The OP almost presupposes an intelligent creator. Evolution doesn’t really work like that. It also presupposes that homosexuality has one cause and that genetic. (Personally I do believe it’s genetic or at very least physiological and before birth in its origin, but I wouldn’t be surprised if there are many different causes and what “makes” one person gay might be different from what “made” his or her partner gay.
It’s also worth remembering that many homosexuals have biological children and they’re no more likely to be sterile than anybody else, so they’re not at all evolutionary dead ends. In fact a homosexual man or woman hundreds of years ago was probably more likely to have children than one today since the pressure to marry and procreate was more intense and reliable birth control non-existent.
Well, we do have love poems written by an ancient Greek woman, directed towards other women. I’ve never heard that Sappho or her writings were oppressed or suppressed, though I admit I haven’t delved too deeply into the question.
Back to the main question, first of all, sexual orientation isn’t entirely genetic. Studies of siblings, twins, and identical twins seem to indicate that there’s at least some component that’s due to the prenatal uterine environment, and some component that’s due to non-inborn factors (whatever those may be). Second, though, for the genetic component (and there’s at least some genetic component, too), there are a large number of hypotheses. One is the so-called “gay uncle” hypothesis mentioned by boytyperanma: Even if an individual doesn’t reproduce, that individual can still contribute to the success of close relatives, and thus perpetuate es genes. Another hypothesis is that, in addition to genes coding for attraction to the opposite sex, there are also genes that code for attraction to men, and genes that code for attraction to women: A gene that codes for attraction to men would, in a woman, lead her to have more procreative sex and therefore be more evolutionarily successful (and vice-versa, for a man with a gene that makes him more attracted to women). But of course, sometimes these genes would end up in someone of the “wrong” sex. Yet another hypothesis is that there’s some factor which facilitates non-sexual bonding between members of the same sex (which might be useful, for instance, in a team of men hunting mammoths), but that too much of that factor might cause the bonding to spill over into sex. Most likely, I think, it’s a mixture of all of these things, plus a few others we haven’t thought of yet.
Does anyone know what the percentages of exclusive homosexuality are in other animals besides humans? My experience is admittedly limited, but the closest I’ve seen to a homosexual animal is more of an omnisexual who will mate with whatever. Well, that and same sex pair bonding that doesn’t seem to involve sex.
I’m curious, because an exclusive homosexual by definition couldn’t breed, but a non-exclusive homosexual/omnisexual/bisexual could. (Humans are the exception as they have figured out sexual reproduction without sexual intercourse.)
Also, I know that some homosexual humans will copulate specifically to have children, despite preferring the other sex, but, in this case, I’m calling that non-exclusive homosexuality. It’s not like we can tell what other animals actually feel about the subject.
I’m assuming you’re referring to “direct” breeding, not artificial insemination.
I’m about as close to an “exclusive homosexual” as you’ll ever find, but if I really really really had to, I could impregnate a woman. Of course, I’d need Hugh Laurie’s photo on the headboard, or an extremely strong imagination.
In the animal kingdom sex is what we would call ‘rape’ for the most part.
A female homosexual animal would certain reproduce since it wouldn’t stop males from breeding her. Most animals don’t pair bond before or after sex and most don’t have casual sex (there are exceptions to both, but they are the exception rather than the rule and even then different from humans). Sex is for breeding, which is driven by hormonal responses, though some animals are aroused by the hormones of their own gender.
In its modern definition homosexuality has as much to do with relationships as with the sex act itself and I don’t think the animal kingdom is that much use as sexuality among humans is incomparably more complex due to the psychological and emotional importance of sex far beyond breeding.
Well, there’s Kin Selection theories. Which is if one cannot further their own genes, then they can seek to try to increase the selection of similarly related genes- basically their siblings and families. That’s at least what I learned 7-8 years ago in Biology, but I believe this works out better in explanation in animal models rather than humans more so, or at least in societies where homosexuality isn’t a stigma.
Basically the ideas of “super-uncles” and “super-aunts” but that has more validity in the animal kingdom, as I haven’t really seen any research other than a small study in Samoato carry it over to the human species.
