My hypothesis -which I am sure is somewhere in the internet- is that evolution selected and maintained the genes responsible for male homosexuality and male transsexuality because it enhances the survivorship of our specie.
If you think about, for most of our existence as "modern" humans, say about the last 100,000 yeas, one of the main role of the males has been the acquisition of large source of protein (meat) for the tribe. leaving the females, children, and old man while going out for long haunting trips left the tribe exposed to enemies and predators. Having some transsexuals and/or homosexual males who wanted to stay behind doing the female-role chores was advantageous because this trans-females and gay males were still able to defend the females, children, and old males left behind.
Ok so far, the question that then arises is: "How about the last 5,000 years?" This questions arises because we invented agriculture (and by that I mean we females..LOL), and made other cultural developments that resulted in the permanent presence of males within a city/tribe. Well, my hypothesis, and again I do not know if other have proposed a similar one, is that the mutation leading to GID or homosexuality more often than note are also associated with genes that conferee added intellectual capabilities. It is thus not surprising to notice that even in the absence of education most GID and homosexual people tend to be "gifted" peoples, inventors, musicians, artists, craftsman, innovators, educators, etc...
of course these are just my unproven hypothesis.... food for thought gents and ladies
Nice thread Brianna!
Dr. Peky
PS Oh, and please do not give me any applauses, it may distract my intellect..LOL