Acknowledgments 1. Culture Is Essential 2. Culture Exists 3. Culture Evolves 4. Culture Is an Adaptation 5. Culture Is Maladaptive 6. Culture and Genes Coevolve 7. Nothing about Culture Makes Sense except in the Light of Evolution.

What motives underlie the ways humans interact socially? Are these the same for all societies? Are these part of our nature, or influenced by our environments?Over the last decade, research in experimental economics has emphatically falsified the textbook representation of Homo economicus. Literally hundreds of experiments suggest that people care not only about their own material payoffs, but also about such things as fairness, equity and reciprocity. However, this research left fundamental questions unanswered: Are such social preferences stable components of (...) human nature; or, are they modulated by economic, social and cultural environments? Until now, experimental research could not address this question because virtually all subjects had been university students, and while there are cultural differences among student populations throughout the world, these differences are small compared to the full range of human social and cultural environments. A vast amount of ethnographic and historical research suggests that people's motives are influenced by economic, social, and cultural environments, yet such methods can only yield circumstantial evidence about human motives. Combining ethnographic and experimental approaches to fill this gap, this book breaks new ground in reporting the results of a large cross-cultural study aimed at determining the sources of social preferences that underlie the diversity of human sociality. The same experiments which provided evidence for social preferences among university students were performed in fifteen small-scale societies exhibiting a wide variety of social, economic and cultural conditions by experienced field researchers who had also done long-term ethnographic field work in these societies. The findings of these experiments demonstrated that no society in which experimental behaviour is consistent with the canonical model of self-interest. Indeed, results showed that the variation in behaviour is far greater than previously thought, and that the differences between societies in market integration and the importance of cooperation explain a substantial portion of this variation, which individual-level economic and demographic variables could not. Finally, the extent to which experimental play mirrors patterns of interaction found in everyday life is traced.The book starts with a succinct but substantive introduction to the use of game theory as an analytical tool and its use in the social sciences for the rigorous testing of hypotheses about fundamental aspects of social behaviour outside artificially constructed laboratories. The results of the fifteen case studies are summarized in a suggestive chapter about the scope of the project. (shrink)

Researchers from across the social sciences have found consistent deviations from the predictions of the canonical model of self-interest in hundreds of experiments from around the world. This research, however, cannot determine whether the uniformity results from universal patterns of human behavior or from the limited cultural variation available among the university students used in virtually all prior experimental work. To address this, we undertook a cross-cultural study of behavior in ultimatum, public goods, and dictator games in a range of (...) small-scale societies exhibiting a wide variety of economic and cultural conditions. We found, first, that the canonical model – based on self-interest – fails in all of the societies studied. Second, our data reveal substantially more behavioral variability across social groups than has been found in previous research. Third, group-level differences in economic organization and the structure of social interactions explain a substantial portion of the behavioral variation across societies: the higher the degree of market integration and the higher the payoffs to cooperation in everyday life, the greater the level of prosociality expressed in experimental games. Fourth, the available individual-level economic and demographic variables do not consistently explain game behavior, either within or across groups. Fifth, in many cases experimental play appears to reflect the common interactional patterns of everyday life. Key Words: altruism; cooperation; cross-cultural research; experimental economics; game theory; ultimatum game; public goods game; self-interest. (shrink)

In the last 60,000 years humans have expanded across the globe and now occupy a wider range than any other terrestrial species. Our ability to successfully adapt to such a diverse range of habitats is often explained in terms of our cognitive ability. Humans have relatively bigger brains and more computing power than other animals and this allows us to figure out how to live in a wide range of environments. Here we argue that humans may be smarter than other (...) creatures, but none of us is nearly smart enough to acquire all of the information necessary to survive in any single habitat. In even the simplest foraging societies, people depend on a vast array of tools, detailed bodies of local knowledge, and complex social arrangements, and often do not understand why these tools, beliefs, and behaviors are adaptive. We owe our success to our uniquely-developed ability to learn from others. This capacity enables humans to gradually accumulate information across generations, and develop well-adapted tools, beliefs, and practices that are too complex for any single individual to invent during their lifetime. (shrink)

Robert Boyd*†, Herbert Gintis‡, Samuel Bowles§, and Peter J. Richerson¶.

