Thus, it became necessary to find a more stringent characterization of Cohen Y-chromosomes that would represent true founder effects in that population. The new paper seems to identify at least two such lineages, one in J-P58, which is a subset of J1, and one in J2a-M410*, and estimates that they were founded 3.2 and 4.2 thousand years ago.
I will comment on this further when I get a hold of the paper and supplementary material.
UPDATE: The authors use the evolutionary mutation rate, and thus the presented ages are overestimated significantly. However, there are reasons to doubt the germline-rate estimate of about 1,000 years for the J1 lineage:
- Demographic plausibility of growth to encompass nearly a third the Cohanim in about 1,000 years. I am not sure what the demic size of Cohanim is, but going from 1 individual to the current population size would require a consistent high growth over many generations. This seems implausible, unless there is indeed historical evidence for such a Cohen founder's descendants extraordinary success.
- The presence of the founding lineage in both Ashkenazim and Sephardim may suggest a common ancestor before the separation of these two populations.
Pinpointing Jewish priestly founders to specific individuals, including Biblical ones, is not easy, as the Y-STR technology does not allow for anything resembling accurate age estimation. However, the paper is a welcome new study of a much-discussed topic, and adds significantly to our understanding.
UPDATE II: On the other hand, the J-P58* haplogroup was found in 325 of 2,099 non-Jews surveyed, but the extended Cohen Modal Haplotype (eCMH) in none (Table S2). If the eCMH founder lived 3+ kya, it would be strange indeed if he left no non-Jewish descendants, as it would imply zero conversion from that lineage to other religions. The lack of non-Jewish eCMHs does support the "Jewishness" of this lineage, but on the other hand, makes a very old age more difficult to accept.
My guess is that the eCMH founder lived in Roman times. This would simultaneously allow enough time to explain the lineage's geographical and demographic growth, while also explaining its limited penetration to non-Jewish populations.
Human Genetics doi:10.1007/s00439-009-0727-5
Extended Y chromosome haplotypes resolve multiple and unique lineages of the Jewish priesthood
Michael F. Hammer et al.
It has been known for over a decade that a majority of men who self report as members of the Jewish priesthood (Cohanim) carry a characteristic Y chromosome haplotype termed the Cohen Modal Haplotype (CMH). The CMH has since been used to trace putative Jewish ancestral origins of various populations. However, the limited number of binary and STR Y chromosome markers used previously did not provide the phylogenetic resolution needed to infer the number of independent paternal lineages that are encompassed within the Cohanim or their coalescence times. Accordingly, we have genotyped 75 binary markers and 12 Y-STRs in a sample of 215 Cohanim from diverse Jewish communities, 1,575 Jewish men from across the range of the Jewish Diaspora, and 2,099 non-Jewish men from the Near East, Europe, Central Asia, and India. While Cohanim from diverse backgrounds carry a total of 21 Y chromosome haplogroups, 5 haplogroups account for 79.5% of Cohanim Y chromosomes. The most frequent Cohanim lineage (46.1%) is marked by the recently reported P58 T->C mutation, which is prevalent in the Near East. Based on genotypes at 12 Y-STRs, we identify an extended CMH on the J-P58* background that predominates in both Ashkenazi and non-Ashkenazi Cohanim and is remarkably absent in non-Jews. The estimated divergence time of this lineage based on 17 STRs is 3,190 ± 1,090 years. Notably, the second most frequent Cohanim lineage (J-M410*, 14.4%) contains an extended modal haplotype that is also limited to Ashkenazi and non-Ashkenazi Cohanim and is estimated to be 4.2 ± 1.3 ky old. These results support the hypothesis of a common origin of the CMH in the Near East well before the dispersion of the Jewish people into separate communities, and indicate that the majority of contemporary Jewish priests descend from a limited number of paternal lineages.
Electronic supplementary material The online version of this article (doi:10.1007/s00439-009-0727-5) contains supplementary material, which is available to authorized users.