the result of a process complex enough that it’s very difficult to predict the outcome or identify the root cause.
Difficult’s a two-place word, and so I’m not sure it makes much sense to argue about whether or not something is ‘objectively’ difficult, instead of difficult at various states of knowledge.
it carries with it an assumption that disowning gay sons has evolutionary roots, or is ingrained behavior in humans, or is common.
It’s not quite that disowning gay sons has evolutionary roots, but that disowning gay sons is not so heavily disfavored as to be extincted. For example, cultures where childbirth is prohibited mostly die out, and so on. But even less obvious things that have an effect on reproductive success are strongly motivating; in cultures with prohibitions against masturbation, those prohibitions are mostly not followed; in cultures where doctors tell mothers to avoid touching their infants because of disease risk, those prohibitions are mostly not followed, and so on. (The impulse for mothers to touch their babies seems very strong, and also very healthy—it actually lowers disease risk by informing the mother what antibodies she needs to produce for her child, and seems critical for proper psychological development.)
And traditional behavior gives us an imperfect window into the economics of the past, which is what’s under discussion when we talk about historical selective fitness. If gay sons were helpful enough with nephews and nieces that it was as if they had had their own children, it seems to me they would be welcomed and lauded as examples of loving selflessness. But if gay sons were reproductively disadvantageous, and in particular if it was reasonable to expect that homosexuality is contagious, then there’s little cost and some reproductive benefit to forcing them out of the home.
(I should note that the hypothesis that one gene causes both female fecundity and male homosexuality is also consistent with disowning gay sons, but I think that one has other challenges.)
After all, my family didn’t disown me, and it seems like disowning gay sons is becoming increasingly uncommon.
Thankfully, people are much more motivated today by individual and relationship satisfaction, neither of which disowning is helpful with. (My family didn’t disown me either.)
Does it make sense for families to disown children for being the wrong religion?
It suspect it made sense for religions to disown members that fail to disown their children for being the wrong religion.
Does it make sense for families to disown children for being pregnant?
It looks like control over sexuality was a big deal, and as a first-order effect it seems that signals of that control would heavily impact someone’s price on the sexual marketplace. As a second-order effect, it seems that the harsher penalties are for not being controlled, the more likely people are to submit to control. But in less status-stratified societies? Probably not—and it seems like this is mostly a class thing in the societies that I’m familiar with.
This is mostly my speculation, though—I haven’t read much on evolutionary accounts of how parents should respond to teenage pregnancy in various environments. I expect someone has thought about this problem.
And traditional behavior gives us an imperfect window into the economics of the past, which is what’s under discussion when we talk about historical selective fitness.
Traditional behavior is so widely varied, though, that it’s difficult to draw any conclusions. Some traditional societies practiced polyandry, others, polygamy, and still others, levirate marriage, and avunculism, and so forth. Some traditional societies were accepting of homosexuality and even transgenderism. You say that cultures that prohibit childbirth die out, but many diverse cultures have a thriving tradition of monasticism (which is even worse for reproductive fitness than homosexuality!)
If gay sons were helpful enough with nephews and nieces that it was as if they had had their own children, it seems to me they would be welcomed and lauded as examples of loving selflessness.
Would they? “Gay” is a recent category; traditional societies did not attempt to classify humans in that way and it only became popular when religious authorities attempted to criminalize it and early psychologists attempted to medicalize it. Men were not “gay” or “homosexual”, they were more or less inclined towards other men.
And traditional behavior gives us an imperfect window into the economics of the past, which is what’s under discussion when we talk about historical selective fitness.
I think we should keep in mind just how far back we’re talking. I’m not saying we inherited homosexuality from our common ancestor with the modern fruit fly, but at least our common ancestor with other great apes. Framing the question as why would it be selected for in the context of human societies is probably wrong, when what we want to know is why it wasn’t sufficiently selected against given it already existed (I doubt we’ll ever figure what advantage it gave the proto-ape whose social structures we’ll never know). Once a trait already manifests in 3% of the population, it takes work to get rid of it, and even within that 3%, it was doubtful the case that 0% of them reproduced while 100% of heterosexual men reproduced. I’m sure it wasn’t exactly parity, but it’s possible there is no explanation in terms of the organization of human societies except for we’re really optimized to enjoy sex, sometimes that wire gets flipped, and it doesn’t provide an advantage, but it also doesn’t give enough of a disadvantage to completely disappear within 300,000 years.
Don’t forget also, that if some gene combo is necessary but not sufficient, and requires other developmental factors to manifest that don’t manifest in your brothers and cousins (which seems to be the case if it’s only 20% between twins), then when they reproduce, even if you don’t, the gene still gets passed on. Take me, for example. I’m not gay, but I am sterile and don’t want kids anyway. Nonetheless, I have 3 sisters and 13 cousins that have had kids so far. Without doing the exact math, off the top of my head I’m guessing at least 80-90% of whatever I’m carrying made it to the next generation.
