[glouch]

http://en.wikipedia.org/wiki/Fraternal_b...rientation

That has nothing to do with genetics.

Nobody said that you can't turn gay from a shitty childhood, just that you aren't born with a sexual orientation.

one theory claims that the birth order affects birth rate because of the condition of the womb during development for children after the first one.

obviously there's nothing conclusive, but evidence seems to point towards the fact that genetics will give you a PREDISPOSITION to developing a certain sexuality. So no, people are not born gay, but they're born with certain factors that could influence homosexuality. It's a typical case of the nature vs nurture debate, and as is usually the case, it's a little bit of both.

as for being gay and its effect on passing on genes, I remember reading something about that, lemme see if I can dig it up...