Why am I gay? -- Nature? Nurture? (Straights welcome, too)

[sactopete]

... the real mamma jamma what?!  IJSE, are you referring to mafranism again?

[Dixon]

from Parenthetical Greg:

 "when Pete used the word "zygotic" I went all weak in the knees"

 Lol, that's so hot

 And I have to say, I was born this way too. In denial for years, sure, but looking back... I had I sticker of a footballer on my bed when I was about 6 or 7 (Johan Cruyff if you must know) and I was just very interested in his legs! (great legs footballers (thats soccer for a lot of you) ). At the time I didn't know what that meant, but looking back it's pretty obvious now.

 Just to speculate on the genes thing a bit: The gay gene(s) could be carried down the maternal line and their effect is to produce conditions in the womb that increase the probability of homosexual offspring. Which would just make finding them that bit harder.

[estefue]

I personally believe that genetics plays a large part but not completely.   There are many instances of identical twins where one is gay and the other straight.  Personally I can account that my mother's cousin was gay, another cousinhas one gay son and one lesbian daughter, another cousin has a gay son and one of my grandmother's cousins was gay.  I can't believe this would be a coincidence .  As for me, my brother and I are a couple of years apart and had pretty much the same upbringing yet when he was roughhousing with his GI Joes  I was building a castle for them...with drapes .  Esteban

[Carissa]

I personally believe that genetics plays a large part but not completely.   There are many instances of identical twins where one is gay and the other straight. 

I was friends with a set of identical twins in college.  One was straight and one was gay (guess which one I had the crush on. Another story for another day though).  Some might say that there goes the nature theory since they were identical twins.  Some might say that there goes the nurture theory since they were identical twins. 

I asked my friend Staci about this since she was a genetics major.  She told me that research she had seen (it was 1997) indicated that the 'gay gene' was on the X chromosome and even though they each got the same genes, not all of the same ones were expressed by in each twin.  So that's how she explained to me about identical twins where one was gay and one was straight.  I don't know if this is still the case with the research but at the time it was and it makes sense to me.

[Dixon]

 An interesting article posted on Yahoo yesterday entitled "Moms' Genetics Might Help Produce Gay Sons";

 http://news.yahoo.com/s/hsn/20060221/hl_hsn/momsgeneticsmighthelpproducegaysons

 Not conclusive, but then I'm not sure it ever can be, at least in the foreseable future, given out rather limited understanding of the way gene expression works atm...

[freshcutgrass]

Sorry...this is a cut and paste.....



Many genetics researchers, and other investigators who are not religious conservatives, examine the data from various studies and have concluded that the conclusion of most religious conservatives is wrong. Studies prove that homosexuality is not caused by poor parenting or child molestation, alone. This is easily verified. Consider two identical newborn twin boys who were separated at birth and raised in different homes without any contact with each other. If homosexuality were caused by something in the environment, then, if twin #1 turned out to be gay, the chances of the other twin becoming a gay adult would only be about 5%. That is because the second twin would have been exposed to a totally different environment during his upbringing. So his chances of being gay would be the same as for any other male -- about 5%. But, studies have reliably shown that if one twin is gay, there is about a 55% chance that the other twin will be gay.


The rejection of a genetic cause of homosexuality by essentially all conservative Christians and some others seem to be based upon a faulty or inadequate knowledge of the detailed workings of genetics. Genes have a property called penetrance, which is a measure of their effectiveness, or power.

Most human sexuality researchers who are not religious conservatives regard homosexual orientation as a trait like left-handedness.

One theory that fits the available observations is that the penetrance of the "gay gene(s)" is approximately 67%. That causes about half of the males with the gene(s) to become gay. "There could be hundreds of millions of straight men walking around with this gay allele but who are straight simply because it didn't penetrate" In the case of the "gay gene(s)" perhaps 10% or more of all males have the allele that causes homosexuality, but in many cases is the allele not "triggered."

