Genes versus Hormones in Homosexuality

It is clear, however, that the cause of homosexuality lies in some unusual balance of hormonal influence in the womb but not later on, a fact that further supports the idea that the mentality of sexual preference is affected by prenatal sex hormones. This is not incompatible with the growing evidence that homosexuality is genetically determined. The "gay gene" that I will discuss in the ext chapter is widely expected to turn out to be a series of genes that affect the sensitivity of certain t...

 How Testosterone Affects the Brain

We last met the steroid hormone testosterone in fish and birds where it was rendering them more vulnerable to parasites by exaggerating their sexual ornaments. In recent years more and more evidence has been found that testosterone affects not just ornaments and bodies but also brains. Testosterone is an ancient chemical. found in much the same form throughout the vertebrates. Its concentration determines aggressiveness so exactly that in birds with reversed sex roles, such as phalaropes and ...