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.

Human cooperation is highly unusual. We live in large groups composed mostly of non-relatives. Evolutionists have proposed a number of explanations for this pattern, including cultural group selection and extensions of more general processes such as reciprocity, kin selection, and multi-level selection acting on genes. Evolutionary processes are consilient; they affect several different empirical domains, such as patterns of behavior and the proximal drivers of that behavior. In this target article, we sketch the evidence from five domains that bear on (...) the explanatory adequacy of cultural group selection and competing hypotheses to explain human cooperation. Does cultural transmission constitute an inheritance system that can evolve in a Darwinian fashion? Are the norms that underpin institutions among the cultural traits so transmitted? Do we observe sufficient variation at the level of groups of considerable size for group selection to be a plausible process? Do human groups compete, and do success and failure in competition depend upon cultural variation? Do we observe adaptations for cooperation in humans that most plausibly arose by cultural group selection? If the answer to one of these questions is “no,” then we must look to other hypotheses. We present evidence, including quantitative evidence, that the answer to all of the questions is “yes” and argue that we must take the cultural group selection hypothesis seriously. If culturally transmitted systems of rules that limit individual deviance organize cooperation in human societies, then it is not clear that any extant alternative to cultural group selection can be a complete explanation. (shrink)

Recent debates about memetics have revealed some widespread misunderstandings about Darwinian approaches to cultural evolution. Drawing from these debates, this paper disputes five common claims: (1) mental representations are rarely discrete, and therefore models that assume discrete, gene-like particles (i.e., replicators) are useless; (2) replicators are necessary for cumulative, adaptive evolution; (3) content-dependent psychological biases are the only important processes that affect the spread of cultural representations; (4) the “cultural fitness” of a mental representation can be inferred from its successful (...) transmission; and (5) selective forces only matter if the sources of variation are random. We close by sketching the outlines of a unified evolutionary science of culture. (shrink)

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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)

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

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..

Evolutionary theory relevant to the question of human cooperation is reviewed and compared to other theoretical perspectives. A compound explanation is distilled as 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 micro-scale cooperation and purely selfish motives. It is proposed 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. This is termed 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. Multilevel selection and gene-culture coevolution effects are included to account for some of these complexities and empirical tests of the resulting hypotheses are discussed. In particular, it is argued 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)

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)

Human social life is uniquely complex and diverse. Much of that complexity consists of culturally transmitted ideas and skills that underpin the operation of institutions that structure our social life. Considerable theoretical and empirical work has been devoted to the role of cultural evolutionary processes in the evolution of institutions. The most persistent controversy has been over the role of cultural group selection and gene-culture coevolution in early human populations the Pleistocene. We argue that cultural group selection and related cultural (...) evolutionary processes had an important role in shaping the innate components of our social psychology. By the Upper Paleolithic humans seem to have lived in societies structured by institutions, as do modern populations living in simple societies. The most ambitious attempts to test these ideas have been the use of experimental games in field settings to document human similarities and differences on theoretically interesting dimensions. These studies have documented a huge range of behavior cross-culturally, although no societies so far examined follow the expectations of selfish rationality. These data are at least consistent with operation of cultural group selection and gene-culture coevolution operating in the deep tribal past and with the contemporary importance of cultural evolution in the evolution of institutions and institutional diversity. (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)

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)

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 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)

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

Version 3.0 12/02/00. Submitted to R.M. Nesse The Evolution of Subjective Commitment, Russell Sage Foundation. Please do not cite without author’s permission.  by Peter J. Richerson and Robert Boyd. Comments welcome! Word count 14,487.

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)

Demography plays a large role in cultural evolution through its effects on the effective rate of innovation. If we assume that useful inventions are rare, then small isolated societies will have low rates of invention. In small populations, complex technology will tend to be lost as a result of random loss or incomplete transmission (the Tasmanian effect). Large populations have more inventors and are more resistant to loss by chance. If human populations can grow freely, then a population-technology-population positive feedback (...) should occur such that human societies reach a stable growth path on which the rate of growth of technology is limited by the rate of invention. This scenario fits the Holocene to a first approximation, but the late Pleistocene is a great puzzle. Large-brained hominins existed in Africa and west Eurasia for perhaps 50,000 years with, at best, slow rates of technical innovation. The most sophisticated societies of the last glacial period appear after 50,000 years ago and were apparently restricted to west and north-central Eurasia and North Africa. These patterns have no simple, commonly accepted explanation. We argue that increased high-frequency climate change around 70,000–50,000 years ago may have tipped the balance between humans and their competitor-predators, such as lions and wolves, in favor of humans. At the same time, technically sophisticated hunters would tend to overharvest their prey. Perhaps the ephemeral appearance of complex tools and symbolic artifacts in Africa after 00,000 years ago resulted from hunting inventions that allowed human populations to expand temporarily before prey overexploitation led to human population and technology collapse. Sustained human populations of moderate size using distinctively advanced Upper Paleolithic artifacts may have existed in west Eurasia because cold, continental northeastern Eurasia–Beringia acted as a protected reserve for prey populations. (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)

