Here's why evolution hasn't eliminated homosexuality

@arthwollipot:
There is a very strong correlation of homosexuality in twin and sibling studies, even twins who are separated by birth. This indicates more than just environmental factors in leading to homosexual behavior.

@Dogdoctor:
The pattern of inheritance is believe to be of polymorphic inheritance but there are competing hypotheses. Here are decent reviews of some of the evidence.

http://serendip.brynmawr.edu/exchange/node/1925
http://allpsych.com/journal/homosexuality.html
 
paximperium said:
@arthwollipot:
There is a very strong correlation of homosexuality in twin and sibling studies, even twins who are separated by birth. This indicates more than just environmental factors in leading to homosexual behavior.
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Fair enough, but is there any data about this non-environmental factor being passed between generations? Like for example, the twins' children? Are the parents of the siblings themselves homosexual? What about grandparents?

It strikes me that finding such a pattern would be more difficult, since although it is possible for homosexuals to have children, it is less common. So there would be less data to examine. Also, if you go back more than a generation or two, people would be more likely to conceal any evidence of homosexuality. There really hasn't been enough time to do a proper multigenerational study of the inheritance of homosexuality.
 
paximperium said:
@arthwollipot:
There is a very strong correlation of homosexuality in twin and sibling studies, even twins who are separated by birth. This indicates more than just environmental factors in leading to homosexual behavior.

@Dogdoctor:
The pattern of inheritance is believe to be of polymorphic inheritance but there are competing hypotheses. Here are decent reviews of some of the evidence.

http://serendip.brynmawr.edu/exchange/node/1925
http://allpsych.com/journal/homosexuality.html
Click to expand...

So basically we are clueless unless online blogs constitute scientific evidence?
 
It quite possible for 'accidents of birth' to be non-genetic.

One theory of the cause of homosexuality was stressed births. Supposedly the rate went way up for babies born during the bombing of London. Twins, even if separated, would still suffer from the same birth 'stress'- if that theory holds.

HMmm, I wonder whether the 'separated twins' studies of gayness looked at fraternal vs identical- do identicals, being used to the company of the same sex in the womb, have a higher rate then different sex twins? Gee, that data would show either genetic or 'birth stress', wouldn't it?

'Birth stress', meaning prenatal stress could also account for the birth order prevalence. On older brother in the terrible twos could cause more stress on mommies during the subsequent pregnancy.

So I think I need a tie to a particular gene before I buy the genetic cause theory.

But the crux of the argument is whether gays are that way by choice, or it's inborn. Their fault? NO. But mommies may feel guilty if it's stressed births.
 
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Dogdoctor said:
So basically we are clueless unless online blogs constitute scientific evidence?
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Didn't read those simple reviews did you? Discounting basic reviews based solely on their presented format and not their substance shows how close minded you are about this topic.

Go here:
http://en.wikipedia.org/wiki/Biology_and_sexual_orientation
I disagree with much of what's in this wiki article but its way more well cited than those articles presented. Do your own homework.
 
arthwollipot said:
Fair enough, but is there any data about this non-environmental factor being passed between generations? Like for example, the twins' children? Are the parents of the siblings themselves homosexual? What about grandparents?

It strikes me that finding such a pattern would be more difficult, since although it is possible for homosexuals to have children, it is less common. So there would be less data to examine. Also, if you go back more than a generation or two, people would be more likely to conceal any evidence of homosexuality. There really hasn't been enough time to do a proper multigenerational study of the inheritance of homosexuality.
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I'm not well read up enough on this topic to answer this specific question. There are recent studies, especially on epigenetics, that show that environmental factors can permanently affect genetic expression and that this stress even in the grandparents can affect the expression of these epigenes even in the grandchildren. I don't believe we know enough to determine if homosexuality is a single gene, multigene, etc. inheritance although the evidence points towards some sort of genetic or biologic inheritance.
 
I got badgered into saying "They don't reproduce!" in a high school class when a non-ordained religious type came to talk to us in health class. I realized later one potential flaw in that reasoning; even lethal genes stay in a gene pool if they're recessive. We proved that with a simple random bean-picking experiment in biology class at the same school.

The guy's name was Joe Wilkerson, and it still annoys me that he got me, and that I didn't spot the error till later. Had I reamed him in class, that would have been awesome. It still bothers me that this happened and it was about 20 years ago.
 
I know a few Homosexual men who have reproduced. They married, had kids, the whole nine yards. Keeping there sexual preference a secret.
 
In "Shadows of Forgotten Ancestors," Carl Sagan notes that ape populations in zoos always contain a certain amount of homosexual activity (by hetersexual males), and that the incidence increases as the population density increases. From there, it's a very short logical hop to interpreting homosexuality as a population safety valve (either biological or emotional, or both) which, in turn, would make it a mechanism for species survival. Ultimately, this would mean that homosexuality will never "evolve out" because it's part of how evolution works.
 
Dogdoctor said:
Darwin observed species and made his theory on what he observed. No one is observing genes before trying to set up rules that genes follow.
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Hold on, of course they observe genes when finding out rules that genes follow.
But more importantly, we don't need to observe individual genes. Did mendel observe individual genes when studying peas? No, yet he set up the rules of inheritance that genes follow.
How? Because genes are linked to traits that are observable without actually knowing what particular gene is involved.

