ABSTRACT: Dissolving the evolutionary puzzle of human cooperation.

Transcription

1 ABSTRACT: Dissolving the evolutionary puzzle of human cooperation. Researchers of human behaviour often approach cooperation as an evolutionary puzzle, viewing it as analogous or even equivalent to the evolutionary puzzle of altruism studied by theoretical biologists. However there are many problems with seeking the ultimate explanation for the evolutionary puzzle of human cooperation using the tools of theoretical biology. These problems have been largely addressed in previous reviews of the human cooperation literature, however we believe that these critiques do not go far enough. While previous critiques emphasize how existent theoretical tools have been misapplied, we argue that these tools, even when correctly applied, are inherently unsuitable for the study of most human behaviours commonly regarded as cooperative. Thus while previous critiques suggest that if researcher's of human cooperation were simply to brush up on their theoretical biology they could solve the evolutionary puzzles of human cooperation, we argue that researcher's studying human cooperation simply do not have an evolutionary puzzle to solve. In this talk we clarify what constitutes an evolutionary puzzle. We focus specifically on the history of the evolutionary puzzle of altruism, and the success of a research strategy known as the phenotypic gambit in this domain. We review the cases for and against the phenotypic gambit and summarize the collected wisdom as to when the phenotypic gambit is justified. We go on to make explicit the phenotypic gambit implicit in the evolutionary puzzle approach to human cooperation. We then highlight why the phenotypic gambit, while wildly successful across broad domains of plant, animal and human behaviour, remains inappropriate for providing evolutionary explanations of the many phenomena typically considered human cooperation. We conclude with a discussion of possibilities for extending the evolutionary game theoretic framework to overcome the particular issues raised by human cooperation.

2 Dissolving the evolutionary puzzle of human cooperation. Daniel Cownden Center for the Study of Cultural Evolution, Stockholm University Thursday July 11, 2013

3 Collaborators Pontus Strimling Kimmo Eriksson

4 Human Cooperation as Evolutionary Puzzle Human cooperation is an evolutionary puzzle. Unlike other creatures, people frequently cooperate with genetically unrelated strangers, often in large groups, with people they will never meet again, and when reputation gains are small or absent. These patterns of cooperation cannot be explained by the nepotistic motives associated with the evolutionary theory of kin selection and the selfish motives associated with signalling theory or the theory of reciprocal altruism. -Fehr and Gächter Altruistic Punishment in Humans Science 2002

5 Human Cooperation as Evolutionary Puzzle The scale of human cooperation is an evolutionary puzzle. All of the available evidence suggests that the societies of our Pliocene ancestors were like those of other social primates, and this means that human psychology has changed in ways that support larger, more cooperative societies that characterize modern humans. -Boyd and Richerson Culture and the Evolution of Human Cooperation Phil. Trans. B 2009

6 Altruism: A Classic Evolutionary Puzzle There are genes A and D. An individual with gene A, has c fewer offspring than an individual with gene D. An individual with gene A will cause some other individual to have b more offspring. Individuals with the gene D cause no such benefit. How can gene A persist in a population?

7 Simplest Classic Formulation Partner chosen uniformly at random. Discrete generations p = proportion of A types q = proportion of D types α = baseline offspring Partner has A Partner has D Focal has A b-c -c Focal has D b 0 Change in focal's baseline offspring as a function of the focal's gene and the partner's gene

8 Altruism: Classic Solutions Hamilton The Genetical Evolution of Social Behaviour JTB 1964 Can be done in lots of different ways. People argue about which is the right way. Keep track of where the genes are.

9 What About Reciprocal Altruism? Trivers The Evolution of Reciprocal Altruism Q Rev Biol 1971 Reciprocal Altruism does not solve our original problem but transforms it. Partner has A Partner has D Focal has A n x (b - c) -c Focal has D b 0 Critically: n x (b c) > b

10 The Phenotypic Gambit Inheritance mechanism: pleiotropy, sex, ploidy, epistasis, linkage disequilibrium. Phylogenetic/Ontological constraint. Sufficient genetic and phenotypic variation. Environmental Stability.

11 Coming Back to Human Cooperation The question of whether or not the gambit is justified depends entirely on the trait in question. In this case, Human Cooperation, which is...

12 Human Cooperation is: Trade Division of labour Sharing meat Hunting big game Warfare Conserving common property

13 Are these behaviours evolutionary puzzles? For each behaviour we must make the gambit: This behaviour corresponds to strategy in a game. The payoffs of this game are in terms of fitness. Simplified evolutionary dynamics can be used. The observed behaviour does not correspond to an ESS of this game.

14 Pleiotropy and Epistasis ``Organisms are integrated entities, not collections of discrete objects.'' - Gould and Lewontin The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme Proc. B 1979 Behaviour Gene

15 Pleiotropy and Epistasis Prosocial behaviours are correlated across a variety of distinct strategic situations and with Social Value Orientation, though not with rejection of low offers in ultimatum games. -Yamagishi et al. 2012, 2013 Punishment behaviours are correlated across situations where punishment is both group beneficial and group detrimental. We expect personality traits to correlate with behavioural patterns, but that these behavioural patterns be related to perceptual, not strategic, similarities.

16 Hope for the future Integrate multiple games and personality measures. Differentiate between the game played, and the game perceived. Develop a theory of cultural evolution. Investigate the origins of human cognition, language and planning.

17 thank you

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19 Tinbergen's Four Questions Mechanism Ontogeny Adaption Phylogeny Our original question considers only adaption. Here Hamilton's insight provides the key. Triver's insight moves the domain of the problem to Mechanism.

20 Human Cooperation as Evolutionary Puzzle Humans are a uniquely cooperative species. In even the simplest societies, people cooperate in large groups of genealogically distant individuals...recent theoretical studies provide an evolutionary explanation for such cooperative behavior: Punishment reduces gain to free-riding, so groups with more punishers can sustain more cooperation...the initial emergence of punishment remains a puzzle. - Boyd, Gintis & Bowles Coordinated Punishment of Defectors Sustains Cooperation and Can Proliferate When Rare Science 2010

21 Human Cooperation is also: Giving more than zero in the dictator game. Giving more than the smallest allowable increment in the ultimatum game. Rejecting unfair offers in the ultimatum game. High contribution in a public goods game. Punishing a low contribution in a public goods game.