As another post pointed out, there is good data that if one male identical twin is gay there's a higher than typical chance (20-50%) that the other twin will also be gay.
If there we a "gay gene" we would expect all identical twins to have the same sexuality, so this is strong evidence against a "simple" genetic cause for sexuality.
But the fact that if one identical male twin is gay there's an increased chance that the second twin will be gay suggests genetics are involved somehow.
So the suspicion is that sexuality is linked to epigenetics, basically you can think of epigenetics as the dials and switches which regulate how strongly a gene is "turned on". These switches and dials can be affected by environmental factors, which in the case of sexuality means environmental factors inside the womb during fetal developmemt.
Given identical twins share the same womb at the same time they are exposed to similar environmental factors so it's thought they are more likely to have those dials and switches set in a similar way than non identical twins.
As I understand it (again I hope a real expert will chime in) epigenetics is currently the leading hypothesis for the cause of sexuality, but it's still a bit of a mystery.
flyingkiwisaurus t1_jaih192 wrote
Reply to Am I more likely to be homosexual if I have a homosexual sibling? by rando999555
I hope a true subject matter expert will chime in but as I understand it there is a strong suspicion that sexuality has a lot to do with epigenetics.
As another post pointed out, there is good data that if one male identical twin is gay there's a higher than typical chance (20-50%) that the other twin will also be gay.
If there we a "gay gene" we would expect all identical twins to have the same sexuality, so this is strong evidence against a "simple" genetic cause for sexuality.
But the fact that if one identical male twin is gay there's an increased chance that the second twin will be gay suggests genetics are involved somehow.
So the suspicion is that sexuality is linked to epigenetics, basically you can think of epigenetics as the dials and switches which regulate how strongly a gene is "turned on". These switches and dials can be affected by environmental factors, which in the case of sexuality means environmental factors inside the womb during fetal developmemt.
Given identical twins share the same womb at the same time they are exposed to similar environmental factors so it's thought they are more likely to have those dials and switches set in a similar way than non identical twins.
As I understand it (again I hope a real expert will chime in) epigenetics is currently the leading hypothesis for the cause of sexuality, but it's still a bit of a mystery.