But if you’re referring to just species in general- the idea of perpetuation of a species isn’t quite the end goal- its more the perpetuation of YOUR Genes, and then the genes most similar to yourself, and thus indirectly the perpetuation of your species. So a look into “Kin selection” theories might give you more information on that topic.
Another thing is that homosexuality covers a very wide variety of behaviors. When one dog mounts another, it’s attempt at dominance. Bonobos simply seem to enjoy genital stimulation - male, female, young or old it doesn’t seem to matter. Penguins can be, like, totally gay.
Depends on what time period and what city-state you’re looking at - Sparta was different from Athens. What I remember knowing about Sparta was that when the boy moved away from his family into the barracks to start his soldier training, the elder mentor was just a teen/twen, so 5 -10 years older. He took the younger under his wing in every meaning, teaching him the fighting skills as well as taking him into bed at night to bond in every way. Later, at 20, when the boy graduated, so to speak, he went off and had a wife to produce as many children for the state as possible; after 30, he gladly moved back to the barracks to spend time with the men again.
In Athens, for contrast, elder men would take young boys as lovers while having a heterosexual marriage.
Remember that love and marriage didn’t belong together outside Greece during that time, either. You married because your parents choose wisely, to get/ keep money/ land/ prestige and influence, and you had children to continue the family line. Love was something elsewhere.
Again, depends on the state and the exact period.
Well, generally women in the Ancient world were less important over all. Their pleasure during sex was unimportant. Their opinion during public discussions on the Agora was not possible, no participation in the political life. The typical woman stayed at home, did the housework, bore and raised children, and wasn’t allowed anything else. OTOH, the allowed exceptions in Athens were the Hegares - educated women, who could hold discussions with philosophers, and unlike normal prostititues, could choose which man to have sex with. (They were not normally paid, only given gifts). They were regarded as having a proper spirit, mind and soul like a man, while the average housewife was as dumb as a slave or animal in the general view.
The famous exception for homosexual women is of course Sappho of the island of Lesbos (hence lesbian) who had a circle of young well-educated women with her writing poetry. Again, it helps to be rich and from a good family to get a good education, then you could get away with stuff the average housewife couldn’t.
Bruce Bagemihl’s excellent and comprehensive book Biological Exuberance answers this, and it’s different for each species (some 600) in which homosexual behaviour has been scientifically observed. (There are no doubt far more species in which homosexual sex takes place; there are plenty of sexed species for which heterosexual sex has never been observed, just because of the difficulty of observing behaviour in the wild, and even a few in which homosexual sex has been observed and heterosexual sex hasn’t.)
In some species, some individuals of one or both sexes have exclusively homosexual sex. In others, some, or even nearly all, individuals of one or both sexes have frequent homosexual sex as well as heterosexual sex. In still others, homosexual sex or particular homosexual behaviours take place at particular life stages. In still others, it varies widely.
This is a logical and interesting hypothesis, IMHO—one that should perhaps be studied in detail. In particular, it would be interesting to know if the rate of homosexuality increases in areas of high population densities and if so, what stress triggers are involved. If this isn’t an evolutionary pathway, it should be—it’s a very good mechanism of population homeostasis (i.e. low population density/ low rate of homosexuality; high density/high rate of homosexuality. Opinions?
Evolution does not work that way. Evolution selects for genes that help people have more kids, period. Population explosions that cross the Malthusian threshold are bad for the people involved, but the genes only care about whether your children will survive the die-off better than your neighbor’s. Otherwise, why don’t we see population controls in ie predator-prey dynamics in which the predator’s initial success leads to reproduction way past the point of sustainability?
And that’s why it’s silly to compare homosexuality to nearly neutral traits like eye color and handedness. A left-handed caveman can kill mammoths and mate with a female just as readily as a right-handed one; a homosexual one will leave no children at all, which is evolutionarily the worst thing that can happen for a trait.
