Jews, no matter where the diaspora has become dispersed around the world. Moreover, DNA tests have demonstrated substantially less inter-marriage in most of the various Jewish ethnic divisions over the last 3,000 years than in other populations. The findings lend support to traditional Jewish accounts accrediting their founding to exiled Israelite populations, and counters theories that many or most of the world's Jewish populations were founded by entirely gentile populations that adopted the Jewish faith, as in the notable case of the historic Khazars. Although groups such as the Khazars could have been absorbed into modern Jewish populations — in the Khazars' case, absorbed into the Ashkenazim — it is unlikely that they formed a large percentage of the ancestors of modern Ashkenazi Jews, and much less that they were the genesis of the Ashkenazim. Previously, the Israelite origin identified in the world's Jewish populations was attributed only to the males who had migrated from the Middle East and then forged the current known communities with "the women from each local population whom they took as wives and converted to Judaism". Research in Ashkenazi Jews has suggested that, in addition to the male founders, significant female founder ancestry might also derive from the Middle East, with about 40% of the current Ashkenazi population descended matrilineally from just four women, or "founder lineages", that were "likely from a Hebrew/Levantine mtDNA pool" originating in the Near East in the 1st and 2nd centuries CE. Points in which Jewish groups differ are the source and proportion of genetic contribution from host populations. For example, the Teimanim differ to a certain extent from other Mizrahim, as well as from Ashkenazim in the proportion of sub-Saharan African gene types which have entered their gene pools. Among Yemenite Jews, the average stands at 5-10%, due to the relative genetic isolation of Yemenite Jews this is only a quarter of the frequency of the non-Jewish Yemenite sample, which can reach 35%. In Ashkenazi Jews, the proportion of male indigenous European genetic admixture amounts to around 0.5% per generation over an estimated 80 generations, and a total admixture estimate around 12.5%. The only exception to this among Jewish communities is in the Beta Israel (Ethiopian Jews); a 1999 genetic study came to the conclusion that "the distinctiveness of the Y-chromosome haplotype distribution of Beta Israel Jews from conventional Jewish populations and their relatively greater similarity in haplotype profile