Is Europe still rat-infested like it once was? And what percentage of Europeans have the CF mutant gene?
1 out of 34 depending on where you are looking ~ some higher/some lower. http://www.clinchem.org/content/57/6/841.full is rather complex but in summary this is not just a white folks thing but fur shur the incidence among whites is far higher than the other groups wherever they might be.