Is homosexuality genetic?

[Drooper]

I've read numerous articles in the past on this question.

But the thing that occurs to me is:

Would not evolutionary theory preclude the existance of genetically caused homosexuality?

[BillyJoe]

Quote:

Originally posted by Drooper
Would not evolutionary theory preclude the existance of genetically caused homosexuality?

It may be linked to a favourable genetic trait like love of your fellow man.

Think about it.

[bjornart]

Quote:

Originally posted by Drooper
I've read numerous articles in the past on this question.

But the thing that occurs to me is:

Would not evolutionary theory preclude the existance of genetically caused homosexuality?

No.

For the same reason that other 'bad' genes aren't precluded by evolutionary theory. All a 'bad' gene has to do is be recessive, or have a beneficial 'side-effect', or be a combination of several genes (making you gay only if you have 'this gene' and 'that gene'), and it can stick around forever.

Quote:

Originally posted by Drooper
I've read numerous articles in the past on this question.

But the thing that occurs to me is:

Would not evolutionary theory preclude the existance of genetically caused homosexuality?

No it isn't how could it be, unless you prescribing to the thought the homosexual gene is carried and passed on like any other genetic marker ot trait?
How would that then go to explain a family history of continous 'hetrosexual 'people and then one day up pops a non hetrosexual person into the mix?

[LuxFerum]

Quote:

Originally posted by Biker Babe

How would that then go to explain a family history of continous 'hetrosexual 'people and then one day up pops a non hetrosexual person into the mix?

cheating

[BillHoyt]

Quote:

Originally posted by Biker Babe
No it isn't how could it be, unless you prescribing to the thought the homosexual gene is carried and passed on like any other genetic marker ot trait?
How would that then go to explain a family history of continous 'hetrosexual 'people and then one day up pops a non hetrosexual person into the mix?

A recessive allele could do exactly that: "hide" for generations.

As for the "wouldn't evolution preclude this" argument, the short answer is no. The longer answer is that many unfit (in the evolutionary selection sense) alleles are maintained simply by a combination of mutation rates and genetic drift. The even longer answer is that you have to factor in human social factors which, for millenia, forced homosexuals into the closet. Many married and had children. Many continue to marry and have children before they finally discover their homosexuality and give up the heterosexual ruse.

To the direct question of what might genetically dictate this, I'd point your attention to the fruit fly mutation found in 1963. The mutant males attempted to mate with other males, and ignored females. The mutation was originally named fruity, but has since been renamed fruitless.American Scientist

Cheers,

[UnrepentantSinner]

In mammals sometimes genes develop that are social and don't necessarily effect direct procreative efforts. Compassion for the sick, dying and retarded have no evolutionary value for direct procreative efforts, but we have them anyway.

It's all a product of being a social being.

Besides {political incorrectness} where would we get our choreographers and interior decorators from? {/political incorrectness}

[arcticpenguin]

Here's the best evidence yet for a genetic basis of homosexuality: http://news.bbc.co.uk/1/hi/sci/tech/2266135.stm

Someone engineered a gene such that homosexual behaviour could be triggered by temperature. It's clear and reproducible. Oh, and it's in Drosophila fruit flies. Good luck extrapolating to human bahaviour.

[Dymanic]

I wonder if anyone's ever done a study on whether homosexuality in humans is more prevalent in warmer climates?

If this so called homosexual gene pops up in a heterosexual 9th generation , are you claiming that they have been carrying it recessively, how is that possible?

I would be more inclined to go with a view that it is a hormonal and brain chemical change that cause this. It is not sex but a gender cause.

[Denise]

I've read that the denser the population, the higher percentage of homosexuality. I haven't studied it, or seen any studies, but I have read about it. Have there been studies of percentage of homosexual behavior in animal colonies with high density vs low density?

If it is, in fact, there is a higher number of homosexual animals in denser populations then I think it would have an evolutionary advantage. That is, of course, if the animals do not reproduce. It allows for less offspring for competition on scarce resources.

Of course, the question would still remain if homosexuality is genetic or not. Maybe it's not tied to the genes but hormones that are bathing the fetus in the womb depending on the situation of the population.

[BillHoyt]

Quote:

If this so called homosexual gene pops up in a heterosexual 9th generation , are you claiming that they have been carrying it recessively, how is that possible?

