Thoughts on the "gay gene" (anyone here a geneticist?)

In the news last week was something about identifying a gene "defect" that drives homosexuality.

I'm not a geneticist, although I was pre-med once, which probably gave me enough knowledge to be dangerous, but I'm having trouble reconciling the whole gene thing (let me preface this by saying that I do not consider homosexuality a choice - there seems to be a spectrum with pure homosexuality on one side, bi-sexuality in the middle, and pure heterosexuality at the other).

The problem with homosexuality as a purely biological concept, it would seem to me, is that since homosexual partnering does not serve to perpetuate the species, that eventually it would select itself out of the species. And yet, by most estimates I've seen, approximately 15% to 20% of the population is homosexual (note: I am not sure if those numbers include bisexuals).

Bisexuals may account for some carry-over - if a person engages in homosexual behavior, because they are "wired" that way, but also engages in heterosexual behavior such that they procreate, then they can pass their genetic information on. But is there enough of that to account for 15% to 20% population membership? Or even 10% if you want to take the low end of the spectrum?

My take on it is not that it is a choice, but rather that it is statistical "noise", if you will, where homosexual members of society contribute in many ways to society, although not specifically to perpetuate the species. There is enough perpetuation (if not too much!) by the remaining 80%-85% that the failure of the homosexual segment to contribute to the repopulation doesn't affect the species' ability to thrive, and it doesn't necessarily cause any damage to the species, so it's tolerated (statistically and biologically).

That said, if it's a pure gene, how does homosexuality manage to persist at such (relatively) high levels? Purely by all the recessive genes floating around? If it's a defect/mutation, isn't that a relatively high level of modification for the population? If you take the argument that it is biological, and I do, then I run into this conflict (there are conflicts as well if you take the position that it is by choice, but I'm not going there right now, other than to say that I have few friends that have deliberately chosen to live a life of secrecy and fear of stigma).

i had a crush on a boy.-.

but i've also got several relationships -- all sexual -- with women.

so if i want to procreate -- i can.

where's the defect?

The article posited a defect, I didn't, but if you would class yourself as bisexual and you may potentially procreate, then you wouldn't be part of the group that was exclusively same-sex partnered with no likelihood of perpetuating the species. If you are in opposite-sex relations, then you don't quite affect the situation as someone in exclusive relationships.

Again, I'm not questioning the genetic link, and I'm not suggesting it's a defect, but at the same time it raises a couple of questions that I can't quite noodle out.

gay people like straight people are not easily pegged!

somebody else posted a thread re: this gene.

but i know that myself and other gay men and women have had sexual relations{that's what we're really talking about here} with members of the opposite sex.

that does not make us ANY LESS THAN FULLY GAY -- but like all people we react differntly in different situations when it comes to sex.

i'm not bisexual -- nor are any other of those dear friends -- but these stereo types make me nuts.

end of rant.

I can procreate too.

Heck, I'll even admit I slept with a man. One man, once. And I've been 100% a lesbian since the day I was born -- and the experience didn't sway me for one second. (In fact, I can think of only one gay man and one lesbian in my life who never once had sex with a MOTOS.)

We all experiment (or try to force ourselves into doing what doesn't come naturally, under societal pressure), no matter how hard-wired our sexuality.

And any straight person who swears s/he's never had a sexual thought about a MOTSS, much less a sexual experience, is lying. If I had a nickel for every straight woman who tried to seduce me... And there's a reason such terms as "LUG" and "closet queen" exist.

It's going to be a long time before the world stops seeing sexuality in black and white, and trying to boil it down to a "reason" (read: "defect"), and come to terms with the fact that sexuality is on a continuum. It's a Morbius strip, not a straight line.

But that's just too threatening for a lot of folks, and always will be, I guess.

are there any identical twins of which one is gay and the other straight? If so, being gay is either a 1) developmental variation (something that happened because your brain grew a certain way, which is more related to the nutrition and external condition on you than to your genotype) or 2) it is a choice. I believe in 1). I do not believe in a "gay gene"

in the DNA of homosexuals, just as you can find genes in DNA of those that are diabetic, sickle cell, cancer, etc.

