Is there a gay gene?

Ken Natton

Quote by Simon Bridge

There is a rich variety of human sexual identification - beyond the black-and-white definitions that many people seem to want to saddle themselves with.

I wholeheartedly agree with that Simon, that is exactly the point. I don't adhere to the belief that sexual orientation is in any way genetically programmed, but it is an idea that seems quite persistent on forums like these, and if a behaviour is genetically programmed, then it is reasonable to seek an evolutionary explanation for it. The usual theory I have seen offered is that homosexuals help to nurture the young of their hetrosexual siblings. I see very little evidence of that phenomenon in the human population.

And though I understand that there is homosexual behaviour observed in other species, I am much less than convinced that it is really exactly the same thing as occurs in human society. But to discuss my thought processes on that point would be way outside the normal discussion limits for a biology forum!

Simon Bridge

One of the problems talking about this is the idea that the genetic code is like a computer code ... that it is a set of instructions that determines everything about you.

This is basically untrue and yet the idea keeps getting circulated.

I like to tell people it is more like a recipe (also an oversimplifcation)... it takes a lot on context. You cannot put human DNA into a chicken egg and expect a human to hatch. It's the wrong context ... similarly a recipe may tell you to bring water to boil but neglect to tell you the altitude (air pressure) to do this at. Water boils at different temperatures in different circumstances but most cooking happens under predictable conditions so the recipe leaves that stuff out.

Each step at the genetic level is quite simple, but the possible variations in interactions mean the overall process of life is very very complicated.

I think there is a valid, bit tricky to pursue, scientific question about the extent to which genetic characteristics affect our social behaviors. It may lead to a more informed examination of our social structures. I somehow don't see this happening though.

Hypercharge

wow...again, I'm making things more complex.
Concerning homosexuality: I say it's a merely psycological attribute you decide for yourself, not your genes. ("Homosexuality has been observed in over 450 species, homophobia in only one.")

So, back to tahayassen's questions: (if anyone would answer differently, feel free to post and do so.

Are gay people born the way they are? Or is it something they learn?

I might answer "maybe" to the first, and "likely" to the second.

If you answer to "yes, gay people are born that way" to the previous question, is it still possible to be gay without being born that way?

Then they'd become it later in life (=learn)

If they are born that way, is it something they inherit?

Most likely not. (see Ken Natton's post

Spoiler

Okay, at that point, the issue does become much more subtle and more complex. I would reiterate the point that if homosexuality is genetically programmed then it will not be a question of a single ‘gay’ gene, it will be much more complex than that. However, there is an interesting parallel with the determinant of sex. Steve Jones’ book, ‘Y’ explains that the determination of male or female can be traced to a single gene that exists on the ‘y’ chromosome. Obviously, it takes a great deal more than one gene to govern all of the anatomical changes from female to male, and almost all of the genes involved are dotted all over the genome on various chromosomes, and thus females have them as well as males. It is just that the individual gene in question, located on the ‘y’ chromosome, is the one that triggers the sequence in embryonic development that drives the change from female to male. It does not even follow that females don’t use the genes in question. It is quite likely that the same genes serve many other purposes during embryonic development used by both females and males. But the particular sequence of maleness depends on a specific gene located on the ‘y’ chromosome.

There is another similar gene called ‘distalless’ because, before it was properly understood, certain alleles were known to cause distal elements to be absent in the fully developed organism. So one fascination of distalless is that it is a gene that is pretty universal across species – both humans and fruit flies have it for example. And certain alleles in fruit flies can cause then to be born without feelers of even legs. In humans it can cause serious malformations of a similar nature. Again, clearly one gene cannot govern the formation of an entire limb. The point is that distalless is critical in the triggering of the sequence that leads to the formation of a whole limb.

