What are the evolutionary benefits of asexuality?

[okmxm]

I've always been a big supporter of the theory of evolution, but recently coming to terms with my sexuality has made me wonder what the evolutionary benefits of asexuality might be? I feel like this would give me a bit more validation if I could see a logical reason for people who are asexual to exist. I guess the same can be said for people who are homosexual, so this could be answered in regards to that too :) I'm just curious what people think!

[Sally]

There's no logical reason to expect any evolutionary benefits. We simply are who we are; we don't need reasons.

[Larkaloke]

Well, there are certainly potential benefits to having unattached, childless adults around in a large group setting. They can contribute to protecting the group without adding to the number of young creatures that need protecting, for one thing. I believe it's also been shown that sometimes homosexual pairs of animals will protect abandoned/orphaned young, which would be a plus. Certainly that sort of thing happens with humans. If indeed the percentage of the human population which is homosexual or asexual has been going up (I suspect it's more the case that people feel more free to actually make it known that they aren't heterosexual), it could also serve as a natural form of population control.

All that said, there are also naturally occurring traits and mutations that appear to have no real benefit, but also have no real evolutionary disadvantage. This could certainly be such a case. Assuming that both are genetic (which I think is decently likely), it would presumably be a recessive trait that is carried by all members of a certain generation, and since it causes no harm there's no reason that it wouldn't continue.

[thekittyhawk]

It seems that LGBT+ are becoming much more common anyway, since the mid 20th century at least. It is possible that we are evolving to have a natural population control, with gay and asexual people unable to reproduce... I don't want to go and say we're more evolved than others but it explains why it's all becoming more common. We'll overpopulate this entire planet before long.

[Sally]

It seems that LGBT+ are becoming much more common anyway, since the mid 20th century at least. It is possible that we are evolving to have a natural population control, with gay and asexual people unable to reproduce... I don't want to go and say we're more evolved than others but it explains why it's all becoming more common. We'll overpopulate this entire planet before long.

Gay men and lesbians can and do have children, and more of them are doing so. Orientation doesn't have anything to do with the physical ability to reproduce.

[The_Halfmoon]

I'm sorry, are you asking HOW is it possible for asexuality to exist? Or are you asking WHY does asexuality exist in the context of evolution?

Because if it's the latter, I think you may be suggesting a non-Darwinian concept of evolution which proposes that mutations are not accidental. Asexuality, homosexuality, blonde hair, hairy chests for men, and every other trait is purely accidental. They don't have to be useful to be passed down. But, for example, if you have a genetic disposition to not be afraid of lions... well that may be passed down. But over the long run, those people who are not afraid of lions are going to get eaten to the point where few will get a chance to have kids.

And some traits are neither beneficial nor detremental. So for example blue eyes have no value in any way. They just appeared in people and those people with blue eyes were still attractive (and some would say MORE attractive) than brown eyes, so they had as many children and blue eyes became a common trait in certain places.

Asexuality is detremental, in an evolutionary sense (as is homosexuality). Except that tribal and societal influences forced asexuals to mate whether they wanted to or not. So they had kids that passed the trait on.

In the end, the only thing that matters for evolutionary reasons is that you are able to have children and those children grow to adulthood.

[Nidwin]

Diversity and because of this it makes sense to have us ace as opposed to hyper, very sexual human beings.

Being ace doesn't mean we can't find a partner and have a happy life and toddlers around. We just don't have that pull or obsession of getting laid because of our lack of sexual and or romantic atttraction.

[monkey101]

I'm sorry, are you asking HOW is it possible for asexuality to exist? Or are you asking WHY does asexuality exist in the context of evolution?

Because if it's the latter, I think you may be suggesting a non-Darwinian concept of evolution which proposes that mutations are not accidental. Asexuality, homosexuality, blonde hair, hairy chests for men, and every other trait is purely accidental. They don't have to be useful to be passed down. But, for example, if you have a genetic disposition to not be afraid of lions... well that may be passed down. But over the long run, those people who are not afraid of lions are going to get eaten to the point where few will get a chance to have kids.

