Gay Politics Science

On adaptive success and theories of homosexuality…

The latest issue of New Scientist contains an article – “The In Crowd” – that is both profoundly interesting and yet totally unavailable online. Gradually, I’m delighted to say, this situation is becoming more rare and more of a surprise each time it occurs.

Anyway, the article – written by Joan Roughgarden – contends that: “Same-sex relationships are not a biological dead end. They are a glue that helps hold many animal societies together, and a fatal flaw in one of Darwin’s central ideas.” Here are a few choice chunks of the article that I think encompass most of the article:

Author Bruce Bahemihl, in his book Biological Exuberance: Animal Homosexuality and natural diversity, has catalogued over 200 vertebrate species in which same-sex genital contact regularly occurs. In some species, homosexuality is not very common – around 1 to 10 per cent of all mating. In others, such a bonobos, homosexual mating occurs as often as heterosexual mating. In some species only males participate, in others only females, in still others both sexes. Sometimes homosexuality is associated with pair bonds that last for years, and in others with short-term courtships. This broad occurrence of homosexuality among vertebrates raises the possibility that if it has a genetic basis at all, it has some broad adaptive significance, and is not an aberrant condition just a few species happen to be stuck with.

In humans, moreover, homosexuality is much too common for it to be considered a genetic aberration. Real genetic diseases are really rare, and their frequency inevitably depends on their severity. A disease that is uniformly lethal must arise anew each generation, so its frequency is equal to the mutation rate, say one in 1 million. A disease that causes only a 10 per cent drop in offspring production (fitness) is 10 times more common than a lethal disease – about one in 100,000. Similarly, a mere 1 per cent drop in fitness leads to a frequency of one in 10,000. If homosexuality has a frequency of 1 in 10, the fitness loss could be no more than 0.001 per cent, which is completely undetectable. A “common genetic disease” is a contradiction in terms, and homosexuality is three to four orders of magnitude more common than true genetic diseases such as Huntington’s disease.

All this seems eminently reasonable to me so far. I mean, clearly I’m no expert in evolutionary biology, so my opinion really counts for less than nothing. But on the other hand, as an engaged reader and a gay man I’ve at least got a legitimate interest in the subject and have found myself relatively compelled by the idea that if homosexual behaviour has a genetic component, that at least some of the genes that result in it must have some adaptive utility. The most commonly cited example is that perhaps a gene might exist that in an heterosexual adult provided a significant reproductive advantage of some kind – but which had the side effect of producing a certain proportion of children who were gay. As long as the cumulative effect was to mean that – on average – the familial line would produce more sexually productive offspring than a line which did not have the gene, then it would be clear that the genes that result in gay people had a reproductive advantage.

Of course while that theory has a certain compelling logic to it, it doesn’t (perhaps shouldn’t) have anything to say about what it means to be gay in this context. In other words – it makes no statement that homosexual behaviour is itself somehow useful or positive with regard to human behaviour, survival or evolution. Homosexual behaviour then, is not considered adaptively useful.

Now back to Joan Roughgarden’s piece (carrying on directly from what was written above):

Indeed, I challenge the presumption that homosexuality leads to any reduction in fitness whatever. Throughout history and across cultures, homoerotic attraction has not precluded heteroerotic attraction. And there is little evidence that people who feel homoerotic attraction have, as a group, any less Darwinian fitness than those who don’t. After all, many exclusively heterosexual people do not have offspring either. Even if those with homoerotic attraction did have marginally fewed children, they might make up for it by a better chance of survival – during wars, for example, when homoerotic bonds might lead soldiers to protect one another more vigorously.

So what then, is the adaptive significance of homosexuality? Homosexuality has many uses, much as the ability to speak does. Homosexual contact is a way to communicate pleasure. And I suggest that homosexuality is a social inclusionary trait – that is, it provides animals, including perhaps humans at times, with admission to social groups. It evolves, I suggest, whenever same-sex cooperation helps achieve an evolutionary successful life: to survive, find mates and protect one’s young from harm. This plays out in different ways in different sexes and species. Sometimes, as with bonobos, same-sex cooperation provides group security and access to food that females need to successfully rear their young. For others, such as male Savanna baboons and probably some whales, it provides the allies they need to survive conflicts so that they may later mate. But the unifying principle is the same – homosexuality cements relationships that are crucial for a successful life.

