Homosexuality and the Theory of Evolution

Mickey Dazzler

So..... I've always considered myself to be an enlightened chap (despite some of my previous posting history)... I have always been a firm believer in the in theory of evolution. Survival of the fittest, natural selection and all that jazz.

I also believe that homosexuality is a natural part of the human condition, not only humans but in the animal kingdom too. People are born that way just like people are born with blue eyes or brown eyes... they just are. There appears to be a constant proportion of the population that are homosexual in all societies.. about 5% I think.... and there always has been and always will be.

But how how can that be?

How can the "gay" gene be perpetuated through the generations if it does not actively reproduce. I understand that only about 20% of gay men have children and if only 5% of the population is gay that is not many children of gay men or women.

It only occurred to me when watching a interview with the evolutionary biologist Richard Dawkins. He was asked where do gays fit into the theory and he basically said he had no idea. It was a mystery of science...

The theory of evolution proposes that strong genes are passed on through the generations and weak genes are bred out over zillions of years all in the name of a better chance in survival. If someone is born gay and therefore much less likely to have children in a traditional fashion, then why is a steady 5% of the population born fabulous?

Dr. Shrike

Have a look into the "gay uncle theory". Basically the idea is that if a gay hangs around with the female members of the tribe while the other males are off hunting, the females are better protected. There's a lot of assumptions there of course.

The way evolution works, it could just as easily have been the gay chaperone theory, eg. having a gay relative stopping the women getting interfered with by men from other gene pools, thus concentrating "gay genes" within the immediate tribe.

There's been some suggestion recently that perhaps the opposite was true, and that homosexual genes were spread by bisexual men who used the pretence of being gay to get closer to women.

nozzferrahhtoo

Mickey Dazzler wrote: »

How can the "gay" gene be perpetuated through the generations if it does not actively reproduce.

I think there are two ways to come at your question that might help you. One way assumes there even is a "gay gene" and the other does not. I do not think there IS a "gay gene" so the former is not that useful except to serve as a thought experiment for you.

So approach one. Think of a hive species as a great example of this line of thinking. Be that bees or ants in the insect world, or something like the bald mole rat in the mammalian world. In these species the genetics dictate that the vast vast majority of the species will never produce. They are soldiers, or drones, and so forth.

Ask yourself, does this harm the species in any way? Not a bit! In fact it strengthens it. Also ask yourself, if the vast majority of the species are carrying genetics for non-reproduction... then should it not be bred out? Clearly again the answer is no, because it is NOT being bred out.

What this thought stream should be showing you is that.... the idea that a gene causing individuals to not reproduce should not survive Natural Selection.... is simply an erroneous idea. So if a "Gay Gene" did exist then there is no reason to expect that it should breed itself out of the species over time.

The biological explanation for this is complex but I can give a simplified explanation here. When a gene exists it can be "expressed" or not. That is, it can be "switched on" or not. When a "Gay Gene" is expressed it would therefore make the host gay. When it is not however, it can still be present.

So for the continued survival of such a gene all that is required is that carriers of the gene to reproduce. Whether they be homosexuals where the gene is expressed who reproduce sexually anyway..... OR heterosexual carriers of such a gene. Either way (likely a combination of both heavily weighted towards the latter) there is no reason to expect the genetics to be bred out.

So approach two is to realise no one has actually identified any such gene. And I see no reason to think one exists. Rather, I expect that any genetic element there is to Homosexuality to be linked entirely to genetics that we already have.

What many people forget, and in fact a huge number of people do not even know, is that every one of us contain the full set of genes for our species. That is to say, we all contain the genes for being male AND female. If you are a guy, you have all the genes inside you for having female genitals, breasts, lactation and more. In fact my own recently born son at the age of two weeks has been lactating. A not unheard of effect of the large quantity of the hormone Lactase that babies get through breast feeding.

The famed XY chromosomes that decide if we are male or female essentially decide which genes are "expressed" (turned on) in our bodies. But the story does not end there. Which genes are expressed is also decided by what hormones and other environmental elements are within us, both live here and now today (you would start lactating if I gave you a large course of ongoing Lactase too), and during the development as a fetus. This is, for example, the reason why men have nipples. We essentially as men carry all the genetics for being female too.

