One hypothesis attributes differences in gender roles to evolution. The sociobiological view argues that men's fitness is increased by being aggressive, allowing them to compete with other men for access to females, as well as by being sexually promiscuous and trying to father as many children as possible. Women are benefited by bonding with infants and caring for children. Sociobiologists argue that these roles are evolutionary and led to the establishment of traditional gender roles with women in the domestic sphere and men dominant in every other area.