How to Be Different
20th December 2017
Lewontin argued that there is more genetic variation within human populations than between them, so they can’t really be very different. Of course that’s bullshit: humans have the second-largest morphological variation of any mammal, behind only dogs. How do you get significant phenotypic differences between populations when there isn’t much Fst between them?
One way (at the extreme) is to have a single allele, one that does a lot, vary strongly between populations: at the limit, be fixed in one and nonexistent in the other. There are not a lot of alleles like this in humans, but it happens. EDAR 370A is almost fixed in Northeast Asia, almost nonexistent in Europe and Africa: it results in thicker scalp hair, more numerous sweat glands, smaller breasts, funny teeth, and changes in the shape of the ears and chin. Just one allele: it would not show up noticeably in Fst.