So for this reason I also would not expect homosexuality to be bred out of the species because to do so you would have to breed out the fact that we carry all the genes for both sexes. If there is a genetic element to homosexuality therefore.... what I am saying is there is no reason to expect a "gay gene"..... rather there is every reason to expect it is merely the "wrong" (after all who is to say it is wrong at all, I use the word wrong only for clarity here) expression of the "wrong" genes in the "wrong" person.

So if there is a genetic element to sexual attraction, and I fully expect there is, then all homosexuality is, is the expression of the genetics for sexual attraction normally active in the opposite sex to that of the current host.

Mickey Dazzler wrote: »

It only occurred to me when watching a interview with the evolutionary biologist Richard Dawkins. He was asked where do gays fit into the theory and he basically said he had no idea. It was a mystery of science...

I would be interested to read a transcript or watch such an interview because I am highly surprised that someone as well versed in Evolutionary Science had no explanation whatsoever for the phenomenon. Especially given a lot of what I just wrote would be highly steeped in his tendency to take a "Genes Eye View" of genetic evolution.

floggg

nozzferrahhtoo wrote: »

I think there are two ways to come at your question that might help you. One way assumes there even is a "gay gene" and the other does not. I do not think there IS a "gay gene" so the former is not that useful except to serve as a thought experiment for you.

So approach one. Think of a hive species as a great example of this line of thinking. Be that bees or ants in the insect world, or something like the bald mole rat in the mammalian world. In these species the genetics dictate that the vast vast majority of the species will never produce. They are soldiers, or drones, and so forth.

Ask yourself, does this harm the species in any way? Not a bit! In fact it strengthens it. Also ask yourself, if the vast majority of the species are carrying genetics for non-reproduction... then should it not be bred out? Clearly again the answer is no, because it is NOT being bred out.

What this thought stream should be showing you is that.... the idea that a gene causing individuals to not reproduce should not survive Natural Selection.... is simply an erroneous idea. So if a "Gay Gene" did exist then there is no reason to expect that it should breed itself out of the species over time.

The biological explanation for this is complex but I can give a simplified explanation here. When a gene exists it can be "expressed" or not. That is, it can be "switched on" or not. When a "Gay Gene" is expressed it would therefore make the host gay. When it is not however, it can still be present.

So for the continued survival of such a gene all that is required is that carriers of the gene to reproduce. Whether they be homosexuals where the gene is expressed who reproduce sexually anyway..... OR heterosexual carriers of such a gene. Either way (likely a combination of both heavily weighted towards the latter) there is no reason to expect the genetics to be bred out.

So approach two is to realise no one has actually identified any such gene. And I see no reason to think one exists. Rather, I expect that any genetic element there is to Homosexuality to be linked entirely to genetics that we already have.

What many people forget, and in fact a huge number of people do not even know, is that every one of us contain the full set of genes for our species. That is to say, we all contain the genes for being male AND female. If you are a guy, you have all the genes inside you for having female genitals, breasts, lactation and more. In fact my own recently born son at the age of two weeks has been lactating. A not unheard of effect of the large quantity of the hormone Lactase that babies get through breast feeding.

The famed XY chromosomes that decide if we are male or female essentially decide which genes are "expressed" (turned on) in our bodies. But the story does not end there. Which genes are expressed is also decided by what hormones and other environmental elements are within us, both live here and now today (you would start lactating if I gave you a large course of ongoing Lactase too), and during the development as a fetus. This is, for example, the reason why men have nipples. We essentially as men carry all the genetics for being female too.

So for this reason I also would not expect homosexuality to be bred out of the species because to do so you would have to breed out the fact that we carry all the genes for both sexes. If there is a genetic element to homosexuality therefore.... what I am saying is there is no reason to expect a "gay gene"..... rather there is every reason to expect it is merely the "wrong" (after all who is to say it is wrong at all, I use the word wrong only for clarity here) expression of the "wrong" genes in the "wrong" person.

