Is homosexuality genetic?

[Bad Lieutenant]

I remember reading a study showing that there is at most a 50% concordance for monozygotic twins and homosexuality. Given their sensory and cognitive architecture (ie: the way they process, interpret and store information) as well as many aspects of their environment would usually be pretty well identicle I take that to mean that homosexuality is resoundingly not genetic.

Paraphrased quote from president Ahmadinejad "We just don't have homosexuality in Iran".

I bet there's some homosexuality in Iran, but nowhere near as much as in the feminist, liberal, gay identity cherishing, monogamous West.

 

[Pup]

I remember reading a study showing that there is at most a 50% concordance for monozygotic twins and homosexuality. Given their sensory and cognitive architecture (ie: the way they process, interpret and store information) as well as many aspects of their environment would usually be pretty well identicle I take that to mean that homosexuality is resoundingly not genetic.

Wait...

If a 50% concordance means that when one twin is gay, the other has a 50% chance of being gay, that's pretty significant.

What's the chance of a random person being gay? Ten percent, maybe, to be generous?

So if you pick a gay person at random, the chance that another person picked at random is also gay, would be 10%. However, if that other person was the first person's identical twin, he would be five times as likely to be gay.

Have I figured those probabilities right, and understood what concordance means?

If so, I'm not sure why a 50% concordance is a sign that homosexuality is resoundingly not genetic. Though twins would also have similar environments if raised together, it seems to indicate there might indeed be a genetic component.

 

[HansMustermann]

Actually, a 50% concordance in something that should have only 10% chance to happen by chance, is incredibly higher than what you'd expect from it being just chance. It's the exact polar opposite of a reason to dismiss it as non-genetic.

As for the Ahmedinejad quote... heh... sorry, there probably are sources even more stupidly unscientific than quoting a politician in a theocracy, but not many. Exactly what WOULD make an Iranian politician -- much less a world-class CT-er and all around idiot like Ahmadinejad -- an expert on how many people have homosexual inclinations? Did he do a peer-reviewed study, or what?

 

[Bad Lieutenant]

There is a medium strength correlation for some genetic characteristics and homosexuality. The point is that none of those characteristics, nor a combination of those characteristics, come close to 100% guaranteeing homosexuality, despite extensive research to identify a genetic cause. The environment holds the ace of spades by a country mile in an "is homosexuality caused by genes or the environment" binary decision. This is most potently illustrated by the study I mentioned above IMO.

As pointed out by an earlier poster, the fact sexual orientation frequently changes during an individual's lifetime is further evidence as if further evidence were required.

 

[Dessi]

There is a medium strength correlation for some genetic characteristics and homosexuality. The point is that none of those characteristics, nor a combination of those characteristics, come close to 100% guaranteeing homosexuality, despite extensive research to identify a genetic cause. The environment holds the ace of spades by a country mile in an "is homosexuality caused by genes or the environment" binary decision. This is most potently illustrated by the study I mentioned above IMO.

Twins can have same DNA, but not necessarily the same gene expression.

For something like sexual and romantic feelings toward others, I'd be very surprised if there were only a few genes which were equally expressed. It may be likely that all humans have the capacity for any sexual orientation, with some genetic recipes making it more likely than others.

 

[Alan]

There isn't a single factor behind one's sexuality. It seems that sexuality is multifactorial, with various things affecting the likelihood of particular sexual orientations. Monozygotic twin studies and dizygotic twin studies seems to suggest genes may play a role, but other factors such as hormonal influences during gestation do as well.

I remember a lecturer in uni doing factor analyses to see how much particular explanations may play a significant role for how many people.

 

[Bad Lieutenant]

There is also the twin test. I forget the exact number but in studies twins share homosexuality something like 8 out of 10 times in comparison to left handedness which is shared in twins 7 out of 10 times.

Sorry, but ********. I do remember the numbers for a study and it was a 50% correlation for monozygotic twins. It would also probably have been much lower had there not been a self-selection bias due to their advertising in gay media rather than sampling at random. They conducted a followup study in fact to address those concerns using the australian twin registry and found a lower concordance...I'll have to dig out the studies...here they are:

~Bailey and Pillard, “A genetic study of male sexual orientation,” Archives of General Psychiatry, vol. 48:1089-1096, December 1991.

