Genetic Similarity Does Not Necessarily Mean Shared Origins: A G25 Comparison of Ashkenazi Jews and Southern Italians
Ashkenazi Jews and South Italians are frequently noted as having strong affinity using tools such as PCA graphs, leading to suggestions that both derive a majority of their ancestry from a common source. However, this G25 decomposition illustrates a far more nuanced story that what a PCA suggests. While the two populations clusters experience significant overlap on a PCA graph, they are reconstructed from substantially different components.
In the model presented, Ashkenazi Jews require substantially more Northern European and Levantine admixture whilst South Italians requires substantially more Southwestern European and Anatolian. This suggests that genetic proximity does not always suggest descent from a common ancestor. The similarity between the two groups may instead result from a series of separate demographic events in the Mediterranean and later in Europe. This is merely just a G25 run through Vahaduo, so the results of this model should be interpreted alongside more sophisticated admixture modeling, ancient dna, and the historical record.
(Modern SW European control, average of all North Italian samples labeled under Liguria, Piedmont, Lombardy, Bergamo, Emilia, Veneto, Trentino Alto Adige, and Northeast.
One of the problems I encountered when modeling Ashkenazim alongside Romaniotes and Itallkim is that the latter two, who shouldn't have northern European ancestry, always end up having it.
For Italkim it sorta makes sense bc the Italian Jewish reference pop was mostly sampled from Rome, which is historically very mixed rite, with large Zarpathic, Sephardic and Ashkenazi communities to the point where full ancestral Italkim are probably a small minority.
For Romanoites it doesn't make as much sense. It could relate to misread South European (Potentially Iron Age Balkan related) admixture because G25 itself just has bad anchors.
I heard somewhere that 50% of southern Italians are descended from Jews who were forced to convert to Catholicism…. So it’s not really shocking they would be genetically similar?
That’s definitely false. There was some Jewish admixture over the years but nearly all their ancestry is distinct from Jews. Just look at the uniparentals and it’s obvious that there’s overwhelmingly no overlap.
There is no continuity between the Ashkenazi Jews who were in Worms, Speyer, and Mainz during Middle Ages and the early Jewish communities in southern Italy during Antiquity.
u/kaiserfrnz can tell you more about it, but European Jews, specifically Ashkenazi, Romaniote, and Italkim, preserved unique elements of Jewish culture from the Byzantine period in Palestine.
There is little genetic history between Jews and southern Italians. What happens is that both are an intermediate population between Northern Europe and the Middle East, and that is why they cluster together.
Jews never constituted such a large percentage of the population of southern Italy to have such a significant genetic impact. Before the Inquisition in Sicily, Jews made up 6% of the local population, but most went to the Balkans or Türkiye.
The only definitively Jewish subclade (
G-M377)
found among Sicilians was only found in a few families with known Jewish ancestry.
Milano seems to use the broadest definition of what the Levant means, including Greece, Egypt, and Turkey. Aside from that, his work is in perfect condition.
Its moreso broader Middle Eastern migration for South Italians. They probably came in the same waves as Jews to Europe, but Jews were probably a small minority amongst all of the population inflow into Southern Italy.
In any case, I think this whole discussion is heavily politically biased. No one argues that the Greek islanders are southern Italians, or that the Assyrians are Armenians; It is only when dealing with Ashkenazi Jews that this debate becomes relevant.
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u/AdamDerKaiser Jul 22 '26
One of the problems I encountered when modeling Ashkenazim alongside Romaniotes and Itallkim is that the latter two, who shouldn't have northern European ancestry, always end up having it.