So if there is a genetic element to sexual attraction, and I fully expect there is, then all homosexuality is, is the expression of the genetics for sexual attraction normally active in the opposite sex to that of the current host.



I would be interested to read a transcript or watch such an interview because I am highly surprised that someone as well versed in Evolutionary Science had no explanation whatsoever for the phenomenon. Especially given a lot of what I just wrote would be highly steeped in his tendency to take a "Genes Eye View" of genetic evolution.

That was a great post - or at least what I read of it. I couldn't get past the fact that you're NEW BORN SON is LACTATING!

Mind blown!!!!!!!

Now all I can think is whether he can now feed himself?

nozzferrahhtoo

floggg wrote: »

That was a great post - or at least what I read of it. I couldn't get past the fact that you're NEW BORN SON is LACTATING!

Mind blown!!!!!!!

Now all I can think is whether he can now feed himself?

No more than the human centipede could I guess. And for some of the same reasons.

But yes new borns can do this, male and female, and new born girls can even have pseudo periods. New Born children, you will learn as I have, are a plethora of surprises, many of them kinda gross

I was new to this myself until it happened. The milk produced is called Neonatal Milk or Witch's Milk and is said to happen in about 5% of new borns.

J_E

I always thought perhaps it was nature's way of population control, but honestly I've never really looked into it or thought about it too much.

daithi84

There are many theories about homosexuality, genetics and/or hormone exposure in the womb. I would see it as natures way of population control as mentioned earlier. As the human population is split 50/50 into male and female and for a species to grow you need more females than males as males can impregnate more multiple females with monogamy being a societal invention rather than a biological one. So as there are too many males being born that some males will be homosexual. This could maybe explain why there seems to be more gay men than lesbians. Sexuality also cant be defined into 2 distinct groups of hetero and homosexual. Sexuality is more of a scale, also there is the theory that all humans are bisexual in nature but due to societal influences this has been demonised so that the majority will purely identify as heterosexual.

I would tend to agree with the hormonal debate as genetics doesnt fully explain transsexuals and also if there is a gay gene there would also have to be a straight gene. I purely identify as homosexual and have no feelings towards women but i do believe there is a spectrum of sexuality where a person if inclined towards a specific side with the majority of the population in the bisexual range.

unfortunately

Here is Dawkins discussing the ideas: http://www.youtube.com/watch?v=MHDCAllQgS0

Genes are rarely "for" one thing - it's more complicated than that. But could you have a situation (for male homosexuality) where if a gene was present in a male it would make him more likely to be gay if certain environmental conditions arise (eg. if exposed to certain hormones in the womb) but if the gene is present in a female it makes her more fertile.

So the advantage of increased fertility drives the prevalence of homosexuality, and as said before "the gay uncle" would also be an advantage from this gene.

Again, the gene present in males not influenced by the environmental trigger would mean they turn out heterosexual but it may play a different role making them more reproductively successful. I know that gay men are more likely to have gay brothers but I wonder if a study could be done to see if a gay man's straight brothers or sisters have more children on average.

Tainor

Firstly trying to simply homosexuality to bare genes is a very difficult, if not impossible task. Homosexuality is a very complex evolutionary mechanism, which involves perhaps many genetic markers and environmental factors.

With all of our genetic and psychological understanding of today, we are still hard pressed to define what causes homosexuality and why it has been present in the majority of species on the planet.

Much studies have tried to bring the cause down to a genetic root, but all have failed to identify a particular marker that is present in every homosexual person. There have been documented cases of identical twins (monozygotic) of which only one has identified as homosexual. Monozygotic twins share over ≈99.99 percent of their DNA. Ergo the genes to express homosexuality require an environmental factor in play, and a psychological upbringing (nature versus nurture concept)

Recent studies have tried to incorporate the epi-genetic markers during pregnancy, that will facilitate the expression of homosexuality, which could support the idea of how monozygotic twins can have different sexual orientation if they share the same genetic make up, but the studies are still early and many geneticists regard epi-genetics to be a keen to "dark matter" of physics, as a not fully understood and complex (aka not straight-forward) to comprehend factor in biology.

