Y-chromosomal Aaron

Y-chromosomal Aaron is the name given to the hypothesised ancestor of the Kohanim, a patrilineal priestly caste in Judaism. In Scripture, this ancestor is identified as Aaron, the brother of Moses. This has come about since the appearance in the 1990s of some relevant publications, relevent to the patrilineal ancestor of all humans, Y-chromosomal Adam.

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 (1997) it was discovered that many Kohanim share certain Y-chromosome markers, which argues in favor of the hypothesis. Other studies (Thomas MG et al, 1998) 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 [1] (http://www.geocities.com/hrhdavid/English/frames/index.html) [2] (http://www.aish.com/societywork/sciencenature/the_cohanim_-_dna_connection.asp), leading to criticism [3] (http://www.ariga.com/genes.shtml).

One might argue that from the premise of the study, 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 (Thomas MG et al 2000) and groups of Kurds.

References

Skorecki K, Selig S, Blazer S, Bradman R, Bradman N, Waburton PJ, Ismajlowicz M, Hammer MF. Y chromosomes of Jewish priests. Nature 1997;385:32. Medline abstract (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8985243) (PMID 8985243).
Thomas MG, Skorecki K, Ben-Ami H, Parfitt T, Bradman N, Goldstein DB. Origins of Old Testament priests. Nature 1998;394:138-40. Medline abstract (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9671297) (PMID 9671297).
Thomas MG, Parfitt T, Weiss DA, Skorecki K, Wilson JF, le Roux M, Bradman N, Goldstein DB. Y chromosomes traveling south: the cohen modal haplotype and the origins of the Lemba--the "Black Jews of Southern Africa". Am J Hum Genet 2000;66:674-86. Medline abstract (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10677325) (PMID 10677325).

External links

A summary of Jewish & Kohanim genetic research papers (http://www.khazaria.com/genetics/abstracts.html)

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