The bonobo has high levels of sexual behavior. Sex functions in conflict appeasement, affection, social status, excitement, and stress reduction. It occurs in virtually all partner combinations and in a variety of positions. This may explain the lower levels of aggression in the bonobo as compared to the common chimpanzee and other apes. Bonobos are matriarchal and a male's rank in the social hierarchy is often determined by his mother's rank.