"The Jewish community has been the focus of extensive genetic study over the past decade in an attempt to better understand the origins of this group. In particular, those descended from Northwestern and Eastern European Jewish groups, known as “Ashkenazim,” have been the subject of numerous DNA studies examining both the Y chromosome and mitochondrial genetic evidence.

The focus of the present study is to analyze and reassess Ashkenazi results obtained by DNA researchers and synthesize them into a coherent picture of Jewish genetics, interweaving historical evidence in order to obtain a more accurate depiction of the complex genetic history of this group. Many of the DNA studies on Ashkenazim fail to adequately address the complexity of the genetic evidence, in particular, the significant genetic contribution of European and Central Asian peoples in the makeup of the contemporary Ashkenazi population.

One important contribution to Ashkenazi DNA appears to have originated with the Khazars, an ancient people of probable Central Asian stock that lived in southern
Russia during the 8th-12th centuries CE. Significant inflow of genes from European host populations over the centuries is also supported by the DNA evidence. The present study analyzes not only the Middle Eastern component of Ashkenazi ancestry, but also the genetic contribution from European and Central Asian sources that appear to have had an important impact on Ashkenazi ancestry."