Razib Khan One-stop-shopping for all of my content

March 22, 2018

The origin of the Ashkenazi Jews in early medieval Europe

Filed under: Ashkenazi Jewish Genetics,Ashkenazi Jews — Razib Khan @ 9:27 pm


Last year’s The time and place of European admixture in Ashkenazi Jewish history is very close to the last word on the genetics of the ethnogenesis of Ashkenazi Jews. Here’s the author summary:

The Ashkenazi Jewish population has resided in Europe for much of its 1000-year existence. However, its ethnic and geographic origins are controversial, due to the scarcity of reliable historical records. Previous genetic studies have found links to Middle-Eastern and European ancestries, but the admixture history has not been studied in detail yet, partly due to technical difficulties in disentangling signals from multiple admixture events. Here, we present an in-depth analysis of the sources of European gene flow and the time of admixture events by using multiple new and existing methods and extensive simulations. Our results suggest a model of at least two events of European admixture. One event slightly pre-dated a late medieval founder event and was likely from a Southern European source. Another event post-dated the founder event and likely occurred in Eastern Europe. These results, as well as the methods introduced, will be highly valuable for geneticists and other researchers interested in Ashkenazi Jewish origins.

Roughly the Ashkenazi Jews are a half and half mix of a Middle Eastern population and various European groups. The majority of the European ancestry is “Southern European,” probably something like Italian. But, a minority of the European ancestry is like “Eastern European.” Additionally, the former admixture pre-dated the bottleneck, and probably dates to ~1000 A.D., while the latter event post-dates the bottleneck.

For years I had thought that Isaac Bashevis Singer’s excellent novel The Slave was interesting but implausible. The reason being that Ashkenazi Jews and their gentile neighbors did not mix by this time, as the European ancestry in Ashkenazi Jews dates to the Roman period.

These results reject that model…the tract-length evidence is persuasive to me that admixture with Slavs did occur.  Some Italian groups are more north shifted, but the most parsimonious explanation while the Eastern European like ancestry came in later is that it tracks Jewish migration into Germany and Poland-Lithuania later.

The dating of admixture is something I’m less sure of. At 625 to 1,250 years before the present, it puts the emergence of the Ashkenazi community firmly in the Christian era. I don’t want to get into too many details, but from what I have read the Church and local authorities frowned on Jews owning Christians slaves, and tried to suppress instances where Christian slave women became concubines to Jewish men or even Judaized.

I had long assumed that these records reflect elite paranoia. If the dates of admixture are right they may reflect a real concern and a phenomenon (the Y and mtDNA evidence strongly point to the likelihood that the pattern was generally partnerships between Jewish men and gentile women).

And to be frank they tell us less about Jews than they do about the nature of “Christian Europe” in the early medieval period. There is one school of Reform Protestant which takes a dim view of how deeply Christian medieval Europe ever was. I think these results support the thesis that Christianity was an elite religion whose grasp upon the masses was more tenuous and illusory than we might imagine. There is also the reality that the feudal Christian state never had totalitarian authority over the population.

In theory Jewish assimilation of Christians to their identity, Judaizing, could be a capital crime. But if these results are correct it was quite common in the formation of the early Ashkenazi community before it moved north and then east. This decentralization and relative weakness of the early medieval Church and state, the superficially of mass Christianity, might also explain how vast regions of France defected from orthodox Christianity for decades in the 12th century during the ascendancy of the Cathars.

On a final note, I decided to do a little probing on the Middle Eastern forebears of the Askhenazi. The paper says that Levantine populations are the most likely source, which is entirely unexpected. But I wanted more detail, so I used the Human Origins Array dataset. You can see on the PCA above that the Ashkenazi Jews are shifted toward the European (Basque) population away from Middle Easterners, but if you project the line outward it lands on Christian and Muslim Lebanese. Haber et al. last year showed that there was continuity between the modern Lebanese and Caananites, and the Jews were likely originally a form of Canaanite. Curiously, Palestinian samples in the data are strongly shifted away for the Lebanese, toward groups like Saudis.

I understand it’s a hot potato politically, but if I didn’t have a dog in this fight I’d say that the contention that Palestine and Jordan (look at the Jordanian sample positions) underwent some population turnover is likely true (though I’d be curious about the data on Palestinian Christians).

July 21, 2012

Ashkenazi Jews are not inbred – 2

I know I excoriate readers of this weblog for being stupid, ignorant, or lazy. But this constant badgering does result in genuinely insightful and important comments precisely and carefully stated on occasion. I put up my previous post in haste, and when I published it I wasn’t totally happy with the evidence from which the authors adduced that Ashkenazi Jews were not inbred. Here’s why, from the comments: Doesn’t identity-by-state permutations test reflect a counterbalance of admixture vs. inbredness + drift? Rather than just the degree of inbreeding? Since the population has strong admixture effects, a low IBS doesn’t exclude strong inbreeding, does it?

From my little personal experience IBS is not the best statistic from which to generalize widely, and can be highly misleading in admixed individuals, as implied by the commenter. First, since I’ve stated above that the Ashkenazi Jews are admixed, let me go into a tangent as to why Ashkenazi are admixed between a Middle Eastern and Western European population, as opposed to being a relatively unadmixed ancient Eastern Mediterranean group with affinities to both regions. The previous previous paper found evidence of linkage ...

July 20, 2012

Ashkenazi Jews are not inbred

Jews, and Ashkenazi Jews in particular, are very genetically distinctive. A short and sweet way to think about this population is that they’re a moderately recent admixture between a Middle Eastern population, and Western Europeans, which has been relatively isolated due to sociocultural forces. As far as their inbreeding, well, here’s one recent paper, Signatures of founder effects, admixture, and selection in the Ashkenazi Jewish population: To explore the amount of genetic variation within the AJ and European populations, we first measured the mean heterozygosity. Surprisingly, we found a higher level of heterozygosity among AJ individuals compared with Europeans…confirming speculation made in one recent report and a trend seen in another…Although this difference may appear small, it is highly statistically significant because of the large number of individuals and markers analyzed, even after pruning SNPs that are in high LD. The higher diversity in the AJ population was paralleled by a lower inbreeding coefficient, F, indicating the AJ population is more outbred than Europeans, not inbred, as has long been assumed…The greater genetic variation among the AJ population was further confirmed using a pairwise identity-by-state (IBS) permutation ...

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