From much of my research in homosexuality that I have done, my personal opinion is that it is a very complex mechanism regulated by many genes and that it requires an environmental (epi-genetic?) factor to be expressed.
It is older than homo-sapiens sapiens as it is present in specie older than us, and it has been carried over for millennia despite the low tendency to be expressed (5-10 percent) in species. Hence it is an important factor and evolutionary beneficial if it has not been deleted from our active coding DNA bank. My personal opinion is that it is a form of population control within species in order to ensure that their rate of growth does not outgrow the available resources within the environment, and even in such a low but continuous rate it helps to curve out the over-growth factor, yet one can argue that humans have far outgrown their global stable population currently?

nozzferrahhtoo wrote: »

So if there is a genetic element to sexual attraction, and I fully expect there is, then all homosexuality is, is the expression of the genetics for sexual attraction normally active in the opposite sex to that of the current host.

I agree with your first approach to homosexuality, as a form of none-reproducing carrying set of genes. But as regards to every human possessing the genetic set for all possible sexes, well this is not the case.
Only males possess both the Y chromosomes, we males start our development as females, until the Y chromosome part over-takes the role of sexual expression and we begin to develop as male forms. The Y chromosome is far smaller in genetic size and coding carrying, also it is prone to more "junk coding", but it is the marker necessary for male development.

On the other hand females only carry two X chromosomes, and hence this would not explain how females can identify as homosexuals if they do not carry Y chromosomes to genetically express their attraction to the same sex?

As I said it is a very, very complex question that perhaps does not have a single answer and a pin-pointing factor, rather it is a set of factors that when coming into play give rise to homosexuality.

nozzferrahhtoo

Tainor wrote: »

as regards to every human possessing the genetic set for all possible sexes, well this is not the case.

It is in fact the case. Just a simplification of the case for a lay audience. As you point out, when we get pedantic and specific, there are some differences. You point out for example that only males possess a Y chromosome.

But specifics are not important to the point I am making and I left them out so as not to confuse a lay audience or to bombard them with irrelevancies. The point I am making is that a majority % by far of the genes "for" being male or female and in females and males.

Tainor wrote: »

On the other hand females only carry two X chromosomes, and hence this would not explain how females can identify as homosexuals if they do not carry Y chromosomes to genetically express their attraction to the same sex?

If the Y chromosome was the sole point of reference as to which "male" genes would be actively expressed you would be correct here. We would have an issue explaining female homosexuals.

A good analogy is to Microsoft Windows Client and Server editions. It turns out that on some versions the CD/DVD you are installing are identical to each other. All except for one tiny byte of information which decides whether the CD will appear to the user to be Client or Server.

It does not work like that in humans. The X/Y chromosome is only one port of call in determining which genetics will be dormant and which expressed. Hormones and other factors also play a role in this. So the issue with explaining female homosexuals is not as great an issue as you might expect for the gene expression theory of homosexuality.

AngusB

Mickey Dazzler wrote: »

So..... I've always considered myself to be an enlightened chap (despite some of my previous posting history)... I have always been a firm believer in the in theory of evolution. Survival of the fittest, natural selection and all that jazz.

I also believe that homosexuality is a natural part of the human condition, not only humans but in the animal kingdom too. People are born that way just like people are born with blue eyes or brown eyes... they just are. There appears to be a constant proportion of the population that are homosexual in all societies.. about 5% I think.... and there always has been and always will be.

A meta-analysis of Kinsey puts the figure of adults who are primarily same sex attracted at between 4%-17%

It must be observed that the operative word is “primarily” and that’s not to say than some or many who are primarily opposite sex attracted are not also, to varying degrees, same sex attracted.

Mickey Dazzler wrote: »

How can the "gay" gene be perpetuated through the generations if it does not actively reproduce. I understand that only about 20% of gay men have children and if only 5% of the population is gay that is not many children of gay men or women.

Why do you think “homosexuality” is partially or completely the result of a genetic disposition?