A change in even the smallest portion of DNA can have HUGE repercussions on the animal. If there are genes controlling male vs. female, I would be surprised to find no genes controlling homosexual vs. heterosexual.

That being said, I'm sure that developmental variation also plays a large role in whether or not someone is homosexual. The bottomline however is that homosexuality is NOT a choice that can be unmade or a disease that can be "cured" (like some Christian literature might suggest).

Edited to add that I am, in fact, an identical twin. (I'm serious!)
Also, I am heterosexual, just to clear all that up :D

that does not mean that homosexuals would die out due to natural selection. Heterosexual couples can have homosexual children, meaning the "species" will propogate even if they themselves cannot procreate. Just clarifying :D

of gay people come from heterosexual parents. It really seems to me that, at least, part of it is genetic, if you ask a gay person is there are any other gay people in their families a good portion will say there is.

Maybe I'm wrong, but I suspect most families have someone who seems a bit "that way."

But ask a midwesterner if anyone in their family is gay? Oh no, of COURSE not.

Homosexuality is likely a complex of genetic and social factors, and talk of a "gay gene" only serves to dumb down the actual science of genetics. It almost certainly is not a single gene.

As for those portions that are genetic, some have speculated that homosexuals function as auxiliary caregivers in their families, ensuring that individuals with a high probability of possessing some of the responsible recessive genes can reproduce. Furthermore, a not insignificant number of homosexuals have had heterosexual sex and are themselves parents.

men in the female line. Like hemophilia, which does not affect the carriers of the gene, it appears to be nonetheless less genetic.

While homosexuality doesn't aid in the survival of the individual's genes, there's an argument that it may aid in the survival of the family's or society's genes. A man not burdened with children contributes to the society by looking after other members and contributing resources. I read a really interesting study that said more fertile women tend to have disproportionately more gay sons. A large family with lots of kids could only be benefited by more gay men: they don't have children to further use up resources, and they provide extra food.

Just thinking aloud.

He throws the best holiday party.

For an individual, homosexuality would seem the death knell for his/her genetic lineage. However, that "gay gene sequence" exists in many individuals. It is merely active in some.

The result is that while the few individuals with the active gay gene may not pass on the gene, the species as a whole, which has the gay gene sequence, may have a better chance of survival. It may serve as a check on uncontrolled population growth, as over population is just as bad as underpopulation for a species.

That's my take on it, at least.

sort of like a "governer" on a motor.

Or maybe like a flywheel. Smoothing out population oscilations. At times the population might become excessive, gayness increases, at times population might sag, gayness decreases.

Perhaps the gayness and "decadence" of certain historic times of plenty are signs of a species wide means of population control? Perhaps Rome and Greece would have failed in massive famines without it. Perhaps the Great Depression would have been worsened by an even greater population pulse from the '20s without it. Perhaps some civilization collapses can be linked to a DENIAL of gayness?

Perhaps I'm overgrandizing the idea? :)

one straight and HIV negative, the other gay and HIV positive, for perfect match bone marrow transplants as a cure for AIDS. It did slow the progression a bit before the drug cocktail came out, but the docs soon discovered that HIV also hides in the central nervous system, beyond the blood/brain barrier.

I find it difficult, therefore, to believe in a "gay gene." I find it much more likely that there may be a genetic predisposition that is "switched on" by the hormonal environment during gestation. Since there are two placentas attached in two different places (generally speaking, rare identicals have shared a single placenta), a different hormonal load for each is entirely possible.

What I do know is that every gay man and lesbian I know feel they were born that way, and people have been coming out to me since I was 14. I spotted a cousin when I was 14 and she was 9. I never told anyone about it, just spotted it, so there's no question of self fulfilling prophecy.

