[QUOTE=AHunter3]
Actually, it is possible that there are evolutionary mechanisms that affirmatively select for a recessive gay gene (should one exist).
Let’s say you are born in the neolithic age to parents one of whom has a gay brother or sister. Some other kid gets born under otherwise similar circumstances to parents neither of which have close gay relatives.
While it is true that gay people can reproduce (being gay doesn’t prevent you from engaging in heterosexual conduct, after all), I would suggest that they would be quite a bit less inclined to do so. So your aunt or uncle is not only gay but childless. And perhaps your aunt or uncle has a good close relationship with a significant other, so you’ve got two childless gay aunts or uncles in a sense. And they pitch in and participate in your child care, helping to spread out the childcare responsibilities, giving your natural parents a break or the freedom to go hunt mastodons or find better sweet potatoes or something.
Advantage: you. You survive in situations where the other kid, lacking such relatives, doesn’t.
And your survival means the gene-set, which may well include some components that were expressed as being gay in your uncle or aunt, persists to be passed on to your own kids, in whom, if it’s a recessive trait, will get passed on yet again.
[/QUOTE]
No offense to you, but that’s really just wild speculation, and very unlikely to explain why x% of people are “born gay”.
We pretty much know that homosexuality is not wholly genetic, given the fact that identical twins don’t always share the same sexuality. It probably has a genetic component, but there are almost certainly some other factors as well.
A more probable scenario is that there is a siute of genes controlling sexuality (and other behaviors) and that sometimes those genes mix and match in a way that produces homosexuality (when combined with other factors). However, it is advantages to the population as a whole to have the entire suite of genes in play even if some individuals in the population are less likely to reproduce. Something along the lines of the sickle cell gene (advantageous to some, yet deadly to others), but more complicated because there is more than one gene involved, and the “condition” is not deadly. In fact, the “condition” probably only acts as a mild lessening of reproductive success for the carrier.