Sex Differences in Human Peer Relationships: A Primate’s-Eye View

Bonds formed by nonhuman animals can illuminate the structure of human relationships. In the juvenile period, primates of many species that are genetically similar to humans form sex-differentiated bonds in which females spend more time with female kin, and males spend more time with unrelated same-sex peers. Research with humans suggests a similar sex difference, with one notable addition: Beginning in middle childhood, male peer groups begin engaging in complex activities, including intergroup contests. This additional component of human peer relations resembles that of chimpanzees (Pan troglodytes), one of humans’ closest living genetic relatives. Cross-species and developmental evidence can aid in constructing a theory of human peer relations that differs by sex.