F264THE ECONOMIC JOURNAL [ AUGUST

Rigdon, M., Ishii, K., Watabe, M. and Kitayama, S. (2009). ÔMinimal social cues in the dictator gameÕ, Journal of Economic Psychology, vol. 30(3), pp. 358–67. Roughgarden, J. (1979). Theory of Population Genetics and Evolutionary Ecology: An Introduction, Upper Saddle River, NJ: Prentice Hall. Silk, J.B., Brosnan, S.F., Vonk, J., Henrich, J., Povinelli, D.J., Richardson, A.S., Lambeth, S.P., Mascaro, J. and Schapiro, S.J. (2005). ÔChimpanzees are indifferent to the welfare of unrelated group membersÕ, Nature, vol. 437(27 October), pp. 1357–9. Smith, E.A. (2000). ÔThree styles in the evolutionary analysis of human behaviorÕ, in (L. Cronk, N. Chagnon and W. Irons eds.), Adaptation and Human Behavior: An Anthropological Perspective, pp. 27–46. New York: Aldine de Gruyter. Smith, E.A., Borgerhoff Mulder, M. and Hill, K. (2011). ÔControversies in the evolutionary social sciences: a guide for the perplexedÕ, Trends in Ecology and Evolution, vol. 16(3), pp. 128–35. Smith, K., Kalish, M.L., Griffiths, T.L. and Lewandowsky, S. (2008). ÔIntroduction: cultural transmission and the evolution of human behaviourÕ, Philosophical Transactions of the Royal Society, B, vol. 363(1509), pp. 3469–76. Stigler, G.J. and Becker, G.S. (1977). ÔDe gustibus non est disputandumÕ, American Economic Review, vol. 67(2), pp. 76–90. Trivers, R.L. (1971). ÔThe evolution of reciprocal altruismÕ, Quarterly Review of Biology, vol. 46(1), pp. 35–57. Williams, G.C. (1966). Adaptation and Natural Selection, Princeton: Princeton University Press. Winterhalder, B. and Smith, E.A., editors (1992). Evolutionary Ecology and Human Behavior, New York: Aldine de Gruyter.

Review 2 1. Can Human Cooperation be Explained by Group Selection? For some years, Samuel Bowles and Herbert Gintis have been working on an extraord- inarily ambitious project that brings together economics, anthropology and biology. In this book, they summarise this work and present their latest thinking about it. As their title suggests, they propose the hypothesis that homo sapiens is a Ôcooperative speciesÕ.By this they mean that, as a result of genetic natural selection, modern human beings are innately predisposed to cooperative behaviour. Bowles and Gintis propose that these cooperative predispositions evolved as adaptations to the natural and social environ- ment in which ancestral humans lived before the development of agriculture. Their project is to try to identify the content of these predispositions and to explain the evolutionary processes by which they were selected. The proposed explanation involves two broad forms of evolutionary theorising – gene– culture co-evolution and multi-level selection. The key idea of gene–culture co-evolution is that if a cultural practice – that is, a practice that is not genetically hard-wired – persists for a sufficiently long time in a sufficiently isolated population, it constitutes a niche in which genetic selection can operate. Thus, alongside the more normal mechanism by which cultural evolution within a population is constrained by that populationÕs genetic endowment, gene pools can adapt to culture. Multi-level selection is the idea that natural selection can work, not only at the level of the individual but also at the level of groups of individuals. As it is uncontroversial that individual selection is a large part of natural selection, the key idea is that group selection played a significant role in the natural selection of human psychology. When thinking about these evolutionary processes, it is essential to keep in mind the distinction between cultural and genetic evolution. The mechanisms of cultural and genetic evolution are isomorphic in important respects, and many of the tools of

