The missing link of Jewish European ancestry: contrasting the Rhineland and the Khazarian hypotheses

Abstract

The question of Jewish ancestry has been the subject of controversy for over two centuries and has yet to be resolved. The "Rhineland hypothesis" depicts Eastern European Jews as a "population isolate" that emerged from a small group of German Jews who migrated eastward and expanded rapidly. Alternatively, the "Khazarian hypothesis" suggests that Eastern European Jews descended from the Khazars, an amalgam of Turkic clans that settled the Caucasus in the early centuries CE and converted to Judaism in the 8th century. Mesopotamian and Greco-Roman Jews continuously reinforced the Judaized empire 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, the Khazars' contribution has been estimated only empirically, as 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 to compare these two hypotheses. Our findings support the Khazarian hypothesis and portray the European Jewish genome as a mosaic of Near Eastern-Caucasus, European, and Semitic ancestries, thereby consolidating previous contradictory reports of Jewish ancestry. We further describe a major difference among Caucasus populations explained by the early presence of Judeans in the Southern and Central Caucasus. Our results have important implications for the demographic forces that shaped the genetic diversity in the Caucasus and for medical studies.

Fig. 1.—

Map of Eurasia. A map of Khazaria and Judah is shown with the state of origin of the studied groups. Eurasian Jewish and non-Jewish populations used in all analyses are shown in square and round bullets, respectively (supplementary table S3, Supplementary Material online). The major migrations that formed Eastern European Jewry according to the Khazarian and Rhineland hypotheses are shown in yellow and brown, respectively.

Fig. 2.—

An illustrated timeline for the relevant historical events. The horizontal dashed lines represent controversial historical events explained by the different hypotheses, whereas solid black lines represent undisputed historical events.

Fig. 3.—

Scatter plot of all populations along the first two principal components. For brevity, we show only the populations relevant to this study. The inset magnifies Eurasian and Middle Eastern individuals. Each letter code corresponds to one individual (supplementary table S3, Supplementary Material online). A polygon surrounding all of the individual samples belonging to a group designation highlights several population groups.

Fig. 4.—

Biogeographical origin of European Jews. First two principal components were calculated for Pygmies, French Basques, Han Chinese (black), Armenians (blue), and Eastern or Central European Jews (red)—all of equal size. PCA was calculated separately for Eastern and Central European Jews and the results were merged. Using the first four populations as a training set, Eastern (squares) and Central (circles) European Jews were assigned to geographical locations by fitting independent linear models for latitude and longitude as predicted by PC1 and PC2. Each shape represents an individual. Major cities are marked in cyan.

Fig. 5.—

Admixture analysis of European, Caucasus, Near Eastern, and Middle Eastern populations. The x axis represents individuals from populations sorted according to their ancestries and arrayed geographically roughly from North to South. Each individual is represented by a vertical stacked column (100%) of color-coded admixture proportions of the ancestral populations.

Fig. 6.—

Proportion of total IBD sharing between European Jews and different populations. Populations are sorted by decreasing distance from the Caucasus. The maximal IBD between each European Jew and an individual from each population are summarized in box plots. Lines pass through the mean values.

Fig. 7.—

Pairwise genetic distances between European Jews and other populations measured across (A) mtDNA and (B) Y-chromosomal haplogroup frequencies. The values of 1 − \udelta _{xy} are color coded in a heat map with darker colors indicating higher haplogroup similarity with European Jews.