sexual selection

Sexual selection creates colourful differences between sexes in Goldie's bird-of-paradise. Male above; female below. Painting by John Gerrard Keulemans.

Sexual selection is a mechanism of evolution in which members of one sex choose mates of the other sex (intersexual selection) to mate with, and compete with members of the same sex for access to members of the opposite sex (intrasexual selection). These two forms of selection mean that some individuals have greater reproductive success than others within a population, for example because they are more attractive or prefer more attractive partners to produce offspring. Successful males benefit from frequent mating and monopolizing access to one or more fertile females. Females can maximise the return on the energy they invest in reproduction by selecting and mating with the best males.