Cooperative Breeding and its Significance to the Demographic Success of Humans

The demographic success of humans compared with other closely related species can be attributed to the relatively rapid pace of reproduction and improved chances of survival. The assistance that mothers receive from others to help raise children is a common theme in explaining this gain in surviving fertility. Cooperative breeding in its broad definition describes such a social system in which nonmaternal helpers support offspring who are not their own. In traditional societies, kin and nonkin of different ages and sex contribute both to child care and to provisioning older children. This review discusses empirical evidence for human cooperative breeding and its demographic significance and highlights the ways in which humans are similar to and different from other cooperative breeders. An emphasis is placed on cross-cultural comparison and variability in allocare strategies. Because helping in humans occurs within a subsistence pattern of food sharing and labor cooperation, both kin selection and mutualism may explain why children are often raised with nonmaternal help. Cooperative breeding is relevant to debates in anthropology concerning the evolution of human life history, sociality, and psychology and has implications for demographic patterns in today's world as well as in the past.