Throughout modern times heterosexuals have accused homosexuals of immorality and mental illness. They have hated and feared homosexuals because they did not understand them. More recently the debate(among heterosexuals) has been whether or not homosexuality is the result of nurture or nature and if the homosexual has a choice. Up until very recently these questions have been confidently answered by people, who it turns out, were only guessing, because there is now scientific evidence showing that male homosexuals are born this way. So how is the gay man born?
All males start out in the womb as female and must be 'converted' into male by testosterone and other hormones. If a women during the early stage of her pregnancy releases more Androstenedione (an adrenaline-related hormone that is structurally similar to testosterone) into her bloodstream and that of her unborn child, it will bind to the receptors that would normally be receiving testosterone thereby 'shielding' the hypothalamus from receiving the amount of testosterone it needs to convert from female to male. In homosexual men, the hypothalamus remains ‘female’ while the rest of the body follows its XY code for male development. We now know that the hypothalamus of homosexual men is smaller than in heterosexual men- about the same size of a female's hypothalamus. Since the hypothalamus is that part of the brain responsible for finding a mate the gay man with a [female] hypothalamus will find men sexually attractive in the same way that heterosexual women do. This is backed-up by the recent pheromone studies that show heterosexual women and homosexual men have the same olfactory nerve responses. For obvious reasons sexual orientation is assigned very early on in fetal development and it cannot be reversed once it is set. Increasing testosterone later in the pregnancy or after birth has shown to have no affect on one's sexual orientation.
While there is no specific 'gay gene' there might be a genetic tendency to produce more Androstenedione. Androstenedione is sometimes called the 'stress hormone' because it's levels can become elevated due to stress. It can also be elevated by certain drugs and possibly other factors such as a later pregnancy. Studies have shown that the youngest son of a woman who has already had several sons is more likely to be homosexual. Why does this happen? We do not yet know. It might be an evolutionary process developed to reduce the size of a family and/or tribe or it could have no specific purpose.
Since hormone levels are fluid we would expect there to be various levels of sexual attraction and gender identification, and that is exactly what we see -from bisexual and masculine gay men to effeminate and the transgender men. It’s possible that if the hypothalamus is completely unchanged one might feel as if he is a women trapped in man's body. Even so, we cannot discount the influence that upbringing and cultural appropriation has on one's personality, behavior and tastes. However, we must realize that these factors do not determine sexual orientation. Unfortunately, people have often confused cultivation with inherited nature.
NOTE: There is a lack of interest by most heterosexual scientists to study homosexuality -party because of their own biases, partly because the outcome of the research does not affect them personally, and partly because they do not wish to get into the middle of a 'cultural war'. These factors have also discouraged people from widely reporting these findings. Because some people find the evidence regarding male homosexuality to be unsatisfactory they have dismissed it. That is unfortunate because what may be true for gay men, may not be true for lesbians, and not yet having a clear picture of one should not negate what we do know about the other. Since a natural cause for male homosexuality has been found it stands to reason that there is natural cause for female homosexuality as well. We still have a lot to learn about the role hormones play in determining sexual orientation and obviously more studies are needed.