UNIVERSITY OF CALIFORNIA Santa Barbara
The acquisition of social status by males in small-scale human societies (with an emphasis on the Tsimane of Bolivia)
A Dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Anthropology
by
Christopher Robert von Rueden
Committee in charge: Professor Michael Gurven, Chair Professor Steven Gaulin Professor John Tooby Professor Leda Cosmides
September 2011
The dissertation of Christopher Robert von Rueden is approved.
_____________________________________________ Michael Gurven
_____________________________________________ Steven Gaulin
_____________________________________________ John Tooby
_____________________________________________ Leda Cosmides
September 2011
The acquisition of social status by males in small-scale human societies (with an emphasis on the Tsimane of Bolivia)
Copyright © 2011 by Christopher Robert von Rueden
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Dedicated to Helena
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ACKNOWLEDGEMENTS I‘d like to thank my advisor and friend Michael Gurven. His intelligence and academic curiosity have been as much an inspiration as his humor, work ethic, and caring way with people in the field. He shared his field site with me, included me in his academic projects, and was always available to discuss intellectual ideas. I owe my burgeoning career as an anthropologist to him. And I look forward to our collaboration in the near future. My wife Helena has provided research advice over the years, and her unwavering love and support have been immeasurable, especially in the last few months of writing this dissertation. My parents fostered my intellectual curiosity and interest in anthropology with many dinner-table discussions and trips to book stores and foreign countries. Hillard Kaplan has been a valuable source of research advice, and Paul Hooper, Dan Cummings, Jon Stieglitz, Helen Elizabeth Davis, and Lisa McAllister assisted in the collection of some of the data in this dissertation. Alberto Maito and Bacilio Tayo not only helped me as translators but their insights shaped the direction of much of my research. I owe a tremendous debt to the people of Tacuaral, Jamanchi, Munday, and Fatima in the Beni, Bolivia for allowing me to live and work amongst them. Finally, I‘d like to gratefully acknowledge financial support for this research from the National Science Foundation (#DDIG-0921429; #BCS-0136274; #BCS-0422690) and National Institutes of Health (#R01AG024119-01).
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VITA OF CHRISTOPHER ROBERT VON RUEDEN September 2011 EDUCATION Bachelor of Arts in Anthropology, Harvard University, Cambridge, May 2001 Doctor of Philosophy in Anthropology, University of California, Santa Barbara, September 2011 PROFESSIONAL EMPLOYMENT 2001: Analyst, World Conservation Union (IUCN), Washington, D.C. 2002: Faculty Member, The Island School, Eleuthera, Bahamas 2003: Analyst, Environment International Ltd., Seattle, Washington 2004-2010: Teaching Assistant, Departments of Anthropology, Law & Society, and Sociology, University of California, Santa Barbara 2010-2011: Teaching Associate, Department of Anthropology, University of California, Santa Barbara PUBLICATIONS von Rueden, C. & M. Gurven (2011). When the strong punish: why the net costs of punishment are often negligible. Behavioral and Brain Sciences. von Rueden, C., M. Gurven, & H. Kaplan (2011). Why do men seek status? Fitness payoffs to dominance and prestige. Proc. R. Soc. B., 278, 2223-2232. Sell, A., G. Bryant, L. Cosmides, J. Tooby, D. Sznycer, C. von Rueden, A. Krauss, & M. Gurven (2010). Adaptations in humans for assessing physical strength from the voice. Proc. R. Soc. B., 277, 3509-3518. Gurven, M., M. Borgerhoff Mulder, S. Bowles, P. Hooper, H. Kaplan, R. Quinlan, R. Sear, E. Schniter, C. von Rueden, A. Bell, & T. Hertz (2010). Domestication alone does not lead to inequality: intergenerational wealth transmission among horticulturalists. Current Anthropology, 51, 49-64. Borgerhoff Mulder, M., S. Bowles, T. Hertz, A. Bell, J. Beise, G. Clark, I. Fazzio, M. Gurven, K. Hill, P. Hooper, W. Irons, H. Kaplan, D. Leonetti, B. Low, F. Marlowe, R. McElreath, S. Naidu, D. Nolin, P. Piraino, R. Quinlan, E. Schniter, R. Sear, M. Shenk, E.A. Smith, C. von Rueden, & P. Wiessner (2009). Intergenerational wealth transmission and the dynamics of inequality in small-scale societies. Science, 326, 682-688.
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Gurven, M., J. Winking, H. Kaplan, C. von Rueden, & L. McAllister (2009). A bioeconomic approach to marriage and the sexual division of labor. Human Nature, 20, 151-183. Sell, A., J. Tooby, L. Cosmides, D. Sznycer, C. von Rueden, & M. Gurven (2009). Human adaptations for the visual assessment of strength and fighting ability from the body and face. Proc. R. Soc. B., 276, 575-584. von Rueden, C., M. Gurven, & H. Kaplan (2008). The multiple dimensions of male social status in an Amazonian society. Evolution and Human Behavior, 29, 402-415. Gurven, M. and C. von Rueden. (2006). Hunting, social status, and biological fitness. Social Biology, 53, 81-99. Walker, R., O. Burger, J. Wagner, & C. von Rueden. (2006). Evolution of brain size and juvenile periods in primates. Journal of Human Evolution, 51, 480-489.
AWARDS Fiona Goodchild Award for Excellence as a Graduate Student Mentor of Undergraduate Research, UCSB, 2010 Dissertation Research Fellowship, UCSB Graduate Division, 2010 Doctoral Dissertation Improvement Grant, National Science Foundation, 2009 Dean‘s Fellowship, UCSB, 2008 Best Student Paper, Evolutionary Anthropology Society , 2008 Rank of Eagle, Boy Scouts of America, 1997
FIELDS OF STUDY Major Field: Cultural Anthropology Major Field: Evolutionary Anthropology
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ABSTRACT
The acquisition of social status by males in small-scale human societies (with an emphasis on the Tsimane of Bolivia)
by Christopher Robert von Rueden
Male status hierarchies are a human universal. In all societies, men with a greater ability to inflict costs (i.e. dominance) or confer benefits (i.e. prestige) gain differential access to contested resources. However, our knowledge of how human societies compare in the determinants and outcomes of status is limited. Ethnographies are typically anecdotal; they explore the link between only one particular trait and social status, or lack a longitudinal design to assess causal relationships. Filling this knowledge gap in fast-disappearing small-scale societies is critical, given their relevance to understanding human evolution and transitions in socio-political complexity over human history. Among the Tsimane horticulturalists of Bolivia, I find that there is a high level of inequality in status acquisition across men, even though they lack formal, authoritative government. The consensus-based decision-making in small-scale societies does not preclude significant inter-individual power differentials beyond those due to age and sex. I compare status acquisition in different domains (dyadic
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fighting ability, getting one‘s way in groups, community-wide influence, and respect from peers), which differ in the extent to which they reflect dominance versus prestige. Physical size best predicts fighting ability while social support from allies, both kin and non-kin, best predicts success in the other status domains. Marketrelated skills are growing contributors to community-wide influence, which is more unequally distributed in more modernized Tsimane villages. Greater access to private, material wealth in these more modernized villages does not undercut the sharing of food and labor across households, which are important means of securing allies and, ultimately, influence. I also evaluate the reproductive outcomes of status acquisition. I find that more influential Tsimane men have more surviving offspring within their marital unions, due to marrying young wives and to the support of allies, but they also experience more extra-marital affairs. The strong relationship between status and fertility (both legitimate and illegitimate) across small-scale societies suggests men do not pursue status solely to improve their access to mates but also to benefit their families. This dissertation is the first multivariate analysis of social status to consider different determinants or outcomes of status simultaneously and is also the first to present longitudinal data on status acquisition in a small-scale society.
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TABLE OF CONTENTS
Chapter 1. Social status: a ubiquitous motivator of human behavior………...............1 A. Why humans care about status………………………………………..……….3 B. Social status defined: relative access to contested resources……............……5 1. Status results from the power to inflict costs or confer benefits..…..…..…6 2. Nonhuman versus human status hierarchies...………………………….…8 3. Status is based on others‘ perceptions……………………………….…..10 C. Status is acquired and manifested differently in men and women…………..12 D. Status hierarchies exist even in small-scale egalitarian societies……………15 E. The special role of small-scale societies in the study of human behavior…...19 F. Motivation and organization of the dissertation…………………………..…22 Chapter 2. Field-site and methods……………………………………...………...…25 A. The Tsimane forager-horticulturalists of Bolivia……………………………25 1. Subsistence and social organization……………………………………...26 2. History and recent ―modernization‖……………………………………..29 3. The four study villages………………………………………………...…31 a. Munday………………………………………………………………34 b. Fatima………………………………………………………………..34 c. Jamanchi……………………………………………………………..35 d. Tacuaral………………………………………………………………36 B. Data collection methods……………………………………………………...37
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1. Photo-ranking…………………………………………………………….40 2. Observational measures………………………………….………………43 3. Demographic, economic, and social network interviews……………..…45 4. Anthropometrics………………………………………………………....47 5. Validation of the photo-ranked measures………………………………..47 Chapter 3. The determinants of status among the Tsimane of Tacuaral...…...…...…50 A. How men acquire status across human societies…………………………….50 1. Embodied capital.......................………………………………………....54 2. Material capital……………..……………………………………………57 3. Relational capital……….………..………………………………………58 4. Status investments over the life-course……………….………………….60 B. Predictions……………………………………………………………………64 C. Data analysis………………………………………………………………....68 D. Results……………………………………………………………………..…74 1. Cross-sectional results…………………………………………………...74 2. Longitudinal results……………………………………………………...83 Chapter 4. The fitness gains of status acquisition in Tacuaral….……………...……90 A. Why measures of lifetime fitness matter.................................………………90 B. Predictions……………………………………………………………………93 C. Data analysis…………………………………………………………………99 D. Results…….………………………………………………………………...102 1. Cross-sectional results………………………………………………….102
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2. Longitudinal results…………………………………………………….118 3. Cross-cultural meta-analysis………………………………..…………..121 Chapter 5. The effects of socio-ecological variation on status hierarchy differences across Tsimane villages……………...……..………..………....130 A. Resource ecology and the evolution of status inequality…………...………130 1. Joint food production and status leveling……...……………….………130 2. The power of salmon, acorns, and sweet potatoes….…………………..133 B. Predictions…………………………………………………………………..136 C. Data analysis………………………………………………………………..143 D. Results…………………………………………………………………...….145 1. Comparing the villages on indices of modernization……..….………...145 2. Comparing the villages on indices of conflict and cooperativeness...….147 3. Villages differ in the determinants of status……………………………152 4. Villages differ in the inequality and inheritance of influence…..………165 5. Villages differ in the reproductive outcomes of influence…..…….……169 Chapter 6. Discussion……………………………………………………….…..…174 A. Summary of results…………………………………………………………174 1. The determinants of status in Tacuaral…………………………………174 2. Status and lifetime fitness in Tacuaral……………………………….…178 3. Status and lifetime fitness cross-culturally……………………………..181 4. The Tsimane villages compared………………………………………..182 B. Interpretation of the results…………..……………………………………..187
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1. The multiple dimensions of male social status……………..…………..187 2. Why do men seek high status?………………………………………….200 3. Natural selection of male status-seeking behavior……………………...211 References…………………………………………………………………………..215 Appendix A: Instructions and questions presented to photo-raters………………...243 Appendix B: Instructions and questions from the economic and social network interviews…………………………………………………..246
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LIST OF FIGURES
Figure 2-1. Map of the four study villages….............................................................33 Figure 3-1. Distinguishing the determinants of status from social power and social status……..…..…………..……………………………..…51 Figure 3-2. Schematic of predicted relationships between the status determinant factors and the social status measures ..............................….…..71 Figure 3-3. Non-parametric LOWESS smoothed curves of each status measure by age, from Tacuaral in 2005……………...………..…….……….82 Figure 3-4. Non-parametric LOWESS smoothed curves of the change in Tacuaral mens‘ social status between 2005 and 2009, by age………….....89 Figure 4-1. The pathways form social power to lifetime fitness…………...……….98 Figure 4-2a. Tacuaral men‘s number of surviving offspring by their community-wide influence…………………………………………………103 Figure 4-2a. Tacuaral men‘s number of surviving offspring (relative to their age) by their community-wide influence…………………104 Figure 4-3a. Tacuaral men‘s number of surviving offspring by dominance quartile…………..……………………………………………...105 Figure 4-3b. Tacuaral men‘s number of surviving offspring by prestige quartile……………..…………………………………...……..…...106 Figure 4-4. Linear relationship between change in Tacuaral men‘s surviving offspring from 2005 to 2009 and their dominance
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(solid line) and prestige (dashed line) from 2005…………………………..119 Figure 5-1a. Sources of conflict in Munday…………………………………..…...149 Figure 5-1b. Sources of conflict in Fatima………………………………………...149 Figure 5-1c. Sources of conflict in Jamanchi……………………………………....150 Figure 5-1d. Sources of conflict in Tacuaral……………………………………....150 Figure 5-2a: Non-parametric LOWESS smoothed curves of each status measure by age, from Munday………………………………………161 Figure 5-2b: Non-parametric LOWESS smoothed curves of each status measure by age, from Fatima……………………………………...…162 Figure 5-2c: Non-parametric LOWESS smoothed curves of each status measure by age, from Jamanchi…………………………………...…163 Figure 5-2d: Non-parametric LOWESS smoothed curves of each status measure by age, from Tacuaral………………………………………164 Figure 6-1: The independent, linear predictors of four measures of adult male social status in Tacuaral from 2005…………………………….176 Figure 6-2: How powerful Tacuaral men produce more intra-marital surviving offspring…………………………………………………………180
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Chapter 1. Social status: a ubiquitous motivator of human behavior
In Leviathan (1651), Thomas Hobbes explains why humans are not hymenoptera. His first argument: ―men are continually in competition for Honour and Dignity, which these creatures are not‖. Without doubt, humans care strongly about relative social position. People tend to be happier when they are richer than their neighbors (Blanchflower & Oswald 2004; Frank 1999; Luttmer 2005) or, in the view of H.L. Mencken (1949), simply richer than their spouse‘s sibling‘s spouse. Individuals will even pursue reputational gains at the expense of absolute gains in wealth (Huberman et al. 2004). Worker satisfaction correlates better with relative rather than absolute income levels (Clark & Oswald 1996; Groot & van den Brink 1999). Robert Frank (1985) has found that people would prefer to live in a small instead of a large house, on the condition that their neighbors live in even smaller houses. Hobbes‘ second argument for why humans are not hymenoptera: among bees and ants, ―the Common good differeth not from the Private‖ (pp. 117). Status concerns in humans often motivate behavior that is individually beneficial but collectively detrimental. Verbal denigration of status rivals can quickly precipitate violence (Daly & Wilson 1988); if coalitions form around the disputants, internecine feuding may result. Avenging an insult to save face is a common motive for declaring war (O‘Neill 1999). Status contests need not be violent to cause collective harm:
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conspicuous consumption (Veblen 1899) creates negative externalities for society at large (Frank 1985). For example, to purchase luxury goods that signal status, individuals may take inefficiently risky jobs that pay more (Heffetz & Frank 2011). Furthermore, as people buy larger McMansions and Hummers to ―keep up with the Joneses‖, they have less to spend on education and health care, let alone invest in savings. Even rural poor facing malnutrition will trade-off productive investments for consumption of designer-label goods (van Kempen 2003) or expensive weddings (Banerjee & Duflo 2007). Such conspicuous consumption among the poor is exacerbated by rising income inequality (Brown et al. 2011). Across nations of the developed world, greater intra-societal status inequality is associated with more crime and poorer average health (Wilkinson & Pickett 2010). But the pursuit of status is not as destructive to society as Hobbes would argue (nor are his characterizations of hymenopteran altruism accurate). While there will always be haves and lesser-haves, status contests do not always lead to zero-sum outcomes or negative externalities. Status contests may reduce transaction costs in ―markets‖ for mates and allies by communicating information (e.g. mate value or fighting ability) to potential partners or competitors (c.f. Noe et al. 1991). When status hierarchies are stable, they reduce the costs of repeated contest competition, as modeled by the war of attrition (Maynard Smith & Price 1973). The pursuit of status can be pro-social. Reputational concerns motivate technological innovation and artistic endeavors (Miller 2001), leadership in the service of group-beneficial collective action (Hooper et al. 2010), and conspicuous generosity (Harbaugh 1998;
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Roberts 1998). People contribute substantially more to public goods when both their identity and the amount they give are made visible to others (Bereckzei et al. 2007; Rege & Telle 2004). Conversely, people are less pro-social in public when their ability to develop an altruistic reputation is diluted by receipt of monetary compensation (Ariely et al. 2009). For better or worse, the pursuit and display of social status underlie much of human psychology and social behavior. However, status-striving is puzzling. The rewards to individuals who acquire status are often intangible and carry high energetic, material, and opportunity costs. The pursuit of status may bring significant risk of injury or death. For some, including the Greek heroes of The Iliad, death is a small price to pay for fame and glory.
A. Why humans care about status Why do people want to be known as stronger, wealthier, and more generous than their peers? The hypothesis entertained in this dissertation is that the ultimate reason is no different from why chimpanzees engage in dominance displays (de Waal 1982), manakin birds queue for alpha status in leks (McDonald 2007), or cichlid fish grow in size when competing over territory (Hofmann et al. 1999). Animals that achieve high status, particularly males, experience greater lifetime reproductive success (Cowlishaw & Dunbar 1991; Ellis 1995). Humans are no exception. A positive relationship between men‘s status and fertility is not restricted to pre-modern chiefdoms, kingdoms, and sultanates (Betzig 1986) but is also evident in small-scale
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societies (Borgerhoff Mulder 1987; Chagnon 1988a; Irons 1979; Kaplan & Hill 1985a). The robustness of the status-fertility relationship across currently-living species suggests that status-conferring traits, including the motivations to achieve and display status, are the product of natural selection. Natural selection is the only process shown capable of creating complex functional design in organisms (Williams 1966), and functional design includes cognitive and motivational systems (Tooby et al. 2008). While a naturally selected trait may not correlate with lifetime fitness everywhere the relationship is tested (Clutton-Brock 1988; Symons 1992), traits that consistently produce higher average fertility than alternatives were probably produced by natural selection (Grafen 2000; Reeve & Sherman 1993). Furthermore, studies of the status-fertility relationship shed light on how current selection pressures may be shaping status-seeking adaptations. In modern industrial human societies, the relationship between status and fertility has been attenuated by modern contraception and socially imposed monogamy (Perusse 1993) and the increased importance of education to wealth acquisition (Kaplan 1996). Nevertheless, high status men in these societies often produce more offspring (Fieder & Huber 2007; Hopcroft 2006; Nettle & Pollett 2008; Weeden et al. 2006). Proximate motivations are not the same as ultimate explanations (Tinbergen 1963). On a conscious level, humans do not necessarily pursue status to increase their reproductive success. Rather, they seek access to contested resources within their social group, especially the acquiescence or aid of other individuals. Social status is
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often defined in terms of such proximate outcomes or, alternatively, the traits that enable individuals to obtain them.
B. Social status defined: relative access to contested resources In anthropology, social status has been defined to broadly include both egocentric statuses, such as kinship terms, as well as socio-centric statuses that do not change from dyad to dyad. For example, ―father‖ is an egocentric status while a Roman Catholic ―Father‖ is a socio-centric status (Service 1962). Across the social sciences, social status in the socio-centric sense is often equated with relative access to contested resources (Chagnon 1979; Davis & Moore 1945; Ellis 1993; Henrich & Gil-White 2001; Lipset 1976; van den Berghe 1978). For example, Weber (1922) defines social status as an effective claim to esteem in terms of negative or positive privileges. High status is tantamount to privileged access to goods and services within a social group, including material wealth (e.g. food, land, technology), knowledge, and the deference or favor of peers, authorities, and potential sexual partners. Furthermore, social status has meaning only when the allotment of such privileges is somewhat stable. If individuals have to fight over contested resources with every social encounter, there is no status hierarchy, only moment-to-moment winners and losers (Henrich & Gil-White 2001). Stable status hierarchies are characterized along two axes: (1) the degree of transitivity among dyadic status relationships and (2) the slope of the relationship between relative position and resource access (van Schaik
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1989; de Vries et al. 2005). In other words, status hierarchies differ in terms of linearity and steepness.
1. Status results from the power to inflict costs or confer benefits Status hierarchies are the result of reciprocal power relationships (Blau 1977; Grammer 1996; Harsanyi 1966; Lewis 2002). A priority of resource access is granted to high-status individuals due to a group-wide perception that these individuals have relatively greater social power, whether actual (currently exercised power) or latent (its potential exercise alone may influence others). Social power is the relative ability to impose costs or confer benefits on others to intentionally alter their behavior (Hamilton 1976; Russell 1938). In the behavioral sciences, the ability to inflict costs is typically labeled dominance while the ability to confer benefits has been called prestige (e.g. Henrich & Gil-White 2001). Two issues with respect to social power must be considered: intention and opposition. Without limiting social power to the product of individual intentions, the concept of power becomes too broad and of little analytical use (Wrong 1968). Any effect of social interaction would become an act of power. An individual need not perform an action for every instance of intentional power, however. Anticipating reactions on the part of a more powerful individual, such as the avoidance of punishment, may still be considered effects of social power (Nagel 1968). Many definitions of social power require opposition between the powerful and the less powerful individuals. Consider Weber: ―power is the probability of a man or
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a number of men to realize their own will in a communal action despite the resistance of others‖ (1947: pp. 152). Lack of opposition does not mean lack of power, however. Social power is certainly an ability to get someone to do something they otherwise would not have done (Bachrach & Baratz 1962; Harsanyi 1962; Dahl 1957) but this does not necessitate coercion. A leader‘s coordination of a collective action, where all individuals are in pursuit of the same goal, constitutes an act of social power (Dowding 2003). Social power is much broader than the infliction of costs upon others. In most cases, an act of social power will both inflict costs and confer benefits. Furthermore, dominance and prestige are not homologues, as some have argued (e.g. Barkow 1989), but can provoke rather different ethological displays among followers. Signals of deference that target individuals better able to furnish benefits, e.g. prolonged stares, are distinct from deference signals towards those better able to inflict costs, e.g. gaze aversion (Henrich & Gil-White, 2001). French & Raven (1959) identified six forms of power: reward and coercion simply induce behavioral changes in the target of power while legitimate power, referent power, expert power, and informational power concern changes in intrinsic motivation.
Dominance and prestige are not analogous to French & Raven‘s
―reward‖ and ―coercion‖ but incorporate all of French & Raven‘s forms of power. Persuading people to adopt new goals or beliefs or imparting to them new skills and knowledge is consistent with a cost-benefit framework. The adoption of new beliefs will have positive and/or negative effects, depending on the particular actions these new beliefs motivate.
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2. Nonhuman versus human status hierarchies Among nonhumans, status hierarchies result primarily from individuals‘ relative ability to inflict costs on each other. For example, physically dominant chimpanzees usurp or maintain priority access to food and mates by signaling their strength and willingness to aggress (Boesch et al. 2006; Cowlishaw & Dunbar 1991; de Waal 1982). Social alliances can be important among nonhuman primates, but they are largely to support the above uses of dominance (de Waal 1982; Nishida & Hosaka 1996). Furthermore, coalitions are neither as large nor as stable as in humans, who are able to reduce coordination costs by the use of language (Dunbar 1996). Individuals whose power to inflict costs is the result of the strength of their coalition are said to possess ―derived dominance‖ (Hand 1986). Combined, individual and derived dominance constitute what Maynard Smith & Parker (1976) term ―resource-holding potential.‖ Whether in humans or non-humans, group members defer to more dominant individuals because in so doing they believe they will avoid harm and gain some (indirect) benefit. Even in the case of purely despotic status hierarchies, subordinates may prefer the company of a despot to their options outside of the group (Vehrencamp 1983). Wild baboons accept despotic decisions by the alpha male, such as following him to patchy resources that he will differentially exploit, because they are less likely to suffer predation compared to foraging alone (King et al. 2008). Status hierarchies represent agreements, maintained by deference signals, to facilitate
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exchange or to avoid costs, including the costs of repeated contest competition as modeled by the war of attrition (Maynard Smith & Price 1973). Social power among nonhumans is not limited to resource-holding potential. Individuals may exercise social power from possession of an inalienable commodity valuable to other group members (Hand 1986; Lewis 2002). Male chimpanzees cannot be coerced into providing coalitional support to the alpha male, but their willing membership in the alpha‘s coalition begets them greater mating opportunity (Duffy et al. 2007). Social power based on inalienable commodities is subject to the effects of supply and demand (Noe et al. 1991). For example, dominant chimps will build dyadic or triadic mate-guarding coalitions when the percentage of copulations they can monopolize drops to 50% or 30%, respectively (Watts 1998). Paradoxically, multi-male alliances are least common where contest competition is a larger contributor to mating success (van Noordwijk & van Schaik 2004). Seasonally breeding females are difficult to monopolize by a single alpha male compared to females who do not synchronize their estrus periods. In the latter case, alpha males have less need of coalitional support to outcompete rivals for estrus females. Among humans, priority access to resources is only sometimes obtained through dominance and is frequently mediated by voluntary transfers of inalienable goods and services. This greater scope for prestige-based hierarchies is the result of commodities made available by extensive sharing of food, information, labor, and other resources (Kaplan & Gurven 2005) and by cumulative cultural evolution (Tomasello 1999). Henrich and Gil-White (2001) describe prestige as the deference
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that accrues to individuals who possess or transmit publicly esteemed skills. However, Henrich & Gil-White‘s discussion of prestige is narrower than the potential range of nonagonistic social status. For example, individuals may attract mates by offering ―good genes‖ or material goods in exchange for sexual access, or they may gain political influence by offering physical strength or coordinative leadership to potential allies. Rarely will human status hierarchies depend entirely on either dominance or prestige. For example, Stephen Hawking‘s work in astrophysics grants him prestige, which in turn provides him the institutional power to inflict costs on others, such as graduate students (Henrich & Gil-White 2001). According to Machiavelli, the most powerful individuals are both feared and loved (1532). This view of hierarchy takes a middle road between the positions of Fried (1967), who describes hierarchies as inherently repressive, and Service (1962), who sees hierarchies as collectively beneficial solutions to management of group interests.
3. Status is based on others’ perceptions Status hierarchies are less determined by the actual distribution of social power within a community than by people‘s perceptions of its distribution. Through dyadic or polyadic interaction, 3rd party observation, or word-of mouth and the media, individuals classify their conspecifics according to their perceived social power. Generally, there is consensus concerning who is more or less powerful. According to Marshall (1977):
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―Social status…rests on collective judgment, or rather a consensus of opinion within a group. No one person can by himself confer status on another, and if a man‘s social position were assessed differently by everybody he met, he would have no social status at all‖ (pp. 198).
When perceptions of social power shift, group members consciously or nonconsciously re-order status hierarchies (Fisek et al. 1991; Markovsky et al. 1984; Rashotte & Webster 2005). Emerson (1962) argues that individuals lose social power when group members become less dependent on them for resource access. Blau (1964) makes a similar point in the context of leadership: power is lost when subordinates can fully reciprocate the services of their leader, seek alternative sources of leadership, or no longer require the services of a leader. However, subordinates need not depend on the resources of the powerful to be vulnerable to their ability to help or harm. The distribution of social power in a community can change rapidly with shifts in group members‘ coalitional affiliations. Coalitions enable subordinates to overthrow higher-status individuals or limit their power (Pandit & van Schaik 2003; Summers 2005; de Waal 1982). In many traditional human societies, exploitive leaders are often ridiculed and, more rarely, ostracized or killed (Boehm 1999). In order to placate disgruntled subordinates and to regain lost social support, high-status individuals may employ such strategies as self-deprecation, wealth redistribution, or an increased commitment to social norms.
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Attempts to influence judgments of relative social power may take the form of conspicuous consumption (Bourdieu 1984; Miller 2009; Nelissen & Meijers 2011; Saad 2007; Veblen 1899) or public displays of skill and generosity (Barclay & Willer 2007; Bereczkei et al. 2007; Griskevicius et al. 2007; Harbaugh 1998; Milinski et al. 2002; Roberts 1998; van Vugt & Hardy 2010). Conspicuous generosity is not only employed as a signal of relative control over resources (Pawlowski & Dunbar 1999) but also as a signal of cooperative intent (Frank 1988; Gintis et al. 2001) or phenotypic quality (Bliege Bird & Smith 2005). The more difficult the specific act of consumption or production, the stronger the signal to potential competitors, allies, or mates of an individual‘s ability to inflict costs or confer benefits. While many instances of wealth and skill demonstration have been attributed to costly signaling as described by Zahavi & Zahavi (1997), status competition is a costly signal in the Zahavian sense only when social status is advertised but not gained (Boone 1998).
C. Status is acquired and manifested differently in men and women Sexual selection theory suggests that men and women will differ in how they pursue and display social status. Males have a higher maximum reproductive rate, due to sex differences in parental investment (Bateman 1948; Trivers 1972). Except for purely monogamous mating systems, male reproductive success is more limited by access to mates and will tend to exhibit greater variance compared to female reproductive success (Clutton-Brock 1988). As a result, males more frequently compete over mates. Across primates, the relationship between dominance and
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reproductive success is weaker and less consistent for females than for males (de Waal 1982; Ellis 1995; Silk 1987; Wrangham 1980). Among humans, men are on average more likely to engage in competitive interactions (Croson & Gneezy 2009), including physical combat (Archer 2009; Chagnon 1983; Daly & Wilson 1988; Ellis et al. 2008). Competition over women is the leading cause of homicide among huntergatherers (Knauft 1991; Lee 1984). A significant sex difference in intra-sexual physical aggression has likely existed throughout human evolution, as indicated by the observation that the upper body strength of the average man is greater than 99.9% of women (Lassek & Gaulin 2009). Men are also more likely to build coalitions in the service of competition for mates (Smuts 1995). Historically, inter-group coalitional warfare is purely a male affair (Adams 1983; Wrangham & Peterson 1996), and its primary functions in pre-industrial societies were the capture of women (Keeley 1996) and pursuit of social power via warriorship (Chagnon 1988a). Sex differences in dominance motivations and coalition-building are present throughout ontogeny: from the preschool years, boys are more prone to rough-andtumble play (Maccoby 1990), and are more likely to prefer group-level activities over dyadic activities (Benenson 1993; Lever 1978). Adolescent boys are more likely to form large and stable groups, which are characterized by clearly delineated dominance hierarchies (Savin-Williams 1980). Boys revere each others‘ competitiveness while girls who compete too vigorously against their peers are likely to be ostracized (Hughes 1988). Public recognition of toughness is less important to girls because dominant, aggressive females are not especially preferred as mates
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(Campbell 1999). Traits conducive to dominance in men, including muscularity and deep voices, have utility not only in contest competition and coalition formation but also in signaling resource access and phenotypic quality to women (Gangestad & Thornhill 2008). Men may be more likely to seek prestige, via conspicuous consumption (Griskevicius et al. 2007) or public displays of production skill (Hawkes et al. 2001). In contrast, women‘s contribution to production has relatively low bearing on their social status across human societies (Low 1992). In traditional societies, highproducing women are valued as mates, but not to the same degree that production skill improves men‘s mate value (Gurven et al. 2009). Given women‘s greater preference for mate cues signaling resource access (Buss 1989) and the importance of male investment to human reproduction (Kaplan et al. 2000), men have greater incentive to broadcast their ability to procure resources. However, if males exercised considerable control over female mating decisions in ancestral human environments, then male-specific physiology and psychology may have been shaped more by intrasexual selection than female choice (Puts 2010). The foregoing arguments are not meant to suggest women have little concern for social status. In her analysis of the Standard Cross-Cultural Sample, Low (1992) found that women often have a voice in community affairs, but formal political influence is rare. In Conambo, Ecuador, women garner social power by brokering factional disputes, and men‘s status benefit from their wives‘ roles as mediators (Bowser & Patton 2009). In most societies, the statuses of a husband and wife will be
14
intertwined, in part due to shared kin support. In those few societies where women hold public office, they evidence no clear reproductive gain (Low 1992). However, their political influence may benefit their son‘s reproductive success more than their own (Low 1992). The degree of paternal investment in a society will also pattern women‘s status-striving (Cashdan 1995). Women compete more heavily for investing mates where there is high paternal investment and directly for material resources where paternal investment is low. When women compete, they are more likely to employ indirect aggression such as gossip (Hess & Hagen 2006). Because the ability to provide maternal care is more important to female fitness than the ability to provide paternal care is to male fitness, women are less likely to engage in risky status displays or injury-causing physical aggression (Campbell 1999). Men‘s greater tolerance of risk when competing for status is partly why socio-economic position has a stronger influence on male than on female mortality rates (Bopp & Minder 2003; Kruger & Nesse 2006; Martikainen et al. 2001).