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If culture is defined as variation acquired and maintained by social learning, then culture is common in nature. However, cumulative cultural evolution resulting in behaviors that no individual could invent on their own is limited to humans, song birds, and perhaps chimpanzees. Circumstantial evidence suggests that cumulative cultural evolution requires the capacity for observational learning. Here, we analyze two models the evolution of psychological capacities that allow cumulative cultural evolution. Both models suggest that the conditions which allow the evolution of (...) such capacities when rare are much more stringent than the conditions which allow the maintenance of the capacities when common. This result follows from the fact that the assumed benefit of the capacities, cumulative cultural adaptation, cannot occur when the capacities are rare. These results suggest why such capacities may be rare in nature. (shrink)

Formal models of cultural evolution analyze how cognitive processes combine with social interaction to generate the distributions and dynamics of ‘representations.’ Recently, cognitive anthropologists have criticized such models. They make three points: mental representations are non-discrete, cultural transmission is highly inaccurate, and mental representations are not replicated, but rather are ‘reconstructed’ through an inferential process that is strongly affected by cognitive ‘attractors.’ They argue that it follows from these three claims that: 1) models that assume replication or replicators are inappropriate, (...) 2) selective cultural learning cannot account for stable traditions, and 3) selective cultural learning cannot generate cumulative adaptation. Here we use three formal models to show that even if the premises of this critique are correct, the deductions that have been drawn from them are false. In the rst model, we assume continuously varying representations under the in uence of weak selective transmission and strong attractors. We show that if the attractors are suf ciently strong relative to selective forces, the continuous representation model reduces to the standard.. (shrink)

Much existing literature in anthropology suggests that teaching is rare in non-Western societies, and that cultural transmission is mostly vertical (parent-to-offspring). However, applications of evolutionary theory to humans predict both teaching and non-vertical transmission of culturally learned skills, behaviors, and knowledge should be common cross-culturally. Here, we review this body of theory to derive predictions about when teaching and non-vertical transmission should be adaptive, and thus more likely to be observed empirically. Using three interviews conducted with rural Fijian populations, we (...) find that parents are more likely to teach than are other kin types, high-skill and highly valued domains are more likely to be taught, and oblique transmission is associated with high-skill domains, which are learned later in life. Finally, we conclude that the apparent conflict between theory and empirical evidence is due to a mismatch of theoretical hypotheses and empirical claims across disciplines, and we reconcile theory with the existing literature in light of our results. (shrink)

Group beneficial norms are common in human societies. The persistence of such norms is consistent with evolutionary game theory, but existing models do not provide a plausible explanation for why they are common. We show that when a model of imitation used to derive replicator dynamics in isolated populations is generalized to allow for population structure, group beneficial norms can spread rapidly under plausible conditions. We also show that this mechanism allows recombination of different group beneficial norms arising in..

It is often argued that culture is adaptive because it allows people to acquire useful information without costly learning. In a recent paper Rogers analyzed a simple mathematical model that showed that this argument is wrong. Here we show that Rogers ' result is robust. As long as the only benefit of social learning is that imitators avoid learning costs, social learning does not increase average fitness. However, we also show that social learning can be adaptive if it makes individual (...) learning more accurate or less costly. (shrink)

The complexity of human societies of the past few thousand years rivals that of social insect societies. We hypothesize that two sets of social “instincts” underpin and constrain the evolution of complex societies. One set is ancient and shared with other social primate species, and one is derived and unique to our lineage. The latter evolved by the late Pleistocene, and led to the evolution of institutions of intermediate complexity in acephalous societies. The institutions of complex societies often conflict with (...) our social instincts. The complex societies of the past few thousand years can function only because cultural evolution has created effective “work-arounds” to manage such instincts. We describe a series of work-arounds and use the data on the relative effectiveness of WWII armies to test the work-around hypothesis. (shrink)

The complexity of human societies of the past few thousand years rivals that of social insect societies. We hypothesize that two sets of social “instincts” underpin and constrain the evolution of complex societies. One set is ancient and shared with other social primate species, and one is derived and unique to our lineage. The latter evolved by the late Pleistocene, and led to the evolution of institutions of intermediate complexity in acephalous societies. The institutions of complex societies often conflict with (...) our social instincts. The complex societies of the last few thousand years can function only because cultural evolution has created effective “work-arounds” to manage such instincts. We describe a series of work-arounds and use the data on the relative effectiveness of WWII armies to test the work-around hypothesis. (shrink)

