Menopause is an evolutionary mystery: how could living longer with no capacity to reproduce possibly be advantageous? Several explanations have been offered for why female humans, unlike our closest primate relatives, have such an extensive post-reproductive lifespan. Proponents of the so-called “grandmother hypothesis” suggest that older women are able to increase their fitness by helping to care for their grandchildren as allomothers. This paper first distinguishes the grandmother hypothesis from several other hypotheses that attempt to explain menopause, and then develops (...) a formal model by which these hypotheses can be compared and tested by empirical researchers. The model is then modified and used to respond to a common objection to the grandmother hypothesis: that human fathers, rather than grandmothers, are better suited to be allomothers due to their physical strength and a high incentive to invest in their own children. However, fathers—unlike maternal grandmothers—can never be sure that the children they are caring for are their own. Incorporating paternity uncertainty into the model demonstrates the conditions under which the grandmother hypothesis is more plausible than a hypothesis that focuses on the contributions of men. (shrink)

Gender differences in dishonesty and mistrust have been reported across cultures and linked to stereotypes about females being more trustworthy and trusting. Here we focus on fundamental issues of trust-based communication that may be affected by gender: the decisions whether to honestly deliver private information and whether to trust that this delivered information is honest. Using laboratory experiments that model trust-based strategic communication and response, we examined the relationship between gender, gender stereotypes, and gender discriminative lies and challenges. Drawing from (...) a student sample, we presented males and females with incentivized stereotype elicitation tasks that reveal their expectations of lies and challenges from each gender, followed by a series of strategic communication interactions within and between genders. Before interacting, both genders stereotyped females as more trustworthy and more trusting than males, in accord with cross-cultural gender differences. In best response to these stereotypes, both genders discriminately accepted or challenged messages based on the sender’s gender. However, we find no differences between males’ and females’ overall rates of lies and challenges. After learning the results of their strategic interactions, males and females revised their stereotypes about lies and challenges expected of each gender; these stereotype revisions resulted in greater predictive accuracy and less disparate gender discrimination. This suggests an important facultative feature of human trust-based communication and gender stereotyping: while the delivery and trust of private information is informed by gender stereotypes, these stereotypes are recalibrated with experience. (shrink)

According to cultural evolutionary theory in the tradition of Boyd and Richerson, cultural evolution is driven by individuals' learning biases, natural selection, and random forces. Learning biases lead people to preferentially acquire cultural variants with certain contents or in certain contexts. Natural selection favors individuals or groups with fitness-promoting variants. Durham (1991) argued that Boyd and Richerson's approach is based on a "radical individualism" that fails to recognize that cultural variants are often "imposed" on people regardless of their individual decisions. (...) Fracchia and Lewontin (2005) raised a similar challenge, suggesting that the success of a variant is often determined by the degree of power backing it. With power, a ruler can impose beliefs or practices on a whole population by diktat, rendering all of the forces represented in cultural evolutionary models irrelevant. It is argued here, based on work by Boehm (1999, 2012), that, from at least the time of the early Middle Paleolithic, human bands were controlled by powerful coalitions of the majority that deliberately guided the development of moral norms to promote the common good. Cultural evolutionary models of the evolution of morality have been based on false premises. However, Durham (1991) and Fracchia and Lewontin's (2005) challenge does not undermine cultural evolutionary modeling in nonmoral domains. (shrink)

This thesis focuses on the evolution of human social norm psychology. More precisely, I want to show how the emergence of our distinctive capacity to follow social norms and make social normative judgments is connected to the lineage explanation of our capacity to form shared intentions, and how such capacity is related to a diverse cluster of prototypical moral judgments. I argue that in explaining the evolution of this form of normative cognition we also require an understanding of the developmental (...) trajectory of this capacity. For this purpose, the thesis is organized as follow. In the first chapter, I make some methodological remarks and provide the general overview and plan for the dissertation. In the second chapter, I explain what my explanatory target is and why it matters. On the view I am defending, shared intentional psychology gives rise to a special form of psychology that enables us to engage in social normative thinking. These norms are represented as shared intentional states. Moral psychology, in contrast, is more diverse. For moral judgments define a quite heterogeneous class of mental states—although some moral judgments may involve the representation and execution of norms, certainly not all of them do. I show that although much of our distinctive social norm psychology can be explained within the framework of shared intentionality, moral judgments cannot be unified in the same way. In the third chapter, I provide the baseline of social-cognitive capacities that serve as starting point for my lineage explanation. I argue that hominin social cognition was for a very long period of our evolutionary history essentially a matter of low-level cognitive and motivational processes. On this picture, bottom-up affective processes regulated the social lives of early hominins without requiring any special top-down mechanism of normative thinking such as a capacity for understanding and representing social norms. In the fourth chapter, I argue that human-like social norm psychology evolved as a result of the selective pressures that gave rise to shared intentionality, especially the demands that came from collective hunting. Yet collective hunting was not the whole story of the evolution of shared intentionality, for our capacity to form shared intentional mental states emerged from the interplay between the selective pressures that led to cooperative breeding in humans as well as organized, goal-oriented, collective hunting. Thus, I propose an evo-devo account of shared intentionality and its normative dimension since I argue that explaining the evolution of this particular form of normative thinking crucially depends on information about the developmental trajectory of this capacity. Finally, in the fifth chapter, I focus on how social norms are acquired and how the way we learn them gives rise to some prototypical cluster of moral judgments. Thus, this chapter returns to some of themes and arguments of the first chapter by explaining how the distinction between moral judgments and nonmoral judgments can be culturally transmitted. (shrink)