2012 The Author(s). The Economic Journal 2012 Royal Economic Society. 2012] BOOK REVIEWS F265 evolutionary game theory are applicable in both contexts. But if the ultimate objective is (as I take it to be for Bowles and Gintis) to explain cooperation in modern human societies, cultural evolution in ancestral societies is relevant only to the extent that it leaves an imprint on the gene pool. Otherwise, we are not entitled to draw inferences about modern cooperation from the social organisation of ancestral societies. That is why gene–culture co-evolution is crucial to Bowles and GinitsÕs argument. Bowles and Gintis start from the experimental evidence, mostly accumulated in the last three decades, of cooperative behaviour in settings such as the PrisonerÕs Dilemma, the Ultimatum game, the Dictator game, the Trust game and the Public Good game (i.e. the game in which a public good is supplied by voluntary individual contributions). They argue, I think correctly, that the balance of evidence disconfirms the hypothesis that individual behaviour in these games can be adequately explained by rational self- interest. The most promising explanatory strategy, they argue, is to assume that indi- viduals are in some way directly motivated to reciprocate one anotherÕs cooperative actions. Bowles and Gintis define ÔcooperationÕ as Ôengaging with others in a mutually beneficial activityÕ and then distinguish between mutualism (where each individual benefits from his own contribution to the cooperative activity) and altruism (where each individualÕs own contribution is a net loss to him, even though he benefits from everyoneÕs contributions taken together) (p. 2). They interpret the experimental evi- dence as showing the existence of altruistic cooperation. I cannot resist pointing out that the hypothesis of altruistic cooperation pre-dates the literature of Ôsocial preferencesÕ on which Bowles and Gintis build. In the early 1980s, I argued that statistical data on charitable donations could not be explained by assuming that donors were altruistically concerned about other peopleÕs welfare. In- stead, I proposed a theory of non-selfish reciprocity in which individuals are moti- vated to reciprocate one anotherÕs contributions (Sugden, 1982, 1984). However, Bowles and Gintis rightly emphasise the significance of the theoretical and experi- mental work of Fehr and Ga¨chter (2000) on altruistic punishment. By the time Fehr and Ga¨chterÕs article was written, it was well known that in repeated experimental Public Good games, contributions are relatively high in early rounds (indicating non- selfishness) but decline sharply as the game is repeated. Fehr and Ga¨chter showed that this decline can be averted if, after each round, each player has the option of incurring a small cost to impose a larger ÔpunishmentÕ cost on any other player, chosen by the punisher. This finding suggests that negative reciprocity may be as important as positive reciprocity in sustaining cooperation. In modelling altruistic cooperation, Bowles and Gintis favour the general approach of assuming optimising behaviour by individuals and modelling non-selfish motivations as ÔsocialÕ preferences but that is justified only as a convenient modelling strategy (p. 9). Beyond this, they are not choosy. They seem to endorse just about every current theory of social preference: People cooperate not only for self-interested reasons, but also because they are genuinely concerned about the well-being of others, try to uphold social norms, and value behaving ethically for its own sake. People punish those who exploit the cooperative behaviour of others for the same reasons. Contributing

2012 The Author(s). The Economic Journal 2012 Royal Economic Society. F266THE ECONOMIC JOURNAL [ AUGUST to the success of a joint project for the benefit of oneÕs group, even at a personal cost, evokes feelings of satisfaction, pride, even elation. Failing to do so is often a source of shame or guilt (p. 1). The problem that Bowles and Gintis set themselves is to explain Ôwhy the social preferences that sustain altruistic cooperation are so commonÕ. They immediately translate this into a question about natural selection. As (they claim) Ôproximate an- swersÕ are to be found in the ways that human brains work, the relevant question becomes: ÔBut how did we come to have brains that function in this manner?Õ (p. 3). This requires a study of the Late Pleistocene environment to which human brains are presumably adapted. Given that this is their strategy, it is surprising that Bowles and Gintis do not point to any direct evidence that the non-selfish motivations they have identified are hard-wired. Indeed, they discuss evidence of cultural variation in non-selfish behaviour that appears to suggest the contrary. One body of such evidence comes from a cross-cultural experimental study of punishment by Herrmann et al. (2008). It is now widely recog- nised that Fehr and Ga¨chterÕs original experimental setup provided unrealistically favourable conditions for altruistic punishment by not giving punishers direct oppor- tunities to retaliate against their punishers. (Casual observation suggests to me that fear of retaliation is a major deterrent to the gratuitous punishment of violations of social norms in public places – at least in Britain, if not in Fehr and Ga¨chterÕs Switzerland.) Subsequent experiments have found that, in some settings, opportunities for Ôanti- social punishmentÕ (perhaps better thought of as retaliation or revenge) lead to ven- detta-like patterns of behaviour. Herrmann et al. find that in some subject pools (e.g. in Boston, Melbourne and Zurich), retaliation opportunities do not compromise the mechanism of altruistic punishment but in other pools (e.g. in Muscat, Athens and Riyadh) they clearly do. Another example (not discussed by Bowles and Gintis) is a cross-cultural study of the Ultimatum, Dictator and Third Party Punishment games, played in 15 diverse small-scale Third World societies. This study finds a large amount of cross-cultural variation. Significantly, cooperative behaviour in these games is posit- ively associated with a societyÕs integration into the market economy and with its participation in a world religion (Henrich et al., 2010). These studies suggest that altruistic cooperation, as identified in the familiar experiments, may be as much a cultural phenomenon as a manifestation of hard-wired properties of human psycho- logy. So it is not self-evident that Bowles and Gintis are looking in the right place for an answer to the problem they have set themselves. Bowles and Gintis pursue their investigation by identifying the characteristic features of cooperation in ancestral societies. I have no expertise in anthropology but their generalisations are credible and broadly consistent with my limited reading on this topic – in particular, a very convincing review of the evidence on food sharing written by Kaplan and Gurven (2005). It seems clear that our species is biologically adapted to a mode of life that could not be sustained without a high degree of social cooperation. Our niche is that of foragers of nutrient-dense foods that can be acquired only by methods that require the coordinated actions of individuals with difficult-to-learn skills. Probably because of this, humans have an exceptionally long period of juvenile dependency. This necessitates much more food-sharing than in other great ape species,