Personally, I don't care what the cause is. I find all the wailing and gnashing of teeth over minor and harmless variations in sexuality to be ridiculous. I see no future in harassing people to change what they were born with, as long as they aren't hurting anyone else.

It always astounds me that some people judge of worth of another on "variations in sexuality" (good phrase!)

But even if something is genetically determined, that does not mean that it's heritable. Personally I think that genes are way overrated and that environment plays a likely more important role in many instances. Sure genes set the stage but environmental factors determine a whole lot.

which is the only way to explain it.

Females who are molested growing up, some turn out to only consort with other females, thus taking the lesbian route, others pursue hetero relationships.

Males who have experiences growing up may turn out to only consort with other males, whereas others still take the hetero route.

Are they choices? Or are they nudged along by a genetic predisposition?

I think it's a combination of environmental and genetics.

it just so happened the abuse happened to someone who was probably gay or bisexual.

Oh, honey, you're way off there on the molestation angle. Where in the world did you get that?! Shut that Paul Cameron window before it poisons your brain!

As one with ZERO sexual abuse in my childhood, and a family so boringly normal, wholesome and loving they make the Bradys look like the Bundys, I'm a lot more common than you know. And I'm the queerest lesbian you could ever have the pleasure of meeting.

Where DO you find this stuff? Unreal!

Obviously you know nothing about women who had childhoods full of sexual abuse.

I'm going to cheat and simply copy-and-paste what I posted over there, because it is directly related to this discussion...

The most persuasive (although not totally convincing) evolutionary explanation I have yet heard for homosexuality was in the book Adam's Curse by Bryan Sykes. It's been a while since I read the book, and I don't remember all the details, so I doubt I will do his explanation much justice here. I suggest that everyone read the book to get the full story. Still, I'll give it a try.

Homosexuality is very difficult to explain from an evolutionary standpoint, because of a very basic fact about evolution. If a particular gene decreases the reproductive success of the carrier, that gene will be removed from the gene pool fairly quickly. While it is true that homosexual men do often have sex with women, and it it is true that plenty of homosexual men have children, there should be little doubt that homosexual men as a group are unlikely to reproduce at the same rate as heterosexual men. This is a evolutionary conundrum.

Sykes notes that the gene or genes for male homosexuality seems to be passed along the female line, from mothers to their sons (and from mothers to their daughters, who are carriers of the gene). Studies have shown that gay men are *not* more likely to have gay fathers than heterosexual men, so it's unlikely that the gene came from the father. Studies have also shown that gay men *are* more likely than heterosexual men to have gay uncles on their mother's side of the family. This pattern strongly suggests that the gene comes from the mother.

This suggests two things: 1) The gene may actually exist in our mitochondrial DNA, which is passed exclusively from mother to child, and is not mixed with the father's DNA; and 2) it also suggests that the gene may increase the reproductive success for the women who carry it -- in the form of greater success for their daughters.

Sykes suggests a possible advantage for those daughters. Because gay brothers are less likely to have children of their own when they grow up, those gay brothers have extra time and extra resources to devote to helping their mothers raise their sisters. This additional nurturing that the sisters get from their gay brothers increases their chances of survival, and increases their reproductive success.

And of course, those daughters pass the gay gene on to their own daughters and sons, and the cycle continues.

Sykes provides a biochemical explanation for how this gene might work, but I don't remember any of the details.

Obviously, this is a highly controversial topic, and there is no scientific consensus at this time. But this is the only convincing evolutionary explanation I have yet heard.

And it does cover the conundrum, and sort of covers my original take - if being gay means you don't contribute to the perpetuation of the species then why are those members of the species not selected out? I opined that perhaps gays (to use the term generically) contribute to society in a positive way while not necessarily negatively affecting society, and thus end up as statistical noise - they help, while not hurting, although I hadn't quite figured out, purely genetically, why they still didn't select out.

If the genes pass from the mother on down that might resolve one of the conundrums of the issue. Therefore a mother might pass the genes to multiple offspring.