I would be more inclined to go with a view that it is a hormonal and brain chemical change that cause this. It is not sex but a gender cause.

Frenchy,

Let's take this away from homosexuality for a moment, and look strictly at recessive/dominant alleles. How can a recessive gene suddenly "pop up" after several generations? The simple answer is: it doesn't. The recessive allele was always there, not showing itself because it never had the chance. To express itself, a single individual would need to have two of the recessive alleles. All other individuals express the dominant allele.

Okay so far, so why does the recessive "hide"? Let's say that only 10% of the alleles in a population are this recessive one. To show the effects of the allele, an individual needs to have two such alleles. The probability of that happening is .1 x .1 = .01. That is, 10% of the alleles in the population can be this recessive, yet only 1% of the individuals will express the recessive trait.

Cheers,

A: No there is no homosexual gene in mammals. If there was, then quite rightly, as someone has already pointed out, no way for that homosexual gene to be passed on to the next generation. The key to understanding passing on genetic traits is through the pathway of natural selection.

The cause of homosexuality is not genetic, but it is biological in origin, and it is not a choice, any more than heterosexuality is a choice. It is also not related to environmental conditions, culture, race, creed or any other societal pressure.

[garys_2k]

Quote:

Originally posted by Titananarchy
A: No there is no homosexual gene in mammals. If there was, then quite rightly, as someone has already pointed out, no way for that homosexual gene to be passed on to the next generation. The key to understanding passing on genetic traits is through the pathway of natural selection.

The cause of homosexuality is not genetic, but it is biological in origin, and it is not a choice, any more than heterosexuality is a choice. It is also not related to environmental conditions, culture, race, creed or any other societal pressure.

It must be nice to have all the answers...

[BillHoyt]

Quote:

Originally posted by Titananarchy
A: No there is no homosexual gene in mammals. If there was, then quite rightly, as someone has already pointed out, no way for that homosexual gene to be passed on to the next generation. The key to understanding passing on genetic traits is through the pathway of natural selection.

The cause of homosexuality is not genetic, but it is biological in origin, and it is not a choice, any more than heterosexuality is a choice. It is also not related to environmental conditions, culture, race, creed or any other societal pressure.

Titanarchy,

Your first claim here is tantamount to claiming that no early-onset lethal genetic disease exists. This is patently untrue. Your second claim is that something can be biologic yet not genetic. This is also patently absurd. The basic flow of biological information is DNA->RNA->protein. For something to be biologically (rather than culturally) defined, it must perforce have its origins in the genes.

Cheers,

Quote:

Originally posted by BillHoyt
[b]

Titanarchy,

Your first claim here is tantamount to claiming that no early-onset lethal genetic disease exists. This is patently untrue.

If the early-onset genetic mutation regularly kills the host before he/she/it is able to reproduce, then yes. There are genetic mutations such as cystic fibrosis, where people with only one half of the information are perfectly fine, but when combined from both parents will produce an early-onset genetic disease. That is different.

Quote:

Your second claim is that something can be biologic yet not genetic. This is also patently absurd.

Wrong! Terribly sorry Bill, but there's a gap in your knowledge of mammalian reproduction, and in it is the answer to how homosexuality arises and why it is not related (directly) to genetics.

Quote:

The basic flow of biological information is DNA->RNA->protein. For something to be biologically (rather than culturally) defined, it must perforce have its origins in the genes.

Cheers,

No Bill, it doesn't. There are other mechanisms which come into play with regard to brain structure and function whose origin is not directly the result of genetic mutation.

There is no gay gene. There is however, a biological reason why homosexuality appears in mammals (in general) and humans (in particular)

Sorry garys_2k for sounding too precise about it. Perhaps you unused to definite answers when social scientists and others positively embrace ambiguity and, dare I say it, ignorance. The question of the origin of homosexuality has been polarised between genetics and environmental causes. However mammalian reproduction introduces a third reason which is biological in origin but which does not require a genetic precursor to happen.

[boooeee]

Quote:

Wrong! Terribly sorry Bill, but there's a gap in your knowledge of mammalian reproduction, and in it is the answer to how homosexuality arises and why it is not related (directly) to genetics.

What specifically about mammalian reproduction leads to homosexuality? Just curious.