2012 The Author(s). The Economic Journal 2012 Royal Economic Society. 2012] BOOK REVIEWS F267 effectively requiring fathers, mothers and older siblings to cooperate in the care and provisioning of children. Because of natural variation in the number of children in a family and the inevitable variability of the returns from hunting large prey, some food- sharing networks need to be wider than the immediate family. The characteristic ancestral form of social organisation was of families living together in loose bands. The boundaries of these bands were fluid, with seasonal agglomerations and frequent movements of families between bands. Exogamy, which is a biological essential, entails individual migration (and therefore also kinship links) across band boundaries. Relations between bands involved a mix of reciprocity, kinship alliances, long-distance trade and lethal warfare. Within bands, there was cooperation within families, between families, and at the level of the whole band. Bowles and Gintis argue convincingly that this pattern of cooperation cannot be explained solely by kin-specific altruism. I was less persuaded by their claim that it cannot be explained by a combination of kin altruism and self-interested reciprocity (i.e. reciprocity based on the long-term self-interest of the respective parties). Their argument relies heavily on non-cooperative game-theoretic models, such as repeated many-person Public Good games, in which the players are not grouped into coalitions. Bowles and Gintis are right to say that in that modelling framework, self-interested reci- procity cannot easily sustain multilateral cooperation in large groups. But the evidence of food-sharing in hunter-gatherer societies indicates that when an individual acquires a large amount of food, for example, as a successful hunter, the redistribution favours that individualÕs kin and those who have previously shared with him (Kaplan and Gurven, 2005, p. 83). That suggests that the models that Bowles and Gintis are using are too simple, not that the hypothesis of self-interested reciprocity is false. (One way of enriching the models might be to allow for reciprocity between coalitions.) Bowles and Gintis give particular emphasis to the problem of explaining what they interpret as practices of punishment within bands. The evidence seems clear that rela- tionships between adults of the same sex were highly egalitarian. Attempts by individuals to assert dominance were not tolerated, and persistent inequalities of consumption were countered by social demands for sharing or gift-giving. Bossiness, stinginess and laziness were all censured. However, the mechanism of censure was not at all like the altruistic punishment modelled by Fehr and Ga¨chter. Typically, an individual did not take it into his own hands to punish a violation of a social norm, unless that violation had been specifically directed at him or his family. The most common forms of communal pun- ishment were coordinated ridicule and hostile gossip. For these mechanisms to work, the person who is punished must feel aversion to being the target of general resentment. But there is no obvious need for altruism on the part of the punishers; the psychology that is most obviously implicated is emotional contagion. More extreme punishments – which could involve coordinated killings – seem to have been organised in ways that minimised the cost and danger to any individual punisher. Bowles and GintisÕs preferred explanation of cooperation relies on genetic group selection. But because of the looseness of group boundaries and the extent of inter- group gene flow necessitated by exogamy, the social organisation of ancestral human life seems highly unfavourable to such selection. Indeed, in an article co-authored with Robert Boyd and Peter Richerson, Bowles and Gintis have made the same point (Boyd et al., 2005, p. 226). In A Cooperative Species, Bowles and Gintis try to allay these doubts by 2012 The Author(s). The Economic Journal 2012 Royal Economic Society. F268THE ECONOMIC JOURNAL [ AUGUST presenting a series of abstract game-theoretic models of simple societies in which, given specific parameters, multi-level selection allows altruistic traits to be reproduced. It is difficult for a non-expert reader to assess the applicability of these models to the realities of human life in the Late Pleistocene. I can only say that, other things being equal, I would have more confidence in a theory that did not have to invoke genetic group selection. So what is the alternative? Group selection is much less problematic in relation to the cultural evolution of ancestral societies. Cultural practices can change much more rapidly than gene pools and, although new entrants to a group keep their natal genes, they can be acculturated to new behavioural norms. Thus, cultural variation between groups can be preserved more easily than genetic variation (Boyd et al., 2005, p. 226). Given that both inter-band warfare and selective migration of families between bands are potential mechanisms of cultural group selection, we might expect the organisation of ancestral human societies to be a reasonably efficient solution to the collective action problems they faced, given the hard-wired properties of human psychology (as it was then, and as it still is now). We might also expect to be able to explain those properties in terms of individual and kin selection, given the general characteristics of ancestral societies. In other words, we should expect humans to be endowed with traits that promoted the interests of themselves and their closest kin in a social environment in which cooperation with non-kin was an essential of survival but in which conflicts of interest constantly needed to be resolved. Such traits would surely include empathy, emotional intelligence and susceptibility to emotional contagion. (The Ôperception–actionÕ model presented by Preston and de Waal (2002) is a beautifully parsimonious explanation of the adaptive value of emo- tional contagion for social animals.) Other individually adaptive traits might include alertness to opportunities for mutually beneficial engagement with others, a predis- position to resent being taken advantage of, and an inhibition towards actions that invoke other peopleÕs resentment. I have yet to be convinced that ancestral human societies needed more than this in order to reproduce themselves. So yes, homo sapiens is a cooperative species. In not adequately recognising this fact, rational-choice theories of human interaction are impoverished. But that is not to say that modern human beings are hard-wired to be altruistically cooperative, still less to be altruistic punishers.

