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Homosexuality and Evolution

Marc L

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Marc L
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Dec 13, 2005
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Let me say right at the beginning that I am not homophobic. Far from it, in fact.

This question comes up from reading The God Delusion by Richard Dawkins recently. In it, he puts forth the hypothesis that a tendency for religion developed from an evolutionary need. He suggests that young children need to be able to obey without question to avoid danger, and that religion was a side effect of this. Now, it's been a couple of weeks since I returned the book to the library, so I may have his theory completely wrong, but that's the gist of it.

For whatever reason, one day while standing watch, I was considering evolution and homosexuality. Obviously, from a purely sexual standpoint, homosexuality is detrimental to the survival of the species. If you have no desire to have sex with the opposite gender, you won't procreate. Since homosexual behavior has been observed in non-human animals, it doesn't make sense that it's just a lifestyle choice, but must be genetic. So I was standing there thinking about why homosexuality would have developed.

First, I thought, maybe it was a form of population control. If the population gets too big, then having a portion of your population not want to have sex with the opposite gender will slow the birth rate down. Given that our population is still growing, however, this doesn't make sense to me.

Have there ever been any studies that have seriously attempted to discover why homosexuality develops? Are there any valid ideas (as opposed to inherent sinfulness, poor genetics, etc)?

Let me close by again stating that I'm not slamming homosexuals. People responding that I am, or trying to flame me will be ignored.

Marc
 
Marc L said:
For whatever reason, one day while standing watch, I was considering evolution and homosexuality. Obviously, from a purely sexual standpoint, homosexuality is detrimental to the survival of the species. If you have no desire to have sex with the opposite gender, you won't procreate. Since homosexual behavior has been observed in non-human animals, it doesn't make sense that it's just a lifestyle choice, but must be genetic. So I was standing there thinking about why homosexuality would have developed.
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It may be like the Grandmother Effect. Without children of their own, they may be around to invest more care into their siblings' children. Since they share genes with their nieces and nephews, this could lead to selection for the gene.

First, I thought, maybe it was a form of population control. If the population gets too big, then having a portion of your population not want to have sex with the opposite gender will slow the birth rate down. Given that our population is still growing, however, this doesn't make sense to me.
Click to expand...

The fraternal birth order has an effect on the chance of being gay - the more older brothers that you have, the more likely you are to be gay. Maybe it's a natural way to limit the use of scarce resources (fewer grandchildren) and improve longevity?

Have there ever been any studies that have seriously attempted to discover why homosexuality develops? Are there any valid ideas (as opposed to inherent sinfulness, poor genetics, etc)?
Click to expand...

I think it's one of those areas where lots of people like to speculate. I don't know off-hand who has done a good job of it.

Linda
 
What if it's a recessive gene like sickle cell anemia. There is some evidence to support that having a single of the sickle cell genes protects you from malaria, having two is deadly. Even though this means you have a 25% chance of your children dying young, you have a 50% chance that you have resistance to blood diseases. Perhaps a single gay gene offers something like an enhanced sex drive, but two causes you to be gay.
 
It may be that gayness in some percentage of the population is an inevitable side-effect of something that is highly adaptive (like pair-bonding, for instance).
 
Sexual attraction is an odd thing that is clearly partly learned. Heterosexual fetishes are common and range from the dull to the bizarre to sadistic. It seems logical that the process by which our sexual peculiarities are formed may not be perfect in leading us to behavior that leads to reproduction.

My guess is that homosexuality is the combination of a particular genetic component and environment. Probably not an evolutionary advantage, just a consequence of an instinct that is hard coded, yet must allow for a wide variety in the appearance of potential mates.
 
Homosexuality does not have to be evolutionarily advantagious to survive in a species. All it has to be is not strongly genetic and not disadvantagious. If it is caused by the level of hormores the fetus is exposed to and if mothers whose wombs provide an imbalance of hormones to one child also provide the correct hormones to one who will procreate, homosexuality will not breed out.

I see no need to look for some perfect fit in the scheme of human survival. It exists, nobody dies from it (ideally), next topic.
 
Indeed, there's a few threads on this topic back through the archives.

Terry's opinion is closest to my own. Homosexuality does not necessarily have to be due to a discrete selection of genes, but rather the interaction of a number of genes that in the past have been of advantage.

Sex is not only about reproduction, especially amongst complex organisms. It can be about dominance and social bonding. Males who have homosexual traits might in the past have been better at bonding with other members of their social group.

To reduce it down to a 'single gene' trait, or a single phenotype result, is to miss whole chunks of the big picture.

Athon
 
athon said:
Indeed, there's a few threads on this topic back through the archives.

Terry's opinion is closest to my own. Homosexuality does not necessarily have to be due to a discrete selection of genes, but rather the interaction of a number of genes that in the past have been of advantage.

Sex is not only about reproduction, especially amongst complex organisms. It can be about dominance and social bonding. Males who have homosexual traits might in the past have been better at bonding with other members of their social group.

To reduce it down to a 'single gene' trait, or a single phenotype result, is to miss whole chunks of the big picture.

Athon
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Yes quite so. You should be aware of my own work, described in my web site "Sex and Philosophy." So far as I know it is the only extended attempt to account for the general pattern of human sexuality.

You should also know that humans seem to be the only species that seem to throw up a significant number of individuals who are exclusively homosexual, rather than displaying homosexual behaviour as part of a more bisexual overall pattern.
 
Not everything is genetic- as Loss Leader mentioned. Studies show it has a lot to do with what hormones You might as well ask why cancer developed- while it has no advantages for evolution, it just springs up as the result of natural biological processes (I'm NOT comparing homosexuality to a disease, or to a mistake, or anything- I'm comparing it to a biological event. Seriously, not homophobic).
 
athon said:
Indeed, there's a few threads on this topic back through the archives.

Terry's opinion is closest to my own. Homosexuality does not necessarily have to be due to a discrete selection of genes, but rather the interaction of a number of genes that in the past have been of advantage.

Sex is not only about reproduction, especially amongst complex organisms. It can be about dominance and social bonding. Males who have homosexual traits might in the past have been better at bonding with other members of their social group.

To reduce it down to a 'single gene' trait, or a single phenotype result, is to miss whole chunks of the big picture.

Athon
Click to expand...

Seconding this, sexual attraction is complex. Every male has all of the genes that make a female female, including the ones that make females be attracted to a variety of male characteristics. Vice versa females have a lot of the genes that make males male, including the ones that make them be attracted to a variety of female characteristics. I find it easy to believe that this machinery would be complex and trouble-prone. Particularly since many minor failures are not strongly selected against - it is only a combination of failures that will result in homosexuality.

Cheers,
Ben
 
Thanks all, I appreciate the answers and links. John, I will check out your website as well.

Marc
 
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