Since it's such a hot topic these days. "Yet, current research indicates that because of the expected hormonal exposure secondary to genetic sex, a certain gender bias probably exists in all newborns. This rudimentary gender identity, although incomplete, is an important determinant in gender development. The dimorphism of the brain itself suggests this. Nevertheless, variations may occur when endogenous or exogenous factors create a fetal environment where hormone levels do not follow the genetically determined pattern. The gender bias of these infants may be tilted away from one that correlates with the genotype. Such variations are discussed below. " http://www.emedicine.com/PED/topic2789.htm I don't know if this proves the morality/immorality of being gay either way, just as evolution doesn't disprove god. God and Satan could BOTH work through the mechanism of biology I suppose.