Assuming that the penetrance of the "gay gene" or "gay genes" is 67%, then one would expect that if one fraternal twin was gay that the other would also be gay about 22% of the time. This number also agrees with studies of families with fraternal twins.

Nobody knows what triggers the allele. It might be some event happening in the womb, like an abnormal amount or irregular timing of hormones. It might be some event during early childhood -- before school age. Either way, it is outside the control of the individual and his family of origin. What is known is that it takes effect before the child reaches age 5. Child psychologists can interview children at that age and determine with excellent accuracy who will grow up to be gay.

[lightatlast]

Hi, first post here, so please excuse my new-poster nervousness

I've been very interested to read everyone's thoughts on the origins of sexuality; this is an area I'm heavily interested in both personally and professionally (as a dreaded psychology major), and I've done a little theorising based on my main background and interest in evolutionary psychology and gender interaction. I guess the main issue here is not so much the origin of homo-/bi- sexuality, but rather sexuality itself. If we follow evolution, it initially makes the most sense to assume that everyone would be heterosexual - after all, every human being on the planet is the product of generations upon generations of heterosexual mating, and in theory will have inherited biological mechanisms that promote identification of and attraction/desire towards members of the opposite sex. Of course, this isn't the case; but I find the 'gay gene' explanation rather unsatisfying, as well as a little contradictory to what natural selection would suggest - if a gene or genes exist whose sole purpose is to produce homosexuality, they'd have been pretty much wiped out within a few generations due to the at worst, biological impossibilities and at best, biological complexities of same-sex couples producing offspring - and even discounting the innate desire to have children, the fecundity of gay men is far, far, below their heterosexual counterparts and not enough to keep an exclusively 'gay gene' at its relatively significant prevalence level. Of course, discounting this leaves only the similarly deeply unsatisfying 'lifestyle choice' option, which is so inherently ridiculous I don't feel the need to explain why it's garbage.

So, instead of the existence of a 'gay gene', I'd argue that homosexuality arises as an equal counterpart through evolutionary mechanisms that promote heterosexual fitness. Many, many studies have shown repeatedly that homosexuality in men shows strong correlates to femininity, especially traits like sensitivity and empathy, which interestingly are traits that are consistently rated highly desirable by females (other studies have more shakily shown that gay men show increased kindness, altruism and are less prone to engage in violent crime, although these are much less conclusive and established). Female preference for more feminine traits in men cannot be underestimated. Imagine a scenario in which a woman has a choice between two males - both attractive, both heterosexual. However, one is highly masculine and displays many typically male behaviours, like pursuing many sexual opportunites at once and having high levels of aggression, while the other is still masculine, but shows less of these traits plus a few more feminine ones (kindness, loyalty). For the female, it makes the best bet to take the more sensitive male, who's less likely to desert her, and has qualities that make him a better father, increasing the survival chances of her children. Therefore, whatever alleles caused the slightly more feminine behaviour get passed on to the next generation. If this happens on a wide scale, over a few generations the amount of 'feminine behaviour alleles' (FBAs) in the gene pool will start increasing rapidly. Now, FBAs may somehow alter the male brain, pushing it slightly in a female direction - something borne out by studies with neuroimaging that show quite a few similarities between brain regions of gay men and straight women versus straight men and gay women.

If there are numerous FBAs in the gene pool, a male stands a chance of inheriting any number of them from his parents. Using a hypothetical 10-allele scale, we could suggest that getting 2 or 3 FBAs feminises a man's brain slightly, producing a straight offspring with some female traits that will improve his later reproductive success. However, a son who inherits 6 FBAs out of ten could experience a larger feminising influence, whereby areas of the brain affecting sexual orientation are shaped slightly, perhaps producing a bisexual man. 8 FBAs could completely shape the orientation region towards the female side and produce a gay son (but one who still has a solid and comfortable male gender identity), while getting the full ten FBAs could completely feminise the brain, perhaps producing a male who would be transgendered.