And some traits are neither beneficial nor detremental. So for example blue eyes have no value in any way. They just appeared in people and those people with blue eyes were still attractive (and some would say MORE attractive) than brown eyes, so they had as many children and blue eyes became a common trait in certain places.

Asexuality is detremental, in an evolutionary sense (as is homosexuality). Except that tribal and societal influences forced asexuals to mate whether they wanted to or not. So they had kids that passed the trait on.

In the end, the only thing that matters for evolutionary reasons is that you are able to have children and those children grow to adulthood.

blond hair and blue eyes i a genetic adaptation for extreme cold weather found in northern europe

[Telecaster68]

How on earth does having blue eyes help in cold weather?

[monkey101]

less chances of catching STDs ( stis )

[The_Halfmoon]

no, blonde hair and blue eyes are purely sexually selected traits. As are chins.

Even pale skin is under question as an adaptation to cold weather, as it was thought to be due to vitamin D deficiencies in the womb but not any longer.

Last I heard about blonde hair evolution was last year when it was thought to have been a mutation occuring in Lithuania roughly 2000 years ago, and spread purely as a sexual trait that had no value to cold weather. Just a coincicence that it occurs in cold regions.

[Lost247365]

I've always been a big supporter of the theory of evolution, but recently coming to terms with my sexuality has made me wonder what the evolutionary benefits of asexuality might be? I feel like this would give me a bit more validation if I could see a logical reason for people who are asexual to exist. I guess the same can be said for people who are homosexual, so this could be answered in regards to that too :) I'm just curious what people think!

Traits don't necessarily have to have benefits.

For example, some traits, are located on the same loci on a chromosome as an advantageous trait and get to piggyback on their success.

It is also possible that a trait could be the effect of random variation or errors that one finds in all thermodynamic systems. The second law of thermodynamics also applies to biological systems after all. Maybe there is a 1 in a hundred chance that the gland that releases the correct hormones malfunctions at a certain time resulting in asexuality during fetal development.

It is also possible that the benefit could be indirect or the result of hybrid genotypes. Sickle cell anemia, for example, is a horrible and deadly genetic disease found in those who are homogeneous for the trait. However, those who are heterogeneous for the trait are more resilient to malaria giving the gene an advantage to overcome the disadvantage.

That said, I personally think that non-reproductive sexualities have an advantage in that they can act as adoptive parent(s) to parentless relatives. I believe that this is one of the advantages some evolutionary scientists currently think can be assign to homosexuality. I don't see why it can't apply to asexuals.

[Dodoa]

There is also the phenomenon of the heterozygotous advantage (I don't know the correct english terms in genetics, sorry) which is most popularly described in scottish sheep. It occurs when a "good" trait is genetically cupled with a "bad trait" and both of those traits are passed on via the Dominant/recessive scheme. Now in the case of the scottish sheep the dominant gene for thick fur is coupled (i.e. passed on together) with the recessive gene for small horns and therefore the recessive gene for thin fur is coupled with the dominant gene for big horns. A sheep with thin fur won't survive the winter and a sheep with small horns won't get a partner. You see both of the "good" genotypes are dominant, so you only need them on one allele for them to be expressed in the phenotype (i.e. visible). If you think it through you realise that the best genotype to have would be: tick fur and small hornes on one chromosome and thin fur and big horns on the other. That way you get a phenotype of thick fur and big horns, but you will still pass on thin fur and small horns to some of your children and that's how the not advantegeous traits are passed on.

[booksoversex]

Evolution works on the level of the gene, not on the level of the organism or the species. On the level of the organism, it seems odd that asexuality could be a benefit, on the species level it could be understandable - but for the "asexual gene", it's goal is to replicate itself. Of course, if the asexual person does not have children, it won't - unless it works like a "gene switch" (don't remember the name of it now) that "turns" genes the organism to act a certain way. Of course, that still wouldn't make the gene succeed as it wouldn't be passed along down the generations such as genes are.

