10 ms·

Not an expert here but, IF a gay gene existed, wouldn't have it been evolved into extinction?

by ohduran 6y ago

TulliusCicero 6y ago
Not necessarily, as long as it's recessive. Not an expert either here though.
- abcc8 6y ago
  If recessive, you'd expect the wild type and 'gay' alleles to be in Hardy Weinberg Equilibrium. However, this obviously isn't the case.
- thaumasiotes 6y ago
  Yes, it would; being recessive just makes the process take longer. I've pointed out on other HN threads that homosexuality has much lower concordance in identical twins (around 40%) than almost any other trait, making it an especially unlikely candidate for direct genetic causes.
berelig 6y ago
Also not if for most of humanity the mates with this hypothetical gene were repressed into heterosexual relationships.
deleted 6y ago
[deleted]
hello_friendos 6y ago
Important to note that there isn't just Gay and Straight, but more often people exist somewhere in between. That's why we have bisexual and pansexual people.
npwr 6y ago
Not if it is recessive. Example with a recessive "gay gene": Both parent have one normal allele and one "gay" allele. The repartition of the offspring will be: - 25% both normal alleles (normal phenotype) - 50% one normal allele (normal phenotype) - 25% both gay alleles (gay phenotype) But homosexuality is not a gene. I believe that the [fetal androgen exposure theory](https://en.wikipedia.org/wiki/Prenatal_hormones_and_sexual_orientation https://en.wikipedia.org/wiki/Prenatal_hormones_and_sexual_o...) is the one currently preferred.
creata 6y ago
A common analogy here is that in lots of insects, you see whole groups of non-reproductive members, and yet the idea of a "non-reproductive worker insect" hasn't "evolved into extinction." (I'm not commenting on whether being gay has a genetic basis or whether it's an example of kin selection, because honestly, I have no idea.)
- abfan1127 6y ago
  non-reproductive workers benefit the reproductive insects. For instance, worker bees benefit the queen. The queens that lay the eggs in the most beneficial ratios are most likely to survive and pass on. For this analogy to be equivalent, it should lead to having gay children benefit the adults enough to allow for more successful breeding. I do am not commenting on one's gayness has a genetic basis, because I also have not idea.
- lultimouomo 6y ago
  The point is that non-reproductive insects don't have specific set of genes that make them non-reproductive - it is not an inheritable trait. If it was, then it would have evolved into extinction.
  - Brian_K_White 6y ago
    Of course they do (have genes that make them non-reproductive) and of course it hasn't (evolved out of extinction). There is nothing about a possible genetic basis (whether complex and indirect or simple and direct) for an individuals non-reproductiveness that implies it has to result in extiguishing itself. Humans are social enough that genetics which benefit the group at the expense of the individual are perfectly selectable. Heck it even works for utterly antisocial species. All that's required for a trait to persist is for it to be good for any members by any means. It doesn't have to be good for the individual carrier, and it doesn't have to be good in a way that we happen to understand.
    - slavik81 6y ago
      A more formal description: > If a gene copy confers a benefit B on another vehicle at cost C to its own vehicle, its costly action is strategically beneficial if p_B > C, where p is the probability that a copy of the gene is present in the vehicle that benefits. Actions with substantial costs therefore require significant values of p. Two kinds of factors ensure high values of p: relatedness (kinship) and recognition (green beards). The Selfish Gene is probably the most famous way of looking at that concept. https://en.wikipedia.org/wiki/Gene-centered_view_of_evolution https://en.wikipedia.org/wiki/Gene-centered_view_of_evolutio...
KingMachiavelli 6y ago
There is also the 'beneficial sibling' theory where a homosexual sibling improves the reproductive success of their siblings/close family via being able to devote more energy to their siblings offspring instead of their own or are able to gather/utilize more resources that leads to a familial advantage.
lr4444lr 6y ago
Common mutations are inescapable.
hliyan 6y ago
It might persevere through kin selection. For siblings who share the gene, such an individual would have all the benefits of a male/female (security, hunting, care-giving), but none of the mating competition. One could argue if such a gene existed, it would be quite an altruistic one.
NortySpock 6y ago
A lot of the musings I've seen in this direction have been along the lines of (1) some people are bisexual and thus would occasionally reproduce and (2) if sexuality promotes "togetherness" and "group cohesion", then having "our gay uncle who 'has connections' and is always willing to help out the family group" is still beneficial for the family unit and thus a gay gene would not be selected against within that family lineage. Probably not a majority of the population, but there's no reason for such a "gay gene" (if it were to exist) to be driven to zero.
fredley 6y ago
Not neccessarily. Humans are social creatures, our genes' survival is not solely dependent on our individual ability to pass them on, since we share genes with our siblings and parents as well as offspring. For example, families with some non-reproducing offspring may fair better due to having a higher adults/children ratio. If such a gene existed (which perhaps it doesn't), it might benefit families who had members carrying it. This is the same reason some species have evolved alarm-calling when a predator is nearby. It benefits the collective (who share the gene), but at an obvious detriment to the individual's ability to pass on their genes in this case.
- ben_w 6y ago