In “Out of Eden” David Barash argues that humans are naturally polygamous, in that they have innate polygamous preferences. In particular, Barash argues that human males have preferences and other psychological states designed to support aggressive polygynous sexual competition, and that the resulting behavior has driven the selection of various other psychological and behavioral traits in humans. This is controversial, since the prevailing view of the human mating system in our recent evolutionary history was that it was choice-based and only (...) mildly polygynous. In this review I evaluate Barash’s arguments and conclude that he has not made his case for the stronger view. (shrink)

We use data collected among Hadza hunter-gatherers between 2005 and 2009 to examine hypotheses about the causes and consequences of men’s foraging and food sharing. We find that Hadza men foraged for a range of food types, including fruit, honey, small animals, and large game. Large game were shared not like common goods, but in ways that significantly advantaged producers’ households. Food sharing and consumption data show that men channeled the foods they produced to their wives, children, and their consanguineal (...) and affinal kin living in other households. On average, single men brought food to camp on 28% of days, married men without children at home on 31% of days, and married men with children at home on 42% of days. Married men brought fruit, the least widely shared resource, to camp significantly more often than single men. A model of the relationship between hunting success and household food consumption indicates that the best hunters provided 3–4 times the amount of food to their families than median or poor hunters. These new data fill important gaps in our knowledge of the subsistence economy of the Hadza and uphold predictions derived from the household and kin provisioning hypotheses. Key evidence and assumptions backing prior claims that Hadza hunting is largely a form of status competition were not replicated in our study. In light of this, family provisioning is a more viable explanation for why good hunters are preferred as husbands and have higher fertility than others. (shrink)

In the past decade, experiments on altruistic punishment have played a central role in the study of the evolution of cooperation. By showing that people are ready to incur a cost to punish cheaters and that punishment help to stabilise cooperation, these experiments have greatly contributed to the rise of group selection theory. However, despite its experimental robustness, it is not clear whether altruistic punishment really exists. Here, I review the anthropological literature and show that hunter-gatherers rarely punish cheaters. Instead, (...) they avoid dealing with them and switch to other partners. I suggest that these data are better explained by individual selection, and in particular by partner choice models, in which individuals are in competition to be recruited by cooperative partners. I discuss two apparent problems for partner choice theories: large-scale cooperation and punishments in economic games. I suggest that rather than favouring group selection theory, these two phenomena provide evidence in favour of individual selection: (1) people produce large-scale cooperation through institutions in which punishment is not altruistic but rewarded on an individual basis; (2) punishment in experimental games can be explained without altruism and is indeed often better explained by individual interests. (shrink)

It is widely agreed that humans have specific abilities for cooperation and culture that evolved since their split with their last common ancestor with chimpanzees. Many uncertainties remain, however, about the exact moment in the human lineage when these abilities evolved. This article argues that cooperation and culture did not evolve in one step in the human lineage and that the capacity to stick to long-term and risky cooperative arrangements evolved before properly modern culture. I present evidence that Homo heidelbergensis (...) became increasingly able to secure contributions form others in two demanding Paleolithic public good games (PPGGs): cooperative feeding and cooperative breeding. I argue that the temptation to defect is high in these PPGGs and that the evolution of human cooperation in Homo heidelberngensis is best explained by the emergence of modern-like abilities for inhibitory control and goal maintenance. These executive functions are localized in the prefrontal cortex and allow humans to stick to social norms in the face of competing motivations. This scenario is consistent with data on brain evolution that indicate that the largest growth of the prefrontal cortex in human evolution occurred in Homo heidelbergensis and was followed by relative stasis in this part of the brain. One implication of this argument is that subsequent behavioral innovations, including the evolution of symbolism, art, and properly cumulative culture in modern Homo sapiens , are unlikely to be related to a reorganization of the prefrontal cortex, despite frequent claims to the contrary in the literature on the evolution of human culture and cognition. (shrink)