No, you're right, this is difficult to comprehend. I am wondering about this too. If evolution worked on the level of the species it could be understandable, avoiding overpopulation and all, but it doesn't.

[Jea]

Less births could be an advantage obviously. At the same time, since most of us don't have kids, the ace population doesn't grow as mutations usually do.

[Telecaster68]

Evolution works on the level of the gene, not on the level of the organism or the species.

Isn't there a bit of a debate about that? Obviously the bottom line is the gene being passed on, but I think the argument is that many species, and therefore their genetic material, survive best by co-operating in groups, so anything that helps that co-operation will continue to be passed on. And 'spare' carers of young could be a co-operative advantage for a group, as would, say, people who were more focused on developing technology or hunters who were more successful because they were less cautious, not having a family to support. This is all completely unsupported speculation of course.

Then again, there might just be a 1% probability of genetic mutations that can cause asexuality in the right environment in every generation - assuming there's an inherited element to the trait.

[Elluna Hellen]

It seems that LGBT+ are becoming much more common anyway, since the mid 20th century at least. It is possible that we are evolving to have a natural population control, with gay and asexual people unable to reproduce... I don't want to go and say we're more evolved than others but it explains why it's all becoming more common. We'll overpopulate this entire planet before long.

not sure if we're/they're becoming more common or if more people just dare to come out because it's slowly become more accepted to *be* LGBT+ since the mid 20th century.

[Dodoa]

Evolution works on the level of the gene, not on the level of the organism or the species.

Isn't there a bit of a debate about that? Obviously the bottom line is the gene being passed on, but I think the argument is that many species, and therefore their genetic material, survive best by co-operating in groups, so anything that helps that co-operation will continue to be passed on. And 'spare' carers of young could be a co-operative advantage for a group, as would, say, people who were more focused on developing technology or hunters who were more successful because they were less cautious, not having a family to support. This is all completely unsupported speculation of course.

Then again, there might just be a 1% probability of genetic mutations that can cause asexuality in the right environment in every generation - assuming there's an inherited element to the trait.

It's a bit more difficult with genes with intermediary heredity (I think tat's what it's called, I didn't take genetics in english) i.e. trates that are on a spectrum, like skin colour, which is coded on I think it was 12 different spots of our genome and every one of those can either say black or white and mixed together that gives all the possible shades of human skin tone and since sexuality is a spectrum too I'd imagine that genetically it might work in a similar way. and there are advantages to not being a comletely sex crazed maniac so it wouldn't be advantegous to have all the genes defining sexuality say sexual. So sometimes the genes of two Half and Half people (i.e. average) might combine to make an asexual person, the same way two moderately dark skinned people might have a very light skinned child.

[dissolved]

Ok so the short answer is: there are no evolutionary benefits to asexuality.

The whole purpose (for lack of a better word) of an organism is to reproduce as often as possible in order to ensure the survival of its genome, its genetic information. The general consensus is that something beneficial will persist in a genome and eventually spread to the entire population - or the majority at least - if allowed to, and on the other side of the coin, deleterious aspects will be removed from the population because the genome cannot compete with one that doesn't have those issues. However, that's not really applicable to humans... selection is not really at work in a species that allows (and encourages) the entire population to mate. The deleterious mutations etc and subsequent genetic disease will never die out when those members of the population are still spreading the problem genome, the deleterious loci, whatever. I'm not saying we need to prevent people from reproducing... that's something to discuss in Hot Box :P

I'm not saying asexuality is deleterious either, it's clearly not the case or this site wouldn't exist :P but it does mean that the drive to mate is lower or non-existent... that still doesn't mean reproduction doesn't happen, clearly. But thanks to the oversimplification of pretty much everything in genetics for the benefit of the laymen, there are these common misconceptions:

