J Econ (2011) 104:191–194DOI 10.1007/s00712-011-0237-5

BOOK REVIEW

Bowles, S. and Gintis, H.: A cooperativespecies—human reciprocity and its evolution288pp, 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 thisis that it allows for continuity in the sense that also ape species, our close relatives inthe animal kingdom, are “cooperative species”. Thinking of genocides, e.g. in the formof building concentration camps to murder millions of people, should make it clearthat “cooperative” is a rather neutral quality—we often “cooperate” in doing good aswell as in causing harm. The book offers a rich account of biological, anthropological,experimental findings which render its reading undoubtedly worthwhile. The questionis, however, whether the authors are rather eclectic in reporting evidence and whenexplaining what they report. And one is left alone when asking oneself how is “coop-eration” related to specialization and labor division which is so highly developed inhomo sapiens, what, of course, presupposes some trading group exceeding the size offamilies. But let us first describe what the book offers.

Chapter 1 elaborates on what is actually meant by “A Cooperative Species”, namelythat we “are genuinely concerned about the well-being of others, try to uphold socialnorms, and value behaving ethically for its own sake” (p. 1) and that this is so becauseour (human) ancestors lived in habitats where such qualities were fitness enhanc-ing. Actually, the main idea is that they existed in groups of “individuals who werepredisposed to cooperate and uphold ethical norms” (p. 1).

Inclinations to care for group welfare are justified as being evolutionarily stablesince phenotypes with such inclinations protect themselves by ostracizing those with-out 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 theirhabitat. What is less clear is whether such structural aspects also apply to some otherspecies. We should be afraid of a hindsight bias, e.g. in the sense of assuming thatwhat we know has happened, had to happen?

W. Güth (B)Max Planck Institute of Economics, Jena, Germanye-mail: gueth@econ.mpg.de

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After briefly mentioning the normative approach to decision making, based onpreferences, beliefs and constraints (action space), Chapter 2 propagates the idea ofsocial preferences, specifically altruism. As experimental evidence, the authors men-tion results of one-shot prisoners’ dilemma games for which appropriately definedaltruism can render mutual cooperation an equilibrium outcome. What “evolution”means is then more clearly discussed in the section on “Genes Culture, Groups, andInstitutions”. The authors refer to gene-culture coevolution where, of course, geneticadaptation is slow compared to the tremendous speed of cultural evolution in man-kind. “The parallel between cultural and biological evolution” (p.15) is more difficultto buy, especially since cultural adaptation often relies on institutional prerequisites(schools, universities,. . .). Regarding genetic evolution one would have liked to see aconvincing argument how and why human intelligence could evolve and why we usethis intelligence to bother about the well-being of those in the same group and to harmthose in other groups.

Chapter 3 propagates “Social preferences” in the sense of reciprocity inclinationor responding in kind. The concept was studied in (social) psychology long beforeits more recent discussion in experimental economics employing punishment gamesor trust-and-reward games. The evidence is often very interesting, especially whencross-cultural effects are reported (Section 3.8) where—as often in so-called cross-cultural/country studies—one misses the comparison with intra-cultural/country var-iance.

Interestingly enough, when played repeatedly using a partners design, the evidenceis rather uncomforting since cooperation is declining. What this shows is that withoutpunishment institutions like veto power in the ultimatum game, cooperation is endan-gered. Could one not argue: we are not intrinsically concerned about others’ well-beingbut we are clever enough to develop emotional reactions that make us reciprocate?

Actually, when in an ultimatum experiment having to wait before reacting to anunfair proposal, the rejection rate is smaller than when responding impulsively. It verymuch depends on circumstances how reciprocal we are. Couldn’t it be that we havedeveloped a very flexible behavioral repertoire of which “cooperativeness” is only oneoption? Social preferences in the narrower sense of neoclassical economics can easilybe shown (analytically) to be evolutionarily stable when certain conditions prevail: ifchanging the own preference type is somehow noticeable by others, this change doesnot 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 propa-gates is to give up the standard assumption of unbiased random matching. It is wellknown that in case of sufficiently strong associative matching cooperative behaviorcan 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 babywith the bath water. To maintain one species of all, there has to be migration. To justifythe claim of methodological individualism, one would like to hear a story how sucha group structure results from individual choices, e.g. by individuals establishing orsevering links with others (as studied in strategic network formation).

