Why Lewontin was wrong about race

Peter Frost explains why Richard Lewontin was wrong when he said that there is more genetic variation within races than between races:

Genes vary much more within than between human populations only if we take one gene at a time. This pattern reverses if we aggregate variation at several gene loci. The more we aggregate, the more this genetic variation will exist between populations and not within them.

This fact was known to Cavalli-Sforza back in 1966 when he was constructing his first phylogenies of human populations: “it is desired that the number of genes considered be as high as possible in order to increase the reliability of the conclusions.” (Cavalli-Sforza 1966). When he and another colleague later aggregated data from 75 gene loci of 144 individuals belonging to 12 human groups in Africa, Asia, Europe, and Oceania, he found very little genetic overlap among the groups. Most individuals clustered with other members of their regional group (Mountain & Cavalli-Sforza 1997). This point has also been made by Mitton (1977, 1978), Edwards (2003), and Sesardic (2010).

Clearly, two groups are easier to tell apart with several criteria than with one. With enough criteria, any overlap will shrink to zero and all individuals can be unambiguously assigned to either group.