Wednesday, December 31, 2008

Parenthetical Aside: the congruence of genealogy and (population) genetics

In comments to the previous entry, JR graciously conceded that he is willing to retreat from his earlier assertion that "no member of the Ashkenazim can trace their ancestry to the Middle East" and that he does "not of course have any difficulty with SOME genetic material in modern Jews being of ME origin. My point is that ME genes are only one part of modern Jewish genetics."

I don't have any argument with that last statement. The point to be made is not that the Jews are an exclusively endogamous population, but rather that over millenia of living as a national community both within their own Land and in an extended diaspora, the Jews have maintained as much of a cultural, historical, and biological continuity as any other nation -- if not more so.

The definition of the Jewish people as a nation, rather than as a community of adherents of a particular religion or as a "race" will be taken up, I hope, in my next posting here. But before tackling the comparisons and contrasts beween "Zion" and "Albion," I want to offer a brief aside regarding an uncanny congruence between the recorded genealogical history of the Jewish nation, and the (population) genetic data regarding our contemporary Jewish population.

In the Wikipedia entry on Ashkenazi Jewish genetic origins I quoted in the previous entry, the following statement appears:

Recent research indicates that a significant portion of Ashkenazi maternal ancestry is also likely of Middle Eastern origin. A 2006 study by Behar et al[1], based on haplotype analysis of mitochondrial DNA (mtDNA), suggested that about 40% of the current Ashkenazi population is descended matrilineally from just four women, or "founder lineages", that were "likely from a Hebrew/Levantine mtDNA pool" originating in the Near East in the first and second centuries CE. According to the authors, "the observed global pattern of distribution renders very unlikely the possibility that the four aforementioned founder lineages entered the Ashkenazi mtDNA pool via gene flow from a European host population."

In addition, Behar et al have suggested that the rest of Ashkenazi mtDNA is originated from ~150 women, most of those were probably of Middle Eastern origin.

Both the extent and location of the maternal ancestral deme from which the Ashkenazi Jewry arose remain obscure. Here, using complete sequences of the maternally inherited mitochondrial DNA (mtDNA), we show that close to one-half of Ashkenazi Jews, estimated at 8,000,000 people, can be traced back to only four women carrying distinct mtDNAs that are virtually absent in other populations, with the important exception of low frequencies among non-Ashkenazi Jews. We conclude that four founding mtDNAs, likely of Near Eastern ancestry, underwent major expansion(s) in Europe within the past millennium.[1][17]

The interesting part of that discussion concerns the "four founding mtDNAs, likely of near Eastern ancestry." The original paper can be accessed as a pdf, here.

That a significant proportion of contemporary Jews are descended from four Near Eastern women will not surprise students of the Bible, who will also be able to supply their names: Leah, Rachel, Bilhah, and Zilpah.

To be sure, the Jews have never been an exclusively endogamous population, and the genetic stock of the population has been augmented and refreshed by the introduction of exogamous strains, from the time that Joseph married Asenath, the daughter of the Egyptian cleric Potipherah. It is nonetheless striking that in good agreement with the Bible, the Ashkenazi Jewish population still carries the genetic signatures of four founding matriarchs.