See the 27:30 to 32:00 mark for Lipson's discussion of distinctively Ashkenazi subclades that have existed in the West since well before the 750 AD juncture. The most significant, according to Lipson, the 3rd largest Cohanim line, is a subclade of J2b which *descends* from the Etruscans but does not *split off* and become *specifically* Jewish until around 200 to 300 CE. He cites the 2019 Antonioni paper here. Lipson also mentions R-L4, a subclade of the more broadly Celto-Latin R1b-U152, which he thinks is slightly younger, branching off as *specifically* Jewish around 300 to 500 CE. Last, he mentions his own personal lineage, a subclade of E, that while probably Levantine in origin appears to have existed in the Western Mediterranean since at least 350 to 400 CE, and today has closely related branches in Tunisia, Sicily, Spain, France.
Nonetheless, without relistening to entire interview, my impression is that both Razib & Lipson believe most Ashkenazi descend from Y-lines that moved *directly* from modern-day Israel to Italy in the 8th century. The lineages mentioned in the paragraph above are exceptions to this broader pattern. But given the complexity of Ashkenazi genetics, perhaps the question is not so clear-cut. Have there been any studies devoted to Sephardics?
Yes, I find the speculation, toward the end of their conversation, that Jewish males may have admixed circa 750 with local Italian women who were somehow more "pagan" unconvincing. Although this might hold true for what happened in Eastern Europe, especially with Litvaks, in Italy the most "pagan" women would have been in more rural areas, while Jewish newcomers were likely in towns.
I just re-listened. By the time the "Jewish" branch of J2b2 coalesced in 200-300 C.E. the Etruscans were long gone, absorbed into the broader population. Plus, while I get that Lipson, like a lot of other Jewish researchers, wants the admixture to have happened in Europe, that lineage is not, to my knowledge, unique to Italians of the Imperial Era.
The debate between Lipson and Khan is this:
Lipson, using coalescence dates for certain y chromosomes, is placing the date of admixture between Southern Europeans, specifically Italians, in the Imperial Period. Khan, using the Carmi method which is based on autosomes and the length of chromosome segments which can be labeled as Southern European, puts it at 750 A.D.
So far as I can tell, they agreed to disagree.
Khan, going by the Carmi analysis, and seeing just two admixture groups, Levantine and Southern European, specifically more Central/Western Southern European, assumes that since the "Levantine" group is relatively "pure", that it must have recently arrived from the Levant.
I think that's an unwarranted assumption.
For one thing there weren't all that many Jews in the Levant in 750 A.D. There had been three rebellions in the East, let's not forget, with resulting exiles. The number of Jews living there was much reduced.
Second of all I don't know why he thinks that Jews who were living in the West would show admixture already by 750 A.D. so the males, presumably, who were admixing with Italian women would have only Levantine chromosomes. That's not necessarily true.
On balance I'm leaning more toward Lipson on this, although I don't know how either he or Khan explain this sudden emergence of a group of Jewish males who found themselves without Jewish females with whom to mate.