A reader writes:
Despite the reasonable idea that
straight kin are far better off in terms of their own reproductive opportunities than they would be without a homosexual dangling so magnificently on their family trees.
Back in our ancestral hunter-gatherer past, were there celebrity homosexuals and lesbians whose fame got their siblings lucky? As the bro of a famous homo, I kinda doubt it, though I suppose the artists at Lascaux and Altimira might've been the Neolithic equivalents of Michaelangelo or Rachel Maddow. What's really interesting is the cultural reversal created by contemporary gay families. My gay brother is a parent, but I am not - by choice and surgical intervention. Instead, I'm the Straight Uncle (vs "confirmed bachelor" uncle of the past) who takes his pre-teen nephew to pro football games.
I think the real evolutionary advantage of gay and lesbians, in terms of Why Would Such a Thing Contribute to a Species Survival, is that in the distant past, it provided caretakers for extended families (those hunter-gatherer tribes) who weren't competing in the intra-tribal mating game. My favorite evidence for this is the statistical - though not determinate - correlation between the number of older male siblings and gay younger siblings (ie, a man is likelier to be gay if he has two or more older brothers). Once a woman has added a few men to the mating pool for the tribe's younger women, something shifts gears physically (prenatal testosterone levels?) to provide caretakers who aren't competitors, who have time to contribute non-reproductively to the survival of the whole group.
And who maybe have the time and talent to decorate the cave.