This paper critiques the competing “Grandmother Hypothesis” and “Embodied Capital Theory” as evolutionary explanations of the peculiarities of human life history traits. Instead, I argue that the correct explanation for human life history probably involves elements of both hypotheses: long male developmental periods and lives probably evolved due to group selection for male hunting via increased female fertility, and female long lives due to the differential contribution women’s complex foraging skills made to their children and grandchildren’s nutritional status within groups (...) provisioned by male hunting. (shrink)

In the developing world, the dramatic male bias in tobacco use is usually ascribed to pronounced gender disparities in social, political, or economic power. This bias might also reflect under-reporting by woman and/or over-reporting by men. To test the role of gender inequality on gender differences in tobacco use we investigated tobacco use among the Aka, a Congo Basin foraging population noted for its exceptionally high degree of gender equality. We also tested a sexual selection hypothesis—that Aka men’s tobacco use (...) is related to risk taking. Tobacco use, income, tobacco purchases, tobacco sharing, reasons for using tobacco, risk taking, and other variables were measured using structured surveys and peer reports. Tobacco use was verified by testing for salivary cotinine, a nicotine metabolite. Contrary to expectations, we found a very large male bias in tobacco use. Low levels of use among females appeared to be explained by aversions to tobacco, concerns over its negative effects on fetal health, and a desire to attract husbands, who prefer nonsmoking wives. High male use appeared to be related to a desire to enhance hunting abilities and attract and/or retain wives, who prefer husbands that smoke. We conclude that low levels of smoking by Aka women are better explained by the hypothesis that women evolved to avoid plant toxins to protect their fetuses and nursing infants. High male use might be better explained by sexual selection. We also highlight the important role that recreational drugs appear to play in hunter-gatherer sharing relationships. (shrink)

Evolutionary debunking arguments purport to undercut the justification of our moral judgments by showing why a tendency to make moral judgments would evolve regardless of the truth of those judgments. Machery and Mallon (2010. Evolution of morality. In J.M. Doris and The Moral Psychology Research Group (Eds.), The Moral Psychology Handbook (pp. 3-46). Oxford: Oxford University Press) have recently tried to disarm these arguments by showing that moral cognition – in the sense that is relevant to debunking – is not (...) the product of natural selection. Specifically, they present a barrage of increasingly influential challenges against reciprocity-based approaches to moral nativism. In the present paper I defend the nativist account of moral cognition against these criticisms, thereby bolstering the skeptical conclusions of evolutionary debunking arguments. However, Machery and Mallon's critique does successfully highlight several vulnerabilities in Richard Joyce's approach to debunking, suggesting several ways in which it can be revised toward generating a more robust version of the argument. (shrink)

The articles in this issue represent the pursuit of a new understanding of the human past, one that can replace the neo-saltationist view of a human revolution with models that can account for the complexities of the archaeological record and of human social lives. The articulation of archaeological, philosophical, and biological perspectives seems to offer a strong foundation for exploring available evidence, and this was the rationale for collecting these particular articles. Even at this preliminary stage there is a coherence (...) emerging in proposals: the origin and operation of symbolically rich, complexly signaling human social systems was the consequence of the long-term evolution of multiple components of perceiving and negotiating social interactions, a contingent outcome of myriad adaptive shifts rather than a single event. (shrink)

Our discussion of the commentaries begins, at the evolutionary level, with issues raised by our account of the evolution of morality in terms of partner-choice mutualism. We then turn to the cognitive level and the characterization and workings of fairness. In a final section, we discuss the degree to which our fairness-based approach to morality extends to norms that are commonly considered moral even though they are distinct from fairness.

