The genetic claims of this study are quite significant and seem to imply some variation of the Khazar theory of Ashkenazic Jewish origins, although this theory has up to now not found support in genetic studies. This area — along with the linguistic origin of Yiddish — is far outside my expertise, so I will say no more. But I will be very interested in seeing the responses to the published paper, which you can read here. The abstract is as follows [UPDATE: bad link now fixed. Sorry!]:
- Yiddish was thought to have originally been an old German dialect
- A new genetic study, however, has pinpointed origin of Yiddish speakers
- Suggests it was invented by Iranian and Ashkenazic Jews on the Silk Road
It may have been spoken for 1,000 years, but the origins of Yiddish – the language of Ashkenazic Jews – has been a bone of contention between linguists for years.
Now researchers say the DNA of Yiddish speakers may have originated from four ancient villages in north-eastern Turkey.
And they believe the Yiddish language was invented by Iranian and Ashkenazic Jews as they traded on the Silk Road, challenging the popular idea it is an old German dialect.
Scientists at the Universities of Sheffield and Tel Aviv used a tool dubbed the Geographic Population Structure (GPS) to convert DNA data into ancestral coordinates.
This enabled them to identify the ancient villages - Iskenaz, Eskenaz, Ashanaz, and Ashkuz – close to the crossroads of the Silk Roads, which were a historically important international trade route between China and the Mediterranean.
They believe the villages names derive from the word 'Ashkenaz' and may have existed as long as 1,500 years ago.
[...]
The Yiddish language is over one thousand years old and incorporates German, Slavic, and Hebrew elements. The prevalent view claims Yiddish has a German origin, whereas the opposing view posits a Slavic origin with strong Iranian and weak Turkic substrata. One of the major difficulties in deciding between these hypotheses is the unknown geographical origin of Yiddish speaking Ashkenazic Jews (AJs). An analysis of 393 Ashkenazic, Iranian, and mountain Jews and over 600 non-Jewish genomes demonstrated that Greeks, Romans, Iranians, and Turks exhibit the highest genetic similarity with AJs. The Geographic Population Structure (GPS) analysis localized most AJs along major primeval trade routes in northeastern Turkey adjacent to primeval villages with names that may be derived from “Ashkenaz.” Iranian and mountain Jews were localized along trade routes on the Turkey’s eastern border. Loss of maternal haplogroups was evident in non-Yiddish speaking AJs. Our results suggest that AJs originated from a Slavo-Iranian confederation, which the Jews call “Ashkenazic” (i.e., “Scythian”), though these Jews probably spoke Persian and/or Ossete. This is compatible with linguistic evidence suggesting that Yiddish is a Slavic language created by Irano-Turko-Slavic Jewish merchants along the Silk Roads as a cryptic trade language, spoken only by its originators to gain an advantage in trade. Later, in the 9th century, Yiddish underwent relexification by adopting a new vocabulary that consists of a minority of German and Hebrew and a majority of newly coined Germanoid and Hebroid elements that replaced most of the original Eastern Slavic and Sorbian vocabularies, while keeping the original grammars intact.Background on the Khazar theory and on Jewish genetics in general is here, here, here, here, here, and links.