Evolutionary theory, kinship, and childbirth in cross-cultural perspective

The authors combine evolutionary theory with the anthropological study of kinship to account for cross-cultural diversity in birth-related investments by kin. Four hypotheses are formulated using paternal certainty, gender, and kinship laterality as independent variables. They test these hypotheses with data from the 60-culture Probability Sample of the Human Relations Area Files (HRAF). Their hypotheses are generally confirmed. For example, grandmothers and aunts provide more direct birth care than grandfathers and uncles. However, they did have some unanticipated results. Fathers provide as much direct birth care as grandmothers and aunts. In addition, they found paternal certainty to be a better predictor of direct birth care than kinship laterality, and kinship laterality to be a better predictor of indirect care. They explain this difference by arguing that direct birth care is the most important kind of investment kin make to ensure the survival and reproduction of mothers and newborns.