  In addition, one suggestion is that a possible “gay gene” would be something that causes extremely strong attraction to men in both men and women with that gene. Women with this gene would then be more likely to father children, which could counter the evolutionary pressure resulting from the male offspring with that gene not having any offspring. (I’m massively oversimplfing of course, my bio knowledge is fairly limited).
  - ip26 6y ago
    Uh, I know we’re all about redefining gender roles these days, but I’m not yet ready for women to father children...
- cwkoss 6y ago
  In my EvoBio class a decade ago, my professor told us the theory that homosexuality could be adaptive based on birth order because it would reduce fraternal rivalry: the family would have an additional adult to care for the young without being a reproductive competitor.
  - valarauko 6y ago
    This doesn't make much sense, though. Every additional human is a very expensive investment of time, resources, and effort on the family, and offers no material return on investment for at least a decade in terms of productivity. True, while the gay son might not produce offspring to compete with his brother's kids, it also means he brings no additional mate and offspring to help out the family.
mikepurvis 6y ago
The argument around this is that it's of social benefit rather than individual. Particularly when child/infant mortality is high and women have lots of children, it could be helpful to have a pool of adults supporting the child-rearing of others, especially their immediate siblings.
nabla9 6y ago
Not necessarily. * the same gene can have different phenotypes in different individuals. One phenotype may be net negative but the benefit from the other makes it net positive. * in social animal gene can be carried by relatives. Extreme example is ants and bees, most of them are not fertile but they help to spread their genes by helping those who are.
- Brian_K_White 6y ago
  More than just that, as far as I can see, there is no reason this only applies to social species. If it benefits the pool that x% of members have a trait, even full sterility, then the genetics will result in x% having that trait, as long as the benefit continues to exist. I'm not sure what an example mechanism might be for some mountain cats or spiders or whatever that the species benefits from 4% of their members being sterile, but I see no reason that there couldn't be one, and it doesn't require the unfortunate exhibitors of the trait to preserve and occasionally produce the next exhibitor of the trait.
  - valarauko 6y ago
    Let's assume the benefit is improved female fertility. If it's an autosomal trait, half of the carriers will be male, and lead to the vast majority of them refusing to have offspring. That would require the sisters to have a pretty spectacular bump in the number of offspring to offset their gay brothers. Indeed, since the trait is clearly polygenic, all the sisters do not inherit the trait equally, if at all. The sisters who do inherit it would have to be spectacularly fecund to compensate.
pdpi 6y ago
Not necessarily. If the gene is recessive, it will be passed on. The question then is: what happens when that gene expresses itself? The naive reaction is: individuals with the "gay gene" won't reproduce and it will eventually die out. A more nuanced perspective is that while that individual won't reproduce, their presence in the community helps the clan's survival, so a community with the gene is overall stronger, so the gene will stay around.
agravier 6y ago
Depending on other conditions (environmental and genetic), a particular gene may not be expressed in the same manner (or at all). You can find simple examples in recessive alleles. The phenotype of such genes will only be expressed when both alleles are of a compatible type. Another striking example: Sickle cell disease will only be deadly if both alleles carry the unfortunate mutation. But the unhealthy allele is unlikely to be eliminated by evolutionary pressure because carrying one allele provides significant protection against malaria. The interactions between genes and their environment is usually more complicated that these simple examples, but I hope it illustrates that evolutionary pressure may not suffice to erase some apparently unsustainable alleles from the population.
- btilly 6y ago
  The striking example that you gave is more striking than that. Having one allele actually brings protection from malaria. So the recessive is selected for..as long as not too many people have it. That is why sickle-cell anemia mostly shows up in people whose ancestors came from places with a long history of malaria.
DoofusOfDeath 6y ago
I would think that being "gay" doesn't 100% prevent someone from fathering / mothering children.
- inglor_cz 6y ago
  This. In the past, there was a lot of prominent personalities who were suspected of being gay, but left progeny. Social pressure to have children, especially if there is a title / wealth / prestige to inherit, would certainly play a role.
  - kgwgk 6y ago
    Not only social pressure. It’s a fact that some homosexual people do want to procreate.
xutopia 6y ago
Well yes and no. It might actually give a benefit to other siblings. It could manifest itself only in certain circumstances in the womb or in the environment if something helps the phenotype manifest itself... For example there is a correlation with sibling order and homosexuality. The more boys your mother had before you the more chance you have of being homosexual. We're talking about a non-negligible increase of over 30%: https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male_sexual_orientation https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male...
threeseed 6y ago
What if the "gay gene" is tied to the "sexually attracted to our parents gene" ? And evolving out the former would cause the later to go which is detrimental to the overall health of the species.
whatshisface 6y ago