Of course, this is all just theory, but I think it would help the research community to stop looking for simple 'gay genes' and start looking a little deeper into sexuality and gender as a spectrum. I've tried to account for bisexuality and transgenderism too, but I know a lot of assumptions are required to make this work (and of course, environment plays a role too, as in discrepancies between MZ twins).

What do you guys think? I know I've only discussed males, but I can do so for females too if anyone is interested. Also a quick apology for a lack of further depth/citations, but this is supposed to be a fun break from my long name-and-date filled dissertation. 

[freshcutgrass]

"I find the 'gay gene' explanation rather unsatisfying, as well as a little contradictory to what natural selection would suggest - if a gene or genes exist whose sole purpose is to produce homosexuality, they'd have been pretty much wiped out within a few generations due to the at worst, biological impossibilities and at best, biological complexities of same-sex couples producing offspring"



This is not a reason to discount the "gay gene" theory at all...as has aleady been explained, studies have show that the hypothetical gay gene(s) have a penetrance value of about 67%.

This means that 33% of all gay genes are in heterosexuals, which will continue to pass them on to their offspring.

[estefue]

Remember that the advantage of the gay gene theoretically passed down by the mother would be other men to protect and nurture the offspring.  Also, since there would be no expectation of offspring from the gay man the woman´s partner would have no reason to get rid of the offspring.  For ex. some male animals will kill offspring that are not genetically related.  Just a thought.  Esteban

[lightatlast]

This is not a reason to discount the "gay gene" theory at all...as has aleady been explained, studies have show that the hypothetical gay gene(s) have a penetrance value of about 67%.

This means that 33% of all gay genes are in heterosexuals, which will continue to pass them on to their offspring.

Firstly, I'll stress that I'm a firm believer in the genetic/biological basis of homosexuality, in case it made it sound like I was doubting genetics full stop. However, I will restate that I believe the basis is much more than anything like a 'gay gene'. In order for any gene to be successful, it has to confer a survival and reproduction benefit - or at least not disadvantage the host. And in the most clinical terms of reproduction, homosexuality is a disadvantage. Why would it be beneficial for heterosexuals to have a gene or genes that solely has the effect of producing homosexuality, regardless of its level of penetrance. Why 'risk' your reproductive stake by carrying a 'gay gene' at all unless that gene gives you a reproductive benefit that outweighs the risk? What advantage do you believe the gay gene confers to the parents who have it, but aren't themselves gay? This is more the area I'm arguing. Do I think genes determine sexuality? Yep. But I don't think there is a gene whose sole purpose is producing gay offspring - sexual and gender orientations are too complicated for that. Heck, bisexuality makes a specific 'gay gene' seem suspect. I haven't read up on that whole aspect, so I may have missed how penetrance explains it. Any insight is good

Of course, we might be splitting hairs here. Your studies on penetrance and my theories on FBA can quite easily complement each other, mine just omits the idea of a specific gay gene in favour of a number of genes that promote heterosexual fitness while also sometimes producing bi-/homosexuality. Same result, just different terminology - which might be all that we're arguing here.

Remember that the advantage of the gay gene theoretically passed down by the mother would be other men to protect and nurture the offspring.  Also, since there would be no expectation of offspring from the gay man the woman´s partner would have no reason to get rid of the offspring.  For ex. some male animals will kill offspring that are not genetically related.  Just a thought.