• There's a gene for everything. Nope. You could compare two identical twins, for example, one straight and one gay. They're genetically identical and they also shared the same uterus, so clearly they're not the reasons why sexuality varies. It's down to epigenetics and probably some random environmental stuff shoved in there for good luck... or maybe other factors we haven't even considered yet
• Everything, every gene, loci, whatever, is either beneficial or deleterious. Nope. The vast majority is under neutral selection, i.e. it doesn't give any selected advantage to an organism, but because it's not doing an harm either, it's not removed by selection, so it prevails by default.

Evolution works on the level of the gene, not on the level of the organism or the species.

Isn't there a bit of a debate about that? Obviously the bottom line is the gene being passed on, but I think the argument is that many species, and therefore their genetic material, survive best by co-operating in groups, so anything that helps that co-operation will continue to be passed on.

Technically evolution works on the level of the gene and the population, i.e. to fix a gene in a population, ensuring its survival.

There is also the phenomenon of the heterozygotous advantage (I don't know the correct english terms in genetics, sorry) which is most popularly described in scottish sheep. It occurs when a "good" trait is genetically cupled with a "bad trait" and both of those traits are passed on via the Dominant/recessive scheme.

It's called genetic hitchhiking :D I guess it has a little to do with with Medelian dominant/recessive trait inheritance... but it's mostly to do with selection acting on very specific loci and linked gene groups, which determines how likely something is to be passed on to offspring... recombination also plays a big part because these areas that are linked are inherited as one big "chunk" of chromosome rather than individual little loci. So for simplicity's sake, say there's a loci that contributes to something which in turn affects sexuality, that loci could easily be nested in other genes and elements which are readily passed on, then it's not unreasonable to see something like that prevail in a population.

[borealmist]

As others have pointed out there's not necessarily any direct evolutionary benefit to asexuality in itself.

However, due to the complex nature of how sexual orientation is determined, even if we only look at the biological aspects such as genes, prenatal hormones and brain structure, it seems quite possible that the separate composite traits that result in asexual or homosexual orientations can have evolutionary benefits that outweigh any disadvantage that may occur when some specific combinations lower the chance of that individual reproducing.

For example, we can look at something like the fraternal birth order theory of male sexual orientation, which tries to explain why the statistical likelihood that a male child will be homosexual rises by more than 30% per older brother he has. One hypothesis is that each male child that the mother carries will trigger the immune system and cause her to start producing antibodies to some proteins active during the sexual differentiation phase. For each male child the immune reaction will then interfere more with the masculinisation process which seems partially implicated in driving orientation.

If that theory is correct, it's quite possible that the traits in the immune system as well as the obvious high fertility and reproductive desire of the mother will easily offer an evolutionary advantage, while the fact that a few of the male offspring turn out homosexual might not be any disadvantage at all for the propagation of the mothers genes over the long term.

I think the concept of asexuality as an orientation is too young for much solid research around correlations to exist yet. Considering how rarely it seems to get fully expressed it would be enough that the composite traits causing the orientation confer a very slight advantage to the gene line itself to provide a logical foundation from an evolutionary perspective. Add to that the fact that asexuality might not even mean a zero offspring result and the possible tangential advantages for asexual people such as a lower STD chance and there's not a lot of evolutionary pressure working to remove the combination trait from the gene pool.

[booksoversex]

I can imagine one advantage, though: less reckless behaviour and less risk to be killed by a "contender" over a sexual or romantic conquest. Still not too uncommon, and even more common before. It also lowers the risk of being killed over jealousy by a partner. I guess before you had contraceptives and probably quite a bit of the sexual activity was involuntary, it was a good chance asexual women would get pregnant anyways and bring forth an offspring, or that asexual people, men or women, more often found a stable partner and stayed away from risk behaviour, increasing their chances of survival.