Self-domestication refers to an evolutionary process in which aggressive behavior is selected against, which makes a species less aggressive and more friendly and social. Bonobos, who share a common ancestor with chimpanzees, show far less aggression than chimpanzees. It is thought that bonobos have become 'self domesticated' due to female bonobos only reproducing with the more gentle males. This process may also apply to humans, who are very social compared to other species.