D. Status hierarchies exist even in small-scale egalitarian societies According to Lewis Henry Morgan (1877), inequality emerges from the acquisition of property. Absent significant material wealth, small-scale human societies are non-hierarchical to the point that even spouses are communally shared, Morgan claimed. Morgan influenced Engels, who argued that simple human societies exhibit ―primitive communism‖ where ―all are equal and free- the women included‖ (1884, pp. 86). In the mid-twentieth century, political anthropologists rectified these
15
mischaracterizations. Sahlins (1958) recognized that societies free of exploitation do not exist, and Fried (1967) argued that age and gender structure access to resources in all human societies. However, Fried believed that in small-scale societies lacking formalized hierarchy, ―there are as many positions of prestige in any given age-sex grade as there are persons capable of filling them‖ (pp. 33). In these so-called egalitarian societies, which are primarily foragers and horticulturalists, men may be able to coerce women and children, but adult male status is neither differentially ascribed nor achieved through competition (Boehm 1999; Knauft 1987). Differences in strength, skill, or knowledge do not typically cause certain individuals in these societies to gain greater favor or deference from group members (Knauft 1987). Egalitarian societies are characterized by ―reverse dominance hierarchies‖ where group members collectively use ridicule or social exclusion to limit aggrandizing behavior (Boehm 1999). For example, !Kung and Hadza hunters who brag are put down (Lee 1969; Hawkes 1992). Leveling coalitions are sometimes observed in nonhuman primates (Pandit & van Schaik 2003), but in comparison with human foragers they are generally risky, of small size, less effective, and short-lived (Boehm 1999). It is not that members of egalitarian societies lack status-seeking motivations, but rather that these are thwarted by communally enforced norms compelling humility. Additionally, communities within egalitarian societies are generally small, exhibit fluid membership, and lack fraternal interest groups organized by patrilineal descent or patrilocal residence (Knauft 1991), so male coalition-building in the service of dominance becomes difficult. Since the major input into production in
16
forager societies is voluntary skilled labor rather than defensible material resources or land, the opportunities for coercion are limited (Kaplan et al. 2009). Fried (1967), Knauft (1987, 1991), and Boehm (1999) may be underrepresenting the extent of status differences in small-scale egalitarian societies, however. Despite widespread resource sharing (Kaplan & Gurven 2005; Winterhalder 1986), a relative lack of defensible resources (Kaplan et al. 2009), and status-leveling norms (Boehm 1999; Cashdan 1980), certain individuals in forager societies consume more resources, get the better pick of mates, and take more central roles in decisionmaking (Kaplan & Hill 1985a; Service 1975; Wiessner 2002a). Furthermore, statusleveling is better characterized as ―counterdominant‖ behavior than as an actual reversal of hierarchy; the rights and opportunities of high status individuals are attenuated but not reversed (Erdal & Whiten 1994). While gains to dominance may be limited in egalitarian societies, knowledgeable and skilled individuals are able to acquire status via prestige, particularly if they are generous and humble (Bird & Bliege Bird 2010). Service (1975) and Meggitt (1977) describes the self-effacing, ―first among equals‖ role of leaders in small-scale societies, who lack coercive authority but have differential influence over their peer‘s opinions and the group consensus-seeking process. Of the !Kung, Shostak (1981) writes:
―With no formal leaders or hierarchies, and no political or legal institutions to convey authority, decisions are made on the basis of group consensus. Each group has individuals whose opinions carry more weight than those of
17
others—because of age, of having ancestors who have lived in the area longer, or of personal attributes such as intelligence, knowledge, or charisma. These people tend to be more prominent in group discussions, to make their opinions known and their suggestions clear, and to articulate the consensus once it is determined. Despite their lack of formal authority, they function very much as group leaders‖ (pp. 245).
With their influence, informal leaders can occasionally steer outcomes of group debates to favor themselves, their allies, or their kin. Betzig (1986) provides examples from small-scale societies where members of powerful coalitions differentially benefit from arbitration of conflicts (e.g. Copper Eskimo: Jenness 1922; Twana: Elmendorf 1960). In all human societies, inter-individual differences in dominance and prestige produce differential access to contested resources, egalitarianism notwithstanding. Egalitarian and hierarchical arrangements coexist in all human societies, even though societies fluctuate towards one more than the other (Wiessner 2009). Paradoxically, egalitarian relationships may require hierarchy in order to emerge at all. In a recent analytical model of political dynamics within groups (Gavrilets et al. 2008), egalitarianism emerged only in the context of intense competition between individuals over relative social position; within-group conflicts promoted the buildup of a group-wide alliance which it was in every actor‘s best interests to join.
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E. The special role of small-scale societies in the study of human social behavior Since humans have lived as hunter-gatherers for over 90% of their existence (Smith et al. 2010), studies of modern forager communities can (1) provide inferences about behavior characterizing ancestral human societies and (2) help elucidate the selective forces responsible for behavior in all human societies. Many aspects of human physiology, behavior, and psychology have likely remained in long-term stasis due to stabilizing selection (Tooby & Cosmides 1990), so measures of fitness in modern populations, particularly hunter-gatherers, will have relevance to our understanding of human evolution. For example, comparison of men‘s lifetime fitness to their generosity is revealing of the strength and direction of past selection on male generosity and the evolved preferences of mates and allies for generous men. However, there are problems in using data from modern hunter-gatherers to extrapolate about conditions in the Pleistocene. Modern foragers may occupy relatively marginal habitat compared to ancestral foragers, and modern foragers have been influenced to varying degrees by association with more powerful agricultural societies (Foley 1988; Wilmsen 1989). Modern hunter-gatherers described in the ethnographic record all possess complex technology compared to pre-modern hominins; as a result, extant foragers are probably more efficient in extracting resources compared to Pleistocene societies (Marlowe 2005). Furthermore, foraging societies in the ethnographic record are quite diverse ecologically, demographically, and politically (Kelly 1995).
19
Modern foragers are instrumental in understanding human evolution not because they are analogues of any original human society but because they reveal how human behavioral adaptations operate in the absence of large, dense populations and significant material wealth. Despite their diversity, modern foragers lack domesticated plants and animals, large food surpluses, and systems for storing food over long periods of time; they typically live in small groups of closely related individuals characterized by high residential mobility and fission-fusion dynamics (Kelly 1995; Marlowe 2005). While the archaeological evidence is scant, Pleistocene foragers probably share with modern foragers a sexual division of labor, central-place provisioning, some degree of polygyny, multi-local post-marital residence and bilateral descent, informal political institutions, and generally egalitarian inter-family relationships (Marlowe 2005). A minority of foragers in the ethnographic record, principally those from the Pacific Northwest, were sedentary, engaged in warfare, and possessed social class distinctions (Ames 2003). A large contribution to the diet of predictable fishing returns likely accounts for the complexity of these societies (Marlowe 2005), though aborigines in the Australian desert were also known to practice warfare and are gerontocratic with high levels of polygyny (Hiatt 1996). Rather than impeding our ability to reconstruct the past, variation in the socioecology of modern foragers can be instrumental in inferring ancestral selection pressures. Forager societies were likely as diverse ancestrally as they are in the ethnographic record (Kelly 1995; Rowley-Conwy 2001). The study of behavioral variation across modern small-scale societies enables tests for facultative adaptations,
20
which is the focus of human evolutionary ecology. Examples of this work include studies of how paternal care responds to a group‘s operational sex ratio (Blurton Jones et al. 2000) or how foraging strategies respond to change in resource abundance and caloric density (Hill et al. 1987; Smith 1991). The political ecology of horticultural societies is not far removed from the egalitarianism of most foraging societies. Most horticulturalists are best described as forager-horticulturalists because they tend to supplement their small-scale agricultural production with hunting and gathering. Horticulture first emerged ~10,000 years ago in the Middle East with the domestication of plants and animals (Bellwood 2005). Unlike agriculture, horticulture is characterized by low intensity production of domesticated plant foods based on human labor and simple tools. Production is aimed at household provisioning rather than surplus for cash-cropping or export. Compared to forager societies, leadership is usually more pronounced, status-leveling less evident, groups larger and more sedentary, and households are more self-sufficient (Gurven et al. 2010). On the other hand, levels of material wealth and wealth inequality among horticulturalists are no higher on average than among foragers (Gurven et al. 2010). Horticulturalists typically lack formal hierarchy; as in forager societies, men with greater social power are in demand as a mate or ally and wield informal influence over political affairs (Chagnon 1988a; Patton 2005; Werner 1981). However, status differentiation is more pronounced among island horticulturalists of Oceania, which range from the ―big man‖ societies of highland Papua New Guinea (Wiessner 2002b) to the chiefdoms of the Trobriand Islands (Weiner 1988). In these
21
societies, access to land is more of a limiting factor to production, promoting property rights and conflict over those rights within and between groups (Kaplan et al. 2009). The social power of ―big men‖ resulted from a need for military and diplomatic leadership in the face of these conflicts. Forager and horticultural political systems vary, but the modal pattern of their social organization is much more egalitarian and devoid of material wealth inequality compared to pastoralists and agriculturalists (Borgerhoff Mulder et al. 2009). The egalitarian norms in forager and horticultural small-scale societies attenuate but do not preclude differential access to resources across adults. Given their likely similarity to the political organization of Pleistocene small-scale societies, modern forager and horticultural societies offer unique insight into the evolution of human status-seeking. Ethnographies of these societies enable better understanding of how individuals build social power, from the savannah to Wall Street, and why they do so.
F. Motivation and organization of the dissertation We have limited knowledge of how human societies compare in the determinants and outcomes of status because existing ethnographies are typically anecdotal, explore the link between only one particular trait and social status, or lack a longitudinal design to properly assess causal relationships. Without quantitative, multivariate ethnography, it is difficult to disentangle direct and indirect effects, and cross-cultural comparison becomes highly interpretive. Filling this knowledge gap in fast-disappearing small-scale societies is critical, given their relevance to the study of
22
human evolution. These societies also provide a unique opportunity to investigate how socio-economic changes within a society shape the determinants and outcomes of status. Better understanding of human social motivation in the context of rapid modernization is important as traditional societies everywhere are increasingly exposed to the forces of globalization. The empirical aims of this dissertation are threefold: to (1) compare the determinants of adult male social status in a small-scale, egalitarian society; (2) determine how status acquisition in this society affects men‘s lifetime reproductive success; and (3) assess how community size and access to material capital shape the determinants, distribution, transmission, and reproductive outcomes of status. Accomplishment of these aims involves several methodological innovations. First, quantitative analyses are presented that consider different determinants and outcomes of status simultaneously. Second, several measures of social status are compared. These measures differ in the extent to which they reflect dominance versus prestige, and they assay relative resource access at different social scales, from the dyad to the community. Third, longitudinal data is evaluated to assess how changes in status determinants affect changes in the measures of status and reproductive success. Fourth, analyses extend across several communities within the same society, which differ in population size and exposure to modern education and markets. Fieldwork for this dissertation was conducted among the Tsimane foragerhorticulturalists of the Bolivian lowlands. The methodological focus is on adult men, which complements work by colleagues on the less overt status competition of
23
Tsimane women (Rucas et al. 2006). Chapter 2 describes the Tsimane, the four villages where data were collected, and data collection methods. Chapter 3 compares the determinants of status across human societies based on existing studies, and develops and tests predictions of the determinants of status in the Tsimane village of Tacuaral. Chapter 4 develops and tests predictions of how social status generates reproductive success in Tacuaral and compares these results with studies of the statusfitness relationship in other small-scale societies. Chapter 5 explains intra-societal increases in stratification over human history and compares Tacuaral with the determinants and outcomes of status in three other Tsimane villages. The four villages differ in size and level of modernization. Chapter 6 discusses the implications of the Tsimane results, for the multi-dimensionality of social status and for natural selection of status-seeking among human males.. Analysis of Tsimane data in Chapters 3 and 4 is restricted to Tacuaral so that the Tacuaral results serve as a benchmark for the village comparisons in Chapter 5. Furthermore, only in Tacuaral is both cross-sectional and longitudinal data available.
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Chapter 2. Field Site and Methods
A. The Tsimane forager-horticulturalists of Bolivia The Tsimane live in central lowland Bolivia, located along the Maniqui, Quiquibey, Apere and Matos Rivers and in adjacent forests of the Beni Department. These rivers are all tributaries of the Amazon via the Beni River. The climate in the region is typically hot and humid year-round, with maximum temperatures around 35° Celsius in the summer. Rainfall is frequent, particularly during the summer rainy season from December through March. Annual rainfall totals are approximately 1800 mm., classifying the forests in the area as tropical rainforest. Since Tsimane territory abuts the foothills of the Andes, ―surazos‖ from the mountains (as far away as Patagonia) can cause temperatures to sporadically drop to as low as 15° Celsius in the winter. The Tsimane language is an isolate, together with Mosetene, and is unrelated to the dominant indigenous languages of Bolivia (Aymara and Quechua in the highlands and the Arawakan and Tupi-Guarani languages in the lowlands). However, mitochondrial DNA suggests the Tsimane and Mosetene are more closely related to the Aymara and Quechua than to other lowland indigenous groups in Bolivia, such as the Yuracare (Corella et al. 2007). This may be due to frequent population admixture between the Tsimane and highland peoples throughout their histories. The genetic
25
diversity among the Tsimane and Mosetene are higher than that observed in other indigenous American groups living in much larger areas (Corella et al. 2007).
1. Subsistence and social organization In all Tsimane villages, subsistence is based on the cultivation of plantains, rice, corn, and sweet manioc in small swiddens, and hunting and fishing for meat. These foods together provide over 90% of the calories in the diet (~65% from horticulture and ~25% from foraging), with the remainder coming mainly from trade with itinerant merchants. Tsimane live in extended family clusters, within which food and labor sharing is extensive. While Tsimane families may spend weeks or months on hunting or fishing trips, or cultivate fields some distance from their primary house in settled villages, the Tsimane are semi-sedentary and live in communities ranging from 30 to 500 individuals. The Tsimane population is roughly 10,000 and dispersed among approximately 90 villages, which were given formal geographic boundaries only in the late twentieth century. Although productive activities are generally confined within extended families, community members will regularly visit each other (sobaqui) to drink chicha (shoc‟dye), an alcoholic beverage typically made from manioc. In Tsimane culture, maintaining friendly relations (jäm‟yity muntyi), being easy-going (chuchuijtyi), and avoiding direct confrontation and expression of anger (chij facoij) are viewed as proper ways of behaving. Someone who speaks freely (chij peyaquity) but not too much or in a gossiping way (chij peyacsity) is a valued social
26
partner, and jokesters are also recognized and viewed positively (chij shevinyity). Happy, cheerful individuals (majoijbäyis) are contrasted with serious, quiet individuals (futy‟dyety) or those who are easily annoyed (achiyity). Other negative traits commonly described refer to those who react rapidly, usually in a bad way (che‟chei‟si), those who brag (va‟bunyis), and those who are lazy (shoyijyi‟tyi or jamyedyedyetyi). Laziness is often contrasted with demonstration of strong work effort (setyi or chij carijtaqui) and generosity in helping others (chij notacsity). The Tsimane lack any recent history of inter-village warfare, but dyadic conflicts between adult males are not uncommon, usually resulting from sexual jealousy, theft, or disputes over horticultural land. Dispute resolution is typically left to the parties directly involved or, on rarer occasions, adjudicated by an informal gathering of adult men. Many conflicts never get resolved and sometimes provoke emigration to other villages by one of the disputing parties. The most serious conflicts among the Tsimane, such as those involving physical violence, are sometimes discussed in community-wide meetings, where influential individuals will try to generate consensus concerning the relative guilt of the parties in conflict. The community may decide to inflict punishment, usually verbal censure, community service (e.g. clearing village trails), or public whippings on rare occasions. However, no individual or group within a community maintains formal, coercive authority over others. Marriages are stable among the Tsimane, with less than 20% of marriages ending in divorce (Gurven et al. 2009). Divorce is most common in the first year of
27
marriage. Tsimane do not commemorate marriages with formal ceremonies but consider a pair to be married when they sleep together in the same house. Crosscousins are preferred marriage partners, but distant relatives are often selected. Men often leave their natal villages to seek mates during social visits, foraging excursions, and village festivals. Parents or other relatives may also aid in marrying their sons or daughters. Suitors usually ask a woman‘s parents for permission to marry, although abductions and forced marriages are not uncommon (Gurven et al. 2009). There is no formal gift exchange at marriage, although informal bride service is common. Extended family clusters form from post-marital residence patterns, which tend to be matrilocal until the first child or two is born, followed by patrilocal residence. However, there is much flexibility in this pattern. Polygyny is widely accepted except in the two villages with an active missionary presence. Across all Tsimane villages, only 3-5% of men are polygynously married, almost always to two sisters. In more remote communities, the rate of polygyny is as high as 10% (Winking et al. 2009). The Tsimane rarely use contraceptives and total fertility rate is very high (~9 births per woman). Approximately 20% of offspring never reach age 5, principally due to respiratory and gastro-intestinal infections (Gurven et al. 2007). The rate of infanticide is low, accounting for no more than 5% of infant deaths. Prior to 1990, life expectancy at birth was 44 years, and life expectancy upon reaching age 15 was 58 years (Gurven et al. 2007). Infectious disease accounts for the majority of adult deaths, but accidents and occasional homicides comprise nearly 25% of deaths in
28
young adults (Gurven et al. 2007). Despite high infant mortality, the population growth rate is high (3% per year).
2. History and recent “modernization” For much of Tsimane history, shamans (cocojsi) wielded tremendous influence as a result of their ability to commune with forest spirits and ancestors and treat illness due to sorcery. Their influence remained intact even after the arrival of the Jesuits, who founded the mission of San Borja in Tsimane territory in 1693. In large part, the Tsimane avoided settlement and contact with the Jesuits by moving deeper into the forests (Huanca 2006). A second attempt to missionize the Tsimane in the mid-nineteenth century also failed. An exploitative priest was killed by Tsimane in San Pablo, which precipitated a brief war between the Tsimane and the Mosetene. To this day, the Mosetene view the Tsimane as inferior and less ―civilized‖. San Borja had become a center of commerce in the region during the nineteenth century, but only became a significant economic, social, and religious influence on Tsimane society in the early 20th century (Huanca 2006). The rubber boom brought an influx of colonists to the town, who bought rubber and other forest products from the Tsimane. In 1936, an airstrip was built in San Borja which facilitated the sale of cattle meat to the highlands. Tsimane began working as ranch hands in exchange for commercial goods such as metal tools and clothes (Huanca 2006). Many Tsimane became trapped in a system of debt peonage, which persists today.
29
In the 1950s, Catholic (Redemptorist) and evangelical Protestant (New Tribes Mission) missionaries succeeded in converting many Tsimane, partly because they developed schools and health care facilities in addition to their evangelism. New Tribes Mission brought radios to the Tsimane, and their radio station at Horeb, near San Borja, still broadcasts daily sermons and religious music in the Tsimane language. In 1976, the Bolivian government finished a road connecting La Paz with the Beni Department. Colonization by highlanders was encouraged and led to increases in logging, farming, and cattle ranching in Tsimane territory. The Bolivian indigenous movement in the 1990‘s granted the Tsimane legal protection to much of their land, and the Great Tsimane Council was organized in 1989 to represent the Tsimane to outside political interests. Unfortunately, the Council has been largely ineffective in stemming mistreatment of the Tsimane and exploitation of their natural resources by colonists. In Tsimane villages, especially those located near San Borja (current population is ~25,000), incipient cattle ownership, wage labor with loggers and farmers, and produce sales to local markets are on the rise. Incipient patron-client systems have emerged in certain villages where wealthier Tsimane men will occasionally pay other Tsimane to labor in their fields. Although many Tsimane now have access to basic healthcare through the services of NGOs and a hospital in San Borja, mortality rates remain high, particularly among infants. Life expectancy at birth increased by 10 years during the 1990s, due more to decreases in old-age mortality than child mortality (Gurven et al. 2007). Many villages have schools for
30
their children, who are taught largely by bilingual Tsimane teachers trained by New Tribes Mission. Several secondary schools now exist in larger villages, and for the first time some Tsimane are becoming high school graduates. However, the overall adult literacy rate remains low, at roughly 25%. Fluency in the Tsimane language is universal and about half of adults are moderately fluent in Spanish. Due partly to missionary influence, the cocojsi have all but disappeared. Village residents now elect chiefs (corregidores) to organize community meetings and to represent their interests to outside political bodies, including the Great Tsimane Council. However, corregidores lack any substantial authority, tend to have short tenure, and often are unable to effectively organize people for collective action, such as trail-clearing or well-digging (Gurven & Winking 2008). The extended family, not the community, remains the central unit of social organization.
3. The four study villages Research was conducted in four Tsimane villages. The villages differ in population size and proximity to San Borja, providing a 2x2 design for testing the effects of village size and access to material capital on the determinants and outcomes of status (aim 3). In general, the closer to San Borja, the more modernized the community: distance to San Borja is positively related to average cash income, literacy, and Spanish fluency within each village (Gurven 2004). Despite their variance in proximity to San Borja, all four study villages have primary schools. The four villages are as follows: Munday is a small, riverside village located 3 days by
31
motorized canoe up the Maniqui River from San Borja; Fatima is a large, riverside village further upriver from Munday (and from San Borja) and the site of a Catholic mission; Jamanchi is a small, forest village within 3 hours drive of San Borja by logging road; Tacuaral is a large, forest village in even closer proximity to San Borja. Table 2-1 highlights the general characteristics of the villages when data were collected. Tacuaral is listed twice because data were collected in both 2005 and 2009. The map (Figure 2-1) shows the relative locations of the four villages. The dark rectangle in the map inset delineates the map borders relative to the rest of Bolivia.
Table 2-1: Size, density, and distance to San Borja of the four study villages Population
Settlement Density (n per km.² of residential area)
Distance to San Borja (km.)
Travel Distance to San Borja (km.)
Munday
87
133
63
101
Fatima
610
38
66
114
Jamanchi
124
231
33
47
Tacuaral (2005)
372
187
29
32
Tacuaral (2009)
458
74
29
32
32
Figure 2-1: Map of the four study villages
33
a. Munday Munday is the smallest of the four villages and the only one in which a lateaged adult is the corregidor. Francisco Nate, aged 60, has been the corregidor since the office was first instituted in Munday. The community is also noted among upriver villages for the intra-village influence of one of its female inhabitants: Rogelia Caiti. Due to her prominence in community meetings and notoriety from selling lumber to independent loggers, Rogelia was the only woman included in the status-rankings conducted in the four study villages. Rogelia was born near San Borja, to which she attributes her confidence in public speaking and influence over other Munday residents. In her own words, ―Soy pura borjana (I am a pure San Borjan)‖.
b. Fatima Fatima is the location of a Catholic mission. In 1955, Redemptorist missionaries established Mission Fatima on the banks of the Tsimane River, a small tributary of the Maniqui. They introduced cattle and extracted timber to support the economy of the mission. With the construction of a primary school and health center, Tsimane in nearby upriver villages swelled the ranks of families already living near the mission. The head of the mission, Father Bauer, paid Tsimane with food and other gifts to build an airstrip. He also bought a tractor and employed community residents in the cultivation and sale of rice to San Borja. Previously, upriver Tsimane sold little of their horticultural produce to San Borja markets (Huanca 2006). Despite his evangelism, Father Bauer did not attempt to change Tsimane culture, including the
34
drinking of shoc‟dye (Huanca 2006). However, he would not visit with the local cocojsi, who was later killed when he fell out of favor with the converted Tsimane in Fatima. After Father Bauer died, a Catholic sisterhood from Colombia took over the mission. They continue to run daily religious services, including a Sunday service that draws many of Fatima‘s residents, and they employ several Tsimane in the maintenance of the mission and the airstrip. However, the nuns wield less influence in the community than Javier Canchi, a Tsimane who had served as Father Bauer‘s assistant. Javier leads the Sunday religious services and lives in a stucco house built during the early years of the mission. He is the most vocal during community meetings and has much informal influence over the election of the corregidor. The position of corregidor has changed hands often in Fatima, due to squabbling between Javier and his allies, who live south of the mission, and other village residents, who live north of the mission. Fatima is in effect four different villages: north of the mission, south of the mission, the extended family cluster in Majsi, and the families in Ijnanarej on the other side of the Maniqui, who in recent years have largely been converted to Protestantism. Despite the centripetal influence of the mission, Fatima is the least densely settled community among the four study villages (see Table 1).
c. Jamanchi Jamanchi means ―on the sand‖ in Tsimane and was originally a fishing destination along a sandy forest stream before it became a more permanent settlement.
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Most community members are kin of Juan Tayo and his wife Rosaura Sanchez, who were early residents of Jamanchi. The village has also attracted a number of families who left other forest communities due to interpersonal problems. One such family includes a man who twice committed murder. His second murder occurred while a resident of Jamanchi, but the village residents wouldn‘t punish him and risk retaliation. Instead, the residents of nearby Tacuaral whipped him in public. The corregidor and other respected men in Tacuaral will often arbitrate disputes throughout the nearby forest villages, including Jamanchi.
d. Tacuaral Tacuaral owes its influence over nearby forest communities to both its size and proximity to San Borja. Residents are on average more educated than in other villages, and several men from Tacuaral are employed as teachers in nearby primary schools. Tacuaral has been the site of numerous government and NGO-sponsored projects. In the past five years, a cement basketball court was built near the primary school, and lumber sold to a logging company led to the purchase of a satellite phone, powered by solar panels. The corregidor from 2003 to 2006 was elected despite his small stature and young age (mid-twenties) because he had studied at a technical school in San Borja. Like other influential men in the village, he used community funds from logging concessions for his own purposes and was replaced by the current corregidor, an older, less educated, and more physically formidable individual. Perhaps the most influential man in the village is Felipe Mayer, age 47, who has
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created pamphlets and DVDs on Tsimane mythology, social customs, and traditional subsistence practices with the funding of a university in the Beni. Felipe was elected in 2010 as the head of the Tsimane Grand Council. Like Javier Canchi in Fatima, Felipe Mayer is the most prominent voice in community meetings, and the corregidor will often defer to him. Both Javier and Felipe prefer to be eminence grise rather than hold actual office within their villages. Although Tacuaral is one of the more modernized Tsimane communities, the process of modernization is mosaic within the village. Tacuaral families differ tremendously in their wage income, income from horticultural sales, education, and Spanish fluency. Some men have purchased small motorcycles to travel to town or their fields while other men still hunt with bows and arrows because they can‘t afford bullets. Between 2005 and 2009, the two years when status data was collected, Tacuaral grew in size from immigration but residential density dropped precipitously (see Table 1). Families, particularly those who are less modernized, moved deeper into the forest to live in greater privacy and closer proximity to old-growth forest, where the hunting and soils for horticulture are better.
B. Data Collection Methods The period of data collection spans three field seasons in Bolivia: JulyNovember 2005, June-August 2008, and June-November 2009. The study population included all males over 18 years of age in Munday, Jamanchi, and Tacuaral in 2005 and all males over 21 in Fatima and Tacuaral in 2009. The age range of the study
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population was restricted in these latter two communities due to their large population size. Table 2-2 describes the study population in each village and the dates of data collection.
Table 2-2: Study population and dates of data collection in each village Adult Men
Ever Married Adult Men
Ever Polygynous Adult Men
Data Collection Period
Munday
18*
17
1
Sep.-Oct. 2009
Fatima
89
84
3
Jul.-Aug. 2008
Jamanchi
31
23
1
Oct.-Nov. 2009
Tacuaral (2005)
57
53
0
Jul.-Nov. 2005
Tacuaral (2009)
78
70
0
Jun.-Aug. 2009
* One woman (Rogelia Caiti) is included in the Munday study population
Prior to the start of data collection in 2005, I organized several small focus groups comprised of Tsimane men and women from Tacuaral, Jamanchi, and other communities. I directed the focus groups to discuss how Tsimane men gain influence within their villages. Alberto Maito (26 years old) and Ramon Vie (19 years old) assisted me in the translation of the group dialogue from Tsimane to Spanish. Both men resided in Tacuaral and had worked previously as translators. Based on the focus group discussions, I identified four measures of social status among Tsimane men: (a)
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success in dyadic physical confrontation, (b) ability to get one‘s way in group conflicts, (c) verbal influence in community-wide meetings, and (d) respect from community members. These measures assay relative resource access at different social scales and differ in the degree to which they result from dominance versus prestige. They also lend themselves to empirical evaluation and cross-cultural comparison. The focus group discussions also led to selection of various traits to be evaluated as predictors of status. These include age and traits related to physical size (height, weight, flexed bicep circumference, chest circumference), production (hunting ability, horticultural production, wage labor income), education (Spanish fluency, literacy, years of school), personality (trustworthiness, keeps promises, sense of humor, general work ethic), generosity (meat-sharing, money-lending, providing advice, resolving conflicts, leading village projects), and social support (number of allies in the event of a conflict, number of social visitors, consanguineal and affinal kin). As detailed in Chapter 4, comparison of these traits as predictors of status will identify the bases of social power in Tsimane society. If the predictors of one of the four status measures differ from those of the other measures, we could conclude that status hierarchies among the Tsimane are multidimensional. For example, the traits predictive of dyadic dispute outcomes may contrast or even trade-off with those traits predictive of polyadic influence. With respect to the rewards of status acquisition, the focus groups noted that high status Tsimane men are often married to desirable wives, in terms of
39
productivity and fecundity. Focus group members also believed that high-status men have more extra-marital affairs. Chapter 4 presents and tests a model of how highstatus men achieve reproductive benefits.
1. Photo-ranking To generate rankings of the status measures and their predictors, I asked Tsimane males to photo-rank other males in their community. Status hierarchies are determined by people‘s perceptions of the distribution of social power within their community. I believe that this justifies the measurement of status in this study as the quantified rankings by Tsimane raters of other community members' social standing. Furthermore, subjective impressions are based on years of interpersonal relationships and, thus, are probably better metrics of personal attributes than researchers' observations. Observation and subjective impression do tend to correlate, however. Among the Ache of Paraguay, there is a strong positive correlation between a hunter's actual meat returns and his ranking of hunting success by other Ache (Hill & Hurtado 1996). Among the Shuar of Ecuador, one's work effort as perceived by others is highly correlated with actual work effort (Price 2006). In his study of social status among the Mekranoti of Brazil, Werner (1981) relies on peer ratings, which correlate strongly with his observational measures. At the end of this chapter, I compare several of my photo-ranked measures with additional measures of those traits generated via observation or self-report.
