[alexander_busek]

There is an increased risk, but it's a lot lower than most people think. Probably in the vicinity of 7% to 11% increased risk of serious birth defects.

So, if, e.g., the risk of being born with a cleft palate is on the average 1 in 700 when the parents are non-consanguine, then incest would boost that risk to only 1 in 650 to 1 in 620?

Regards,

[Sherman Logan]

I think that’s right. But it depends drastically on the genetics of the people involved.

There is of course a very longterm experiment underway in the effects of first-cousin marriage. Many Muslim groups primarily marry their first cousins, and this has been going on for a very long time indeed.

It is clear from UK statistics that they have significantly increased birth defect rates, but if marriage to close relatives was as dangerous as commonly assumed, they would have died out as a people a good many centuries ago.

Any good dog or horse breeder, btw, knows that inbreeding concentrates good traits as well as bad ones.