Biology + Environment = Gay or Straight

LGBTMost researchers believe that both genetic and environmental factors (biological and social) play a role in forming sexual orientation.

They are not quite sure how it all comes together.

A variety of things point to someone being “more likely” to be gay, but none of the following are determinative:

  • Gay men more often have a counterclockwise hair whorl
  • Lesbians more often have a male pattern “longer ring finger/shorter index finger”
  • Left-handed and ambidextrous folks are more likely to be gay or lesbian
  • Boys with older brothers are more likely to be gay
  • Twin studies suggest genes account for 34% to 50% of the reason why someone is gay

Genes, hormones, brain structure and womb chemistry all seem to play a role.

But maybe it takes a blending of factors to create straight or gay.

Why aren’t identical twins always the same sexual orientation?

I’d like to spend a bit more time discussing why identical twins don’t always share the same sexual orientation.

The blending of factors I just described might play a role. Some researchers have suggested that twins might get a different hormone distribution, depending upon their placement in utero, for instance.

Maybe epigenetics are a factor, too. When twins are born their genes are identical. But over time the environment adds information and affects gene expression, so that twins become less identical with age.

There’s also the question of admitting that you are gay. When twins are separated at birth, one twin might be more likely to admit — to himself or to others —  that he is gay if he were raised in a more liberal home, for instance.

More later.

(Second in a 3-part series on sexual orientation.)

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About BroadBlogs

I have a Ph.D. from UCLA in sociology (emphasis: gender, social psych). I currently teach sociology and women's studies at Foothill College in Los Altos Hills, CA. I have also lectured at San Jose State. And I have blogged for Feminispire, Ms. Magazine, The Good Men Project and Daily Kos. Also been picked up by The Alternet.

Posted on December 4, 2015, in feminism, LGBT+, psychology, sex and sexuality and tagged , , , , , , . Bookmark the permalink. 28 Comments.

  1. While many previous studies have looked into potential genetic drivers of homosexuality, these studies often boasted a significantly smaller sample size or lacked common controls. This is the first study of its kind to boast such a robust sample size and also be published in a scientific peer-reviewed paper.

    • Which studies are you talking about?

      • The study detailed an in-depth analysis of blood and saliva samples taken from 409 pairs of openly gay brothers, including non-identical twins, from 384 families. The only common characteristic shared by all 818 men was being gay.

        Knowing this, the researchers theorized that any single nucleotide polymorphisms (SNPs) consistently found among these men would have something to do with sexual orientation.

  2. Why look for such a thing? Being lesbian, gay, trans or bi is not a disease. People are who they are, that’s all. There is no need to find out causes. Do they want to heal the rainbow people or prevent them from existing?

    • Maybe things are different in France, which is where I believe you are from. But in the United States the more someone believes that being gay has a biological cause, the more likely they are to be accepting of gays. Maybe because then they feel that God made them that way. So finding a biological cause tends to help fight homophobia. And all the research points to a biological cause at base.

      And when a blending of factors is the cause, As appears to be the case, it would be pretty much impossible to “cure” someone of being gay.

      Now, among people who Aren’t homophobic, cause doesn’t really matter. They tend to be fine with gay people regardless of the cause. And that’s where I am. I really don’t care. But other people do and I’m a social researcher, Who has general curiosity, So I write about these things.

  3. More than genetic or left-right inclinations, the environment and social exposure may well be deciding factors. More may be for the researcher and social scientist to unravel…

    • Not sure what you mean by left-right inclinations. Since I’m not sure what you are saying I will add this: I will have to say that even if the environment (biological and sociological) and general social exposure play important roles, it’s not as if someone can *decide* to be gay or straight. For instance, you can’t determine what environmental information enters your genes, and you can’t take it out surgically once it’s there. And there is a “nature-nurture dance” such that nurture affects our biology. But when we end up however we are, we can’t just change it. If you could, there wouldn’t be so many gay people who have tried so hard to change and couldn’t, and who end up committing suicide because they come to hate themselves so much. But thank you for your thoughts.

  4. Interesting! I ever knew about those biological pointers…my ring finger is longer than my index finger 😉 I’ve always enjoyed the company of lesbian women – they seem less full of nonsense than some other women, and I like how they are not beholden to men for anything!

  5. I definitely agree that environment factors can affect sexual orientation. I have a friend, who experienced his mother’s betrayal although his father was really responsible and caring. Then he became homosexual when he was in middle school, which he suffered a lot from due to the conservative and patriarchal society. Sometimes I am also confused about my sexual orientation. Actually I have no idea what love is and I feel “shameful” whenever I picture me being lesbian. But I think there is a potential… as all elder males in my life have betrayed. One of them has hurt my dearest person in the world, my grandmother. Anyway I can’t trust men. I always push them away from me. So we’ll see. Maybe one day, I will find it out.

  6. I find this topic of “biological and environmental factors” role and affect in forming a sexual orientation so interesting. I do think there is a definite correlation in one’s social/cultural environment and their sexual preference. For example, in a culture that is more accepting and open to homosexuality, then someone is more likely to experiment and uncover where they stand on the spectrum of sexuality. But clearly the social aspect can’t be the entire force behind sexuality because of the research done on identical twins. Genetics seem to account for sexuality in some way or another, highlighted in your point that “Twin studies suggest genes account for 34% to 50% of the reason why someone is gay”. I’m really looking forward to the next part of this series.

  7. Religion too can influence sexual orientation. Like in this video, where all straight women are more open while a muslim woman opposed. https://www.youtube.com/watch?v=4Hvaos4qxi8

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