~Bailey, Michael J., Michael P. Dunne and Nicholas G. Martin (2000). Genetic and environmental influences on sexual orientation and its correlates in an Australian twin sample. Journal of Personality and Social Psychology, 78, 3, 524-536.

In the (unbiased) twin registry study the researchers found a mere 20% concordance for monozygotic twins and homosexuality. This study is not on J. Michael Bailey's wikipedia page because it is not compatible with the PC gay community activist agenda. BTW, don't forget that twins share the same amniotic fluid so in-uterine testosterone/androgen exposure is not applicable when simply referencing this data.

The "born gay" myth is more disproved and illogical than a room full of cold readers, and twice as pernicious. I hope JREF is more concerned with truth than prevailing/comfortable politics.

 

[Bad Lieutenant]

Twins can have same DNA, but not necessarily the same gene expression.

from the linked article:

The advantage of studying twins is that they start out with the exact same genetic information. Therefore, differences in gene expression are attributable to different environmental factors rather than genetics.

So the difference in "gene expression" is caused by the environment - an environmental influence.

It may be likely that all humans have the capacity for any sexual orientation, with some genetic recipes making it more likely than others.

Sounds likely to me - everybody has the capacity to be a gender normative heterosexual.

 

[TheAnachronism]

the feminist, liberal, gay identity cherishing, monogamous West.

You meant to use another word, surely?

 

[Pup]

Sounds likely to me - everybody has the capacity to be a gender normative heterosexual.

That would also mean that everyone has the capacity to be homosexual, depending on the environment they're exposed to, presumably at a young age, since there seem to be differences in brain structure.

If you're saying that "the PC gay community activist agenda" is trying to claim that gay people can't change who they are because they're born that way, there's not much difference between being exposed to some unknown environmental factor at a young age and being born with certain genes. They're both out of the individual's control, and society's control as well, until the environmental factor is isolated.

And I don't think that living in a society like Iran where being gay can be punished by death, counts as an environmental factor when it comes to gene expression, though it may certainly cause people to alter their outward behavior due to fear.

In the (unbiased) twin registry study the researchers found a mere 20% concordance for monozygotic twins and homosexuality

You said the 50% concordance showed it was "resoundingly not genetic," till we pointed out the problem with that conclusion. Now, when that argument doesn't work, you're saying the 50% study was biased. It seems you've made up your mind first, and are trying to find data to fit.

Twenty percent is still at least twice the chance compared to the population at large, indicating something genetic may be going on--a gene that requires less of an environment trigger in some people, perhaps.

 

[Aridas]

So the difference in "gene expression" is caused by the environment - an environmental influence.

Sounds likely to me - everybody has the capacity to be a gender normative heterosexual.

Capacity? Maybe, for some definition of capacity. Pup's done a good job at beating me to the post, though, so I'll just agree with him, while pointing out that it's more likely to be a variety of factors than just one particular environmental factor. I can make an anecdotal statement and say that at no point did I consciously "choose" who I am attracted to, though. My "choice" was to accept that it was highly unlikely that I'll find a female that I'm attracted to... and rather high that I'll find males that I'm attracted to.

To add to the discussion otherwise, though... I figure that Wikipedia has a little bit to say.

The authors of a 2008 study stated "there is considerable evidence that human sexual orientation is genetically influenced, so it is not known how homosexuality, which tends to lower reproductive success, is maintained in the population at a relatively high frequency". They hypothesized that "while genes predisposing to homosexuality reduce homosexuals' reproductive success, they may confer some advantage in heterosexuals who carry them". Their results suggested that "genes predisposing to homosexuality may confer a mating advantage in heterosexuals, which could help explain the evolution and maintenance of homosexuality in the population".[79] A 2009 study also suggested a significant increase in fecundity in the females related to the homosexual people from the maternal line (but not in those related from the paternal one).[80]

 

[epepke]

If gay was a choice, you'd think some of the anti-gay bigots would choose it, just to 'take one for the team' and prove the point. I know Dan Savage has publicly made the challenge, and so far no takers.

Has a week gone by during which no anti-gay bigot has been caught playing dingle-dangle-dongle wit the requipment of his own gender? (from Frank Zappa)

Anyway, a lot about this choice stuff is silly. Gay or straight, offended at having is called a choice or not a choice, I've seen all four combinations. So saying "I'm offended!" loses its punch when people eventually come to see it as part of the background noise.

