It's known that birth order matters. "The more older brothers a male has from the same mother, the greater the probability he will have a homosexual orientation."[1] Interestingly, this occurs only in right-handed males.
See [2]: "Mothers of gay sons, particularly those with older brothers, had significantly higher anti-NLGN4Y levels than did the control samples of women, including mothers of heterosexual sons." There's something going on during pregnancy, and it's starting to be identifiable, but it's not understood yet.
I'd definitely be surprised if a significant portion of homosexuality wasn't environmental, but to my knowledge there is a degree of heritability shown in twin studies. Actually reading the article shows that they found several genes that each contribute, but no single gene. That shouldn't be surprising to anyone, considering that almost every complex trait is somewhat affected by a huge number of genes each tweaking the result by a small amount. Remember that DNA controls the development of the body through an insanely complicated Rube Goldberg machine, no one should expect a 1:1 correspondence between any complicated trait and a gene.
I'm curious if they instead focused on a simple neural net that is fed genes + gay/straight flag if the NN would actually successfully predict it.... in other words, NN's don't care about "finding" that specific gene, they kinda include everything and it "finds" the gene without actually pointing it out.
That's very different from the human approach which is to try to find something specific.
I mean compare it to blood diseases based on genetics. There are many genes that lead to health problems that comes down the shape. But it's not just one thing, it's a spread of things. We're thinking Gay is a specific gene we're just as unlikely to find it.
Not arguing any specific direction, but I just suspect the findings if they don't include variances in their methods.
Here is the speculation part: the more older brothers one has the older they will be from you and entering into sexual experimentation with younger brothers. A quick google shows that this is normal behaviour but the sings are normally similar ages.
I tend to think its probably a mix between nature and nurture.
I suppose it depends on causality - do otherwise "str8" men who experiment with other men "turn" gay, or do "queer" men self select themselves for such experimentation?
Regarding your hypothesis, I'd suggest that perhaps queer kids are more likely to be targeted by older male relatives for sexual abuse.
It's unlikely there's a gene that codes for being gay. Homosexuality instead is better thought of as more like why men have nipples. Obviously the nipples are not useful to the reproductive success of men, but genetics and natural selection are messy and there's likely no easy path to not having them in men while maintaining their function in women.
For homosexuality, the systems of sexual attraction in the brain need to tune to the gender somehow, and this is a system which, apparently, isn't 100% successful at aligning gender and sexual attraction. So the answer to "why are some men attracted to men" is the same as "why do men have nipples:" it's because women need to be attracted to men and because women need nipples.
And of course it needs to be said that just because someone's sexual attraction isn't aligned to their gender it doesn't mean that they're inferior. We don't measure the worth of a person by their reproductive success.
Not sure if nipples are the best analogy here. Formation of nipples is largely down to how fetuses develop; i.e. nipples form before sexual differentiation. And I believe in some mammals, males in fact do not have visible nipples.
I found the conclusion to be misleading, based on this “ The researchers split their study participants into two groups — those who reported having had sex with someone of the same sex, and those who didn’t. ”
So apparently you are gay if you have had sex one time with someone of same sex sometime, anytime in your life. Bisexual, bicurious, some one straight who experimented, etc would all then be “gay”, which are all more prevalent than being strictly gay.
That’s like looking for genes that predict left handedness by selecting people who at some point in their lives have written with their left hand. No wonder they got confusing / weak signals. They should have limited to including only people who actually identified as being gay.
I recently read about the spectrum of homosexuality. Its not a black and white issue. I don't recall the Kinsey scale being the article I read, but it seems relevant. If this is the case, it seems less likely its a single gene. Perhaps its multiple gene expressions accompanied with environmental factors?
People latched onto the idea that sexuality is genetically determined because it seemed like the only viable way to defend themselves against rampant religious bigotry and oppression. It was a rope dangling into the well you were trapped in, and the well was filling with acid, but if you could just manage to climb that rope then you'd make it out. The reasoning went something like "if I can prove that sexuality is genetically predetermined then it means that I didn't choose to be this way". As if genetic predestination were the only possible reason to grant protection to a class. Some people fairly quickly saw the problem with this defense and expanded it to include other uncontrollable elements of childhood development, again leaning on the "if I didn't have a choice _then_ it has to be ok". As if choices were still somehow the problem.
But that's always been a fucked up idea. It shouldn't matter whether it was predetermined or otherwise not in your control. If it's constructed then it's constructed. If it's not then it's not. People shouldn't be oppressed for their sexuality full stop, regardless of reason.
I think the idea of genetic predestination might have been a short-term useful crutch in the past but I hope that we've begun to progress beyond needing people to explain themselves.
