Homosexual behaviour is not limited to humans. Biologists have reported homosexual behaviour in many species of wild animal, ranging from bats and birds to dolphins and primates.
When animals engage in homosexual behaviour, one might assume that they invest less time and energy on reproduction. This suggests that there may be strong reproductive costs associated with such behaviour, such as having fewer offspring. So it raises the question of how homosexual behaviour manages to evolve and continue to exist within a population.
