While we’re on the topic of the scientific merits and demerits of this discussion of inbreeding, here’s a point that seems to have escaped Mr. Fischer: although inbreeding is bad for the kids, it’s not bad for the gene pool. Talk about the `damage done to the gene pool’ by this practice is at best ignorant prattle, and more likely, sheer demagoguery.

What happens with inbreeding is that some of the genes from the genetic load, a collection of damaged genes that rattle around inside all of us, is more likely to be expressed.

Harmful genetic errors that are recessive can just sit there, almost never expressed, because they almost always get paired with a dominant allele that works just fine. The allure of the exotic is nature’s way of reminding us of that, when we go to pick a mate.

With inbreeding, the mated pair share a dangerously high fraction of their genes. If both partners carry the damaged allele, and if that’s the one that makes it into the egg and into the lucky sperm, the kid is unlucky.

The incidence of the harmful allele in the population, though, goes down when the kid is too badly damaged to survive or breed. That’s right, inbreeding is (marginally, and as a technical point of no real consequence) a practice that if anything weeds out these harmful alleles.

Where inbreeding is very common and severe, the current generation will include a large number of individuals who had the bad luck to receive the same harmful allele from both parents, at several sites. This messes up their lives, but the gene pool of the suffering population is not in any way made inferior by this unfortunate practice.

Populations that are not inbred also carry around a genetic load. Just as big if not bigger. But, it does far less harm.