And here lies the problems of finding causation not correlation:
- gay is not binary neither through time (people do evolve both way while getting old) neither through ‘space’ (some people are half/half, some people have some preference for love and others for sex, and so on)
- genes are not expressed linearly, and one slight expression in the womb can mean something big, or nothing or maybe something?
- social pressure about sexuality start early even though we may get better at avoiding some: blue for boys, pink for girls, boys do sports, blablabla and so on
- internal development and expression of sexuality does not happen at the same pace and at the same amplitude for everybody (some people really are asexual their whole life) and of course the familly, sister/brotherhood, socio-economical environment influence it too
So in these studies of sexuality and even worse, with the metastudies, I’m always left with the feeling that the hypothesis tested by it was broken from the start. What was the question they were trying to answer?
« Is it biologically complicated? » Ok yes.
« Do we have the tool to even make the distinction between a weak correlation due to the sample bias? » Can’t see how in this study.
What am I missing?
> - internal development and expression of sexuality does not happen at the same pace and at the same amplitude for everybody (some people really are asexual their whole life) and of course the familly, sister/brotherhood, socio-economical environment influence it too
Some people IS asexual. Asexuality it's a valid sexual orientation like being bi/pan/homo or heterosexual. It isn't lack of sexual development or sexual expression or result of family, socio-economical environment influences.
Kind of hopeful we can stop using genetics as a way of justifying queer peoples' existence. Whether it's conditioning, a choice, or genetics, shouldn't really be a factor in how you treat queer people.
That would be ideal, but some people need to be convinced that it is not a choice before they will consider treating gay people with respect. So long as they think it's just a behavioral decision, they can rationalize their bigotry.
If you want people to be treated equally, wouldn't you want their existence to be justified?
It's difficult to think of a PC analogy here, so maybe... super villain mind control device strapped to someone's head. Provably unjustified behaviors due to the mind control device implies the ethical thing to do is try to remove the device. Treating someone normally implies an implicit belief that they're normal. Sound biological evidence that being queer is just how some people are feels like the best way to reinforce that belief and remove requirements for heteronormativity.
One of the sad things about the state of sex ed is that this isn't taught in school. The interplay between genetics (homosexuality is at least somewhat heritable) and environmental factors (each older brother a boy has from the same mother increases the chance he will be gay by about 40%).
Also, this study and many others uses the term "men who have sex with men" not gay. These are two overlapping but different groups.
Plus you need yo look at evidence that sexuality is a modern construct. The Kinsey scale and attitudes to sex in other societies (where men who have sex with men are sometimes considered a third gender or where its more a matter of taste/fancy than a rigid part of identity) would help people understand actual sexuality more effectively.
What you end up with is some genetics, some epigenetics and some environmental factors creating preferences of various strengths. Those are then buried under a layer of socially acceptable behaviour. Which in turn is filtered through identifies ("I'm not gay, I just do it with my mate").
Genes aren’t a good way to explain most things. They’re more like LEGO blocks. It’s how the cells use and express the genes that matters.
So you want to look at regulatory regions of the genome, promoters, and even how and when the dna folds up to inactive large regions. That’s where all the action is.
There are two meanings to "gene" here. What you describe as lego blocks are segments which code for a protein, which is one meaning.
The other is just any code which affects the phenotype, including promotors etc. The SNPs mentioned in TFA are just known fairly common single-point differences, but aren't necessarily in coding DNA. Of course these are still heritable, just like coding changes.
This may be a stupid question, but I'll ask it anyway: How did gay people live in pre-historic times?
Arguably, in our current culture, it is pretty obvious that gay people will produce less offspring than heterosexuals. However, looking on an evolutionary timescale, this culture is rather young. In tribal times, most males did not reproduce - lessening the impact of homosexuality. Maybe the higher female-to-male-gene reproduction rate is factor?
This is just rough speculation, my knowledge is really limited. But it seems plausible at first glance.
I think it's a mistake to see homosexuality as a binary on/off switch; in many cases it's a gradient.
I'm generally heterosexual, but I've also had sex with a man. It's was okay, I guess, but I'd prefer women. On a scale of 0-100 my "gayness score" is probably about 10-20. A hard strong 0 or 100 is probably a lot less common than it's often portrayed: it's more of a bell curve.
One explanation I've read is that gay men are more likely to be left alone with women as they're perceived to be less threatening; giving the gay man a chance to propagate his genes through infidelity (infidelity is fairly common throughout human history). The ever-eqloquent Richard Dawkins once called this "the sneaky fucker strategy".
