How does evolution explain homosexuality?

[Valjean]

I don't agree. I think that a genetic basis to homosexuality is plausible.

Not only plausable, homosexuality can be identified with certain brain scans. There are identifiable, morphological differences.
I'm not saying all homosexuality is innate, as attractiveness clearly has a strong cultural component.

In re: the OP, I supect innate homosexuality to be the product of small variations in brain structure, easily within the range of normal prenatal development. Inasmuch as the resulting trait does not seriously handicap the species, it is no pressure to select it out.

 

[Francine]

Not only plausable, homosexuality can be identified with certain brain scans.

You should tell the Army, so they can scan people before they sign up.

 

[9-10ths_Penguin]

It seems to me that homosexuality has simply ALWAYS existed and is not genetic. I think this was the point I was trying to make. Everyone's arguments seem to agree with this too.

Not mine, IMO. I tried to make the point that it's quite plausible that homosexuality is genetic, and that there's a very well-defined mechanism that would allow this to occur.

On top of this (though not mentioned by me in this thread) is the strong evidence that points to sexual orientation being set by birth, which would only leave two possible causes: genetics and prenatal environment.

 

[Autodidact]

I think that tomspug raises a valid and puzzling question. (Although I think he should have the integrity and humility to admit he was wrong elsewhere before he has the temerity to challenge anyone else.)

The problem is puzzling because homosexuality is obviously counter-reproductive. It is not that homosexuals don't reproduce--I myself have 3 children--but that the more homosexual one is, the less likely to reproduce. Therefore it is puzzling how this trait has survived, if you accept evolutionary psychology.

I think the answer requires a more sophisticated evolutionary approach. One possibility that has been looked at is "group selection", that is, that having homosexuals in a tribe or family benefits offspring in that group, but for complicated reasons I don't think that works.

First, you start from the premise that the answer is likely to be completely different for men than for women. Why? Because the difference between men and women is sex. There is no reason to assume that the answer would be the same for both.

Let's take men first. One strong possibility is that homosexuality is in effect vestigial in men, like nipples. What? Well, one study indicates that the mothers and sisters of homosexual men have more offspring than than those that don't. So this raises the possibility of a gene that benefits women. If this gene happened to be on the X chromosome, then a male could inherit it, and turn out gay. In this way the gene would persist, through the female relatives of gay men. Since homosexuality is relatively rare, occurring in only around 4% of the male population, I think this is an intriguing direction to look.

As for women, I have a long but I think correct explanation, but alas no time for it right now. If you're interested I'll lay it out.

 

[logician]

I think that tomspug raises a valid and puzzling question. (Although I think he should have the integrity and humility to admit he was wrong elsewhere before he has the temerity to challenge anyone else.)

The problem is puzzling because homosexuality is obviously counter-reproductive. It is not that homosexuals don't reproduce--I myself have 3 children--but that the more homosexual one is, the less likely to reproduce. Therefore it is puzzling how this trait has survived, if you accept evolutionary psychology.

I think the answer requires a more sophisticated evolutionary approach. One possibility that has been looked at is "group selection", that is, that having homosexuals in a tribe or family benefits offspring in that group, but for complicated reasons I don't think that works.

First, you start from the premise that the answer is likely to be completely different for men than for women. Why? Because the difference between men and women is sex. There is no reason to assume that the answer would be the same for both.

Let's take men first. One strong possibility is that homosexuality is in effect vestigial in men, like nipples. What? Well, one study indicates that the mothers and sisters of homosexual men have more offspring than than those that don't. So this raises the possibility of a gene that benefits women. If this gene happened to be on the X chromosome, then a male could inherit it, and turn out gay. In this way the gene would persist, through the female relatives of gay men. Since homosexuality is relatively rare, occurring in only around 4% of the male population, I think this is an intriguing direction to look.

As for women, I have a long but I think correct explanation, but alas no time for it right now. If you're interested I'll lay it out.

With the population explosion, there is no pressure to reproduce, so the incidence of homosexuality on that basis at least would tend to rise.

