[sphinx]

A friend, as a young officer in WWII, was stationed for a time in Delaware. Eligible men were in short supply and he was one of the available officers who were more-or-less pressed into service as social escorts for the armies of DuPont girls floating around Wilmington. He heard through the grapevine that the DuPonts had been intermarrying a bit too closely -- I don't suppose they were marrying first cousins, but a degree or two further removed could still have an effect ever time. Apparently the results were not good, and the docs had had a sit-down with the family elders and told them to cut it out.

The DuPonts might stand out as an interesting case study because they had a good thing going with the company, the city, and the state, which was virtually a DuPont estate. There were clear incentives to keep things in the family. I suppose the same thing has happened many times over the years when aristocracies of land, wealth, or status start to get a little clannish. You don't have to go the full Deliverance route to see the effects. I don't know enough about Muslim societies to comment, but the thesis is intriguing.

[Sherman Logan]

For a good idea of the beneficial effects of introducing new blood into a family, look at Prince Charles versus his sons.

Diana wasn’t royalty, but she very obviously had good genes. Probably because she wasn’t royalty.

[Scanian]

I can recall a passage in “Gone with the Wind” in which Scarlett’s father, I believe, extolls the virtue and success of Charleston families who retain their strength by marrying their cousins.

Along with retardation being multiplied through incest, talent can likewise be multiplied. The advocates of cousin-marrying likely think about the winners and ignore the losers.