Mickey Dazzler wrote: »

The theory of evolution proposes that strong genes are passed on through the generations and weak genes are bred out over zillions of years all in the name of a better chance in survival. If someone is born gay and therefore much less likely to have children in a traditional fashion, then why is a steady 5% of the population born fabulous?

There are an awful lot of “if’s” in that paragraph.
Firstly, you seem to assume there is a gene which influences or controls sexual attraction. Have you evidence for this? Where do you get your figure of 5% from? How do you know there is a steady “5%” of the population born primarily same sex attracted?

As the famous judge says, “If I were 4 inches taller I could have been a model”

Genegirl83

nozzferrahhtoo wrote: »

I think there are two ways to come at your question that might help you. One way assumes there even is a "gay gene" and the other does not. I do not think there IS a "gay gene" so the former is not that useful except to serve as a thought experiment for you.

So approach one. Think of a hive species as a great example of this line of thinking. Be that bees or ants in the insect world, or something like the bald mole rat in the mammalian world. In these species the genetics dictate that the vast vast majority of the species will never produce. They are soldiers, or drones, and so forth.

Ask yourself, does this harm the species in any way? Not a bit! In fact it strengthens it. Also ask yourself, if the vast majority of the species are carrying genetics for non-reproduction... then should it not be bred out? Clearly again the answer is no, because it is NOT being bred out.

What this thought stream should be showing you is that.... the idea that a gene causing individuals to not reproduce should not survive Natural Selection.... is simply an erroneous idea. So if a "Gay Gene" did exist then there is no reason to expect that it should breed itself out of the species over time.

The biological explanation for this is complex but I can give a simplified explanation here. When a gene exists it can be "expressed" or not. That is, it can be "switched on" or not. When a "Gay Gene" is expressed it would therefore make the host gay. When it is not however, it can still be present.

So for the continued survival of such a gene all that is required is that carriers of the gene to reproduce. Whether they be homosexuals where the gene is expressed who reproduce sexually anyway..... OR heterosexual carriers of such a gene. Either way (likely a combination of both heavily weighted towards the latter) there is no reason to expect the genetics to be bred out.

So approach two is to realise no one has actually identified any such gene. And I see no reason to think one exists. Rather, I expect that any genetic element there is to Homosexuality to be linked entirely to genetics that we already have.

What many people forget, and in fact a huge number of people do not even know, is that every one of us contain the full set of genes for our species. That is to say, we all contain the genes for being male AND female. If you are a guy, you have all the genes inside you for having female genitals, breasts, lactation and more. In fact my own recently born son at the age of two weeks has been lactating. A not unheard of effect of the large quantity of the hormone Lactase that babies get through breast feeding.

The famed XY chromosomes that decide if we are male or female essentially decide which genes are "expressed" (turned on) in our bodies. But the story does not end there. Which genes are expressed is also decided by what hormones and other environmental elements are within us, both live here and now today (you would start lactating if I gave you a large course of ongoing Lactase too), and during the development as a fetus. This is, for example, the reason why men have nipples. We essentially as men carry all the genetics for being female too.

So for this reason I also would not expect homosexuality to be bred out of the species because to do so you would have to breed out the fact that we carry all the genes for both sexes. If there is a genetic element to homosexuality therefore.... what I am saying is there is no reason to expect a "gay gene"..... rather there is every reason to expect it is merely the "wrong" (after all who is to say it is wrong at all, I use the word wrong only for clarity here) expression of the "wrong" genes in the "wrong" person.

So if there is a genetic element to sexual attraction, and I fully expect there is, then all homosexuality is, is the expression of the genetics for sexual attraction normally active in the opposite sex to that of the current host.



I would be interested to read a transcript or watch such an interview because I am highly surprised that someone as well versed in Evolutionary Science had no explanation whatsoever for the phenomenon. Especially given a lot of what I just wrote would be highly steeped in his tendency to take a "Genes Eye View" of genetic evolution.

Hmm... I dont know about comparing say, moles to humans though because of the huge amounts of viable inbreeding. Moles likely don't have as much potential for genetic illness as humans and actually, with regards to loads of genes not being passed on, the labour are almost all related so there is very little variation to begin with. They have one queen and just loads of different worker, male voles in a labour, right?