This article investigates the nature and appeal of morally ambiguous protagonists, or anti-heroes, through an evolutionary lens. It argues that morally ambiguous protagonists navigate conflicts between prosocial and antisocial motivational pulls. In so doing they present audiences with a window onto the conflicts inherent in human sociality. Working from this premise, the article analyzes the morally ambiguous protagonist Walter White from the TV series Breaking Bad, complementing the analysis with survey results. The article finally discusses critically the role of moral (...) disengagement in enjoyment of stories with morally ambiguous protagonists. (shrink)

The domain of “folk-economics” consists in explicit beliefs about the economy held by laypeople, untrained in economics, about such topics as, for example, the causes of the wealth of nations, the benefits or drawbacks of markets and international trade, the effects of regulation, the origins of inequality, the connection between work and wages, the economic consequences of immigration, or the possible causes of unemployment. These beliefs are crucial in forming people's political beliefs and in shaping their reception of different policies. (...) Yet, they often conflict with elementary principles of economic theory and are often described as the consequences of ignorance, irrationality, or specific biases. As we will argue, these past perspectives fail to predict the particular contents of popular folk-economic beliefs and, as a result, there is no systematic study of the cognitive factors involved in their emergence and cultural success. Here we propose that the cultural success of particular beliefs about the economy is predictable if we consider the influence of specialized, largely automatic inference systems that evolved as adaptations to ancestral human small-scale sociality. These systems, for which there is independent evidence, include free-rider detection, fairness-based partner choice, ownership intuitions, coalitional psychology, and more. Information about modern mass-market conditions activates these specific inference systems, resulting in particular intuitions, for example, that impersonal transactions are dangerous or that international trade is a zero-sum game. These intuitions in turn make specific policy proposals more likely than others to become intuitively compelling, and, as a consequence, exert a crucial influence on political choices. (shrink)

Most of what we know about teaching comes from research among people living in large, politically and economically stratified societies with formal education systems and highly specialized roles with a global market economy. In this paper, we review and synthesize research on teaching among contemporary hunter-gatherer societies. The hunter-gatherer lifeway is the oldest humanity has known and is more representative of the circumstances under which teaching evolved and was utilized most often throughout human history. Research among contemporary hunter-gatherers also illustrates (...) a complex pattern of teaching that is both consistent with and distinct from teaching in other small- and large-scale societies with different subsistence practices and cultural forms. In particular, we find that the cultural emphasis on individual autonomy and socio-political egalitarianism among hunter-gatherers differently shapes how teaching occurs. For example, teaching clearly exists among hunter-gatherers and appears in many forms, including institutionalized instruction in valued cultural and technical skills. However, teaching tends to be less common in hunter-gatherer societies because people live in small, intimate egalitarian, groups that support each other’s learning in a variety of ways without teaching. Furthermore, foundational cultural schemas of autonomy and egalitarianism impact the nature of teaching. For example, adults and older children limit their interventions, permitting autonomous learning, and, when they occur, teaching episodes are generally brief, subtle, indirect, and situated in a present activity. We discuss the implications of this research in terms of discussions of the evolution of human cognition and the co-evolution of teaching and culture through the process of cultural niche construction. (shrink)

Economists and biologists have proposed a distinction between two mechanisms – “strong” and “weak” reciprocity – that may explain the evolution of human sociality. Weak reciprocity theorists emphasize the benefits of long-term cooperation and the use of low-cost strategies to deter free-riders. Strong reciprocity theorists, in contrast, claim that cooperation in social dilemma games can be sustained by costly punishment mechanisms, even in one-shot and finitely repeated games. To support this claim, they have generated a large body of evidence concerning (...) the willingness of experimental subjects to punish uncooperative free-riders at a cost to themselves. In this article, I distinguish between a “narrow” and a “wide” reading of the experimental evidence. Under the narrow reading, punishment experiments are just useful devices to measure psychological propensities in controlled laboratory conditions. Under the wide reading, they replicate a mechanism that supports cooperation also in “real-world” situations outside the laboratory. I argue that the wide interpretation must be tested using a combination of laboratory data and evidence about cooperation “in the wild.” In spite of some often-repeated claims, there is no evidence that cooperation in the small egalitarian societies studied by anthropologists is enforced by means of costly punishment. Moreover, studies by economic and social historians show that social dilemmas in the wild are typically solved by institutions that coordinate punishment, reduce its cost, and extend the horizon of cooperation. The lack of field evidence for costly punishment suggests important constraints about what forms of cooperation can or cannot be sustained by means of decentralised policing. (shrink)

Many studies show that punishment, although able to stabilize cooperation at high levels, destroys gains which makes it less efficient than alternatives with no punishment. Standard public goods games (PGGs) in fact show exactly these patterns. However, both evolutionary theory and real world institutions give reason to expect institutions with punishment to be more efficient, particularly in the long run. Long-term cooperative partnerships with punishment threats for non-cooperation should outperform defection prone non-punishing ones. This article demonstrates that fieldwork data from (...) hunter-gatherers, common pool resource management cases and even PGGs support this hypothesis. Although earnings in PGGs with a punishment option may be lower at the beginning, efficiency increases dramatically over time. Most ten-period PGGs cannot capture this change because their time horizon is too short. (shrink)