Something similar could also apply to women.
It's hard to be sure of these kind of things, since it's, well, pre-history, but there are some models which can explain the propagation of homosexual genes and/or behaviour.
I wonder if anyway has attempted a more qualitative study on this. Asking exactly what attributes attract and what the person is thinking when they look at images of men and women.
Do gay men think the same as women? Is it a spectrum?
For straight men it seems mostly tied to women’s ability to carry children, coupled with a genderless beauty evaluation (e.g. symmetry) and then some measure of femininity (which is kind of like anti-masculine maybe). Femininity is really hard to quantify but it’s definitely a “know it when you see it” kind of thing.
An interesting finding is the fraternal birth order effect. The more older brothers you have, the more likely you are to be homosexual (for men). Seems to indicate in-utero mechanisms are involved.
If this question is strictly about the study in OP and not a broader philosophical question, then it's worth pointing out that the study doesn't actually use the word gay but instead:
> In this study, we use the term “same-sex sexual behavior,” which is defined as having ever had sex with someone of the same sex.
I assume it’s a physical attraction to members of the same sex, with the emotional dimension developing in the same way as it does between any two individuals in a mated pair.
In the simplest terms, it’s seeing a beautiful naked body of the opposite sex and getting zero sexual pleasure out of it. That’s it. Being gay doesn’t stop you from forming close bonds with the opposite sex just like being straight doesn’t stop you from having best friends of the same sex.
Is there any trait that is strongly linked to a single gene?
Whenever I hear a news article that there is no X gene, I am completely unsurprised. The idea that a single gene would uniquely determine a particular trait, as if it were a variable in a program like "bool has_blue_eyes", seems oversimplified and unrealistic.
> Is there any trait that is strongly linked to a single gene?
Sure.
Sickle-cell anaemia is one classic case, one (recessive) gene.
Huntington's disease is another, it's about a specific repeat number.
But, as you say, most complex traits (such as height) aren't like that, and involve hundreds or thousands of different genes. IIRC eye color is actually fairly simple, not one gene but much of the control in just a handful? Maybe hair color too? (But not super-sure.)
Yes. MC1R which people with red hair carry. It's a very strongly associated gene. Also "People with freckles and no red hair have an 85% chance of carrying the MC1R gene that is connected to red hair. People with no freckles and no red hair have an 18% chance of carrying the MC1R gene linked to red hair."
i dont get it. whats the problem with accepting that homosexuality might have traits other than where people want to put their genitalia. perhaps its about sending information down via genes and culture? seems homosexuals are amazingly beautiful at generating art and cracking nazi spy codes. maybe their families have other genes and we are just focusing on the whole where people put their genitalia thing vs the "wow maybe gays have a lot to contribute with, you know, just as women or men who are sterile." still find it hilarious that people have been obsessing about this since i was born and longer. accepting homosexuality took me like 1 minute. 45 seconds of laughing at two genitals of the same kind not fitting, and 15 thinking about i love my friend and i want her to be happy because she deserves to feel loved the way she needs too.
[+] [-] Animats|5 years ago|reply
See [2]: "Mothers of gay sons, particularly those with older brothers, had significantly higher anti-NLGN4Y levels than did the control samples of women, including mothers of heterosexual sons." There's something going on during pregnancy, and it's starting to be identifiable, but it's not understood yet.
[1] https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male...
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5777026/
[+] [-] ravi-delia|5 years ago|reply
[+] [-] coding123|5 years ago|reply
That's very different from the human approach which is to try to find something specific.
I mean compare it to blood diseases based on genetics. There are many genes that lead to health problems that comes down the shape. But it's not just one thing, it's a spread of things. We're thinking Gay is a specific gene we're just as unlikely to find it.
Not arguing any specific direction, but I just suspect the findings if they don't include variances in their methods.
[+] [-] godmode2019|5 years ago|reply
Sexual Assault Risks among Gay and Bisexual Men - NCBI - NIH
"One half of men (50.8%) reported childhood sexual assault"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4117833
Similar: https://i.stuff.co.nz/national/3949087/Abused-more-likely-to...
Here is the speculation part: the more older brothers one has the older they will be from you and entering into sexual experimentation with younger brothers. A quick google shows that this is normal behaviour but the sings are normally similar ages.
I tend to think its probably a mix between nature and nurture.
[+] [-] mmmrtl|5 years ago|reply
[+] [-] valarauko|5 years ago|reply
Regarding your hypothesis, I'd suggest that perhaps queer kids are more likely to be targeted by older male relatives for sexual abuse.
