EVOLUTION: The Rise And Fall of Sexual Promiscuity. “Promiscuity is a funny thing in nature. Despite what your mother and youth pastor spent so many years telling you, sleeping around has real (genetic) benefits. Polyandry—in which females take more than one mate—allows for better gene diversity, boots the likelihood of fertilization, decreases infanticide, and means more male providers. Gavrilets acknowledges that in switching from promiscuity to monogamy, females actually risked lower fertility. The tradeoff was security.”