What is the evolutionary advantage of homosexuality?

I am suffering from a bit of cognitive dissonance on this issue. I believe both that the tendency towards homosexuality is inherited and that any trait that leads to the organism being unable to breed (or choosing not to breed - there is effectively no difference) will be quickly bred out of the species.

So how am I to reconcile these two views. My best shots (which are pretty weak) are below;

1: Homosexuality is relatively new to our species and there have always been taboos against it. Thus many homosexuals breed to avoid being outcast from society while secretly pursuing their proclivities in private. Ironically, now that homosexuals are free to marry as they choose this theory would lead to their extinction within a generation or so.

2: There is some advantage to having someone with a man’s build to stay at the camp while the males are out hunting. Gay men can nuture but they also are better able to fend off predators than a woman. Thus a man who begets the occassional homosexual male will have a better chance of his progeny surviving. In this case the homosexual is a special type of worker bee. He will never breed himself but he will nevertheless play an important role in the community. This does nothing to address the presence of lesbians in our population however and no doubt the analogy will be distasteful to some (and just seem idiotic to others).

Notice I leave out bi-sexuality for the sake of clarity, but also because I could make an easier argument for it thus I have no dissonance to contend with. I could see bi-sexuality providing an outlet for sexual behaviour when the preferred choice of mate is in short supply thus lessening the chance of violence when fighting over mates but allowing the subject to keep a high sex drive for when a member of the opposite sex eventually becomes available.

Pure and exclusively homosexual behaviour seems much more difficult to explain from an evolutionary perspective. If homosexuality were chosen like one’s religion or house color for instance then I wouldn’t have this problem but there must be something I am missing to make my two beliefs mesh. Either that or one of my axioms is faulty. Do twin studies back-up homosexuality as being an inherited trait? What is the state of science on this issue?

There is no teleological reason for it.

Natural selection simply doesn’t work that way. There are hundreds of thousands of little variations that neither help nor hinder the species as a whole.

It’s a weak link. Out of the twin study, guys with a gay twin only had a higher chance of being gay. I’m too lazy to dig up cites right now but I think it was 50% or lower. Since they are genetically identical it demonstrates that sexual orientation is not purely genetic and certainly can’t be simulated with one of those high school biology Punnett squares.

Nobody really knows why people are gay, there are all sorts of complicated theories out there to explain why having a gay uncle might be an evolutionary advantage (as kamikaze bees show, an evolutionary adaptation doesn’t have to be beneficial to the individual to be selected for) but it could also be environmental since twins tend to grow up together and, more importantly, share the same womb. I think they did a bunch of experiments back in the 80s trying to produce gay mice or something by sticking hormones into the pregnant mother; I dunno if that ever got anywhere.

You must remember evolution doesn’t do what’s best, it does what WORKS.

And by that it means whatever is able to reproduce the most. Without killing off its host.

Since heterosexual people commonly have homosexual children, homosexuality is not necessarily a product of evolution. It doesn’t figure in.

Because all evolution cares about is the ablity to pass your genes on so you can reproduce.

Demographic population rates for “strictly” homosexual people are fairly low and are generally 5% or less of total population. Also, you are correlating gay=non-breeding which I don’t necessarily follows as a conclusion historically in human societies. Being a lesbian would not prevent you from being impregnated in an arranged or forced coupling, and gay men can often make children by being creative about their fantasies if it is socially expected.

In addition there is the not all that illogical hypothesis that gay “uncles” and “aunts” (if non-breeding) could actually be advantageous for human group survival by giving a disproportionate amount of their resources to the tribal/family group while taking less resources overall than breeding couples.

So the main facts are

1: It’s too small to be a hit on the genome and

2: It might actually be advantageous.

The queer gene’s not likely to be disappearing anytime soon.

What are you basing this on? Cite?

You know better than I do, "The facts are…cannot be followed by “might” unless it refers to physical strength.

[anecdote] Of the dozen or so lesbians I know personally, at least four have gotten pregnant and given birth. Two others have children but I think they are adopted.

Even if homosexuality is not purely genetic, it would still be under the pressure of evolution. Even if it is genetically possible for every person in the world to become homosexual, the evolutionary question still stands. Because why did evolution make this possible in the first place?

I like this argument. It would be good for the tribe to have some skilled interior decorators and some aesthetically minded clothes designers.
Another thought could be that it was too difficult for evolution to make heterosexual love very strong while avoiding homosexual love.
I would like to hear if Blake has anything to say.

A fair number of mammalian social structures such as those of wolves include non-breeding adults to help look after the kids. Given the horrendous amount of effort that goes into raising a child, it makes sense that you can produce more kids by designating a few of your population as non-breeders and have them look after their neighbors than you can by having those same people simply spam the environment with more children.

Just a WAG. No actual official status in evolutionary biology or sociology.

Suppose that the gene involved made humans like sex with men more. Then women who inherited it would spread that gene more. Men who inherited it would prefer men. But the gene would continue to be part of the pool.

Some traits survive because they are gender related. The gene for hemophilia is carried by women, but expressed almost always in men. Although until modern times, male hemophiliacs rarely lived to reproduce, the gene did no harm to the women who carried it. The male hemophiliac’s sisters would pass along the gene to the next generation.

Likewise, the trait of male homosexuality could be gender related: carried by the female line, but expressed in the male line.

I read an article in New Scientist where one theory is that the gene for it is helpful in regards to fertility in general in heterosexual couples, with the side effect that it increases homosexuality as well or something like that. Sorry cant cite it directly

Ie that homosexuality is a byproduct of another genetic advantage, rather than genetically advantageous in itself, which explains why it doesnt die out despite not being obviously advantageous in that particular form.

The other obvious possibility is that most homosexual people reproduce rather than being exclusively homosexual anyhow ie its not an inherently disadvantageous gene anyway.


Pay no attention to him. He just blethers on about tigers burning bright in the forest of the night - and he can’t even spell “tiger”, come to that.

But can he spell “rock”?

Humans, especially in modern societies are no longer competing for survival. Without competition for food and/or mates, there can’t be any natural selection. If homosexuality is purely genetic, it doesn’t need to have an evolutionary advantage to exist - the same way disabled, retarded, blind, deaf and any number of congenital illnesses exist. A person can have a trait that is neither beneficial to himself or to his species and still live a long productive productive (and usually even reproductive) life!

Well, he has always impressed me when the discussion turns to evolutionary questions, even if he doesn’t use spellcheck.

What is this about tigers you are talking about?

The poet William Blake (1757-1827), who wrote The Tyger.

haha :slight_smile:

The OP fundamentally misunderstands natural selection. The heritable unit isn’t the trait, it’s the gene. So you don’t ask yourself, “what is the evolutionary advantage of homosexuality.” You properly ask yourself (assuming any genetic predisposition) “what is the evolutionary advantage of the *gene * that predisposes to homosexuality.” The answer is, we don’t know what those genes are (if they exist) and we don’t know what they DO, so we can’t answer the question. But it’s hardly a paradox. I have no problem imagining an advantageous gene which, as a byproduct, predisposes a certain percentage of its carriers to be gay. Particularly if that predisposition only expressed itself under certain circumstances - for instance in the presence of other genes, or in the right environment. And in fact there’s evidence that not only are genes a factor, but so is the hormonal environment in the womb.

I’m pretty sure I’ve read the same article, and IIRC gay men have more fertile aunts or somesuch… hey up, I’ve found the relevant New Scientist link, which explains all.