History and Genetics: Ashkenazic Jewry in the Rhineland

Part VI

During the Roman period, the Jewish community began to spread throughout the northern shore of the Mediterranean  to move, in small numbers, into various European locations.  For this reason, archaeological remains of small Jewish communities are scattered throughout southern Europe.  Even further to the north, small Jewish quarters are in evidence from Roman times, as Jewish traders follow the Roman armies and or trade routes. The larger communities of Italy and North Africa had come into being by substantial migrations, but in the Jewish move into Europe small groups of families or males alone established these new communities and, hence, inclusion of local women may be observed in the DNA record.

For a variety of reasons, historians have maintained that the Ashkenazic communities of medieval Franco-Germany (Hebrew: Ashkenazi) were developed as a result of a process by which Jews came from the Land of Israel to the boot of Italy, moved up further to the north of Italy, and then moved further up into areas that are now parts of northern France and Germany.  This does not mean that the same families made the entire trip, although in some cases we know that they did.  For the most part, we are dealing with a complex process of slow migration as families moved further north. These communities derived their religious and literary character from the influence of the ancient culture of the Land of Israel in Talmudic times. For example, the presence of Byzantine period Palestinian liturgical poetry in the holiday liturgies of Ashkenazic Jewry is explained in this manner.

Genetic markers have also suggested that this community was founded by a small number of immigrants, a situation likely in the light of other historical sources. Investigation of a number of disease mutations that are almost exclusively found among Ashkenazic Jews has provided coalescence of approximately 40 to 50 generations ago. This yields a date of approximately 1000 years ago, when we know that the Rhineland Jewish communities came into existence.

Y chromosomal studies have found that Ashkenazic Jews come from seven Y lineages.  Only four of these are transmitted from the Middle East and two entered the population in Europe.  However, not all Middle Eastern elements in the genetics of the European population should be seen as Jewish. Other Middle Eastern people came to Europe already in prehistoric times.  However, some of the European Y chromosome elements can only be explained by intermixing between non-Jewish men and Jewish women.  As can be expected, our historical sources testify to all of the same possibilities that we can imagine: some non-Jewish men converted to Judaism, although this was restricted by Christian authorities and has to be assumed to have been very rare; some Jewish women gave birth to children out of wedlock or adulterous relations, and some were raped.  The rate of admixture and intermarriage with European populations after the founding of the Ashkenazic community is assumed to be 5-8%.  This is equivalent to 0.5% per generation.  The admixture of males shows evidence of two separate stages, one of types expected in the German context and the second an admixture of East European genetic elements, common with Ukrainians, Poles or Russians. All this adds up to a situation in which the community was constructed on the combination of founder events, that is, core families who provided the initial population, and admixture of males that we have discussed, as well as a similar small admixture of females.

From analysis of mitochondrial genomes it appears that only four subtypes account for 70% of the Ashkenazi Jews.  This suggests a total of four female founders.  These founders appear to descend from families that come from the Middle East from which they migrated to the Rhineland.  It is fits well with what historical sources tell us about the Israel-Italy-Germany connection. Some other founding females seem to have derived from the non-Jewish population.  This phenomenon indicates the possibility that some males in the earliest community of Rhineland Jews had no choice but to seek wives from beyond their genetic group[1] since fewer females had immigrated than males. This may provide a pattern for the manner in which some other small communities were developed.

 Theories that Ashkenazic Jews were derived primarily from converts, be they Khazars, Slavs or anyone else, are totally disproven by Jewish genetic research.  But this should not surprise us since historical sources, read carefully and without prejudice, do not give any indication of such mass conversions to Judaism in Europe.[2] This is certainly the case with the Khazars, although our sources do indicate conversion by some of the elite classes.  It is possible, therefore, and some geneticists have argued, that there was an infusion of some Khazar genetic material into the Ashkenazic Jewish community.  But this would have been in Eastern Europe, to which we now turn