So it is possible that a single gene could be identified that a certain allele of that gene could trigger a sequence in embryonic development that leads to homosexuality in the mature organism. But it is also entirely possible for some organisms to have that allele and not be affected by it. In the way that, not everyone in a family known to have the gene that causes breast cancer actually develops breast cancer. Not everyone in a family known to have the gene that causes sickle cell anaemia necessarily have sickle red blood cells. The question I once posed is whether it is possible, if homosexuality is genetically programmed, for it to be maintained by evolution at a certain proportion in the population. And the answer came that yes it is. The suggestion is that the prevalence of a certain trait in a population could affect the selective pressure that acts on it, such that, in the manner of a closed loop control system, it finds a balance at a certain proportion in the population. And that then raises the possibility that other factors could also act on the selective pressure such that the balance point changes, thus explaining why that proportion is different at different times. See what I mean about more subtle and more complex?

)

If it's something they inherit, is there a particular gene?

Definitely there's not one, but several genes. Yet I'm not keen on finding out which ones( if they exist ) because I fear selection of people.

Pythagorean

Not peer-reviewed, but references peer review:

When homosexual men smelled the odor of male sweat—more specifically, a chemical in the male hormone testosterone—their brains responded similarly to those of women.

The findings suggest that brain activity and sexual orientation are linked. It also supports an opinion held by most scientists, that people are born—not bred—gay.

"This is one more line of evidence that there's a biological substring for sexual orientation," said Dean Hamer, a geneticist at the National Institutes of Health in Bethesda, Maryland.

http://news.nationalgeographic.com/n..._gayscent.html

lisab

Not to derail this thread, but it's very closely related - is there a straight gene?

Ken Natton

Quote by lisab

Not to derail this thread, but it's very closely related - is there a straight gene?

I am aware that you are not really interested in the answer to that question - that is not really your reason for posting - but for what it is worth, simple logic tells you that if there is a 'gay' gene then there is also a 'straight' gene. Of course the gay gene and the straight gene could actually be exactly the same gene. If it exists, it could be a matter of just different alleles of the same gene. It could be as subtle as a few different amino acids in the chain causing the protein to fold slightly differently.

It could be...

Ryan_m_b

Quote by Ken Natton

I am aware that you are not really interested in the answer to that question - that is not really your reason for posting - but for what it is worth, simple logic tells you that if there is a 'gay' gene then there is also a 'straight' gene. Of course the gay gene and the straight gene could actually be exactly the same gene. If it exists, it could be a matter of just different alleles of the same gene. It could be as subtle as a few different amino acids in the chain causing the protein to fold slightly differently.

It could be...

It is extremely unlikely that a complex and varied personality trait is controlled by one gene.

Ken Natton

Quote by Ryan_m_b

It is extremely unlikely that a complex and varied personality trait is controlled by one gene.

<Sigh> Yes Ryan, quite, I am aware of that. That issue has been discussed in detail further up this thread. I have also nmentioned how one gene can be critical in triggering different sequences of gene expression, and thus can appear to be pivotal in quite different traits in the organism. I doubt that lisab was really posing a question, I suspect she was only expressing her low opinion of this thread. But I was merely trying to point out that if something in the geneome does lead to homosexuality in the organism, then clearly there must be a contrasting feature that leads to hetrosexuality. It seems to me that does follow. That does not necessarily suggest any merit in the original premise.

Ryan_m_b

Quote by Ken Natton

<Sigh> Yes Ryan, quite, I am aware of that. That issue has been discussed in detail further up this thread. I have also nmentioned how one gene can be critical in triggering different sequences of gene expression, and thus can appear to be pivotal in quite different traits in the organism. I doubt that lisab was really posing a question, I suspect she was only expressing her low opinion of this thread. But I was merely trying to point out that if something in the geneome does lead to homosexuality in the organism, then clearly there must be a contrasting feature that leads to hetrosexuality. It seems to me that does follow. That does not necessarily suggest any merit in the original premise.

I wasn't questioning that you didn't know that, simply reiterating it. Of more important note though is that it does not necessarily follow that there is a homosexual or heterosexual genotype at all. It could be that those phenotypes are determined by development perhaps with genotypes leading to predispositions.

