The article is quite interesting, but I have to say I don't understand why Yiddish being a Slavic language would suddenly mean that all European Jews are Iranian; the Slavic languages aren't descended from anything spoken in Iran in the first century CE. That really feels like it came out of nowhere.
It didn't exactly come out of nowhere, it was prefaced by "a fringe tends to develop; in Yiddish linguistics, that would be Paul Wexler".
As an L2 german (standard & dialect) speaker who's learning a slavic language I think "fringe" may be the charitable way to put it. (I've experimented with alemannic dialect speakers and upon first exposure they tend to think of yiddish as a different german dialect with some bizarre vocabulary)
> In a lokh in der erd hot gevoynt a hobit. Nit keyn bridke, koytike, nase lokh, ongefilt mit di ekn fun verem un a dripendikn reyekh, oykh nit keyn trukene, hoyle, zamdike lokh mit gornisht vu zikh avektsuzetsn tsi vos tsu esn: zi iz geven a hobit-lokh, un dos heyst bakvemlekhkeyt. —JRRT
As a native Slavic speaker that can also speak an almost fluent Dutch, and knowing what the quoted Hobbit line says, I can't even see how this having anything to do with Slavic languages is even a discussion.
There is one word of Slavic origin in that paragraph: bridke (English ugly, Polish brzydki, German hässlich). (And I can't find a cognate for "dripendikn" in any other language.)
I wonder why anyone would think that. The words predominantly come from German, and the grammar is more of a thing of its own, far from resembling anything Slavic...
Most people who encounter Yiddish outside of the religious Jewish community encounter Western Yiddish. Most people who learn Yiddish as a first language today would be speaking Eastern Yiddish (think Ukraine, Belarus, Lithuania, Russia), which has more obviously Slavic elements.
The standard historical explanation for this is that Yiddish began as a Germanic language, and the Eastern dialects developed after Jews were expelled from Germany in the 14th century and migrated East. There were already Jews living there, but the population grew tremendously with the migration.
Paul Wexler's thesis is that the Eastern dialects of Yiddish actually independently descend from early Jewish Slavic languages (e.g. https://en.wikipedia.org/wiki/Knaanic_language), and the Western dialects are derived from the Eastern ones.
Paul Wexler's thesis is that the Eastern dialects of Yiddish actually independently descend from early Jewish Slavic languages (e.g. https://en.wikipedia.org/wiki/Knaanic_language), and the Western dialects are derived from the Eastern ones,
"... a hypothesis that has been widely rejected by other Yiddish and Germanic linguists and geneticists", says his WP bio.
The fringe nature of this hypothesis is discussed in the article itself. I was just explaining why one would even think to go down this road to begin with.
As another comment mentioned, both of those claims come from one theory that is considered as fringe in this field. That is explained in the article, although how those specific claims are being linked is not detailed.
Iranian languages and peoples that are referred here are not from Iran though. During ancient and middle ages there were various Iranian peoples in Eastern Europe, speaking Iranian languages and distantly related to modern people in Iran. These were very prominent, with two of these peoples, Scythians and Sarmatians, being used as names for the whole East Europe during the times of ancient Greek and Rome. In early middle ages, the Iranian tribe Alans also spread to western Europe, and there are still Iranian peoples such as Ossetians living in north of the Caucasus. For the first century CE, it would be these Iranian populations in eastern Europe which interacted with Slavs and are a source of many loanwords.
I guess the theory goes so that a significant Iranian population in central or east Europe would have converted to Judaism and thus they would make up a large portion of European Jews' ancestry. It's probably not so, because while there certainly were many individuals or small groups converting and thus being part of Jewish ancestry, we don't really have evidence of large-scale conversions.
Of course there has been the whole political debate based on these theories, which goes to claim that "Jews are not Jews" because according to their views, almost all Ashkenazi Jews would be descended from European converts and have little to none Middle Eastern ancestry. This often goes to antisemitic direction if it's used as basis to deny some part of Jewish culture, for example. But if such conversions ever happened in a large scale, that was 1000 years ago, and surely the Jewish people whose ancestry is from one of those groups who converted, are as Jewish as are those with Middle Eastern ancestry.
