This study does not prove that people aren’t born that way. Of course there is no “gay gene.” That would make no evolutionary sense. It has to be a complex of them that, combined, cause it. Plus this seems to ignore pre-natal environment. There’s some evidence that this is a cause as well.
[Friday-morning update]
And then there’s this: “Genetics may explain up to 25% of same-sex behavior.”
“Of course there is no “gay gene.” That would make no evolutionary sense.”
I don’t know. From an evolutionary standpoint, men are disposable; your relatives share many of your genes, and all your male relatives share exactly the same Y-chromosome, mutations aside. And it only takes one male relative to pass those genes on through dozens of women to hundreds of kids.
So I’d say there could well be an evolutionary advantage for a fraction of men to not be interested in women and therefore not make kids, freeing up their time to do other things that might help their relatives have more kids. And if it’s a recessive gene, many people could carry it but not express it.
I’m not saying it is true, but it’s far from clear to me that there wouldn’t be genes which would expend disposable men in order to pass itself on through their relatives.
“So I’d say there could well be an evolutionary advantage for a fraction of men to not be interested in women and therefore not make kids, freeing up their time to do other things that might help their relatives have more kids.”
But you don’t need gayness for that. You only need a low sex drive. They could still be “interested” in women but not interested in spending time with them.
Also a low “care for the kids” factor on some males will produce the same effect.
There are ways that homosexuality could evolve as a population control measure and/or to allow some men in groups to not be distracted by children. Group selection as part of evolutionary theory is not a new thing, although it was out of fashion for a while. The latter could always be around, while the former would generally be triggered by environmental conditions.
Seems a lot more complicated to evolve than a (psycho)social norm that children should be cared for by their mothers.