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J Econ (2011) 104:191–194 DOI 10.1007/s00712-011-0237-5 BOOK REVIEW Bowles, S. and Gintis, H.: A cooperative species—human reciprocity and its evolution 288pp, Princeton University Press, Princeton and Oxford 2011, Hardback, e24.35 Werner Güth Published online: 27 August 2011 © Springer-Verlag 2011 The authors consider homo sapiens as “A Cooperative Species”. What I like about this is that it allows for continuity in the sense that also ape species, our close relatives in the animal kingdom, are “cooperative species”. Thinking of genocides, e.g. in the form of building concentration camps to murder millions of people, should make it clear that “cooperative” is a rather neutral quality—we often “cooperate” in doing good as well as in causing harm. The book offers a rich account of biological, anthropological, experimental findings which render its reading undoubtedly worthwhile. The question is, however, whether the authors are rather eclectic in reporting evidence and when explaining what they report. And one is left alone when asking oneself how is “cooperation” related to specialization and labor division which is so highly developed in homo sapiens, what, of course, presupposes some trading group exceeding the size of families. But let us first describe what the book offers. Chapter 1 elaborates on what is actually meant by “A Cooperative Species”, namely that we “are genuinely concerned about the well-being of others, try to uphold social norms, and value behaving ethically for its own sake” (p. 1) and that this is so because our (human) ancestors lived in habitats where such qualities were fitness enhancing. Actually, the main idea is that they existed in groups of “individuals who were predisposed to cooperate and uphold ethical norms” (p. 1). Inclinations to care for group welfare are justified as being evolutionarily stable since phenotypes with such inclinations protect themselves by ostracizing those without such inclinations, since such inclinations become intrinsic once over a lifetime, and since groups compete with other groups in order to maintain or even enlarge their habitat. What is less clear is whether such structural aspects also apply to some other species. We should be afraid of a hindsight bias, e.g. in the sense of assuming that what we know has happened, had to happen? W. Güth (B) Max Planck Institute of Economics, Jena, Germany e-mail: [email protected] 123 192 W. Güth After briefly mentioning the normative approach to decision making, based on preferences, beliefs and constraints (action space), Chapter 2 propagates the idea of social preferences, specifically altruism. As experimental evidence, the authors mention results of one-shot prisoners’ dilemma games for which appropriately defined altruism can render mutual cooperation an equilibrium outcome. What “evolution” means is then more clearly discussed in the section on “Genes Culture, Groups, and Institutions”. The authors refer to gene-culture coevolution where, of course, genetic adaptation is slow compared to the tremendous speed of cultural evolution in mankind. “The parallel between cultural and biological evolution” (p.15) is more difficult to buy, especially since cultural adaptation often relies on institutional prerequisites (schools, universities,. . .). Regarding genetic evolution one would have liked to see a convincing argument how and why human intelligence could evolve and why we use this intelligence to bother about the well-being of those in the same group and to harm those in other groups. Chapter 3 propagates “Social preferences” in the sense of reciprocity inclination or responding in kind. The concept was studied in (social) psychology long before its more recent discussion in experimental economics employing punishment games or trust-and-reward games. The evidence is often very interesting, especially when cross-cultural effects are reported (Section 3.8) where—as often in so-called crosscultural/country studies—one misses the comparison with intra-cultural/country variance. Interestingly enough, when played repeatedly using a partners design, the evidence is rather uncomforting since cooperation is declining. What this shows is that without punishment institutions like veto power in the ultimatum game, cooperation is endangered. Could one not argue: we are not intrinsically concerned about others’ well-being but we are clever enough to develop emotional reactions that make us reciprocate? Actually, when in an ultimatum experiment having to wait before reacting to an unfair proposal, the rejection rate is smaller than when responding impulsively. It very much depends on circumstances how reciprocal we are. Couldn’t it be that we have developed a very flexible behavioral repertoire of which “cooperativeness” is only one option? Social preferences in the narrower sense of neoclassical economics can easily be shown (analytically) to be evolutionarily stable when certain conditions prevail: if changing the own preference type is somehow noticeable by others, this change does not only affect the own behavior but also that of others who are noticing this change. Partitioning society such that “group” sizes are small could imply such effects. Chapter 4 discusses the “socio-biology” of evolution. What it essentially propagates is to give up the standard assumption of unbiased random matching. It is well known that in case of sufficiently strong associative matching cooperative behavior can evolve. Although associative rather than random matching is the generic case, assuming that a species is substructured in groups may mean to throw out the baby with the bath water. To maintain one species of all, there has to be migration. To justify the claim of methodological individualism, one would like to hear a story how such a group structure results from individual choices, e.g. by individuals establishing