Incest, morality and genetics

Over at Secular Right I point out that Romania is set to decriminalize consensual sexual relations between adult first-order kin. That is, incest. There are a few angles that this story offers. First is the moral-ethical one. From a rational individualist perspective how reasonable are laws which ban consensual sex between adults who just happen to share distinctive genetic information? The love that dare not speak its name because of alleles which are identical by descent? Of course all this rational talk is irrelevant for most people. Incest is gross, repugnant and immoral. Not because incest is irrational or unreasonable, human instinct just tells us that it's wrong. For most humans the repulsiveness of incest requires as much justification as the repulsiveness of consuming feces. My earlier post, The biological roots of moral sentiments?, and Jonathan Haidt's distinctions between liberal and conservative morality, are relevant in explaining some of the ...