The (bi)sexual brain

Most animals begin their lives as a single cell, grow and develop into one of two sexes and, when mature, interact with the other sex to conceive a new single cell that starts the cycle anew. This basic equation underlies all aspects of sexuality; that is, specific traits evolved to attract members of the opposite sex, ensure copulation and thereby reproduction. It also suggests that all life forms evolved from ancestors that could adopt both male and female roles (Fig 1)— bisexual life forms—and we can find elements of bisexuality throughout all life processes, including the brain functions in higher animals that control sexual behaviour. But, semantics can manipulate perception: the general view still defines male and female in regard to the opposite sex and focuses on differences rather than similarities. However, to explain sexual behaviour, there is a new perspective that regards it as an emergent property of specific areas of the brain.