Something that occurs to me is that we very well could be framing this question wrong by sticking with western concepts of homo/heterosexuality. The validity of such labels is disputed as being to categorical and unrepresentative of the spectrum of human sexual diversity (not to mention the confusion regarding whether or not a behaviour is homosexual and what that says about one's sexuality). I wonder if to tackle sexuality from a biological perspective at all we have to adopt a better way of talking about and viewing sexuality from a social perspective.

lisab

Quote by Ken Natton

I am aware that you are not really interested in the answer to that question - that is not really your reason for posting - but for what it is worth, simple logic tells you that if there is a 'gay' gene then there is also a 'straight' gene. Of course the gay gene and the straight gene could actually be exactly the same gene. If it exists, it could be a matter of just different alleles of the same gene. It could be as subtle as a few different amino acids in the chain causing the protein to fold slightly differently.

It could be...

Actually it wasn't a rhetorical question. It was inspired by a conversation I had many years ago with a bio major. She said people had been looking for a long time for a left-handed gene but couldn't find anything definitive. Then someone thought to look for a right-handed gene and boom, there it was. She said people who don't have the right-handed gene are left-handed about half the time.

(Note: I have no idea if her story was correct, and my background is not in genetics so I don't have the knowledge or resources to research it properly.)

Ryan_m_b

Quote by lisab

Actually it wasn't a rhetorical question. It was inspired by a conversation I had many years ago with a bio major. She said people had been looking for a long time for a left-handed gene but couldn't find anything definitive. Then someone thought to look for a right-handed gene and boom, there it was. She said people who don't have the right-handed gene are left-handed about half the time.

(Note: I have no idea if her story was correct, and my background is not in genetics so I don't have the knowledge or resources to research it properly.)

As far as I'm aware the jury is still out on handedness with publications frequently cropping up detailing slight differences in various genes. Though there is a hypothesis similar to your story postulating that there is a specific allele that determines left-hemisphere dominance but it's not confirmed yet.

Pythagorean

As a left-hander, I'm apparently more likely to be homosexual, dyslexic, schizophrenic, creative and athletic.... and president of the USA!

CCWilson

I suspect that there isn't a gay gene. If there were, it would be quickly eliminated by evolution. But I do believe that we have no choice in the matter of which sex we'd rather do the deed with. As a heterosexual guy, when puberty hit, the desires were focused and extreme and automatic. I think with some people it isn't that clear cut, but presumably for some homosexual men, it's also focused and automatic. The fact is that the plumbing allows any combination, so it's a matter of preference and desire. So if sexual orientation isn't genetically determined, why doesn't everybody turn out heterosexual, which is obviously better for spreading one's genes into future generations?

My opinion is that something is happening in the womb during development of the embryo. Sexual preference is a subtle thing. Men like other men as friends, women like other women as friends, it's just the sexual urges that differ from person to person. It may be that it was very difficult for evolution to devise a strategy that 100% of the time got the psychological urges right. Even the development of sexual organs, which is controlled by hormones, sometimes goes awry, and it must be much more complicated for genetics to control our psychological preference for vagina or otherwise. So my guess is that it's a hormonal thing during gestation. There probably are genetic variations in the control of those hormones, but I'm pretty sure that a gene which specifically causes homosexuality would be weeded out by evolution.

Regardless of the cause, I know that in my case sexual preference isn't something that I ever decided, it just was. For many homosexuals, probably likewise. We desire what we desire, and most of us could never change those tendencies.

2AlphaMales?!

Intrauterine hormone dosing causing homosexuality is almost as evolutionarily counterintuitive as a gay gene, and although there is a medium strength correlation for some hormonal conditions/some genes and homosexuality there has only ever been at most a medium strength correlation demonstrated AFAIK. Hardly deterministic. There is only a 20% concordance for monozygotic twins and homosexuality (Bailey et al 2000). Many such twins would also have shared very similar environments of course - still only 20% however.

If it were frequently the environment which causes homosexuality (seems likely) it would not be politically correct to disseminate that information with certitude however because then various...unpalatable cultural groups would force their members, and society at large, to undergo experimental, possibly damaging and certainly unethical practices in order to try and ensure heterosexuality.