 

[Autodidact]

With the population explosion, there is no pressure to reproduce, so the incidence of homosexuality on that basis at least would tend to rise.

No, I don't think this is right. It's not about pressure to reproduce, it's just axiomatic that traits that don't get reproduced die out.

 

[Valjean]

I think that tomspug raises a valid and puzzling question. (Although I think he should have the integrity and humility to admit he was wrong elsewhere before he has the temerity to challenge anyone else.)

The problem is puzzling because homosexuality is obviously counter-reproductive. It is not that homosexuals don't reproduce--I myself have 3 children--but that the more homosexual one is, the less likely to reproduce. Therefore it is puzzling how this trait has survived, if you accept evolutionary psychology.

Lots of "counter reproductive" traits exist in many species. Animals are not that finely honed. Good enough frequently works fine.
Keep in mind that homosexuality has been observed throughout the animal kingdom.

I think the answer requires a more sophisticated evolutionary approach. One possibility that has been looked at is "group selection", that is, that having homosexuals in a tribe or family benefits offspring in that group, but for complicated reasons I don't think that works.

I don't think the answer is "evolutionary" at all. It is a simple genetic anomaly, like albinism, red hair or left handednes. It doe not seriously detract from the reproductive succes of the species, so is not selected out.

First, you start from the premise that the answer is likely to be completely different for men than for women. Why? Because the difference between men and women is sex. There is no reason to assume that the answer would be the same for both.

I don't follow your reasoning here...Let's take men first. One strong possibility is that homosexuality is in effect vestigial in men, like nipples. What? Well, one study indicates that the mothers and sisters of homosexual men have more offspring than than those that don't. So this raises the possibility of a gene that benefits women. If this gene happened to be on the X chromosome, then a male could inherit it, and turn out gay. In this way the gene would persist, through the female relatives of gay men. Since homosexuality is relatively rare, occurring in only around 4% of the male population, I think this is an intriguing direction to look.

As for women, I have a long but I think correct explanation, but alas no time for it right now. If you're interested I'll lay it out.[/quote]

 

[crystalonyx]

No, I don't think this is right. It's not about pressure to reproduce, it's just axiomatic that traits that don't get reproduced die out.

Then the increasing incidence of it in our socienty indicates it is not particularly a genetic trait, but more a choice.

 

[9-10ths_Penguin]

Then the increasing incidence of it in our socienty indicates it is not particularly a genetic trait, but more a choice.

Has the incidence of homosexuality been increasing?

It's hard to tell - increased societal acceptance of homosexuality means a smaller percentage living in the closet. This effect would cause the proportion of people who are identified as homosexual to increase over time in any way you could measure. Regardless of whether the incidence of homosexuality is going up, down or staying the same, you'll have more homosexual people being open about their orientation. How do you factor this out?

 

[Francine]

Then the increasing incidence of it in our socienty indicates it is not particularly a genetic trait, but more a choice.

The incidence remains constant, but they are starting to make movies and shows about it (The L Word, Bareback Mountain).

 

[Fluffy]

1) There is a common misconception that natural selection selects for individuals. Actually, natural selection selects for genes. Why is this important?

Consider animal a who has gene set A and animal b who has gene set B.
These animals mate and produce 10 offspring, each called ab, who each have a different combination of the gene sets A and B, called AB.
The first of the second generation, ab1, mates with animal c who has gene set C.
Their 10 offspring are each called abc and have varying gene sets ABC.

Now assume that the specific combination of A and B, AB1, found in animal ab is the most advantageous combination out of all 10 existent combinations. The children of ab1 and c will then have a more advantageous gene set than the children of ab1's siblings. These children will survive whilst the others won't meaning that gene set AB1 will continue whilst the others will become extinct.

However, there is still competition between these gene sets even though AB1 will become victorious. If the gene sets of the other combinations support AB1 instead of competing with it then AB1 would become even more advantageous.

