The socioecology of infant handling in primates: Is the current model convincing?

A strong interest shown by females towards infants other than their own is one of the most consistent behavioral traits found in primates, including humans. Species differences exist, however, in the extent mothers allow other group members to interact with their offspring. Socioecological theory predicts that in species characterized by relaxed, egalitarian dominance relations mothers should allow extensive interactions between their infants and other individuals from the first weeks of life, while in species characterized by nepotistic and despotic dominance relations maternal tolerance of infant handling should be low. While this model received some support from a comparison between colobines and some cercopithecines, several other species, including the Barbary macaque, do not appear to fit easily into the framework. In fact, only about half of all well-studied species follow the predicted pattern, suggesting that other factors, associated with the costs and benefits of the behavior, must be invoked to explain the variation in mothering styles and infant handling found in primates.