The trouble with that argument is that it also works with, "If there was a genetic cause for shortsightedness, why is it still around?" "If there was such a thing as a genetic disease, why haven't they evolved out?" "If not having X-ray vision was genetic, wouldn't the absence of X-ray vision have been selected out?" You really can't expect evolution to accomplish its "goals," per se. It is sort of a gentle flow down a lazy river, towards adaptation.
- lultimouomo 6y ago
  "If there was a genetic cause for shortsightedness, why is it still around?" - because myopia doesn't significantly affect your chances to produce offsprings. It seems reasonable that being gay does significantly reduce your ability to have children; therefore it is reasonable to expect that if it was an inheritable trait it would have been selected against.
  - Brian_K_White 6y ago
    Everyone keeps saying that, but it's simply not true. We have understood how this is not true for decades or even hundreds of years, and it's not even some impossible concept to grasp. All that's required for a trait to persist, is for it to benefit the pool, not the individual. The only way the seemingly obvious but incorrect idea you descibed applies is, a trait which is good for the group at the expense of the individual, if it's 100% effective like sterility unlike say alarm-calling which merely carries a risk for the individual, is that such a trait can never grow to where all members exhibit it. But it can absolutely be strongly selected for maintaining whatever the optimal percentage is. IE, if it benefits the pool for 10% of members to be sterile, then the percentage of sterile members will not decrease through the mechanism you and so many imagine, but will stay at 10% for as long as the benefit exists.
    - dctaflin 6y ago
      And everybody keeps saying THAT. The problem is, that's a secondary effect. A secondary effect is going to have to be pretty strong to counter an obviously anti-competitive primary effect. You can construct scenarios, but I haven't seen any that seem particularly compelling. It seems to me that the default position of "it's not genetic" is much better supported by the data.
zvrba 6y ago
Interestingly, I've heard about many people who went from "straight", married with children to leaving their families because they've found out they're gay. I even knew one whose first sexual experiences were with women, and he decided he was gay later. In his "straight phase" he could have had fathered children if he weren't careful. Curiously, I've never heard about opposite cases (spontaneous [1] gay -> straight transition). Make of it what you want. [1] Spontaneous = ignoring attempts to "cure" gay orientation.
praptak 6y ago
The other posts cover possible reasons why being gay may be actually good for the utility function of a gene. There is another hypothesis for why this hypothetical gene might not evolve into extinction. Being gay may just be a side effect of it, with some other benefits being the reason this gene stays in our gene pool.
xirbeosbwo1234 6y ago
If you take a simplistic view of genetics where you draw Punnet squares and check if the offspring has GG alleles, maybe. Even if there are social benefits to there being some gay people around, that would still make those alleles pretty unlikely to be passed on. That doesn't imply there isn't a genetic component. Real genetics is a lot more complicated than that. The fact that something is genetic doesn't imply there is no social component. Genetic factors could lead to a predisposition for a certain behavior that would still be altered by environment. There could be many genes that each has some small effect but none of which is an on/off switch. Those would lead to more complicated selection pressures. We are pretty sure there is a genetic component. We are pretty sure that it isn't just "if you got the gay allele then you's gay". Also, some gay (or mostly gay) people have children. This is because a) most people are at least a little bit bisexual, b) people may want to have children even if the sex act isn't appealing, and c) there are social pressures to conform.
tzs 6y ago
There are several possibilities. 1. If having gay relatives improved the chances that you will have children and they would survive to themselves reproduce, then evolution could favor maintaining a gay gene. Remember that for nearly all of our species' existence, and that of the pre-humans we evolved from, we've lived most of our lives in arrangements where our close relatives lived near us and most people in the region were also related to us. Your children have half your genes. Your siblings' children have a quarter of your genes. So in effect two of your siblings children are equivalent to one of your own as far as getting your genetic material into the next generation goes. If being gay meant that your sibling does not have their own kids to take care of and so they devote effort that would have gone to raising their own kids to helping their straight siblings' with their kids or to doing things that help the village that those with kids don't have the time for, that might greatly increase the survival rate of those kids enough to make up for not having kids of their own. 2. Being gay doesn't mean you can't have kids. Throughout most of our history, many many people have had kids with people they have not been attracted to. That goes for both gay people and straight people. 3. What if it were a bisexual gene rather than a gay gene? Having people in your tribe that can form with both men and women the kind of close bonds the people form for the sexual partners has some obvious advantages.
notabee 6y ago
https://en.wikipedia.org/wiki/Grandmother_hypothesis#The_grandmother_effect https://en.wikipedia.org/wiki/Grandmother_hypothesis#The_gra...
throwaway2245 6y ago
I view this question - and the deliberation over it - as coming from present-day society's latent homophobia. Doesn't the question apply to straight people, and anyone else, who don't reproduce?
wyldfire 6y ago
If homosexuality provided a species or community benefit, it could be selected for in that way. Perhaps akin to aging phenomena that benefit the species through mortality.