Robert Sugden

School of Economics, University of East Anglia

References Boyd, R., Gintis, H., Bowles, S. and Richerson, P.J. (2005). ÔThe evolution of altruistic punishmentÕ, in (H. Gintis, S. Bowles, R. Boyd and E. Fehr, eds.), Moral Sentiments and Material Interests: The Foundations of Cooperation in Economic Life, pp. 215–27, Cambridge, MA: The MIT Press. Fehr, E. and Ga¨chter, S. (2000). ÔCooperation and punishmentÕ, American Economic Review, vol. 90, pp. 980–94. Henrich, J., Ensminger, J., McElreath, R., Barr, A., Barrett, C., Bolyanatz, A., Camilo Cardenas, J., Gurven, M., Gwako, E., Henrich, N., Lesorogol, C., Marlowe, F., Tracer, D. and Ziker, J. (2010). ÔReligion, community size, and the evolution of fairness and punishmentÕ, Science, vol. 327(5972), pp. 1480–4.

2012 The Author(s). The Economic Journal 2012 Royal Economic Society. 2012] BOOK REVIEWS F269

Herrmann, B.H., Tho¨ni, C. and Ga¨chter, S. (2008). ÔAnti-social punishment across societiesÕ, Science, vol. 319, pp. 1362–7. Kaplan, H. and Gurven, M. (2005). ÔThe natural history of human food sharing and cooperation: a review and a new multi-individual approach to the negotiation of normsÕ, in (H. Gintis, S. Bowles, R. Boyd and E. Fehr, eds.), Moral Sentiments and Material Interests: The Foundations of Cooperation in Economic Life, pp. 75– 113, Cambridge, MA: The MIT Press. Preston, S.D. and de Waal, F.B.M. (2002). ÔEmpathy: its ultimate and proximate basesÕ, Behavioral and Brain Sciences, vol. 25, pp. 1–72. Sugden, R. (1982). ÔOn the economics of philanthropyÕ, Economic Journal, vol. 92, pp. 341–50. Sugden, R. (1984). ÔReciprocity: the supply of public goods through voluntary contributions,Õ Economic Journal, vol. 94, 772–87. doi: 10.1111/j.1468-0297.2012.02539.x

2012 The Author(s). The Economic Journal 2012 Royal Economic Society.