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)

Experiments may contribute to understanding the basic processes of cultural evolution. We drew features from previous laboratory research with small groups in which traditions arose during several generations. Groups of four participants chose by consensus between solving anagrams printed on red cards and on blue cards. Payoffs for the choices differed. After 12 min, the participant who had been in the experiment the longest was removed and replaced with a naı¨ve person. These replacements, each of which marked the end of (...) a generation, continued for 10 – 15 generations, at which time the day’s session ended. Time-out duration, which determined whether the group earned more by choosing red or blue, and which was fixed for a day’s session, was varied across three conditions to equal 1, 2, or 3 min. The groups developed choice traditions that tended toward maximizing earnings. The stronger the dependence between choice and earnings, the stronger was the tradition. Once a choice tradition evolved, groups passed it on by instructing newcomers, using some combination of accurate information, mythology, and coercion. Among verbal traditions, frequency of mythology varied directly with strength of the choice tradition. These methods may be applied to a variety of research questions. D 2004 Elsevier Inc. All rights reserved. (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)

Ongoing advances in paleoclimatology and paleoecology are producing an ever more detailed picture of the environments in which our species evolved. This picture is important to understanding the processes by which our large brain evolved. Our large brain and its productions—toolmaking, complex social institutions, language, art, religion—are our most striking differences from our closest living relatives. Indeed, humans are unique in the animal world for our brain size relative to body mass and in the elaboration of our cultures. We are (...) also the world’s dominant organism (Vitousek et al. 1997). We achieved our present anatomy and behavioral repertoire very recently. Fossil material attributable to our species goes back perhaps 200,000 years and artifacts that strike us as representing fully modern behavioral capacities are only about 50,000 years old (Klein 1999; McBrearty and Brooks 2000), about which time anatomically modern humans spread from Africa to Eurasia (Lahr and Foley 1994). Our ecological dominance began with the evolution of agriculture starting about 10,000 years ago. Explaining the late coming of human brains is a major evolutionary puzzle. Most important animal adaptations are old. Eyes, internal skeletons, adaptations for terrestrial life and for flight all date back hundreds of millions of years. Given that big brains and culture were such an overwhelming success for us why didn’t they evolve long ago? (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)

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)

MOST MODERN PEOPLE think it is obvious why people become modern. For them, a more interesting and important puzzle is why some people fail to embrace modern ideas. Why do people in traditional societies often seem unable or unwilling to aspire to a better life for themselves and their children? Why do they fail to see the benefi ts of education, equal rights, democracy, and a rational approach to decisionmaking? What is the glue that makes them adhere to superstition, religion, (...) and obligations to family and tribe even if it means accepting a life of insecurity and poverty? The “kin infl uence hypothesis” (Newson et al. 2005) suggests an explanation both for why people become modern and for why modern ideas are often slow to be accepted by a population. The hypothesis is based on the understanding gained by social-psychological research of how cultural norms change. It takes a Darwinian approach to explaining human behavior and recognizes that much of the cultural change associated with modernization is a progressive abandonment of values and norms that encourage people to pursue what evolutionary theorists refer to as “reproductive success.”1 The kin infl uence hypothesis proposes that the cascade of cultural changes associated with modernization is the result of the momentous change in the human social environment that occurs early in economic development. For most of human evolutionary history, the norms of all cultures must have prescribed behavior that, on balance, enhanced the genetic fi tness of their members. If this were not the case, then, as Lumsden and Wilson (1981) and Alexander (1979) rightly pointed out, evolutionary biologists would be unable to explain how humans evolved the uniquely human capacity for learning and imitation that makes culture possible. Nor could we explain how an African ape came to be the world’s dominant organism. With economic development, however, people begin to abandon the beliefs and values that encourage fi tness-enhancing behavior.. (shrink)

The existence of social learning has been confirmed in diverse taxa, from apes to guppies. In order to advance our understanding of the consequences of social transmission and evolution of behavior, however, we require statistical tools that can distinguish among diverse social learning strategies. In this paper, we advance two main ideas. First, social learning is diverse, in the sense that individuals can take advantage of different kinds of information and combine them in different ways. Examining learning strategies for different (...) information conditions illuminates the more detailed design of social learning. We construct and analyze an evolutionary model of diverse social learning heuristics, in order to generate predictions and illustrate the impact of design differences on an organism’s fitness. Second, in order to eventually escape the laboratory and apply social learning models to natural behavior, we require statistical methods that do not depend upon tight experimental control. Therefore we examine strategic social learning in an experimental setting.. (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)