Not an expert here but, IF a gay gene existed, wouldn't have it been evolved into extinction?

TulliusCicero 6y ago

Not necessarily, as long as it's recessive. Not an expert either here though.

abcc8 6y ago
If recessive, you'd expect the wild type and 'gay' alleles to be in Hardy Weinberg Equilibrium. However, this obviously isn't the case.
thaumasiotes 6y ago
Yes, it would; being recessive just makes the process take longer. I've pointed out on other HN threads that homosexuality has much lower concordance in identical twins (around 40%) than almost any other trait, making it an especially unlikely candidate for direct genetic causes.

berelig 6y ago

Also not if for most of humanity the mates with this hypothetical gene were repressed into heterosexual relationships.

deleted 6y ago

[deleted]

hello_friendos 6y ago

Important to note that there isn't just Gay and Straight, but more often people exist somewhere in between. That's why we have bisexual and pansexual people.

npwr 6y ago

Not if it is recessive. Example with a recessive "gay gene": Both parent have one normal allele and one "gay" allele. The repartition of the offspring will be: - 25% both normal alleles (normal phenotype) - 50% one normal allele (normal phenotype) - 25% both gay alleles (gay phenotype) But homosexuality is not a gene. I believe that the [fetal androgen exposure theory](https://en.wikipedia.org/wiki/Prenatal_hormones_and_sexual_orientation https://en.wikipedia.org/wiki/Prenatal_hormones_and_sexual_o...) is the one currently preferred.

creata 6y ago

A common analogy here is that in lots of insects, you see whole groups of non-reproductive members, and yet the idea of a "non-reproductive worker insect" hasn't "evolved into extinction." (I'm not commenting on whether being gay has a genetic basis or whether it's an example of kin selection, because honestly, I have no idea.)

