DNA studies have shown us who the Jews are, biologically. All varieties of Jews (MIzrahi, Sephardic, Ashkenazi) are crossbreeds between Europeans and Middle Easterners. The Ashkenazi have the highest degree of European admixture, around 40% on average. But all of the Jewish groups are more closely related to each other than to their host populations. The name-changing is explainable as an effort to appear less different from their hosts than they really are.