Much human adaptation depends on the gradual accumulation of culturally transmitted knowledge and technology. Recent models of this process predict that large, well-connected populations will have more diverse and complex tool kits than small, isolated populations. While several examples of the loss of technology in small populations are consistent with this prediction, it found no support in two systematic quantitative tests. Both studies were based on data from continental populations in which contact rates were not available, and therefore these studies (...) do not provide a test of the models. Here, we show that in Oceania, around the time of early European contact, islands with small populations had less complicated marine foraging technology. This finding suggests that explanations of existing cultural variation based on optimality models alone are incomplete because demography plays an important role in generating cumulative cultural adaptation. It also indicates that hominin populations with similar cognitive abilities may leave very different archaeological records, a conclusion that has important implications for our understanding of the origin of anatomically modern humans and their evolved psychology. (shrink)

Human societies are based on cooperation among large numbers of genetically unrelated individuals. This behavior is puzzling from an evolutionary perspective. Because cooperators are..

Most evolutionary analyses of animal communication suggest that low-cost signals can evolve only when both the signaller and the recipient rank outcomes in the same order. When there is a conflict of interest between sender and receiver, honest signals must be costly. However, recent work suggests that low-cost signals can be evolutionarily stable, even when the sender and the receiver rank outcomes in different orders, as long as the interest in achieving coordination is sufficiently great. In this paper, we extend (...) this body of work by analysing a game theory model that shows that low-cost signals can evolve when there are conflicts of interest and no interest in coordination, as long as individuals interact repeatedly. We also present an empirical example indicating that female rhesus macaques, Macaca mulatta, use honest, low-cost, vocal signals to facilitate interactions when conflicts of interest exist. (shrink)

Using samples from three diverse populations, we test evolutionary hypotheses regarding how people reason about the inheritance of various traits. First, we provide a framework for differentiat-ing the outputs of mechanisms that evolved for reasoning about variation within and between biological taxa and culturally evolved ethnic categories from a broader set of beliefs and categories that are the outputs of structured learning mechanisms. Second, we describe the results of a modified “switched-at-birth” vignette study that we administered among children and adults (...) in Puno, Yasawa, and adults in the United States. This protocol permits us to study perceptions of prenatal and social transmission pathways for various traits and to differentiate the latter into vertical versus horizontal cultural influence. These lines of evidence suggest that people use all three mechanisms to reason about the distribution of traits in the population. Participants at all three sites develop expectations that morphological traits are under prenatal influence, and that belief traits are more culturally influenced. On the other hand, each population holds culturally specific beliefs about the degree of social influence on non-morphological traits and about the degree of vertical transmission—with only participants in the United States expecting parents to have much social influence over their children. We reinterpret people's differentiation of trait transmission pathways in light of humans' evolutionary history as a cultural species. (shrink)

Most human populations are subdivided into ethnic groups which have self-ascribed membership and are marked by seemingly arbitrary traits such as distinctive styles of dress or speech. Existing explanations of ethnicity do not adequately explain the origin and maintenance of group marking. Here we develop a mathematical model which shows that groups distinguished by both differences in social norms and in arbitrary markers can emerge and remain stable despite significant mixing between them, if (1) people preferentially interact in mutually beneficial (...) social interaction with people who have the same marker as they do, and (2) they acquire their markers and social behaviors by imitating successful individuals. We also show that the propensity to interact with people with markers like oneself may be favored by natural selection under plausible conditions. (shrink)

Anthropologists believe that human behavior is governed by culturally transmitted norms, and that such norms contain accumulated wisdom that allows people to behave sensibly even though they do not understand why they do what they do. Economists and other rational choice theorists have been skeptical about functionalist claims because anthropologists have not provided any plausible mechanism which could explain why norms have this property. Here, we outline two such mechanisms. We show that occasional learning when coupled with cultural transmission and (...) a tendency to conform can lead to the spread of sensible norms even though very few people understand why they are sensible. We also show that norms that help solve problems of selfcontrol that arise from time-inconsistent preferences can spread if individuals tend to imitate successful people and are occasionally influenced by members of other groups with different norms. (shrink)