Edit: Also, one last thing is we don’t know the prevalence in the ancestral population. Given it’s roughly 100% bisexual in such a closely related other species, it could have been fairly high in the common ancestor, obviously not 100% obligate, but more than 3%, and it actually has been selected against, a lot, just not enough to get us to zero yet.
Difficult’s a two-place word, and so I’m not sure it makes much sense to argue about whether or not something is ‘objectively’ difficult, instead of difficult at various states of knowledge.
It’s not quite that disowning gay sons has evolutionary roots, but that disowning gay sons is not so heavily disfavored as to be extincted. For example, cultures where childbirth is prohibited mostly die out, and so on. But even less obvious things that have an effect on reproductive success are strongly motivating; in cultures with prohibitions against masturbation, those prohibitions are mostly not followed; in cultures where doctors tell mothers to avoid touching their infants because of disease risk, those prohibitions are mostly not followed, and so on. (The impulse for mothers to touch their babies seems very strong, and also very healthy—it actually lowers disease risk by informing the mother what antibodies she needs to produce for her child, and seems critical for proper psychological development.)
And traditional behavior gives us an imperfect window into the economics of the past, which is what’s under discussion when we talk about historical selective fitness. If gay sons were helpful enough with nephews and nieces that it was as if they had had their own children, it seems to me they would be welcomed and lauded as examples of loving selflessness. But if gay sons were reproductively disadvantageous, and in particular if it was reasonable to expect that homosexuality is contagious, then there’s little cost and some reproductive benefit to forcing them out of the home.
(I should note that the hypothesis that one gene causes both female fecundity and male homosexuality is also consistent with disowning gay sons, but I think that one has other challenges.)
Thankfully, people are much more motivated today by individual and relationship satisfaction, neither of which disowning is helpful with. (My family didn’t disown me either.)
It suspect it made sense for religions to disown members that fail to disown their children for being the wrong religion.
It looks like control over sexuality was a big deal, and as a first-order effect it seems that signals of that control would heavily impact someone’s price on the sexual marketplace. As a second-order effect, it seems that the harsher penalties are for not being controlled, the more likely people are to submit to control. But in less status-stratified societies? Probably not—and it seems like this is mostly a class thing in the societies that I’m familiar with.
This is mostly my speculation, though—I haven’t read much on evolutionary accounts of how parents should respond to teenage pregnancy in various environments. I expect someone has thought about this problem.
Traditional behavior is so widely varied, though, that it’s difficult to draw any conclusions. Some traditional societies practiced polyandry, others, polygamy, and still others, levirate marriage, and avunculism, and so forth. Some traditional societies were accepting of homosexuality and even transgenderism. You say that cultures that prohibit childbirth die out, but many diverse cultures have a thriving tradition of monasticism (which is even worse for reproductive fitness than homosexuality!)
Would they? “Gay” is a recent category; traditional societies did not attempt to classify humans in that way and it only became popular when religious authorities attempted to criminalize it and early psychologists attempted to medicalize it. Men were not “gay” or “homosexual”, they were more or less inclined towards other men.
I think we should keep in mind just how far back we’re talking. I’m not saying we inherited homosexuality from our common ancestor with the modern fruit fly, but at least our common ancestor with other great apes. Framing the question as why would it be selected for in the context of human societies is probably wrong, when what we want to know is why it wasn’t sufficiently selected against given it already existed (I doubt we’ll ever figure what advantage it gave the proto-ape whose social structures we’ll never know). Once a trait already manifests in 3% of the population, it takes work to get rid of it, and even within that 3%, it was doubtful the case that 0% of them reproduced while 100% of heterosexual men reproduced. I’m sure it wasn’t exactly parity, but it’s possible there is no explanation in terms of the organization of human societies except for we’re really optimized to enjoy sex, sometimes that wire gets flipped, and it doesn’t provide an advantage, but it also doesn’t give enough of a disadvantage to completely disappear within 300,000 years.
Don’t forget also, that if some gene combo is necessary but not sufficient, and requires other developmental factors to manifest that don’t manifest in your brothers and cousins (which seems to be the case if it’s only 20% between twins), then when they reproduce, even if you don’t, the gene still gets passed on. Take me, for example. I’m not gay, but I am sterile and don’t want kids anyway. Nonetheless, I have 3 sisters and 13 cousins that have had kids so far. Without doing the exact math, off the top of my head I’m guessing at least 80-90% of whatever I’m carrying made it to the next generation.
Edit: Also, one last thing is we don’t know the prevalence in the ancestral population. Given it’s roughly 100% bisexual in such a closely related other species, it could have been fairly high in the common ancestor, obviously not 100% obligate, but more than 3%, and it actually has been selected against, a lot, just not enough to get us to zero yet.