DNA – the kohein link

Can it be that deep in our ancestors’  bodies, hidden in their cells, silent  historians recorded the dead secrets of  our past? 

Over ten years ago, longtime  nephrologist and medical researcher  Dr. Kalman Skorecki was davening  Shacharis in his Toronto shul when a  kohein was called up to the fi rst aliyah  of Krias HaTorah. As he watched the  kohein striding up the bimah steps, a  strange idea fell into Dr. Skorecki’s  mind.

I am a kohein and he is a kohein,  he thought to himself. Even though my  parents are from Eastern Europe and his  parents are from Morocco, we have a  common bond that transcends geography  – we are both direct descendants of  Aharon HaKohein. Could it be that  this link has somehow been physically  preserved? Could it be that the common  bond between us is upheld not only  by tradition, but is also a physical fact  readily identifiable in the test tube and  microscope?

On the face of it, such an idea would  seem preposterous. True, a son often  looks like his father, and grandsons  sometimes look like their zeidies, but  after many generations, what chance  is there that kohanim could have any  characteristic linking them to their  forefather, Aharon, who lived so many  generations ago?

However, as a doctor and researcher,  Dr. Kalman realized that it was not only  possible, but even likely, that a physical  bond existed, since deep within every  cell of the human body are structures  that determine not only every detail  of our physical and mental being, but  also harbor secrets of the distant past.  Anchored in these microscopic structures  are many secrets of human ancestry.  These mysterious constructs are our  chromosomes and genes.

For centuries, savants and researchers  agonized over how information is passed  from parent to child. Why does a whale  grow into a whale and not into a mouse?  Why do children generally have two ears  like their parents and not sprout an extra  one or two of these useful appendages?

The Genetic Age broke on February  28, 5713/1953, when two English  researchers, Francis Crick and James  Watson discovered the “secret of life.”  After years of effort they had figured  out the shape of DNA (deoxyribonucleic  acid), a structure so long that to fit into  our tiny cells it wraps itself into a tiny  bundle.

It took Crick another four years  to figure out DNA’s brilliant code.  Basically, DNA is composed of four  molecules represented by the letters A,  C, G, and T, each one called a nucleotide.  Each of our cells contains the human  genome, which consists of three billion  nucleotides packed into 23 pairs of  chromosomes. Just as a computer can  record millions of facts simply through  endless rows of ones and zeros, so these  billions of nucleotides, in their endless  combinations and permutations, record  everything about us and transmit it to  future generations, from the color of our  eyes to our level of intelligence. 

There are two intriguing facts about  this incredible letter sequence that  encodes our body structure and function  from the cradle to the grave. First of all,  the genome code is virtually identical for  all members of the human population.  Broadly speaking the whole human race  is made up of identical twins regarding  99.9% of their make-up. The vast human  diversity regarding skin color, height,  nose size and length is determined by  the puny 0.1% that makes Tom different  than Dick and Harry.

Secondly, only a small percentage of  the genome’s three billion nucleotides  transmit useful information. The rest of  the sequence, known as “junk DNA,”  has no obvious effect on the body at all.  Because of this lack of obvious function,  junk DNA has one important practical  use – scientists have discovered that  specifically because of its “uselessness,”  it serves as a faithful record of a person’s  ancestry. Why is this?

Useful DNA needs to remain in  perfect working order in order to serve as  an accurate blueprint of the human body.  Any blurb in the DNA sequence can  wreak havoc on the human body, causing  genetic flaws and terrible diseases such  as Tay-Sachs.

Junk DNA is different. Since it  serves no obvious purpose, its sequences  often undergo changes that have no  detrimental effect on the organism.  These changes are then passed down  through the generations and provide  evidence of one’s distant ancestry. Let’s  say certain links in Mr. Sam Levi’s DNA  chain got mixed up five generations ago.  These changes can sometimes pass on  to his children and great grandchildren,  branding them forever more as his  descendants.

Dr. Skorecki considered it likely that  Aharon HaKohein had such markers,  which would have been passed down to  the approximately 350,000 kohanim of  our time.

The problem is that children  generally have a combination of their  parents’ DNA. Modern day kohanim  are the progeny not only of Aharon, but  of all the thousands of wives kohanim  have married throughout history. Is  there any DNA that retained Aharon’s  stamp without the input of these endless  marriages?