Although, technically, I guess there's no reason why a father can't pass the same genes along.

seems to have come from my paternal grandfather, a deeply closeted man who didn't marry until the age of 46, a good Catholic, church organist, who had a very special relationship with the Monsignior and thought sex was strictly for procreation.

There are 2 gays and 2 lesbians among his 20+ grandchildren, so I guess it skipped a generation, none of his offspring were gay.

Paleolinguistics studies have shown no word for "father" in reconstructed Indo European, the word was later derived from the word for "owner." What does seem to be the most ancient root is "Mother's Brother," which seems to have been the primary male relationship to the succeeding generation, and they can't all have been gay.

I still think the genetic predisposition/hormonal thing makes the most sense to me. Dr. Sykes's theory is interesting speculation, but I sincerely doubt that removing 10% of the males from the breeding population to baby sit a woman's offspring would have made much of a dent in their survival, especially given that a woman's brothers were likely the meat providers in a system with unrecognized paternity.

I had a gay aunt. My husband had a gay uncle. My sister-in-law has 2 gay kids out of her 4. We had 1 out of our 2 kids.

You do the genetics. Remember those?

I had never heard that point about there not being a word for "father" in reconstructed Indo European. I must say I am skeptical, but considering the fact that it was not possible to prove paternity until very recently, I can kinda see how it might be the case.

Still, I think that Syke's hypotheis has merit, even within the societal constraints that you have suggested. If the mother's brother is the primary meat provider for her children, there could still be an evolutionary advantage to a child with a gay uncle. Consider:

Chimpanzee males are known to barter food with females in exchange for sex. Imagine if all the heterosexual males in your society were giving most of their meat to their sister's children, but they were also setting aside a little bit of meat for their own use so they can "buy" sex from females. Homosexual males don't feel compelled to set aside meat to purchase sex, so their neices and nephews get a little bit more meat than all the other kids in the society. (Meanwhile, their mother may be supplementing the family's meat by selling sex to heterosexual males.) Ultimately, the children with gay uncles are a bit better off. In fact, I kinda think Syke's hypothesis might work better under the conditions you have suggested. Someone needs to do a study to find out if chimps barter food for gay sex, or if they only do it for heterosexual sex.

is that other species (nearly all of them, in fact) have examples of homosexual behavior. Many of those species have no role with the offspring for the male once semen is passed on. It's as true for the homosexual males as well as the ones who actually produced offspring.

Again, men like Sykes are entertaining to read, but trying to deodorize homosexuality (for the right wing?) by pointing out an evolutionary advantage to families with homosexuals is rather a lost cause. The behavior you described, the gay men being left behind to help guard the women and children in war time was quite common among the plains tribes in the US, and possibly in other reasonably evolved social systems, as well, and had little to do with which women they were genetically closest to. There is an advantage to a group in recognizing the contributions of its gay and lesbian members, but that contribution rarely falls along strict genetic lines.

Remember, we were tribal during most of our history, and only developed extended families during the rise of the nation/state. Nuclear families are even more recent, mostly a phenomenon of the 1950s, when the rush to the suburbs occurred. The nuclear family scenario Sykes seems to envision, with a gay uncle providing extra food and babysitting services, would have been preposterous at the dawn of our species, when the "gay gene" should have evolved.

Perhaps I misunderstand what you're saying. My post (which was pure speculation) was based on the assumption that gay men were not staying behind to protect the women. My assumption was that gay men were engaging in the same behaviors as straight men -- specifically, hunting for food and then sharing it with their sister and their sister's children -- the only difference being that gay men were less likely to squander food bartering for sex, and thus had more to share with their nieces and nephews.

The "nuclear family scenario" in this case was based on my reading of your post. You refer to the ancient root "Mother's Brother," and you state that the mother's brother seems to be the primary male relationship to the succeeding generation. That is the exact assumption behind my post, so I'm not sure why you are calling it preposterous now. My assumption was that the uncle was providing childrearing assistance regardless of whether that uncle was gay or straight. I was suggesting a possible reason why the nieces and nephews of gay uncles might get slightly more resources than those with straight uncles.