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Half of the men in each village were randomly selected as raters of their adult male village members. The raters represented most ages and all extended families within their village. For the following traits, a rater was shown an array of photographs of men from their community and asked to rank them from highest to lowest: ability to win a dyadic physical confrontation, influence during community meetings, number of allies who would provide assistance during a conflict, ability to get one‘s way in the context of a group conflict, and respect. No one rated themselves. The method by which raters were presented photos of their peers was based on a block design, which varied according to the number of men present in each village. In Tacuaral in 2005, for example, the block design was based on the incidence matrix for the projective plane of order 7. The incidence matrix specifies which photos appear together in a given array, such that evaluation of all arrays compares each photo with every other photo, but no photos appear in the same array together more than once. Tacuaral raters ranked arrays of 8 photographs at a time, and each of the 57 resident men were ranked eight times by eight different evaluators, yielding a range in score from 8 to 64 for each trait. Jamanchi raters ranked arrays of 6 photographs at a time. Photo-ranking in Jamanchi was based on the projective plane of order 5 (yielding a range in scores from 6 to 36). Fatima raters and Tacuaral raters in 2009 ranked arrays of 9 photographs at a time. Photo-ranking in Fatima and Tacuaral in 2009 were based on the projective plane of order 8 (yielding a range in scores from 9 to 81). Since the projective plane of order 8 is based on a sample size of 73, the five youngest men in Tacuaral in 2009 and sixteen men living on the
41
periphery of Fatima were not included in the photo-ranking. Due to the small population in Munday, two-thirds of the men were selected as raters. Munday raters ranked all other men (and Rogelia Caiti) simultaneously for each trait (yielding a range in scores from 12 to 216). Scores from Munday, Jamanchi, and Tacuaral in 2005 were scaled to match the range in score values from Fatima and Tacuaral in 2009. Additional measures were photo-ranked using a different method. For hunting skill, work ethic, wife‘s attractiveness, trustworthiness, ability to keep promises, sense of humor, meat-sharing generosity, money-lending generosity, whether a man is sought after for advice, ability to resolve interpersonal conflicts, and whether a man is frequently visited by others, raters answered ―yes‖ or ―no‖ to the presence of that trait in the photographs presented to them. Raters evaluated two arrays of photographs at the same time using this method. They rated all the photographs on a single trait before evaluating those same photographs on a second trait, and so on. The photographs were again counterbalanced using the block designs. In Tacuaral in 2005, for example, each of the 57 men were rated eight times for every trait, each time by a different rater, yielding a range in score from 0 to 8 for each trait (―yes‖ responses are summed). Scores in Jamanchi varied from 0 to 6, scores in Munday varied from 0 to 12, and scores in Fatima and Tacuaral 2009 varied from 0 to 9. All scores were again scaled to match the range in score values from Fatima and Tacuaral 2009.
42
For all photo-ranked measures, each rater evaluated his peers with no one else present but me. Each rater evaluated all questions within an hour to an hour and a half. The raters were made aware of the confidentiality of their individual rankings. Photos were Polaroids of the top-half of each man's body, set against as neutral a background as possible. Instructions for the photo-ranking were translated into Tsimane from Spanish (with the assistance of Alberto Tayo and Ramon Vie) and then, as a test of the accuracy of translation, back-translated into Spanish by Tsimane men from other communities. All instructions to the raters were given by me in Tsimane. See Appendix A for the instructions and questions presented to raters. For their time, I compensated raters with gifts of fishing hooks, fishing line, bullets, and soap. Given the large number of traits measured via peer photo-ranking, it is possible that the photo-ranking was subject to halo effects. For example, raters‘ impressions of their peers‘ dominance may have biased evaluations of their peers on other traits (c.f. Anderson & Kilduff 2009). However, halo effects are more likely where raters have less situation-specific information available to them (Berger et al. 1980). Tsimane raters possess a lifetime of knowledge about their peers specific to each of the traits they photo-ranked.
2. Observational measures To corroborate the photo-ranked measure of influence during community meetings, I recorded video and audio from five community meetings in Tacuaral in
43
2009. Three of the meetings were attended by both sexes and involved discussion of land tenure, mistreatment by non-indigenous Bolivians, government sponsored horticultural projects, occurrences of theft in the community, the village school, illness among community members, the annual village festival, and other topics. The other two meetings were attended by men only and concerned sale of lumber to a logging company and collective clearing of weeds from the village trails and soccer field. The video and audio recordings of the meetings enable calculation of the number of times individual men spoke, who interrupted whom, and whose ideas gained most support. Time allocation data were collected in Tacuaral under the auspices of the Tsimane Health & Life History Project (THLHP), whose co-PIs are Michael Gurven and Hillard Kaplan. These data allow estimation of the time each man and his wife dedicated to direct childcare, food production (includes hunting, fishing, farming and collecting), and socializing or cooperating with other adults. The time allocation data are based on spot observations between February and December 2005 of all 20 household residential clusters in Tacuaral. Each cluster was observed once a week during a two-hour time block, in which the activities of cluster residents were recorded every half hour. The hours of observation for a given cluster were sampled without replacement until all hours of the day (between 7am and 7pm) were sampled, which began a new round of sampling. On average, 81 spot observations were made of each individual (range =55 to 105). I and other members of the THLHP (Jon
44
Stieglitz, Helen Davis, Amanda Veile, and Lisa McAllister) collected the time allocation data.
3. Demographic, economic, and social network interviews All demographic data used to age individuals, describe kinship relations, determine within-marriage paternity, and identify offspring who have died comes from extensive reproductive history interviews. These interviews were conducted by THLHP co-PI Michael Gurven between 2002 and 2004, and I updated the demographic data with additional interviews during each of my field visits between 2005 and 2009. Men and their wives were interviewed separately, and their responses were cross-validated with other community members‘ responses. Since many Tsimane do not know their exact age, relative and absolute age estimation methods were used in combination to ascertain individuals‘ ages. These methods include comparison of interviewees with photos of Tsimane of known ages, calibration of age with birth order and fertility, linking interviewees‘ life events to dates of historical and ecological significance, and analysis of missionary vital records. In Tacuaral only, I used three well-trusted informants to provide data on men‘s involvement in extra-marital affairs. Based on the informant reports in both 2005 and 2009, I calculate the frequency of extra-marital affairs for all Tacuaral men during the period 2000-2009. Economic interviews were administered to every man in the four villages. These interviews allow calculation of each man‘s average weekly wage labor income,
45
average weekly horticultural commerce income, years of education, literacy, and Spanish fluency. In Tacuaral in 2005, each man was interviewed once a week from February through December. Economic interviews in Tacuaral in 2009 and in the other communities were conducted once per man, who was asked to report income from the previous twelve months. Literacy was determined by the ability to read a standard sentence in Tsimane; the men were recorded as unable to read, able to read poorly, or able to read well. When questioned about his Spanish fluency, each man could indicate no knowledge, minimal knowledge, or fluency. I conducted the interviews in Tsimane with each man in private. Some of the interviews in Fatima were administered with the assistance of Paul Hooper and Dan Cummings, affiliates of the THLHP. Directly following the economic interviews, I asked each man about his social network (this was not done in Tacuaral in 2005). Men were asked to list their regular cooperative partners during hunting, fishing, logging, and horticultural work. They also named food-sharing partners, allies who would assist them in a conflict, and men whose advice they have sought. Each man was asked to describe recent conflicts and name the individuals with whom he quarreled or who helped to resolve the conflicts. In Fatima, Paul Hooper and Dan Cummings provided assistance with these interviews. As with the photo-ranking, all questions in the economic and social network interviews were translated and back-translated with the aid of Tsimane research assistants. See Appendix B for instructions and questions presented to interviewees during the economic and social-network interviews.
46
During 2005 in Tacuaral and during 2008 in Fatima, Tsimane research assistants working for the THLHP conducted weekly interviews of each nuclear family regarding food production and consumption. In Tacuaral, the research assistants were Alberto Maito, Ramon Vie, and Casimiro Tayo, and in Fatima the research assistants were Basilio Tayo and Alberto Cary. Based on their interviews, I calculate average weekly calories produced by men and their wives, the average calories they received from inter-household food sharing, and the frequency with which their household received gifts of food. In 2005, Tacuaral men were also asked about aid received from village members during periods of crop failure or sickness.
4. Anthropometrics The height and weight of all men and women in the four villages were measured annually by medical staff employed by the THLHP. Height in centimeters was measured using a Seca 214 Portable Stadiometer, and weight in kilograms was measured using a Tanita portable digital weigh scale. From these measures, I calculated the BMI of individuals as weight/height2. In 2005 in Tacuaral, I also measured men‘s flexed bicep circumference (on their dominant arm) and chest circumference using a tape measure.
5. Validation of the photo-ranked measures Photo-ranked hunting ability, meat-sharing generosity, frequency one‘s household is visited, ability to resolve conflicts, number of allies, and community-
47
wide influence were validated using additional measures of those traits. A man‘s 2005 photo-ranked hunting ability correlates strongly with the meat calories he produced per hunt-day (r=0.429, p=0.002, n=51), based on weekly self-reports of food production during 2005. However, the hunting ranking did not correlate with calories produced per hour spent hunting (r=0.084, p=0.559, n=51), which suggests the photo-rankings capture overall hunting returns rather than hunting efficiency. Hill & Kintigh (2009) argue that several hundred days of hunting observation are required to accurately distinguish men based on hunting ability. In the absence of such a sample size, peer-rankings based on long periods of observational experience may be more accurate than measured return data. The 2005 photo-ranked measure of meatsharing generosity did not correlate with meat calories shared per day (r=-0.161, p=0.231, n=57), based on the 2005 weekly self-reports of food production. Since there were only 2.32 meat-sharing events, on average, recorded per Tacuaral household across the entire sampling period, the production data may be too noisy for proper validation of the photo-ranked meat-sharing measure. The other photo-ranked measures show better evidence of external validity. The frequency of social visitation a man‘s household experiences, according to 2005 photo-ranking, correlates positively with the amount of time a man spends in social, leisure activities based on 2005 time allocation data (r=0.240, p=0.077, n=57). A man‘s photo-ranked ability to resolve interpersonal conflicts correlates strongly with the frequency others named him as a conflict resolver during the 2009 social network interviews (r=0.420, p<0.001, n=73). A man‘s photo-ranked number of allies from
48
2009 also correlates with the social network interview data, both in terms of selfreported number of allies (r=0.400, p<0.001, n=73) and the number of times other men named him as an ally (r=0.567, p<0.001, n=73). Finally, men photo-ranked highly in community-wide verbal influence in 2009 spoke significantly more often during video-recorded community meetings from 2009 (r=0.528, p<0.001, n=73).
49
Chapter 3. The determinants of status among the Tsimane of Tacuaral
The first aim of this dissertation is to compare the traits that predict status in a small-scale egalitarian society. Before evaluating which traits, more than others, predict adult male social status among the Tsimane of Tacuaral, I present a framework for categorizing and explaining the determinants of status in different human societies. In this chapter, all analyses are restricted to the village of Tacuaral, where the most comprehensive data are available, including longitudinal data. In Chapter 5, the determinants of status are compared across the four Tsimane study villages.
A. How men acquire status across human societies The determinants of status may be viewed as resources, which can be mobilized to inflict costs or confer benefits on others. Status is the effect of such resource mobilization (i.e. social power) within social relationships. Therefore, statusseeking is a self-reinforcing process: resources beget more resources. The determinants of status include embodied, material, and relational capital, which are leveraged to produce changes (either costs or benefits) in another individual‘s embodied, material, and relational capital. Embodied capital refers to wealth that is stored somatically (Kaplan 1996) and may include physical size, health, personality traits, skill, and knowledge. I avoid use of the term ―human capital‖ because it
50
typically is restricted in connotation to skills and knowledge (Becker 1964). Material capital refers to tangible assets, which include land, shelter, food, tools, etc. Relational capital refers to an individual‘s network of social partners (Lin 1999) that may include mates, relatives, friends, followers, or cooperative partners. I do not use the term ―social capital‖ because it has become synonymous with community-level attributes like cooperative norms and institutions, civic participation, and networks of trust (Coleman 1990; Putnam 2000). Community-level social capital is the result of underlying individual decisions, which has unfortunately received little theoretical attention (Glaeser et al. 2002).
Figure 3-1: Distinguishing the determinants of status from social power and social status
Status Determinants
Social Power
Social Status
Embodied Capital Dominance Material Capital Prestige Relational Capital
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Relative Access to Contested Resources
I assume that individuals acquire social status through investments into embodied, material, and relational capital. Relative wealth in these three classes of capital is theoretically distinct from their effects on relative access to contested resources, i.e. social status. To generate status, embodied, material, or relational capital must first be mobilized as social power, whether dominance or prestige (see Figure 3-1 above). Changes in status may then feedback on individuals‘ wealth in the three types of capital. Similar distinctions have been made in political science between social power and the bases of social power (Dahl 1957). In other academic traditions, status is often conflated with its determinants. For example, status is frequently equated with relative income in sociology (Ellis 1993) and in economics (Frank 1985). The determinants of status may be relatively static from culture to culture (e.g. height) or they may vary (e.g. hunting ability). Whether a trait is important for status acquisition depends on how that trait affects the local flow of embodied, material, and relational capital in producing productive and reproductive costs and benefits. The traits that possess the greatest utility for imposing costs or conferring benefits on others in a particular population should best correlate with ratings of social power and social status. Since the marginal utility of a status determinant is affected by its supply and demand, social status may depend upon biological markets (Noe et al. 1991). Individuals who supply uniquely valuable benefits to group members, such as good hunters who are generous with their meat, are held in high esteem and tend to
52
receive more aid in times of illness or injury (Gurven et al. 2000; Sugiyama & Chacon 2000).
However, traits in great supply may remain important to status
acquisition if their utility is inelastic. For example, even if everyone in a community is an equally exceptional and benevolent hunter, an individual who ceases to hunt may lose status because of the necessity of procuring protein for his family. Various socio-ecological factors will affect the marginal utility of particular traits as determinants of status. For example, foraging societies differ in the gains to cooperation. Opportunities for profitable managerial roles, such as in Inuit whaling parties (Spencer 1959), will privilege individuals with the human, material, and social capital conducive to leadership. Foraging societies also differ in the ability of individuals to monopolize material resources. Where resources are economically defensible, as in the salmon-based foraging societies of the Pacific Northwest (Ames 2003), greater inter-individual variance in material capital contributes to greater status inequality. With a more predictable food supply, families are also less dependent on relational capital to buffer risk of food shortfalls (c.f. Gurven et al. 2002). Even with less inter-dependence in food production, however, the gains to relational capital may actually experience a net increase due to greater economies of scale in cooperative production, coalitional contests, and warfare. Major shifts in resource production technology, as with the domestication of plants and animals, alter the suite of skills that optimize embodied capital. Because pastoralism and agriculture shift the major input into production from voluntary skilled labor to defensible material resources (Kaplan et al. 2009), embodied capital
53
takes a backseat to material capital in generating status (Borgerhoff Mulder et al. 2009). Even in some horticultural societies, land can become the limiting input to production. This is the case where productive soils are concentrated in high-quality patches, such as in riverine African villages, or where population pressure is high, as in highland New Guinea (Kaplan et al. 2009). In chiefdoms and states, inherited leadership and massive inequalities in material and relational capital greatly increase the contribution of dominance to social status. In modern states, however, democratic legal institutions curb the ability of individuals to wield human or social capital coercively. Education is integral to the acquisition of material and relational capital in modern, industrial societies. In the following sections, I detail the contribution of specific traits to embodied, material, and relational capital across human societies. I then describe how investments in these traits interact over the life-course.
1. Embodied capital Physical size and strength are components of embodied capital that are most often associated with dominance. Height, weight, and strength are primary determinants of successful fight outcomes in humans (Archer 1988), and lifting strength among U.S. college students predicts self-reported success in resolving interpersonal conflicts (Sell et al. 2009). However, physical size and strength may also lend themselves to prestige. Height and muscle mass may indicate health, attractiveness, athletic performance, and resource production, which will all increase
54
the value of an individual to potential mates or coalition partners. Even in urban nation-states, the large majority of studies find a significant, positive relationship between height and socio-economic status (Ellis 1994). Case and Paxon (2006) suggested that the cross-cultural relationship between height and socio-economic status may be driven by cognitive performance. Better nutrition leads to both tallness and intelligence, and it is the latter that produces socioeconomic success. Excellence in certain skills is commonly associated with prestige in smallscale societies. Hunting prowess is the archetypal male skill among foragers and many horticulturalists and correlates positively with social status almost everywhere the relationship has been tested (Gurven & von Rueden 2006; Smith 2004; Wiessner 1996). Where warfare is prevalent, such as among the Yanomamo (Chagnon 1983) or Achuar (Patton 2000), reputation as a fierce warrior begets social status. Oratory skill is typically requisite for gaining political influence within a community, as is the case with the Benkulu of Sumatra (Fessler 1999), !Kung (Lee 1979), and Semai of Malaysia (Dentan 1979). Rhetoric is perhaps most useful to aspiring leaders as a means of shaping the degree to which they are perceived as sharing a common identity with group-members (Reicher & Hopkins 1996). Other prestige-relevant skills may include expert knowledge of tool manufacture, healing, or supernatural forces. Personality traits, particularly extraversion, are germane to status attainment (Anderson et al. 2001; Judge et al. 2002). In a study of U.S. undergraduate athletic teams, extraversion was more related to peer-rated dominance than to peer-rated
55
prestige (Cheng et al. 2010). Furthermore, dominance was positively related to narcissistic self aggrandizement while prestige was positively related to conscientiousness. Conscientiousness-related personality traits, such as trustworthiness or work ethic, may produce prestige because of their direct benefits to others while other personality traits, such as sense of humor, may confer prestige due to signaling of fitness or intelligence (Miller 1999). A frequently cited determinant of status across human societies is generosity, which signals both production skill and pro-social personality traits. Generosity is likely to vary as a source of prestige, depending in part upon the level of group-wide sharing and the opportunity to recruit and maintain political allies through gift giving (Patton 2005). The costly signaling of cooperative intent through generous donations of food, money, and services may be an important means of being recognized as a valuable social partner or ally (Frank 1988; Gintis et al. 2001; Gurven et al. 2000). The potlatch of the Pacific Northwest (Barnett 1938) and moka of highland New Guinea (Strathern 1971) enabled chiefs and big men to flaunt their embodied and material capital through grand displays of generosity. Among the Gitkasan, individuals would move to new households after potlatches where they felt their leader was not as generous, hence powerful, as others (Adams 1973). Meat-sharing is particularly important to status acquisition among foragers and horticulturalists, including the Yuqui of Bolivia (Stearman 1989) Achuar (Patton 2005), !Kung (Marshall 1967), and Pintupi of Australia (Myers 1980). The best Martu hunters of western Australia share generously even though their meat-sharing is not repaid in
56
kind; their magnanimity gives them access to ritual power as older adults (Bird & Bliege Bird 2010).
2. Material capital The accumulation of material capital is perhaps nowhere more important to status acquisition than in modern, industrial societies, where status is often operationalized as income or as occupation and extent of education, which are close correlates of income (Ellis 1993). Material capital is more important to becoming a leader in the United States than it is for Mekranoti chiefs (Werner 1982), whose horticultural economy does not depend on capital accumulation and the innovation and large-scale collective action it underwrites. Mekranoti chiefs do not differ significantly from their peers in the number of personal ornaments and tools they own (Werner 1981). Among small-scale societies where material capital is more important to production, such as in pastoral and land-limited horticultural societies, material capital is a larger determinant of status (Borgerhoff Mulder et al. 2009). Almost all human societies, including foragers, are now part of a market economy, which places a premium on conspicuous consumption of market goods. Among the Tsimane, men who earn more money from wage labor and sales of horticultural produce devote a greater percentage of their income to the purchase of prestigious and conspicuous leisure items, such as watches and radios (Godoy et al. 2006).
57
3. Relational capital The contributions of embodied and material capital to status acquisition are partly due to their effects on relational capital. People seek social proximity to the strong, skilled, generous, and wealthy because of the knowledge and material goods they might acquire (Henrich & Gil-White 2001) and because of the indirect social value of association with powerful individuals. Among the Xavante of Brazil, men‘s status stems from the in-group social support engendered from one‘s athleticism, oratory skill, hunting ability, sense of humor, and other attributes (Maybury-Lewis 1974). Benenson et al. (2009) studied coalition formation in a laboratory setting and found that people were most likely to choose strong and trustworthy individuals as coalition partners. In exchange for social proximity to high-status group members, individuals offer their deference and support. While relational capital may contribute to dominance as well as prestige, the exploitative use of relational capital can erode one‘s social power. Personal gain based solely on violence or the threat of violence is, in most cultures, considered illegitimate (Riches 1986). The perceived legitimacy of social status is crucial to its maintenance and expansion. Bass (1981) found that legitimate use of power will increase acceptance of demands made by high-status individuals. Blau (1964) describes the process of power legitimation: (1) powerful individuals who are viewed as generous and fair (2) receive the collective approval of group members, which (3) leads to social norms compelling compliance. Whether the result of formal laws or informal norms, legitimacy is best viewed as a constraint on social power rather than as fundamental to power itself.
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Kinship is of particular importance in generating social support. Compared to other primates, humans maintain longstanding male-male alliances due in large part to the presence of strong affinal and consanguineal kinship ties (Chapais 2008; Rodseth et al. 1991). The anthropological literature is replete with examples of male kinship groups as a basis for organization to defend common interests (Otterbein 1968). Even in small-scale societies that lack corporate descent groups and promote an egalitarian ethos, male coalitions based on kinship shape status hierarchies. For example, Efe men from the Congo form affiliative bonds with consanguineal male kin to generate allies in the face of competitive social situations (Bailey & Aunger 1989). Yanomamo men with larger intravillage kinship networks are more likely to be polygynous and powerful (Chagnon 1988a). Marriage is a common strategy for constructing alliances. Hughes (1988) documents several ethnographic examples, including the Nuer of Sudan and Toba of South India, where high-status men are individuals on whom both affinal and consanguineal relatedness are concentrated. Among the Coast Salish of the Pacific Northwest, a man‘s social status was associated with his inter-village alliances, established through marriage (Elmendorf 1971). Kin are not always a wellspring of relational capital. Among the Kipsigis pastoralists, co-resident paternal kin improved child survival only among the materially wealthy (Borgerhoff Mulder 2007) while among Pimbwe horticulturalists, co-resident maternal kin improved child health only among the poor. Co-resident brothers actually decreased a man‘s number of surviving offspring in Dominica,
59
which is attributable to demands siblings make on each other‘s labor and money (Quinlan & Flinn 2005). Wealth in relational capital depends on both the quantity and quality of kin relationships.
4. Status investments over the life-course Cross-culturally, older individuals are typically of higher status because they have had more time to accrue embodied, material, and relational capital. In most small-scale societies, older men (but not necessarily the oldest men) exercise the greatest social power and receive the most deference (Silverman & Maxwell 1978; Simmons 1945). Given the strength requirements of many status-related activities, such as dyadic contest competition, age may not linearly predict status. Strength in male foragers tends to peak in the 20s (Walker et al. 2002). Older individuals, however, may rank highly in political influence since they are likely to be sought after for advice, that is, wisdom, and have more relational capital in the form of direct descendants. Wisdom has been defined as a high level of contextual and procedural knowledge regarding life‘s problems and an ability to formulate appropriate judgments in the face of uncertainty (Baltes & Smith 1990). With increasing age, therefore, prestige may plateau or show diminishing returns rather than decline. On the other hand, older males in many modernizing small-scale societies have had limited access to market-related skills, which are likely an increasingly important predictor of prestige in their societies. Maxwell & Silverman (1970) conjecture that
60
rapid institutional change, leading to information obsolescence, translates into reduced prestige for the elderly. Over the course of their lives, individuals will invest in embodied, material, or relational capital with respect to several parameters: (1) marginal returns in fitness, (2) opportunity costs, and (3) time discounting / risk sensitivity. These parameters will, in part, reflect the within-group supply and demand of the different determinants of status, as well as the intensity of stratification and an individual‘s initial location within the status hierarchies (Kuznar 2002). Furthermore, strategies of investment in the determinants of status need not be consciously motivated. In part, these investment strategies will result from physiological and behavioral adaptations for accruing social status, which respond both to individual condition and environmental contingencies. As a function of fitness, investments in embodied capital, material capital, or relational capital can be subject to either increasing or diminishing returns at different stages of the life course. Strategically acquiring kin through marriage may be of less marginal value when one already has a large kin group. With the introduction of a market economy, people may invest less in specific forms of relational capital. More material capital to draw upon in times of need may cause individuals to devalue resource-sharing partnerships as insurance against risk and uncertainty. Modernization can have adverse consequences on inter-family generosity within traditional societies (Fafchamps 1992; Rosenzweig 1988).
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Muscle anabolism carries different fitness costs and benefits at different life stages. Building more muscle mass when one is already of large size may increase the returns to dominance, especially if investments in other forms of capital would result in lower returns to dominance. This may be true of young boys who experience initial victories in aggressive competition. Fighting yields valuable information about relative strength and the profitability of further investments in strength. However, aggression should decline as individuals gain experience (Fawcett & Johnstone 2010): the male bias in physical aggression is greatest in the 20s (Archer 2004). Without gains either to dominance or prestige, individuals many not be able to afford the costs of muscle anabolism, which include fat catabolism, energetic expenditure, and immuno-suppression (Bribiescas 2001; Muehlenbein & Bribiescas 2005). Testosterone suppresses IgA (Granger et al. 2000; Marshall-Gradisnik et al. 2009), which is the most common immunoglobulin on mucosal surfaces in humans (Kindt et al. 2006). Approximately 90% of human microbial infections involve mucosal sites (Challacombe 1995). In general, testosterone is lower in environments with high energetic demands, parasite loads, and infection rates (Beall et al. 1992; Bribiescas 1996; Campbell et al. 2003; Christiansen 1991; Ellison et al. 1989; Lukas et al. 2004). However, individuals with larger energy budgets can afford to invest heavily in multiple phenotypic traits, trade-offs between them notwithstanding (McDade 2003; Muehlenbein & Bribiescas 2005). Across species, relative male ornament size or quality in adulthood decreases if the animals experienced compromised immune systems as juveniles (Borgia et al. 2004; Jacot et al. 2005; Uller et al. 2006).
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Investments across the determinants of status may be synergistic. For example, height positively predicts adult wages in industrial societies, and this effect is driven primarily by height disparity during the teen years (Persico et al. 2004). Developing pedagogical relationships with skilled individuals builds both embodied and relational capital. Status investments may also be zero-sum. Developing hunting skills probably has opportunity costs with respect to time spent in school and/or in wage labor. Building relational capital within one‘s group may trade off with tie formation across social divides (Balkundi & Kilduff 2006). Within one‘s social group, individuals make decisions concerning how much of their resources to share and with how many others (Gurven 2004). Sharing decisions which optimize resource consumption via reciprocal altruism might trade off with sharing decisions which optimize status acquisition. Multiple equilibria likely characterize the optimal investment of time and energy in status enhancement. Since investments in different forms of capital mature at different rates, timediscounting will shape investment preferences. Physical size, for example, matures earlier than most investments in skill. Strength peaks a decade or two earlier than hunting skill (Walker et al. 2002; Gurven et al. 2006), and wage labor and other income-generating activities depend upon educational investments earlier in life. Therefore, individuals who heavily discount the future may accrue less skill-based expertise. Time-discounting may be a function of intelligence and personality traits related to conscientiousness and restraint, which are the most important predictors of
63
educational achievement, occupational attainment, and subsequent job performance in industrial societies (Caspi et al. 2005; Judge et al. 1999; Shiner et al. 2003).
B. Predictions When individuals directly compete for access to limited resources, status hierarchies become especially palpable. Whether in dyadic confrontation or in jockeying for influence during community-wide meetings, individuals vie for status by marshaling or signaling the embodied, material, or relational capital at their disposal. While prior ethnographies have demonstrated a link between one particular trait and social status, this study of the Tsimane employs a multivariate approach to compare several traits as predictors of status in different social domains. This multivariate approach has two functions: (1) assessment of the relative contribution of different traits to social status and (2) evaluation of the multi-dimensionality of status. If the predictors of status in one domain of social competition differ from the predictors of status in other domains, individuals can hold multiple, independent statuses. An individual may be successful in the context of dyadic confrontation due to physical size, but he may gain community-wide influence due to his oratory skill. Within a given society, therefore, status hierarchies may not be uni-dimensional. The different domains of status competition I evaluate among the Tsimane are the following: (a) success in dyadic physical confrontation, (b) getting one‘s way in group conflicts, and (c) verbal influence in community-wide meetings. I also investigate (d) respect because this term is cross-culturally associated with status and
64
can be directly translated into the Tsimane language. None of these measures should be considered equivalent to dominance or prestige; in all likelihood, each of the status measures will result from elements of both. Furthermore, these measures are not meant to be exhaustive of the range of social status among the Tsimane. Among the Tsimane, dyadic fights are infrequent. They are usually motivated by accusations of theft, stinginess, or sexual jealousy and may be more proximately precipitated by alcohol consumption. I anticipate that physical size measures, such as flexed bicep circumference, chest circumference, height, and weight, predict ranked dyadic fighting ability better than any other variables. I suspect that bicep and chest circumference will be stronger determinants of fighting ability than height since tall, skinny men may be less likely to win a fight than short, brawny men. Group conflicts among the Tsimane often involve two or more families competing over land or other resources, or they may be the progressive fallout from prior dyadic conflicts. The typical number of individuals involved remains small enough that physical size should still play a role in group conflict outcomes, but relational capital as a result of allies will become important as well. Allies will include family members, friends, or exchange partners. Physical size is unlikely to be a direct predictor of influence during community-wide meetings given the large number of individuals involved. In the village of Tacuaral, community-wide meetings have in the past addressed allocation of government benefits, sale of community lumber, internal conflicts and those with colonists, and participation in community development and anthropological projects.
65
These community debates often require interaction with Bolivian nationals, and so literacy, Spanish fluency, experience working with loggers or ranchers, and familiarity with the market town of San Borja are of particular importance to community-wide influence. Pro-social personality traits should predict influence independently of one’s level of modernization. Among the Tsimane, trustworthiness, work ethic, and generosity are often described as valued traits in a man because they indicate longterm, intrinsic motivation to provide for one‘s family and friends and to engage in collective action for the sake of the community. On the other hand, sharing is generally restricted to close kin in extended family household clusters; generosity in meat-sharing or money-lending may therefore have less relevance as a group-wide predictor of influence. I anticipate that relational capital, particularly the number of one’s allies, will mediate much of the effects of the size, skill, personality, and generosity variables upon community-wide influence. I predict that respect reflects not just an individual‘s social power but its legitimacy or collective approval. In Tacuaral, several aggressive, dominant men are prone to drunken brawls and spousal abuse. Anecdotally, these men are viewed unfavorably by others so physical size may not be a strong determinant of respect. Neither may education nor market-related skills. Certain of the more educated and materially wealthy men of Tacuaral are known to manipulate community discussions and decision-making to their advantage. Those with less education or market acumen often resent the influence of their more ―modernized‖ peers. People are also wary of
66
what they don‘t understand. Thus, respect is less likely to accrue to men who excel in novel, market-related skills than to men who excel in more traditional skills, such as horticultural knowledge or hunting ability. In addition, I predict that marketrelated skills will trade-off with hunting ability, even in young men, due to their opportunity costs and the self-selection into schooling of boys showing less promise as hunters or more patience and aptitude for the classroom. The relationship between age and the social status measures will be more quadratic than linear. About 40% of Tsimane men survive to age sixty and beyond (Gurven et al. 2007); these individuals are not as likely to win a dyadic fight or get their way in a group conflict as are younger, physically stronger individuals. Older individuals, however, may rank high on verbal influence during community meetings, in part because they have larger kin networks. On the other hand, older males have had limited access to market-related skills, which are likely an increasingly important predictor of influence in Tacuaral. The majority of schools in Tsimane villages have existed for less than thirty years and so individuals currently above age fifty are less likely to be literate or speak Spanish. I anticipate that the social status measures will increase throughout early adulthood but decline in late age; the ability to win a dyadic fight should show the steepest declines with age and respect the least declines with age.
