Overlapping Bell Curves can obscure important differences

Steve Sailer:

Richard Lewontin's argument that there is more genetic variation within racial groups than between them is constantly cited and constantly misinterpreted. You often hear people say that this means that a black man is more genetically similar to a white man than two white men are to each other, which is completely brain-dead. That's not at all what Lewontin meant.

What Lewontin pointed out is that the difference between the averages for two racial groups is often less than the difference between two individuals. As so often with race, it helps in understanding to recast the statement as being about family. Consider two nuclear families, the Shorts and the Longs, each with three adult sons. The Short sons are 5'-4", 5'-8", and 6'-0", while the Long boys are 5'-7", 5'-11", and 6'-3". On average, the Longs are three inches taller than the Shorts, while the standard deviation within each family is 4 inches. So, one of the Shorts is taller than two of the Longs, but overall the Longs are notably taller than the shorts on average. Many of the racial differences we see in the world are roughly similar.

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