questioning the "cohen gene" #dna


Joan Hartman <joanhartman@...>
 

Does anyone have any science-based response to the following paraphrase
from an anthropology blog, which challenges the conventional understanding
of the "cohen gene" (the blog is written anonymously so I cannot evaluate
the author's credentials):

"One of the first applications of Y-chromosome testing was the discovery
that Jewish Cohanim exhibited a particular Y-chromosome haplotype, called
the Cohen Modal Haplotype (CMH). The first letter announcing this discovery
(www.familytreedna.com/nature97385.html) showed a spectacular difference
between Cohanim and non-Cohanim. The Cohanim had trace frequencies of
haplogroup E3b, and a particular DYS19 allele at high frequency. While this
finding proved different histories for priests and non-priests, it did not
prove descent >from a single individual because the YAP- DYS19B combination
is not a monophyletic lineage. (If two men have the same haplotype, it
does not mean that they are descended >from the same ancestor. This is due
to the fact that microsatellites defining haplotypes mutate quite fast, so
two unrelated men may have the same haplotype by chance. The probability of
this increases as the number of microsatellites decreases.) In another
study
(www.journals.uchicago.edu/AJHG/journal/issues/v66n2/990488/990488.html),
the authors discovered a more extended version of the same haplotype
(DYS19-14, DYS388-16, DYS390-23, DYS391-10, DYS392-11, DYS393-12) at high
frequencies.

The Cohen modal haplotype belongs to a Y-chromosome haplogroup called J (or
HG-9). A haplogroup is defined by a unique event polymorphism, and men who
belong to the same haplogroup are indeed descended >from a single man. But,
in the case of J, that single man lived more than 10,000 years ago, long
before the time of Aaron. However, J is split into two lineages that are
also more than 10,000 years old: J2 (or Eu9) and J1 (or Eu10). If people
who have the CMH are always in just one of these groups -- either only in
J1 or only in J2 -- then the CMH could reflect descent >from a single
individual. But, if it is found in both, then by definition the CMH could
not reflect descent >from Aaron, because he lived approximately 3500 years
ago, much after the common ancestor of J1 and J2. Both groups can't be
descended >from Aaron. In this study
(bioanthropology.huji.ac.il/pdf/Nebel_2001b.pdf), 22 out of 25 individuals
with the CMH belonged to J1. But the appendix of the same study shows that
haplotype 108 is also part of the CMH, but haplotype 108 belongs to
haplogroup J2. In another study
(www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11592923&dopt=Abstract)
the authors state that: "By typing a limited number of Italian Cohanim for
the STRs used here, we determined" that the CMH "does indeed belong to
network 1.2." Network 1.2 falls under the J2 haplogroup. In the
supplementary materials of the following comprehensive article on Ashkenazi
Jewish Y-chromosome variation, 28 of the Jewish CMHs belong to J1 and 25
belong to J2.
(www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14740294&dopt=Abstract)

Note that in Anatolia, in region 6 (south), 12% of the population belongs
to the
J1-CMH. (hpgl.stanford.edu/publications/HG_2004_v114_p127-148.pdf). Among
Armenians in the West region, the CMH frequency is
4.4%. (www.ucl.ac.uk/tcga/tcgapdf/Weale-HG-01-Armenia.pdf).

Thus, several studies have now shown that the CMH occurs among Jews in both
J1 and J2 and does not represent a single lineage. More importantly, the
CMH was first identified because of its high frequency compared to other
haplotypes. The strength of this evidence is diminished by the finding that
CMH chromosomes belong to two unrelated lineages. Furthermore, the dating
of CMH chromosomes to Aaron's time should be reconsidered, and the
molecular variation within J1 and J2-background CMH and its neighbors
should be considered separately. In conclusion, the true genetic identity
of Aaron remains elusive."

