• Question: I read an article recently about sexual orientation in twins (especially identical twins). As an identical twin, I found this very interesting and wondered what your opinions and knowledge was of difference in preferences between people who share genes?

    Asked by lectureattendee to Emma, Ed on 23 Jan 2019.
    • Photo: Edward Morrison

      Edward Morrison answered on 23 Jan 2019:


      This area of science is called “behavioural genetics”. By studying twins and people who were adopted we can try to work out how important genes are in things like our preferences including sexual orientation. Our genes are very important for how we turn out to be.

      The results are very consistent – a good amount (roughly half give or take) of the differences between people are due to their genes. The rest is usually due to the “non-shared environment”. This means things not in the genes that twins do not share e.g. all the idiosyncratic things that happen in life and randomness. It means how your parents raise you is unimportant.

      I recommend a short article called “Three Laws of Behavior Genetics and What They Mean” by Turkheimer for a nice summary of this area.

    • Photo: Emma Meaburn

      Emma Meaburn answered on 28 Jan 2019:


      Interesting question! I do not do any research in this area, but from what I know of the literature there is evidence for a genetic contribution to non-heterosexual behaviour (i.e., genes explain a about 1/3 of the differences we see between people in terms of their sexual orientation). Genes are not the whole story , but seem important.

      There are some big studies currently being performed to find more out about the specific genes involved, such as a study by the Neale lab: http://www.nealelab.is/data/ and https://blog.23andme.com/23andme-research/23andme-studies-the-genetics-of-sexual-orientation/
      These articles would be a good place to start if you wanted to learn a bit more.

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