Punitive behaviours are often assumed to be the result of an instinct for punishment. This instinct would have evolved to punish wrongdoers and it would be the evidence that cooperation has evolved by group selection. Here, I propose an alternative theory according to which punishment is a not an adaptation and that there was no specific selective pressure to inflict costs on wrongdoers in the ancestral environment. In this theory, cooperation evolved through partner choice for mutual advantage. In the ancestral (...) environment, individuals were in competition to be recruited in cooperative ventures and it was vital to share the benefits of cooperation in a mutually advantageous manner. If individuals took a bigger share of the benefits, their partners would leave them for more interesting partners. If they took a smaller share, they would be exploited by their partners who would receive more than what they had contributed to produce. This competition led to the selection of a sense of fairness, a cognitive adaptation aiming to share equally the benefits of cooperation in order to attract partners. In this theory, punishment is not necessary for the evolution of cooperation. Punitive behaviours are only a way to restore fairness by compensating the victim or penalizing the culprit. Drawing on behavioural economics, legal anthropology, and cognitive psychology, I show that empirical data fit better with this framework than with the theory of group selection. When people punish, they do so to restore fairness rather than to help the group. (shrink)

Within paleoanthropology, the origin of behavioral modernity is a famous problem. Very large-brained hominins have lived for around half a million years, yet social lives resembling those known from the ethnographic record appeared perhaps 100,000 years ago. Why did it take 400,000 years for humans to start acting like humans? In this article, I argue that part of the solution is a transition in the economic foundations of cooperation from a relatively undemanding form, to one that imposed much more stress (...) on human motivational and cognitive mechanisms. The rich normative, ceremonial, and ideological lives of humans are a response to this economic revolution in forager lives; from one depending on immediate return mutualism to one depending on delayed and third-party reciprocation. (shrink)

The standard theories of cooperation in humans, which depend on repeated interaction and reputation effects among self-regarding agents, are inadequate. Strong reciprocity, a predisposition to participate in costly cooperation and the punishment, fosters cooperation where self-regarding behaviors fail. The effectiveness of socially coordinated punishment depends on individual motivations to participate, which are based on strong reciprocity motives. The relative infrequency of high-cost punishment is a result of the ubiquity of strong reciprocity, not its absence.

Humans share with other mammals and primates many social motivations and emotions, but they are also much more cooperative than even their closest primate relatives. Here I review recent comparative experiments and analyses that illustrate humans’ species-typical social motivations and emotions for cooperation in comparison with those of other great apes. These may be classified most generally as (i) ‘you > me’ (e.g., prosocial sympathy, informative and pedagogical motives in communication); (ii) ‘you = me’ (e.g., feelings of mutual respect, fairness, (...) resentment); (iii) ‘we > me’ (e.g., feelings of obligation and guilt); and (iv) ‘WE (in the group) > me’ (e.g., in-group loyalty and conformity to norms, shame, and many in-group biases). The existence of these species-typical and species-universal motivations and emotions provides compelling evidence for the importance of cooperative activities in the human species. (shrink)

In the developing world, the dramatic male bias in tobacco use is usually ascribed to pronounced gender disparities in social, political, or economic power. This bias might also reflect under-reporting by woman and/or over-reporting by men. To test the role of gender inequality on gender differences in tobacco use we investigated tobacco use among the Aka, a Congo Basin foraging population noted for its exceptionally high degree of gender equality. We also tested a sexual selection hypothesis—that Aka men’s tobacco use (...) is related to risk taking. Tobacco use, income, tobacco purchases, tobacco sharing, reasons for using tobacco, risk taking, and other variables were measured using structured surveys and peer reports. Tobacco use was verified by testing for salivary cotinine, a nicotine metabolite. Contrary to expectations, we found a very large male bias in tobacco use. Low levels of use among females appeared to be explained by aversions to tobacco, concerns over its negative effects on fetal health, and a desire to attract husbands, who prefer nonsmoking wives. High male use appeared to be related to a desire to enhance hunting abilities and attract and/or retain wives, who prefer husbands that smoke. We conclude that low levels of smoking by Aka women are better explained by the hypothesis that women evolved to avoid plant toxins to protect their fetuses and nursing infants. High male use might be better explained by sexual selection. We also highlight the important role that recreational drugs appear to play in hunter-gatherer sharing relationships. (shrink)

