Often we hear people argue that that racial classifications are arbitrary, and therefore race does not exist. Actually they say a lot of things, most of which are pretty nebulous, but this point does come up. What if they were right – about racial classifications being arbitrary? I can conceive of a world where that was the case.
In this hypothetical world, human genetic variation is purely clinal. At one end of a long narrow continent, there is one set of gene frequencies, while the gene frequencies at the other end of the continent are significantly different. In between, the gene frequencies vary linearly. For example, if the A and B alleles of a particular gene have frequencies of 90% and 10% at the east end of the continent and frequencies of 20% and 80% at the west end, the frequencies in the middle will be 55% and 45%. Phenotypes also vary continuously. There is no natural divide, no seam, no non-arbitrary way to separate the population into two or more groups. But… that says nothing about how different the east
end and west end populations are. There are clinal species like this where the two end populations can’t even interbreed.
Red-green color blindess might exist in 8% of west-end males and 1% of east-end males. The DRD4 7-R allele might have a frequency of 70% in west-enders and a quarter of a percent in east-enders. A number of alleles that tend to increase height might be more common at one end than the other, such that people at the high end average more than a foot taller. Those kinds of differences certainly exist in humans, although their distribution is not as simple as in this example.
When the inhabitants of this boring parallel world develop better transportation, people will move long distances from their place of origin. We might end up with a colony of east-enders in a west-end metropolis – call it Gotham. The Gothamites think that those east-enders are different – and they’re right. Maybe they’re stiff business competition, maybe they’re dumb and dangerous. Maybe they’re curious and twitchy. Certainly they look different. You can’t say they’re a separate race, in a scientific sense - but what does that matter? The important fact is that the east-enders are biologically different and that the difference has a social impact. Classification issues are irrelevant.
If we dropped a few fusion bombs on the middle of that continent, suddenly there would be a natural seam. In the long run, that interruption of gene flow might have interesting consequences. But in the short run, it wouldn’t make any difference at all. Back in Gotham, the existence or nonexistence of a natural seam between populations has no consequences.