There was an article maybe a decade ago where they showed how the kings and queens of European countries in the 18th, 19th and 20th centuries caused inbreeding because of the many diplomatic marriages, and they made some calculations on why the Romanov son got the disease because of this.Originally Posted by Sakkura
Edit: ok, here's how I think they meant the inbreeding increases the disease (though I'm no expert). Some males will always survive because they get a not too severe form of the disease. They will carry on the gene to their daughters. Inbreeding will make sure these alleles get more common among the female FMs. When they get more common among the female FMs, the male FMs too get them more likely. If you don't inbreed, you will lower the probability of the female FMs having them, because while it's likely that the non-FMs you marry also have some disease, they're less likely to have the same disease, and so you will gradually, generation by generation, decrease the probability of the disease by 75% per child. Inbreeding, on the other hand, gives a higher probability each generation.
Bookmarks