Human Reproductive Egalitarianism: A Catalyst for the Evolution of Personality Traits

The human, species-typical reproductive system is distinctive and unique among the great apes. It involves pair-bonding and long-term mating as well as male investment in both mate and offspring. Studies have demonstrated that this mating system produces the lowest male reproductive skew known in primates as well as in mammals generally which entails the lowest level of reproductive failure among human males compared to other primate/mammalian species. It is argued that this low reproductive skew leads to an increase in the effective population size and to a greater diversification/variation in personality and behavioural traits in the population compared to other species. The implications of this Reproductive Egalitarian Model for human mating are discussed with regard to the emergence of human personality traits, social complexity, division of labour and risk of mental disorder.