And to be clear: I've gone way beyond Sykes' speculation here. I was trying to suggest a possible way that his explanation might fit within the parameters which (I thought) you were describing.

providing a role model and perhaps some training for the boys in the skills used by men back then. Even at that, they'd have had help from the experts in the tribe.

Perhaps I'm wearing my own politics on my sleeve here, as evolutionary biologists all seem locked into that "man the hunter and provider, woman the passive breeder" paradigm, something evidenced by your reading of Sykes. (If I had any money, I'd buy his book, read it, and then send him a scorching letter about his cultural myopia)

Truth be told, in all hunter/gatherer social groups being studied today, the women do the gathering and provide something like 90% of the calories for the group. They do it pregnant and they do it lugging infants. Hunting is sporadic, at best, and success even more so. Perhaps it would make more sense to view the gay uncle as remaining with the females doing the gathering, thus increasing the amount of foodstuff, but there again, most of those societies share among the group instead of each nuclear family being out for itself.

There again, homosexual behavior has been observed in species where the male is little more than sperm donor and all males will be driven off if they get anywhere near offspring, something Sykes fails to explain away in his restriction to the only group that would support his theory: primates.

In any case, his speculation is just that, at best. Given the wide variety in species observed as having homosexual members, it seems that the predisposition, if it is a genetic one, is very old, indeed, predating the first hominids, and should be regarded as an entirely normal variation.

You were the person who introduced the "father figure provides meat" paradigm into this, not me and not Sykes. So it seems a little unfair to accuse him of being locked into the culturally myopic paradigm of "man the hunter and provider, woman the passive breeder".

My original post referred only to "extra time" and "extra resources" and "additional nurturing". I did not make any claim regarding what form that additional nurturing may have been, and (if my memory serves) neither did Sykes. My impression is that the hypothesis could work whether the additional nurturing is food, or even "providing a role model and perhaps some training for the boys in the skills used by men back then" as you describe. And even if it was not much nurturing at all, just a tiny bit could make a difference in evolutionary terms.

Furthermore, I don't see why you think Sykes' hypothesis goes against the idea that homosexuality is an old and entirely normal variation.

But whatever. We've moved totally into the area of speculation here, and I'm not sold on Sykes' hypothesis, either. I shared it because the topic of this thread was evolutionary explanations for homosexuality, and Sykes' hypothesis fits the topic. As I said above "Obviously, this is a highly controversial topic, and there is no scientific consensus at this time." My guess is that he will likely be proven wrong. But at this point it is still the only compelling evolutionary explanation I (as a non-expert) have yet come across.

"Paeter", wich became "pita" in Sanskrit, Pater in Latin. and "vater" in German.

As I said, I was pretty skeptical of that. Any idea if the word was derived from the word "owner," as was suggested above?

And...

The best explanation I've heard about the genetics of gay men is somewhat related to these arguments. It has to do with people in the time of cavemen. While the (straight) men would go out and do the hunting, the women would be left behind to take care of the children, etc. Those women needed to be guarded, and the straight men felt comfortable leaving the small % of gay men behind with the women, to protect them.

Also, if there is anyone out there who does not understand recessive vs. dominant genes, <http://en.wikipedia.org/wiki/Recessive_gene>

Which is actually funny considering I happen to be a femme lesbian.

But as I just stated, my mothers brother happens to be gay, and I turned out gay as well. Go figure! :shrug:

Apparently he is working from the assumption that homosexuality has different evolutionary origins in men and women.

Sykes notes that the gene or genes for male homosexuality seems to be passed along the female line, from mothers to their sons (and from mothers to their daughters, who are carriers of the gene). Studies have shown that gay men are *not* more likely to have gay fathers than heterosexual men, so it's unlikely that the gene came from the father. Studies have also shown that gay men *are* more likely than heterosexual men to have gay uncles on their mother's side of the family. This pattern strongly suggests that the gene comes from the mother.

