No Roots

Gay Genes

I've got to get this post out of my system... the gay gene thing.

I was interested to see this comment at the bottom of a "scientific" blog post:

While on the subject of press reports, I can't resist repeating the classic headline from Sunday's über-tabloid, The News of the World: 'Cocaine Kate's 3-in-Bed Lesbian Orgy'. (The 'Kate' is Kate Moss, in case you hadn't guessed.) Nothing to do with GNXP, but it's a dream come true!

This triggered a discussion on why lesbians make men so horny.

I have a number of "how does evolution account for xxx" questions but the attraction of men to lesbians has never been one of them. The answer seems obvious: guys who were attracted to lesbians and twosomes passed on more of their genes.

What is more interesting is why there so many men and women who are gay. I have heard a number of theories beginning with "The reason for gay people is ..." but this is wrong. This "reason for" thinking is such a trap. In the context of evolution, there is no reason for anything. Things just ARE. The question is "How would this trait result in a successful strategy for perpetuating genes in the next generation?" For those in the know this is pedantic, but to a lot of people this explanation is essential.

For starters, I'm not going to debate the fact that homosexuality is heritable because I think that has been well documented elsewhere.

So what of the genes? It's possible that there is a single or combination of genes that results in homosexuality regardless of gender… or there could be gender specific gay genes. Given the different roles of men and women in reproduction, I'm going to assume that the gay genes are gender specific. Saying that, I know a number of families where the siblings of both genders are gay.

A few points which theorists may like to address but which I just add as a mental note:

  • there are way more predominantly gay men than predominantly gay women
  • men tend to be gay or straight – few men are bisexual
  • a large number of women are bisexual and few are exclusively gay

Untested but worthy of further investigation:

  • Gay men are better looking than straight men. Has anyone done a symmetry test?

Ok the theories...


  1. Women who bonded as a couple would have been more successful in rearing children than women who were alone. With men buggering off on silly hunting trips or otherwise indisposed due to war and the like, this may have proven a successful survival strategy.
  2. Where men had multiple wives, the wives were less likely to kill each other if they were having sex together.
    [Somewhere in the middle here I assume that the male taste for lesbians evolved. Men who got jealous seeing their wives at it would have passed on less genes than those who joined the party]
  3. And here's the very politically incorrect "I know my friends won't speak to me for 3 months" theory. Let's say that in every tribe, there are a few women who are unable to find a mate. The men aren't selecting them (we'll assume there is some modicum of male choice at work). If the rejects just go about their business and become spinsters so be it. But lets say a couple of them get together. If the male trait for attraction to lesbians and threesomes has already developed, this girlie action could be all the extra incentive some guy needs for getting them pregnant.

Gay Men

I think the only thing that makes sense here is kin survival ie if a gay man helps provide for his sibling's family, his genes may be more successful in the next generation.

Ironically, religious pressure to marry and procreate may have helped propagate gay male genes as it no doubt does today. All those X-gays are just a breeding ground for little gay boys and girls!

From these theories, it would seem there would be many more avenues for a lesbian gene to propagate than a gay male gene and yet the opposite seems to be true. Saying that, there are likely many more bisexual women than gay men.

There are probably mathematical ways this would work out… the genotype of a woman need only have one lesbian gene to be bisexual but needs two to be a hard core "men stand back 300 feet" type. With men, on the other hand, the gene may be completely recessive and when it shows, it's the real deal.

And that's THAT.

To end off, perhaps you could answer a question for me...

How does evolution account for the fact I find baby mammals of other species so damn cute?

Labels: , Furl digg Reddit TailRank Add to My Yahoo co.mments Tuesday, September 20, 2005


Blogger Razib Khan

Ironically, religious pressure to marry and procreate may have helped propagate gay male genes as it no doubt does today. All those X-gays are just a breeding ground for little gay boys and girls!

note that you have to be careful about the math here. for example, a gay uncle is 1/4 related to his nieces and nephews, so, if that gay uncle doesn't have children, than the nieces and nephews need to be 4 times as fit for a "gay" gene to propogate. in other words, even on the biological level there has to be other things going on. last i checked the concordance of homosexuality for males for identidical twins was estimated to be about 1/4 (ie; if you are gay, there is a 1 out of 4 chance that your twin is gay).

How does evolution account for the fact I find baby mammals of other species so damn cute?

the same development genes are at work for all mammals (and frankly, most vertebrates). ergo, the same developmental pathway results in all mammal babies having:

1) bigger eyes
2) bigger head
3) smaller nose
4) no secondary sexual characteristics

etc. etc.

the adaptation that cues you to baby cuteness simply gets turned on for other creatures because the same developmental occurs in them (contrast this with many reptiles, where the babies aren't cute because they are replicas of their parents, instead of "neotonous" miniatures).

btw, your baby is cute.

Thursday, September 22, 2005  

Blogger R

That baby is ME baby (age 1)!

PS: I do understand the math on uncles...I'm suggesting uncle Elliot is helping his sister-in-law turn out 8 good sprogs instead of, say, four. Saying that, from what I've read about the contribution of men to prehistoric family life, they seemed to be more of a burden than a plus! On that point we must give modern men credit for "evolving."

PPS: I've read that the homosexuality of twins is 1/2. I'd dig out the references if it wasn't for this damn day job...

Thursday, September 22, 2005  

Blogger Razib Khan

no, i checked out your photolog. but you were cute as a baby too :)

anyway, the 1/2 number is probably wrong, i know one of the researchers who did some work in that area (michael bailey of northwestern) and he admits that sampling bias was probably at work (twins who submit to these sort of studies are more likely to be homoduplicates because that's more interesting than if there was discordance). a recent large sample with less bias in australia came up with 1/4. these surveys are also problematic because of people in the closet and so forth.

Thursday, September 22, 2005  

Blogger TangoMan

You might want to read about Greg Cochran's germ theory.

Thursday, September 22, 2005  

Blogger R

Interesting. From your link:
"Cochran strayed from his field to try his hand at writing an article on biology - elaborating an audacious theory that human homosexuality might result from a "manipulation" of a host by a germ with its own agenda."

Perhaps there is a germ making men gay, giving them a flare for interior design and great taste in clothes... but then again.

Maybe it's an alien germ from Transexual, Transilvania! Cool.

Thursday, September 22, 2005  

Blogger TangoMan

As Cochran and others note, there are some problems with the Gay Gene Theory.

For an analog to the Gay Germ Theory, check out how Helicobacter Pylori was associated with Peptic Ulcers and the shift in thinking that this created.

Friday, September 23, 2005  

Blogger R

I'm familiar with Helicobacter having long been convinced it plagues me.

I've poo poo'd Cochrane but I agree his theory fits mathematically. There is a more complete anlaysis of his idea here. There is such a complex correlation of traits associated with homosexuality it is hard for me to get my head around it being the result of, say, a small package of RNA.

I am interested to know if there are other gene theories which may fit - for instance what if there is a "horny" gene but in homozygous form it creates a tendancy to homosexuality?

If it is a germ, it may be a benficial one as far as population control goes... ie if the germ spreads more in dense populations, perhaps it can control, as Agent Smith would put it, the parasites known as humans.

Friday, September 23, 2005  

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