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
He considered 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
Dr. Skorecki 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 background.
The results 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 on non-Kohanim.
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 in 10,000.
The finding 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.
Professor Hammer 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
Calculations 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 faithfulness.
Wider genetic 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.
This genetic 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
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
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
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
Many individual 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
The research, 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 G-d surely His promises.
May we soon see Kohanim at their
service, Levites on their Temple platform and Israelites at their places.