Posted by
Mike on Sunday, April 26, 2009 2:13:06 PM
http://westernperspective.blogspot.com/
The question of the genetic origin of the Ashkenazim of Central and Eastern Europe has long been a topic of debate. This raises the question of whether scientific data is being manipulated to prove preconceived notions or theories.
Arthur Koestler's belief that the Ashkenazim are descended from the Asian tribe of Khazars was once accepted as true. One study purportedly demonstrated that Ashkenazi Jews were less likely to be descended from Middle Eastern ancestors than were Europeans in the aggregate. This distortion obviously led to much confusion as new scietific evidence became available.
The most recent studies of Y-chromosome DNA confirm that the Ashkenazim are more likely descended paternally from Middle Eastern ancestors, with about 12.5% of European or Central Asian descent. Based upon mtDNA studies, it had been thought that the Ashkenizim originated from male Jews from the Middle East perhaps coming as traders and having offspring with local Eastern European women, inasmuch as it could not be determined precisely where the female ancestors were from, although it appeared that there were many different origins. Later studies in Israel tend to establish that like the male ancestors, the female ancestors also came from the Middle East and that about 40% of the present day Ashkenazim descend from just four founding mothers of Middle Eastern origin, and the remaining 60% being more likely of Middle Eastern descent as well. This tends to agree with the changing definition of Jewishness based upon descent from the mother at the time of settlement.
Among rabbinical descendants, it is noteworthy that the Cohanim priesthood does apparently descend paternally from a single Middle Eastern ancestor corresponding to Aaron the brother of Moses. The Levitical priesthood among the Ashkenazim, on the other hand, is over 50% descended paternally from the local European population, probably due to the descendants of an early single male ancestor who was a convert to Judaism.
None of this is conclusive with regard to the total genetic makeup, which could be more or less of European or other descent, because the markers determining paternal or maternal ancestry only make up a small part of the total DNA. In this regard, it could be that Jewish children with some European descent were more likely to become converts to Christianity in Europe, so that their non-Middle Eastern genes were not as likely to show up later in the gene pool.