Unlike other primate males, men invest substantial effort in producing food that is consumed by others. The Hunting Hypothesis proposes this pattern evolved in early Homo when ancestral mothers began relying on their mates’ hunting to provision dependent offspring. Evidence for this idea comes from hunter-gatherer ethnography, but data we collected in the 1980s among East African Hadza do not support it. There, men targeted big game to the near exclusion of other prey even though they were rarely successful and (...) most of the meat went to others, at significant opportunity cost to their own families. Based on Hadza data collected more recently, Wood and Marlowe contest our position, affirming the standard view of men’s foraging as family provisioning. Here we compare the two studies, identify similarities, and show that emphasis on big game results in collective benefits that would not be supplied if men foraged mainly to provision their own households. Male status competition remains a likely explanation for Hadza focus on big game, with implications for hypotheses about the deeper past. (shrink)

The presence of a kinship link between nuclear families is the strongest predictor of interhousehold sharing in an indigenous, predominantly Dolgan food-sharing network in northern Russia. Attributes such as the summed number of hunters in paired households also account for much of the variation in sharing between nuclear families. Differences in the number of hunters in partner households, as well as proximity and producer/consumer ratios of households, were investigated with regard to cost-benefit models. The subset of households involved in reciprocal (...) meal sharing is 26 of 84 household host-guest pairs. The frequency of reciprocal meal sharing between families in this subset is positively correlated with average household relatedness. The evolution of cooperation through clustering may illuminate the relationship between kinship and reciprocity at this most intimate level of food sharing. (shrink)

Experimental research has studied the emergence of fairness criteria such as merit and equality at increasingly younger ages. How much does the recognition and practice of these principles depend on the influence of central aspects of Western educated and industrialized societies? In an attempt to answer these questions, this article provides evidence regarding the choices of children in the Kogi indigenous community of the Sierra Nevada de Santa Marta, a traditional society living in the mountains of Northern Colombia that practices (...) swidden agriculture, cattle-raising, and enjoys a special cultural status granted by the Colombian Constitution. Two groups of 6–7 and 10–11 year olds were tested on a modified dictator game and several scenarios from a resource distribution task including different fairness criteria. Our results point to the lack of focality of the idea of merit among Kogi children at these ages when deciding on third-party allocation tasks, even when the design prevented equal distribution. (shrink)

The fact that humans cooperate with nonkin is something we take for granted, but this is an anomaly in the animal kingdom. Our species’ ability to behave prosocially may be based on human-unique psychological mechanisms. We argue here that these mechanisms include the ability to care about the welfare of others (other-regarding concerns), to “feel into” others (empathy), and to understand, adhere to, and enforce social norms (normativity). We consider how these motivational, emotional, and normative substrates of prosociality develop in (...) childhood and emerged in our evolutionary history. Moreover, we suggest that these three mechanisms all serve the critical function of aligning individuals with others: Empathy and other-regarding concerns align individuals with one another, and norms align individuals with their group. Such alignment allows us to engage in the kind of large-scale cooperation seen uniquely in humans. (shrink)

In this paper I argue the best examples of the methods in the evolutionary social sciences don’t actually resemble either of the two methods called “Adaptive Thinking” or “Reverse Engineering” described by evolutionary psychologists. Both AT and RE have significant problems. Instead, the best adaptationist work in the ESSs seems to be based on and is aiming at a different method that avoids the problems of AT and RE: it is a behavioral level method that starts with information about both (...) the trait in question and knowledge of the EEA. I describe some examples from the literature, and suggest how a behavioral level ESS might still contribute to the discovery and understanding of human psychology. Finally, I describe some remaining problems for adaptationist reasoning of this kind. (shrink)

Various human groups, from food foragers to inner-city urban Americans, have used widespread sharing of resources through kin networks as a means of buffering themselves against fluctuations in resource availability in their environments. This paper addresses the effects of progressive incorporation into a wage-labor economy on the benefits of traditional kin networks for two social classes in urban South India. Predictions regarding the effects of kin network wealth, education, and size on child and spouse characteristics and methods of financing marriages (...) are tested using various regression techniques. Despite the rapid growth of participation in a wage-labor economy, it is found that kin network characteristics still have an important impact on investment behavior among families in Bangalore in both social classes. Network wealth is found to have a positive effect on child and spouse characteristics, and large networks are found to act as significant drains on family resources. However, the results for education are broadly consistent with an interpretation of increasing family autonomy as parents’ education has a far stronger influence on child and spouse characteristics across categories than network education does. Finally, professional-class parents are found to prefer financing marriages using formal mechanisms such as savings and bank loans while working-class parents preferentially finance marriages using credit from relatives and friends. (shrink)

Strong reciprocity theorists claim that punishment has evolved to promote the good of the group and to deter cheating. By contrast, weak reciprocity suggests that punishment aims to restore justice (i.e., reciprocity) between the criminal and his victim. Experimental evidences as well as field observations suggest that humans punish criminals to restore fairness rather than to support group cooperation.

