Homosexuality Might Develop in the Womb Due to Epigenetic Changes

December 12, 2012

Biology

homosexual-womb

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]

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18 Responses to “Homosexuality Might Develop in the Womb Due to Epigenetic Changes”

  1. jessie Says:

    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$$.

    Reply

    • Mosaic Says:

      My mother is bisexual, my sister is bisexual, I think my brother is closet gay, I’m gay, I have gay cousins on my dad’s side, on my mom’s side, her brother is gay, my cousin is bisexual— let’s be honest here. There is a genetic trend in my family and it is likely this science isn’t meant to “explain” why homosexuality is this or that– it’s just plain facts. How a person twists the facts is another agenda.

      Reply

      • anonymous Says:

        I couldn’t agree more. I’m a fellow homo-sexual. My dad has two sisters each of them have a gay child. His mother’s sister has three daughters one of which has a bi- sexual son, the other daughter has an only child who I know for a fact is gay. However the rest of the family don’t. And the other daughter have two younger girls, one of which is very butch. Time will tell I could be wrong. I tell you an interesting book all if you’ve not read it yet. ‘The evolution of homosexuality’. I can’t help but feel the only time homophobia comes into the picture is when the sons of god or allah are put into the picture. Now don’t call me anti- Islam I beg of you.

        Reply

    • Mandie Says:

      But why is it bad if it is a genetic dysfunction? Seeing as how the whole purpose of sex is reproduction, it very well could be genetic dysfunction. That doesn’t make it wrong or abnormal.

      Reply

  2. Uranium Willy Says:

    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.

    Reply

  3. Emma Says:

    -”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.

    Reply

    • Staff Says:

      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.

      Reply

    • Range Says:

      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.

      Reply

  4. namos Says:

    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.

    Reply

  5. Henry Says:

    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.

    Reply

  6. eddie Says:

    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..

    Reply

    • Mosaic Says:

      Thought-provoking comment…. looking at the situation, spiritually, I used to believe (there’s that tricky word on a science forum) that Homosexuality was Nature/Evolution’s natural population control, which I hypothesized to be a gene mutation that occurs by random to control the population. There is no evidence or basis behind my theory, but one inspired by some classic spiritual poetry.

      Thinking about it, it would make sense as Homosexuality occurs in many species of animals. I for one am a homosexual male and I personally feel elated to know (and believe) that my homosexuality contributes to a natural, effective, harmless, efficient population control.

      Reply

  7. Francisco Culloton Says:

    great article although I’m not sure if i believe this is true – think this is going to take more reading up on.

    Reply

  8. texas holdem strategy Says:

    Its sick that we all the time try to “explain” it.. // analucia

    Reply

  9. Michelle Bastian Says:

    If you’re going to pretend to have a serious and “scientific” discussion regarding what occurs during embryonic, fetal, child, adolescent and adult growth and development and reproductive process (a set of topics already far too lengthy and unwieldy to apply any real science to AT ALL) it may be a good idea to, at the very least, use SCIENTIFIC rather than BIBLICAL language in expressing the “allegedly” scientific conclusions of said discussion.

    Of course as a trained scientist I will NOT call your flimsy mish-mash of tossed about ifs and maybes science OR research, but I will share this one simple fact with you. Post-conception human development takes place, at this point in time, beings in the female UTERUS, not the mystical “womb”. How on earth do you expect people to take anything you say as hard science when you use such archaic and emotive language and base conclusions on suppositions and half-baked conjecture, not true Scientific Method?

    I cannot believe this was even considered seriously, much less published.

    Reply

  10. Madanagopal.V.C Says:

    ‘Barr body’ in the egg of the woman is a dysfunctional X-chromosome,which hides itself in the egg when fertilization takes place as a non-functional one. Okay! But it does not always stays so. If Y chromosome enters the egg it will naturally try to influence it sometimes, either destroying it completely, so that more girl babies would be produced or significantly affect the fertilization with its x-enzymes. The child may develop more testosterone or more estrogen and if it happens with the wrong sex it may become a Gay or Lesbian.Depending on the degree of getting affected the child may become a Gay or Lesbian or an heterosexual when it grows. The case of the ‘Transexuals’ is different since they are XXY chromosome holders where XX expresses the faminine qualities and extra Y gives male organs growth. XXX is completely harmless since they are 100% females and XYY chromosomes are found in some hard criminals.Thus epigenic changes for Gay or Lesbian can be little bit understood as a generation defect rather than labeling them as taboos. Thank You.

    Reply

  11. AxelWolf8745 Says:

    I am the only gay male in my entire family…

    How is that fair?

    Reply

  12. Thoughtful reader Says:

    You can’t deny that it raises some interesting questions. For example, what if turns out that’s its preventable. If you could prevent your child from being gay, would you? I can tell you that any man who has children would want to (I have two), regardless of what they may say in public, nobody wants their children to be gay.

    As a society, we have come to accept homosexuality. The obvious reason being that it does not appear to be something they can control, and most of us agree it is wrong to persecute someone for something that it out of their control, so despite the repulsion so many of us feel, we accept it.

    But again, what if it could be prevented? What f you could take a shot, a vaccine, if you will, and guarantee that you children would be heterosexual. Can you really, truthfully say that you would not?

    I apologize if this has offended anyone, and I do not mean to treat it as a disease, but seriously, putting our usual knee-jerk emotional reaction aside, and look at it objectively.

    If you do answer this, I’d also be curious to know if you’re over 25, and if you have children.

    Reply

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