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Another genetics theory

Timothy Kincaid

December 11th, 2012

It seems that you have epi-marks on your genes. And those epi-marks control how your genes operate. And while they are not supposed to be passed on to your kids, sometimes they are.

And that’s why you’re gay. Or something. (USNews)

Long thought to have some sort of hereditary link, a group of scientists suggested Tuesday that homosexuality is linked to epi-marks — extra layers of information that control how certain genes are expressed. These epi-marks are usually, but not always, “erased” between generations. In homosexuals, these epi-marks aren’t erased — they’re passed from father-to-daughter or mother-to-son, explains William Rice, an evolutionary biologist at the University of California Santa Barbara and lead author of the study.

Rice and his team created a mathematical model that explains why homosexuality is passed through epi-marks, not genetics. Evolutionarily speaking, if homosexuality was solely a genetic trait, scientists would expect the trait to eventually disappear because homosexuals wouldn’t be expected to reproduce. But because these epi-marks provide an evolutionary advantage for the parents of homosexuals: They protect fathers of homosexuals from underexposure to testosterone and mothers of homosexuals from overexposure to testosterone while they are in gestation.

This is all a theoretical model which has yet to be tested by studies. But it undoubtedly will. And if it proves out, this could be the end of the “choice” debate – and also may prove to be an unhandy response to those who might be tempted to eugenically control for orientation.

Meanwhile, I’m sticking with my old standby theory: orientation is caused by Gerber’s Strained Peas. And as no one has yet proven me wrong, I’ll just sit here and smirk.



December 11th, 2012 | LINK

I disagree with your theory VEHEMENTLY. It was caused by cod liver oil, dosed to us kids of the 60’s.

December 11th, 2012 | LINK

Boiled okra.

Priya Lynn
December 11th, 2012 | LINK

There are other plausible explanations as to how gayness can be genetic and still passed on from generation to generation regardless of whether or not gays reproduce.

December 11th, 2012 | LINK

Interesting theory, if it pans out. I do love your eternal optimism as always, Timothy. “This could be the end of the ‘choice’ debate”.
We still have people who think the earth is 6000 years old and evolution is “just a theory” and global warming is a hoax. Nothing will ever end the “choice” debate. But it will be interesting for those of us who aren’t anti-science, nonetheless.

Lynn David
December 12th, 2012 | LINK

A hypothesis is that which gets tested and as factual evidence is found backing that hypothesis is then developed into a theory. So to say this is a theory is jumping the gun.

It is a hypothetical model:
But one which has efficacy based in their work on a model: “In the current study, researchers from the Working Group on Intragenomic Conflict at the National Institute for Mathematical and Biological Synthesis (NIMBioS) integrated evolutionary theory with recent advances in the molecular regulation of gene expression and androgen-dependent sexual development to produce a biological and mathematical model that delineates the role of epigenetics in homosexuality.”

December 12th, 2012 | LINK

Distinguishing ‘epi-marks’ from actual genetics is a stretch. I thought we were long past believing in one ‘gay gene’. As PL points out, there is sufficient room for actual genes (alleles of actual genes, to be precise) to play beneficial roles in reproduction and still guide the mind and body towards homosexuality. In fact, given the complexity of reproductive fitness (since it includes traits from one’s physical form and well being, to one’s ability to produce healthy and effective gametes) it makes sense that a great variety of genes could fit such a role, and have an additive effect (that could also explain the variation we see in orientation, i.e. the Kinsey scale). Indeed, it is not uncommon for certain alleles to confer a benefit in one regard while providing a ‘detriment’ in another; it is the weight of benefit to detriment that determines the success of the allele. If all of this is true, it would make sense that epigenetic markers controlling the expression of such genes (or their varying alleles) could play a role in influencing one’s orientation. These ideas are not mutually exclusive, and to suggest otherwise is hardly scientific.

I do, however, feel that this is an effort to find some way of ‘curing’ or preventing gay children from being born. A gene is hard to change, but epigenetic markers can be more easily altered, though not without a great deal of risk. We are fatalistic about our genetic sequences, but we are cool with trying to influence the outcome of, or even change, other, equally deterministic factors that influence our biology. Whatever the causes of homosexuality, hormones, ‘epi-markers’ or genetic sequences (and most likely a combination of all three, as well as other factors), one’s orientation should not matter.

Ryan, may I encourage you to use the term ‘hypothesis’ when discussing ideas like the one above. We allow our opponents to continue their scientific ignorance when we use scientific terminology on their terms. As LD pointed out, hypothesis and theory are distinct, but our culture has confused them, and ‘theory’ has been adopted in our lexicon as a general term for any idea, no matter how scientific or how proven. If we can begin to use these terms properly, I believe we can reclaim scientific debate.

December 12th, 2012 | LINK

You’re right, Nathaniel. Obviously there is “scientific theory” and layman’s theory which is just speculation, and the two are very different things. I should have made it clearer when talking about a science-related issue.

Timothy Kincaid
December 12th, 2012 | LINK

Lynn David,

I’m not a scientist, so forgive my terminology errors.

I agree that this is a hypothesis, not a theory. It is a proposed explanation, but it has not been tested or accepted.

However, once a hypothesis has been proposed and is considered for testing, does it not then become a theoretical model? Would not a hypothetical model be the basis on which a hypothesis was worked out and once it was formalized it would then be beyond the hypothetical model?

I’m happy to use the correct language (though I have been known to use “theory” when I meant hypothesis) but I’m not sure about the exact border of “model”. And google and wikipedia are pretty useless for language that is generally misused.

December 12th, 2012 | LINK

This might be a really stupid question, but, given the discussion on this blog regarding the difficulties counting the LGB population, i am curious as to how these studies define and find gay persons? Are there brain scans or do they just have people self report?

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