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C. Data analysis I analyze the determinants of status in Tacuaral both cross-sectionally, using the 2005 data, and longitudinally, comparing the 2005 and 2009 data. All statistical analyses were performed using SPSS version 16.0. For the cross-sectional analysis, I first used factor analysis to improve the subjects-to-variables ratio. I use a maximum-likelihood factor extraction, which allows goodness-of-fit tests, and an oblimin factor rotation, which simplifies the factor structure such that variables load highly on one factor and less on others. I chose an oblique factor rotation method since orthogonal rotation methods generate uncorrelated factors, resulting in a loss of valuable information if the factors are indeed correlated. Of the twenty predictor variables analyzed, five contained less than five non-systematic missing values, which were replaced with the sample means. To reduce my errors of inference due to a small sample size, I divided my predictor variables into two smaller groups before performing a factor analysis on each group. The first group, the ―size and skills‖ variables, yielded three factors: a physical-size factor (on which loaded bicep circumference, chest circumference, height, and weight), a food-production factor (on which loaded hunting ability, hard-working, and horticultural income), and a modernization factor (on which loaded literacy, Spanish fluency, education level, and wage labor income). The size factor captured 26% of the variance in the ―size and skills‖ variables, the food-production factor captured 31% of the variance, and the modernization factor captured 11% of the variance. The factor extraction fit the data well (χ²25=17.906, p=0.846). The second
68
group of predictors, the ―social‖ variables, yielded two factors: a pro-social personality factor (on which loaded keeps promises, trustworthy, gives good advice, lends money, generously shares meat, funny, and visited often) and a social-support factor (on which loaded number of allies and kin network centrality). The kin network measure is the total number of households in Tacuaral in which a man or his wife can claim a full sibling, parent, or offspring. The pro-social personality factor captured 52% of the variance in the ―social‖ variables, and the social-support factor captured 13% of the variance. The factor extraction fit the data well (χ²19=19.114, p=0.450). Tables 3-1 and 3-2 display the rotated factor loadings.
Table 3-1: Rotated factor loadings (pattern matrix) from factor analysis of the Tacuaral size and skill variables from 2005 (n=57)
Height Weight Bicep circumference Chest circumference Hunting ability Work ethic Horticultural income Wage income Literacy Spanish fluency Education
Food Production
Physical Size
Modernization
0.082 0.003 0.046 -0.050 0.974 0.676 0.202 -0.237 0.015 0.112 0.051
0.442 0.923 0.825 0.910 0.073 0.004 0.072 0.166 -0.010 0.112 -0.069
0.166 0.015 0.094 -0.210 -0.012 0.015 -0.344 0.451 0.820 0.784 0.831
69
Table 3-2: Rotated factor loadings (pattern matrix) from factor analysis of the Tacuaral social variables from 2005 (n=57)
Keeps promises Trustworthy Shares meat Lends money Gives advice Funny Visited often Kin centrality Allies
Pro-Social Personality 0.670 0.703 0.896 0.541 0.851 0.570 0.817 -0.035 0.207
Social Support 0.101 -0.132 -0.170 0.250 0.094 0.153 0.056 0.512 0.669
To determine the best predictors of status in Tacuaral in 2005, I use linear regression to compare individuals‘ standardized scores on the status determinant factors with their ranks on each of the four status measures: (a) winning a dyadic fight, (b) getting one‘s way in a group, (c) community-wide verbal influence, and (d) being respected. To each of the four least-squares regression models, I add age and age² as controls. Figure 3-2 depicts the status determinant factors, the variables they comprise, and their predicted relationships with the four status measures. See Table 35 in the next section for the regression results. Standardized betas are reported for ease of comparison of the strength of each factor in predicting the status measure.
70
Figure 3-2: Schematic of predicted relationships (dashed arrows) between the status determinant factors and the social status measures
Status Determinants
Status Determinant Factors
Height Weight Bicep circ. Chest circ.
Physical Size
Good hunter Hort. income Work ethic
Food Production
Wage income Literacy Speaks Spanish Education
Status Measures
Wins Dyadic Fights
Gets Way in Group Modernized
Keeps promises Trustworthy Shares meat Lends money Gives advice Funny Visited often
Pro-Social Personality
Kin centrality Allies
Social Support
Community Influence
71
Respect
A factor analysis using maximum-likelihood extraction and oblimin rotation was also performed on the determinants of status measured in 2009. Four men photoranked in 2005 were not ranked in 2009, due to emigration from the community. An additional twenty men immigrated into the community and were included in the 2009 photo-ranking. Of the predictor variables analyzed, four contained less than five nonsystematic missing values, which were replaced with the sample means. Though the composition of Tacuaral had changed in the intervening four years, and not all of the measures evaluated in 2005 were evaluated in 2009, the factor analysis largely replicated the factor analysis of the 2005 data. The ―size and skills‖ variables yielded a physical size factor (on which loaded height and weight), a food-production factor (on which loaded hunting-ability, hard-working, and horticultural income), and a modernization factor (on which loaded literacy, Spanish fluency, education level, and both horticultural and wage labor income). The size factor captured 13% of the variance in the ―size and skills‖ variables, the food-production factor captured 32% of the variance, and the modernization factor captured 22% of the variance. The factor extraction fit the data well (χ²12=10.418, p=0.579). The ―social‖ variables generated only a single factor, on which loaded keeps promises, lends money, generously shares meat, funny, resolves conflicts, leads projects, visited often, number of allies, and kin network centrality. This single factor explained 61% of the variance in the ―social‖ variables but did not exhibit good statistical fit (χ²27=68.301, p<0.001). Tables 3-3 and 3-4 display the factor loadings.
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Table 3-3: Rotated factor loadings (pattern matrix) from factor analysis of the Tacuaral size and skill variables from 2009 (n=73)
Height Weight Wage income Literacy Spanish fluency Education Horticultural income Hunting ability Work ethic
Food Production
Physical Size
Modernization
0.028 0.119 -0.058 0.001 -0.009 -0.168 0.244 0.963 0.585
0.034 0.188 0.572 0.721 0.738 0.812 0.245 -0.105 -0.309
0.730 0.710 0.054 -0.027 0.157 0.109 -0.138 0.158 0.187
Table 3-4: Factor loadings (factor matrix) from factor analysis of the Tacuaral social variables from 2009 (n=73) Social Kin centrality Shares meat Keeps promises Lends money Funny Resolves conflicts Leads projects Visited often Allies
0.435 0.673 0.861 0.734 0.678 0.882 0.879 0.582 0.901
To replicate the 2005 cross-sectional results and better test the causal claims made in the predictions, I compare Tacuaral men‘s status determinant factor scores in
73
2005 with changes in the status measures over the same period. In addition I compare change in the status determinants with change in the status measures. The factor scores are based on the 57 men present in 2005 and the 73 men present in 2009, but the longitudinal analysis was necessarily restricted to the 53 individuals whose data was collected in both 2005 and 2009. Since the 2009 social variables yielded only a single factor, I compared scores from the 2009 social variables factor with the average scores from the 2005 pro-social personality and social-support factors. I linearly regressed the change in each of the four status measures on the changes in the status determinant factors. To each least-squares regression model, I added men‘s age and age² in 2009 as controls. See Table 3-8 for these regression results.
D. Results 1. Cross-sectional results a. Success in dyadic physical fights Cross-sectional analyses from 2005 of the four status measures and their determinants include all 57 adult men present in the community. The regression model of winning dyadic fights (Table 3-5, column 2) is significant and explains 71.1% of the variance in the data. As anticipated, the strongest predictor of winning fights is the physical-size factor. Height is probably least responsible for this relationship since it loads the least on the physical-size factor among the four physical-size variables (see Table 3-1). Additionally, height produces a smaller bivariate correlation with success in dyadic fights (r=0.571, p<0.001) than does bicep
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circumference (r=0.715, p<0.001) or weight (r=0.779, p<0.001). Chest circumference correlates with relative ability to win dyadic fights but produces the smallest effect size (r=0.595, p<0.001). The social-support factor is also a significant predictor of winning dyadic fights. Marginally significant are the age and age² terms. The foodproduction factor, modernization factor, and pro-social personality factor do not independently predict winning dyadic fights in the regression model.
Table 3-5: Standardized betas from multiple regression of the Tacuaral status measures from 2005 (n=57) Wins Dyadic Fights
Gets Way in Group
Community Influence
Age Age squared Physical size1 Food production1 Modernized1 Prosocial personality1 Social Support1
0.972* -1.049† 0.536‡ 0.046 0.196 -0.093 0.265†
0.305 -0.221 0.285† -0.065 0.010 -0.013 0.468‡
Adj. R Squared F7,49
0.711 20.656‡
0.351 5.323‡
Respect
Social Support2
0.199 -0.026 0.093 0.102 0.301† 0.069 0.628‡
-0.716 0.882 0.027 0.360† 0.056 0.159 0.400†
0.860 -0.601 0.269† 0.112 0.546‡ 0.263† -
0.762 26.585‡
0.388 6.071‡
0.517 10.989‡
*= p<.10, †= p<.05, and ‡= p<.01 1
2
Predictors derived from factor analysis
Initially a predictor variable but subsequently analyzed as a dependent variable due to its strong relationship with the other social-status measures
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b. Getting one’s way in a group The regression model is significant and explains 35.1% of the variance in getting one‘s way in a group. Social support is the strongest predictor of getting one‘s way in a group though physical size is also significant. Neither the age terms nor the other status-predictor factors even marginally approach significance.
c. Community-wide influence The regression model is significant and explains 76.2% of the variance in verbal influence during community-wide meetings. Neither the physical-size factor, food-production factor, pro-social personality factor, nor the age and age² terms independently predict influence in the regression model. The relationship between social support and influence is the strongest of all the regression results. The number of one‘s allies is probably a greater contributor to influence (as well as to the other status measures) than is number of close kin. Number of allies alone explains 40% of the variance in winning a dyadic fight, 28% of the variance in getting one‘s way in a group, 78% of the variance in community influence, and 43% of the variance in respect (adj. R² values). Number of allies, furthermore, loads more heavily on the social-support factor than does kin network centrality (see Table 3-2). The modernization factor is an independent predictor of community-wide influence in the regression model. Unlike wage labor income, I surmise that horticultural commerce income neither predicts influence nor loads strongly on the
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modernization factor because horticultural commerce can be a less rewarding enterprise and does not require tremendous initial investment in one‘s education. Compared to horticultural income, wage labor offers Tacuaral men both higher average weekly earnings ($4.37 US vs. $3.43 US) and potentially higher absolute earnings (wage labor income σ²=27.50 vs. horticultural income σ²=12.80). Wage labor, such as working as a ranch-hand, logger, teacher or agro-forestry consultant for Bolivian nationals, correlates highly with Spanish fluency (r=0.454, p=0.001), literacy (r=0.425, p=0.001), and influence (r=0.256, p=0.056) while horticultural income is un-related to Spanish fluency (r=-0.073, p=0.593), literacy (r=-0.040, p=0.768), or influence (r=-0.109, p=0.426). The question remains, however, whether literacy and Spanish fluency are the results of wage labor or are in fact generating wage opportunities. Controlling for age and age², completed grade level (std. beta=0.695, p<0.001) and not wage labor income (std. beta=-0.095, p=0.350) predicts literacy in a multiple regression (F4,46=20.520, p<0.001). However, both completed grade level (std. beta=0.401, p=0.004) and wage labor income (std. beta=0.252, p=0.055) predicts Spanish fluency (F4,46=8.281, p<0.001).
d. Respect The regression model is significant and explains 38.8% of the variance in respect. While the physical-size factor, modernization factor, pro-social personality factor, and the age and age² terms do not predict respect in the regression model, social support and food production are strong independent predictors of respect.
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Hunting ability loads the highest on the food-production factor (see Table 3-1), and hunting ability correlates strongly with respect (r=0.469, p<0.001). Since respect is not as strongly correlated with reputation as a hard worker (r=0.286, p=0.031) or horticultural commerce income (r=-0.028, p=0.837), hunting ability appears to drive the food production-respect relationship. The food-production and modernization factors negatively co-vary (see Table 3-6 below), which suggests that investments in community-wide influence trade-off with investments in more respected traditional skills, particularly hunting ability. Wage labor income is inversely related to hunting ability (r=-0.298, p=0.026). Controlling for age, however, attenuates the inverse relationship between modernization and traditional food production (partial r=-0.213, p=0.115). Furthermore, modernization is neither a significant negative nor positive bivariate predictor of respect.
78
1
1
1
79
1
1
.036
1
*= p<.10, †= p<.05, and ‡= p<.01 1 Predictors derived from factor analysis
Respect
Community influence
Gets way in group
Wins dyadic fights
Social support
1
Pro-social personality
Modernized
Food production
Physical size
Age
Physical size
Age
1
.292†
.205
1
-.289†
.234*
-.665‡
1
.334†
.350‡
.184
-.096
1
.541‡
.474‡
.225*
.518‡
-.078
Food Modern- Pro-social Social proized personality support duction
.339† .653‡
.525‡ 1
1
1
.419†
.675‡
.588‡ 1
.548‡
.455‡
.115
.459‡
.328†
.146
.863‡
.545‡
.497‡
.244*
.535‡
-.070
.602‡
.278†
.250*
.151
.524‡
.049
.654‡
.301†
.424‡
.242*
.781‡
-.179
Wins CommunGets way dyadic ity Respect in group fights influence
Table 3-6: Pearson correlation coefficients among the Tacuaral social status measures and their predictors from 2005 (n=57)
e. Social support The social-support factor is probably a strong mediator of the other status predictor variables, so I performed a regression to gauge which predictor variables most associate with social support (see Table 3-5, column 6). The regression model is significant and explains 51.7% of the variance in social support. The modernization factor is the strongest predictor of the social-support factor. However, men with more total income do not acquire more social support because they are more generous, whether in meat-sharing (r=0.208, p=0.128) or in money-lending (r=0.208, p=0.128). The physical-size factor and the pro-social personality factor are also independent contributors to social support. Since the pro-social personality factor correlates with all four status measures, especially influence and respect (see Table 36), the effects of pro-sociality on status acquisition are likely mediated by social support. The mediating effect of social support is largely due to number of allies. Prosociality correlates with alliance strength (r=0.508, p<0.001) but not with kin network centrality (r=0.188, p=0.161). Likewise, level of modernization correlates with alliance strength (r=0.473, p<0.001) but not with kin network centrality (r=-0.019, p=0.887). Among the pro-social personality variables, giving good advice loads highest on the pro-social personality factor (see Table 3-2) and produces the strongest correlation with community-wide influence (r=0.507, p<0.001). Generous meatsharing and how often one is visited load nearly as high on the pro-social personality
80
factor. Among the pro-social variables, meat-sharing is the strongest bivariate predictor of respect (r=0.450, p<0.001).
f. Social status and age Figure 3-3 (below) suggests that the social-status measures relate to age quadratically, i.e. show a mid-life peak. The ability to win a dyadic fight produces the strongest quadratic relationship with age (F2,54=6.843, p=0.002), and respect produces the weakest quadratic relationship with age (F2,54=1.418, p=0.251). None of the status measures produce a linear relationship with age (see Table 3-6). With the exception of getting one‘s way in a group, status peaks in the thirties for the average Tsimane male. Respect shows only slight declines with old age. In Tacuaral, there are only ten men older than age fifty. On aggregate, these individuals are not recognized as high status, and they lack many of the traits that are crucial to status acquisition. Age does not linearly predict the physical size, foodproduction, pro-social personality, and social-support factors (see Table 3-6). Age negatively predicts the modernization factor, and age correlates negatively with wage labor income (r=-0.406, p=0.002). Older individuals are in general not overcoming deficits in wage labor income by pursuing alternative income strategies. Age shows no linear relationship with horticultural commerce income (r=0.065, p=0.636). While older men cannot claim more allies (r=-0.104, p=0.442), they may possess relatively more support from kin (r=0.234, p=0.079). This latter relationship would be stronger were the oldest male in Tacuaral in 2005 not a recent immigrant to the community.
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Figure 3-3: Non-parametric LOWESS smoothed curves of each status measure by age, from Tacuaral in 2005 (n=57)
In Tacuaral, the lack of a linear age effect on the polyadic status measures may be largely an artifact of novel conditions (i.e. modernization). When controlling for the modernization factor, age does produce significant partial correlations with getting one‘s way in a group (partial r=0.270, p=0.045), respect (partial r=0.281, p=0.036) and community influence (partial r=0.398, p=0.002). On the other hand, wins dyadic fights produces no partial correlation with age (partial r=0.136, p=0.318).
82
Steep senescence in relative fighting ability beginning in middle age is not likely to be a cohort effect.
2. Longitudinal results Comparison of the 2005 and 2009 factor determinant scores assesses how individuals change relative to other men in Tacuaral rather than how they absolutely increase or decrease in the status determinants. Table 3-7 (below) indicates that the physical size and modernization factor scores did not change, for the 53 men in the longitudinal sample, as much as scores for the food production factor and pro-social personality/social support factor. Time, and the changing composition of the village, afforded these men more opportunity to increase their relational capital and production skill relative to others than to increase their relative physical size or modernization. Among the four status measures, the average individual changed less on his relative ability to win a dyadic fight than on getting his way, community influence, and respect. Mean change is positive, rather than zero, for the status determinant factors and status measures, which indicates that the immigrants to the community not included in the longitudinal analysis were ranked relatively low on all measures. Bivariate correlation between men‘s status in 2005 and 2009 is high for all status measures (see Table 3-7), suggesting that relative change in status was minimal over the four years. Men‘s relative scores on the factor determinants in 2005 and 2009 were also highly correlated (see Table 3-7).
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Table 3-7: Change in the status measures and status determinant factor scores in Tacuaral between 2005 and 2009 Physical size
Food production
Modernized
Pro-social personality/ social support
Mean Δ
0.067
0.140
0.021
0.205
SD
0.590
0.873
0.550
0.649
r
0.789‡
0.549‡
0.834‡
0.663‡
Wins dyadic fights
Gets way in group
Community influence
Respect
Mean Δ
0.231
2.447
2.543
2.983
SD
8.64
8.86
7.78
8.788
0.772‡
0.585‡
0.841‡
0.653‡
r
*= p<.10, †= p<.05, and ‡= p<.01
Absolute change in the status determinants was also minimal. On average, the fifty-three men lost 0.143 centimeters in height (std. dev.=1.240), which is likely the result of measurement error. They gained 1.55 kilograms in weight (std. dev.=3.625). Absolute changes in education (mean=0.472 years; std. dev.=0.953 years), Spanish fluency (4 men gained one point on the Spanish fluency scale), and literacy (11 men improved one point on the literacy scale) were low, but absolute changes in wage income (mean=9.89 boliviano increase per week; std. dev.=78.00 bolivianos per week) and horticultural commerce income (mean=10.76 boliviano increase per week; std. dev.=49.72 bolivianos per week) were more dramatic. This absolute increase in
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average income between 2005 and 2009 occurred as the boliviano appreciated in value (from 0.13 to 0.14 bolivianos per US dollar), and Bolivian prices for rice and other food products nearly doubled. The other measure for which absolute change can be documented is kin network centrality; the 53 men gained an average of 1.792 (std. dev.=1.392) adult male co-resident kin, due to immigration and to their young male relatives‘ entrance into adulthood. Tables 3-8a and b (below) present the longitudinal regression analyses. In general, model fit and variance explained is much weaker in comparison to the 2005 cross-sectional regression analysis (Table 3-5). Men‘s relative scores on physical size, food production, and personality/social support in 2005 show little relationship to men‘s relative change in social status between 2005 and 2009 (Table 3-8a). On the other hand, men‘s relative modernization in 2005 significantly predicts growth in community-wide influence. Comparison of the other status determinants to change in the personality/social support factor reveals positive but marginally significant effects of men‘s relative physical size and modernization. The effects of change in the status determinant factors on change in social status (Table 3-8b) provide better support for the cross-sectional analyses. Since relative change in success in dyadic physical fights was minimal, it is unsurprising that relative change in the status determinants do not strongly predict change in winning dyadic fights. Relative increases in the physical size factor do not significantly correlate with increases in relative fighting ability. However, the bivariate relationship between changes in physical size and relative fighting ability is
85
stronger (r=0.208, p=0.135). Change in the ability to get one‘s way during a group conflict is positively predicted by relative change in the pro-social personality and social support factor and, to a lesser extent, the modernization factor. The increased effect of the pro-social personality and social support factor across winning dyadic fights, getting one‘s way in a group, and community-wide influence replicates the cross-sectional analysis, where the effect of the social support factor also increased the more polyadic the social status measure. Contrary to the effects of relative modernization in 2005, change in the modernization factor does not predict change in community-wide influence. Furthermore, change in wage labor income does not correlate with change in community influence (r=0.021, p=0.881) while change in horticultural income does (r=0.298, p=0.030). Horticultural income loaded on both the food production and modernization factors from 2009. In 2005, horticultural income loaded negatively on the modernization factor. The cross-sectional analyses suggested education generates wage labor opportunities, but increases in education do not predict increases in wage income between 2005 and 2009 (r=0.076, p=0.587). Confirming the cross-sectional analyses, relative modernization is negatively related and relative food production positively related to change in respect. In a bivariate relationship, however, wage income increases do not negatively predict change in respect (r=0.064, p=0.647). The relationship between change in respect and change in food production may be driven more by increases in relative hunting ability, which significantly correlates with change in respect (r=0.266, p=0.054), than by change in horticultural commerce income, which does not significantly correlate with
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change in respect (r=0.087, p=0.537). Change in the pro-social personality and social support factor was made a dependent variable due to its strong relationship with change in the status measures. Changes in the other status determinant factors do not significantly predict change in pro-social personality and social support (Table 3-8b, column 6).
Table 3-8a: Standardized betas from regression of change in the Tacuaral status measures on the relative status determinant scores from 2005 (n=53) Δ Wins Dyadic Fights
Δ Gets Way in Group
Δ Commun -ity Influence
Age Age squared Physical size Food production Modernized Personality/ Social support
-0.110 -0.337 -0.125 0.175 0.362 -0.173
-0.978 0.974 0.052 0.271 0.314 -0.152
1.678 -1.558 -0.138 0.246 0.662† -0.183
1.678 -1.461 0.088 -0.241 0.245 0.242
-0.270 0.345 0.302* 0.042 0.325 -
Adj. R Squared
0.358
-0.027
0.122
0.189
0.130
F6,46
5.829‡
0.768
2.199*
3.021†
2.549†
*= p<.10, †= p<.05, and ‡= p<.01
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Δ Respect
Δ Personality / Social support
Table 3-8b: Standardized betas from regression of change in the Tacuaral status measures on change in the relative status determinant scores (n=53) Δ Wins Dyadic Fights
Δ Δ Commun Gets Way -ity in Group Influence
Δ Respect
Δ Personality / Social support
Age Age squared Δ Physical size Δ Food production Δ Modernized Δ Personality/ Social support
-0.682 0.005 -0.057 -.0114 -0.015 0.198*
-1.266 1.069 -0.078 -0.142 0.235 0.370†
1.007 -1.212 -0.100 0.118 0.001 0.427‡
2.030† -1.932† -0.024 0.212 -0.251* 0.192
0.216 -0.254 -0.191 0.225 -0.186 -
Adj. R Squared
0.370
0.094
0.242
0.158
0.019
F6,46
6.081‡
1.894
3.768‡
2.627†
1.203
*= p<.10, †= p<.05, and ‡= p<.01
The large age² effect sizes in Table 3-8 suggest that relative changes in getting one‘s way, community influence, and respect relate to age quadratically. Of these three status measures, relative change in influence produces the strongest quadratic relationship with age (F2,50=2.586, p=0.085), followed by relative change in respect (F2,50=2.009, p=0.145), and relative change in getting one‘s way (F2,50=0.574, p=0.567). Relative change in winning a dyadic fight is strongly, linearly related to age (F2,50=16.396, p<0.001). On average, Tacuaral men do not experience decreases in relative fighting ability until the late thirties (see Figure 3-4 below), which is roughly equivalent to peak fighting ability from the cross-sectional analysis (Figure
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3-3). Average decreases in getting one‘s way and influence began in the late forties, more than a decade after they peaked in the cross-sectional analyses. Relative respect shows average increases at all ages, with greatest average increases in the forties. This indicates that immigrants to the community subsequent to 2005 were photoranked lower on respect at all ages compared to those men in the longitudinal analysis. As in the cross-sectional analysis, respect is least susceptible to declines in late age among the four status measures.
Figure 3-4: Non-parametric LOWESS smoothed curves of the change in Tacuaral mens’ social status between 2005 and 2009, by age (n=53)
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Chapter 4. The fitness gains of status acquisition
The patterning of individuals‘ investments in embodied, material, and relational capital over their lives is the result, in part, of naturally selected physiological and behavioral strategies for status acquisition. To better understand the evolutionary history of male status-seeking, this chapter investigates how status acquisition generates fitness gains in a small-scale human society (the second aim of the dissertation). I evaluate the pathways from social power to the proximate benefits of status acquisition to lifetime fitness among the Tsimane of Tacuaral. I then compare these results to existing literature on the status-fitness relationship across foragers and horticulturalists.
A. Why measures of lifetime fitness matter Comparison of social status and fertility in present-day societies, particularly small-scale societies, can provide insight into how natural selection may have acted on status-conferring traits in ancestral human environments. If aspects of human behavior and psychology have remained in long-term stasis due to stabilizing selection, then measures of fitness in modern populations will have relevance to our understanding of human evolution. A positive relationship between men‘s social status and fertility is not restricted to pre-modern empires, kingdoms, and sultanates, where high social status included sexual access to a large number of women (Betzig
90
1986). One of the first quantitative investigations of the status-fertility relationship in a small-scale society, among the pastoralist Yomut Turkmen of Iran, revealed that materially wealthy men have more offspring for their age (Irons 1979). Subsequent studies in other small-scale societies found similar evidence of fertility gains to status-determining traits, including: material wealth (Borgerhoff Mulder 1987), hunting skill (Gurven & von Rueden 2006; Kaplan & Hill 1985a; Smith 2004), and warriorship (Chagnon 1988a). High-income men in modern industrial societies also exhibit higher fertility (Hopcroft 2006) but often only after controlling for their level of education (Fieder & Huber 2007; Kaplan & Lancaster 2000) and/or inclusion of childless men in the sample (Nettle & Pollet 2008; Weeden et al. 2006). While cross-cultural evidence, particularly from small-scale societies, suggest that traits conducive to male status acquisition have experienced positive selection throughout human history, the means by which high status men achieve higher fitness remain under-investigated. Past studies are selective in their analysis of the factors responsible for increases in fertility or offspring survivorship among dominant and prestigious men. Rarely are extra-marital affairs evaluated (but see Kaplan & Hill 1985a). Whether the fitness gains of status are concentrated within the nuclear family or within the context of extra-marital affairs is important to debates about the evolution of human pair-bonding and male parental investment (Gurven & Hill 2009; Hawkes et al. 2001, 2010). Identifying the proximate pathways by which dominance and prestige generate current fitness sheds light on the kinds of social relationships evolution has motivated men to maintain.
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However, not all evolutionary biologists endorse the use of lifetime fitness measures to illuminate adaptations. A naturally selected trait will not correlate with fitness everywhere the relationship is tested (Symons 1992). Short-term reproductive success may be random with respect to trans-generationally recurring traits (CluttonBrock 1988), or fitness differentials may be a consequence not of some recurrent phenotypic design but of an unrecognized, correlated trait (Grafen 1988). Despite these concerns, mathematical developments on the Price equation by Grafen (2000) support the measurement of average relative fertility as a marker of natural selection in action. Furthermore, traits that predominate in a population and cause higher fitness than alternatives are likely the product of natural selection (Reeve & Sherman 1993). According to Perusse (1993), the assumption should not be that ―individual reproductive effects are systematically assumed guilty of happenstance until proven innocent by design‖ (pp. 279). Interpretation of trait-fitness relationships becomes problematic when traits are measured only once in an organism‘s life. In the studies of status and fertility described above, one-shot measures of relative social position are compared to men‘s cumulative fertility. Without a longitudinal study design, it is unclear whether men with higher social status for their age maintained their relative position throughout their reproductive lives, or whether their fitness gains were concentrated within a narrower window of time. Furthermore, higher fertility may be driving gains in status as much as the reverse. In this chapter, I use both cross-sectional and longitudinal data to assess the strength and causal direction of the relationship between men‘s
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social status and lifetime fitness. I evaluate the pathways mediating this relationship and address potential confounding variables.
B. Predictions If high status Tsimane men have relatively more surviving offspring, their social power must increase fertility, reduce child mortality, or accomplish both. Social power increases fertility, in part, by granting men access to more (fecund) wives, more durable marital unions, and more numerous extra-pair mates, either because social power signals phenotypic quality (Smith et al. 2003) or represents a priority of resource access valuable to potential mates (Pawlowski & Dunbar 1999). Prediction 1: Socially powerful men have higher fertility.
Dominant and prestigious men may not only achieve higher fertility, but their offspring may experience lower childhood mortality, because children have inherited their parents‘ genetic quality, they are better provisioned, they are protected from disease, or they receive better medical care. Prediction 2: Offspring of socially powerful men experience lower childhood mortality.
While women should prefer husbands who exhibit resource accruing power and commitment (Buss & Shackelford 2008), they may place more weight on indicators of ―good genes‖ when considering extra-marital affairs. Masculinized traits
93
such as muscle mass may be costly signals of genetic quality in the face of testosterone-linked immune-suppression (Folstad & Karter 1992) and other tradeoffs due to increased mating effort (Gangestad & Simpson 2000). Women may prefer dominant, physically robust men as short-term mates due to the developmental stability and ―good genes‖ these traits signal. Women may also engage in extra-marital affairs for short-term resource access. If prestigious men rather than dominant men are better able to provision their mistresses then affairs might be as common to prestige as to dominance. Prediction 3: Socially powerful men have more extra-marital affairs (and more illegitimate offspring).
Women may not prefer dominant men as marital partners if dominant men are more likely to commit partner-directed aggression or provide unreliable paternal investment. U.S. undergraduate women prefer prestigious men over dominant men as romantic partners, particularly in the context of long-term relationships (Snyder et al. 2008). However, U.S. undergraduate women rank dominance even higher than kindness or trustworthiness in an ideal romantic partner if their dominance is directed solely towards other men (Lukaszewski & Roney 2010). It is unclear whether this latter result holds in both short-term liaisons and long-term married relationships. Prediction 4: Socially powerful men marry at earlier ages and have more wives, especially for prestigious men.
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Either by coercion or mutual choice, dominant and prestigious men may be more likely to mate with physically attractive women. Cues of youth, such as smooth skin, are highly valued because female fecundity is strongly age dependent (Williams 1975). Socially powerful men may reproduce well into old age as a result of serial monogamy or polygynous matings with younger women (Marlowe 2000). In traditional societies characterized by low body weight and stature, men also prefer higher body mass index (BMI) in their mates (Marlowe & Westman 2001; Sugiyama 2004). Among women with lower body weight, higher BMI increases neonate weight (Pawlowski & Dunbar 2005), which reduces risk of infant mortality and morbidity (Fields & Frisancho 1993). Furthermore, better nutrition in mothers and earlier weaning of offspring can increase fertility by decreasing birth intervals (Howell 1979). Prediction 5: Socially powerful men marry women who are younger, have higher BMIs, start reproducing early, and who are rated as more attractive by community-members.
Studies among tribal societies show that while men value physical attractiveness more than women, both partners are concerned that long-term mates are hard-working, generous, and high producers (Gurven et al. 2009; Marlowe 2005). Prediction 6: Socially powerful men marry women who are more hardworking and who spend relatively more time in productive and parenting activities.
