- New paper on genomic differences between Ashkenazi Jews and Europeans
- 300K SNP paper on European genetic substructure
- European population substructure revealed by genetics
On the other hand, the conclusion that the genetic distinctness of Ashkenazi Jews is due to Middle Eastern ancestry is not demonstrated by this study. For example, the Uyghur of Central Asia are distinct from both East Asians and Caucasoids, but this is not due to any mysterious "Central Asian" component in them, but rather due to the fact that they are an admixed population of Caucasoids and Mongoloids.
To demonstrate the specific Middle Eastern background of Ashkenazi Jews, it would be a good idea to also study other Jewish groups. If it is shown that the various Jewish groups possess a common autosomal genetic component, then the simplest explanation would be that this component stems from the ancestral Jewish population of the 1st millennium AD, prior to the separation of the various Jewish groups from each other.
Moreover, the genetic distinctiveness of Ashkenazi Jews does not in itself say anything about the extent of Middle Eastern ancestry in this group. For example, in this paper, the Middle Eastern groups (mostly non-Jewish Semitic groups recruited in Israel) were different from other Caucasoids by the possession of a specific ancestral component (color-coded brown), but the extent of this component differed among them.
With that said, I do suspect that the distinctiveness of the Ashkenazi Jews is in part due to the possession of a Middle Eastern component of unspecified strength. I base this hypothesis on the results reported to me about the EURO-DNA-CALC test. This test distinguishes between NW, SE Europeans and Ashkenazi Jews; a few Arab individuals who have communicated their results to me have reported fairly high AJ components, indicating that part of what distinguishes an AJ from Europeans is related to the Middle Eastern Semitic background of that group.
The way forward is of course to perform a comprehensive admixture analysis where Europeans, various Jewish groups, and various non-Jewish Middle Eastern groups will be represented. That is the only way to ascertain the ancestral components of the various Jewish groups. Moreover, such an analysis would establish the extent of the common genomic element between the various Jewish groups, which -so far- has been established for a limited number of Y-chromosome and mtDNA lineages.
UPDATE: While a formal admixture analysis is not performed, the EIGENSOFT plot is suggestive of what common sense would dictate, namely that Ashkenazi Jews (reds) are intermediate between a native Near Eastern group (the Druze) and Europeans. Unfortunately the inclusion of the Mozabites (off the chart to the left) who have substantial Sub-Saharan ancestry, makes the resolution of the visible part of the chart less than desirable.
Genome Biology doi:10.1186/gb-2009-10-1-r7
A genome-wide genetic signature of Jewish ancestry perfectly separates individuals with and without full Jewish ancestry in a large random sample of European Americans
Anna C Need et al.
It was recently shown that the genetic distinction between self-identified Ashkenazi Jewish and non-Jewish individuals is a prominent component of genome-wide patterns of genetic variation in European Americans. No study however has yet assessed how accurately self-identified (Ashkenazi) Jewish ancestry can be inferred from genomic information, nor whether the degree of Jewish ancestry can be inferred among individuals with fewer than four Jewish grandparents.
Using a principal components analysis, we found that the individuals with full Jewish ancestry formed a clearly distinct cluster from those individuals with no Jewish ancestry. Using the position on the first principal component axis, every single individual with self-reported full Jewish ancestry had a higher score than any individual with no Jewish ancestry.
Here we show that within Americans of European ancestry there is a perfect genetic corollary of Jewish ancestry which, in principle, would permit near perfect genetic inference of Ashkenazi Jewish ancestry. In fact, even subjects with a single Jewish grandparent can be statistically distinguished from those without Jewish ancestry. We also found that subjects with Jewish ancestry were slightly more heterozygous than the subjects with no Jewish ancestry, suggesting that the genetic distinction between Jews and non-Jews may be more attributable to a Near-Eastern origin for Jewish populations than to population bottlenecks.Link (pdf)