What Explains Patrilineal Cooperation?

Evolutionary anthropologists have proposed that unilineal kinship promotes collective action and that patriliny occurs when the reproductive payoff from passing wealth to sons is greater than that for daughters. We assess both of these theoretical perspectives as well as indirect reciprocity and kin selection as possible contributors to patrilineal cooperation in the Dogon of Mali. The mean coefficient of relatedness for males (N = 4,724) in 31 Dogon patrilineages is r = 0.03, which is very low (akin to second cousins). However, relatedness in the 638 work-eat groups (WEGs) that make up the patrilineages is very high (r = 0.32), or greater than for half siblings. Indirect reciprocity and collective action explain cooperation among fictive kin in the patrilineage as a whole: the old men at the apex of the lineage help to stabilize cooperation by using their gerontocratic authority to punish cheaters. However, kin selection is a more useful theory for explaining cooperative behavior within WEGs, and both quantitative data and informants' statements show that WEGs are the more important unit for economic activity and family life. As expected for a patrilineal society, the Dogon derive a greater reproductive payoff from passing land and livestock to sons than to daughters.