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Even more important to child survival than securing a genetically robust, healthy, and hard-working wife may be the recruitment of cooperative partners. In times of food scarcity and sickness, the families of prestigious Ache men, particularly those known for their generosity, preferentially receive aid from others (Gurven et al. 2000). Socially powerful men also benefit in times of political conflict from a greater pool of allies (Patton 2005), though the spoils of victory may not necessarily benefit men‘s families. In the face of risk and uncertainty, social status acts as a form of social insurance important for improving survival and capitalizing on resource consumption opportunities. This is less true of dominant than prestigious men, whose skills and prosociality provide direct benefits to long-term cooperative partners. Over the short-term, however, socially powerful men and their families may not differentially benefit from food-sharing or labor assistance. They may be favored in times of sickness or famine, but socially powerful men might have less need in general. Measures of altruism based on short-term observation may not capture the infrequent yet pivotal aid given to socially powerful men. Prediction 7: Socially powerful men, especially those who are prestigious, recruit more cooperative partners with respect to political alliances, food production, and food sharing. Socially powerful men are particularly likely to receive greater support from their peers during periods of food shortage or sickness.
In behavioral experiments, signals of social power elicit more helping behavior (Ball & Eckel 1998; Bickman 1971; Nelissen & Meijers 2011). It is not
96
clear, however, whether these experiments reflect high status individuals‘ ability to garner cooperative partners or to instill deference in their competitors. Deference may accrue more to physically dominant men, whose competitors anticipate the indirect benefits to avoiding costly contest competition. Prestigious men, however, will also receive deference from competitors if the strength of their alliances grants them greater formidability in conflicts. Prediction 8: Socially powerful men, especially those who are dominant, are accorded more deference from community-members.
The pathways from social power to fertility and offspring mortality can be summarized as the following: (1) the length of a man‘s reproductive career and his number of mates, (2) the age, fecundity, health, and productivity of his mates, (3) alliances and exchange partnerships, and (4) resources gained as a result of others‘ deference or acquiescence. While I analyze extra-marital affair frequency, I do not report number of children produced from these affairs, due to the risks of overspeculation on the part of informants. As a result, my comparisons of the social power-fitness pathways are restricted to intra-marital fertility. Figure 4-1 illustrates these pathways, which may interact in more complex ways than depicted. For example, the quality of a wife with respect to offspring survival may depend on the allies (including affinal kin) a man expects to gain through the marriage. Alliances also facilitate mate acquisition. Humans use kin and allies to create, manipulate, or circumvent marriage rules (Chagnon 1988b), to coercively acquire women from
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neighboring groups (Chagnon 1983), and to acquire women via trade or tribute (Betzig 1986). While I model cooperative partnerships and deference from competitors as outcomes of social power, the relationships among these variables are in reality more reciprocal than unidirectional.
Figure 4-1. The pathways from social power to lifetime fitness (1) Better Access To Mates (2) Social Power
Higher Mate Quality
(3)
Surviving Offspring
Partners and Allies Status Determinants
(4) Deference from Competitors (5) (6)
Pathways (5) and (6) in Figure 4-1 represent alternative explanations for the status-fitness relationship. Social status may play a minimal role in a man‘s number
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of surviving offspring if they result more from his individual productivity than from his ability to procure quality mates, engender others‘ deference, or recruit cooperative partners. Furthermore, status may result from having more offspring, rather than the reverse, due to incentives to increase one‘s productivity and social support with increasing child dependency. Longitudinal data are key to testing pathway 6.
C. Data analysis In this chapter, I restrict evaluation of the model in Figure 4-1 to data from Tacuaral. Inter-village comparisons of the status-lifetime fitness relationship are performed in the subsequent chapter. I use the photo-ranked measures of success in dyadic physical fights and community-wide verbal influence as proxies for social power. While neither measure is a pure reflection of either dominance or prestige, the ability to inflict costs is better represented by dyadic fighting success than by community influence, which in Tacuaral is predicted directly and indirectly by prestige-conferring market skills and pro-sociality (see Table 3-5). I first use 2005 cross-sectional data to assess the fitness gains of status acquisition in Tacuaral. All statistical analyses employ SPSS version 16.0. To test the eight predictions and compare the strengths of the pathways in Figure 1, I perform partial correlations (controlling for the log of men‘s age) among the two social power variables, intra-marital live births, intra-marital offspring who died prior to age 15 (as a fraction of total offspring born), intra-marital surviving offspring (who were alive at the time of data collection or who died subsequent to age 15), frequency of extra-
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marital affairs, and eighteen other variables associated with the social power-fitness pathways (see Table 4-1 in the Results section). I preferred a logarithmic age control because quadratic models of the age-specific reproductive data tended to depict decreases in fertility and surviving offspring at the oldest ages. Some of the oldest men in Tacuaral had relatively low fertility for their age. My measure of intra-marital surviving offspring includes children who are currently alive but excludes offspring who died prior to reaching age 15. I do not analyze only those offspring who had reached their reproductive years, given that the majority of offspring in this study are under 15 years old. The pyramidal age structure of the Tsimane means a significant portion of men have only just started reproducing. Despite the right-censoring this introduces in the offspring survivorship data, there are reasons to believe my measure of offspring survivorship is not biased by inclusion of young offspring: (1) if infant and child mortality are constant across men, it shouldn‘t matter in within-population comparisons; (2) if infant and child mortality is greater for low status men, then if anything, I am underestimating the effects of social status; (3) if there are cohort differences in mortality rates (Gurven et al. 2007 shows this to be the case), then controlling for age should account for that. In general, lifetime retrospective methods of fertility estimation are preferable to methods that include individuals who have not completed their reproduction and control for their age. However, both methods produced similar results in other ethnographic settings (e.g. the Dogon of Mali), even though they differed in statistical power and potential bias (Strassman & Gillespie 2003).
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I test five OLS regression models of intra-marital surviving offspring. Models 1 and 2 serve two goals: they directly compare the strengths of the power-fitness pathways, and they determine whether these pathways mediate the effects of the dominance and prestige measures on reproductive outcomes. The independent variables in each model are log age, one of the two social power measures, and each variable from Table 4-1 that produced significant (p<.05) bivariate correlations with both intra-marital surviving offspring and that social power measure. Model 3 directly compares dominance and prestige as predictors of intra-marital surviving offspring. Models 4 and 5 identify whether social power has effects on intra-marital surviving offspring beyond a man‘s productivity and inherited kin network (pathway 5 in Figure 4-1). Independent variables in these models include log age, hunting skill, horticultural income, man‘s consanguineal kin, and either wins fights or influence. The potential for men to achieve higher status due to greater child dependency (pathway 6 in Figure 4-1) was evaluated by controlling for the producer-consumer ratio of each man‘s household when correlating his fertility with his dominance or prestige. If status is a recent response to current child dependency, then measures of dominance and prestige may not predict fertility independent of the ratio of producers to consumers within a man‘s household. A producer was defined as anyone within the household older than fifteen years. Mean production matches mean consumption around age 15 for men and age 20 for women across the Tsimane (Hooper 2011). For the longitudinal analysis, I assess whether relative dominance and prestige in 2005 predicts the number of extra-marital affairs, intra-marital births, intra-marital
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child deaths, and intra-marital surviving offspring a man accrued between 2005 and 2009. I use Poisson regression to compare change in the latter four variables with men‘s dyadic fighting ability and community influence from 2005, and control for men‘s age. To assess whether changes in intra-marital surviving offspring can respond to short-term changes in social power, I use Poisson regression to compare change in social power between 2005 and 2009 with change in intra-marital surviving offspring over that period, controlling for men‘s age. To assess the contribution of pathway 5 (Figure 4-1) to changes in men‘s reproductive success, I use Poisson regression that regresses men‘s number of intramarital surviving offspring between 2005 and 2009 on the following variables measured in 2005: hunting ability, horticultural income, and consanguineal kin. The regression controls for age and the 2005 social power measures. The longitudinal data is particularly useful for examining whether men are motivated to gain status due to greater offspring dependency (pathway 6 in Figure 41). I correlate a man‘s household‘s producer-consumer ratio in 2005 with the change from 2005 to 2009 in his relative dyadic fighting ability and community influence.
D. Results 1. Cross-sectional results Socially powerful Tacuaral men produce more surviving offspring, at least within their marital unions. Winning dyadic physical confrontations significantly predicts number of intra-marital surviving offspring (partial r=0.349, p=0.009). Men
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in the top quartile of winning dyadic fights have on average 1.64 more surviving offspring for their age than men in the bottom quartile (see Figure 4-3a). Communitywide influence is an even stronger predictor of intra-marital offspring survivorship (partial r=0.489, p<0.001). Figures 4-2a and b show the distribution of surviving offspring by influence, with and without log age controls. Men in the top quartile of influence have on average 2.66 more surviving offspring for their age than men in the bottom quartile of influence (see Figure 4-3b).
Figure 4-2a: Tacuaral men’s number of surviving offspring by their communitywide influence (n=57)¹
1
Non-parametric LOWESS-smoothed curve fitted to the distribution
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Figure 4-2b: Tacuaral men’s number of surviving offspring (relative to their age) by their community-wide influence (n=57)1
1
Non-parametric LOWESS-smoothed curve fitted to the distribution
104
Figure 4-3a: Tacuaral men’s number of surviving offspring by dominance quartile (n=57)
105
Figure 4-3b: Tacuaral men’s number of surviving offspring by prestige quartile (n=57)
106
In the following sections, I report the results from tests of the eight predictions outlined in section 4.b. and the results of the multivariate models that compare the social power-fitness pathways. Conclusions are in italic and boldface, followed by description of the statistical results.
a. Dominant and prestigious men have higher fertility, and the offspring of prestigious but not dominant men experience lower childhood mortality I found more support for prediction 1 than for prediction 2: the effect of social power on intra-marital offspring survivorship is due more to its effect on intramarital fertility than on offspring mortality. Winning dyadic physical confrontations predicts intra-marital live births (partial r=0.307, p=0.022) but not intra-marital offspring mortality rate (partial r=-0.072, p=0.622). Men in the top quartile of wins dyadic fights have on average 1.22 more births and a 3.24% lower offspring mortality rate for their age than men in the bottom quartile. Community-wide influence predicts intra-marital live births (partial r=0.449, p=0.001) and intra-marital offspring mortality rate (partial r=-0.247, p=0.087), though the latter result is only marginally significant. Men in the top quartile of influence have on average 2.50 more births and a 9.02% lower offspring mortality rate for their age than men in the bottom quartile. Of the 294 live, intra-marital births attributed to the 57 men in Tacuaral, only 27 of the births ended in death during the first year of life. Fourteen more of the births ended in death within a decade.
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b. Dominant and prestigious men have more extra-marital affairs Dominant and prestigious men had more extra-marital affairs within the previous five years, in support of prediction 3. Frequency of extra-marital affairs is predicted less by winning a dyadic physical confrontation (partial r=0.312, p=0.019) than by community-wide influence (partial r=0.420, p=0.001). Men in the top quartiles of winning dyadic fights and influence have on average 0.85 and 1.19 more extra-marital affairs for their age, respectively, than men in the bottom quartiles. Nineteen of the 57 men in Tacuaral were reported to have engaged in extramarital sex between 2000 and 2005. The majority of these affairs took place outside of the community: only 8 of the 33 total reported affairs involved women married to other Tacuaral men in 2005.
c. Neither dominant nor prestigious men are more likely to remarry nor do their wives have shorter IBIs; prestigious but not dominant men marry at earlier ages Since fertility is determined by both the length of the reproductive period and the rate of births during that period, it is no surprise that a Tacuaral man has higher intra-marital fertility if he marries at a younger age (partial r=-0.328, p=0.023) and the inter-birth intervals of his offspring are lower (partial r=-0.455, p=0.002). Number of serial wives has no bearing on fertility (partial r=-0.094, p=0.495), but men who remarry following divorce or death of their spouse may increase their
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fertility relative to those who do not remarry. Only six men in Tacuaral had remarried during their lives. Socially powerful men are not increasing their fertility by decreasing their wives‘ inter-birth intervals. Neither winning a dyadic confrontation nor communitywide influence predict wife‘s average inter-birth interval (see Table 4-1 below). Furthermore, a man‘s number of serial marriages is predicted neither by winning physical confrontations nor by community-wide influence. Men who win dyadic confrontations do not marry earlier (partial r=-0.023, p=0.879), but in support of prediction 4, men with more community-wide influence do marry at earlier ages (partial r=-0.266, p=0.067). Men in the top quartile of influence married at age 18.5 on average, which is 1.7 years earlier than the average age of marriage for men in the bottom quartile.
109
110 0.123
In-pair surviving offspring
-0.023
Total in-pair fertility -0.232
0.150
Community influence
Offspring mortality rate
0.296**
Wins dyadic fights
Wife age difference (n=53)
0.349***
In-pair surviving offspring
0.307**
Total in-pair fertility -0.072
0.676***
Community influence
Offspring mortality rate
1
Wins dyadic fights
0.043
0.126
Wife average IBI (n=43)
-0.174
-0.180
-0.328**
-0.266*
-0.023
Marriage age (n=49)
-0.526***
0.175 -0.362**
-0.041
-0.523*** -0.455***
-0.350**
-0.080
Wife age first birth (n=49)
0.489***
-0.247*
0.449***
1
0.676***
Commun-ity influence (n=57)
-0.060
0.090
-0.150
0.145
0.260*
0.131
-0.107
0.092
0.420***
0.312**
Extramarital affairs (n=57)
-0.035
0.047
-0.113
0.273*
0.367**
Wife attractive (n=49)
‡ Also controls for household producer-consumer ratio
0.238*
Visited often† (n=57)
0.014
-0.184
-0.179
0.106
0.289*
Wife parent time‡ (n=47)
0.253*
-0.182
0.189
0.506***
(2) Mate Quality
Wife BMI (n=46)
-0.025
0.158
0.017
0.044
0.126
# Serial wives (n=57)
(1) Mate Access
* p<0.10, ** p<0.05, and *** p<0.01 † Also controls for man‘s # of consanguineal and affinal kin living in the community
Fitness Measure
Social Power
Fitness Measure
Social Power
Wins dyadic fights (n=57)
Social Power
0.291**
-0.178
0.281**
0.062
-0.185
Wife production time‡ (n=47)
0.293**
-0.141
0.277**
0.862***
0.573***
Allies† (n=57)
0.032
0.273*
0.115
0.069
-0.030
Food sharing partners† (n=55)
0.131
0.043
0.166
-0.212
-0.123
0.132
-0.148
0.093
0.223*
0.253*
Wife calories produced‡ Wife kin (n=46) (n=57)
0.068
0.012
0.052
0.310**
0.178
Labor partners† (n=55)
-0.207
0.139
-0.125
-0.206
-0.330**
Daily calories received (n=47)
0.361***
-0.129
0.327**
0.525***
0.593***
Gets way in group (n=57)
(4) Deference
-0.110
0.361**
0.055
0.101
-0.017
Times received food (n=52)
(3) Trading Partners and Allies
Table 4-1: Coefficients from partial correlations of social power, social status outcomes, and fitness measures, controlling for the log of men’s age
d. Dominant men but not prestigious men marry women who are younger, have higher BMIs, and who are rated as more attractive; prestigious men but not dominant men marry women with an earlier age at first birth In support of prediction 5, the wives of influential men first give birth at earlier ages (partial r=-0.350, p=0.015). Women married to men in the top quartile of influence first give birth at 17.2 years on average, 2.6 years earlier than women married to men in the lowest quartile of influence. Men who win physical confrontations marry women significantly younger than themselves (partial r=0.296, p=0.033). Men in the top quartile of winning dyadic fights are on average 4.1 years older than their wives while men in the bottom quartile of dominance are on average 0.7 years older. Men who win dyadic fights tend to have wives with marginally higher BMIs and who are rated as more attractive. However, wife‘s BMI and attractiveness are not significantly associated with age-controlled fertility (see Table 4-1).
e. Wives of dominant and prestigious men do not produce more food than other men’s wives; wives of dominant but not prestigious men spend more time caring for offspring To assess parental investment and productivity, I control not only for log age but also for the household producer-consumer ratio, which is indicative of the amount of within-household allo-parenting available. Prediction 6 is partially supported:
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wives‘ time spent interacting with offspring is greater the more likely her husband is to win physical confrontations (partial r=0.289, p=.054) but not if her husband is more influential (partial r=0.106, p=0.490). Men do not spend more time in direct contact with offspring the higher their rank on winning dyadic fights (partial r=0.039, p=0.779) or community influence (partial r=-0.070, p=0.619). Men spend less time in direct food production the more they are physically dominant (partial r=-0.338, p=0.013) or influential (partial r=-0.268, p=0.052), and women‘s time spent in direct food production has no relationship with their husbands‘ social power (see Table 4-1). Although the results are not significant, men tend to produce fewer calories per day the more they are physically dominant (partial r=0.142, p=0.325) or influential (partial r=-0.100, p=0.488), but women‘s average calories produced per day is not significantly related to their husbands‘ social power (see Table 4-1).
f. Dominant and prestigious men have more intra-village kin and allies but not more food-sharing partners; prestigious men have more labor partners and are visited more often than dominant men A man‘s number of co-resident, consanguineal close kin predicts his likelihood of winning a physical confrontation (partial r=0.385, p=0.003) and his community-wide influence (partial r=0.388, p=0.003). I defined close kin as adult male relatives with a coefficient of relatedness to ego of 0.5 or higher (i.e. sibling, parent, or child). Socially powerful men are marginally more likely to be married to
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women with many co-resident kin, though number of affinal close kin is not strongly related to the fitness measures (see Table 4-1). Excluding fifteen men whose postmarital residence is bilocal, socially powerful Tacuaral men are not more likely to live virilocally than uxorilocally (wins fights: partial r=0.162, p=0.346; influence: partial r=0.096, p=0.579). However, men with parents AND parents in-law who have lived in Tacuaral (bilocal post-marital residence) do have more social power (wins fights: partial r=0.259, p=0.067; influence: partial r=0.278, p=0.048). In support of prediction 7, men with more influence are visited more often (partial r=0.506, p<0.001), have more labor partners (partial r=0.281, p=0.042), and have more allies who would aid them in a conflict (partial r=0.862, p<0.001), controlling for log age and number of co-resident consanguineal and affinal close kin. To a lesser degree, men who win physical confrontations are also visited more often (partial r=0.238, p=0.081) and have more allies (partial r=0.573, p<0.001). They do not have more labor partners (partial r=0.140, p=0.317). Neither men who win physical confrontations nor influential men have more food sharing partners (see Table 4-1).
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g. Prestigious but not dominant men are more generous; families of dominant and prestigious men do not in general receive more food from other households, but they are more likely to be aided by non-relatives after crop loss Generous meat-sharing is attributed to influential men (partial r=0.300, p=0.026) but not to men who win physical confrontations (partial r=0.059, p=0.668), controlling for log age and hunting ability. Money-lending is attributed to influential men (partial r=0.390, p=0.004) but not to men who win physical confrontations (partial r=0.216, p=0.121), controlling for log age and average weekly income. Influential men spend more time socializing with other community members (partial r=0.332, p=0.014), and men who win physical confrontations do not (partial r=0.171, p=0.215). The generous food-sharing of influential men is not repaid in kind, at least not in the short-term. Families of higher status Tacuaral men are not given food more frequently than other households nor do they receive more calories per day (see Table 4-1). In fact, physically dominant men‘s households received fewer calories per day from other households (partial r=-0.330, p=0.025) while households with higher offspring mortality rates received more frequent gifts of food (partial r=0.361, p=0.011). In Tacuaral, households produce on average 21,752 kilo-calories of food per day, and they give away 1,683 kilo-calories to other households (principally close relatives). More than half of all production is sold in San Borja or to traveling merchants.
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During occasional periods of sickness or crop failure, all Tacuaral men who were interviewed report that close relatives provide aid in terms of food, money, or labor. Out of the 32 men interviewed, only 5 men reported aid from non-relatives after loss of horticultural crops. They all rank in the top 20% of dyadic fighting ability and top 30% of influence within the community. Only one man (the corregidor) reported aid from non-relatives while he was sick. Status may benefit men and their families less in the short-term and more over the long-term as insurance against unexpected misfortune.
h. Dominant and prestigious men are accorded more deference In support of prediction 8, dominant and prestigious men are more likely to get their way during a group dispute (see Table 4-1).
i. Intra-marital fitness gains are the result of multiple pathways Bivariate correlations suggest that pathways one through four in Figure 4-1 all contribute to the intra-marital fitness gains of Tacuaral men. More surviving offspring is associated with a wife with an earlier age at first birth, more allies, greater likelihood of getting one‘s way, a wife with shorter inter-birth intervals, and a wife who spends more time in food production (see Table 4-1). The latter two variables do not correlate with social power, however.
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Table 4-2: Standardized beta coefficients from regression of Tacuaral men’s surviving offspring on (models 1 and 2) the power-fitness pathways, (model 3) dominance and prestige alone, and (models 4 and 5) determinants of status
Log age Wins dyadic fights Community influence Wife age at first birth Allies Gets Way Hunting ability Consanguineal kin Horticultural income Adj. R² F statistic Total df
Model 1
Model 2
Model 3
Model 4
Model 5
0.740***
0.769***
0.740***
0.670***
0.681***
0.092
-
0.047
0.205**
-
-
0.229**
0.285***
-
0.309***
-
-0.281***
-
-
-
0.112
-
-
-
-
0.118
0.049
-
-
-
-
-
-
0.007
-0.017
-
-
-
0.129
0.070
-
-
-
0.245***
0.253***
0.615 22.934*** 55
0.687 0.649 0.654 0.695 27.327*** 34.862*** 21.027*** 25.126*** 48 55 53 53
* p<0.10, ** p<0.05, *** p<0.01
In regression model 1, which compares the pathways between physical dominance and lifetime fitness, no variable apart from the age term significantly predicts surviving offspring (see Table 4-2 above). Collinearity statistics do not indicate problems with model interpretation, but the strong inter-relationships among winning dyadic confrontations, allies, and getting one‘s way likely reduce their individual predictive power in the multivariate analysis. Getting one‘s way has the largest linear coefficient among these variables, which suggests it is mediating the
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effect of dominance on fitness outcomes. In model 2, which compares the pathways between community-wide influence and lifetime reproductive success, wife‘s age at first birth is the strongest predictor. However, influence remains a significant predictor of surviving offspring. Although number of allies met the criteria for inclusion in model 2, the allies variable was dropped because of its relatively high collinearity with influence (VIF=4.317). Getting one‘s way, the other variable with significant (p<.05) bivariate relationships to both surviving offspring and communitywide influence, is not significant in this model. In model 3, community-wide influence mediates the effect of winning dyadic fights on surviving offspring (see Table 4-2).
j. Social status generates fitness gains independent of men’s skill, income, and inherited kin network Number of offspring surviving to age 15 is positively predicted by hunting ability (partial r=0.247, p=0.070), horticultural income (partial r=0.322, p=0.019), and within-village consanguineal kin (partial r=0.284, p=0.040). Wage income does not predict surviving offspring (partial r=0.084, p=0.550). Models 4 and 5, however, suggest that the status-fitness relationship is not driven by wealthier, more skilled men acquiring fitness independent of their status gains. Nor are socially powerful men accruing more surviving offspring principally because they have inherited more kin support or have lived in the community longer than their peers. In model 4, a man‘s likelihood of winning a dyadic physical confrontation but not hunting ability or
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consanguineal kin significantly predict number of offspring surviving to age 15 (see Table 4-2). Horticultural commerce income remains a strong independent predictor in model 4 and does not correlate with winning fights (partial r=-0.070, p=0.614). In model 5, a man‘s community-wide influence but not hunting ability or within-village consanguineal kin predicts offspring survivorship (see Table 4-2). Horticultural commerce income remains a strong independent predictor in model 5 and does not correlate with influence (partial r=-0.057, p=0.680).
k. Social status differentials are not the result of current child dependency I find little evidence for reverse causality: having a larger family or greater number of dependents does not seem to motivate status seeking. After controlling for both log of age and household producer-consumer ratio, winning a dyadic confrontation (partial r=0.237, p=0.085) and influence (partial r=0.387, p=0.004) still predict intra-marital fertility.
2. Longitudinal results Between 2005 and 2009, fifty-four intra-marital offspring were born to the fifty-three Tacuaral men in the longitudinal sample. Five men experienced the death of one of their children. Over four-fifths of the new births were to men younger than age 40; a Poisson regression indicates that change in surviving offspring is negatively related to men‘s age (beta=-0.032, p=0.020). The regression is significant (Likelihood ratio Χ2=6.085, p=0.014, df=1), based on comparison with the intercept-only model.
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Figure 4-4: Linear relationship between change in Tacuaral men’s surviving offspring from 2005 to 2009 and their dominance (solid line) and prestige (dashed line) from 2005 (n=53)
Men who were ranked in 2005 as more likely to win a dyadic fight gained more intra-marital surviving offspring between 2005 and 2009 (beta=0.027, p=0.028), in a Poisson regression controlling for men‘s age (Likelihood ratio Χ2=10.857, p=0.004, df=2). Men who were ranked in 2005 as more influential during community
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meetings did not (beta=0.006, p=0.671), in a Poisson regression controlling for age (Likelihood ratio Χ2=6.264, p=0.044, df=2). Figure 4-4 (above) compares dominant and prestigious men on change in their number of surviving offspring. The growth in intra-marital surviving offspring for dominant men was due to their relatively higher intra-marital fertility over the four years (beta=0.028, p=0.018) rather than due to offspring deaths (beta=0.001, p=0.977). Men with greater community-wide influence in 2005 experienced more extra-marital affairs between 2005 and 2009 (beta=0.075, p=0.001), in a Poisson regression controlling for age (Likelihood ratio Χ2=28.721, p<0.001, df=2). Men likely to win a dyadic fight also experienced more extra-marital affairs over that period (beta=0.040, p=0.028), in a Poisson regression controlling for age (Likelihood ratio Χ2=20.543, p<0.001, df=2). Comparison of change in offspring survivorship with change in social power between 2005 and 2009 produces different results. In a Poisson regression controlling for age (Likelihood ratio Χ2=6.349, p=0.042, df=2), men who gained in relative fighting ability did not gain more intra-marital surviving offspring (beta=-0.011, p=0.608). In a Poisson regression controlling for age (Likelihood ratio Χ2=7.443, p=0.024, df=2), men who gained influence were also no more likely to increase their number of surviving offspring (beta=0.022, p=0.244). This failure to find effects on lifetime fitness from change in social power may be due to the fact that men‘s relative social power remained fairly constant between 2005 and 2009 (see Table 3-7). A Poisson regression of change in surviving offspring from 2005 to 2009 on wins dyadic fights and other variables from 2005 (hunting ability, horticultural
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income, consanguineal kin, and age) is not supportive of pathway 5 from Figure 4-1. In the regression model (Likelihood ratio Χ2=11.551, p=0.041, df=5), the only significant terms are age (beta=-0.039, p=0.022) and wins fights (beta=0.028, p=0.058). The effects of the other terms are insignificant (hunting ability: beta=0.046, p=0.614; horticultural income: beta=0.003, p=0.451; consanguineal kin: beta=0.029, p=0.744). Pathway 6 from Figure 4-1 is also not supported by longitudinal analysis: a man‘s household‘s producer-consumer ratio in 2005 does not correlate with change between 2005 and 2009 in his ranked fighting ability (r=0.032, p=0.819) or community influence (r=-0.184, p=0.187). Status acquisition does not appear to be a recent response to child dependency.
3. Cross-cultural meta-analysis The Tacuaral results in this chapter are the most complete analysis of the pathways linking social power and lifetime fitness in any small-scale society. A relative lack of such analyses in other societies prevents a detailed corroboration of the Tsimane data. Rather, I use the available ethnographic data to make some general inferences about the linkages between status and fitness across small-scale societies. Table 4-3a (see below) summarizes the relationships between social status and lifetime reproductive success for sixteen different small-scale societies, including the Tsimane. The status measures I evaluate in Table 4-3a include two status determinants (hunting ability and material capital) and two measures of social power
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(success in physical contests and political influence). To the best of my knowledge, the sixteen societies in Table 4-3a represent the extent of the published, quantitative data on male social status and lifetime reproductive success among foragers and horticulturalists. The Trinidad data (Flinn 1986) and Yanomamo political influence data (Chagnon et al.1979) do not include age controls, but all other studies either control for man‘s age or report completed fertility. Where the table lists ―yes‖, a significant and positive relationship was reported. ―No‖ signifies an insignificant relationship, ―neg‖ signifies a significant and negative relationship, and ―maybe‖ signifies indirect evidence for a positive relationship. The references listed in Table 43a pertain to Tables 4-3b and 4-3c as well. Summing across the pairings of status variable with study population, traits associated with male status correlate positively with higher fertility nineteen times out of twenty-two (86%). Of the three non-significant pairings, two produce a near significant positive relationship and one, warriorship among the Waroani (Beckerman et al. 2009), produces a significant negative relationship. In only three populations is offspring mortality evaluated as an independent contributor to total offspring surviving to maturity. Ache men who are better hunters or materially wealthy produce offspring who are less likely to die as children, and this relationship is marginally significant among Tsimane men with more community-wide influence. In contrast, children of acclaimed Waorani warriors experience higher mortality. For twelve results out of sixteen (75%), traits associated with status correlate with more offspring surviving to maturity. Again, the Waorani data alone indicates an opposite effect.
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Table 4-3a: Relationships among measures of social status and lifetime reproductive success across 16 forager and horticulturalist societies
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¹Harpooners only ²But in the predicted direction ³Ages 5-9 only ⁴Offspring show greater seasonal weight increase ⁵Offspring have higher BMI
Table 4-3b (see below) compares societies on pathways 1 (mate access) and 2 (mate quality) from Figure 4-1. Extra-marital affairs are reported for three societies: the reservation Ache (Kaplan & Hill 1985a), Mekranoti (Werner 1981), and Tsimane. As I found for socially powerful Tacuaral men, better Ache hunters and more influential Mekranoti men have higher intra-marital offspring survivorship and more extra-marital affairs. The reproductive measures reported for the other thirteen societies (Table 4-3a) are not explicitly tied to within-marriage reproduction, but the fertility they report is likely concentrated within marital unions and not within extramarital liaisons. In the Ifaluk study (Turke & Betzig 1986), all but 10 of the recorded births are legitimate; in the !Kung study marriage and paternity are closely correlated (Wiessner 2002a), and in the Trinidad study (Flinn 1986) four known cases of cuckoldry do not alter the study‘s results. In seven of ten cases (70%), men who rank higher on hunting ability, material capital, or social power marry at a younger age. In the five study populations where polygyny is compared to social status, two cases (40%) do not produce the expected relationship: influential Mekranoti men are no more likely to be polygynous, and Waorani warriors are less likely to be polygynous. In only three of eight cases (38%) do good hunters, wealthy men, or socially powerful men have more serial wives.
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There is mixed evidence that higher male status in these societies attracts higher quality mates (pathway 2 in Figure 4-1). In five cases out of ten (50%) from Table 4-3b, wives of skilled hunters, wealthy men, or socially powerful men marry earlier or have their first birth at an earlier age. Four of the five non-significant cases pertain to the wives of better hunters. In only one case out of three (33%) does male status correlates with wife‘s BMI. In two cases out of six (33%), women married to skilled hunters, wealthy men, or socially powerful men are more hard-working; the two positive results are for wives of skilled hunters, which is suggestive of assortative mating for productivity. Of the five studies reporting wife‘s inter-birth interval (IBI), only the Ifaluk study finds that the wives of high status men have lower average IBIs.