There is also the problem that if environmental factors which lead to an increased likelihood of homosexuality were widely known then most parents would do their bit to try and ensure the heterosexuality of their kids, for whatever reason, thereby validating the politically incorrect view that there's something wrong with homosexuality.

The important thing is that it doesn't matter if people are gay or not, and that view is far from universally accepted, so official pronouncements that homosexuality could be avoided through environmental manipulation would cause problems. The AP(sychological)A's glaring omission/dismissal of all the individual psychotherapeutic reports of successful SOCE (sexual orientation change efforts) from their “definitive” 2009 report is testament to that.

It seeems scientific analysis has to take a back seat about this one for now – it’s one of the areas where psychology (and, indeed, biology) isn't allowed to be a proper science for political reasons. Black books indeed…no need to go so far as to actually burn the books however, ergo the comment.

~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.

CCWilson

Alpha, when you say that you believe it's environment that causes homosexuality, do you mean parenting and childhood experiences, without including intrauterine environmental factors? Possible, but in many of us sexual preference is so powerfully one-sided that I don't think anything could have changed us. In others, sexual preference is less focused, and those folks might be able to go either way; I can see that they might be influenced by outside factors.

It's interesting to think about how genetics could lead us, through specific wiring in the brain, to find one sex or the other sexually stimulating. Are there connections in our brains between the sexual stimulation center and images of our mother or of some kind of representation of generic female or male secondary sexual characteristics? How does genetics do that? Strange to contemplate.

Are there differences in sexual preference among those who are breast fed or had more intensive mothering? How about sexual preference percentages between those raised in a heterosexual two-parent home and those raised by one parent or by two homosexual parents or in an orphanage? I think in general there aren't big differences in outcome, although I don't believe the definitive studies have been done. If it turns out that sexual preference isn't affected by the sexual orientation of the parent(s), that would suggest - but not prove - that social environment outside the womb is not the determining factor.

I don't agree that intrauterine hormones as a cause of homosexuality is counterintuitive. My suggestion was that sexual preference, presumably genetically engineered through brain structure and connections, must be a difficult thing to get right, and easy to screw up. So it's possible that the best that evolution could come up with as a mechanism isn't perfect and only gets it right 90% of the time, using hormones (and who knows what else) as drivers for the brain changes that tell a person, "This is what turns you on."

OmCheeto

Quote by tahayassen

...
Are gay people born the way they are? Or is it something they learn?
...

A topic about sexuality, and sheep haven't been brought into the conversation yet?

BIOLOGY BEHIND HOMOSEXUALITY IN SHEEP, STUDY CONFIRMS

Researchers ... have confirmed that a male sheep's preference for same-sex partners has biological underpinnings.

...researchers discovered an irregularly shaped, densely packed cluster of nerve cells in the hypothalamus of the sheep brain, which they named the ovine sexually dimorphic nucleus or oSDN because it is a different size in rams than in ewes. The hypothalamus is the part of the brain that regulates sex hormone secretion, blood pressure, body temperature, water balance, and food intake, while it also plays a role in regulating complex behaviors, such as sexual behavior.

The oSDN in rams that preferred females was "significantly" larger and contained more neurons than in male-oriented rams and ewes. In addition, the oSDN of the female-oriented rams expressed higher levels of aromatase, a substance that converts testosterone to estradiol so that the androgen hormone can facilitate typical male sexual behaviors. Aromatase expression was no different between male-oriented rams and ewes.

The study was the first to demonstrate an association between natural variations in sexual partner preferences and brain structure in nonhuman animals.

Typical incomprehensible biology babel, but I think it implies that they're born that way.

ps. Lots of interesting articles can be found by googling "gay sheep"

pps. I'm still in the market for lesbian tree climbing milk goats. If anyone see's some for sale, please contact me immediately.

CCWilson

What we don't know is why the hypothalamus was different in straight and gay sheep - was it genetic, or was it something that happened in the womb?

There was a study which showed that the more older brothers a boy has, the higher the likelihood he'll be homosexual. That suggests that maybe the mother's supply of hormones available for the fetus gets depleted or altered somehow. But who knows. http://www.dailymail.co.uk/health/ar...ikely-gay.html

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