or severing links with others (as studied in strategic network formation). Chapter 5 strangely begins with presenting Folk Theorems for infinitely often repeated base games, e.g. the prisoners’ dilemma game on p. 81. One argument— 123 Bowles, S. and Gintis, H.: A cooperative species—human reciprocity and its evolution 193 see also the own criticism by the authors in section 5.6—against this is that nearly every outcome can be justified by a subgame perfect equilibrium. Why do the authors focus on cooperative outcomes? Another objection is that requiring subgame consistency (all isomorphic subgames must have the same solution) avoids Folk Theorems. Most importantly, however, human life is finite (in the sense of a commonly known upper bound for human life). Viewing the infinite horizon as the limit of large finite horizons is another way to avoid Folk Theorems. Note also that one does not need an infinite horizon when the base game has multiple equilibria with different payoffs (one can threaten to switch to a worse equilibrium in case of a deviation from solution play). Here the criticism would be only that the subgame perfect equilibria which condition on past moves are not subgame consistent. So what remains is the insight that by not just looking at future implications but reacting to some forgone events, we can stabilize cooperation. This again postulates reciprocity inclinations. For this there exists ample evidence—experimentally, however, based on scenarios where a finite horizon is unavoidable. We probably observe a lot of initial cooperation in finite horizon games because of punishment incentives, similar to ultimatum experiments. In Chapter 6 the interesting idea of reputation formation in repeated interaction meaning that human life unfolds in a more or less stable group is elaborated. Note that this allows a cooperative type not only to display own cooperativeness but also the conditional co-operators in his group to behave cooperatively, i.e., we are outside the realm of habitats for which general theorems (of evolutionary selection) predict own material opportunism (assuming that material success is the relevant fitness measure). Such reputation formation requires limited group sizes allowing that everybody learns more or less about all others. The authors try to justify this by referring to anthropological, genetic, and prehistoric warfare evidence. Of course, it is a bit questionable how representative the evidence about which we can learn now is for the circumstances of our ancestors. And should we not more explicitly incorporate the genetic and cultural inheritance of the ancestors (primates) of our (human) ancestors because the evolution of human cooperation did not start from scratch. The coevolution of institutions and behaviors can and should be studied theoretically especially since the efficiency of institutions will depend on the reliability of the individuals implementing them. So, for instance, witness evidence will be rather questionable in a society where lying is common practice. The authors first describe a broad impression about such coevolution by reporting some finding and then formally justify their interpretation by explicitly modelling intergroup interaction: “the model works because altruists confer fitness advantages on insiders, while inflicting fitness costs on outsiders” (p. 113). “Selective Extinction” (Section 7.1) is mathematically formulated and formally analyzed (in Sections 7.2 to 7.4) and applied in Sections 7.5, 7.6 by imposing calibrated parameters before simulating “Gene-Culture Coevolution” (Section 7.7). Chapter 8 continues with simulation findings, this time with simulating “Parochialism, Altruism, and War”, first illustrated by rather special games (Tables 8.1 and Figure 8.1). The authors then go on to discuss what they call “Strong reciprocity” (Chapter 8), namely a “predisposition to cooperate and a willingness to punish defectors” (p. 148). They begin with a little analytical exercise or some complex simulation and then draw rather general and mostly intuitive conclusions which are additionally 123 194 W. Güth supported by field or experimental evidence. “Socialization” (Chapter 10) and “Social Emotions” (Chapter 11) are analyzed in the same way. A special service for the reader is the Appendix with altogether 12 subsections giving the formal details and illustrations of altruism, agent based models, “game theory” (only a glimpse of it), dynamical systems, etc. Reading the book is an exciting experience, mainly because it • is very informative by reporting findings from different sciences like archaeology, eth(n)ology, evolutionary theory, experimental research and relating them to each other, • offers a specific approach relying on partitioning mankind in subgroups allowing altruists to survive in spite of their disadvantage, and reputation formation in small sub-societies, • but also provokes the reader with their approach, e.g. by letting her decide for herself how subgroup structuring results from individual (non)migration tendencies, how to actually imagine the dynamics of genetic and cultural adaptation, how to compare the evidence, generated by archaeologists and eth(n)ologists with those produced by analytic exercises, numerical simulations, and recent experiments. It is this impressive courage of drawing major conclusions from so far still very specific evidence which impresses the reader most. This is not just a selling story but, in my view, the deep conviction of Samuel Bowles and Herbert Gintis how mankind could evolve as a cooperative species due to its strong reciprocity inclinations. Like me, readers might not follow their reasoning in some aspects. But these do not question that the broad picture which they describe is an appealing one. Like me, most readers will finally say: “Dear Herb, dear Sam, I am very impressed and thank you both for this most inspiring book!” 123