Your Great Grandmother Within

A new genetic study on the origins of Ashkenazi Jewry finds that 40% of Ashkenazi jews alive today, are the descendants of just 4 women! It's relatively easy to look at maternal lineages. In the same way that the Y chromosome is only inherited from fathers, a small loop of 'mitochrondrial DNA' is inherited only from fathers. Which means that in the absence of mutation, you share the same mitochondrial DNA as your great grandmothers great grandmother.

Ashkenazi jews are already known to fall into a number of distinct genetic groups, two of which represent 42% of the population. When the authors looked at the DNA sequence of those two groups, they found evidence for just four types of original mitochrondrial DNA, meaning that just four women gave rise to almost half of the Ashkenazi jewish population. Amazingly, one of the four DNA types is present in 1,700,000 living Ashkenazi jews - 10% of jews today can trace their origins to the same woman.

One of the authors on the study was Karl Skorecki from Tel Aviv University, who published an even more astonishing paper several years ago demonstrating that about 90% of self-identified Cohanim share a Y chromosome type. This would be expected if indeed todays Cohanim are descendants of Aaron, brother of Moses.