[BillHoyt]

Quote:

Originally posted by Titananarchy
If the early-onset genetic mutation regularly kills the host before he/she/it is able to reproduce, then yes. There are genetic mutations such as cystic fibrosis, where people with only one half of the information are perfectly fine, but when combined from both parents will produce an early-onset genetic disease. That is different.

There are lethal genetic defects that kill before puberty. Always have been. Always will be. The problem is you have an extraordinarily limited understanding of how evolution works.

Now do a bit of research on Duchene's Muscular Dystrophy, a lethal, X-linked characteristic. Male fetuses spontaneously abort. Females are born with DMD.
a bit on DMD

That's just the first example. If you like, I can more directly address your misunderstandings about evolution. If you care to persist in this idiotic line of reasoning, I will simply pepper you with more examples that refute your preposterous claim. Your move.

Quote:

Wrong! Terribly sorry Bill, but there's a gap in your knowledge of mammalian reproduction, and in it is the answer to how homosexuality arises and why it is not related (directly) to genetics.

Straw man. I never said homosexuality in mammals was caused by genetics. I have spoken only to homosexuality in Drosophila and to the various erroneous claims about evolution that have been made here.

Quote:

No Bill, it doesn't. There are other mechanisms which come into play with regard to brain structure and function whose origin is not directly the result of genetic mutation.

There is no gay gene. There is however, a biological reason why homosexuality appears in mammals (in general) and humans (in particular)

Sorry garys_2k for sounding too precise about it. Perhaps you unused to definite answers when social scientists and others positively embrace ambiguity and, dare I say it, ignorance. The question of the origin of homosexuality has been polarised between genetics and environmental causes. However mammalian reproduction introduces a third reason which is biological in origin but which does not require a genetic precursor to happen.

Balderdash. If it is biological, it is genetic, sir. Stop with the lame proclamations and get to marshalling evidence.

Cheers,

[arcticpenguin]

Quote:

Originally posted by BillHoyt

Balderdash. If it is biological, it is genetic, sir. Stop with the lame proclamations and get to marshalling evidence.

I don't know what he's getting at, but there is the possibility of it being developmental; i.e. due to environmental influence at specific stages of growth.

All in all he sounds much too certain of himself on a topic where the science is not clear.

[arcticpenguin]

Quote:

Originally posted by Titananarchy

Wrong! Terribly sorry Bill, but there's a gap in your knowledge of mammalian reproduction, and in it is the answer to how homosexuality arises and why it is not related (directly) to genetics.

No Bill, it doesn't. There are other mechanisms which come into play with regard to brain structure and function whose origin is not directly the result of genetic mutation.

There is no gay gene. There is however, a biological reason why homosexuality appears in mammals (in general) and humans (in particular)

Put up or shut up. You say there are mechanisms and reasons but so far have refused to name any.

[BillHoyt]

Quote:

Originally posted by arcticpenguin

I don't know what he's getting at, but there is the possibility of it being developmental; i.e. due to environmental influence at specific stages of growth.

All in all he sounds much too certain of himself on a topic where the science is not clear.

Hi, A/P,

But those influences would be cultural, not biological. Frankly, this one is a pompous clown who is already past the limits of his knowledge. He'll have to do more than proclaim and gainsay to make any headway.

Cheers,

[arcticpenguin]

Quote:

Originally posted by BillHoyt

But those influences would be cultural, not biological.

Not necessarily, could be chemical and therefore biological. Influence of hormones in the womb, that sort of thing. Agreed on the other point.

[BillHoyt]

Quote:

Originally posted by arcticpenguin

Not necessarily, could be chemical and therefore biological. Influence of hormones in the womb, that sort of thing. Agreed on the other point.

Most of the fetal hormones are from the fetus itself, rather than from the mother. The placental barrier permits transfer of maternal steroidal hormones, but largely blocks maternal protein hormones.

Cheers,

[Denise]

I read somewhere that the fetus is female before it is bathed in a certain hormone, I believe testosterone which causes the fetus to take on male secondary charactoristics. The baby was genetically XY before hand, but it's not clear how the hormones "know" which fetus to bathe the hormone with. Does this make any sense?

[Denise]

Quote:

Originally posted by BillHoyt


Most of the fetal hormones are from the fetus itself, rather than from the mother. The placental barrier permits transfer of maternal steroidal hormones, but largely blocks maternal protein hormones.