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Table 4-3b: Relationships among measures of social status, mate access, and mate quality across 16 forager and horticulturalist societies
6
Only for those polygynous societies where the literature reports the number of wives of socially powerful men relative to other men 7 Could include extra-marital affairs 8 Larger women experience higher fertility 9 For polygynous men 10 Household wealth negatively associated with breast-feeding duration
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Greater social support in the form of allies and trading partners (pathway 3 in Figure 4-1) is a ubiquitous covariate with measures of social status. In Table 4-3c (see below), nine of nine cases (100%) demonstrate this relationship. More support from allies does not mean that families of socially powerful men continually receive more food from other households. In the forest Ache (Kaplan & Hill 1985b), Achuar (Patton 2005), Lamalera (Alvard & Gillespie 2004), Meriam (Smith et al. 2003), and Tsimane, generous food sharing or greater contribution to collective food production by highly productive or powerful men is not reciprocated in-kind, at least not in the short-term. Table 4-3c also evaluates potential confounds of the status-fitness relationship across the sixteen societies (pathway 5 in Figure 4-1). In six of eight cases (75%), hunting ability, material wealth, or social power co-varies with some measure of support from co-resident kin. In these societies, it remains possible that men‘s inherited kin network contributes independently to both status and offspring survivorship and is responsible for much of their covariance. On the other hand, high status men‘s direct investment in offspring is an unlikely confound of the statusfitness relationship. In only two of eleven cases (18%) do better hunters, wealthy men, or socially powerful men provide more direct parenting to their offspring, and among influential Aka men there is a significant negative relationship (Hewlett 1988). Although men often gain status because of their skills in production, in only three cases out of eleven (27%) are better hunters, wealthy men, or socially powerful men
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better direct providers for their nuclear families. In only two of five cases (40%) is there clear evidence that families of better hunters receive more meat.
Table 4-3c: Relationships among measures of social status, alliances, co-resident kin, and paternal investment across 16 forager and horticulturalist societies
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11
For generous hunters Though good hunters don't give more food than they receive 13 Polygynous families receive more food from others 14 Influential men give more food than they receive to recruit allies 15 Chiefs' families receive tribute and privileged access to land, and their children have more alloparents ¹6Hunters families aren't privileged in meat sharing ¹7Hunters families receive larger share of meat ¹8Return rates highest for men with most biological children in camp; hunter's family receives larger share of large kills; hunters increase return rates of less widely shared food when they have young children 19 Harpooners' receive proportionally larger shares relative to hunting effort, but this doesn't correlate with offspring number 20 Most turtle hunting returns are shared outside the family and unreciprocated 21 Wealthy men's families consume more imported goods 22 Chiefs and their successors work no more than others 23 More co-resident married offspring 24 Better hunters don't have more co-resident kin to care for their offspring 25 Warriors don‘t come from larger patrilineal descent groups 26 Men with larger patrilineages, but fewer co-resident brothers, have more surviving offspring 27 Father's presence in village increases male's fertility, and mother's presence in village increases female's fertility 28 More coresident brothers 29 More allies (and for influential men, more labor partners) but not more foodsharing partners 12
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Chapter 5. The effects of socio-ecological variation on status hierarchy differences across Tsimane villages
Strategies of status acquisition, the operation and inheritance of status, and the reproductive consequences of status vary across Tsimane villages. The third aim of the dissertation is to test whether this variation is predicted by village differences in socio-ecology, particularly village size and access to material capital. Increases in inequality within human societies have been linked theoretically to population growth (Carneiro 1967; Johnson 1982) and greater access to material capital (Arnold 2010; Bowles 2005), but little ethnographic work has been done on actual transitions in status hierarchies. Before analysis of inter-village differences in status hierarchy among the Tsimane, I discuss why some societies are more egalitarian than others and how differences in resource ecology within and across human societies impact status inequality.
A. Resource ecology and the evolution of status inequality 1. Joint food production and status leveling Most hunter-gatherers in the ethnographic record are egalitarian (Kelly 1995); no individual in these societies wields coercive authority over others, and decisionmaking is highly consensual. Boehm (1999) argues that shifts towards egalitarianism (relative to a chimpanzee-like ancestor) began in the hominid line at least 100,000
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years ago due to several evolutionary developments, notably the coordinated production and distribution of food within and across families. Joint production yokes the fitness of individuals together. However, collective action in food production and distribution carries coordination and free-riding costs. Why did food production become more communal? Compared to other slow-growing primates, humans wean infants at earlier ages and thereby shorten inter-birth spacing and increase fertility rates (Harvey et al. 1987). The greater dependency of a larger number of slow-growing offspring generates high-energetic demands on mothers throughout their reproductive lives (Gurven & Walker 2006). This human life history was made possible in foraging societies by paternal provisioning and a division of labor within families that capitalizes on the comparative advantage of women in gathering and men in hunting (Kaplan et al. 2000). Furthermore, the key productive resources of foraging economies, including game, fruits, tubers, and nuts, are rarely concentrated in stable predictable patches. Food-sharing within and across families pools the risk of underproduction on any given day (Winterhalder 1986). Even in absence of injury or illness, Ache breeding pairs require extra-pair food transfers for on average two weeks out of the year to provision their offspring (Hill & Hurtado 2009). The central importance of cooperative relationships in many small-scale societies leads to status-leveling norms (Boehm 1999; Cashdan 1980). Men have incentives to produce goods surplus to the needs of their family not only to maintain reciprocal food-sharing relationships but also to gain in social power relative to their
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peers. When men boast or claim special rights and privileges, they advertise a lower commitment to the former motive and a greater commitment to the latter. In response, resentful social partners may publically criticize such selfishness and, in extreme cases, seek the ostracism of selfish individuals. Humans are more effective than any other primate in forming leveling coalitions to counter exploitation (Boehm 1999; Pandit & van Schaik 2003). Status-leveling upholds the cooperative risk-pooling central to forager economies. According to one of Lee‘s informants from the !Kung, ―When a young man kills much meat, he comes to think of himself as a chief or a big man, and he thinks of the rest of us as his servants or inferiors. We can‘t accept this. We refuse one who boasts, for someday his pride will make him kill somebody. So we always speak of his meat as worthless. In this way we cool his heart and make him gentle‖ (1979, pp. 246). Other factors contribute to egalitarianism. The development of effective weapons, particularly projectile weapons, lessened the importance of individual strength in fight outcomes (Bingham 1999). Since the resources of foragers tend to be mobile and widely distributed, dissatisfied individuals can more easily move their families away from selfish aggrandizers, i.e. ―vote with their feet‖. Furthermore, an unpredictable distribution of food resources across time and across the landscape reduces their ―economic defensibility‖ (Boone 1992; Brown 1964). Resource patches are not privately owned or transmitted from parents to offspring. A lack of defensible and transmissible material capital is perhaps the most important constraint on the emergence of more hierarchical political organization (Bowles 2005). Average
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household material capital, inequality in its distribution, and its transmission to subsequent generations are minimal in most foragers and horticulturalists in comparison with pastoral and agricultural societies (Borgerhoff Mulder et al. 2009).
2. The power of salmon, acorns, and sweet potatoes Changes in political complexity within human societies, including expansion of administrative bureaucracy and legal institutions, tend to occur in small, sequential steps (Currie et al. 2010). This result is based on phylogenetic modeling of societies from island south-east Asia, ranging from acephalous bands to large states. Gradual shifts in the costs and benefits of status aggrandizement and in the scope of social power led these societies in one direction or another along the continuum from more egalitarian to more hierarchical political structures. Various social and ecological factors have been proposed as the root cause of changes in status inequality throughout human history. Summers (2005) summarizes these factors, which include change in population size (Carneiro 1967; Johnson 1982) and density (Johnson & Earle 2000), agricultural surplus and food storage (Allen 1997), sedentism (Plog 1990), control over the means of production (Marx 1867) including labor (Hayden 1995) and material capital (Arnold 2010), inter-generational transmission of material capital (Bowles 2005), coordination of large-scale projects (Wittfogel 1957), and religious ritual (Earle 1997). All of the above factors are associated with increases in status inequality in certain historical contexts. However, some factors are more universally applicable or
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causally antecedent than others. Increases in status inequality in small-scale societies, for example, are not dependent on plant and animal domestication. Rather, inequality is potentiated in these societies whenever food resources become more abundant, predictable, and heterogeneously distributed across the landscape (Boone 1992). The oak groves and salmon runs of western North America enabled foragers to develop hereditary inequality and even slavery (Ames 2001; Arnold 2010; Coupland 2006; Hayden 1995; Prentiss & Kuijt 2004). In these complex hunter-gatherer societies, individuals with greater social power monopolized predictable resource patches and transmitted these privileges to their offspring (e.g. Chumash: Arnold 2010; Kwakiutl: Wolf 1999). With a more predictable food supply, status-leveling norms are weakened because families are less dependent on each other for risk-pooling (Gould 1982). Also, surpluses of food, whether foraged or farmed, support larger, denser populations in which the socially powerful can employ the services of others in specialized economic activities (Hayden 1995). The introduction of the sweet potato in highland New Guinea produced a surplus economy, in which certain families gained managerial control over exchange networks and political institutions (Wiessner 2002b). Large, dense populations foster technological innovation (Henrich & Boyd 2008), which elites may also exploit. Among the Chumash of Central California, certain families maintained political power and control over others‘ labor through ownership of sea-going canoes (Arnold 2010). Among northern Chumash who lacked large ocean-going canoes, there were no hereditary chiefs as in the southern Chumash (Arnold 2010).
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The evolution of status inequality in small-scale societies is at root ecological. Increases in the abundance and predictability of food resources (1) reduce incentives for risk-pooling and status-leveling, (2) generate surpluses of food and labor, which enables economic specialization, and (3) encourage larger and denser settlement, which leads to technological innovation and economies of scale in production. Wealthier families, who have monopolized the best resource patches or own technology important to production, come to coordinate or usurp the labor of others in diverse economic activities. Inter-generational inheritance of political privilege and material capital, whether land or other commodities, cause ratchet-like increases in status inequality with each generation. Religious ideology and political institutions may help formalize the relative power of wealthy lineages. The rise of hereditary, social stratification is not simply due to powerful families claiming and transmitting a greater share of contested resources. Subordinates may be unable to seek better alternatives or may even prefer greater status differentiation. Circumscription models argue that group fission is kept in check by a scarcity of productive habitat (Carneiro 1970; Kennett et al. 2009) or by external war (McEachron & Baer 1982). Models of reproductive skew (Johnstone 2000; Vehrencamp 1983) predict subordinates will emigrate only when there are minimal ecological constraints on independent reproduction, group productivity is low, and subordinates‘ relative fighting ability and relatedness to dominants are weak. However, group members do not acquiesce to increased status differentiation only to avoid costs, especially since leveling coalitions can be a powerful weapon against the
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socially powerful. Subordinates may prefer increases in status inequality or even institutionalized governance when this helps resolve collective action dilemmas. Acquiescing to the leadership of socially powerful individuals can be mutually beneficial (Smith & Choi 2007). In large groups, cooperation under management can unlock economies of scale in production, reduce resource distribution conflicts, coordinate war or trade, and improve intra-group communication (Johnson 1982; Keeley 1988; Service 1975). In return for a greater share of the spoils, leaders will bear the costs of coordination and monitoring that can derail collective action in large groups (Hooper et al. 2010). Even in predominantly egalitarian societies, decisionmaking authority is occasionally granted to certain individuals to facilitate cooperation. For example, whaling expeditions among the Inuit are capitalized and captained by boat-owners, who maintain their positions through careful distribution of the spoils (Grier 2000).
B. Predictions I test the effects of variation in socio-ecology across Tsimane villages on (1) the determinants of community-wide influence, (2) inequality and inter-generational inheritance of influence, and (3) the reproductive benefits of acquiring influence. I focus much of my analysis on influence rather than the other status measures (i.e. winning dyadic fights, getting one‘s way in a group, and respect) since only influence is measured explicitly at the community-level. The acquisition of status at smaller
136
social scales such as the dyad or small group may not differ tremendously across the villages. I compare inter-village differences in status hierarchies with village size and access to material capital. These aspects of socio-ecology are central to the theoretical and empirical studies of transitions in inequality discussed above. Furthermore, the four villages of Munday, Fatima, Jamanchi, and Tacuaral provide a 2x2 design for comparing village size and modernization to differences in status hierarchies. Munday and Jamanchi are relatively small Tsimane communities while Fatima and Tacuaral are two of the largest communities. Jamanchi and Tacuaral are relatively close to the market town of San Borja, which may mean men in these communities are more educated and have greater access to income than men in the upriver communities of Munday and Fatima. However, Fatima has been the site of a Catholic mission for over fifty years, and the mission has promoted income-generating opportunities for community residents since its inception (see Chapter 2).
Differences in village size will affect how men acquire status. If men are on average more closely related to each other in smaller Tsimane communities, they may also experience fewer same-sex conflicts. Where groups are homogeneous and cohesive, influential individuals are more likely to be group prototypical than possess superlative traits (Hogg et al. 1998). This is because individuals who identify strongly with their group have greater motivation to support a leader who is similar to them versus one who is dissimilar. Thus, community-wide influence in smaller
137
communities may depend less on superlative attributes or skills than on similarity to one‘s peers. Prediction 1: Men in smaller villages have higher average kin relatedness Prediction 2: Men in smaller villages experience fewer same-sex conflicts Prediction 3: Community-wide influence in smaller villages is due less to superlative embodied and material capital and more to kin support.
In larger communities, lower average relatedness and more frequent conflict may foster greater inequality in influence. Community members may permit influential men greater conflict resolution and decision-making authority as a solution to the coordination problems inherent in heterogeneous groups. In large groups, channeling decision-making through leaders can improve communication and prevent conflicts from escalating (Johnson 1982). In turn, greater disparity in influence may increase the attractiveness of influential men to potential mates and allies, strengthening the relationship between status and lifetime fitness. Prediction 4: Community-wide influence is more unequally distributed in larger villages Prediction 5: Influential men in larger villages arbitrate a larger proportion of conflicts Prediction 6: Community-wide influence in larger villages is more likely to associate with intra-village differences in lifetime fitness
138
In villages with greater access to local markets and wage labor, village priorities may have less to do with internal affairs than with political developments in the nearest market town or incursions by farmers, loggers, or other non-Tsimane. As the analyses in Chapter 3 suggest, traditional skills, such as hunting ability, may be less conducive to community-wide influence in more modernized villages than market-related skills, including Spanish fluency, formal education, and wage labor experience. Since older Tsimane men currently possess fewer market-related skills, influence may peak at earlier ages in villages with greater access to material capital. Rapid institutional change, leading to information obsolescence, translates into reduced social power for the elderly (Maxwell & Silverman 1970). Prediction 7: In villages with more material capital, community-wide influence is caused more by market-related skills than by traditional skills, such as hunting ability Prediction 8: In villages with more material capital, influence peaks at younger ages
Generosity may also be less important to community-wide influence in villages with greater access to material capital, and inter-family food sharing may be lower overall. At the community level, modernization can have adverse consequences on inter-family generosity within traditional societies, perhaps because people begin to invest more in material capital than in relational capital as a means of risk reduction (Fafchamps 1992; Rosenzweig 1988). Transitions in food-sharing behavior
139
among the Ache supports this argument: Ache families who live on reservations and have greater access to cultigens and store-bought foods share food less widely than Ache foraging in the forest (Gurven et al. 2002). On the other hand, villages may have greater access to material capital because of cooperative partnerships. The increased horticultural production of some Tsimane villages may depend on increased sharing of field labor across families. Prediction 9: In villages with more material capital, fewer calories are shared across families, men have fewer food-sharing partners, and generosity in food-sharing is less important to community-wide influence Prediction 10: In villages with more material capital, men accrue more labor partners
Community-wide influence in villages with greater access to material capital may be more unequally distributed. This may result in part from increased competition for fertile land for cash-cropping. With more such conflicts, community members may grant influential men greater conflict resolution authority. In villages with more material capital, the emergence of patron-client relationships among coresident Tsimane men also contributes to inequality in their community-wide influence. In these villages, there is larger disparity in the ability of individuals to capitalize horticultural production, through the purchase of tools, pesticides, or even the labor of other Tsimane. Men with more income can afford to pay their coresidents to work in their fields. As a result, they free up time to engage in wage labor
140
outside the community while making net profits from increased horticultural production. Patronage may beget influence because village residents want to maintain good stead with their employers. Prediction 11: Community-wide influence is more unequally distributed in villages with more material capital Prediction 12: Men experience more conflicts in villages with more material capital, in part due to greater competition for land for cash-cropping Prediction 13: Influential men arbitrate a larger proportion of the conflicts in villages with more material capital Prediction 14: Patron-client relationships are more common in villages with more material capital Prediction 15: Influential men in villages with more material capital are more likely to employ their peers in wage labor
Greater inequality of influence in more modernized villages may also result from external political forces. Many traditional societies have shifted toward more prominent political leadership in response to the demands of coordinating with the outside world (Lee & Daly 1999). Among the Mekranoti, chiefs have become ―culture-brokers‖ with missionaries, anthropologists, traders, and government officials. The knowledge and relationships chiefs cultivate as representatives to external political bodies is transmitted to their sons, who become more likely to inherit their fathers‘ leadership position (Werner 1982). In Tsimane villages,
141
particularly those close to San Borja or ranching and logging operations, negotiation with outsiders is a more frequent responsibility of elected corregidores. I predict that the sons of influential men are more likely to inherit their father‘s social power if they live in more modernized communities, due partly to inter-generational transmission of material capital and market-relevant knowledge. Prediction 16: Influential men are more likely to coordinate with outside political bodies in villages with more material capital Prediction 17: Sons of influential men are more likely to inherit their father‟s influence in villages with more material capital
Greater variance in influence in Tsimane villages with greater access to material capital translates into greater disparity in men‘s number of surviving offspring. Wealthier men attract higher quality mates and more allies, which increases their social power and, over the long-run, their reproductive success. Among foragers of Western North America, the privatization of resource patches led to increased variance in intra-community social power and reproductive success, as measured by levels of polygyny (Sellen & Hruschka 2004). While polygyny may contribute to the reproductive gains of high status Tsimane men, the effect is likely to be small. Only five men in all four communities were ever polygynous (see Table 2-2). Prediction 18: Influence in villages with more material capital is more likely to associate with intra-village differences in lifetime fitness
142
C. Data analysis In Table 2-1, I report the population sizes of the four study villages. To distinguish Munday, Fatima, Jamanchi, and Tacuaral (2009 data) in terms of access to material capital, I calculate the average income of the men in each village from horticulture, lumber sales, and wage labor (with non-Tsimane ranchers, loggers, or farmers). I also calculate men‘s average number of visits to a market town (either San Borja or the upriver port of Yucumo). Since the distributions of these variables are fairly skewed, I use the non-parametric Kruskal-Wallis test to compare them across villages. Tables 5-1a and 5-1b present the village comparison results as well as within-village averages and inequality in distribution for these indices of access to material capital. As a measure of inequality, I use the Gini coefficient, which compares the actual distribution of a trait to its uniform distribution. Gini coefficient values range from 0 (perfect equality) to 1 (perfect inequality). Next, I use the Kruskal-Wallis test to compare villages on average kin relatedness, frequency of male-male conflict, calories shared between families, and number of food-sharing partners, field labor partners, and allies (see Table 5-2). I compute a man‘s average kin relatedness with other group members by dividing his number of close kin (number of intra-village households in which he or his wife can claim a full sibling, parent, or offspring) by the total number of households in the village. Conflict frequency is determined by the number of different conflicts men report with their adult male co-residents during the social network interviews; men‘s number of different field labor partners, food-sharing partners, and allies (amongst
143
their male co-residents) is similarly derived. I also report the intra-village frequencies of various categories of conflict, including conflicts over land. To determine village differences in the relationships among the status measures and their determinants, I use partial correlations, which control for the log of men‘s age (see Tables 5-3a through d). In each village, I compare men‘s BMI, hunting ability, meat-sharing generosity, education, wage income, horticultural income, logging income, ability to resolve interpersonal conflicts, number of close kin, and number of allies with the status measures evaluated in Chapter 3: wins dyadic fights, getting one‘s way in groups, community-wide verbal influence, and the respect of peers. To compare the age profiles of status acquisition across the villages, I fit (to 95% of the data) non-parametric LOWESS curves to plots of status by age. To estimate differences in influence inequality, I calculate Gini coefficients in each of the four villages for community-wide influence. I also calculate Gini coefficients for men‘s number of allies, based on the photo-ranking, and the frequency with which men arbitrate inter-personal conflicts, as assessed by the social network interviews (see Table 5-4). I gauge the presence of patron-client relationships in each village based on men‘s income from laboring in other Tsimane men‘s fields and the ratio of paid to unpaid field labor assistance (see Table 5-5). I estimate intergenerational inheritance of the social power measures by correlating the dyadic fighting ability and influence of sons with the same measure for their fathers, controlling for their logged ages. Only in Fatima and Tacuaral are the number of coresident fathers and sons high enough to support statistical estimation of inheritance.
144
To assess village differences in the relationship between influence and lifetime fitness, I correlate number of surviving offspring with community-wide influence in each of the four villages (see Table 5-6). These correlations control for the log of men‘s age. In each village, I also correlate influence with wife‘s age at first birth, given the mediating role of the latter on influential men‘s fitness in Tacuaral in 2005. Finally, I determine whether Tsimane men who married polygynously rank high in influence relative to their monogamous peers.
D. Results 1. Comparing the villages on access to material capital The four villages differ significantly in visits to town, wage labor income, logging income, and horticultural income (see Tables 5-1a and 5-1b). The average Tacuaral man visits town more frequently, earns more from wage labor, and earns more from sale of horticultural produce than the average male resident in the other villages. Tacuaral men sell 56% of the total caloric value of their food production, compared to 23% in Fatima. Jamanchi men cash-crop nearly as much as Tacuaral men, but they rank the lowest in terms of wage labor income and income from lumber sales. The one category in which Tacuaral scores significantly lower than the other villages is sale of lumber. Average income from lumber in Tacuaral is a fifth and a third of the average sales in Munday and Fatima, respectively. Much of this lumber income is illegitimate, sanctioned by neither the community nor the Great Tsimane Council. In general, the income data suggests villages pursue different strategies of
145
income acquisition: upriver men specialize in lumber sales while men living close to San Borja specialize more in horticultural production. Summing across income categories, average income for Tacuaral and Munday men is $1.72 per day while Fatima and Jamanchi men earn $1.14 and $0.89 per day, respectively. However, the distribution of income in all categories is much more unequal in Tacuaral compared to Munday. Only for horticultural income is inequality lower in Tacuaral compared to elsewhere: the Gini for horticultural income is higher in Fatima, at 0.60, than it is in Tacuaral, at 0.51. Considering the relatively egalitarian nature of Tsimane society, income inequality is rather high in all villages. For comparison, the U.S. household income Gini in 2009 was 0.47 (U.S. Census Bureau 2010) and the Bolivia household income Gini in 2009 was 0.58 (U.S. Central Intelligence Agency 2011).
Table 5-1a: Men’s wage income, lumber sales, and town visits by village Daily wage labor income
Daily lumber sales
Annual visits to town
Avg.
Gini
Avg.
Gini
Avg.
Gini
Munday
$0.58
0.56
$0.90
0.46
4.29
0.33
Fatima
$0.36
0.75
$0.52
0.87
6.26
0.46
Jamanchi
$0.24
0.53
$0.13
0.69
5.38
0.43
Tacuaral (2009)
$0.71
0.75
$0.17
0.87
9.81
0.49
Total n Kruskal-Wallis Χ2
212
212
212
10.58†
20.02‡
10.44†
146
Table 5-1b: Men’s wage, horticulture, and lumber income by village
Daily horticulture income
% calories produced that are sold1
Avg.
Gini
Munday
$0.22
0.45
-
Fatima
$0.26
0.60
22.51
Jamanchi
$0.52
0.46
53.28
Tacuaral (2009)
$0.84
0.51
56.43
Total n
212
110
Kruskal-Wallis Χ2
52.36‡
14.12‡
*= p<.10, †= p<.05, and ‡= p<.01 1
Caloric data reported for Tacuaral was collected in 2005
2. Comparing the villages on indices of conflict and cooperativeness Average relatedness among co-resident men is significantly different across the four villages (see Table 5-2 below). In support of prediction 1, men are on average most closely related to each other in Munday, the smallest village, and least related to each other in Fatima, the largest village. This is unsurprising since average relatedness is necessarily a function of village size (see Table 2-1 for the population size of each village).
147
A man‘s reported number of inter-personal conflicts also differs significantly across villages (see Table 5-2). I find mixed support for prediction 2. Frequency of male-male conflict does not clearly track village size. Jamanchi and Tacuaral rank higher in conflicts per man than Fatima, the largest village. On the other hand, Munday is the smallest village and has the lowest incidence per person of male-male conflict. Support is also mixed for prediction 12 that villages with more material capital experience more internal conflicts. Tacuaral and Jamanchi exhibit the most conflicts per man as well as the highest levels of cash-cropping. Competition over land for horticultural purposes is the most frequently cited source of male-male conflict in Tacuaral (see Figures 5-1a through d below). However, theft and alcoholinduced disputes accounts for the largest share of conflicts in Jamanchi. Even though Munday men make relatively little in horticultural income, they also cite land as the most common source of conflict. Furthermore, Munday men make on average as much total income as Tacuaral men but they report the fewest conflicts. Village differences in the frequency of conflict categories must be interpreted with caution. A number of interviewees in Fatima were not asked to report the nature of their conflicts, hence the high frequency of conflicts of type ―unknown‖. Since the conflict data is self-reported, I may be underestimating conflicts due to allegations of spousal abuse or sexual infidelity. Informant reports from Tacuaral suggest such male-male conflicts over women may actually comprise a third or more of all conflicts. Also, conflicts attributed by interviewees to alcohol are probably instigated by one of the other conflict categories as well.
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Figure 5-1a: Sources of conflict in Munday (17 conflicts, 17 men)1
Figure 5-1b: Sources of conflict in Fatima (111 conflicts, 89 men)1
1
―free-ride‖= under-contribution to collective actions; ―debts‖= conflict over money owed; ―alcohol‖= no reason given other than drunkenness; ―alliance‖= pulled into
conflicts involving an ally, or conflicts due to showing favoritism to one‘s coalition
149
Figure 5-1c: Sources of conflict in Jamanchi (46 conflicts, 21 men)1
Figure 5-1d: Sources of conflict in Tacuaral (157 conflicts, 81 men)1
1
―free-ride‖= under-contribution to collective actions; ―debts‖= conflict over money
owed; ―alcohol‖= no reason given other than drunkenness; ―alliance‖= pulled into conflicts involving an ally, or conflicts due to showing favoritism to one‘s coalition
150
The villages differ significantly on several indices of food-sharing (see Table 5-2). Fatima men report the fewest number of regular food-sharing partners, the fewest calories shared between families, and the smallest percentage of production allotted to sharing. Tacuaral families share the most food, both absolutely and relative to total calories produced. Since Tacuaral is a more modernized community, this latter result does not support prediction 9. The increased availability of material capital in Tacuaral does not attenuate inter-family food sharing. Jamanchi men report the largest number of regular food-sharing partners; Jamanchi men earn the least total income but they also earn much more money from food production compared to men in Munday and Fatima. Jamanchi and Tacuaral men also report the most (unpaid) labor partners, in support of prediction 10. However, average number of labor partners does not differ significantly across villages (see Table 5-2). Jamanchi and Tacuaral men also report more allies. As predicted, the lower average numbers of labor partners in Munday and Fatima may be a consequence of less extensive horticultural production. Another explanation may be village density: Fatima is the most sparsely populated of the villages, which limits daily interaction among different family clusters. While Munday is more densely settled than Tacuaral in 2009, Tacuaral residents had lived in much higher density only four years earlier (see Table 2-1). Families may have maintained cooperative partnerships with former neighbors after moving their homes deeper into the surrounding forest.
151
Table 5-2: Village differences in average kin relatedness, frequency of male-male conflict, and cooperation
Kin relatedness
Conflicts per person (over past year)
% All Foodcalories sharing produced partners that are shared1
Munday
0.18
0.47
5.24
Fatima
0.06
1.08
Jamanchi
0.12
Tacuaral (2009)
Allies
Field labor partners (unpaid)
-
4.18
1.35
4.11
1.06
2.63
1.96
1.90
6.81
4.44
5.05
4.09
0.08
1.64
4.89
6.44
4.46
2.02
Total n
218
207
207
128
207
207
KruskalWallis Χ2
16.59‡
21.02‡
12.08‡
37.31‡
20.69‡
5.17
*= p<.10, †= p<.05, and ‡= p<.01 1
Caloric data reported for Tacuaral was collected in 2005
3. Villages differ in the determinants of status As indicated by Tables 5-3a through d (see below), the traits that predict status acquisition in one village do not always predict status acquisition in other villages. However, there are cross-village similarities. Except in Munday, body mass index (BMI) is a universal predictor of winning dyadic fights. BMI does not contribute significantly to community-wide influence or respect, except in Tacuaral. The effect of physical size on influence in Tacuaral may be mediated by number of allies, as I
152
found in 2005 (see Table 3-5). Across villages, number of allies is a universal covariate with the status measures. The counter-intuitive correlations between dyadic fighting ability and other status determinants, particularly hunting ability and number of allies, suggest a strong co-variance among status-determining traits within the same men in each of the villages. In fact, the four measures of status competition correlate significantly with each other in all villages, with the exception of wins fights and respect in Munday (r=0.092, p=0.715, n=18), wins fights and influence in Munday (r=0.267, p=0.285, n=18), and wins fights and respect in Jamanchi (r=0.299, p=0.102, n=31). However, the effect sizes of the latter two correlations are not negligible. I find mixed support for prediction 3 that support from kin is a stronger determinant of influence in smaller villages. A man‘s number of intra-village consanguineal and affinal kin predicts influence in Munday, the smallest community, but also in Tacuaral, the second-largest community (see Table 5-3c). I also do not find clear evidence that influence in smaller communities depends less on superlative skill or material capital. Hunting ability bears the strongest relationship with influence in Jamanchi. Generous meat-sharing, years of education, and income of any source do not significantly predict influence in Munday nor in Jamanchi, but some of the effect sizes are substantial. These variables do significantly predict influence in Fatima and Tacuaral, the largest communities.
153
Table 5-3a: the determinants of winning dyadic fights by village1
1
Diagonally hatched cells indicate significant (p<.05) correlations,
controlling for log age; all significant correlations are positive; dark-filled cells indicate effect sizes > 0.300
154
Table 5-3b: the determinants of getting one’s way by village1
1
Diagonally hatched cells indicate significant (p<.05) correlations,
controlling for log age; all significant correlations are positive; dark-filled cells indicate effect sizes > 0.300
155
Table 5-3c: the determinants of community-wide influence by village1
1
Diagonally hatched cells indicate significant (p<.05) correlations,
controlling for log age; all significant correlations are positive; dark-filled cells indicate effect sizes > 0.300
156
Table 5-3d: the determinants of respect by village1
1
Diagonally hatched cells indicate significant (p<.05) correlations,
controlling for log age; all significant correlations are positive; dark-filled cells indicate effect sizes > 0.300
157
I find mixed support for prediction 7 that, in villages with greater access to material capital, market-related skills are more important than traditional skills in acquiring influence. Tacuaral men earn the most income from wage labor, and Tacuaral is the only village where wage income is a significant predictor of influence (see Table 5-3c). Despite the higher average income from logging in the upriver communities, logging income also significantly predicts influence in Tacuaral. Years of school significantly predicts influence only in Tacuaral and Fatima, the two villages where public education has been available the longest. However, influence in Tacuaral is also linked to the traditionally valued traits of meat-sharing generosity and hunting ability. The relationship between influence and meat-sharing is not driven by men‘s income; men with more income are not more generous meat-sharers in either Tacuaral (r=0.082, p=0.493, n=73) or Fatima (r=0.174, p=0.140, n=73). In contrast with the 2005 data, however, Tacuaral men with more total income in 2009 are rated as more generous money-lenders (r=0.260, p=0.027, n=73). A larger contribution of hunted calories to food production in Jamanchi and Tacuaral may explain why hunting ability in those villages is significantly linked to influence, at least in bivariate relationship. Hunted calories comprise 8.75% and 5.76% of all food production in Jamanchi and Tacuaral, respectively. Hunted game comprises only 1.95% of all food production in Fatima. On the other hand, meatsharing generosity is a predictor of influence in Fatima despite low levels of food sharing relative to total production (see Table 5-2).