There was! Among the human cell’s  46 chromosomes (DNA bundles) is the  Y chromosome that is possessed only by  males. No woman since creation has had  a Y chromosome in her genome. Every  father bequeaths his sons with an exact  copy of his Y chromosome, free from  female influence. When Aharon had a  son, this son received an exact copy of  Aharon’s Y chromosome. Therefore,  since kehunah passes exclusively down  the male line, it stands to reason that  every kohein alive in our day possesses an  exact copy of Aharon’s Y chromosome.

But how to determine whether the  Y chromosome of modern day Sam  Cohen is the same as Aharon’s? Is there  some way to differentiate between the  Y chromosomes of Tom, Dick and  Harry? As mentioned earlier, there is! If  the junk DNA of all modern kohanim’s  Y chromosome is found to possess  aberrations common to all, this would  prove that they all had a common  male ancestor, presumably Aharon  HaKohein.

At the conclusion of two studies, Dr.  Skorecki’s efforts were crowned with  success. After investigating a number  of kohanim by painlessly scraping off  some cells from the inner cheek, it was  discovered that almost all of them shared  six unique chromosome markers in the  Y cell; 97 of 106 kohanim tested showed  this common bond back to a single  ancestor. These six markers are now  known as the Cohen Modal Halotype  (CMH).

On top of that, scientific evidence  indicates this marker extends back  106 generations, or 3,300 years, the  time when the Jews left Egypt. And  since Avrohom Avinu was only seven  generations before Aharon, this CMH  marker may also be the genetic marker  of the first Jew!

Ongoing research revealed that over  80% of contemporary kohanim possess  the CMH marker, while the kohanim  of the Tunisian island of Djerba have a  100% percent rating, leading Dr. Kalman  Skorecki to conclude that:

“The oral tradition of the priesthood  has a DNA or genetic counterpart. The  scientific information confirms that the  majority of contemporary Jewish males  who identify themselves as kohanim  are descended from a common male  ancestor who founded a patrilineal  dynasty consistent with the tradition of  the Jewish priesthood.

“It’s almost equivalent to finding a  remnant of the garb of the first priest’s  family, as if you went to Sinai and found  some remnant of Aharon’s anointment  ceremony.”

Regarding kohahim who do not have  these genetic markers, Rav Yaakov  Kleiman, author of “DNA and Tradition,”  emphasizes that for various reasons  these scientific findings have no halachic  significance whatsoever.

“At present there are no halachic  ramifications from these discoveries,” he  writes. “No one is certified nor disqualified  because of their Y-Chromosome  markers.” 

Encouraged by the success of the so  called “Kohein Gene,” researchers in the  USA, England and Israel turned their  attention to investigating the origins of  world Jewry. Could it be demonstrated that  Jews worldwide have a common origin  in the Middle East whose traces have  survived two thousand years of exile?  Investigation of the Y-Chromosome  and genetic signatures of 29 population  groups including seven Jewish groups  revealed that Jews from the Near East and  Ashkenazim had almost identical genetic  profiles despite Ashkenazi Jews separating  from their eastern cousins about 1,200  years ago.

This led Professor Michael Hammer  of the University of Arizona to comment  that:

“Despite their long term residence  in different countries and isolation from  one another, most Jewish populations  were not significantly different from one  another at the genetic level. The results  support the hypothesis that the paternal  gene pools of Jewish communities from  Europe, North Africa and the Middle  East descended from a common Middle  Eastern population and suggest that  most Jewish communities have remained  relatively isolated from neighboring non-  Jewish communities during and after the  Diaspora.”

But if so, you might ask, why do  many Jews look like the residents of their  adopted countries? Why do German Jews  look like Germans and Moroccan Jews  look like Moroccans?

According to the Vilna Gaon, much of  the physical traits of nations are dependant  on their particular geography and weather.  For example, those that live in sunnier  climates will be darker than those that live  in colder climates. So it is possible that  after living in a particular area for hundreds  of years, we may have developed different  physical appearances.

Another answer is that it has been  estimated that in the course of the 50  generations of European Jewry, the  influx of converts is about 0.5% in each  generation. This is sufficient to account  for the Jews’ resemblance to the non-Jews  of their host countries, while allowing a  distinctively Jewish genetic profile to  survive.

We are all linked by an invisible  thread.

(Source: Kleiman, Rabbi Yaakov.  DNA & Tradition, the Genetic Link to the  Ancient Hebrews. Devorah Publishing,  2007.)

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