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).
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.
This hypothesis was first tested by prof. Karl Skorecki and collaborators from Haifa, Israel. In their study [1] (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 corrobated the findings [1]. This lead to the development of the Cohen Modal Haplotype, a set of Y-chromosomal markers that might have been shared by the Biblical Aaron.
Understandably, the finding led to a lot of excitement in religious circles, providing some "proof" of the historical veracity of the Bible [1] [1], leading to criticism [1].
Other criticism might be that, according to the logic of Skorecki et al, all Jews should share the same Y chromosome. After all, Aaron and Moses descended patrilineally from Jacob, the ancestor of all Jews (see, however conversion). The differences potentially accrued by recombination between Jacob and Moses/Aaron (5 generations) would have been lost in the many generations that separate Aaron and the present Kohanim.
The Cohen Modal Haplotype has been identified in groups of non-Jews, notably the Lemba of Southern Africa [1] and groups of Kurds.Background
Proving the hypothesis
Criticism