

While I agree with you in principle, I actually do think that 1/7k is unexpectedly high. If 1/10k people had an incestuous relationship, that would be low enough that I wouldn’t find it surprising. This study, if we take it to be cross-sectional, implies that the rate of incidence is much higher, at least on the order of 1/1k, possibly something around 1%. I don’t know the frequency that people of incestuous individuals have a child as a result, but the idea of it being higher than 1/7 strikes me as unlikely. Of course, multiple children can result from a pairing, so that has the potential to sway the numbers, but I’d hope that incestuous individuals are less likely to desire children from the relationship, and as a result would take a pregnancy as a sign to stop.
No, but I’m also an extremely permissive DM.