Many accounts of ethnic phenomena imply that processes such as stereotyping, essentialism, ethnocentrism, and intergroup hostility stem from a unitary adaptation for reasoning about groups. This is partly justified by the phenomena’s co-occurrence in correlational studies. Here we argue that these behaviors are better modeled as functionally independent adaptations that arose in response to different selection pressures throughout human evolution. As such, different mechanisms may be triggered by different group boundaries within a single society. We illustrate this functionalist framework using (...) ethnographic work from the Quechua-Aymara language boundary in the Peruvian Altiplano. We show that different group boundaries motivate different ethnic phenomena. For example, people have strong stereotypes about socioeconomic categories, which are not cooperative units, whereas they hold fewer stereotypes about communities, which are the primary focus of cooperative activity. We also show that, despite the cross-cultural importance of ethnolinguistic boundaries, the Quechua-Aymara linguistic distinction does not strongly motivate any of these intergroup processes. (shrink)

What are the causes of the evolution of complex cognition? Discussions of the evolution of cognition sometimes seem to assume that more complex cognition is a fundamental advance over less complex cognition, as evidenced by a broad trend toward larger brains in evolutionary history. Evolutionary biologists are suspicious of such explanations since they picture natural selection as a process leading to adaptation to local environments, not to progressive trends. Cognitive adaptations will have costs, and more complex cognition will evolve only (...) when its local utility outweighs them. (shrink)

Understanding cooperation and punishment in small-scale societies is crucial for explaining the origins of human cooperation. We studied warfare among the Turkana, a politically uncentralized, egalitarian, nomadic pastoral society in East Africa. Based on a representative sample of 88 recent raids, we show that the Turkana sustain costly cooperation in combat at a remarkably large scale, at least in part, through punishment of free-riders. Raiding parties comprised several hundred warriors and participants are not kin or day-to-day interactants. Warriors incur substantial (...) risk of death and produce collective benefits. Cowardice and desertions occur. (shrink)

Over the past several decades, we have argued that cultural evolution can facilitate the evolution of largescale cooperation because it often leads to more rapid adaptation than genetic evolution, and, when multiple stable equilibria exist, rapid adaptation leads to variation among groups. Recently, Lehmann, Feldman, and colleagues have published several papers questioning this argument. They analyze models showing that cultural evolution can actually reduce the range of conditions under which cooperation can evolve and interpret these models as indicating that we (...) were wrong to conclude that culture facilitated the evolution of human cooperation. In the main, their models assume that rates of cultural adaption are not.. (shrink)

E.O. Wilson (1975) described humans as one of the four pinnacles of social evolution. The other pinnacles are the colonial invertebrates, the social insects, and the non-human mammals. Wilson separated human sociality from that of the rest of the mammals because, with the exception of the social insect like Naked Mole Rats, only humans have generated societies of a grade of complexity that approaches that of the social insects and colonial invertebrates. In the last few millennia, human societies have even (...) begun to exceed, in numbers of individuals and degree of complexity, the societies of ants, termites, and corals. (shrink)

The application of phylogenetic methods to cultural variation raises questions about how cultural adaption works and how it is coupled to cultural transmission. Cultural group selection is of particular interest in this context because it depends on the same kinds of mechanisms that lead to tree-like patterns of cultural variation. Here, we review ideas about cultural group selection relevant to cultural phylogenetics. We discuss why group selection among multiple equilibria is not subject to the usual criticisms directed at group selection, (...) why multiple equilibria are a common phenomena, and why selection among multiple equilibria is not likely to be an important force in genetic evolution. We also discuss three forms of group competition and the processes that cause populations to shift from one equilibrium to another and create a mutation-like process at the group level. (shrink)

We would like to thank the commentators for their generous comments, valuable insights and helpful suggestions. We begin this response by discussing the selfishness axiom and the importance of the preferences, beliefs, and constraints framework as a way of modeling some of the proximate influences on human behavior. Next, we broaden the discussion to ultimate-level (that is evolutionary) explanations, where we review and clarify gene-culture coevolutionary theory, and then tackle the possibility that evolutionary approaches that exclude culture might be sufficient (...) to explain the data. Finally, we consider various methodological and epistemological concerns expressed by our commentators. (shrink)