Also, it seems to me that a lot of the "choice" rhetoric popped up about 30 years ago when people started using the term "sexual preference." Except that term came from classical behaviorism, which specifically discounted choice and indeed all internal states. They used "preference" as jargon for what most people would call "tendency."

@Ian Osborne has mentioned a common assumption, that homosexuals are less likely to reproduce (and therefore it probably isn't genetic). Others have suggested a kind of "selfish gene" approach, where individual genes in close relatives can get expressed, or a "caretaker" approach based on something a bit more like group selection.

I question the basic assumption, that homosexuals don't reproduce as much. Gay people seem to be popping out kids right and left, and not necessarily with the aid of turkey basters, either. One of my mother's late friends was a guy who was 1) gay, 2) a priest, and 3) had a daughter. That's a pretty varied life right there. I've also met lots and lots of gay men who don't even identify as bi who say "of course in high school I had sex with all the girls." (I didn't get a chance to, and I'm heterosexual.)

A smaller inclination to have heterosexual sex and therefore reproduce may not be as significant as an increase in access, especially for gay men. Heterosexual men have to learn to do this balancing act; volumes have been written on the subject. Too safe, and you don't ever get to touch, and you get told Let's Just Be Friends. Too dangerous, and the Star Trek shields go up and phasers set to kill. This has resulted in ridiculous courtship rituals, almost like mating scorpions, who have to immobilize each other's stingers lest they get killed.

Gay men, on the other hand, can get away with murder when it comes to heterosexual women. Plus, there's the "I can fix him" appeal.

And if gay men don't want to stick around and give all their money to women, who cares? There are a lot of heterosexual men who will step right up, and evolution doesn't really care much, as long as the baby makes it to reproductive age, where the cycle begins again.

This doesn't seem to work so well for lesbians, but then again, female sexuality seems a lot more labile than male sexuality.

I don't glory in these rather nasty aspects of humanity, and just relating them makes me want to take a shower. However, I cannot discount the possibility that it may work like a charm.

 

[Bad Lieutenant]

You meant to use another word, surely?

Nope. The fact that, in the Muslim world, polygyny (and NOT polyamory) is invariably explicitly legislated for seems the cornerstone of their "the sexes are very different" society. In the West males and females are treated as if they are are practically identical - no wonder if there is more homosexuality in the West.

 

[Bad Lieutenant]

That would also mean that everyone has the capacity to be homosexual, depending on the environment they're exposed to, presumably at a young age, since there seem to be differences in brain structure.

Not really, brain structure can change substantially in later life.

If you're saying that "the PC gay community activist agenda" is trying to claim that gay people can't change who they are because they're born that way, there's not much difference between being exposed to some unknown environmental factor at a young age and being born with certain genes. They're both out of the individual's control, and society's control as well, until the environmental factor is isolated.

The point is there are some plausible hypotheses detailing social causes of homosexuality which are derided because they lend support to the idea that being gay is a choice - such talk is incompatible with the gay rights movement for some reason....perhaps homosexuality is so hated by the majority of the world the only way it could gain some level of societal acceptance is if it were not a choice.

You said the 50% concordance showed it was "resoundingly not genetic," till we pointed out the problem with that conclusion.

No you didn't...not from where I'm sitting.

Now, when that argument doesn't work, you're saying the 50% study was biased. It seems you've made up your mind first, and are trying to find data to fit.

I'm familiar with the data from a couple of years ago actually - both studies. Mentioning the 50% concordance study first seems the best way to shatter any delusion of a primary genetic determinant when the superior 20% study backs it up as reinforcement - as if reinforcement were required.

Twenty percent is still at least twice the chance compared to the population at large, indicating something genetic may be going on--a gene that requires less of an environment trigger in some people, perhaps.

A small contributory genetic influence and a very large environmental determinant. That's all I've said.

 

[Bad Lieutenant]

To add to the discussion otherwise, though... I figure that Wikipedia has a little bit to say.

The bias of Wikipedia circa homosexuality has been graphically illustrated in post number 47.

Forgive me for not placing much weight on the "hypothetically possible, although diametrically counter-intuitive (and without evidence) evolutionary advantage of a gay gene" stuff.