At which point, I’m afraid, I think my scepticism comes to the fore. It seems to me that any theory of homosexuality that operates in direct opposition to people’s experience of contemporary human sexuality seems to be at least flawed. While bonobo homosexuality might be seen to be useful in the creation of social inclusion, often exactly the opposite occurs in human society. Eve Kosofsky Sedgwick’s classic book Between Men specifically talks about the continual need to disavow sexual components to male homosocial relationships (ie. male-on-male friendship / bonding relationships). We’re all familiar with this kind of experience – that the most common and most potent sources of anti-gay tirades are tightly-bound social groups of men. At the very least more is going on in those situations than simple homoeroticism bringing those men together to express solidarity and closeness. Even at our most open-minded, surely we have to state that in those circumstances, the fact that any vestigial or situational erotics have to be so vigorously denied makes it clear that there’s a distinction to be drawn between homoerotic behaviour, homosexual behaviour and homosexual identities that is much more complex than anything that Roughgarden supplies us with.

I will of course give her the benefit of the doubt in this case – the article is evidently a truncation of a body of work that no doubt includes a massive set of sample data from which to draw conclusions as well as the applied expertise of a lifetime of training. If I get the chance to read any more of her work, I will make sure that I do so vigorously. But in the meantime, I’m afraid I must remain interested but unconvinced.

18 replies on “On adaptive success and theories of homosexuality…”

I’m probably being insultingly obvious here, but it seems that there is a major stumbling block here: the presumption, at root for everything else said in relation to it, that sexuality is merely a tool for the propogation of a species via reproduction. Surely this idea would have to be set aside before anything really meaningful could be said?

i don’t think we can use civilized history to discount a theory based on evolution, because humans have many features that had clear evolutionary advantages before civilization, but are no longer useful. hair, for example, was useful for keeping us warm (among other things). but we now have blankets, hats, and all sorts of external tools for doing that. this doesn’t suggest that hair didn’t become genetically common because it kept us warm. it just suggests that as a species we’ve moved on from (unintentional) evolution. so while i’m not convinced by the argument you’re refuting here, i’m also not convinced by your refutation.

I don’t see that there is any contradiction between homosexuality as a socially-beneficial character and homophobia as similarly socially-beneficial (in a purely local sense). Both can serve to cement social relationships, even if the latter does so in a rather less constructive way. Also, while there is a fair amount of evidence for there being a genetic basis for homosexuality (or at least a predisposition to it), homophobia seems likely to be a largely memetic phenomenon, and therefore effective over a much shorter timescale (by the same token, the gay identity is clearly a memetic construct, which seems to have been somewhat effective against homophobia on the scale of 20-30 years). The fact that homophobia has been a recurring memetic strategy for a few centuries in no way undermines the suggestion that human homosexuality may have conferred evolutionary benefits on the order of thousands to millions of years — and indeed may still be doing so.

I’ll second what Matt and Scott have said. You must not confuse long-term, seriously long-term, evolutionary processes with relatively recent, relatively localised, cultural developments. Indeed, for that matter, neither should relatively juvenile cultures, such as Pauline Christianity, or fetal cultures like post-Victorian sexual repression, be taken as meaningful developments. It’s far too early to make that call.
Of course, that’s all utterly useless if you’re having to deal with with people’s beliefs today, but still.

To MacDara – actually I think I’m more at risk of making that assumption than Joan Roughgarden is. Her specific argument (probably poorly represented by me) is that sexuality has a wide variety of uses that aren’t related exclusively to the immediate creation of offspring. On the other hand, it does still kind of come down to reproductive success in the end though – I think that’s inevitable when you’re talking in terms of the survival of a gene that seems superficially to be directly counter to helping that genome survive.
To scott – I think you can probably tell by my last couple of paragraphs that I can see ways in which you could back up the position that homophobia in the homosocial could be a result of precisely those feelings that Joan would posit exist – so I don’t think I would call my comments a refutation, more of an expression of doubt or suspicion that – at the very least – indicate that there’s clearly a few nuances of the argument that are missing from the article.
To matt – can you actually think of any ways in which at the local level of the individual, homosexual behaviour is likely to have been advantagous to them having children and hence spreading the gene further? Because all the examples I can think of end up saying that certain mixes of gay-related genes could perhaps afford advantages to individuals, but that at the end of the day those people who are “just, y’know, gay” are simply much less likely to have children. That’s got to be a problem for that kind of theory, surely?

Ben – and yet the problem remains – can you imagine a context in which a man who felt himself to experience limited or no heteroerotic desire could be seen as having a reproductive advantage?

Well, lots of women seem to be attracted to gay men, and I know a fair number of gay fathers, including my own. But that’s purely anecdotal, and on such a short term as to be evolutionarily irrelevant. On the other hand, the notion of a separate, exclusively-gay identity is such a recent invention that it has to be similarly negligible. Even if we accept it as a wholly-genetic effect that does indeed limit the individual’s reproductive potential, there remains the argument you yourself cite: of homosexual behaviour somehow conferring an advantage on heterosexual siblings who still carry (at least part of) the gene, either by increasing their chances of reproducing (“have sex with me because my brother is *fabulous*”) or increasing their offspring’s chance of survival (eg, by altruistic intervention as a doting uncle). Genetic reproduction is certainly at some level a matter of brutal chemistry, but in the context of social animals there is a lot more going on than that.

