Given time, a hash enough environment is going to select for phenotypes despite the quality of the genetic variation. That has to happen or the group dies off [

Given time, a hash enough environment is going to select for phenotypes despite the quality of the genetic variation. That has to happen or the group dies off [1]. That is the point of the phase "I don't think it matters much". I expect a refutation of that statement to be along the lines of, "here is information that shows that the difference in genetic variation between the in Africa and outside of Africa peoples is so big (or the latter have very low variation) that there are marked differences in adaptability to different environments". [1] The reason for extinction may well be very low genetic variation.