Ashkenazi Jewish genetics: a match made in the Mediterranean

How and when did the Ashkenazim come to be?

Great Synagogue of Vilna, 1930

Also: The eternal wanderers: Sephardic Jewish genetics and culture and Under pressure: the paradox of the diamond.

Sometime after the year 1000 AD, a group of Jews began migrating eastward across Europe, into the principalities of Germany and the kingdom of Poland, attracted by the combination of religious tolerance and economic opportunity. These territories were beyond the frontiers of the Roman Empire; they were lands that Jews had traditionally not occupied. By the time these pioneers arrived in the small towns of Germany and the hamlets of Poland, Jewish communities had already been established in Persia and Egypt for 1,500 years. Even more mysterious, the Jews migrating out of the west into Germany encountered another community of believers issuing out of the east. These were Slavic-speaking Jews whose ultimate provenance is even more opaque. Though the cultural memory of the later Ashkenazim draws upon the western Jews whose forebears sojourned in France, the imprint of the eastern Jews is unmistakable with the tools of modern genetics.

For the next 800 years, these Jews, a synthesis of Western and Eastern European, waxed in numbers due to their essential economic position in the developing lands of Eastern Europe, but unlike the Hebrews of antiquity, they became culturally invisible to their gentile neighbors, quietly navigating a closed social universe organized around adherence to their own laws and focused on their own texts. Their ultimate origins were a mystery to the gentiles around them, and indeed became forgotten even to themselves. Were they the descendants of the ancient Hebrews, converts to the religion, or a mix of both? These possibilities were hidden from the Jews of Eastern Europe as their memory of their past faded and their written culture focused purely on matters of religion. 

This curiosity is worth pausing over. Ashkenazi Jewish luminaries have recorded such outsized contributions to every aspect of human output in culture and knowledge over the past two centuries, it’s natural to assume that the familiar intellectual restlessness and insatiable curiosity of the community’s standouts have deep cultural roots. But if the textual record is anything to go by, nothing could be further from the truth. Hunting for attested evidence of Ashkenazi Jewish passage from antiquity to the 19th century is like trying to catch a glimpse of a secretive nocturnal creature. Not only did Jews receive unhelpfully scant coverage from gentile chroniclers, but the community itself also appears to have trained its considerable literacy and intellectual power solely on matters Talmudic, to the complete exclusion of any historical records of the various communities.

And yet, it was these people that flourished in the unknown and wild lands of Eastern Europe who would go on to beget 80% of the modern Jewish diaspora, and join the mainstream of Western civilization after 1800. These are the more than ten million Ashkenazim, whose members have left indelible marks on world history and culture so far out of proportion to their numbers, from Karl Marx to Albert Einstein, since their reintegration into the stream of Western civilization after the Enlightenment.

In the Bible, Ashkenaz is one of the descendants of Noah, and Jewish scholars associated his scions with various points north, initially Scythia, but eventually Germany. So the Ashkenazim were the Jews of Ashkenaz, of Germany and parts east, and their native language, Yiddish, was a dialect of German. The Jews of Spain and Portugal, the Sephardim, loomed large during the medieval period between 1000 and 1500 AD, producing the great rabbi Moses Maimonides and polymath Judah Halevi, and persisting in prominence into early modernity, with philosophers like Baruch de Spinoza. It was only in the 19th and 20th centuries that the history of Jewish prominence and cultural achievement became so disproportionately the story of the Ashkenazim, who were 92% of the world’s Jews in 1930, and have shared in fully 20% of all Nobel Prizes awarded.

And yet, though the Jews are a people whose history is extensively documented, from the Bible to Josephus’ Roman-era The Jewish Wars, the origins of the Ashkenazim remain a bit of an enigma. In 1096 AD, Christian crusaders infamously massacred Jews in the German Rhineland as warm-up for the slaughter they would inflict upon people in the Middle East, and the German-speaking lands saw widespread pogroms in the mid-14th century, at the height of the Black Death. But in comparison to their ubiquity in the 19th century, the Ashkenazim are mentioned only glancingly in the histories of this earlier period. They came to be notable only with their demographic ascendence in the massive dominion of Poland-Lithuania, as the Middle Ages gave way to the Renaissance 500 years ago. Not to mention in their later cultural explosion in the modern world.