And another thing… (god, I seem to be in blathering mode tonight) One could argue that homophobia is a pretty strong force for the propagation of a “gay gene” in that it encourages people who would naturally be predominantly homosexual to enter reproductive heterosexual relationships in order to hide their predilections. And since homophobia would be lost without homosexual targets, both tendencies could be seen as interdependent, almost symbiotic. (Ick, what a repulsive argument. I’ll shut up now.)

It’s important to note that genes do not determine action, but rather weight it. There is no gay gene in the sense that everyone with that gene is necessarily exclusively homosexual, though it seems widely accepted that there are genes that make homosexuality more likely. Perhaps there are simply genes (or lack of specific genes) that counter the tendency to be very much more strongly attracted to the opposite sex. This wouldn’t in itself drastically affect a person’s probability of reproducing, but would level the field for psychological or sociological influences to determine homo-, bi- or heterosexuality independent of genes.

The most important bit: “Homosexuality has many uses, much as the ability to speak does.” That homosexuality exists across species at a fairly constant rate suggests there’s an inherent purpose for the perpetuation of each species. My own belief is that it is the ultimate fallback, the buffer against complete obliteration of a species. Jared Diamond’s ‘Guns, Germs and Steel’ makes the point that most communicable fatal diseases run their course through a population, but stop shy at roughly 10% (correct me, it might be 6%). This percentage is fairly constant. Any heterosexually-transmitted pathogen would be defeating its own perpetuation to wipe out an entire genome upon which it is dependent; the buffer allows for a group with immunity to rebuild the genome. Under the stress of the loss of the rest of the non-homosexual members in a genome, homosexuals may modify behavior sufficient to allow reproduction and rebuilding of the genome. This is at genetic level. At memetic level, homosexuals may represent the perpetuation of culture, the operating system of the genomic hardware. For example, the mahu of Hawaiian culture were the keepers of the Hawaiian language and history; when Hawaiian culture was suppressed, the mahu kept the culture alive until it could be documented and restored to Hawaiian people. That homosexuality has other social purposes only ensures that a genome does not obliterate its fail-safe. There may be some rational for the extreme reaction (disgusting as it is) by a percentage of the hetero population; it keeps them at opposite ends of contact, reducing the chance that heteros infected (with pathogens or with aberrant memetic materials) do not harm the fail-safe. My personal guess is that there would be a correlation in population size — roughly 10% of the population is rabidly anti-homosexual. Thanks for being our fail-safe, Tom…this begs another question: is blogging another method by which homosexuals can now “keep the culture”?

Tom, AFAIK, your instincts are right. I’ve long supported ‘genetic homosexuality’ because it both seems the simplest and most powerful explanation, and because it seems the most acceptable: if gays are gays because of their genes, attempts at cures are hopeless– with much saving of misery.
I’ll have to buy the current issue, but, from what I’ve seen quoted, Joan Roughgarden doesn’t understand the basics. If she meant “a fatal flaw in one of Darwin’s central ideas,” the woman is a fool–nothing she has said works as a flaw in Darwin. Evolution happens to populations, not individuals. (Anyway, Darwin is dead: if he had wrong ideas, so what? Gravity still pulls you down even if Newton never transmuted lead into gold.)
Put crudely, individuals don’t have “reproductive advantages”– traits do.
And I think you’re very wrong about: “We’re all familiar with this kind of experience – that the most common and most potent sources of anti-gay tirades are tightly-bound social groups of men.” Well, who would you favour someone you had slept with or a stranger? You have to see that sexual relationships would make these kinds of organisations much less stable.
There is also (and I don’t think anyone has mentioned this so far) the ‘spare uncle/aunt’ theory — a few fallback relatives if blood parents get killed by violence/disease/childbirth would also be useful, as would extra hands hunting etc.
But to me, gay men (not all,obviously) seem to understand social behaviour and charm more than straights, and I’m not sure that large societies could survive without a few.

Does that latter point work equally well for lesbian women? Obviously there’s no obvious reason for saying that the genetic advantages conferred by some measure of homosexuality are necessarily symmetrical, but I wonder how much of that understanding of male homosexuality is a myth that seems somehow less stable if brought alongside the complementary case.

