How the brain determines sexuality

This opened up a fascinating debate: Did this apply to humans, and if so, how? We know that the male human embryo forms testes very early during pregnancy (about 10 weeks) and that these new testes promptly start to secrete testosterone. This means that the male brain is exposed to testosterone during a critical time during its development. What are the effects, and are they as long-lasting as in other species?

Human sexuality, of course, is made up of several components, though they overlap. Gender identity – the sex you identify with – is almost impossible to study in animals, though we know that males of many species treat other males differently than females, suggesting some sort of knowledge of gender, and an equivalence to gender role in humans. Sexual preference can be studied, as can patterns of sexual activity. Both the latter are altered by exposure (or lack of it) to testosterone early in life in the expected direction in animals. Testosterone, it appears, has a major role or the development of sexuality. In the 1980s, when Germany was still divided into a Western segment and an Eastern one under the domination of the then Soviet Union, a group of East scientists proposed that human homosexuality was the result of insufficient exposure to testosterone in the womb. Since the moral atmosphere of the time in that country regarded homosexuality with abhorrence, they proposed that all pregnant females should have the fluid surrounding their male foetuses tested for testosterone. Those with low values (they did not specify what these were) should be aborted, thus eliminating gay men from East German society. An excellent example of the misuse of science, though it was never adopted.