Kinship Systems, Cooperation and the Evolution of Culture

Cultural psychologists and anthropologists argue that societies have developed heterogeneous systems of social organization to cope with social dilemmas, and that an entire bundle of psychological and biological characteristics has coevolved to enforce cooperation within these different regimes. This paper develops a measure of the tightness of historical kinship structures to provide empirical evidence for this large body of theories. In the data, societies with loose ancestral kinship ties cooperate and trust broadly, which appears to be sustained through a belief in moralizing gods, universal moral values, internalized guilt, altruistic punishment, and large-scale institutions. Societies with a historically tightly knit kinship structure, on the other hand, exhibit strong in-group favoritism: they cheat on and distrust out-group members, but readily support in-group members in need. This cooperation regime is enforced by tribalistic moral values, emotions of external shame, revenge-taking, conformity to social norms, and strong local institutions. These relationships hold across historical ethnicities, contemporary countries, ethnicities within countries, and among migrants. The results suggest that religious beliefs, moral values, social preferences, emotions, social norms, and institutions all coevolved to support specific social cooperation systems