Y-chromosomal Aaron
Since the appearance in the 1990s of some relevant publications, there have been attempts to identify the Y-chromosomal Aaron. Aaron was the brother of Moses, the first Kohen (priestly caste in Judaism).
Background
In genetics it is understood that every male inherits 23 chromosomes from either parent, but the Y chromosome always from the father and the mitochondrial DNA (mtDNA) always from the mother.
As membership of the Jewish priesthood caste is patrilineal, it can be hypothetised that all people claiming to be a kohen should share the same Y chromosome.
Proving the hypothesis
This hypothesis was first tested by Prof. Karl Skorecki and collaborators from Haifa, Israel. In their study (Nature 1997;385:32) it was discovered that many Kohanim share certain Y-chromosome markers, which argues in favor of the hypothesis. Other studies have corroborated the findings . This led to the development of the Cohen Modal Haplotype, a set of Y-chromosomal markers that might have been shared by the Biblical Aaron.
Criticism
Understandably, the finding led to a lot of excitement in religious circles, providing some "proof" of the historical veracity of the Bible , leading to criticism .
One might argue that all Jews should share the same Y chromosome. After all, Aaron and Moses descended patrilineally from Jacob, the ancestor of all Jews. However conversion as a source of distinct genetic material and the special status of the Cohen family (Kohanim) among the Jews mitigate against the expectation that all Jews should share the same Y chromosome. Converts can never be part of the Kohanim, a status which is passed from father to son only, whereas status as a Jew is based upon the mother only. So all members of the Kohanim are Kohanim based upon the father and Jews based upon the mother.
The Cohen Modal Haplotype has been also been found in groups of non-Jews, notably the Lemba of Southern Africa and groups of Kurds.
See also