This paper presents a simple mathematical model that shows how economic inequality between social groups can arise and be maintained even when the only adaptive learning process driving cultural evolution increases individuals’ economic gains. The key assumptions are that human populations are structured into groups and that cultural learning is more likely to occur within than between groups. Then, if groups are sufficiently isolated and there are potential gains from specialization and exchange, stable stratification can sometimes result. This model predicts (...) that stratification is favored, ceteris paribus, by (1) greater surplus production, (2) more equitable divisions of the surplus among specialists, (3) greater cultural isolation among subpopulations within a society, and (4) more weight given to economic success by cultural learners. (shrink)

Social institutions are the laws, informal rules, and conventions that give durable structure to social interactions within a population. Such institutions are typically not designed consciously, are heritable at the population level, are frequently but not always group benefi cial, and are often symbolically marked. Conceptualizing social institutions as one of multiple possible stable cultural equilibrium allows a straightforward explanation of their properties. The evolution of institutions is partly driven by both the deliberate and intuitive decisions of individuals and collectivities. (...) The innate components of human psychology coevolved in response to a culturally evolved, institutional environment and refl ect a prosocial tendency of choices we make about institutional forms. (shrink)

Among the many vivid metaphors in Darwin’s Dangerous Idea, one stands out. The understanding of how cumulative natural selection gives rise to adaptations is, Dennett says, like a “universal acid”—an idea so powerful and corrosive of conventional wisdom that it dissolves all attempts to contain it within biology. Like most good ideas, this one is very simple: Once replicators (material objects that are faithfully copied) come to exist, some will replicate more rapidly than others, leading to adaptation by natural selection. (...) The great power of the idea is that the resulting adaptations can be understood by asking what leads to efficient, rapid replication. Given that ideas seem to replicate, it is natural that Dawkins (1976, 1982), Dennett (1992), and others have explored the possibility of using this idea to explain cultural evolution. (shrink)

Indirect reciprocity occurs when the cooperative behavior between two individuals is contingent on their previous behavior toward others. Previous theoretical analysis indicates that indirect reciprocity can evolve if individuals use an image-scoring strategy. In this paper, we show that, when errors are added, indirect reciprocity cannot be based on an image-scoring strategy. However, if individuals use a standing strategy, then cooperation through indirect reciprocity is evolutionarily stable. These two strategies differ with respect to the information to which they attend. While (...) image-scoring strategies only need attend to the actions of others, standing strategies also require information about intent. We speculate that this difference may shed light on the evolvability of indirect reciprocity. Additionally, we show that systems of indirect reciprocity are highly sensitive to the availability of information. Finally, we present a model which shows that if indirect reciprocity were to evolve, selection should also favor trusting behavior in relations between strangers. r 2003 Elsevier Ltd. All rights reserved. (shrink)

It is almost 30 years since the sociobiology controversy burst into full bloom. The modern theory of the evolution of animal behavior was born in the mid 1960’s with Bill Hamilton’s seminal papers on inclusive fitness and George William’s book Adaptation and Natural Selection. The following decade saw an avalanche of important ideas on the evolution of sex ratio, animal conflicts, parental investment, and reciprocity, setting off a revolution our understanding of animal societies, a revolution that is still going on (...) today. By the mid-1970’s, Richard Alexander, E. O. Wilson, Napoleon Chagnon, Bill Irons, and Don Symons among others began applying these ideas to understand human behavior. Humans are evolved creatures, and quite plausibly the same evolutionary forces that shaped the behavior of other animals also molded our behavior. Moreover, the new theory of animal behavior—especially, kin selection, parental investment, and optimal foraging theory—seemed fit the data on human societies fairly well. (shrink)

Biology and the social sciences share an interest in phylogeny. Biologists know that living species are descended from past species, and use the pattern of similarities among living species to reconstruct the history of phylogenetic branching. Social scientists know that the beliefs, values, practices, and artifacts that characterize contemporary societies are descended from past societies, and some social science disciplines, linguistics and cross cultural anthropology for example, have made use of observed similarities to reconstruct cultural histories. Darwin appreciated that his (...) theory of descent with modification had many similarities of pattern and process to the already well developed field of historical linguistics. In many other areas of social science, however, phylogenetic reconstruction has not played a central role. (shrink)