Joan Hartman


Deb Katz
 

On 2006.07.11 Joan Hartman <joanhartman@ameritech.net> asked:

Does anyone have any science-based response to [...] an anthropology
blog, which challenges the conventional understanding of the "cohen
gene" (the blog is written anonymously so I cannot evaluate the author's
credentials)
from everything I've read and understand---which is extensive and includes
most of the scientific papers on the subject---the information in the blog
you quoted is fairly accurate. The thing is, it looks like cohanim Jews of
either haplogroup are very much more likely to have the CMH than non-cohanim
Jews and non-Jews...so even though the CMH may have arisen independently in
both haplgroups, there is some kind of connection...and for my money the
connection is geographic and cultural, i.e. for several thousands of years,
the J1's and J2's who developed the CMH were hanging out together...in the
middle east.

As it happens, I have three lineages (one J1f and two J2*) with the CMH...
although only one retained a tradition of cohanim descent. (one of the J2*s)

My best guess theory based on the facts so far is that all priests did not
descend >from one man...but rather >from numerous men (including likely
"Aaron" and his paternal relatives as well as others of the era who may have
"bought" their way into the preisthood or gotten there by other means).
Thus, I don't think the CMH's time to a common ancestor is far off...2500 to
3500 years ago is probably about right. The whole issue of how to
accurately date TMRCA of Y-dna matches is subject to hot debate...in time
they will figure this out and get a better handle on what other genetic
distinctions cohanim may share (i.e. fine tune the CMH) and we will get our
answer.

Debbie Katz
Los Altos CA


CherylSimani <cherylsimani@...>
 

Have you read this article?
http://www.jogg.info/11/coffman.htm
It is an interesting summary. However, keep in mind
that this a new and dynamic field of study.

Cheryl Simani
Sender: CherylSimani <cherylsimani@yahoo.com>


Joan Hartman <joanhartman@...>
 

Thanks for responding. Just to clarify, currently, Jews are mostly found
in haplogroup J. As I understand it, a haplogroup is defined as a pattern
of Y chromosomes that shares a unique mutation(s) but varies in the number
of copies of short sequences of bases that are inherited together. As I
understand it (and I am no scientist), haplogroup J is differentiated >from
other haplogroups by one mutation ("M304") . Haplogroup J is in turn
divided into two sub-haplogroups, J1 and J2. Sub-haplogroup J1 is defined
by another mutation ("M267"). Subhaplogroup J2 is defined by yet a third
mutation ("M172") Apparently the current thinking is that J1 and J2
separated well over 10,000 years ago. What I am trying to understand is
how, >from a scientific and genetic perspective, the cohen modal haplotype
-- which is just a pattern of six defined regions of DNA containing a set
number of copies of short sequences of bases which are inherited together
-- could have independently developed among a tribe of proto-priests who
fall into two completely different sub-haplogroups, J1 and J2, each of
which is over 10,000 years old. Unless I completely misunderstand the
science, the odds of this happening seem very small. (And if the cohen
modal haplotype predates the J1/J2 split, wouldn't we find it more widely
distributed in the population?) Even if you were to assume that this
random pattern could have arisen at the same time, 3500 years ago, in two
such men among the group of proto-priests of which Aaron was a member, how
could we then explain the fact that a far greater percentage of the
population of a region of southern Anatolia (12%) has the cohen modal
haplotype than do Jews?

Joan Hartman
Sender: Joan Hartman <joanhartman@ameritech.net>


susana mead <shofar-1@...>
 

On 2006.07.14, Debbie Katz <dkbk@sbcglobal.net> wrote:

As it happens, I have three lineages (one J1f and two J2*) with
the CMH... although only one retained a tradition of cohanim descent.
(one of the J2*s)
Shabbat shalom, Debbie,

Could you clarify for me how can one have two haplogroups? I was under
the impression one only have one (mine is J for instance). You mentioned
having J1 and J2. Also, is the CMH only found among the J?

Shoshana Mead
Sender: Susana Mead <shofar-1@hotmail.com>