It’s likely that there is a proportion with a predisposition to homosexuality. It’s possible that at a young age, there was a stimulus that triggered homosexuality. The function of homosexuality might have been a throwback to an ancient evolutionary time when a fish would be capable of changing sex in case there is an unequal proportion of male and female. The clownfish, from a recent issue of the TIME Magazine (USA edition), can change from a male to a female in the event that his mate and children have been killed.
I heard in biology, though I might have misunderstood, that the vertebrates have four times more chromosomes than the closest non-vertebrates, the Echinodermata. This diversity allows the Chordates, which include human beings, to become larger than other animals. The size of dinosaurs, whales, and elephants should serve as an example. Of course, the giant squid could be the disproof, but I’ll continue.
This complex mass of genes allow us to grow in size, but also carry a risk that mutations will propogate and carry over long period of time, eventually resulting in a definition of attraction between same-sex individuals.
It is possible that same sex attraction was not just a mutation, but an accumulation of mutations that eventually became entangled in the mass of DNA that we have, most of which are junk.
In an environment with equal proportion of male and female, a competition for food and survival, and the fact that male can produce millions of sperm but female can produce only one baby in a lock step succession, it may be necessary for a male to aggressively take more than one mate, especially when he is more prepared for an hostile environment.
Another thing to consider is that the culture involving homosexuality arises at the same time as heterosexuality. Therefore, the moment that people were able to communicate and make drawings on the wall, it was already very well-present in a tribal situation and accepted as a normal part of life. Only when the population increases that people isolated from such groups forms opinions about them that gradually become homophobia.
When we recognize the possibility of same sex attraction, culture follows to integrate it, whether by ostracism or by giving them a superhuman adulation, as in the case of the Native Americans. Without such attraction, we would not even be talking about it and our entire society would be completely different.

Was Darwin Wrong About Homosexuality?
Joan Roughgarden, a professor of biology at Stanford University, California, claims that “Darwin’s theories are inherently flawed.” Was she convinced of Darwin’s error because of it’s circular logic? Perhaps, she realized that the t…

My thoughts on homosexuality and genetics. I have wondered if Homosexuality and the hunting instict..gene’s that control the adrenline response in humans could be the culprits. Also, in the sifting process that occurs in jr highschool of who gets picked last or the fear of being picked there a weeding of less
viable reproductive males going on? Like wise coarsely is Lesbianism a Protect the eggs and offspring biochemical response. The male being seen as a predator. Consider modern response to
Males seeking Children as mates, and Women seeking Males as mates. Though Socially now it is being frowned upon. In and before Our Grandparents Generation it was quite common. I have seen a program on Baboons where the Male adult baboon seeks a child as mate as a stronger
sureness for not being rejected as a suitor.
Certainly the biggest hetrosexual male fear of being labeled homosexual is that Females will reject him as a potential mate. Otherwise, what is the issue? simplely pleasure. Culturally the Social Meme idea is a strong one as well, Cultures that are more Homophobic also have Higher cleanliness issues as well surrounding fecal cleanliness. Consider witch craft in north africa is considered possible when the left hand used for anal care is placed in the common food bowl.Other responses to be considered is the focal warning leadership response, How humans respond socially to one person warning many. Which can be even supstitued by a telivison marking post. The meme accept non accept biochemical response for danger or non danger would also hairtrigger adrenline levels i think.
That’s my theory anyway.

“Cultures that are more Homophobic also have Higher cleanliness issues as well surrounding fecal cleanliness.” What? Where did you get this? The Japanese were probably cleaner than their Western counterparts yet until the arrival of strong Western influence, homosexuality wasn’t considered a problem. I think you are just trying to say that cultures under strong Abrahamic religions (Christianity, Judaism, Islam) are more homophobic which is true.
Today most men today don’t even identify themselves as homosexual until their 20s. Think back hundreds of year ago when many (most?) men and women wed as teenagers. Marriage could easily be viewed as something that was the culmination of love or something that was a social duty just like hunting for food or preparing for winter. For humans it isn’t completely a genetic deadend .. that would be sterility.
I personally agree with Joan Roughgarden. Homosexuality could help form and maintain large societies by reducing tensions/in-fighting that inevitably arise among men in such societies; more importantly among the elites in the society.
To “The most common and most potent sources of anti-gay tirades are tightly-bound social groups of men”, I would say that first you must identify two groups (gays and non-gays) and then you must identify one you’re not in with something negative. You can replace sexual orientation with race or ethnic group or caste or high school and you end up with a group of tightly-bound social groups of men with something negative to say about some group they don’t belong in.

I’d really recommend having a read of Between Men – it talks a lot about the ‘homosocial’, ie. male friendships and what it they rely on. Close male friendships are pretty much necessarily based on the understanding that there are no sexual motives that could be threatening. It’s a rare friendship that can maintain itself under the impression that one participant wants to have sex with the other – and that’s as obvious in heterosexuality as it is with gay people.

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