Credit: Shutterstock/Anton Gvozdikov; University of California.
According to a newly released hypothesis, homosexuality might not lie in DNA itself. Instead, as an embryo develops, sex-related genes are turned on and off in response to fluctuating levels of hormones in the womb, produced by both mother and child. This benefits the unborn child, however if these epigenetic changes persist once the child is born, and has children of its own, some of these offspring may be homosexual.
The scientists published their findings in the journal The Quarterly Review of Biology. Evolutionary geneticists propose that this is the reason why homosexuality didn’t fade away due to evolutionary pressure. Current research estimates that 8% of the population is gay, and it has been known that homosexuality can run in families. If one of a set of identical twins is gay, there’s a 20% chance that the other will be, too.
Homosexuality isn’t just tied to the human species. There are many species exhibiting homosexual traits, including fish and birds, and geneticists have not been able to find a gene that is responsible for sexual orientation.
Testosterone doesn’t explain everything. Female fetuses are exposed to small amounts of testosterone from their adrenal glands, the placenta and the mother’s endocrine system. At many key points of gestation, male and female fetuses are exposed to similar amounts of testosterone. Levels of the hormone can be higher than normal in females and lower than expected in males without any effects on genital or brain structures.
The authors propose that the differences in sensitivity to sex hormones result in epigenetic changes, which don’t affect the structure of a gene, but can be activated by chemically altering a gene’s promoter region. Epigenetic changes could enhance or blunt testosterone’s activity as needed.
Epigenetic changes involve alterations in the proteins that bind together long strands of DNA and can be handed down to offspring. The authors propose that homosexuality may be a carry-over from one’s parents’ own prenatal genes to resist excess testosterone, and this could alter the gene activation in areas of the child’s brain involved in sexual attraction and preference. This could explain why homosexuality persists throughout evolution, state the authors.
Going from changes in gene expression to why someone is attracted to a person of the same sex is probably a question for which science may never find the answer, states Marlene Zuk, an evolutionary biologist at the University of Minnesota, Twin Cities.
[via ScienceNOW]
December 12, 2012 at 10:19 am
This is all sorts of messed up. Why is it that we are trying to “explain” it?
So now if you’re gay its your moms fault and it’s a genetic disfunction. Unify the people my a$$.
December 12, 2012 at 6:00 pm
Explaining it doesn’t say anything about whether its wrong or right. There are explanations for lots of differences in humans and we don’t then say therefore that difference is wrong. Its interesting to know about the factors that add up to make us who we are.
December 13, 2012 at 1:15 am
-”Current research estimates that 8% of the population is gay, and it has been known that homosexuality can run in families.”
What research? Where’s the link to that? Homosexuality “runs in families” that are willing to accept and love their son and daughter no matter who they love, not hid and deny it, especially to researchers.
The article also states “homosexuality might not lie in DNA itself” – Wheres the articles that says it does? Theres no solid proof on the origins of homosexuality and is generally accepted as a fact about most species of animal. This article is contradictory, assumptive, speculative and poorly written at best.
December 13, 2012 at 6:53 am
The study, which you can link to from the article, explains where the researchers got their information.
The study: “Homosexuality as a Consequence of Epigenetically Canalized Sexual Development,” William R. Rice, Urban Friberg, and Sergey Gavrilets, The Quarterly Review of Biology
“Might not lie in the DNA itself” means in the DNA and in something else.
December 17, 2012 at 5:40 am
The source article has all of the right sources, if you care to read up on them. You can find them here
http://news.sciencemag.org/sciencenow/2012/12/homosexuality-may-start-in-the-w.html
or the article cited by our Staff. This article is about the possibility that epigenetic changes could affect the sexual preference of offspring. It has to do with the science, not with the moral dilemmas that stem from this.
December 13, 2012 at 10:45 am
Or it cold be that its just a natural part of human sexual expression, and cultural pressures prevent it from being more openly accepted. In animals the behavior is pretty common. Twins are more likely to WANT to mimick each other, so the fact that both are more likely to be gay if one is doesn’t necessarily co-oberate this weak study.
February 22, 2013 at 5:37 pm
Now there is a new type of testing known as autosomal testing, which relies on the other 22 chromosomes, the ones that are not the sex chromosomes.
April 14, 2013 at 3:24 pm
Over the last 45 years I have noticed a huge increase in the number of Homosexuals and have wondered why their has been such a huge increase between the 70′s and the 90′s. I believed in College in 1972, for which I was verbally abused by my Micro Instructor, that their had to be a Mutation of some sort going in the womb. This is the same Micro Instructor who I had a go around with the previous year about the effects of Partially Hydrogenated fats reacting exactly the same in Cholestrol Lab tests. So my question now is what external substance or life style, is creating the mutations in the womb. Since man I believe is primarily primed to be Hetrosexual for the main purpose of the survival of the species, then homosexuality has to be a mutantion happening in the womb also evidenced by “manish” women and Feminie Men. Is the increase use of illegal drugs by the female populace, or the increased use of Alcohol, or Pesticides in the food chain or even Corn Syrup or food perservatives and additives, antibiotics in growth hormones in Beef and Dairy Products? I do see a marked differnce in the children produced by Vegans, in my observation of only a few couples, the children tend to be more afraid or less agressive which would have been a huge negative a few thousand years ago when warring tribes were almost the norm. So it would be interesting to see a concerted effort to try and find the cause for the mutations within the womb. And no, I am not an expert who has been taught to think in the box, to be accepted by such low lifes as my former College Professors whose huge Egos were threatened by anyone like myself thinking out side of the box..And still do..