Recent investigations have uncovered large, consistent deviations from the predictions of the textbook representation of Homo economicus (Roth et al, 1992, Fehr and Gächter, 2000, Camerer 2001). One problem appears to lie in economists’ canonical assumption that individuals are entirely self-interested: in addition to their own material payoffs, many experimental subjects appear to care about fairness and reciprocity, are willing to change the distribution of material outcomes at personal cost, and reward those who act in a cooperative manner while punishing (...) those who do not even when these actions are costly to the individual. These deviations from what we will term the canonical model have important consequences for a wide range of economic phenomena, including the optimal design of institutions and contracts, the allocation of property rights, the conditions for successful collective action, the analysis of incomplete contracts, and the persistence of noncompetitive wage premia. Fundamental questions remain unanswered. Are the deviations from the canonical model evidence of universal patterns of behavior, or do the individual’s economic and social environments shape behavior? If the latter, which economic and social conditions are involved? Is reciprocal behavior better explained statistically by individuals’ attributes such as their sex, age, or relative wealth, or by the attributes of the group to which the individuals belong? Are there cultures that approximate the canonical account of self-regarding behavior? Existing research cannot answer such questions because virtually all subjects have been university students, and while there are cultural differences among student populations throughout the world, these differences are small compared to the range of all social and cultural environments. To address the above questions, we and our collaborators undertook a large cross-cultural study of behavior in ultimatum, public good, and dictator games.. (shrink)

Darwin believed that his theory of evolution would stand or fall on its ability to account for human behavior. No species could be an exception to his theory without imperiling the whole edifice. The ideas in the Descent of Man were widely discussed by his contemporaries although they were far from being the only evolutionary theories current in the late nineteenth century. Darwin's specific evolutionary ideas and those of his main followers had very little impact on the social sciences as (...) they emerged as separate disciplines in the early Twentieth Century. Not until the late twentieth century were concerted, sophisticated efforts made to apply Darwinian theory to human behavior. Why such a long delay? We argue that Darwin's theory was rather modern in respects that conflicted with Victorian sensibilities and that he and his few close followers failed to influence any of the social sciences. The late Twentieth Century work takes up almost exactly where James Baldwin left off at the turn of the century. (shrink)

Two kinds of factors set the tempo and direction of organic and cultural evolution, those external to biotic evolutionary process, such as changes in the earth’s physical and chemical environments, and those internal to it, such as the time required for chance factors to lead lineages across adaptive valleys to a new niche space (Valentine 1985). The relative importance of these two sorts of processes is widely debated. Valentine (1973) argued that marine invertebrate diversity patterns responded to seafloor spreading as (...) this process generated more or less niche space. He suggested that natural selection is a powerful force and that earth’s biota are in near equilibrium with the niches available on the geological time scale. Walker and Valentine (1984) modeled the evolution of species assuming a logistic speciation rate limited by internal factors and a diversity-independent death rate caused by ongoing environmental change. Fitting this model to the observed evolution of shelled marine invertebrates suggests that the lag between extinctions and the evolution of new species leaves perhaps 30% of ecological niches unfilled. In this model, the biota lag environmental change by perhaps a few million years. However, as Valentine (1985) notes, if adaptive landscapes have whole suites of niches protected by deep maladaptive valleys, the waiting time for some pioneering species to cross the divide may be very long, generating the rare events that set new body plans and generate major adaptive radiations. Eldredge and Gould (1972) and Gould (2002) championed the idea that internal processes such as genetic and developmental constraints, coupled with the complexity of the adaptive landscape, resulted in a highly historically contingent evolutionary process. On Gould’s account, most of the history of life had to do not with a relatively close tracking of a changing environment but with the halting evolutionary exploration a deeply fissured niche space, mostly by rapid bursts of evolution as a fissure was crossed, followed by long periods of stasis.. (shrink)

