Theories of gender transpositions are fundamentally flawed because they often fail to comprise biological, social, familial, and cultural variables which influence the development of sexual behavior and identities in humans. These theories are reminiscent of 19th century views of sexuality which relied on the notion of biological determinism. This approach has been considered reductionistic and has led to conclusions that variations of human sexual expression, such as homosexuality, are deviations from the heterosexual norm. That heterosexuality is considered to be the norm originates from the equation of sexuality to reproductive biology in biomedicine. While there is an impressive body of information on hormonal influence on sexual brain differentiation, prenatal life, and later sexual motor behavior in lower mammals, these findings have not been clearly replicated in primates or humans. Yet, there have been forceful extrapolations to the human from lower mammals (e.g., theories of gender transpositions). Upon critical analyses of hormonal theories of heterosexuality and transsexualism, there are no robust data to support the role of hormones in the development of these behaviors or identities among humans. While an understanding of the etiology of these phenomena, including heterosexuality, is intriguing, we need to be cautious in our zeal to find simplistic explanations and not to retreat to oversimplified notions.
- Sexual orientation