Experimental studies on punishment have sometimes been over-interpreted not only for the reasons Guala lists, but also because of a frequent conflation of proximate and ultimate explanatory levels that Guala's review perpetuates. Moreover, for future analyses we may need a clearer classification of different kinds of punishment.

Pietraszewski exemplifies the need for computational theory using group conflict; I complement this with an example of group cooperation. He criticizes past theories for having black boxes; I suggest his theory also has a black box – the concept of costs. He divides what mentally constitutes a group from mere ancillary attributes; I hazard that some of these attributes are essential.

Researchers commonly use long-term average production inequalities to characterize cross-cultural patterns in foraging divisions of labor, but little is known about how the strategies of individuals shape such inequalities. Here, we explore the factors that lead to daily variation in how much men produce relative to women among Martu, contemporary foragers of the Western Desert of Australia. We analyze variation in foraging decisions on temporary foraging camps and find that the percentage of total camp production provided by each gender varies (...) primarily as a function of men’s average bout successes with large, mobile prey. When men target large prey, either their success leads to a large proportional contribution to the daily harvest, or their failure results in no contribution. When both men and women target small reliable prey, production inequalities by gender are minimized. These results suggest that production inequalities among Martu emerge from stochastic variation in men’s foraging success on large prey measured against the backdrop of women’s consistent production of small, low-variance resources. (shrink)

Recent analyses of food sharing in small-scale societies indicate that reciprocal altruism maintains interhousehold food transfers, even among close kin. In this study, matrix-based regression methods are used to test the explanatory power of reciprocal altruism, kin selection, and tolerated scrounging. In a network of 35 households in Nicaragua’s Bosawas Reserve, the significant predictors of food sharing include kinship, interhousehold distance, and reciprocity. In particular, resources tend to flow from households with relatively more meat to closely related households with little, (...) as predicted by kin selection. This generalization is especially true of household dyads with mother-offspring relationships, which suggests that studies of food sharing may benefit from distinctions between lineal and collateral kin. Overall, this analysis suggests that exchanges among kin are primarily associated with differences in need, not reciprocity. Finally, although large game is distributed widely, qualitative observations indicate that hunters typically do not relinquish control of the distribution in ways predicted by costly signaling theory. (shrink)

Human cooperation and group living are based on societies in which individuals not only care about their own interests but share common norms and values – such as morality and prosocial behavior. As early as the 18th century, Immanuel Kant postulated autonomy as the key to human morality. Kant explained that a rational agent with a free will would necessarily make moral – not immoral – decisions. However, the fundamental question of how moral behavior acquires normative weight remains unresolved until (...) the present day, especially when moral behavior entails personal costs for the individual. This dissertation builds on Kant’s thesis and aims to investigate important building blocks of moral autonomy at preschool age. Therefore, children’s own prosocial decisions as well as their normative and descriptive expectations about others’ prosocial actions are assessed and linked to fundamental underlying mechanisms such as cultural learning and collective intentionality. Study 1 assessed whether preschoolers enforce agreed-upon prosocial ver-sus selfish sharing norms in a group dictator game. Three- and 5-year-old children and two hand puppets had the opportunity to agree on how to distribute re-sources between themselves and a group of passive recipients. The findings sug-gest that preschoolers understand prosocial, but not selfish, agreements as binding even though prosocial sharing norms are associated with personal costs. Study Set 2 assessed in two experiments whether observed choice increases the children’s own prosocial sharing behavior. In Experiment 1, children observed an adult model who was provided with costly choice, non-costly choice, or no choice. As a next step, children were given the opportunity to decide how many stickers they would like to share with a sad animal puppet. Experiment 2 aimed to investigate possible age effects. The study design was reduced to condition and, a second test trial was added. Taken together, the results of Study Set 2 suggest that 5-year-old’s prosocial sharing behavior increases when previously having observed someone who intentionally acts prosocially at a personal cost. Study 3 investigated preschoolers’ descriptive expectations about the causal agent of prosocial and selfish actions, based on agents’ prior history of voluntary versus involuntary prosocial behavior. The results show that children at the age of 5.5 years use information about the circumstances and intentions of previous actions to generate descriptive expectations about other’s future prosocial behavior. From 4 years of age, children distinguish between an agent who shares voluntarily and an agent who shares only involuntarily. Taken together, this dissertation shows that preschool aged children infer and enforce prosocial – but not selfish – sharing norms. They engage in prosocial sharing which is affected by observed choice and they form descriptive expectations about others tendency to behave prosocial or selfish on the base of knowledge about the agents prosocial versus selfish intentions. (shrink)

