The field of twin studies has shed some light on the old 'nurture vs. nature' debate.
Many people have held that one's upbringing is of far greater influence than one's genes.
Whilst 'nurture' is still regarded as important, it's amazing how much is buried in the genes.
If one of a pair of twins bought up seperately from their twin turns out to be gay, it is twice as likely that their twin will be gay, even if they grow up with no knowledge of each other in different environments. If they are fraternal twins, it's lower, if just normal sinlings then only slightly above the average for society.
That doesn't mean all homosexuals are 'born that way', but it shows that for many being gay is part of their natural make-up. And if some people are gay without it being due to their gene's, so what?
Funnily enough, twin studies have shown relgious inclination is about as genetic as homosexuality.
If one of a pair of identical twins seperated at birth is very religous, it is far more likely than normal for their seperated twin to share their depth of religious devotion, even though the actual religion might vary according to the family they were bought up in.
If I get a chance I'll post some URL's, but I'm at work and busy today.
Of course, the question of WHY religious inclination is a genetic inheritable component is a different one.
My personal take is that it ISN'T religion that some of us are genetically inclined towards. Religion is the path taken to fufil needs.
The needs of community and of belonging and of belief - and I don't neccesarily mean belief in god, but a suseptability towards belief.
It would be a trait that would be positively selected by evolution, as people with that trait would form more succesful communities than those without.
People without an inclination towards community and belonging, and without that suseptability towards belief would be less inclined towards communities and less able to conform to their structures as they wouldn't have that binding ability to believe in their community and its values.
Also, a community with people with this inclination towards belief would survive better as they would be more willing to be lead by a leader, as they would believe in him. There would be less dissention and factionalism as a dominant alpha-male would be less likely to be opposed.
Fun isn't it?