 

[TheAnachronism]

Nope. The fact that, in the Muslim world, polygyny (and NOT polyamory) is invariably explicitly legislated for seems the cornerstone of their "the sexes are very different" society. In the West males and females are treated as if they are are practically identical - no wonder if there is more homosexuality in the West.

Ah, that's what you meant. I thought that might be what you were hinting at, but then I thought it might have been a simple vocabulary error. I hadn't read any posts by you previously, so I wasn't aware of your viewpoint.

It's an interesting hypothesis that depends on several assumptions being true, but I'm certainly not convinced. For one thing, I wasn't aware that there was "more homosexuality" in "the West."

 

[Bad Lieutenant]

For one thing, I wasn't aware that there was "more homosexuality" in "the West."

It seems plausible. Especially with homosexual acts being illegal. Indeed, I'm not certain of it by any means...it just seems likely, and I'madinnerjacket seemed to believe it when he said so at least.

 

[Aridas]

The point is there are some plausible hypotheses detailing social causes of homosexuality which are derided because they lend support to the idea that being gay is a choice - such talk is incompatible with the gay rights movement for some reason....perhaps homosexuality is so hated by the majority of the world the only way it could gain some level of societal acceptance is if it were not a choice.

The incompatibility is almost certainly reactionary and largely political, given that the most vocal opponents of homosexuality are, fairly obviously, religious people who claim that it's a choice. Intrinsic in their claim of it being a choice is that it's a horrible sin, one that in the broad sense, is condemned far more than the multitude of other things listed as sins, despite there being no actual reason for such, given that it's a simple system of sin versus no sin for the consequences.

I'd suggest that far too many people have let their views be swayed one way or another by that. Add to that, then, the feeling that I think that many homosexuals hold, that they did not actively "choose" which gender that they were attracted to, and the likely too commonly held false duality between choice and genetics bearing all the blame... well, you get an area where feelings tend to run high and confirmation bias on both sides holds too much sway, in general. My apologies for any grammatical dissonance that one might sense while reading that last sentence.

A small contributory genetic influence and a very large environmental determinant. That's all I've said.

Given that small and very large are relative terms... Meh. I'd suggest that the understanding that it's a combination of both is, by far the most likely. Given lack of enough evidence enough to form a more accurate picture, I'm not going to suggest a ratio.

The bias of Wikipedia circa homosexuality has been graphically illustrated in post number 47.

Forgive me for not placing much weight on the "hypothetically possible, although diametrically counter-intuitive (and without evidence) evolutionary advantage of a gay gene" stuff.

You're quite forgiven. I actually chose not to include the next paragraph in the quote, given the clearly biased view that it seemed to support. Still, I'd be curious how the fecundity study mentioned holds up under scrutiny and whether further test results corroborate the findings.

As for the diametrically counter-intuitive comment... I really can't say that I see how you justify that reasonably, at all. Without seeing the studies that were cited, myself, I cannot comment on your without evidence comment. Naturally, however, you'll forgive me in turn for being a bit doubtful of the veracity of that comment. Given the bias that Wikipedia may well have on this subject, I'd be curious to see whether there are any good studies done that support different conclusions.

 

[Antiquehunter]

Nope. The fact that, in the Muslim world, polygyny (and NOT polyamory) is invariably explicitly legislated for seems the cornerstone of their "the sexes are very different" society. In the West males and females are treated as if they are are practically identical - no wonder if there is more homosexuality in the West.

Having just spent 7 years living in the Muslim world (Afghanistan) let me reassure everyone that homosexuality there is alive and thriving. And based on anecdotal evidence, I would suggest with similar percentiles of the populace. Of course, the Afghans aren't going to self-identify on any poll. They're just going to keep on.... well you know the sorts of things that go on.

 

[Bad Lieutenant]

Having just spent 7 years living in the Muslim world (Afghanistan) let me reassure everyone that homosexuality there is alive and thriving. And based on anecdotal evidence, I would suggest with similar percentiles of the populace. Of course, the Afghans aren't going to self-identify on any poll. They're just going to keep on.... well you know the sorts of things that go on.

As many as San Francisco? (Brighton?) If you say so, although the circles we westerners might move in could give the wrong impression perhaps.