Homosexuality, Nature or Nurture?

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After reading the nurture vs. nature section of the book, I couldn't help but think if homosexuality could be related to either one. I personally feel that homosexuality is not inherited through genes but this article has got me thinking a little. http://www.physorg.com/news84720662.html The article alluded to fruit fly gene alterations that eventually led to homosexuality. I looked up this study and found a good article here  http://www.timesonline.co.uk/tol/news/science/article3025835.ece about how scientists have found a mutation gene known as "gender-blind" or GB. This mutation, which they've found a way of turning on and off, can make flies bisexual! This came as a surprise to me because I have never thought that your genes could play a role in your sexual orientation. Though the implications cannot be directly inferred to humans, it is interesting enough to see that gene mutations in fruit flies can give such information.

I also read an article http://news.softpedia.com/news/Homosexual-by-Birth-41918.shtml which was a bit clearer on the different genes and variables/trends that have been associated with homosexuality. They gave an example of how homosexuality in men increases with the "number of biological older brothers he has, even when he does not grow up with his older male siblings." I found this extremely interesting and it sort of ties into the nature part of homosexuality.The overall message that I got from all three of the articles was that though there are common factors in genes and homosexuality, the larger part of it was up to how the individual grew up, nurture. I also agree with the last article that "it is too early to decide which of our models is most feasible." So what are your opinions about homosexuality and its relations with nature vs. nurture?


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To play devil's advocate -- I believe homosexuality is all nature. Take a look at families who discourage homosexuality -- their kids are just as likely to be gay than anyone else's. The only difference is that those kids might have more trouble coming to terms with that fact due to lack of acceptance from their parents.
I think its possible that homosexuality is evolution's solution to overpopulation. If that on/off gene for homosexuality exists, then why wouldn't nature have turned it on now that humans seem to be, for the most part, outside the realm of natural selection?

As far as the empiricism takes us, there is not much, if anything at all, to suggest homosexuality is "produced" by nurture.

Consider the studies done on male children who were born with deformed genitals—genitals then surgically reconstructed to be female—who were raised as girls without being told, until some point in adulthood, their biological sex. The most crucial time for nurture-development was spent, for these young men, being raised as females. None observed "turned out" to be attracted to men, and some felt deeply tormented about sexual orientation and gender identity while they remained ignorant of their biological sex.

I admit that this argument assumes that the nurturing hypothetically involved in influencing sexual orientation is all related to the gender as which one is treated. There may be more to it.

But this brings me to my next point: we need to be careful so as not to equate gender identity to sexual orientation. The issue is being revealed as more and more complex. There is a correlation between biological sex and sexual orientation (obviously), but we have to wonder about real causation.

It gets even more complex; it's clear that biological sex does not always dictate gender identity.

The fact that this interrelationship of sexual orientation-gender identity-biological sex is likely different for females than it is for males adds even more to contend with. Differences in brain physiology have been observed for all three.

Here is a good article that addresses some of the issue.

One thing that is clear to me is that seems environmental factors play a trivial role at best. I eagerly await more research.

Great discussion here. Homosexuality is such a perfect topic for the nature/nurture debate.. I might even use it in class next time.

I think Eva is correct in that the nurture aspect of homosexuality is lacking empirically. I have not had the time to check out the articles Tou cites here concerning specific gene manipulation changing sexual orientation but it sounds intriguing.

People are much more complex and just as sexuality seems to exist on a kind of continuum rather than hard categories such as gay and straight, gender also has variability if we choose to broaden our definition beyond sexual organs.

This is an very interesting topic. The implications of such a study are potentially huge. If either side is proven, its results could have major effects regarding the view of homosexuality and how it is viewed in society.

While both sides seem to have intriguing and valid points, there was one pressing issue that I have had difficulty coming to grips with. In the article that E. Carrier's posted, the author wrote “Sexual selection defines evolution and creation—such a major player in determining society". Through all my science classes I have taken, I have learned that the primary goal (biological standpoint) is to reproduce as many genes as possible into the next generation. Such explains, why many animals have sexual intercourse with multiple partners. However, an individual with homosexual orientation is incapable to reproduce. Thus from an evolutionary and biological standpoint, why would such a gene be promoted? The only explanation I can have have is that homosexuality is perhaps a mutation. Still, such a mutation would most likely die out to do natural selection of favorable traits. Thus the other alternative explanation is nurturing.

Science continues to grapple with the same question you pose: if the biological end of sex is procreation, and homosexual sex does not lead to procreation, why is homosexuality as prevalent as ever?
There are a good number of theories, but one of the most interesting, to me, is stated in the article I linked:

Possible explanations abound, but an ingenious one was recently put to the test. Perhaps, the theory goes, some genes, when found in men, make them more likely to be gay and when found in women make them more likely to have children. (“Fecund” is the word the researchers use.) The increased number of grandchildren that a parent might have through such a superfertile daughter would offset whatever loss of genetic posterity comes from having a gay son.

It seems clear that researchers are more preoccupied with male homosexuality. I wonder what can be said about female homosexuality with regard to evolution? The same theory, but sexes swapped?

While nurture remains a possible influence, I'm not convinced that the fact a trait is at odds with reproductive success necessarily suggests nurture is the alternative cause. While homosexuality is clearly disadvantageous from a purely evolutionary standpoint to the homosexual individual, genes conferring homosexuality may also confer advantages to other members of the family. Reproduction by these relatives may allow these genes to be passed on collaterally.

I think this is an intersting theory. As you mentioned, It seems to deal well with male homosexuality, however its does not seem to acount for female homosexuality. If this gene is responsible for homosexuality, it would seem that there would be no homosexual females. I can understand why the nurture argument gets a bad rep due to the many variables at hand. It would be very difficult if not impossible to prove on a scientific level alone. However, the role of nurturing can be underestimated. I believe, a twins study would be especially helpful in this case, primarly a study of identical twins. If such a gene was indeed responsble for homosexuality, it would seem that both twins containing this gene would be homosexuals and there would no room for difference regarding sexual orientation between the twins. Otherwise, it would seem that some other factor would have to be involved. Could this factor be nurturing?

Hypothetically, there could be a correlative gene for female homosexuality that, when present in men, lends itself to virility. I don't, however, know of any observations of such a gene. It's been hypothesized that sexual orientation and identity in men is vastly different in dynamics from that in women.

The article addresses your next concern. We can't forget methylation: identical twins have the same DNA, but the activity of their genes isn't necessarily the same. Methylation turns off certain sections of genetic code. So even though we inherit two copies of every gene—one from our mother, one from our father—whether the gene is methylated often determines which of the two genes will be turned on. Methylation is inherited, just as DNA is. But unlike DNA, which has an enzyme that proofreads both the original and the copy to minimize errors, methylation has no built-in checks.

Of course it's possible that nurture and environment is a factor. It undeniably has a role in gene expression. For all we know, nurture may have a hand in determining methylation. What doesn't seem to hold up is the idea of nurture, on a purely learning/conditioning level, being a significant component.

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This page contains a single entry by xiong872 published on October 2, 2011 10:09 PM.

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