158
The determinants of respect by village do not corroborate the 2005 Tacuaral results, in which food production but not the modernization factor predicted respect (see Table 3-6). Logging income does not correlate with respect in any of the villages, but respected men are more educated in all the villages, have more wage income in Tacuaral, and have more horticultural income in Munday. Multiple regression may show education or income have little relationship to respect after controlling for the other status determinants. In Tacuaral in 2009, however, wage income (std. beta=0.416, p<.001) and hunting ability (std. beta=0.428, p<.001) independently predict respect in a multiple regression controlling for log age (F68,3=16.438, p<001). Hunting ability and wage income negatively correlate as in 2005, but not significantly so (r=-0.147, p=0.220). They also show negative but non-significant relationships in Jamanchi (r=-0.161, p=0.433) and in Munday (r=-0.241, p=0.351) but not in Fatima (r=0.042, p=0.724). The patterning of status acquisition by age in each of the four villages (see Figures 5-2a through d below) provides mixed support for prediction 8 that influence peaks at earlier ages in villages with more access to material capital. Munday men are equivalent to Tacuaral men in terms of average total income, but influence in Munday reaches its average maximum the latest of the four villages, close to age 50. In Fatima, influence peaks near age 45, in Jamanchi in the early 40s, and in Tacuaral in the late 30s. On the other hand, village rank in terms of average horticultural income maps exactly onto village differences in peak age of influence.
159
Dyadic fighting ability has a similar age profile in each of the four villages: a peak in the mid 30s and a precipitous drop-off thereafter. In early adulthood, men score higher on winning dyadic fights than on the other status measures. In mid-life, a shift occurs in which men‘s rankings on respect eclipse scores on the other status measures. Respect stays high into old age or shows more modest declines in comparison to the other status measures. Since age correlates negatively with education (r=-0.305, p<.001, n=203) and with total income (r=-0.159, p=.022, n=205), older men may be maintaining respect through meat-sharing generosity (r=0.197, p=0.006, n=195) skill in resolving interpersonal conflicts (r=0.134, p=.061, n=195), and their greater numbers of co-resident close kin (r=0.157, p=.019, n=221).
160
Figure 5-2a: Non-parametric LOWESS smoothed curves of each status measure by age, from Munday (n=18)
161
Figure 5-2b: Non-parametric LOWESS smoothed curves of each status measure by age, from Fatima (n=89)
162
Figure 5-2c: Non-parametric LOWESS smoothed curves of each status measure by age, from Jamanchi (n=31)
163
Figure 5-2d: Non-parametric LOWESS smoothed curves of each status measure by age, from Tacuaral (n=73)
164
4. Villages differ in the inequality and inheritance of influence Distribution of influence within each village is highly unequal (see Table 5-4). The Gini score for community-wide verbal influence is above 0.80 in Tacuaral and close to 0.80 in Jamanchi. Influence inequality is lower in Munday, where the Gini for influence is 0.72, and in Fatima, where the Gini for influence is 0.69. These results support prediction 11 that villages with more material capital, specifically those that exhibit higher levels of cash-cropping, demonstrate greater inequality in social status. I do not find evidence for prediction 4 that influence inequality increases with village size. Such high measures of inequality must be considered in light of the method of data acquisition: community influence was assayed via photoranking, which forced raters to ordinally rank arrays of photos. While the methodology provided fair comparisons across the villages, it may have universally inflated the estimated measures of inequality in social power.
Table 5-4: Inequality in influence, allies, and conflict arbitration, by village
Influence (Gini)
% % Support Conflict arbitrations arbitrations from allies arbitration by men in by (Gini) (Gini) top decile of corregidor influence
Munday
0.72
0.62
0.80
64.71
52.94
Fatima
0.69
0.58
0.73
46.15
10.77
Jamanchi Tacuaral (2009)
0.78
0.80
0.89
82.76
41.38
0.86
0.75
0.88
74.51
50.00
165
Since horticultural income is not a predictor of influence in Tacuaral and Jamanchi (see Table 5-3c), inequality in influence in these villages is not driven directly by men‘s disparity in horticultural income. Rather, variables associated with village-level increases in horticultural production may be responsible, including conflict arbitration inequality and patron-client relationships. Tacuaral and Jamanchi rank higher than Munday and Fatima in inequality of support from allies and inequality in arbitration of inter-personal conflicts (see Table 5-4). Men in the top decile of community-wide influence arbitrate 83% of all interpersonal conflicts in Jamanchi and 75% of all conflicts in Tacuaral. In Munday and Fatima, these figures drop to 65% and 46%, respectively. The village corregidor alone is involved in 50% of all arbitrations in Tacuaral compared to only 11% of arbitrations in Fatima. These results provide more support for prediction 13 than for prediction 5: access to material capital, particularly through increases in horticultural production, and not village size per se contributes to centralization of dispute resolution. In Tacuaral and Jamanchi, where horticultural production is most extensive, employment of Tsimane in field labor by other Tsimane men is more frequent in comparison to the upriver communities (see Table 5-5 below). Thus, support for prediction 14 is mixed: frequency of patron-client relationships tracks average horticultural income but not income from all sources. In Tacuaral, community-wide influence correlate positively with frequency of paying others for their labor (r=0.342,
166
p=0.029, n=41), which is supportive of prediction 15. This relationship is nearly significant in Jamanchi (r=0.436, p=0.071, n=18) but not significant in Fatima (r=0.176, p=0.204, n=54). In Munday, the relationship is negative (r=-0.536, p=0.137, n=9). Tacuaral men earn the most from laboring in other Tsimane men‘s fields, followed by Jamanchi men and then Munday men (see Table 5-5). The relevant data was not collected in Fatima. Annually, each Tacuaral man pays for labor 9.49 times on average, which accounts for 37% of the total field labor assistance he receives. Jamanchi men pay for 24% of all labor assistance and Fatima and Munday pay for only 6% and 5% of field labor help, respectively. The Gini measures for paid labor help are higher in Munday and Fatima because instances of Tsimane employing other Tsimane are relatively rare in those communities.
Table 5-5: Indices of intra-Tsimane patron-client relationships, by village Daily wage from laboring in Tsimane fields
Times paid other Tsimane for labor, annually
% of labor help that is paid
Avg.
Gini
Avg.
Gini
Munday
<$0.01
0.94
0.56
0.84
4.76
Fatima Jamanchi
$0.04
0.80
1.82 4.50
0.74 0.62
5.94 24.32
Tacuaral (2009)
$0.08
0.65
9.49
0.60
37.30
Total n Kruskal-Wallis Χ
2
124
128
8.59†
29.22‡
*= p<.10, †= p<.05, and ‡= p<.01
167
Across the four villages, a man‘s average weekly wage labor income (outside the community) marginally correlates with the number of Tsimane men he paid to work in his field (r=0.166, p=0.065, n=124). Although the effect size is small, it suggests that men who pay others to work their fields have more time for wage labor, or their wage labor provides them the income to employ others. I can provide only anecdotal support for prediction 16, that influential men in villages with more material capital coordinate more frequently with outside political bodies. Of the four villages, Tacuaral has been the site of most investment by NGOs and government agencies. Projects in Tacuaral funded by these organizations and coordinated by influential men in the community have included a well, water tower, fish pond, solar-powered satellite phone, primary school, basketball court, vaccination of children, adult education seminars, and instruction in plant and animal husbandry. The other three villages have primary schools and receive occasional visits from health organizations but have not experienced investment to the same degree as Tacuaral, the Catholic mission in Fatima notwithstanding. Even though Tacuaral men earn less from lumber sales compared to men in the upriver villages, influential men in Tacuaral may negotiate more frequently with logging companies since Tacuaral is adjacent to a forest concession. Furthermore, several Tacuaral men serve with the Grand Tsimane Council, including as its head. Proximity to San Borja is probably a better determinant of village interactions with external political forces than is access to material capital per se.
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Estimates of the inter-generational inheritance of influence do not support prediction 17 that sons are more likely to share their fathers‘ influence in villages with more material capital. In Tacuaral, fathers‘ community-wide influence does not significantly predict their sons‘ influence, controlling for the log of each of their ages (partial r=0.331, p=0.132, n=24). In Fatima, fathers‘ influence does predict their sons influence (partial r=0.470, p=0.012, n=30). On the other hand, fighting ability appears to be strongly inherited in both Fatima and Tacuaral. In Fatima, fathers‘ dyadic fighting ability predicts their sons‘ dyadic fighting ability, controlling for the log of each of their ages (partial r=0.573, p=0.001, n=30). This is also the case in Tacuaral (partial r=0.447, p=0.037, n=24). Inheritance of fighting ability is likely a consequence of body size correlations between fathers and sons. However, sons‘ BMI correlates with fathers‘ BMI, controlling for the log of their ages, in Tacuaral (partial r=0.590, p=0.004, n=24) but not in Fatima (partial r=0.294, p=0.137, n=30).
5. Villages differ in the reproductive outcomes of influence Community-wide influence does not associate with higher lifetime fitness in all villages. In support of prediction 18, but not in both of the larger villages, contrary to prediction 6. In Tacuaral and Jamanchi, but not in the upriver communities, men‘s influence correlates with their number of intra-marital offspring surviving to age 15, controlling for log age (see Table 5-6). In Tacuaral and Jamanchi, influence is even a
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stronger predictor of intra-marital offspring produced (and who did not die) during the previous decade (see Table 5-6).
Table 5-6: Partial correlations (controlling for the log of men’s age) between influence and lifetime fitness, by village Influence – Surviving offspring
InfluenceSurviving offspring produced in last decade
Influence – Wife age at first birth
Munday
0.120
0.008
0.117
Fatima
0.016
0.171
0.085
Jamanchi
0.325*
0.449†
-0.341
Tacuaral (2009)
0.329‡
0.359‡
-0.260†
*= p<.10, †= p<.05, and ‡= p<.01
Since wife‘s age at first reproduction was the strongest mediator of the influence-fitness relationship in Tacuaral in 2005 (see Table 4-2), I assessed its relationship with influence across the four villages. Only in Tacuaral and Jamanchi do wives of influential men give birth at earlier ages, and only in Tacuaral is this effect significant. In a multiple regression combining the Tacuaral and Jamanchi samples and controlling for the log of men‘s age (F77,3=38.625, p<0.001), number of intramarital surviving offspring is independently predicted by both influence (std. beta=0.181, p=0.019) and wife‘s age at first birth (std. beta=-0.194, p=0.014). As in
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the 2005 Tacuaral analyses, wife‘s age at first birth only partially mediates the effect of influence on number of surviving offspring. Besides wife‘s age at first birth, several other variables may be driving the influence-lifetime fitness relationship in Jamanchi and Tacuaral and the absence of that relationship in Munday and Fatima. Influential men in Jamanchi and Tacuaral, but not influential men in Munday and Fatima, are more likely to be good hunters and hire horticultural laborers. Controlling for the log of men‘s age, hunting ability correlates with number of surviving offspring in Tacuaral in 2009 (partial r=0.241, p=0.043, n=69) but not in Jamanchi (partial r=0.205, p=0.296, n=26). However, hunting ability did not mediate the effect of Tacuaral men‘s influence in 2005 on their number of surviving offspring. The frequency with which men pay others for their labor correlates with their number of surviving offspring neither in Tacuaral (partial r=0.038, p=0.817, n=38) nor in Jamanchi (partial r=0.004, p=0.987, n=14). Since Jamanchi and Tacuaral men claim more field labor partners and foodsharing partners, perhaps these latter variables contribute to the social power-fitness relationship in those communities and its absence upriver. However, number of reported field labor partners predicts number of surviving offspring neither in Jamanchi (partial r=0.350, p=0.131, n=22) nor in Tacuaral (partial r=-0.178, p=0.138, n=69), controlling for the log of men‘s age. Number of reported foodsharing partners also predicts number of surviving offspring neither in Jamanchi (partial r=0.340, p=0.142, n=22) nor in Tacuaral (partial r=0.077, p=0.525, n=69). On the other hand, men‘s support from allies, based on photo-ranking, predicts
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surviving offspring in both communities (Jamanchi: partial r=0.333, p=0.084, n=26; Tacuaral: partial r=0.332, p=0.005, n=69). Number of allies do not correlate with surviving offspring upriver (Munday: partial r=0.139, p=0.594, n=18; Fatima: partial r=0.066, p=0.592, n=69). Polygyny is not a contributor to the reproductive gains of high status Tsimane men, at least not in the four communities in this study. No Tacuaral man has been polygynously married, and only one man in Jamanchi has ever had more than one wife at a time (see Table 2-2). The Jamanchi man with a history of polygynous marriage does have the most surviving offspring in the community, at fourteen. However, he is only ranked 13th in influence out of the thirty-one adult male residents. Fatima has the most incidences of polygynous marriage (three) despite the presence of a Catholic mission. Two of these men live on the outskirts of the community and were part of the sixteen men not included in the Fatima status rankings. The third polygynously married Fatima man ranks 15th in influence out of the seventy-three men ranked. The average age of the five ever-polygnous men in this study is 39 so their lack of influence is not due to old age. Although I found that the influence of fathers and sons show significant covariation in Fatima, men‘s number of surviving offspring does not show strong evidence of inter-generational inheritance. Controlling for the log of each of their ages, fathers and sons‘ number of surviving offspring do not correlate in Tacuaral (partial r=-0.041, p=0.858, n=24) nor in Fatima (partial r=0.112, p=0.579, n=30). The correlations between father and sons‘ reproductive success do not improve when
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restricting the analyses to fathers who are in the top half of influence. This is the case in Tacuaral (partial r=-0.496, p=0.145, n=12) and in Fatima (partial r=0.118, p=0.687, n=15). Since there are only 24 and 30 father-son pairs in Tacuaral and Fatima, respectively, the effect sizes in these analyses should be interpreted with caution.
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Chapter 6. Discussion
The aims of this dissertation were threefold: to (1) determine how men acquire social status in a small-scale, egalitarian society; (2) determine how men translate status into reproductive gains; and (3) assess how intra-societal variation in socioecology shapes the determinants, distribution, transmission, and reproductive outcomes of status. Each aim was addressed, in turn, by Chapters 3, 4, and 5. In this chapter, I summarize their results. I then discuss the significance of the results and consider their relevance to the evolution of human male status-seeking behavior.
A. Summary of results 1. The determinants of status in Tacuaral In Chapter 3, I evaluated the traits of Tacuaral men that beget success in four domains of status competition: dyadic fights, intra-group conflicts of interest, community-wide meetings, and respect from peers. Factor analysis segregated the status-determining traits into five factors: physical size, food production, modernization, pro-social personality, and social support. Rankings on the four status measures were inter-correlated but predicted by different traits in multivariate analysis. There are multiple paths to status acquisition among the Tsimane of Tacuaral. The more specific results, based on the 2005 cross-sectional analyses controlling for men‘s age, are as follows:
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Physical size is the primary determinant of dyadic fight outcomes
Social support (due to men‘s allies and co-resident kin) is slightly more predictive than physical size of getting one‘s way in a group
Greater social support and exposure to modernization (via wage labor or education) independently result in community-wide influence
Greater social support and skill in food production (principally hunting ability) generate respect; more modernized men are not more respected
Larger physical size, greater modernization, and generosity are independently associated with more social support, and social support mediates their effects on the status measures
Men with more income do not acquire more social support because they are more generous, whether in meat-sharing or in money-lending
With respect to the patterning of the status measures by age, I found the following:
The status measures rise with age until the 30s, when they begin to decline (especially winning dyadic fights)
Respect remains relatively flat into old age
Figure 6-1 (see below) diagrams the most significant predictors of the status measures in Tacuaral from 2005.
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Figure 6-1: The independent, linear predictors of four measures of adult male social status in Tacuaral from 2005 (n=57)¹
Physical Size
Wins Dyadic Fights
Food Production
Gets Way in Group
Modernized
Community Influence
Pro-Social Personality
Social Support
1
Respect
Arrows indicate multiple regression weights with standardized values >.25 and p values <.05; arrows in boldface indicate multiple regression weights with standardized values >.45 and p values <.01 (see Table 3-5)
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Longitudinal analyses of the status determinants, which compared 2005 with 2009 Tacuaral data, corroborate several of the cross-sectional results but depart from them in some significant ways. In general, men‘s relative scores on the status measures and their determinants changed little between 2005 and 2009. Analyses of the changes that did occur produced the following results:
Change in men‘s relative ability to win dyadic fights was not significantly affected by the baseline measures of the status determinants nor their change between 2005 and 2009
Relative increases in getting one‘s way and especially community influence were due to gains in pro-sociality and social support
Relative modernization in 2005 but not change in relative modernization correlated with change in influence
Relative increase in respect was due to relative gains in food production (particularly hunting ability) and decreases in modernization (but not wage income per se)
Longitudinal changes in status by age were as follows:
Men who were in their 20s gained in relative fighting ability, but these gains became progressively smaller as they entered their 30s; by 40, men began progressive declines in relative fighting ability
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Relative rank in getting one‘s way and influence changed little for men in their 20s and 30s and showed only modest declines in the oldest ages
Growth in respect relative to one‘s peers was highest for men in their 40s and decelerated at older ages (but never became negative)
2. Status and lifetime fitness in Tacuaral In Chapter 4, I found that the rewards of status acquisition in Tacuaral include higher lifetime fitness. Men ranked highly in dyadic fighting ability and especially in community-wide influence have more live births and surviving offspring within the context of their marriages, as well as more extra-marital affairs. Influence but not fighting ability is associated with a lower intra-marital offspring mortality rate. I evaluated the means by which social power, as gauged by winning dyadic fights and community-wide influence, increases men‘s number of intra-marital surviving offspring. The more detailed cross-sectional results from 2005, which control for men‘s age, are as follows:
The wives of socially powerful men, specifically men with influence, first give birth at earlier ages, but they do not have shorter inter-birth intervals
Men who are ranked highly in fighting ability marry women who are significantly younger than themselves, have larger body mass indices, and are rated as more attractive
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The wives of socially powerful men do not produce more food than other men‘s wives; wives of men ranked highly in fighting ability spend more time in direct contact with their offspring
Influential men are more generous food-sharers; their families do not in general receive more food from other households, but socially powerful men are more likely to receive aid from non-relatives during periods of crop failure.
Socially powerful men have more political allies and are accorded more deference
Socially powerful men are more likely to live bilocally post-marriage, and they have both more consanguineal and affinal kin living in the community
The relationship between the social power measures and intra-marital surviving offspring is not an artifact of men‘s productivity, inherited support from consanguineal kin, or current child dependency
Men who win dyadic fights have more intra-marital surviving offspring largely because they are also influential
Wife‘s age at first birth only partially mediates the influence-surviving offspring relationship; number of allies may also contribute to this relationship given its isomorphism with influence
Figure 6-2 (see below) diagrams the most significant pathways from social power to number of surviving offspring, based on the cross-sectional analyses.
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Figure 6-2: How powerful Tacuaral men produce more intra-marital surviving offspring (n=53)1
(1) Better Access To Mates (2) Social Power
Higher Mate Quality (3)
Surviving Offspring
Partners and Allies Status Determinants
(4)
Deference from Competitors (5) (6)
1
Arrows indicate pathways tested; arrows in boldface indicate pathways that maintained significance through both bivariate and multivariate analysis
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Longitudinal analyses over the period 2005-2009 did not strongly corroborate the cross-sectional analyses of the social power-lifetime fitness relationship in Tacuaral. Men more likely to win a dyadic fight in 2005 but not more influential men gained more intra-marital surviving offspring between 2005 and 2009. However, change in either social power measure between 2005 and 2009 did not associate with change in intra-marital surviving offspring. Men more influential in 2005 and to a lesser extent men more likely to win a dyadic fight experienced more extra-marital affairs between 2005 and 2009. I found that men‘s productivity and support from kin do not explain the gains in surviving offspring among physically dominant men. Furthermore, increases in either social power measure between 2005 and 2009 were not stimulated by child dependency in 2005. Status begets more surviving offspring, not the reverse. Age controls in all analyses were justified by the age gradient in fertility between 2005 and 2009: over four-fifths of the new births were to men younger than age 40.
3. Status and lifetime fitness cross-culturally After evaluating the fitness gains to status acquisition in Tacuaral, I compared those results to published data on status and reproductive success from fifteen other foraging and horticultural societies. I focused the meta-analysis on four correlates of social status described in these societies: hunting ability, material capital, success in physical contests, and political influence. The principal results of the meta-analysis are as follows:
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High status men have higher fertility in 86% of cases and more surviving offspring in 75% of cases
Out of 22 cases, only one (Waorani warriors) shows higher status men to have significantly lower fertility
Higher status men have more extra-marital affairs (80% of cases), marry at a younger age (70% of cases), are more likely to be polygynous (60% of cases), have more allies and trading partners (100% of cases), and have more coresident kin (75% of cases)
Higher status men have more serial wives in only 38% of cases, marry or have their first child at younger ages in only 50% of cases, marry more hardworking women in only 33% of cases, and marry women with lower interbirth intervals in only 20% of cases
Higher status men spend more time directly parenting their offspring in only 18% of cases
Higher status men are rarely better direct providers for their families (27% of cases), in part because their generous food-sharing outside of the family is unreciprocated in-kind
4. The Tsimane villages compared In Chapter 5, I evaluated differences in the determinants, inequality, inheritance, and reproductive outcomes of status across four Tsimane communities:
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Munday, Fatima, Jamanchi, and Tacuaral in 2009. I predicted that these differences would track variation in village size and access to material capital. Tacuaral men have the greatest access to material capital, based on average number of visits to town per year, average annual wage income, and average annual horticulture income. Jamanchi also has high average levels of horticultural income, relative to the two upriver communities of Munday and Fatima. Tacuaral and Jamanchi sell approximately 50% of their food production to local markets. While horticultural production is lower upriver, Munday and Fatima men make much more income from the sale of lumber than do men in Tacuaral and Jamanchi. In terms of total income from all sources, Munday and Tacuaral men earn more than men from Fatima, and Jamanchi men earn the least. I predicted that residents of larger villages and villages with more material capital would be less cooperative, due to lower average kin relatedness and reduced reliance on risk-pooling, respectively. While Tacuaral and Jamanchi rank the highest in terms of male-male conflicts per capita, they also have higher levels of inter-family food sharing and men claim greater numbers of allies and field labor partners. Most conflicts in Tacuaral are disputes over land for horticultural purposes, but in Jamanchi, alcohol-related disputes, monetary debts, and theft account for greater shares of all conflicts. Land is also a principal source of conflict in Munday and Fatima despite their lower levels of cash-cropping.
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In each village, I analyzed the relationships between ten different determinants of status and the four status measures. Below, I summarize these results, which are based on bivariate correlations controlling for men‘s age:
The four measures of status competition are inter-correlated in each village, with the exception of fighting ability and respect in the smaller communities
Physical size predicts winning dyadic fights in three of the villages, getting one‘s way in two of the villages, and influence and respect only in Tacuaral
Number of allies is a universal covariate with all four status measures, and ranked skill in resolving interpersonal conflicts predicts influence and respect in each village
The contribution of kin support to influence is not necessarily greater in smaller communities: number of co-resident affinal and consanguineal kin predicts influence in Munday, the smallest village, but also in Tacuaral, the second largest
Education, income, and generosity are more likely to beget influence in the larger communities of Fatima and Tacuaral than in the smaller communities
Traditional skills are not necessarily less conducive to influence in the villages with more material capital; hunting ability predicts influence in Tacuaral and Jamanchi, where men engage in more cash-cropping and in more hunting
Horticultural income does not predict influence in any of the communities
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More modernized men do not necessarily accrue less respect: respected men are more educated in all the villages, have more wage income in Tacuaral, and have more horticultural income in Munday
Only in Tacuaral does hunting ability significantly predict respect; hunting ability and wage income independently predict respect in Tacuaral in 2009
Hunting ability is negatively correlated with wage income in three of the four villages, but not significantly
I found inter-village similarities and differences in the timing of status acquisition across the lifespan:
Dyadic fighting ability peaks in the mid 30s and drops precipitously thereafter in all four villages
The peak age of average intra-village influence tracks the community‘s distance from San Borja: in Munday and Fatima influence peaks in the mid to late 40s while in Jamanchi and Tacuaral influence peaks in the early 40s and late 30s, respectively
In all four villages, men are ranked highest on dyadic fighting ability in early adulthood; by mid-life, men‘s ranking on respect eclipses their rankings on the other status measures
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Across villages, older men are less educated and generate less income, but they are more generous, more skilled in conflict resolution, and have more coresident close kin
Inequality in influence differs across the villages. Community-wide verbal influence is more unequally distributed in Jamanchi and Tacuaral compared to Munday and Fatima. Men with more influence are more likely to arbitrate interpersonal conflicts in all villages, but inequality in conflict arbitration is particularly high in Jamanchi and Tacuaral. In all four villages, a minority of men hire their peers to assist them in horticultural labor. The frequency of these patron-client relationships is highest in Jamanchi and in particular Tacuaral, and it is influential men in these latter two villages, but not in Munday and Fatima, who are most likely to be patrons. I estimated inter-generational inheritance of community-wide influence by comparing the influence of co-resident fathers and sons. I predicted that inheritance of influence would be stronger where access to material capital was greater, but the influence of Fatima men and not Tacuaral men predicted their sons‘ influence. Fighting ability is strongly inherited in both Tacuaral and Fatima. Tacuaral and Jamanchi men with more community-wide influence produced more surviving offspring during the previous decade as well as over their entire reproductive careers to-date. This is not the case in the upriver villages. Of the variables that predict influence in Tacuaral and Jamanchi and not upriver, only wife‘s age at first birth correlates with number of surviving offspring. Furthermore, wife‘s
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age at first birth only partially mediates the effect of Tacuaral and Jamanchi men‘s influence on their number of surviving offspring. In no community is there strong evidence of sons inheriting their fathers‘ reproductive success.
B. Interpretation of the results 1. The multiple dimensions of male social status Among the Tsimane, male status hierarchies are best viewed as multidimensional. I analyzed four measures of male social status: (1) success in dyadic physical confrontation, (2) the ability to get one‘s way in a group, (3) communitywide influence, and (4) respect. These status measures represent distinct social contexts in Tsimane society through which men vie for access to contested resources. While dyadic fighting ability is largely determined by physical size, physical characteristics contribute less to the ability to get one‘s way in a group dispute and minimally if at all to community-wide influence and respect. The latter three status measures arise primarily from social support, both from kin and non-kin. The results from the Tsimane village of Tacuaral suggest male fighting ability is determined more by muscle size and weight than by height. In a study of U.S. college students, flexed bicep circumference predicts lifting strength and self-reported conflict outcomes better than height, weight, or chest circumference (Sell 2005). However, in a study of Indian men, height, weight, and flexed bicep circumference all significantly correlate with aggression, but height and weight produce higher bivariate correlations with aggression than does bicep size (Archer & Thanzami
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2007). Since the cross-correlations among all of these variables are as high in the Indian and U.S. samples above as among the Tsimane, the different results reported by these studies may be more apparent than real. Physical size is not the only means of winning a dyadic fight. Occasionally, disputants will use weapons, such as machetes or shotguns. Approximately 8% of young adult and middle-age male deaths are due to violence (Gurven et al. 2007), principally from weapon-inflicted injuries. Surprisingly, social support also contributes to winning a dyadic fight. In Tacuaral, men with more social support are more likely to win a dyadic fight independent of their physical size. Furthermore, the number of allies who would come to one‘s aid in a conflict is associated with winning dyadic fights in all four villages. My interpretation is that dyadic fighting ability is perceived as indistinguishable from one‘s ability to elicit social support. The downstream consequences of any dyadic fight may involve retaliation by the disputing parties‘ coalitions. For group dispute outcomes, coalitional support is paramount, but physical size still plays an important independent role. Thus, getting one‘s way in a group is a form of social status among Tsimane males that is intermediate between winning a dyadic fight and influence within the context of community-wide meetings. In generating community-wide influence in Tacuaral, physical size has no effect independent of social support. In other villages, physical size has no effect at all on influence. Rather, social support from allies, including both kin and non-kin, is the sine qua non of influence among the Tsimane. In Tacuaral, social support
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mediates much of the effects of skill, material wealth, and generosity on influence, and increases in social support over four years predicted growth in influence during that same period. This is not to say that social power based on dominance is of no consequence at the community level. Men may recruit allies due to prestige, but this social support can in turn function as (derived) dominance. This conclusion is supported by personal observation. I present three sets of dialogue from community meetings in Tacuaral as examples of how alliances shape access to contested resources. I have changed names to hide individuals‘ identities.
a. Tacuaral community meeting, July 19th, 2009 In this dialogue, men‘s alliances become transparent in discussion of who and who cannot sell community lumber.
Rogelio: “If there is a community member that has a problem and there is no solution, like if they have no money, they can sell lumber to pay their debt…For example, Juan told me, „I have a problem concerning sickness. I am going to sell lumber because I have two sick children who need to have operations in Trinidad.‟ In this case, it‟s ok. But there are some people selling lumber who have no kind of problem. That will not do. I said this to Pablo while drunk.” Gerardo: “But it is not correct to say these things while drunk.” Miguel: “Yeah, that is not good.”
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Rogelio: “I don‟t want others to cut trees like he is doing, because he never told me or you anything about why he began cutting trees there. That is wrong, and I don‟t want it.” Pedro: “I told Benicio that those wishing to sell wood must get permission and not take more than what we have censused. If they do not have permission then they should not be selling wood.” Rogelio: “But if someone has a real problem it is alright for him to sell the lumber. If we tell him that he cannot sell the lumber, then we must find at least 50 to 100 bolivianos so that he can cure his son or fix some other problem.” Felipe (aside to Ignacio): “But take me as an example. I was asking for help from the community and they did not want to help me.” Lucio (aside to Felipe): “They will never go and help us; these guys only talk.”
I caught these last two comments because I was sitting near Felipe and Lucio during the meeting. Felipe was ranked 7th in alliance strength in the community while Lucio was ranked 36th. They are clearly not happy with the principal speakers, including the corregidor Rogelio. Rogelio was rated in 2009 as the man with the most allies and influence in Tacuaral. Juan, the man who Rogelio argued should be allowed to sell lumber, is a close ally and brother to Rogelio and was ranked 4th in the community in both influence and support from allies. Lacking a close alliance with these influential community figures, Felipe and Lucio are less likely to receive community-wide support in times of need.
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b. Tacuaral community meeting, July 19th, 2009 This second dialogue transpired later in the same meeting. An influential man in the village admits to accepting a bribe from a non-Tsimane but this does not provoke outrage among meeting attendees.
Emeterio: “That [non-Tsimane] man needs to leave our forest.” Abraham: “This is not good of him.” Emeterio: “He is doing it [cutting lumber]. We don‟t have to give him any time before kicking him out.” David: “But we are the ones at fault, we are allowing him in.” Rogelio: “Listen community members, I am not going to go all by myself to get that man to leave. We all have to go together to force him out.” Miguel: “He left money in your house, Benicio?” Benicio: “He left me 100 bolivianos.” Rogelio: “I don‟t want to go there by myself. We have to go together: men, women, and children, to force him out.” Benicio: “Like the corregidor said, we all have to go there to force him out. We have to take arrows, guns, and other things. That‟s how we are going to do it so that the man will fear us.” Juan: “They all don‟t have to go. Just us who are tired of him [stealing lumber] have to go.”
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Benicio admits to accepting a bribe, but Rogelio steers the conversation in a different direction. Perhaps to soften public opinion against him, Benicio is then quick to voice approval for the growing community sentiment that the man who bribed him must be ousted from Tsimane land. That Benicio was ranked 3rd in alliance strength and influence in the community may help explain why he was not criticized for his abuse of power.
c. Tacuaral community meeting, July 1, 2009 The final dialogue I present illustrates intra-village conflict over land for horticultural purposes and the role of alliances in winning those conflicts.
