  The question of Jewish ancestry has been the subject of controversy for over
two centuries and has yet to be resolved. The "Rhineland Hypothesis" proposes
that Eastern European Jews emerged from a small group of German Jews who
migrated eastward and expanded rapidly. Alternatively, the "Khazarian
Hypothesis" suggests that Eastern European descended from Judean tribes who
joined the Khazars, an amalgam of Turkic clans that settled the Caucasus in the
early centuries CE and converted to Judaism in the 8th century. The Judaized
Empire was continuously reinforced with Mesopotamian and Greco-Roman Jews until
the 13th century. Following the collapse of their empire, the Judeo-Khazars
fled to Eastern Europe. The rise of European Jewry is therefore explained by
the contribution of the Judeo-Khazars. Thus far, however, their contribution
has been estimated only empirically; the absence of genome-wide data from
Caucasus populations precluded testing the Khazarian Hypothesis. Recent
sequencing of modern Caucasus populations prompted us to revisit the Khazarian
Hypothesis and compare it with the Rhineland Hypothesis. We applied a wide
range of population genetic analyses - including principal component,
biogeographical origin, admixture, identity by descent, allele sharing
distance, and uniparental analyses - to compare these two hypotheses. Our
findings support the Khazarian Hypothesis and portray the European Jewish
genome as a mosaic of Caucasus, European, and Semitic ancestries, thereby
consolidating previous contradictory reports of Jewish ancestry.
