> even things like allergies and sexualities which one would expect to be more biological in origin.
It doesn't seem to be well-known, but concordance for homosexuality in identical twins is very low (if memory serves, around 40%) compared to concordance for virtually anything else you can measure.
This is pretty unsurprising looking at the biological fundamentals -- a quick naive approach would be to predict "genes will never code for homosexuality, because it is such a crippling failure for the organism" -- but it does tend to undermine the idea that homosexuality is biological in origin.
It doesn't seem to be well-known, but concordance for homosexuality in identical twins is very low (if memory serves, around 40%) compared to concordance for virtually anything else you can measure.
This is pretty unsurprising looking at the biological fundamentals -- a quick naive approach would be to predict "genes will never code for homosexuality, because it is such a crippling failure for the organism" -- but it does tend to undermine the idea that homosexuality is biological in origin.