If you look at the example of hive animals, say an ants, this is exactly what happens. The queen ant is the only fertile female so any descendants will be sure to have her gene set. The vast majority of the ants are infertile and support the colony, and especially the queen, to ensure the survival of this one gene set. Their own gene sets will become extinct but that is irrelevant because the most advantageous gene set is held by the queen.

2) Animals simply aren't as good at determining sex as we are and don't have any of the hang ups that we have either. Clearly an animal that has sex with anything and an animal that is picky over determining gender will have a survival advantage.

Farmers put coloured chalk on the underside of their rams during mating season with each ram having a different colour. When the rams have sex with the ewes, they leave a coloured mark on the wool on the ewes back. The farmers use this to tell which ewes have been impregnated because the rams are able to tell when a ewe has been fertilised. If a ewe has got 1 colour on her back then she is likely to have conceived but if she has many colours then she might be infertile.

However, the rams can't tell the difference between male and female and so each ram ends up with every colour on their back as they cannot, obviously, be fertilised. This doesn't make them homosexual and it frustrates me immensely when gay advocates point to similar so-called homosexual incidents. They will just have sex with anything. That is clearly distinct from homosexuality in humans.

 

[Smoke]

However, the rams can't tell the difference between male and female and so each ram ends up with every colour on their back as they cannot, obviously, be fertilised. This doesn't make them homosexual and it frustrates me immensely when gay advocates point to similar so-called homosexual incidents. They will just have sex with anything. That is clearly distinct from homosexuality in humans.

You find it easier to believe that rams can't tell males from females than to believe that rams are often bisexual?

 

[tomspug]

You find it easier to believe that rams can't tell males from females than to believe that rams are often bisexual?

I'm pretty sure that animals can tell differences in gender better than we can. Although animals seem to have a much harder problem controlling their lebido than we do. Heck, dogs will hump anything if they're in the mood.

 

[Autodidact]

Lots of "counter reproductive" traits exist in many species. Animals are not that finely honed. Good enough frequently works fine.
Keep in mind that homosexuality has been observed throughout the animal kingdom.



I don't think the answer is "evolutionary" at all. It is a simple genetic anomaly, like albinism, red hair or left handednes. It doe not seriously detract from the reproductive succes of the species, so is not selected out.

Possibly, but the difference is that it is actually counter-reproductive, which of course left-handedness is not.

I don't follow your reasoning here..

It's possible that the explanation may be the same for men and women, but unlikely, and no reason to assume this. As I said, the difference between men and women is sex, and sex is (evolutionarily speaking) reproduction. So there is no reason to assume that any evolutionary or genetic explanation for homosexuality will be the same for the two different "sides" of the reproductive equation.

 

[Autodidact]

Then the increasing incidence of it in our socienty indicates it is not particularly a genetic trait, but more a choice.

What makes you think there is an increasing incidence of homosexuality? On the contrary, the fact that homosexuality has always been practiced by a minority of the population in all times and all cultures tends to indicate a biological basis.

 

[doppelganger]

I'm pretty sure that animals can tell differences in gender better than we can.

Actually, non-human animals are conspicuously weak when it comes to the formal rules of grammar.

 

[tomspug]

Actually, non-human animals are conspicuously weak when it comes to the formal rules of grammar.

Okay...

EDIT: ANIMALS CAN TELL BODY PARTS BETTER THAN WE CAN.

Happy?

 

[doppelganger]

Happy?

I was happy before . . . :yes:

 

[crystalonyx]

Has the incidence of homosexuality been increasing?

?

I would say yes, precisely because it is more accepted. Remember, we're talking incidence here, not some percentage of people who might have leanings that direction but can't act on them, which has been the case throughout history until now.

 

[Autodidact]

I would say yes, precisely because it is more accepted. Remember, we're talking incidence here, not some percentage of people who might have leanings that direction but can't act on them, which has been the case throughout history until now.

Well I realize that's your assumption, but the question is, is there any reality to it? For example, do you have any evidence, studies, statistics, to back up your assertion?

In any case, since homosexuality is a good thing, this argument would speak in general of greater acceptance of it, if true.

Nevertheless, frankly I doubt it.