abfan1127 6y ago
non-reproductive workers benefit the reproductive insects. For instance, worker bees benefit the queen. The queens that lay the eggs in the most beneficial ratios are most likely to survive and pass on. For this analogy to be equivalent, it should lead to having gay children benefit the adults enough to allow for more successful breeding. I do am not commenting on one's gayness has a genetic basis, because I also have not idea.
lultimouomo 6y ago
The point is that non-reproductive insects don't have specific set of genes that make them non-reproductive - it is not an inheritable trait. If it was, then it would have evolved into extinction.
- Brian_K_White 6y ago
  Of course they do (have genes that make them non-reproductive) and of course it hasn't (evolved out of extinction). There is nothing about a possible genetic basis (whether complex and indirect or simple and direct) for an individuals non-reproductiveness that implies it has to result in extiguishing itself. Humans are social enough that genetics which benefit the group at the expense of the individual are perfectly selectable. Heck it even works for utterly antisocial species. All that's required for a trait to persist is for it to be good for any members by any means. It doesn't have to be good for the individual carrier, and it doesn't have to be good in a way that we happen to understand.
  - slavik81 6y ago
    A more formal description: > If a gene copy confers a benefit B on another vehicle at cost C to its own vehicle, its costly action is strategically beneficial if p_B > C, where p is the probability that a copy of the gene is present in the vehicle that benefits. Actions with substantial costs therefore require significant values of p. Two kinds of factors ensure high values of p: relatedness (kinship) and recognition (green beards). The Selfish Gene is probably the most famous way of looking at that concept. https://en.wikipedia.org/wiki/Gene-centered_view_of_evolution https://en.wikipedia.org/wiki/Gene-centered_view_of_evolutio...

KingMachiavelli 6y ago

There is also the 'beneficial sibling' theory where a homosexual sibling improves the reproductive success of their siblings/close family via being able to devote more energy to their siblings offspring instead of their own or are able to gather/utilize more resources that leads to a familial advantage.

lr4444lr 6y ago

Common mutations are inescapable.

hliyan 6y ago

It might persevere through kin selection. For siblings who share the gene, such an individual would have all the benefits of a male/female (security, hunting, care-giving), but none of the mating competition. One could argue if such a gene existed, it would be quite an altruistic one.

NortySpock 6y ago

A lot of the musings I've seen in this direction have been along the lines of (1) some people are bisexual and thus would occasionally reproduce and (2) if sexuality promotes "togetherness" and "group cohesion", then having "our gay uncle who 'has connections' and is always willing to help out the family group" is still beneficial for the family unit and thus a gay gene would not be selected against within that family lineage. Probably not a majority of the population, but there's no reason for such a "gay gene" (if it were to exist) to be driven to zero.

fredley 6y ago

Not neccessarily. Humans are social creatures, our genes' survival is not solely dependent on our individual ability to pass them on, since we share genes with our siblings and parents as well as offspring. For example, families with some non-reproducing offspring may fair better due to having a higher adults/children ratio. If such a gene existed (which perhaps it doesn't), it might benefit families who had members carrying it. This is the same reason some species have evolved alarm-calling when a predator is nearby. It benefits the collective (who share the gene), but at an obvious detriment to the individual's ability to pass on their genes in this case.

ben_w 6y ago
In addition, one suggestion is that a possible “gay gene” would be something that causes extremely strong attraction to men in both men and women with that gene. Women with this gene would then be more likely to father children, which could counter the evolutionary pressure resulting from the male offspring with that gene not having any offspring. (I’m massively oversimplfing of course, my bio knowledge is fairly limited).
- ip26 6y ago
  Uh, I know we’re all about redefining gender roles these days, but I’m not yet ready for women to father children...
cwkoss 6y ago
In my EvoBio class a decade ago, my professor told us the theory that homosexuality could be adaptive based on birth order because it would reduce fraternal rivalry: the family would have an additional adult to care for the young without being a reproductive competitor.
- valarauko 6y ago
  This doesn't make much sense, though. Every additional human is a very expensive investment of time, resources, and effort on the family, and offers no material return on investment for at least a decade in terms of productivity. True, while the gay son might not produce offspring to compete with his brother's kids, it also means he brings no additional mate and offspring to help out the family.

mikepurvis 6y ago

The argument around this is that it's of social benefit rather than individual. Particularly when child/infant mortality is high and women have lots of children, it could be helpful to have a pool of adults supporting the child-rearing of others, especially their immediate siblings.

nabla9 6y ago

Not necessarily. * the same gene can have different phenotypes in different individuals. One phenotype may be net negative but the benefit from the other makes it net positive. * in social animal gene can be carried by relatives. Extreme example is ants and bees, most of them are not fertile but they help to spread their genes by helping those who are.