We review the evolutionary theory relevant to the question of human cooperation and compare the results to other theoretical perspectives. Then, we summarize some of our work distilling a compound explanation that we believe gives a plausible account of human cooperation and selfishness. This account leans heavily on group selection on cultural variation but also includes lower-level forces driven by both microscale cooperation and purely selfish motives. We propose that innate aspects of human social psychology coevolved with group-selected cultural institutions (...) to produce just the kinds of social and moral faculties originally proposed by Darwin. We call this the “tribal social instincts” hypothesis. The account is systemic in the sense that human social systems are functionally differentiated, conflicted, and diverse. A successful explanation of human cooperation has to account for these complexities. For example, a tribal-scale cultural group selection process alone cannot account for human patterns of cooperation because, on one hand, much conflict exists within tribes and, on the other, people have proven able to organize cooperation on a much larger scale than tribes. We include multilevel selection and gene–culture coevolution effects to account for some of these complexities and discuss empirical tests of the resulting hypotheses. In particular, we argue that strong support for the tribal social instincts hypothesis comes from the structure of modern social institutions. These institutions have conspicuous “work-arounds” that shed light on the underlying instincts. (shrink)

Is society an organic whole with each of its many components working together like the organs in a body? Like organisms, societies are composed of many parts which seem to work together enhance their survival. Different people fulfill different, necessary role—subsistence, reproduction, coordination, and defense. Regular exchange of matter and energy guarantees that each component has the resources it needs. Norms, laws and customs regulate virtually every aspect of social interaction, who may marry who, how disputes are resolved, and how (...) verbs should be conjugated. Ritual and religion provide comfort to the sick and fearful, maintain a feeling of solidarity and belonging, and serve to preserve and transmit knowledge through time. Even the simplest human societies seem like complex machines designed for growth and survival. (shrink)

Experiments are not models of cooperation; instead, they demonstrate the presence of the ethical and other-regarding predispositions that often motivate cooperation and the punishment of free-riders. Experimental behavior predicts subjects' cooperation in the field. Ethnographic studies in small-scale societies without formal coercive institutions demonstrate that disciplining defectors is both essential to cooperation and often costly to the punisher.

Version 4.4 October, 1994 Introduction When explaining human behavior, anthropologists frequently distinguish the things that people do of their own free will from the things they do because they have to. In much of anthropology, and most American archaeology, this is the difference between style and function. Functional behaviors are the things people are constrained to do; stylistic behaviors are the things people do when unconstrained. Where necessity stops and free choice begins is, of course, a classic problem of social (...) science theory, but wherever the boundary is placed, it is generally implied that the domains thus divided are not of equal importance (Bettinger 1991:49-50). Few straddle this fence: Materialists emphasize function and downplay style; structuralists and postmodernists do the opposite. Recent attempts to apply neo- Darwinian concepts to the archaeological record predictably side with materialist tradition, repeating the premise that it is most important to explain functional behavior; stylistic behavior is interesting only for localizing social units in time and space. (shrink)

The iterated prisoner’s dilemma (IPD) has been widely used in the biological and social sciences to model dyadic cooperation. While most of this work has focused on the discrete prisoner’s dilemma, in which actors choose between cooperation and defection, there has been some analysis of the continuous IPD, in which actors can choose any level of cooperation from zero to one. Here, we analyse a model of the continuous IPD with a limited strategy set, and show that a generous strategy (...) achieves the maximum possible payoff against its own type. While this strategy is stable in a neighborhood of the equilibrium point, the equilibrium point itself is always vulnerable to invasion by uncooperative strategies, and hence subject to eventual destabilization. The presence of noise or errors has no effect on this result. Instead, generosity is favored because of its role in increasing contributions to the most efficient level, rather than in counteracting the corrosiveness of noise. Computer simulation using a single-locus infinite alleles Gaussian mutation model suggest that outcomes ranging from a stable cooperative polymorphism to complete collapse of cooperation are possible depending on the magnitude of the mutational variance. Also, making the cost of helping a convex function of the amount of help provided makes it more difficult for cooperative strategies to invade a non-cooperative equilibrium, and for the cooperative equilibrium to resist destabilization by noncooperative strategies. (shrink)

This chapter focuses on the way that cultures change and how cultural diversity is created, maintained and lost. Human culture is the inevitable result of the way our species acquires its behavior. We are extremely social animals and an overwhelming proportion of our behavior is socially learned. The behavior of other animals is largely a product of innate evolved determinants of behavior combined with individual learning. They make quite modest use of social learning while we acquire a massive cultural repertoire (...) from the people we associate with (Richerson & Boyd, 2005: Chapter 2). Expertise in exploiting our environment, values about what matters in life and even feelings about whom to trust and whom to hate are mostly “absorbed” from those around us. (shrink)