Why would a son being gay increase the likelihood of a heterosexual man caring for him? For a new male coming into a new family, there are two possible strategies; in both of which, the sexual orientation of their partner's offspring is pretty insignificant, since that has little bearing on the man's own reproductive success. If a male is caring for another man's offspring, he's diverting his own resources into raising a child that has no bearing on his own gene perpetuation (when he could be using them to raise his own kids). Likewise, his partner will be placing her effort/resources into raising the child, when she could use them to raise his. If anything, the stepfather is more likely to withdraw his parenting - hence the greater likelihood of stepparent abuse and neglect of stepchildren than biological children (the well-documented 'Cinderella' syndrome, which has its animal analogue of infanticide (as you mentioned). That's the rather blood-curdling strategy one. Number two is to provide care for the child, reducing the female's required level of parental effort and thus 'freeing her up' to have the stepfather's own children alongside her existing ones. Either way, the child's orientation has little impact the new male's investment. In situation one, the male in putting investment in to no return, so whether his stepchild is gay or straight, he gets no advantage. In situation two, the child's being gay or not also has no issue to him, since he'll be getting his own kids out of the deal. If anything, the number of gay teens who have been abused and disowned by their families suggests that for some people, homosexuality is enough reason to stop investing, not increase its likelihood.

[estefue]

Just to clarify; what I meant is that gay men would be additional caretakers for the mother's children, not that the male would take care of the female's gay children. 

[lightatlast]

Just to clarify; what I meant is that gay men would be additional caretakers for the mother's children, not that the male would take care of the female's gay children. 

Ah, apologies. I take it you're referring to the helpers at the nest theory - when a mother has gay sons who can then look after her later offspring?

[estefue]

Exactly.  Think about gay uncles spoiling nieces and nephews.  And in my case godson

[lightatlast]

Exactly.  Think about gay uncles spoiling nieces and nephews.  And in my case godson

Aw, cute.

Not a huge fan of 'helpers' myself, although it's undoubtedly true that many family members can benefit from a doting gay male relative (and his disposable income!). But do you think that would be enough to keep a gay gene afloat in the evolutionary pool? A gay relative's help can certainly boost the fitness of a few family members, but he could help them even more by having his own children, which would see genes he shares with his family passed on. And isn't homosexuality correlated with birth order (with younger sons more likely to be gay than older ones, depending on the number of brothers)? Helpers would work better if the first son was gay (and could thus help raise his siblings) - and looking at birth order, by the time a younger gay son is born, there would already be a couple of offspring who could provide additional care to relatives themselves - kind of negating the reason for having a gay 'helper' in the first place. I'd also wonder why helpers would necessarily be gay - if some kind of genetic imperative pushed towards producing 'helper' children, why not just have them be genetically asexual? That way, they don't spend time trying to form relationships - freeing up time to spend helping their family - and if they're not having sex, they don't have to worry about health-damaging STIs either. Why would genetics/evolution push towards having a gay son for the purpose of helping when you could have an asexual child?

Overall, I'd imagine that that the relative help is probably a nice bonus but not a significant factor in the genetics of homosexuality - kind of like the wafer you get with an ice cream, great but not particularly crucial to the ice cream itself. And now I've started using dodgy analogies, I'll stop typing. Hope my viewpoint makes some kind of sense.

[sactopete]

In order for any gene to be successful, it has to confer a survival and reproduction benefit - or at least not disadvantage the host.

I’m not a genetics expert, but is this always true?  I know it’s the stock answer.  I know it’s the “logical” or “rational” assumption.  I just wonder if things aren’t quite a bit more complex.  There are vestigial genetics.  Snakes still carry the genes for their legs, etc.  Perhaps the “advantage” originally associated with the gene is no longer in our environment?

homosexuality is a disadvantage. Why would it be beneficial for heterosexuals to have a gene or genes that solely has the effect of producing homosexuality, regardless of its level of penetrance. Why 'risk' your reproductive stake by carrying a 'gay gene' at all unless that gene gives you a reproductive benefit that outweighs the risk?

Humans are an extremely successful species.  But we’re not just talking about humans.  Homosexuality is documented in many other species.  One could easily argue that what is at work in humans may have commonality with similar behavior in say Bonobo chimpanzees perhaps, but how to explain same sex behavior in fish or birds or insects?  Explanations may be perfectly logical once you have all the information, but when we understand so little of the human genome expecting it all to behave in a logical manner may be a limiting assumption.