Brian_K_White 6y ago
More than just that, as far as I can see, there is no reason this only applies to social species. If it benefits the pool that x% of members have a trait, even full sterility, then the genetics will result in x% having that trait, as long as the benefit continues to exist. I'm not sure what an example mechanism might be for some mountain cats or spiders or whatever that the species benefits from 4% of their members being sterile, but I see no reason that there couldn't be one, and it doesn't require the unfortunate exhibitors of the trait to preserve and occasionally produce the next exhibitor of the trait.
- valarauko 6y ago
  Let's assume the benefit is improved female fertility. If it's an autosomal trait, half of the carriers will be male, and lead to the vast majority of them refusing to have offspring. That would require the sisters to have a pretty spectacular bump in the number of offspring to offset their gay brothers. Indeed, since the trait is clearly polygenic, all the sisters do not inherit the trait equally, if at all. The sisters who do inherit it would have to be spectacularly fecund to compensate.

pdpi 6y ago

Not necessarily. If the gene is recessive, it will be passed on. The question then is: what happens when that gene expresses itself? The naive reaction is: individuals with the "gay gene" won't reproduce and it will eventually die out. A more nuanced perspective is that while that individual won't reproduce, their presence in the community helps the clan's survival, so a community with the gene is overall stronger, so the gene will stay around.

agravier 6y ago

Depending on other conditions (environmental and genetic), a particular gene may not be expressed in the same manner (or at all). You can find simple examples in recessive alleles. The phenotype of such genes will only be expressed when both alleles are of a compatible type. Another striking example: Sickle cell disease will only be deadly if both alleles carry the unfortunate mutation. But the unhealthy allele is unlikely to be eliminated by evolutionary pressure because carrying one allele provides significant protection against malaria. The interactions between genes and their environment is usually more complicated that these simple examples, but I hope it illustrates that evolutionary pressure may not suffice to erase some apparently unsustainable alleles from the population.

btilly 6y ago
The striking example that you gave is more striking than that. Having one allele actually brings protection from malaria. So the recessive is selected for..as long as not too many people have it. That is why sickle-cell anemia mostly shows up in people whose ancestors came from places with a long history of malaria.

DoofusOfDeath 6y ago

I would think that being "gay" doesn't 100% prevent someone from fathering / mothering children.

inglor_cz 6y ago
This. In the past, there was a lot of prominent personalities who were suspected of being gay, but left progeny. Social pressure to have children, especially if there is a title / wealth / prestige to inherit, would certainly play a role.
- kgwgk 6y ago
  Not only social pressure. It’s a fact that some homosexual people do want to procreate.

xutopia 6y ago

Well yes and no. It might actually give a benefit to other siblings. It could manifest itself only in certain circumstances in the womb or in the environment if something helps the phenotype manifest itself... For example there is a correlation with sibling order and homosexuality. The more boys your mother had before you the more chance you have of being homosexual. We're talking about a non-negligible increase of over 30%: https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male_sexual_orientation https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male...

threeseed 6y ago

What if the "gay gene" is tied to the "sexually attracted to our parents gene" ? And evolving out the former would cause the later to go which is detrimental to the overall health of the species.

whatshisface 6y ago

The trouble with that argument is that it also works with, "If there was a genetic cause for shortsightedness, why is it still around?" "If there was such a thing as a genetic disease, why haven't they evolved out?" "If not having X-ray vision was genetic, wouldn't the absence of X-ray vision have been selected out?" You really can't expect evolution to accomplish its "goals," per se. It is sort of a gentle flow down a lazy river, towards adaptation.