They are merely guessing at what they might do.
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No, they are using our current understanding of how evolution by natural selection works to set up a hypothesis, and then try to test it.
Obviously the hypothesis could be wrong, but that's how science works.
Whatever homosexuality is or isn't remains to be discovered. If it is a gene which one(s)? What is the pattern of inheritance? We have no clue. Just guesses.
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Guesses based on a pretty robust theory (natural selection), and guesses which they are attempting to test.

No one is claiming that this is the basis of homosexuality, just that it's possible and worth looking at. What's wrong with that?
 
Beady said:
In "Shadows of Forgotten Ancestors," Carl Sagan notes that ape populations in zoos always contain a certain amount of homosexual activity (by hetersexual males), and that the incidence increases as the population density increases. From there, it's a very short logical hop to interpreting homosexuality as a population safety valve (either biological or emotional, or both) which, in turn, would make it a mechanism for species survival. Ultimately, this would mean that homosexuality will never "evolve out" because it's part of how evolution works.
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Sagan is a hero of mine, but he was an astronomer, not a biologist. I still don't see how this works if we're looking at it as mechanism based on group selection.
On the other hand, if it's kin-selection that we're talking about, I can see it.

It makes sense, for instance, to have fewer children when populations are high, because a higher percentage may live to adulthood in those circumstances.
It might also make sense to have the same number of children, some of whom are homosexual, because they can help to care for the reproductive hetrosexual's offspring, thus sharing resources.

The above noted behavior (in apes) might also simply not be adaptive, but rather a biproduct of stress that wasn't selected for - just something that happens because of the way brains evolved in primates.

Of course, I think it's worthwhile to try to find out which of these (or if none of them, which other possibility) is true.
 
arthwollipot said:
Fair enough, but is there any data about this non-environmental factor being passed between generations? Like for example, the twins' children? Are the parents of the siblings themselves homosexual? What about grandparents?

It strikes me that finding such a pattern would be more difficult, since although it is possible for homosexuals to have children, it is less common. So there would be less data to examine. Also, if you go back more than a generation or two, people would be more likely to conceal any evidence of homosexuality. There really hasn't been enough time to do a proper multigenerational study of the inheritance of homosexuality.
Click to expand...

I remembr reading some years back about some studies suggesting an increase in homosexuality among men on the mothers side of the family (I think it might have specifically looked at maternal uncles). This suggests that the X chromosome may be involved. I'm not sure if the data held up to replication since then, I might go have a look later.
 
Roboramma said:
Hold on, of course they observe genes when finding out rules that genes follow.
But more importantly, we don't need to observe individual genes. Did mendel observe individual genes when studying peas? No, yet he set up the rules of inheritance that genes follow.
Click to expand...

Mendel did not know of genes but suspected something. He observed it directly. He made his analysis from data he colected.
How? Because genes are linked to traits that are observable without actually knowing what particular gene is involved.
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Observing traits does not tell you the genetics involved or the transmission or expression of these traits. You cannot say anything about the the selection of genes involved unless you know at least the specific way that a gene influences the organism.

No, they are using our current understanding of how evolution by natural selection works to set up a hypothesis, and then try to test it.
Obviously the hypothesis could be wrong, but that's how science works.
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They should not be talking about genes if they don't know what genes do. Where is the data to support those views? No science there. It's pure philosophy.

Guesses based on a pretty robust theory (natural selection), and guesses which they are attempting to test.
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Still just guesses.

No one is claiming that this is the basis of homosexuality, just that it's possible and worth looking at. What's wrong with that?
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Nothing but don't pass it for good science it is just guessing.
 
paximperium said:
Didn't read those simple reviews did you? Discounting basic reviews based solely on their presented format and not their substance shows how close minded you are about this topic.

Go here:
http://en.wikipedia.org/wiki/Biology_and_sexual_orientation
I disagree with much of what's in this wiki article but its way more well cited than those articles presented. Do your own homework.
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You cut down on the number I see.
I started reading all of them and realized faults with all of them. The first one you have now, they are trying to say too much about the genetics and build assumption upon assumption. Starting with the genetics for it are from the mother. They ignore that not all male homosexual behavior can be related to the mothers genes. To me this means they are looking at other influences. Such willingness to accept something to be true when they have aknowledged that it is not true seems totally bizarre and inaccurate.

I will wait for when they announce they have discovered all of the gene(s) invovled in homosexuality and know how they work. It will be big news. No need for me to read about endless wild guesses.

eta Just let me add that I have no doubt that genetics are involved in homosexuality. It's just how it is involved is my problem. The only behaviors we can have are those that our genetics allow us to have. But exactly how this influences homosexual behavior remains a mystery. Anyone who thinks they know how genetics influences homosexual behavior does so without good science to substantiate their thoughts. Again I wait for better data.
 
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@Dogdoctor:
Thanks for the clarification. I don't see much that I disagree with that statement.
 
Roboramma said:
Sagan is a hero of mine, but he was an astronomer, not a biologist.
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[Shrug] I notice your sig quotes Asimov, speaking outside the field of his degree. Asimov was a biologist, not a physicist, philosopher or astronomer. I think, with certain intellects, a degree is a jumping-off point, not a definition.

I wonder what a conversation between Asimov and Sagan would have sounded like? Would Sagan, the astronomer, have ignored Asimov, the biologist, as Asimov discussed the Big Bang? Would Asimov have discounted Sagan's thoughts on DNA mutation?

Maybe we should ask Randi. He doesn't have a degree at all, yet knew both men and could hold his own with each.
 
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