[+] [-] readams|5 years ago|reply
For homosexuality, the systems of sexual attraction in the brain need to tune to the gender somehow, and this is a system which, apparently, isn't 100% successful at aligning gender and sexual attraction. So the answer to "why are some men attracted to men" is the same as "why do men have nipples:" it's because women need to be attracted to men and because women need nipples.
And of course it needs to be said that just because someone's sexual attraction isn't aligned to their gender it doesn't mean that they're inferior. We don't measure the worth of a person by their reproductive success.
[+] [-] BurningFrog|5 years ago|reply
We don't measure human worth that way, but evolution measures nothing else!
[+] [-] masklinn|5 years ago|reply
[+] [-] naebother|5 years ago|reply
https://www.livescience.com/32467-why-do-men-have-nipples.ht...
[+] [-] mrfusion|5 years ago|reply
https://en.m.wikipedia.org/wiki/Antagonistic_pleiotropy_hypo...
[+] [-] dnissley|5 years ago|reply
[+] [-] unknown|5 years ago|reply
[deleted]
[+] [-] sjg007|5 years ago|reply
[+] [-] threatofrain|5 years ago|reply
[+] [-] xivzgrev|5 years ago|reply
So apparently you are gay if you have had sex one time with someone of same sex sometime, anytime in your life. Bisexual, bicurious, some one straight who experimented, etc would all then be “gay”, which are all more prevalent than being strictly gay.
That’s like looking for genes that predict left handedness by selecting people who at some point in their lives have written with their left hand. No wonder they got confusing / weak signals. They should have limited to including only people who actually identified as being gay.
[+] [-] abfan1127|5 years ago|reply
https://en.wikipedia.org/wiki/Kinsey_scale
[+] [-] ohduran|5 years ago|reply
[+] [-] BugsJustFindMe|5 years ago|reply
But that's always been a fucked up idea. It shouldn't matter whether it was predetermined or otherwise not in your control. If it's constructed then it's constructed. If it's not then it's not. People shouldn't be oppressed for their sexuality full stop, regardless of reason.
I think the idea of genetic predestination might have been a short-term useful crutch in the past but I hope that we've begun to progress beyond needing people to explain themselves.
[+] [-] notmars|5 years ago|reply
- gay is not binary neither through time (people do evolve both way while getting old) neither through ‘space’ (some people are half/half, some people have some preference for love and others for sex, and so on)
- genes are not expressed linearly, and one slight expression in the womb can mean something big, or nothing or maybe something?
- social pressure about sexuality start early even though we may get better at avoiding some: blue for boys, pink for girls, boys do sports, blablabla and so on
- internal development and expression of sexuality does not happen at the same pace and at the same amplitude for everybody (some people really are asexual their whole life) and of course the familly, sister/brotherhood, socio-economical environment influence it too
So in these studies of sexuality and even worse, with the metastudies, I’m always left with the feeling that the hypothesis tested by it was broken from the start. What was the question they were trying to answer? « Is it biologically complicated? » Ok yes. « Do we have the tool to even make the distinction between a weak correlation due to the sample bias? » Can’t see how in this study. What am I missing?
[+] [-] Zardoz84|5 years ago|reply
Some people IS asexual. Asexuality it's a valid sexual orientation like being bi/pan/homo or heterosexual. It isn't lack of sexual development or sexual expression or result of family, socio-economical environment influences.
Perhaps, you should inform about it better : https://www.asexuality.org/?q=overview.html
[+] [-] bonoetmalo|5 years ago|reply
[+] [-] rootusrootus|5 years ago|reply
[+] [-] klmadfejno|5 years ago|reply
It's difficult to think of a PC analogy here, so maybe... super villain mind control device strapped to someone's head. Provably unjustified behaviors due to the mind control device implies the ethical thing to do is try to remove the device. Treating someone normally implies an implicit belief that they're normal. Sound biological evidence that being queer is just how some people are feels like the best way to reinforce that belief and remove requirements for heteronormativity.
[+] [-] hisabness|5 years ago|reply
[+] [-] drocer88|5 years ago|reply
Result: "five autosomal loci were significantly associated with same-sex sexual behavior".
[+] [-] LatteLazy|5 years ago|reply
Also, this study and many others uses the term "men who have sex with men" not gay. These are two overlapping but different groups.
Plus you need yo look at evidence that sexuality is a modern construct. The Kinsey scale and attitudes to sex in other societies (where men who have sex with men are sometimes considered a third gender or where its more a matter of taste/fancy than a rigid part of identity) would help people understand actual sexuality more effectively.