Everyone here knows I am gay. Something not many know is, I also have a gay Uncle. (Yes my mothers brother.)

I also have a friend who has a gay son. That friend has two brothers who happen to be gay as well.

It would be interesting to actually do a proper count of this, just to see what the statistics of this actually are.

Thanks for posting this, Skinner!

That's all well and good, but: Does the theory apply to lesbians as well?

If it does, then too bad there's always an exception to the theory: me. I'm the only known gay person in my family, ever, going back three generations. I've asked my mother, and she couldn't recall even one aunt or cousin who was so much as a little "odd" (well, OK, some were "odd," but not in the sense they might have been gay), let alone a recognizable "Uncle Arthur."

I suppose I must have had gay ancestors at some point, just due to the law of averages.

Interestingly, of my maternal grandmother's ten grandchildren, I seem to be the token ten-percenter.

There's one generation in the family after mine, consisting of 13 cousins (all my second cousins). Five are unquestionably straight, so the odds are fair that one of the remaining eight will turn out to be gay.

I can hope, can't I? ;)

On the other hand, perhaps lesbians get this "gene" from our fathers. My brain's not willing to imagine right now what evolutionary use we would be, comparable to the "gay brother" scenario, but I suppose anything's possible.

I have no anecdotal evidence to support the idea of a recessive lesbian gene passed from father to daughter, as I knew virtually no one on my father's side of the family. For all I know, Mr. Sapphocrat's family could be filled with flaming homos.

I can hope, can't I? ;)

Both are caused by recessive genes so you need both genes to get the disease. On the otherhand having one gene bestows a benefit on a person. One sickle cell gene makes a person nearly immune from malaria while one cystic fibrosis gene helps lung function. Thus the gene gets perpetuated even while killing off some carriers.

there are two or three distinct molecular signalling pathways by which gender is communicated from the genes and chromosomes to and between cells to configure the various tissues.

One of these has a variety of different uses in early fly embryo development, one of which is to set the gender-specific pattern of the neurons and their hookup pattern in the fly equivalent of the spinal cord and ganglia outside it. It also acts in a brain region that could contain sex-specific wiring.

The major interesting thing about this system is that it functions quantitatively- 1x amount of the ligand means male hookup pattern of the peripheral nervous system, 2x means female hookup pattern. Whether this is also at work in the brain area where it seems to act, I don't think anyone knows for certain but it's implausible that it would be otherwise.

Humans and mammals in general have signalling molecules very similar this fly system- a variety of obscure interleukins. Where they show up is the immune system. Flies have extremely rudimentary blood and immune systems, but the signalling system shows up in the development of those as well. I don't think anyone has looked for this family of molecules in the early mouse or human nervous system yet.

You could come up with a model where a woman has a cryptic infection on the fetus or in her uterine wall while a very early male embryo is developing, and spillover of some of these obscure interleukin molecules from agitated lymphocytes at the site of infection during the appropriate time window could drive up the effective signalling level in the embryo from 'male' to confused/intersex or 'female'. I think the variety of evidence- the birth order phenomenon (the later the higher the probability), higher rates of gay men among historically desert peoples in wet climates and peoples with higher rates of uterine diseases, and the link to the female line (i.e. hereditary small uterine defects or immune disorders there)- fits this model pretty well. But it wouldn't much affect female foeti.

that a woman's ammune system may respond to a male fetus in a way that would cause her to produce (and transfer to the child) the chromosome marked XQ28. While the chromosome itself seems to appear in homosexual men, the studies have not concluded how it got there. The current theory- an ammune system reaction by the mother- is still unproven.

These are biological traits, but not genetic traits. Only heritable characteristics could partake in evolution. This is not to say that homosexuality (or heterosexuality or bisexuality or what-have-you) is an "acquired" characteristic. You will always have gays and straights and everything in between and beyond.
My two cents.