Most of the contributions to Cooperation and Its Evolution grapple with the distinctive challenges presented by the project of explaining human sociality. Many of these puzzles have a ‘chicken and egg’ character: our virtually unparalleled capacity for large-scale cooperation is the product of psychological, behavioural, and demographic changes in our recent evolutionary history, and these changes are linked by complex patterns of reciprocal dependence. There is much we do not yet understand about the timing of these changes, and about the order in which different aspects of human social psychology (co-)evolved. In this review essay, I discuss four such puzzles the volume raises. These concern punishments and norm-psychology, moral judgement and the moral emotions, hierarchy and top-down coercion, and property rights and legal systems.
The structural parallels between the four preceding cases are clear. In all four, we find two features of human social life that now seem inextricably entangled, and we are left wondering how one could ever have evolved without the other. The most promising strategy, in all four cases, is to break the target phenomenon into its constituent parts and attempt to construct a gradual transition in which those parts were cumulatively assembled, each successive change in one enabling further alterations in the other. It is an explanatory strategy that has reaped dividends in other areas of biology, and it will no doubt do so in the human case too. But there are so many pieces of the jigsaw we do not yet have—and so many alternative ways to fill in the gaps. In sum, Cooperation and Its Evolution is essential reading for anyone who seeks a better understanding of the puzzles we face in explaining human social evolution and a sharper picture of the space of possible solutions.
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