The Origins of Human Cooperation

Biological explanations of cooperation are based on kin altruism, reciprocal altruism, and mutualism, all of which apply to human and nonhuman species alike. But human cooperation is based in part on capacities that are unique to, or at least much more highly developed in, Homo sapiens. We seek an explanation of cooperation that works for humans, but does not work for other species, or works substantially less well. Central to our explanation will be human cognitive, linguistic and physical capacities that allow the formulation of general norms of social conduct, the emergence of social institutions regulating this conduct, the psychological capacity to internalize norms, and the basing of group membership on such non-kin characteristics as ethnicity and linguistic behavior, which facilitates highly costly conflicts among groups. We show that these could have co-evolved with other human traits in a plausible representation of the relevant environments. The forms of cooperation we seek to explain are confirmed by natural observation, historical accounts, and behavioral experiments. Our account is based on a plausible evolutionary dynamic involving some combination of genetic and cultural elements, the consistency of which can be demonstrated through formal modeling. Moreover, the workings of the models we develop account for human cooperation under parameter values consistent with what can be reasonably inferred about the environments in which humans have lived. ∗To appear in Peter Hammerstein (ed.) The Genetic and Cultural Origins of Cooperation (Cambridge: MIT Press, 2003). We are grateful to Eric Alden Smith for helpful comments and to the John D. and Catherine E. MacArthur Foundation for support of this research. Samuel Bowles is Professor of Economics at the University of Siena and Director of the Economics Program at the Santa Fe Institute. Herbert Gintis is a member of the External Faculty of the Santa Fe Institute. Both authors are Emeritus Professors of Economics, University of Massachusetts. Email addresses: bowles@santafe.edu and hgintis@attbi.com. Web sites: http://www-unix.oit.umass.edu/ ̃bowles, http://www-unix.oit.umass.edu/ ̃gintis.