Well, some alleles (genes) cluster among populations, and many people believe that statistically different genetic populations equates to different races. It's

Well, some alleles (genes) cluster among populations, and many people believe that statistically different genetic populations equates to different races. It's a widespread mistaken belief that has no scientific basis, because having different races requires 100% isolation of the populations. There are many horrible things that have happened in the world on the basis of this belief, and it irritates me when people propagate it, even if they aren't doing so maliciously. Note that I realize now I may have been quoting him out of context about the physical differences, kind of hard to tell. Okay, based on recent comment, apparently a total misunderstanding.