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Yes, there is extensive research on this subject in ethology. One hypothesis that seems to be fairly strong is that homosexuality is, essentially, just one manifestation of the broad altruism strategy. Think about what makes altruism in general persist, despite it been seemingly harmful for its carriers long-term: they might not maximize the likelihood of survival of their own progeny, but in sacrificing that, they increase the likelihood of survival of progeny of people from the same family, tribe or larger community - which have a certain amount of shared genes. If you think of the natural selection game as fundamentally centered on the genes rather than their carriers ("selfish gene" etc), this strategy makes perfect sense - your altruism may result in a lot more people surviving and carrying genes shared with you, and down the line, the end result is that population in the future will be genetically more common with you than it has been otherwise - so your genes "win". If so, the tradeoff is in favor of altruism over selfishness, and altruism becomes a selected trait. Now, homosexuality can be seen as an extreme example of that. Every homosexual pair that adopts children (and there are a lot!) is, essentially, forgoing spreading their genes directly, and spending the effort that would normally go into that on the genes of some other person. Now, in this day and age, children often get adopted across large distances; but historically, and obviously in nature, adoption would be from geographically and genetically close populations; so it's a form of altruism that can be favored by natural selection. If you unwind back even further, before family was a thing, any tribe members that don't have children of their own have more time to spend watching, feeding and protecting others' children. Now, you might wonder, why homosexuality rather than asexuality, since the latter would produce the same result? Evolution, due to the mechanisms that drive it, generally takes the path of the least resistance at any given point, even if it results in a very long-winded trek long-term. And it's simpler, from an evolutionary perspective, to "neutralize" the sexual drive by changing its target, than it is to switch it off completely. On top of that, there are some benefits other than children to be derived from sexuality in social species - bonding and mutual assistance, facilitating communication (as e.g. bonobos often use sex) etc. |