Comments by "" (@RedXlV) on "THE SHY HISTORIAN" channel.

In isolation, a single pair of first cousins marrying doesn't really increase the incidence of genetic disease. But if their ancestors had also been marrying first cousins frequently, it adds up quickly.
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@ChrispyDubstep That's even more restrictive than most people would think, since there aren't very many surnames in Korea. IIRC it's less than 300 total. That's because for most of Korean history, surnames were exclusively for royalty and nobility, and even as recently as 100 years ago, a majority of Koreans had no surname. So when everybody was required to have a surname, there didn't end up being much variety, and a lot of unrelated clans ended up with the same surname. Also, more than 1/5 of South Koreans have the surname Kim.
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