Dr. Skorecki considered, "According
to tradition, this Sefardi and I have a common ancestor. Could
this line have been maintained since Sinai, and throughout the long
exile of the Jewish people?" As a scientist, he wondered, could
such a claim be tested?
Being a nephrologist
and a top-level researcher at the University of Toronto and the Rambam-Technion
Medical Center in Haifa, he was involved in the breakthroughs in molecular
genetics which are revolutionizing medicine and the study of the life-sciences.
He was also aware of the newly developing application of DNA analysis
to the study of history and population diversity.
a hypothesis: if the Kohanim are descendants of one man, they
should have a common set of genetic markers--a common haplotype-- that
of their common ancestor. In our case, Aharon HaKohen.
A genetic marker
is a variation in the nucleotide sequence of the DNA, known as a mutation.
Mutations which occur within genesa part of the DNA which codes
for a proteinusually cause a malfunction or disease, and is lost
due to selection in succeeding generations. However, mutations found
in so-called non-coding regions of the DNA tend to persist.
Since the Y
chromosome, besides for the genes determining maleness, consists almost
entirely of non-coding DNA, it would tend to accumulate mutations. Since
it is passed from father to son without recombination, the genetic information
on a Y chromosome of a man living today is basically the same as that
of his ancient male ancestors, except for the rare mutations that occur
along the hereditary line. A combination of these neutral mutations,
known as a haplotype, can serve as a genetic signature of a mans
male ancestry. Maternal geneaologies are also being studied by means
of the m-DNA (mitrocondrial DNA), which is inherited only from the mother.
then made contact with Professor Michael Hammer, of the University of
Arizona, a leading researcher in molecular genetics and a pioneer in
Y chromosome research. Professor Hammer uses DNA analysis to study the
history of populations, their origins and migrations. His previous research
included work on the origins of the Native American Indians and the
development of the Japanese people.
A study was
undertaken to test the hypothesis. If there were a common ancestor,
the Kohanim should have common genetic markers at a higher frequency
than the general Jewish population.
In the first
study, as reported in the prestigious British science journal, Nature
(January 2, 1997), 188 Jewish males were asked to contribute some cheek
cells from which their DNA was extracted for study. Participants from
Israel, England and North America were asked to identify whether they
were a Kohen, Levi or Israelite, and to identify their family
of the analysis of the Y chromosome markers of the Kohanim and non-Kohanim
were indeed significant. A particular marker, (YAP-) was detected in
98.5 percent of the Kohanim, and in a significantly lower percentage
In a second
study, Dr. Skorecki and associates gathered more DNA samples and expanded
their selection of Y chromosome markers. Solidifying their hypothesis
of the Kohens' common ancestor, they found that a particular array of
six chromosomal markers were found in 97 of the 106 Kohens tested. This
collection of markers has come to be known as the Cohen Modal Haplotype
(CMH)--the standard genetic signature of the Jewish priestly family.
The chances of these findings happening at random is greater than one
of a common set of genetic markers in both Ashkenazi and Sefardi
Kohanim worldwide clearly indicates an origin pre-dating the separate
development of the two communities around 1000 C.E. Date calculation
based on the variation of the mutations among Kohanim today yields
a time frame of 106 generations from the ancestral founder of the line,
some 3,300 years, the approximate time of the Exodus from Egypt, the
lifetime of Aharon HaKohen.
was recently in Israel for the Jewish Genome Conference. He confirmed
that his findings are consistent that over 80 percent of self-identified
Kohanim have a common set of markers. The finding that less than one-third
of the non-Kohen Jews who were tested possess these markers is not surprising
to the geneticists. Jewishness is not defined genetically. Other Y-chromosomes
can enter the Jewish gene pool through conversion or through a non-Jewish
father. Jewish status is determined by the mother. Tribe membership
follows the fathers line.
based on the high rate of genetic similarity of todays Kohanim
resulted in the highest paternity-certainty rate ever recorded
in population genetics studiesa scientific testimony to family
studies of diverse present day Jewish communities show a remarkable
genetic cohesiveness. Jews from Iran, Iraq, Yemen, North Africa and
European Ashkenazim all cluster together with other Semitic groups,
with their origin in the Middle East. A common geographical origin can
be seen for all mainstream Jewish groups studied.
research has clearly refuted the once-current libel that the Ashkenazi
Jews are not related to the ancient Hebrews, but are descendants of
the Kuzar tribe--a pre-10th century Turko-Asian empire which reportedly
converted en masse to Judaism. Researchers compared the DNA signature
of the Ashkenazi Jews against those of Turkish-derived people,
and found no correspondence.
In their second
published paper in Nature (July 9,1998) the researchers included
an unexpected finding. Those Jews in the study who identified themselves
as Levites did not show a common set of markers as did the Kohanim.
The Levites clustered in three groupings, one of them the CMH. According
to tradition, the Levites should also show a genetic signature from
a common patrilineal ancestor.
It is interesting
to note that the tribe of Levi has a history of a lack of quantity.
The census of BaMidbar shows Levi to be the smallest of the tribes.
After the Babylonian exile, the Levites failed to return en masse to
Jerusalem, though urged by Ezra HaSofer to do so. They were therefore
fined by losing their exclusive rights to maaser. Though statistically,
the Levites should be more numerous than Kohanim, today in synagogue,
it is not unusual to have a minyan with a surplus of Kohanim
and yet lack even one Levite. The researchers are now focusing effort
on the study of Levites' genetic make up to learn more about their history
in the Diaspora.
Using the CMH
as a DNA signature of the ancient Hebrews, researchers are pursuing
a hunt for Jewish genes around the world. The search for lost tribes,
whether the biblical 10 Lost Tribes which were uprooted from Eretz
Yisrael by the Assyrians, or other would-be Jews, Hebrews or "chosen
peoples," is not new. Using the genetic markers of the Kohanim
as a yardstick, these genetic archaeologists are using DNA research
discover historical links to the Jewish people.
Kohanim and others have approached the researchers to be tested.
The researchers' policy is that the research is not a test of individuals,
but an examination of the extended family. Having the CMH is not a proof
of one's being a Kohen, for the mother's side is also significant
in determining one's Kohanic status. At present, there are no
halachic ramifications of this discovery. No one is certified
nor disqualified because of their Y chromosome markers.
which began with an idea in shul, has shown a clear genetic relationship
amongst Kohanim and their direct lineage from a common ancestor. The
research findings support the Torah statements that the line of Aharon
will last throughout history. That our Torah tradition is supported
by these findings should be a reinforcement for Kohanim and for all
those who know that the Torah is truth, and that God surely keepsHis promises.
May we soon
see Kohanim at their service, Levites on their Temple platform and Israelites
at their places.