Infertility might be a better comparison. Remember that infertility results from defects in the very complex human reproductive system - usually a single piece of the machinery breaks down, resulting a wide range of phenotypes that laymen group under the umbrella term “infertility.” Considering how complex sexual attraction and mate-selection processes are, it may simply be really difficult to reliably make everyone heterosexual (and not get sidetracked into fetishes, attraction to old/prepubescent people, and same-sex people.) So any of a bunch of errors in brain wiring can break this delicate mechanism, and homosexuality is one manifestation.
An argument against this notion, however, is that homosexuality is still more prevalent than it should be. Infertility is high partly because people delay child-rearing until they’re well past their peak fertility years; many people who go to infertility clinics are biologically normal but simply too old. Selection pressure against homosexuality should be very strong - a homosexual individual represents a “waste” of resources from an evolutionary standpoint; all the effort a parent puts into raising him or her does nothing for their genes. If you needed to create more redundancy pathways in the brain to prevent homosexuality, it seems like it should be a a worthwhile investment. And human mate selection is actually extraordinarily accurate among heterosexual folk; serious fetishes are orders of magnitude rarer than homosexuality, and people are very good at discerning traits indicating immune function, vigor, social status, and hormone levels (high-testosterone males and high-estrogen females). It would seem that the ability to make these delicate distinctions would be easier to break than the straightforward male/female designation.
athelas: You are neglecting the “sickle cell anemia phenomenon.” It’s possible that certain genes are benefitial towards reproductive success in some combination, but produce homosexuality in other combinations. There is no way to determine how prevalent homosexuality “should be”, unless you know the mechanism, which we don’t.
Yes, that’s a possibility we have to consider as well. But sickle-cell anemia is caused by a single mutation in a specific protein (hemoglobin) that happens to have a specific effect: if all your hemoglobin is mutant than your red blood cells die very fast and you have anemia; if half your hemoglobin is mutant your red blood cells only die a little faster than normal and that makes it harder for the malaria parasite to live in you (they go through a stage of infecting red blood cells).
But homosexuality is not a simple Mendelian trait; there must be more than one mutation that affects it. It’s plausible that the mutation of one protein will have beneficial effects under some circumstances; it’s implausible that mutation of dozens of proteins will all happen to have some sort of beneficial effect.
Even if homosexuality were Mendelian, the evidence would argue against a heterozygote advantage model. Since people with sickle-cell anemia live to about 45, many of them can still reproduce, and some of them likely managed it even in the ancestral environment - yet homosexuals produce no children - it’s a larger evolutionary handicap. If there were a similar balance going on with homosexuality, the compensating benefits of being “heterozygous-gay” would have to be very large, even larger than the benefit of being malaria-resistant in tropical Africa. Such heterozygote advantage should be readily visible, yet we don’t see gays and their relatives having an obvious biological leg up in any environment. (Appreciation of musical theater doesn’t count.)
Yes, it’s clearly not a single mutation, if it is even genetic. But how you go from “not one” to “dozens” is unclear. There’s a lot of room in between. In humans, there could easily be a reproductive survival advantage to males and/or females to form close bonds. A certain amount is just right, and a little bit more tips the scale to sexual attraction.
The idea that homosexuals produce no children is simply not true. One fallacy you are making is assuming the homosexuals are all male. Women in primitive societies, for example, don’t get to choose whether or not they mate and have children. They do what their family tells them to do. Roles are fairly rigid for both sexes. We’re not talking about San Francisco style gays and lesbians here.
The fact that sexuality isn’t simple-Mendelian but instead is influenced by a whole load of genes makes it easier, not harder, to get a sickle-cell-like situation. You could have a situation where each of those genes gives some small advantage on its own, and also nudges the person a little bit closer to homosexuality. A person with a small number of such genes will still reproduce just fine, and just spend a little extra time ogling members of the same sex, say, but meanwhile reap the benefits of all of those separate genes as well. It wouldn’t be until an individual had enough of those genes to drive them to exclusive or near-exclusive homosexuality that it’d be a problem evolutionarily.
Remember, sex is cheap; it’s pregnancy and childrearing that really eat up the resources. It’s not really wasteful to have a bunch of homosexual encounters, as long as you still have a few heterosexual ones, too.