I'm not sure about there not being actual gay genes. It is HIGHLY unlikely to be monogenic, is probably due to a few and almost definitely has an epigenetic aspect (so like, post transcriptional, non-genome encoded modifications that would definitely make the whole thing MUCH harder to define or study). My best friend is a researcher in neurogenetics and only this morning he mentioned about sexual perceptive changes by a single gene mutation in a recent study and in his opinion (and possibly the authors), possibly due to chemosensory receptor alterations. So essentially in this (early study) a single gene actually altered neuro circuits.
He also works really closely with Drosophila melongaster too and apparently there is one single gene mutation that can lead to changes in expression patterns of almost 2000 genes which masculinised the flies behaviour. So, depending on which genes were altered in any given organism, you might find a spectrum were homosexuality falls as well as transexuality.

In my opinion though, while it would be handy to put it all down to the genes and blame them for homosexuality, I kinda feel like needing a gene demeans us a compassionate, rational people though. I mean personally I just think that someone should be able to do whatever they want (within reason) because we can see the merits of personal freedom and not simply because we know their blueprints say they can't help their behaviour. It shouldn't take genomics to make us harmonious.

With regards the OP: Possibilities...
Population control, gay uncle theory, non harmful variation, in utero hormone exposure, intrinsic testosterone levels. Not to mention the countless environmental factors likely needed in addition to genetic factors. In my opinion...

nozzferrahhtoo wrote: »

It is in fact the case. Just a simplification of the case for a lay audience. As you point out, when we get pedantic and specific, there are some differences. You point out for example that only males possess a Y chromosome.

If the Y chromosome was the sole point of reference as to which "male" genes would be actively expressed you would be correct here. We would have an issue explaining female homosexuals.

Also there are certain things that usually only occur in females or males more or less. As in if it occurs on the X or Y chromosome. Y-linked or X-linked.
And we do have an issue with female homosexuals, likely male and female homosexuality will not have the exact same basis.

Disclaimer: I could be mistaken or oversimplifying some things here, eukaryotic genetics is a passing interest not my forte...
Don't shoot!

nozzferrahhtoo

Genegirl83 wrote: »

Hmm... I dont know about comparing say, moles to humans though because of the huge amounts of viable inbreeding.

It is not really the comparison I am making. It would be an error, probably my fault in how I worded it, to think I am comparing humans to mole rats... or their breeding.... in any large way.

The point I am making is more simple than that. Which is that the assumption.... that a gene which causes hosts to not reproduce should be bred out of a species.... is simply a false one but one shared by a surprisingly large % of the lay population.

The mole rats and other hive species are just one example of this and the easiest one to explain to the Lay Person on the subject. There are many more however.

As with all comparisons and analogies there is always a danger people will read too much into them, or over extend the comparison. The point, as I said, is merely to address the idea that such genes, were they to exist, would by necessity be bred out by natural selection.

Genegirl83 wrote: »

I'm not sure about there not being actual gay genes.

I am not "sure" about it either. I am merely hoping to point out that at this time we have no evidence for any. That certainly does not mean there is none. I would just be pointing out that there does not NEED to be one and in fact there are many other ways, genetically, that homosexuality could come about without the requirement for genes dedicated to it.

Genegirl83 wrote: »

It is HIGHLY unlikely to be monogenic, is probably due to a few and almost definitely has an epigenetic aspect

Agreed but as I tried to point out earlier, I am over simplifying in order to not confuse people who simply are not versed in the subject of Evolution. It is all too easy... and has happened all too many times in the past.... to turn people glass eyed if you go too deep and detailed.

We could go deeper into the discussion on the topic but I think the level I presented it at is sufficient to address the OPs questions and points.

If I were to pin my expectations on my sleeve I think it will likely turn out all the theories and hypotheses are right at the same time. That our sexuality and expression of it are genetic, epigenetic, neural, hormonal AND yes even learned behavior or even (the red button for many).... personal choice.

The quantities of each not being fixed but being variable from person to person with much bunching on each continuum (for example sexual orientation by choice is clearly what all but a small minority reject).