Friday, August 14, 2009

R1b1b2 Cohanim

A new paper by Hammer et al. (Extended Y chromosome haplotypes resolve multiple and unique lineages of the Jewish priesthood) focuses on the J-P58* lineage among Jewish priests (Cohanim). But the paper adds some data to the understanding of R1b1b2 also.

Among the 215 Cohanim haplotypes published in the paper, 13 are R1b1b2 (one is mis-identified as R-P25). The paper doesn't treat these R1b1b2 in a detailed manner, and I think reaches a suspect conclusion:

In contrast, our
network and divergence time analyses suggest that R-M269
chromosomes entered the Cohanim population via several
“migration” events, and do not represent a single Cohanim
founding lineage. For example, divergence time estimates
are much older for Cohanim R-M269 chromosomes (>10
kyears) than for the three Cohanim lineages in haplogroup J
discussed above, and median-joining networks of Cohanim
R-M269 chromosomes lack a modal haplotype and show
many unrelated singleton haplotypes that are interspersed
among Cohanim and non-Jewish samples (Figure S4).
However, a closer look at the R1b1b2 data from the paper is revealing

First, take a look at a table of pairwise genetic distances for the 13 haplotypes. I color-coded the GD values, so the red ones are the most closely related. You can quite easily see that there are two clusters of R1b1b2 Cohanim, with the first cluster having six haplotypes and the second cluster having three.

The first cluster is older (with a TMRCA of around 1600 years ago, or about 400 A.D.) By most accounts of Jewish history, the MRCA for this cluster was either contemporaneous with or slightly pre-dated the largest diaspora movements. The second cluster appears younger (maybe 1200 AD). Both of these clusters have members in the Jewish R1b project at FTDNA, so more detailed analysis with longer haplotypes should be possible. Both clusters are likely R1b1b2a* (aka R-L23).

Another phenomena comes from a graphic representation of the GD between pairs of haplotypes. For this comparison I show three series.

Look at the red series first. This represents 100 men chosen at random from the general R1b project at FTDNA. It shows a relatively smooth distribution, peaking at a GD of 8. In other words, the modal distance between two random haplotypes using the same 22 markers as the Hammer paper is 8.

Next, look at the blue series. These are the 13 R1b1b2 Cohanim from the new paper. Their distribution has some significant differences. One is a substantial excess of closely related haplotypes. This means that the R1b1b2 Cohanim are not merely or entirely the result of some random admixture, but rather that a significant fraction of the Cohanim R1b1b2 lineages have pre-diaspora or diaspora-era connections.

A second difference is the second, larger peak at a GD of 11. This is reflecting an early seperation of R1b1b2 lineages around 4,400 years ago, most probably in the Near East. You can also see this in the green series, which shows the GD distribution of all the Cohanim/non-Cohanim pairs (1300 pairs, in fact). The Cohanim are more distant from random R1b1b2 European men (on average) than R1b1b2 European men are from each other. This reflects the fact that 80% of the Cohanim men appear to be L23+ L51- while most European men (the 100 "random" ones mentioned earlier) are not only L51+ but also L11+ and either P312+ or U106+.

7 comments:

Čtenář said...

If the first older cluster has a TMRCA of around 1600 years ago and is probably L23* then have we here any clear assumption about its origin in Levant? Or it would be more safe to predict some relationship with Jews in Diaspora?

Aharon Yosef (Athol) said...

Keep up the good work. This is a wonderful post on R1b Cohanim.

geoff said...

Vincent. I think you are brilliant.The sons of the servants of Solomon were assigned duties with the Levites on their return to Judea. Well before that Joshua and David assigned the Jebusites to Temple duties.The first mentioned where probably sent by King Hiram skilled men to help with building the first temple.The second lot mentioned a tribe of Caananites who fooled Joshua.They at first not allowed to marry into the Coehnin. Geoff.

nordn8 said...
This comment has been removed by the author.
nordn8 said...

Wouldn't an adoption of an infant and raising it as their own solve any questions about R1b entering the J1 gene pool of the kehuna?

Aharon said...

No it wouldn't as an adopted child does not have the right to be classified as a cohen unless his real father was also a cohen.

Nicole Czarnecki said...

So, is R1b1b2 exclusively Cohanate or did it enter the Cohanate lines as R1a1a1 entered Ashkenazi Levite lines?