Miguel: “When I first married my wife, I made my field near here because I want to live with my family. But now my father-in-law lives in this place. So I moved to the place where I am now. I have already cut five hectares out of the forest, where I have a field and a house. Now, others want to use my land, and I don‟t want to fight with my neighbors. They thought that if they planted banana trees I wouldn‟t cross into their field. I just want them to give me 200 meters, that‟s all.” Juan: “I also know that when Miguel moved over there he made his field by that lagoon. I helped him cut down all the trees. The field first belonged to Miguel, not to Julio or Manuel. First it was Miguel‟s.”
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Miguel: “I have already planted where I live now. I have asked Benicio to help me tell other people not to move into the place where I now live. Let them look somewhere else, in another part of the forest.” Juan: “As Miguel said, where we now have our fields others should not plant. Go over and look at it all so you will know. Because we can‟t live anywhere else.” Benicio: “The soil needs us now; we must begin to work because our families will be hungry. The soil does not grow without us. We need it to survive.”
Benicio‘s use of platitude may or may not have fooled others into believing he is concerned for the welfare of all community members rather than principally that of his allies. Both Benicio and Juan are allies of Miguel and are in support of his claim to disputed land. In Tacuaral, Benicio and Juan are ranked 3rd and 4th in alliance strength, respectively, while the men who contest Miguel‘s land claim are ranked 25th and 31st in alliance strength. No one voices support for their cause in the meeting.
The above dialogues and the statistical analyses of previous chapters reveal the central importance of allies to men‘s community-wide influence. Certain men acquire more allies than other men because they have more locally-residing kin, they possess skills others hope to learn, they are sources of food or money, they offer leadership during collective actions, or they provide valued knowledge. In addition, membership in the coalition of powerful men may increase one‘s attractiveness to
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potential mates and one‘s formidability relative to enemies. In Tacuaral in 2005, the strongest determinant of social support, and in particular one‘s number of allies, was men‘s level of modernization. Tacuaral men with more income may acquire allies due to generous money-lending, though the positive effect of income on money-lending was significant only in 2009. Furthermore, men‘s pro-sociality (including their degree of food-sharing and money-lending) contributes to their social support independent of their relative modernization (see Table 3-5). Tacuaral men with more income or education acquire allies through some means other than generosity. Relative to residents of Munday and Fatima, Tacuaral and Jamanchi men more frequently hire their peers as horticultural laborers, and they have on average a greater number of intra-village allies. Tacuaral and Jamanchi men with higher income may acquire allies by acting as patrons. Furthermore, the higher frequency of patronclient relationships in Tacuaral and Jamanchi may be exacerbating the steepness of status hierarchies. Only in Tacuaral and Jamanchi are more influential men the most likely to hire their co-residents as laborers, and support from allies and influence is more unequally distributed relative to the upriver villages. The influence of more modernized Tacuaral men is not just due to social support from allies, whether kin or non-kin. Independent of their level of social support, men‘s relative modernization in 2005 predicts their influence that year and also their relative change in influence four years later. Skills gained through formal education and wage labor are of increasing importance to community-wide influence because they provide access to knowledge germane to participation in community-
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wide debates. Market-related skills also favor men as leaders in coordinating projects with outside political bodies, as is frequent in Tacuaral. Differences in time-discounting among Tsimane males may determine who reaps more wealth and influence later in life. In a recent study of the Tsimane, more patient individuals reported more years of schooling, and four years later they had earned greater wage labor income (Reyes-Garcia et al. 2007). The negative relationship I found between ranked hunting ability and wage labor income, though only significant in Tacuaral, suggests Tsimane men segregate into different occupational pursuits. While data from the Hadza show that archery skills do not trade off with time spent in school (Blurton Jones & Marlowe 2002), there is a big difference between accuracy in archery shooting and success in hunting, which the authors note. In Tacuaral, the pursuit of material capital via education and wage labor is more likely to generate influence than respect while the cultivation of traditional skills such as hunting ability is more likely to beget respect than influence. The material capital of the nouveau riche may be seen as a less legitimate avenue to social power while the allocation of respect remains rather conservative. Anecdotal reports of what it means to be a ―good man‖ in Tsimane society support my interpretation that traditional skills in food production are seen as a more legitimate means of achieving status. Consider the following, told to me in 2009 by Felipe Mayer, the current head of the Tsimane Grand Council:
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―To be considered a good man, one must know how to work in the field, chop down trees, hunt, fish, and make arrows. If a man wants to marry or find a woman, first he must demonstrate that he will be able to take care of his family. The community knows when a man is good or is lazy.‖
However, I do not find the same distinction between respect and influence in other Tsimane communities. Education and income are not associated with influence in Jamanchi, and hunting ability is significantly associated with respect only in Tacuaral. Furthermore, hunting ability and wage labor income are nearly equally independent contributors to respect in Tacuaral in 2009, which was not the case in 2005. I suspect that the division between influence and respect in Tacuaral is due to the confluence of two factors: (1) the higher contribution of hunted game to the diet (relative to the upriver communities), and (2) the higher levels of wage and horticultural income opportunities in the community, which have mostly benefited younger men. Old age is not a guarantor of social status among the Tsimane. Given the senescence of physical size with age, the relative lack of dyadic fighting ability among older men is unsurprising. The decline or stasis in getting one‘s way in a group, community-wide influence, and respect after age 40 differs from reports of deference towards elderly men in other small-scale societies (Silverman & Maxwell 1978; Simmons 1945). However, the Tsimane results are perhaps not uncommon for
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a rapidly modernizing small-scale society where the elite ritual knowledge of older men has decreased in value. Furthermore, the lack of influence among Tacuaral males older than age fifty is in large part a cohort effect due to their limited exposure to public education and market-based knowledge. Income opportunities and the ability to purchase prestigious, foreign items (e.g. watches and radios) have shifted the basis of power from folk knowledge to market acumen. This transition is evident in the comparison of villages on age of peak influence. Community-wide influence peaks at earlier ages in the villages closest to San Borja, where wage and horticultural income opportunities are highest. In any society, rapid institutional change translates into reduced status for the elderly (Maxwell & Silverman 1970). Respect shows the least decline with old age across the Tsimane villages. Despite their loss of influence, the oldest men in Tsimane villages may retain respect due to three significant assets: meat-sharing generosity, wisdom in resolving interpersonal problems, and a relatively greater number of co-resident kin. Men may also acquire respect just for having survived to late age. Since hunting ability is a strong predictor of respect in Tacuaral, senescence in the former may, in part, explain senescence in the latter. Men older than fifty are still contributing significant amounts of food to their households, but their hunting performance is decreased relative to men in their thirties and forties (Gurven et al. 2006). Social status may be multi-dimensional, but a few Tsimane men rank the highest in most predictors of status and all four manifestations of status competition. It is to the advantage of individuals to excel in many of the status determinants,
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thereby increasing the scope of their social power (both dominance and prestige) and precluding others from gaining ascendancy in a new status niche. Phenotypic correlations (e.g. better nutrition, health, and general intelligence among higher status men) may underlie the lack of social niche specialization among the Tsimane. Because the predictors of the status measures tend to concentrate in the same people, traits correlated with status lose significance in my statistical models. In other published studies of social status, bivariate relationships may likewise not hold up to multivariate analysis. For example, the relationship between height and leadership in most societies (Ellis 1994; Judge & Cable 2004; Stogdill 1948) may be largely attributable to intelligence or task-specific skills (Case & Paxson 2006; Lindqvist 2010). Concentration of status-conferring traits in the same men is not unique to the Tsimane. In many Amazonian societies, the headman is also the shaman, as among the Tapirape (Wagley 1977). In Brazil, Mekranoti men with more political influence are not only more likely to be shamans but also song-leaders, good hunters, good craftsmen, and good warriors (Werner 1981). Among the Kapauku of highland New Guinea, headmen are wealthy, generous, eloquent, physically fit, and brave in war (Pospisil 1963). Leaders of modern nation-states are likewise superlative in multiple status-relevant traits. Successful U.S. presidential candidates are almost by definition eloquent and wealthy, and they tend to be more intelligent (Simonton 2006) and taller than the average U.S. male (Persico et al. 2004). The advantage of large stature in
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modern electoral politics suggests leadership preferences have changed little over human history. That only a few men excel in each of the dimensions of status, in the Tsimane and in other small-scale societies, is not strongly supportive of Fried‘s description of status hierarchies in egalitarian societies. There may be ―as many positions of prestige in any given age-sex grade as there are persons capable of filling them‖ (Fried 1967, pp. 33), but the number of such persons is rather low when the best hunter is also the best warrior and the best orator. Furthermore, the high levels of inequality in community-wide influence and conflict arbitration among the Tsimane are surprising for a society lacking formal authority. Collective decision-making is still, in the end, consensual, but a minority of individuals wields disproportionate influence over that process. Even in the two remote, upriver villages, inequality in influence and arbitration of conflicts is substantial. While the Tsimane may tolerate more inequality in informal political influence compared to other small-scale societies, especially purely foraging societies, even the archetypal !Kung permit certain individuals a larger role in collective decision-making (Shostak 1981; Wiessner 2002a). The conventional notion of status equality among adult men in so-called egalitarian societies is not correct. As described in Chapter 2, I included one woman in my analyses of social status: Rogelia Caiti from Munday. Given her renown in upriver communities, it is unsurprising that Rogelia ranked 5th in community-wide influence and respect amongst the eighteen adult men in her village. Tsimane women are capable of
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navigating and mastering male-dominated village politics but few, as of yet, do so as publically as Rogelia. I hope this dissertation catalyzes more multivariate analyses of the determinants of political inequality in foragers and horticulturalists, before they assimilate fully into the capitalist economies that surround them. Better understanding of human social motivation in the context of rapid modernization is both timely and important as traditional societies everywhere are increasingly exposed to the forces of globalization.
2. Why do men seek high status? Across human societies, men expend tremendous time and energy building and displaying social power, whether in the form of dominance or prestige. With relatively greater social power, individuals reap greater social status, including better access to mates, the support of allies, and deference from competitors. Inequality in these proximate rewards is likely to cause differentials in lifetime fitness, whether consciously intended or not. Higher status men have greater reproductive success, whether in the more egalitarian of human societies (see Table 4-4a), the oligarchies of human history (Betzig 1986), or even in post-demographic transition, industrialized societies (Fieder & Huber 2007; Hopcroft 2006; Nettle & Pollett 2008; Weeden et al. 2006). However, the mechanisms by which socially powerful men reap lifetime fitness benefits are not well studied, at least in small-scale societies. Whether men seek status to improve the fertility of their wives and health of their children or rather
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to acquire more sexual partners bears significance for debates about the evolution of human pair-bonding and male parental investment. The data I present from the Tsimane represents the most complete picture in any small-scale society of the pathways from social power to fitness outcomes. The results suggest that men are motivated to pursue status because of fitness gains both within and outside of marital unions. For the village of Tacuaral, at least, dominant and prestigious men achieve greater numbers of surviving offspring within their marital unions and they also experience more extra-marital affairs. Tacuaral men who are more likely to win dyadic fights are significantly older than the women they marry. Their wives are also rated as more attractive than other men‘s wives. However, neither of these factors is strongly tied to Tsimane men‘s number of surviving offspring. Few studies of status and fertility in small-scale societies report the age differences of spouses, but in the historical Sami of Finland, marital fitness was maximized by older, wealthier men marrying women at least 1015 years younger (Helle et al. 2008). Absolute age at marriage or first birth for either spouse is more commonly reported in studies of status and fertility, and their effects on the fitness of high status men across small-scale societies are mixed. In Tacuaral, influential men have more surviving offspring in part because they marry at earlier ages to women with earlier ages at first birth. A wife‘s first pregnancy usually follows a year or two after marriage, so later first births by wives of low-prestige men are due more to late marriages than longer waiting-time to first birth. Physically dominant men do not
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marry at earlier ages or to absolutely younger women. Even though physical dominance peaks a decade or more earlier than does community-wide influence, it may be that young men‘s future gains in community-wide influence are highly predictable based on their skills, prosociality, and social support as adolescents. The strong relationship between men‘s marriage age and their status at some point later in their lives suggests that, relative to his age mates, a man‘s status is fairly constant across the lifespan. Even in the absence of age controls, men‘s relative status changed little between 2005 and 2009 in Tacuaral. Controlling for the numbers of consumers and producers within families, wives of socially powerful Tsimane men neither spend more time in food production nor produce more calories per day than other men‘s wives. These results contrast with data from the Hadza (Hawkes et al. 2001), where the effects of male productivity and status on intra-marital fertility were mediated by wife‘s productivity. In general, Tsimane women who spend more time in food production have more surviving offspring, controlling for the number of consumers and producers within families. The wives of socially powerful men may not have to increase their productivity to reap higher reproductive gains because their husbands are better hunters, earn more income, and receive more social support from allies, both kin and non-kin. Wives might have better support networks themselves; high status Tacuaral men have more affinal as well as more consanguineal kin. Community-wide influence, largely isomorphic with number of allies, contributes to Tsimane men‘s number of surviving offspring independent of wife‘s
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age at first birth. The dialogues illustrated that vocal support from allies is a principal means by which influential men swing community opinion in their favor. When disputes over land access for horticulture are aired during community meetings, the collectively-agreed terms of their resolution often favor high status men‘s families. Men with community-wide influence are more generous and garner more social support than physically dominant men, but both forms of social power associate with frequent visitation by peers, greater number of allies, and more labor partners. Within one‘s social group, individuals make decisions concerning how much of their resources to share and with how many others (Gurven 2004). Sharing decisions which optimize food consumption via reciprocal altruism may trade off with sharing decisions which optimize status acquisition via alliance formation. Influential Tacuaral men are rated as more generous meat-sharers, but they do not have more food-sharing partners nor do their families receive more calories per day from other households. Physically dominant men receive fewer calories per day from other households while some of the oldest, lowest producing men receive the most calories per day. Households where infants experience higher mortality rates receive food more frequently than other households. On the other hand, socially powerful Tacuaral men are more likely than their co-residents to receive aid from non-relatives in times of food shortfalls. Since they tend to be better hunters, farmers, or wage earners, socially powerful men do not share out of short-term need. Rather, they share to build alliances in the face of inter-household conflicts and to accrue insurance against infrequent misfortune.
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In other small-scale societies, generous food-sharing or greater contribution to collective food production by higher status men is also not reciprocated in-kind (Meriam: Smith et al. 2003; Achuar: Patton 2005; forest Ache: Kaplan & Hill 1985b; Martu: Bird & Bliege Bird 2010; Lamalera: Alvard & Gillespie 2004). As among the Tsimane, socially powerful men share food in these societies to receive benefits in alternative currencies that often pay-out only in the long-term. Investments in social power may be motivated in large part as insurance against infrequent famine, sickness, or conflict (Boone 1998). Generous Achuar men benefit from stronger political alliances during intra-village conflicts (Patton 2005). Magnanimous Martu hunters are more likely to acquire ritual power as older men (Bird & Bliege Bird 2010), and generous Ache hunters are more likely to be provisioned when sick (Gurven et al. 2000). Better !Kung hunters have more hxaro exchange partners (Wiessner 2002a), who are long-term sources of not only food but also mates and political support. My analysis of small-scale societies, including the Tsimane, suggests that socially powerful men are not in general better parents or even better direct providers for their offspring. On the other hand, their prestige pays dividends for their families in the long-run. Exchange between higher and lower status men does not always involve a bidirectional flow of benefits. Among the Tsimane, men more likely to win a dyadic fight and men with more influence receive more deference from competitors, who may be ceding to their socially powerful peers simply to avoid the costs of contest competition. While getting one‘s way appears to be the strongest pathway from
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physical dominance to fitness gains, fighting ability produces more surviving offspring in large part because the most dominant Tacuaral men are also the most influential. Most studies of status and reproductive success do not test for confounding variables. For example, men‘s productivity may independently generate more offspring and more social power. High status Tsimane men in Tacuaral tend to be more productive and draw on a larger intra-village consanguineal kin network, but these variables alone do not produce the fitness gains of high status men. Furthermore, better hunting ability and more numerous consanguineal kin increase a man‘s total surviving offspring in part because of their effects on his social power. Wealth and skill attract mates and others‘ allegiance and deference, important determinants of men‘s reproductive success. Furthermore, potential mates and allies may use social status as a heuristic for ascertaining men‘s skill and wealth. Hunting ability, for example, is not easily identified by co-residents based on return rates (Hill & Kintigh 2009). Some forms of production important to fitness may not lend themselves to social status gains, perhaps because they are less skill-intensive or are subject to less variance over time (Bliege-Bird et al. 2001). Income from sales of horticultural goods predicted number of Tacuaral men‘s offspring surviving to maturity independent of social status. Longitudinal analyses in Tacuaral show men who gain in fighting ability but not men who gain in influence produce more surviving offspring, relative to their age,
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between 2005 and 2009. This appears to contradict the cross-sectional results, in which the effects of fighting ability on reproductive success were fully mediated by influence. However, half of all births over those four years were to men in their 20s, whose average gains in influence were lower than their average gains in fighting ability (see Figure 3-4). Furthermore, men‘s social power did not change substantially between 2005 and 2009 (see Table 3-7). Four years may be too short a window in which to document the effect of change in social power on change in fertility and surviving offspring. In the coming years, I plan to return to Tacuaral to extend the longitudinal results. With the Tsimane, I am also able to discredit current offspring dependency as a principal motivator of status acquisition. Both the cross-sectional and longitudinal analyses indicate that social power begets more surviving offspring more than the reverse. While socially powerful Jamanchi and Tacuaral men produce more surviving offspring for their age, their counterparts in Munday and Fatima do not. I suspect that such intra-societal variation is also characteristic of the other foragers and horticulturalists where a positive relationship between status and reproductive success was reported (Table 4-4a). Influential men in Jamanchi and Tacuaral are more likely to be better hunters, they arbitrate a greater share of inter-personal conflicts, and they hire more co-residents to assist them in horticultural labor. However, these variables do not explain the fitness gains of Jamanchi and Tacuaral men with influence. On the other hand, influential men in Jamanchi and Tacuaral marry wives with earlier ages at
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first birth, and this is not the case in Munday and Fatima. In addition, influence and support from allies are more unequally distributed in Jamanchi and Tacuaral, suggesting influential men in these communities are more likely to resolve conflicts in their favor relative to influential men in Munday and Fatima. Compared to Fatima, there is greater inter-family food-sharing and more frequent sharing of field labor in Jamanchi and Tacuaral, although in 2005 I did not find that the families of influential Tacuaral men disproportionately benefited from average daily food transfers. Influential Tacuaral men have more allies and labor partners, but only number of allies predicts men‘s number of surviving offspring. Another study of the Tsimane (Godoy et al. 2007) found that gifts of labor and food constitute a higher percentage of ―income‖ for Tsimane households in the top quintile of wealth (5.51%) than for those in the bottom quintile (2.98%). And gifts of labor and food constitute a higher percentage of ―income‖ in villages close to San Borja (4.82%) than further away (2.50%). Our results are at odds with the notion that greater access to material capital causes individuals in traditional societies to invest more in private wealth than in social support (Fafchamps 1992; Rosenzweig 1988). However, investments in social support may not be motivated by risk-reduction per se. In only 11.66% of episodes of misfortune do Tsimane households rely on unrelated individuals for help (Godoy et al. 2007). I found that only a handful of men (those with higher status) received support from non-relatives in addition to kin when they were sick or lost a percentage of their crops. When villages integrate more into the
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market economy, individuals may offer food, labor, and alliance to others for political gain more than for reducing the risks of food under-production. Among the Tsimane, inequality of social power and the translation of social power differentials into fitness gains may be exacerbated by greater market integration. Jamanchi and Tacuaral are closely located to San Borja, which facilitates the transportation and sale of horticultural products. As a result, Jamanchi and Tacuaral invest more heavily in cash-cropping, selling close to 50% of their horticultural production. However, horticultural income does not predict influence in any of the villages. This may be due to its lower variance across individuals compared to wage income, as I found in Tacuaral. While wage income is a determinant of influence in Tacuaral, wage income in Jamanchi is relatively low and does not predict men‘s influence. Furthermore, men in Munday and Fatima earn significantly more from sales of lumber, and Munday men earn as much total income on average as Tacuaral men. Access to material capital can only be a partial explanation for why social power is more unequally distributed in Jamanchi and Tacuaral, or why socially powerful men in those communities, but not in Munday or Fatima, marry wives with earlier ages at first birth and produce more surviving offspring. The steeper status hierarchies of Tacuaral and Jamanchi may be due not to greater access to material capital per se but rather to the translation of material capital into influence over others labor. Tacuaral and Jamanchi men employ their peers more frequently in horticultural labor, and it is the influential men who are most likely to be
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the patrons. Munday men may make as much income as Tacuaral men, but they lack the incentive to increase capitalization of horticultural or other production given their distance from markets. Likewise, the political complexity in foragers from the Northwest Coast was not due to the greater abundance of material capital per se (e.g. salmon) but to elites‘ coordination of others labor in the production of surplus food (Hayden 1995). In Tacuaral, proximity to San Borja has also exposed village residents to more NGO and government investment. More coordinative leadership is demanded of influential men in order to negotiate the village‘s interests with outside political or charity organizations. Village residents may be willing to allocate greater status to men with the market-related skills conducive to such leadership. Across the globe, traditional societies have shifted toward more prominent political leadership in response to the demands of coordinating with the outside world (Lee & Daly 1999). Settlement density may also explain some of the village differences in the inequality and reproductive outcomes of status acquisition. In Fatima, settlement density is quite low (see Table 2-1). Influential men in Fatima have more allies, but their alliances do not beget greater reproductive success. Mobilization of allies in times of conflict may be more difficult when your allies live an hour or two distant by foot. Jamanchi families live at high density, which facilitates their relatively high levels of food and labor sharing. However, Tacuaral men maintained relatively high levels of cooperation despite internal migration between 2005 and 2009 that drastically reduced settlement density.
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In addition to settlement density, I suspect that social dynamics internal to Fatima contribute to the greater equality of social power in the village and the absence of a relationship between influence and lifetime fitness. In Fatima, factionalism among different extended families within the community leads to frequent argument during community meetings. Allies extend not much farther than close kin. This has likely been the case for several decades. Father Martin was the glue that kept the large number of families living in Fatima amiable; after his death, families bickered and spread their homes further apart. Currently, residents who live upriver of the mission want to separate from those living downriver. The corregidor they supported was ousted in 2009 after only a month in office. Another segment of Fatima now professes Protestantism and already acts effectively as a separate community. Across Tsimane villages, individuals are able to predict the modal level of cooperation of their co-residents in the context of economic games. Furthermore, these norms of cooperative behavior do not remain stable in the same village over time (Gurven et al. 2008). Such historically-contingent social dynamics likely contribute to the inequality and outcomes of intra-village status hierarchies as well. The greater strength of the relationship between status and fertility in the villages closest to San Borja suggests that the Tsimane are not yet experiencing a demographic transition to lower fertility. In developing economies undergoing a demographic transition, the wealthy are usually the first to adopt lower fertility (Borgerhoff Mulder 1998). Childhood mortality is higher in more remote Tsimane villages (Gurven et al. 2007), but fertility has not dropped substantially in more
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modernized villages close to town, despite their greater access to education, material capital, and non-indigenous cultural norms (McAllister et al. n.d.). In coming years, I hope to expand the number of Tsimane communities in which I compare social power to lifetime fitness. A larger sample of villages will help to better untangle the relationships between market integration, social power, and men‘s reproductive success.
3. Natural selection of male status-seeking behavior Since humans have lived in small-scale societies for the majority of their existence, reproductive data in these societies can help elucidate the selective forces that have shaped how men acquire social status. Higher male status is associated with fitness gains within pair-bonds, in the Tsimane of Tacuaral and in other small-scale societies. Physically dominant and prestigious Tacuaral men have more extra-marital affairs, but these are in addition to the fitness gains they realize within their marital unions. Also, socially powerful men‘s intra-marital fitness gains were not driven by serial marriages. Tsimane men tend to invest in a single wife their entire reproductive careers. These data suggest that men do not acquire status simply to increase their number of mates. Status-conferring traits must be genetically heritable to be subject to natural selection. I find that the sons of physically dominant Tsimane men tend to be physically dominant themselves, and, in Fatima, the sons of influential men are also influential. However, I do not determine the source of such inheritance, whether
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shared genes, shared environment, or cultural transmission of information or material capital. In other small-scale societies, there is evidence that high status men achieve higher reproductive success because they capitalize on their father‘s status during their own reproductive years. Among the Martu of Australia, for example, co-resident fathers enable their adolescent sons to achieve earlier initiation, which results in higher lifetime reproductive success (Scelza 2010). The sons of Mekranoti headmen, who have higher reproductive success than their peers, inherit their fathers‘ influence due largely to inheritance of privileged relationships with traders, missionaries, anthropologists, and government officials (Werner 1982). Among the Tsimane, I do not find evidence that sons inherit the reproductive success of their fathers. Fathers with more social power do no better in transmitting their reproductive success to their sons. The strongest social power-fitness relationship I identify is among influential Tacuaral men, but it is the sons of physically dominant rather than influential Tacuaral men who are more likely to transmit their social power to their offspring. More accurate tests of inheritance would measure fathers and sons at the same age. Men who ultimately achieve the most influence in their communities may not be so ranked at earlier ages, relative to their same-age peers. Furthermore, the relative modernization of Tacuaral has decreased the influence of older men, so the lack of inheritance of community-wide influence in Tacuaral could be largely a cohort effect. My use of age controls in testing the inheritance of social power does not fully eliminate this confound.
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In genetic studies of Y chromosome haplotype variation, evidence for longterm, positive selection on heritable male traits is mixed. Among Indonesian foragers, horticulturalists, and agriculturalists, high fertility along patrilines rarely persists for more than a few generations (Lansing et al. 2008). On the other hand, 8% of Asian men living between the Pacific Ocean and the Caspian Sea can trace their Y chromosome to Genghis Khan and his relatives (Zerjal et al. 2003). Most heritable genetic variation particular to status achievement will be associated with autosomal genes and not the few non-recombining genes on the Y chromosome. Even among autosomal genes we may not expect to see a clear signature of positive selection on heritable male traits: the genotypes of high status men may represent a fitness peak which mutation and sexual recombination will break down in successive generations; balancing selection may prevent the traits of high status men from sweeping across a population; or status achievement may arise from conditional behavioral responses to uncorrelated genetic variation (Smith 2011; Tooby & Cosmides 1990), such as extraversion increasing in response to muscle development. These possibilities may explain why men vary at all in traits related to status acquisition. If positive selection for status-conferring traits was consistent along lineages throughout recent human evolution, we might expect less variance in such traits compared to their currently observed distribution within populations. A limitation of this dissertation is my inability to distinguish endowment from motivation in generating differences in men‘s status-related fitness gains. Certain men may be of lower status not because they lack the motivation to be stronger, wealthier,
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more skilled, or more generous than their peers, but because they were less fortunate in their genetic and cultural inheritance. For example, better hunters may be more intrinsically coordinated or intelligent, or they may have received better instruction in hunting techniques from their older family members. I suspect that desire for high status is universal, but inter-individual differences in endowment prevent some men from realizing that desire or dissuade men from pursuing high status at all. The lifetime fitness benefits that accrue to high status men reflect the synergism of motivation for higher relative social position with phenotypes locally favorable to status acquisition. Given the relative ubiquity of the status-lifetime fitness relationship across human societies, a desire for higher relative social position has probably been favored by selection throughout human evolutionary history,
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Appendix A: Instructions and questions presented to photo-raters
Thank you for participating in my project about the men in this community. My questions will last an hour, and I hope they will be interesting to you. I am not going to show your responses to anyone else. Your specific responses are confidential. Ok?
First I am going to show you x photos [15 in Tacuaral in 2005; 17 in Fatima; 11 in Jamanchi; 18 in Munday; 17 in Tacuaral in 2009]. There is one man in each photo. I am going to read thirteen descriptions, one at a time, about these men. For each photo, if you are in agreement with the description, say ―yes‖. If you are not in agreement, say ―no‖. For example, here is a photo of me. Listen to the following description about this photo and respond with ―yes‖ or ―no‖: He is from another country.
Do you have questions? Here are the photos for you to evaluate. Say ―yes‖ or ―no‖ to the following descriptions.
1. He knows how to keep promises 2. Many people in the community like to visit him 3. He gets angry easily with others 4. He shares meat generously with others 5. He is a good hunter compared to other men
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6. You can trust this man 7. His wife frequently makes chicha for others in the village 8. If you have a problem, you would go to him for advice 9. His wife is very attractive 10. He knows how to resolve conflicts in the community [not asked in Tacuaral in 2005] 11. In an emergency, you could borrow 50 bolivianos from him 12. He is funny 13. He works a lot; he is a hard-worker
Now I am going to give you x photographs [8 in Tacuaral in 2005; 9 in Fatima; 6 in Jamanchi; 18 in Munday; 9 in Tacuaral in 2009]. Order these photos according to the description I will read. I want the photographs ordered in x different positions. The man most similar to the description should be on the furthest right and on his immediate left the photo slightly less similar to the description and so on for the whole set of photos. On the furthest left should be the photo least similar to the description among these photos. Do you have questions?
Here are the x photos. Now, listen to the following description:
1. This man is respected
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Are you ok with how you organized the x photos? This photo is most similar to the description [I point to the right-most photo]? And this photo is least similar to the description [I point to the left-most photo]? Ok, there are five more descriptions to read. With each description, you will have x new photos to order. Order them in the same manner as before. Ready? Listen to the following descriptions:
2. When this man is with a group of people and is upset with something, it is likely that he will get what he wants 3. When there is a dispute in which this man is in conflict with another man, this man will have more people who will defend or help him in the conflict 4. This man knows how to organize people to lead community projects [not asked in Tacuaral in 2005] 5. When there is a dispute in the community, what this man says carries more influence 6. This man will win a physical fight against another man because he is strong
That is the last description for you to evaluate. Thank you for your time.
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Appendix B: Instructions and questions from the economic and social network interviews
Thank you for participating in my project about the men of your community. My questions today are about your work and will last an hour. I am not going to show your responses to anyone. Your specific responses are confidential. Ok? Please answer the following questions to the best of your knowledge. Let me know if you do not wish to respond to a particular question.
1. In the past year, how many times did you visit San Borja or [asked of Munday and Fatima residents only] Puerto Yucumo? 2. How many years of school did you complete? 3. Do you speak Spanish? No, a little, or well? 4. How many palm-leaf roofing panes did you sell this year? 5. How many arrobas of rice did you sell this year? 6. How many racimos of banana did you sell this year? 7. How many arrobas of corn did you sell this year? 8. How many arrobas of manioc did you sell this year? 9. How many chickens do you have? 10. How many pigs do you have? 11. How many days did you work for loggers this year? What was your wage? 12. How much money did you make selling your lumber this year?
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13. How many days did you work for non-Tsimane ranchers or farmers this year? What was your wage? 14. How many days did you work for money in other Tsimane men‘s fields this year? What was your wage? Who employed you?
Now I‘d like to ask you about your social relationships with other men. List all the men in the community who fit the following descriptions.
1. Which men in the community live with you? 2. Which men in the community help you in your fields? 3. Which men in the community share food with you? 4. Which men in the community go fishing with you? Who usually has the idea to go fishing? 5. Which men in the community go hunting with you? Who usually has the idea to go hunting? 6. Which men in the community do you collaborate in selling lumber? Who usually has the idea to sell lumber? 7. Which men in the community help or defend you in a conflict with others? 8. If you have a problem, to which men do you go for advice? 9. With which men have you had conflicts? Why were you in conflict? Who intervened in the conflicts to help resolve them?
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