Cheers,

OMG! LOL! Read the post I just posted while you were posting! Looks like you answered my question! Cue twilight theme music....

[BillHoyt]

Quote:

Originally posted by Denise
I read somewhere that the fetus is female before it is bathed in a certain hormone, I believe testosterone which causes the fetus to take on male secondary charactoristics. The baby was genetically XY before hand, but it's not clear how the hormones "know" which fetus to bathe the hormone with. Does this make any sense?

Worshipful one,

I think you mean primary sexual characteristics. The adam's apple, deep voice, beard and ability to guzzle great quantities of bad beer are the secondary sexual characteristics. The hormones are triggered during the gonadal differentiation phase of embryological development. The genes for those hormones reside on the Y chromosome.

Cheers,

[BillHoyt]

Quote:

Originally posted by Denise


OMG! LOL! Read the post I just posted while you were posting! Looks like you answered my question! Cue twilight theme music....

Hmmm, you did mean twilight zone there and not some sort of romantic serenade? Shades of that other thread...

Cheers,

[Denise]

Quote:

Originally posted by BillHoyt


Worshipful one,

I think you mean primary sexual characteristics. The adam's apple, deep voice, beard and ability to guzzle great quantities of bad beer are the secondary sexual characteristics. The hormones are triggered during the gonadal differentiation phase of embryological development. The genes for those hormones reside on the Y chromosome.

Cheers,

Yep, you got me. I was thinking penis and testes which, of course, are primary. At least to most men anyhow from what I've heard.

Anyhow, is there any measurable differences attributable from testosterone on homosexual vs heterosexual males?

Can we consider the possibility that rather than one obvious mutation in one gene, the combination of more subtle differences is at work? Slightly lower or higher expression of any number of genes, slightly better or worse binding affinities on certain receptors and so on, would have no impact on the overall viability of the affected organism, but may change behaviour.

Also, for evolution to somehow eliminate a particular mutation/behaviour, there needs to be selective pressure. What pressures do humans face that would delete such a hypothetical gene or mutation?

[DrChinese]

Quote:

Originally posted by Drooper

Would not evolutionary theory preclude the existance of genetically caused homosexuality?

No, as already mentioned by others. You are focused on the fact that homosexuals don't reproduce. First, this is not a true statement. Second, the relevant question is "do people which the hypothetical gene repreduce"? which is entirely different.

Further, it is a mistake to confuse "evolutionary advantage" with the actual mechanisms of evolution (random mutation, natural selection) . There is nothing that requires the adaption to be "useful" according to a simple, easily understood and objective criteria. Many - if not most - mutations have no discernible benefit for the species. Obviously, some do.

However, I think the research on the genetic component of homosexuality leaves a lot to be desired. It is a bit hard to get at without a coherent theory of human behavior to work against.

[Denise]

As I asked earlier in the thread, what kind of studies have been done in homosexual non humans? Do they reproduce usually? Why is it that the denser the human population, the higher percentage of homosexuals? Is that true in the animal kingdom as well?

[Fade]

I am not a biologist. In fact, my knowledge of genetics is limited to three years (only) of various courses that are somewhat related to the topic.


I have never, in my entire life, thought 'hey, I want to have sex with men and alienate myself from a large portion of the population'

Not once. It wasn't a choice. So it must be something else.

Quote:

Originally posted by BillHoyt
Straw man. I never said homosexuality in mammals was caused by genetics. I have spoken only to homosexuality in Drosophila and to the various erroneous claims about evolution that have been made here.

Bill, you were replying to my statements about mammalian reproduction. It is not a straw man to say that your statements that something can be biologic without having a direct genetic cause. You have made a statement that I believe to be false. I have not misrepresented your argument.

Quote:

Balderdash. If it is biological, it is genetic, sir. Stop with the lame proclamations and get to marshalling evidence.

Cheers, [/b]

Absolutely, but later. I'm busy but I will try to return to this later today or tomorrow with evidence of how a biological difference can happen without a direct genetic cause in humans, and in a burst of keeping to the subject of the thread, how homosexuality (or come to think of it) heterosexuality arises in humans.

Cheers.

[Shane Costello]

As someone with a growing knowldege of genetics, led me add my tuppence worth.

IMO it's going to be difficult to measure any genetic influence on sexual preference without having a reliable and reproducible measurement of the phenotype, in this case homosexuality. Neither is it likely that there would be a single gay gene, rather a number of genes expressed together would influence sexual preference one way or the other.

