[chownie]

Culture determines your publicly expressed outward identity, I have no doubt that people have assumed a gay/trans/etc identity privately for far longer than we've had terms or tolerance for them.

Some of the most common observations by our very small trans elderly is that they "found a way to describe" or "finally found the words" for who they are, ie the identity was always there but no terms to identify with.

I think by and large it's nature (fraternal birth order effect, twin studies etc) modulated to the extreme by societal rejection. You dont see gay men in the streets of countries where homosexuality earns the death penalty, you instead see extremely depressed "straight" men :)