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A gay gene?

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08 Mar 2012 15:10 #636153 by Diable Rouge
Reading Dawkins' proposition that religion is a malfunctioning by-product of our cultural indoctrination towards deference, in which he also mentions our failure to develop genetic immunity to the common cold, it raises the question of why certain conditions persist, even when they provide no evolutionary benefit. Disorders such as sickle-cell disease have long been known to be caused by recessive genes, and given that homosexuality has been noted in all cultures throughout recorded history, but can't be considered learnt behaviour, perhaps it falls under this category. That is not to make a value judgement, only to state that as a practice, it doesn't favour the survival of any animal species where it has been noted, so can its persistence through generations be considered genetic?
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08 Mar 2012 15:16 #636156 by Stumpy Pepys
Diable Rouge wrote:

Reading Dawkins' proposition that religion is a malfunctioning by-product of our cultural indoctrination towards deference …


His argument for this hypothesis in The God Delusion is so flabby and half-arsed that — by the end of that bit of the book — even he gives up on it.
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08 Mar 2012 15:23 #636159 by Ginger Yellow
On the sickle cell issue, obviously the disease itself is not adaptive, but the genetic mutation that causes it is adaptive in single allele form, in malaria-prone countries. And the geographic distribution of the mutation reflects that.

On the main point, it can be considered genetic if it has a genetic component, surely. Which we don't know.
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08 Mar 2012 15:29 - 08 Mar 2012 15:32 #636163 by ooh aah
Is this now the time to start a new thread, where I state in the OP "I've got a pair of ripped jeans, and they're pretty gay"

Was Gene Pitney gay?
Last Edit: 08 Mar 2012 15:32 by ooh aah.
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08 Mar 2012 15:34 - 08 Mar 2012 15:36 #636164 by Wyatt Earp
OK, first we need to define our terms. Homosexuality isn't an evolutionary puzzle, any more than masturbation is. What's an evolutionary puzzle is an exclusively homosexual orientation.

Now, having conceded that that's an evolutionary puzzle, let's immediately point out that it's no more of one, in principal, than any number of congenital conditions that threaten successful reproduction, such as Tay-Sachs or sickle cell. (That's not to say that having a homosexual orientation makes you sick; just that from the genes' point of view it's as if it does. But the genes' point of view neither is nor ought to be the same as ours.)

There are several ways in which things like this can happen. One is that although the condition in homozygotes is "gene-fatal", being a heterozygous carrier of the condition confers some evolutionary advantage that outweighs that. This is unlikely but not impossible in the case of homosexuality.

Another is that though congenital, the condition is not innate in origin, but developmental. There's some evidence that at least some of the time the uterine environment may play a role in male homosexuality, such as the intriguing finding that you're more likely to be gay if you have an older brother, whether or not you grew up together, but no more likely to be gay if you have an older stepbrother or paternal halfbrother. However, this is almost certainly not the whole story or anything like it.

The most likely explanation is that a homosexual orientation arises partly through the developmental environment and partly through innate factors that are polygenic: that is, that arise from a combination of effects caused by many genes in many loci. Such traits don't breed true, because they arise from the unique genetic hand you're dealt rather than from any one of the cards in it, and sexual reproduction involves shuffling the pack. So a polygenic trait presents natural selection with a moving target. Such traits can't be selected for, and they can't be selected against.
Last Edit: 08 Mar 2012 15:36 by Wyatt Earp.
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08 Mar 2012 15:47 #636174 by WOM
A gay Gene, yesterday.

Or possibly the day before. It's been a hectic week.

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08 Mar 2012 15:49 #636176 by Sean of the Shed
I don't think it would have worked in Life On Mars.
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08 Mar 2012 17:32 #636211 by Duncan Gardner
Why at Last! wrote:

a homosexual orientation arises partly ...through innate factors that are polygenic: that is, that arise from a combination of effects caused by many genes in many loci


Careful with that split gay gene, it causes consternation.
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08 Mar 2012 18:03 - 08 Mar 2012 18:04 #636214 by Tubby Isaacs
Why at Last! wrote:

OK, first we need to define our terms. Homosexuality isn't an evolutionary puzzle, any more than masturbation is. What's an evolutionary puzzle is an exclusively homosexual orientation.


Masturbation (assuming we're talking about heterosexual stuff)= pretending you're doing something that would (sans contraception) have a reasonable chance of leading to conception.

Homosexuality= doing or thinking something that can't possibly lead to conception.

The former looks much more likely to be favoured by natural selection to me.
Last Edit: 08 Mar 2012 18:04 by Tubby Isaacs.
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08 Mar 2012 18:27 #636227 by laverte
Good summary, Why, I don't have anything useful to add except this: none of the pre-birth factors that correlate with homosexual men apply to homosexual women. Fraternal birth order, left-handedness, curly hair (in white people) — no correlation.

The vast majority of research into human homosexuality is male-oriented. Furthermore, it's difficult to capture female homosexual attraction in animals. Evolutionary comparisons, eg to masturbation, are obviously problematic when applied to women.

It seems quite possible that the causes of homosexual orientation, if they are biological at all, are different for men and women. That would seem to be another nail in the coffin of the idea that there's a unique gay gene.
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14 Mar 2012 16:58 #638378 by Wyatt Earp
Tubby Isaacs wrote:

Why at Last! wrote:

OK, first we need to define our terms. Homosexuality isn't an evolutionary puzzle, any more than masturbation is. What's an evolutionary puzzle is an exclusively homosexual orientation.


Masturbation (assuming we're talking about heterosexual stuff)= pretending you're doing something that would (sans contraception) have a reasonable chance of leading to conception.

Homosexuality= doing or thinking something that can't possibly lead to conception.

The former looks much more likely to be favoured by natural selection to me.


Not sure how to respond to this, unless you give me your rationale.
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14 Mar 2012 17:03 #638381 by Wyatt Earp
laverte wrote:

Evolutionary comparisons, eg to masturbation, are obviously problematic when applied to women.


I don't see what you're getting at here, really. The general point that it's only an exclusively homosexual orientation that's evolutionarily problematic seems to apply to women as much as men. If not more so, if anything, in that female mammals can only have a limited number of offspring, and can therefore happily make any purely "recreational" sexual activity entirely unproductive of offspring.
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14 Mar 2012 17:17 #638394 by Reed John

There are several ways in which things like this can happen. One is that although the condition in homozygotes is "gene-fatal", being a heterozygous carrier of the condition confers some evolutionary advantage that outweighs that. This is unlikely but not impossible in the case of homosexuality.


I have no idea what this means.

I don't see how the genetic basis for any behavior has much bearing on whether or not it's a good idea. I'm naturally predisposed to want to consume vast quantities of salt, sugar, and fat. Doesn't make it a good idea. I also have no plans to reproduce and Dawkins et al can fuck right off if they want to tell me that's a "malfunction."
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