lultimouomo 6y ago
"If there was a genetic cause for shortsightedness, why is it still around?" - because myopia doesn't significantly affect your chances to produce offsprings. It seems reasonable that being gay does significantly reduce your ability to have children; therefore it is reasonable to expect that if it was an inheritable trait it would have been selected against.
- Brian_K_White 6y ago
  Everyone keeps saying that, but it's simply not true. We have understood how this is not true for decades or even hundreds of years, and it's not even some impossible concept to grasp. All that's required for a trait to persist, is for it to benefit the pool, not the individual. The only way the seemingly obvious but incorrect idea you descibed applies is, a trait which is good for the group at the expense of the individual, if it's 100% effective like sterility unlike say alarm-calling which merely carries a risk for the individual, is that such a trait can never grow to where all members exhibit it. But it can absolutely be strongly selected for maintaining whatever the optimal percentage is. IE, if it benefits the pool for 10% of members to be sterile, then the percentage of sterile members will not decrease through the mechanism you and so many imagine, but will stay at 10% for as long as the benefit exists.
  - dctaflin 6y ago
    And everybody keeps saying THAT. The problem is, that's a secondary effect. A secondary effect is going to have to be pretty strong to counter an obviously anti-competitive primary effect. You can construct scenarios, but I haven't seen any that seem particularly compelling. It seems to me that the default position of "it's not genetic" is much better supported by the data.

zvrba 6y ago

Interestingly, I've heard about many people who went from "straight", married with children to leaving their families because they've found out they're gay. I even knew one whose first sexual experiences were with women, and he decided he was gay later. In his "straight phase" he could have had fathered children if he weren't careful. Curiously, I've never heard about opposite cases (spontaneous [1] gay -> straight transition). Make of it what you want. [1] Spontaneous = ignoring attempts to "cure" gay orientation.

praptak 6y ago

The other posts cover possible reasons why being gay may be actually good for the utility function of a gene. There is another hypothesis for why this hypothetical gene might not evolve into extinction. Being gay may just be a side effect of it, with some other benefits being the reason this gene stays in our gene pool.

xirbeosbwo1234 6y ago

If you take a simplistic view of genetics where you draw Punnet squares and check if the offspring has GG alleles, maybe. Even if there are social benefits to there being some gay people around, that would still make those alleles pretty unlikely to be passed on. That doesn't imply there isn't a genetic component. Real genetics is a lot more complicated than that. The fact that something is genetic doesn't imply there is no social component. Genetic factors could lead to a predisposition for a certain behavior that would still be altered by environment. There could be many genes that each has some small effect but none of which is an on/off switch. Those would lead to more complicated selection pressures. We are pretty sure there is a genetic component. We are pretty sure that it isn't just "if you got the gay allele then you's gay". Also, some gay (or mostly gay) people have children. This is because a) most people are at least a little bit bisexual, b) people may want to have children even if the sex act isn't appealing, and c) there are social pressures to conform.

tzs 6y ago

There are several possibilities. 1. If having gay relatives improved the chances that you will have children and they would survive to themselves reproduce, then evolution could favor maintaining a gay gene. Remember that for nearly all of our species' existence, and that of the pre-humans we evolved from, we've lived most of our lives in arrangements where our close relatives lived near us and most people in the region were also related to us. Your children have half your genes. Your siblings' children have a quarter of your genes. So in effect two of your siblings children are equivalent to one of your own as far as getting your genetic material into the next generation goes. If being gay meant that your sibling does not have their own kids to take care of and so they devote effort that would have gone to raising their own kids to helping their straight siblings' with their kids or to doing things that help the village that those with kids don't have the time for, that might greatly increase the survival rate of those kids enough to make up for not having kids of their own. 2. Being gay doesn't mean you can't have kids. Throughout most of our history, many many people have had kids with people they have not been attracted to. That goes for both gay people and straight people. 3. What if it were a bisexual gene rather than a gay gene? Having people in your tribe that can form with both men and women the kind of close bonds the people form for the sexual partners has some obvious advantages.

notabee 6y ago

https://en.wikipedia.org/wiki/Grandmother_hypothesis#The_grandmother_effect https://en.wikipedia.org/wiki/Grandmother_hypothesis#The_gra...

throwaway2245 6y ago

I view this question - and the deliberation over it - as coming from present-day society's latent homophobia. Doesn't the question apply to straight people, and anyone else, who don't reproduce?

wyldfire 6y ago

If homosexuality provided a species or community benefit, it could be selected for in that way. Perhaps akin to aging phenomena that benefit the species through mortality.