Exponential random graph modeling (ERGM) is used here to test hypotheses derived from human behavioral ecology about the adaptive nature of human food sharing. Respondents in all (n = 317) households in the fishing and sea-hunting village of Lamalera, Indonesia, were asked to name those households to whom they had more frequently given (and from whom they had more frequently received) food during the preceding sea-hunting season. The responses were used to construct a social network of between-household food-sharing relationships in (...) the village. The results show that kinship, proximity, and reciprocal sharing all strongly increase the probability of giving food to a household. The effects of kinship and distance are relatively independent of each other, although reciprocity is more common among residentially and genealogically close households. The results show support for reciprocal altruism as a motivation for food sharing, while kinship and distance appear to be important partner-choice criteria. (shrink)

Anecdotal evidence from many hunter-gatherer societies suggests that successful hunters experience higher prestige and greater reproductive success. Detailed quantitative data on these patterns are now available for five widely dispersed cases (Ache, Hadza, !Kung, Lamalera, and Meriam) and indicate that better hunters exhibit higher age-corrected reproductive success than other men in their social group. Leading explanations to account for this pattern are: (1) direct provisioning of hunters’ wives and offspring, (2) dyadic reciprocity, (3) indirect reciprocity, (4) costly signaling, and (5) (...) phenotypic correlation. I examine the qualitative and quantitative evidence bearing on these explanations and conclude that although none can be definitively rejected, extensive and apparently unconditional sharing of large game somewhat weakens the first three explanations. The costly signaling explanation has support in some cases, although the exact nature of the benefits gained from mating or allying with or deferring to better hunters needs further study. (shrink)

Helping behavior is likely to have evolved to increase summary chances for survival of an individual and their group. Nevertheless, populations differ significantly in their eagerness to help, and still little is known about populational and inter-individual determinants of these differences. Previous studies indicated that economic and physiological factors might influence helping behavior. The aim of the present study was to investigate the effects of approach to resource management of a society (immediate-return economy vs. delayed-return economy), prenatal androgenization (based on (...) second-to-fourth digit ratio), and physical strength (based on hand grip strength) on helping behavior towards others. Helping was assessed in terms of both general eagerness to help and differential helping towards: (1) kin, (2) other group members indiscriminately, (3) friends, and (4) those from whom help was obtained in the past. Based on data collected in two small-scale societies, we found that people in the egalitarian immediate-return society (the Hadza hunter-gatherers of Tanzania) engaged in helping behavior significantly more often than representatives of a more stratified delayed-return economy (Yali horticulturalists of Papua). Additionally, our results revealed that physical strength was a significant predictor of helping behavior in women but not in men. We discuss our findings in the light of the adaptive value of helping behavior. (shrink)

I present evidence that humans have evolved convergently to social insects with regard to a large suite of social, ecological, and reproductive phenotypes. Convergences between humans and social insects include: (1) groups with genetically and environmentally defined structures; (2) extensive divisions of labor; (3) specialization of a relatively restricted set of females for reproduction, with enhanced fertility; (4) extensive extramaternal care; (5) within-group food sharing; (6) generalized diets composed of high-nutrient-density food; (7) solicitous juveniles, but high rates of infanticide; (8) (...) ecological dominance; (9) enhanced colonizing abilities; and (10) collective, cooperative decision-making. Most of these convergent phenotypic adaptations stem from reorganization of key life-history trade-offs due to behavioral, physiological, and life-historical specializations. Despite their extensive socioreproductive overlap with social insects, humans differ with regard to the central aspect of eusociality: reproductive division of labor. This difference may be underpinned by the high energetic costs of producing offspring with large brains. (shrink)

Paul Seabright is the first to clearly identify a major puzzle about human social evolution: the expansion of cooperation in the more complex societies of the Holocene. Identifying that problem is a major achievement, but in this paper I give a somewhat different account of the nature of the problem and a somewhat different account of the social world of Pleistocene foragers. So, we agree that there is a problem, but not on its nature or solution.