Chapter 5 strangely begins with presenting Folk Theorems for infinitely oftenrepeated base games, e.g. the prisoners’ dilemma game on p. 81. One argument—

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see also the own criticism by the authors in section 5.6—against this is that nearlyevery outcome can be justified by a subgame perfect equilibrium. Why do the authorsfocus on cooperative outcomes? Another objection is that requiring subgame consis-tency (all isomorphic subgames must have the same solution) avoids Folk Theorems.Most importantly, however, human life is finite (in the sense of a commonly knownupper bound for human life). Viewing the infinite horizon as the limit of large finitehorizons is another way to avoid Folk Theorems. Note also that one does not needan 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 solutionplay). Here the criticism would be only that the subgame perfect equilibria whichcondition on past moves are not subgame consistent. So what remains is the insightthat by not just looking at future implications but reacting to some forgone events,we can stabilize cooperation. This again postulates reciprocity inclinations. For thisthere exists ample evidence—experimentally, however, based on scenarios where afinite horizon is unavoidable. We probably observe a lot of initial cooperation in finitehorizon games because of punishment incentives, similar to ultimatum experiments.

In Chapter 6 the interesting idea of reputation formation in repeated interactionmeaning that human life unfolds in a more or less stable group is elaborated. Note thatthis allows a cooperative type not only to display own cooperativeness but also theconditional co-operators in his group to behave cooperatively, i.e., we are outside therealm of habitats for which general theorems (of evolutionary selection) predict ownmaterial opportunism (assuming that material success is the relevant fitness measure).Such reputation formation requires limited group sizes allowing that everybody learnsmore or less about all others. The authors try to justify this by referring to anthropolog-ical, genetic, and prehistoric warfare evidence. Of course, it is a bit questionable howrepresentative the evidence about which we can learn now is for the circumstances ofour ancestors. And should we not more explicitly incorporate the genetic and culturalinheritance of the ancestors (primates) of our (human) ancestors because the evolutionof human cooperation did not start from scratch.

The coevolution of institutions and behaviors can and should be studied theoret-ically especially since the efficiency of institutions will depend on the reliability ofthe individuals implementing them. So, for instance, witness evidence will be ratherquestionable in a society where lying is common practice. The authors first describe abroad impression about such coevolution by reporting some finding and then formallyjustify their interpretation by explicitly modelling intergroup interaction: “the modelworks because altruists confer fitness advantages on insiders, while inflicting fitnesscosts on outsiders” (p. 113).

“Selective Extinction” (Section 7.1) is mathematically formulated and formallyanalyzed (in Sections 7.2 to 7.4) and applied in Sections 7.5, 7.6 by imposing cali-brated parameters before simulating “Gene-Culture Coevolution” (Section 7.7).

Chapter 8 continues with simulation findings, this time with simulating “Parochi-alism, Altruism, and War”, first illustrated by rather special games (Tables 8.1 andFigure 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 defec-tors” (p. 148). They begin with a little analytical exercise or some complex simulationand then draw rather general and mostly intuitive conclusions which are additionally

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supported by field or experimental evidence. “Socialization” (Chapter 10) and “SocialEmotions” (Chapter 11) are analyzed in the same way. A special service for the readeris the Appendix with altogether 12 subsections giving the formal details and illustra-tions of altruism, agent based models, “game theory” (only a glimpse of it), dynamicalsystems, 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 eachother,

• offers a specific approach relying on partitioning mankind in subgroups allowingaltruists to survive in spite of their disadvantage, and reputation formation in smallsub-societies,

• but also provokes the reader with their approach, e.g. by letting her decide for her-self how subgroup structuring results from individual (non)migration tendencies,how to actually imagine the dynamics of genetic and cultural adaptation, how tocompare the evidence, generated by archaeologists and eth(n)ologists with thoseproduced by analytic exercises, numerical simulations, and recent experiments.

It is this impressive courage of drawing major conclusions from so far still veryspecific 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 mankindcould evolve as a cooperative species due to its strong reciprocity inclinations. Likeme, readers might not follow their reasoning in some aspects. But these do not questionthat the broad picture which they describe is an appealing one. Like me, most readerswill finally say: “Dear Herb, dear Sam, I am very impressed and thank you both forthis most inspiring book!”

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