Homosexuality has been accepted and practised to varying degrees throughout history. AFAIK it was very prevalent among the ancient Greeks, but that it went hand in glove with heterosexual relationships. I'd imagine that with the advent of Christianity and the role played by the Church in Greek society that homosexuality was frowned upon. It's hard to see how genetics could have influenced this about change.

In some species only a few animals in a colony or wider group assume reproductive duties. Last week's edition of "New Scientist" did a feature on this, and I'll get back to it when I have time.

[a_unique_person]

since humans are social animals, it could well be that we need the 'gays' to perform essential societal functions.

[BillHoyt]

Quote:

Originally posted by Titananarchy
Bill, you were replying to my statements about mammalian reproduction. It is not a straw man to say that your statements that something can be biologic without having a direct genetic cause. You have made a statement that I believe to be false. I have not misrepresented your argument.

I'm afraid you really put the dash in the balder again. Here is the exact exchange of posts:

Quote:

Wrong! Terribly sorry Bill, but there's a gap in your knowledge of mammalian reproduction, and in it is the answer to how homosexuality arises and why it is not related (directly) to genetics.

Quote:

Straw man. I never said homosexuality in mammals was caused by genetics. I have spoken only to homosexuality in Drosophila and to the various erroneous claims about evolution that have been made here.

I repeat again: I have not said homosexuality is caused by genetics. Your statement clearly implies I made a genetic claim about human homosexuality. I have not. I have attempted to shed light on what seems to be a common misconception about how selection works.

And on that point, before we go any further, are we agreed that your claim about lethal genes was in error?

Cheers,

[Dymanic]

Quote:

In some species only a few animals in a colony or wider group assume reproductive duties.

In haplo-diploid species like ants and bees, the non-reproducing members are acting in their best genetic interests by aiding their siblings, to which they are more closely related than they would be to their offspring.
It's not going to help to explain homosexuality in humans.

I'm curious about where this (1994) research ended up:

Quote:

WASHINGTON (AP) -- Two Canadian researchers have found
a link between the number of ridges in fingerprints and male
homosexuality, adding to the theory that sexual orientation is
determined before birth.

Hall JAY, Kimura D.
Dermatoglyphic asymmetry and sexual orientation in men.
Behavioral Neuroscience 1994;
108(6):1203-1206.

These guys evidently studied only male homosexuals. Even if we establish that male homosexuality has a biologicalgenetic cause, I wonder if homosexuality among females will be traceable to the same cause.

[arcticpenguin]

Quote:

Originally posted by Titananarchy

Absolutely, but later. I'm busy but I will try to return to this later today or tomorrow with evidence of how a biological difference can happen without a direct genetic cause in humans, and in a burst of keeping to the subject of the thread, how homosexuality (or come to think of it) heterosexuality arises in humans.

Once again, you have all the answers, but fail to reveal them. Put up or shut up, troll boy.

[BillHoyt]

Quote:

Also, for evolution to somehow eliminate a particular mutation/behaviour, there needs to be selective pressure. What pressures do humans face that would delete such a hypothetical gene or mutation?

There are two parts to the "any homosexual allele should have been eliminated" hypothesis:
o the presumed homosexual allele is recessive
o homosexuals don't reproduce
The errant conclusion is: the allele should have been eliminated.

First of all, the second premise isn't universally true. Secondly, if it were true, it still would not effectively eliminate the homosexual allele. Directional selection would, at best, reduce the homosexual allele frequency to its mutation-selection equilibrium value -- the point at which the rate of new homosexual alleles being introduced by mutation equals the rate at which these alleles are being removed by selection.

Cheers,

Quote:

Originally posted by Denise
Why is it that the denser the human population, the higher percentage of homosexuals?

Hypothesis: it isn't. The percentage of _out_ homosexuals will be higher in a region of denser population. If I'm gay and living somewhere sparsely populated, I'm unlikely to meet out gays very often, I'm unlikely to be part of any gay community. I'm therefore going to be reluctant to come out myself.

On the other hand, if I'm gay and in a major city, I'm going to encounter other gays much more frequently. I'm going to realise that there's a whole gay subculture. Therefore I'm far more likely to have the confidence to come out.

If anyone in this thread is _actually_ gay... comments?