Fire and Knowledge

The distinctions that we conventionally use to divide the species into races—skin color, hair, and the shape of faces—are controlled only by a few genes. The vast majority of variable genes do not respect so-called racial boundaries. There is far more variation within any given population of humans than between populations. If all the humans on earth were wiped out except a single tribe in a remote New Guinea valley, the survivors would still preserve 85 percent of the genetic variability of our entire species.

–Carl Zimmer, Evolution: The Triumph of an Idea, pp. 81-82