Summary: The evolution of complex societies began when agricultural subsistence systems raised human population densities to levels that would support large scale cooperation, and division of labor. All agricultural origins sequences postdate 11,500 years ago probably because late Pleistocene climates we extremely variable, dry, and the atmosphere was low in carbon dioxide. Under such conditions, agriculture was likely impossible. However, the tribal scale societies of the Pleistocene did acquire, by geneculture coevolution, tribal social instincts that simultaneously enable and constrain the (...) evolution of complex societies. Once agriculture became possible, a competitive ratchet drove further improvements in subsistence and in scale of social organization . Those societies that grew and became better organized were advantaged in individual wealth and economic and military power, and tended to conquer, absorb, or be imitated by smaller and less well organized societies. Internal competitors for power espousing useful social innovations could deliver improved returns when their quest was successful. Notwithstanding the ratchet, social complexity increased only slowly in the first half of the Holocene and even afterwards few periods except the past two centuries saw changes that were dramatic on the scale of individual lifetimes. We attempt a taxonomy of the processes that regulate rates of institutional evolution, cause reversals of complexity against the ratchet, and impose historical contingency on institutional evolution. (shrink)

Recently, several authors have argued that the Pleistocene climatic fluctuations are responsible for the evolution of human anatomy and cognition. This hypothesis contrasts with the common idea that human language, tools, and culture represent a revolutionary breakthrough rather than a conventional adaptation to a particular ecological niche. Neither hypothesis is satisfactory. The “Pleistocene hypothesis”, as proposed, does not explain how Pleistocene fluctuations favor the particular adaptations that characterize humans. The alternative hypothesis does not explain what has prevented many animal lineages (...) in the remote past from evolving a similar adaptive complex of tools, language and culture. Theoretical models of the cultural evolutionary process suggest some answers to these questions. Learning, including social learning, is rather generally a useful adaptation in variable environments. The progressive brain enlargement in many mammalian lineages during the last few million years suggests that climatic deterioration has had the general effect predicted by the Pleistocene hypothesis. Increased dependence on simple social learning was a preadaptation to the evolution of a capacity for complex traditions. The evolution of a costly capacity to acquire complex traditions is inhibited because, initially, complex traditions will be rare. Having the capacity to learn things that are far too complex to invent for oneself is not useful until traditions are common, but traditions cannot become complex before the capacity to acquire them is common. This problem may explain why many animals became more sophisticated learners in the Pleistocene, but why complex, cumulative cultural traditions are so rare. The history of our lineage must have included unique preadaptations that permitted us to evade the useless-when-rare problem. (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)

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)

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)

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)

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)

Human syntactic language has no close parallels in other systems of animal communication. Yet it seems to be an important part of the cultural adaptation that serves to make humans the earth’s dominant organism. Why is language restricted to humans given that communication seems to be so useful? We argue that language is part of human cooperation. We talk because others can normally trust what we say to be useful to them, not just to us. Models of gene-culture coevolution give (...) one plausible explanation for how language, cooperative institutions, and the genetic basis for both could have evolved. Why did the coevolutionary process come to rest leaving a huge space for the cultural evolution of language? We argue that language diversity functions to limit communication between people who cannot freely trust one another or where even truthful communications from others would result in maladaptive behavior on the part of listeners. (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.

The debates over the future of human population and the earth’s environment, and similar large issues, usually take place without reference to explicit models. Debate would be clarified if such models were employed. We propose that the logistic equation and its extensions like the generalized logistic and the Lotka-Volterra equations, so familiar to ecologists, can easily be modified to model the important "macro" questions that motivated the three thinkers of our title. The long term rate of population growth must normally (...) be controlled by the rate of improvement in K, the carrying capacity of the earth. K will in turn be controlled by the rate of technological progress. The present situation, in which technological improvement (but also perhaps environmental deterioration) are increasing at rates above r, the Malthusian intrinsic rate of natural increase, is probably unique in human history. Can present levels of human prosperity and population growth be sustained? What processes are most likely to determine the answer to this and similar questions? We here sketch a model that endogenizes technological progress and environmental deterioration in the logistic framework. We discuss extensions of the logistic approach to multiple populations, such as other species, and sub-populations, such as human social classes, using the Lotka-Volterra equations. (shrink)

Modern humans are probably a product of social and anatomical preadaptations on the part of our Miocene australopithecine ancestors combined with the increasingly high amplitude, high frequency climate variation of the Pleistocene. The genus Homo first appeared in the early Pleistocene as ice age climates began to grip the earth. We hypothesize that this co-occurrence is causal. The human ability to adapt by cultural means is, in theory, an adaptation to highly variable environments because cultural evolution can better track rapidly (...) changing environments than can genes. High resolution ice and sediment cores published in the early 1990s showed the last ice age was characterized by high amplitude millennial and submillenial scale variation, exactly the sort of variation mathematical models suggest should favor a costly capacity for culture. More recent cores suggest that over the last several 100 thousand year glacial cycles the amount of millennial scale variation has increased rather dramatically in parallel with increases in hominin brain size and sophistication of the artifacts they made. (shrink)