Given Ashkenazi Jews’ newfound prominence and mysterious origins, in the late 19th century, European intellectuals began to explore the “Khazar hypothesis” for the origin of the Ashkenazim: the strange idea that Eastern European Jews descended from an ancient Turkic steppe confederacy destroyed by Kievan Rus 1,000 years ago. The Khazars are notable because much of their elite reputedly converted to Judaism while other groups were adopting Christianity or Islam. The Khazar hypothesis’ argument was that the Ashkenazim descended from the scattering of Khazar Jews westward into Europe. It is only with genetics in the 21st century that this theory has been able to be tested, and ultimately found mostly wanting. The Ashkenazim are mostly the synthesis of ancient Levantine Jews and various Mediterranean European populations with whom the former mixed. Their origins date back to the fall of Rome, not the fall of Khazaria. And yet there is now a glimmer of light that might allow for a Khazar origin: the Ashkenazim descend in part from Jews that seem to have settled in the early medieval state of Great Moravia in Eastern Europe. These Slavic-speaking Jews seem to have brought more Northern European ancestry into the Ashkenazim, and it is through them that the most likely vector for the small fraction of East Asian ancestry found in modern Jews arrived.

In the intersection

To understand when and where the Ashkenazim come from, it is important to understand what they were before they became the distinctive people we know from history and fiction. The ancient King David was a simple shepherd, while the Babylonian Talmud outlines how farmers must maintain adherence to the laws of the Torah despite the agricultural season’s cycles. 2,000 years ago, the Jews were both pedestrian and unique. Pedestrian in that they were a nation of farmers and shepherds, as extensively documented in the Bible. Yes, large communities of urban Jews flourished in Alexandria, Rome and other large cities, but on balance, the Jews were not particularly urban. Like the Jews, Greeks outside of their homeland tended to be urban as well, but the average Greek was still a farmer or a shepherd, as were the vast majority of humans in the ancient world (not to mention, incidentally in the world as a whole until the 20th century). The ancient Jews were tillers of the soil and drivers of flocks, like all their contemporaries.

Where the Jews were unique was their strict adherence to a set of laws handed down to them by a god whom they held to be the one true god above all others. The Jews were zealous in their religious particularity, a reality which led to a war of liberation against the Greeks in 167 BC, where they rebelled against the imposition of pagan syncretism by raising an altar to Zeus in the Jewish Temple. Today we know of this war mostly through its commemoration at Hanukkah. Once Rome rose and conquered the Eastern Mediterranean, the Jews rebelled twice against the Roman imperium, once in the first century AD and once in the second. Again, the cause of their rebellion was the fact that they chafed at the rule of the religiously tolerant but unabashedly polytheistic Romans. The first rebellion was triggered by riots that erupted in 66 AD when pagan Greeks provocatively sacrificed birds in front of a synagogue, an act of sacrilege in Jewish eyes meant to inflame tensions in Jerusalem. The first rebellion ended a period when Jews were prominent in Roman elite circles, particularly due to the Judaean client king Herod Agrippa’s friendship with the Roman Emperor Caligula. From then on, Jews were tolerated, but seen to be different: a people apart. 

The Jewish farmers and warriors who characterized the nation in the first centuries of the Common Era would eventually fade from living history, recalled only as legends in scripture and oral tradition. By the time European Jews became more than marginal curiosities in early modernity, pure subsistence agriculture and a martial ethos had become wholly alien to the Jewish mode of existence for the urban and small-town Ashkenazim. The Zionist movement made explicit efforts to synthetically re-install the ethos in the new settlers of Palestine. Zionism emerged from socialism and 19th-century nationalism and imagined a robust patriotic citizenry working the land on collective farms, the kibbutzim, at the ready to rise as a nation and take up arms against enemies near and far. Set against this future ideal was the contemporary bourgeois life that was aspiration and reality for many of the European Ashkenazim, who had already made the comfortable transition to material security in the wake of the piecemeal Jewish emancipation that swept the continent over the course of the 19th century.

But these assimilated Ashkenazim still came from an earlier regime, where Jews were set apart from the nations among whom they dwelt. Whereas their biblical ancestors had been farmers, pastoralists and warriors, the Ashkenazim known from later medieval and early modern history occupy professions avoided by Christians. The more modest members of the community were peddlers and artisans serving rural villages, while the Jewish elite were money-lenders and tax-farmers, intermediaries between the aristocracy that ruled much of Europe and the peasants whom they exploited. The enmity toward the Ashkenazim pervasive across much of Europe in the early modern period derived from this experience, as the dirty work of wringing taxes from poor, immiserated farmers fell to the Jewish subordinates of rural nobility. Meanwhile, in the domain of high finance, Jewish families like the Warburgs and Rothschilds were to make their mark as lenders to kings, weathering all the risks and exulting in the windfalls that ensued.