Mitochondrial Eves

The JPost reports:

[F]our Jewish "founding mothers" who lived in Europe 1,000 years ago have been credited with being the ancestors of nearly half of all Ashkenazi Jews, who constitute the majority of the current Jewish population.
About 3.5 million people - or 40 percent of Ashkenazi Jews currently alive - are descended from these matriarchs, who were among a small group, probably after migrating from the Middle East, according to the Israeli researchers, who also provide evidence of shared maternal ancestry between Ashkenazi and non-Ashkenazi (Sephardi and Oriental) Jews.

Interesting -- although hardly surprising, because, as we noted (quoting an article in the Atlantic) last time we discussed the Jewish ancestry issue,

20 percent of the adult Europeans alive in 1000 would turn out to be the ancestors of no one living today (that is, they had no children or all their descendants eventually died childless); each of the remaining 80 percent would turn out to be a direct ancestor of every European living today....

and you can most likely say something similar about Ashkenazi Jewry. At the same time, I noted that the same article claimed that the most recent common ancestor of all Europeans lived about 600 years ago; since I'm no scientist, maybe someone can help me out here -- what, if anything, does the latest research imply about the most recent common ancestor of Ashkenazi Jewry?

UPDATE: Another question for the more scientifically inclined: how does this latest research square with this?