The coevolution of kinship systems, cooperation, and culture

Prof Benjamin Enke of Harvard Univ analyses the relationship between kinship, cooperation and culture. This issue is perhaps the holy grail of all social studies.

He says that societies with tighter kinship cooperate more within but poorly outside:

I find that ancestral kinship tightness is indeed strongly predictive of cultural variation in cooperation and trust patterns. In societies that historically had tight kinship systems, people exhibited strong in-group favouritism. They cooperated poorly in experimental games with out-group members, and even cheated them, but assigned high importance to helping in-group members in need. Similarly, they have shown high trust in in-group members such as neighbours, but low trust in strangers and people in general. In contrast, societies with loose ancestral kinship ties cooperate effectively and trust broadly, yet do not place special emphasis on helping in-group members in need.

If kinship tightness is associated with fundamentally different cooperation systems, then – according to the psychological and anthropological theories – it should also be related to the structure of psychological, biological, and institutional enforcement devices. That is, religious beliefs, moral values, shame versus guilt, formal institutions, and social norms should vary as predicted by theory. I establish that this is the case. In particular, I find that societies with loose ancestral kinship ties appear to regulate behaviour through belief in a moralising god, universal moral values that emphasise concepts as individual harm, rights and justice, internal feelings of guilt, and ‘global’ institutions that supersede separate in-groups.

In contrast, societies with a tight kinship structure seem to enforce cooperative behaviour through ‘communal” or tribal moral values such as in-group loyalty, emotions of external shame, and strong local institutions and social norms – alongside values that mandate norm-adherence and behaving properly.

So the structure of enforcement devices closely corresponds to observed cooperation and trust patterns. This suggests a coevolution of kinship structures, cooperation regimes, institutions, and cultural traits. In particular, punishment in tight kinship societies is largely personal and direct, while in loose kinship societies it is often anonymous and relies on ‘psychological police officers’. The apparently puzzling amount of cultural variation in what appears to be unrelated psychological and biological phenomena can be understood through the lens of coevolution for the purpose of ensuring effective cooperation.


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