A population of Jewish people known as the Ashkenazi Jews have an unusually high risk of several genetic diseases, and up until now, no one has understood why. Was it random chance that made mutations so common or did evolution play a role in keeping mutations around? The answer to this question, said researchers at Stanford University Medical Center, appears to be chance. Their findings appear in the March online issue of the American Journal of Human Genetics and in the journal’s April print edition.