username sucks said:
I lack the knowledge to answer any of the questions posed, but...
Q: Is there any biological/evolutionary/whatever reason for homosexuality to exist in humans? [footnote]Not that there's anything wrong with it, of course. I'm just curious if someone who knows SCIENCE could explain.[/footnote]
A: To add to what the other guy said, just as importantly in evolution, perhaps more so, it not having a reason to not exist.
In other words, even if one were to argue that there is zero 'evolutionary purpose', that being gay only detrimental, it hardly matters unless all of an individuals children are gay (and don't have kids), thus halting that genetic line.
An overly simplified version: If you have 4 kids, and 1 is gay, you could argue that you carry a gene that gives a 1/4 chance of gayness. So, now maybe your other 3 kids also have the gene with that 25% chance which they will pass on to their kids. Even if one generation has fewer kids, that gene is still going to get passed on and will continue to do so as long you don't get an unlucky generation where there'd only gay kids, then it's game over, but since that'd just one branch on a vast family tree, the gene still carries on elsewhere.
So, all evolution really says about being gay, or anything else that doesn't seem to make logical sense, is that it didn't impede the parents ability to pass on the genes some other way (other kids). Plenty of theories on how it could be helpful, like how having extra gay male adult provides a better protector/child ratio, but even that isn't necessary. Doesn't have to be good, just has to not kill the bloodline.
Also, need to remember that the whole 'rape is bad' concept is not, I don't think, super relevant to most animals, and even modern humans can be a bit iffy on the subject depending on culture. Point being, everything else aside, it's a bit harder to breed something out when it only applies to half the population, I doubt being a gay woman pre-human provided the same assurances of cock avoidance that it might/should today.
In theory, if you found every gay person, and prevented both them and all their siblings from having children, and did that without fail for even just a few generations, I wouldn't be surprised if you saw an end to the trait. But, it seems to be common enough that that probably covers the entire population, so it is what it is.
