Bonobos Exhibit Delayed Development of Social Behavior and Cognition Relative to Chimpanzees

SummaryPhenotypic changes between species can occur when evolution shapes development. Here, we tested whether differences in the social behavior and cognition of bonobos and chimpanzees derive from shifts in their ontogeny, looking at behaviors pertaining to feeding competition in particular. We found that as chimpanzees (n = 30) reached adulthood, they became increasingly intolerant of sharing food, whereas adult bonobos (n = 24) maintained high, juvenile levels of food-related tolerance. We also investigated the ontogeny of inhibition during tasks that simulated feeding competition. In two different tests, we found that bonobos (n = 30) exhibited developmental delays relative to chimpanzees (n = 29) in the acquisition of social inhibition, with these differences resulting in less skill among adult bonobos. The results suggest that these social and cognitive differences between two closely related species result from evolutionary changes in brain development.

► Chimpanzees decrease in interindividual tolerance with age; bonobos do not
► Chimpanzees outperform same-age bonobos in tasks of social inhibitory control
► Species differences in behavior may correlate with changes in brain development
► The same developmental pathway may mediate the ontogeny of numerous traits.