Jon Entine in his book "Abraham's Children" has a map p124 that shows Jews in the Rhine River area in the 6-8 th Century. Do we know where these R1b Jews came from -possibily Spain or Khazaria?
The jews on your map most likely emerged first out of ITALY which had a large roman-era jewish populartion of close to a million, but let me state that is my opinion only, and I have no scientific way to establish that. Moneylending was religously illegal in this area of germany, although jews in italy had decrees excepting them such provisions, so I assume that they purchased similar decrees from the duchies and rulers in germany, and opened up a new market for lending that was not yet saturated as was the case in Italy.
The jews of western europe can only be studied from their descendents in other continents today because almost all those communites obviously no longer exist.
The geneticists of jewish descent are also not eager to clearly, accurately unravel matters as their is often fear, possibly well-founded, that this would be used to incite problems for the state of Israel.
From the studies mostly of North American, Australian, Immigrant-israeli jews,
this is what we know-
The jews of the low countries / rhine region are / were very
parentally intermixed with the resident gentile population.
The average descendent of Dutch jews has almost a 50% chance of falling into a west european Hg, R/I..
The female ancestry of askenazic jews is very heavily composed of, almost 33%, in the MTdna Hg of 'K'.. the 'K' Hg is not found significantly among the gentile population of these regions,
which is consistent with the jewish tradition that the maternal line is the line by which determination of whether the child is a jew is made.
This is considered problematic by some, as the sephardic community does not share the 'K' MTdna-
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002062#s3
"This is because more than one founder is likely to have existed within a given Hg, as we have shown using complete mtDNA sequencing for the Ashkenazi founding lineages within Hg K
[5]. "
Sephardic and Ashkenazic communities of jews DO NOT share the same genetics in the same proportions, or at all in some cases..
Sephardic population have on average less or no euro introgression, (THE EXCETION BEING SPAIN/PORTUGAL for specific reasons)
and a higher percentage of Semetic paternal Hg ancestry / Ydna Hg 'J'.
Askenazic Levites are VERY interesting as they (levi, levy, leavit, etc..) are the Paternal-descended lower priestly class of Judaism..
Go to Ysearch.org, and pull up all the variants of Levy.
You will find over 1/3 of the entire population of descendants on average falls in Y-dna 'R1a', which is not natively found in the middle east, but is found in the regions of the former kazaria, as well as the eastern european surroudings of their immediate residence.
Less than 1/3 of the total levy population paternally is descended from a 'J' semitic or 'E' mediternanean/african Hg...
the remainder are mostly in Euro R/I, or steppe population like Hg 'G'.
I would suspect that a significant part of the R1a levites are the result of converting khazars who chose to convert to a priestly cast, instead of as a routine worshipper..although this is not actually permitted, no one could/did stop them IN MY OPINION.
As to the R1b in the western Ashkenazic populations, it is well known, and their is really no answer beyond either conversion of husbands marrying jewish females, or intermixing with the local population. The populations of all european and north african jews have significant semitic ancestry, which aligns with Mizrahi genetics of those who never left the levant, however a significant and in some cases even majority of Ashkenazic genetics in particular is often of european origin.
THIS-
http://www.plosone.org/article/slid...RI=info:doi/10.1371/journal.pone.0002062.t002
paper/diagram shows the prominent jewish MATERNAL Hg by global community,
the same are available from studies on Jewish Paternal Hg, but these are very often NOT peer reviewed and I have always seem deliberate flaws that are incorporated to undercount what are seen as gentile components and accentuate Semitic Hg counts inaccurately.
Because of disputes over the modern middle-east, as well as conflicts between askenazics and sephardic communities in Israel, it is viewed as undesireable to assess non-semitic components of the ashkenazic communities.
The reality of the MTdna study as you can see, is such that the communities are often not maternally related across continents or even in the same MT Hg's, and that a substantial portion of the communities seem to be genetically related at least partially to the host population, so its not really surprising that the same results occur paternally,
hope this helped to answer your question.