What you end up with is some genetics, some epigenetics and some environmental factors creating preferences of various strengths. Those are then buried under a layer of socially acceptable behaviour. Which in turn is filtered through identifies ("I'm not gay, I just do it with my mate").
The point being humans are messy.
[+] [-] mrfusion|5 years ago|reply
So you want to look at regulatory regions of the genome, promoters, and even how and when the dna folds up to inactive large regions. That’s where all the action is.
[+] [-] iguy|5 years ago|reply
The other is just any code which affects the phenotype, including promotors etc. The SNPs mentioned in TFA are just known fairly common single-point differences, but aren't necessarily in coding DNA. Of course these are still heritable, just like coding changes.
[+] [-] Sebb767|5 years ago|reply
Arguably, in our current culture, it is pretty obvious that gay people will produce less offspring than heterosexuals. However, looking on an evolutionary timescale, this culture is rather young. In tribal times, most males did not reproduce - lessening the impact of homosexuality. Maybe the higher female-to-male-gene reproduction rate is factor?
This is just rough speculation, my knowledge is really limited. But it seems plausible at first glance.
[+] [-] arp242|5 years ago|reply
I'm generally heterosexual, but I've also had sex with a man. It's was okay, I guess, but I'd prefer women. On a scale of 0-100 my "gayness score" is probably about 10-20. A hard strong 0 or 100 is probably a lot less common than it's often portrayed: it's more of a bell curve.
One explanation I've read is that gay men are more likely to be left alone with women as they're perceived to be less threatening; giving the gay man a chance to propagate his genes through infidelity (infidelity is fairly common throughout human history). The ever-eqloquent Richard Dawkins once called this "the sneaky fucker strategy".
Something similar could also apply to women.
It's hard to be sure of these kind of things, since it's, well, pre-history, but there are some models which can explain the propagation of homosexual genes and/or behaviour.
[+] [-] neaanopri|5 years ago|reply
Recently the identity option has been emphasized. Part of those is because it offers more legitimacy: if I can convince you that:
1. Gay people exist 2. I am gay
Then, my homosexual behavior is more legitimate. Without the identity, Western legal codes were able to ban homosexual behavior.
[+] [-] robin21|5 years ago|reply
Do gay men think the same as women? Is it a spectrum?
For straight men it seems mostly tied to women’s ability to carry children, coupled with a genderless beauty evaluation (e.g. symmetry) and then some measure of femininity (which is kind of like anti-masculine maybe). Femininity is really hard to quantify but it’s definitely a “know it when you see it” kind of thing.
[+] [-] peteretep|5 years ago|reply
I think this is far from clear
[+] [-] unknown|5 years ago|reply
[deleted]
[+] [-] francisofascii|5 years ago|reply
https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male...
[+] [-] antattack|5 years ago|reply
[+] [-] kstrauser|5 years ago|reply
I imagine being gay would be a lot like that, except it would've been a boy.
[+] [-] michae4|5 years ago|reply
[+] [-] marc_abonce|5 years ago|reply
> In this study, we use the term “same-sex sexual behavior,” which is defined as having ever had sex with someone of the same sex.
https://science.sciencemag.org/content/365/6456/eaat7693
[+] [-] swarnie_|5 years ago|reply
Honestly i have no idea but this might be one of the last places left on the internet you can ask a question like this without getting dogpiled.
I've batted for both teams in my life and i still can't tell you.
[+] [-] TulliusCicero|5 years ago|reply
> Is it dislike, fear(?) of opposite sex?
Not generally, no, just like most straight people don't dislike members of their own sex.
[+] [-] stemlord|5 years ago|reply
[+] [-] implements|5 years ago|reply
[+] [-] aardvarkr|5 years ago|reply
[+] [-] haberman|5 years ago|reply
Whenever I hear a news article that there is no X gene, I am completely unsurprised. The idea that a single gene would uniquely determine a particular trait, as if it were a variable in a program like "bool has_blue_eyes", seems oversimplified and unrealistic.
[+] [-] iguy|5 years ago|reply
Sure.
Sickle-cell anaemia is one classic case, one (recessive) gene.
Huntington's disease is another, it's about a specific repeat number.
But, as you say, most complex traits (such as height) aren't like that, and involve hundreds or thousands of different genes. IIRC eye color is actually fairly simple, not one gene but much of the control in just a handful? Maybe hair color too? (But not super-sure.)
[+] [-] Simulacra|5 years ago|reply
https://en.wikipedia.org/wiki/Melanocortin_1_receptor
[+] [-] nradov|5 years ago|reply
https://en.wikipedia.org/wiki/ABO_%28gene%29
[+] [-] nomoreusernames|5 years ago|reply