Ketuvot 23b ~ The Cohen Gene

HEllo, I'm Your New Cohen

משנה כתובות דף כג עמוד ב 

וכן שני אנשים, זה אומר כהן אני וזה אומר כהן אני - אינן נאמנין, ובזמן שהן מעידין זה את זה - הרי אלו נאמנין; רבי יהודה אומר: אין מעלין לכהונה על פי עד אחד

Likewise in the case of two men; one says, "I am a Cohen", and the other says "I am a Cohen", they are not believed. If however they testify about one another they are believed. R. Yehuda said: we do not elevate [a person] to the status of Cohen based on the testimony of only one witness....

Being a Cohen comes with rights and duties. They get called to the Torah first, and are given preference to lead Birkat Hamazon.  During Temple times, they got lots and lots of food.  But how do you prove you are a Cohen, and entitled to these privileges?  According to the Mishnah in today's Daf Yomi, (and discussed in detail in the talmudic discussion that follows,) you need witnesses to attest to your status. But what if the Cohen was mistaken about his ancestors? What if the witnesses were being paid to dupe the locals into believing the Cohen was legitimate? Is there an alternative to the methods mentioned in this Mishnah? Perhaps.

The Saturday Night Live Cohen 

My friend Misha Galperin, (the former CEO of the Jewish Federation of Greater Washington and  CEO of International Development at The Jewish Agency) is a Cohen. Only he didn't know it when he arrived in America from the Soviet Union.  Here's what happened, as told to me in a recent email  that he kindly allowed me to share:

Five months after arriving in the US, I am sitting in the lounge of Yeshiva University's dorm watching SNL with my tutor who was teaching me Alef Bet is so I can start classes on Monday. 
A skit starts with guest host Leonard Nimoy dressed as Mr. Spock  - with ears - and  at the end he raises his right palm in the symbolic gesture and says: "Live long and prosper!"
I turn to the tutor and ask him what this gesture means. Why?--he asks. "Because my father taught me this, and his father taught it to him before being murdered by Nazis in 1941. My father did not know what it meant, but he taught me..."

And so Misha learned that he was a Cohen from Saturday Night LiveBut not all Cohanim are so lucky. (Fun fact: Leonard Nimoy ז’ל wrote about his decision to give Mr. Spock this priestly hand salute in his 1997 autobiography I Am Not Spock.)  With neither witnesses nor TV to help, is there another way to establish one's genealogy as a member of the priestly class? That's where the Cohen Gene comes in.  

The Cohen Gene

If all Cohanim are descended from Aaron, and the privilege is only transmitted from father to son, then perhaps being a Cohen can be genetically linked to a chromosome that is only passed from father to son. And there is such a chromosome. It's the Y chromosome, and all (fertile) men carry a copy that comes only from their biological father. (Quick recap: girls are XX and boys are XY. So all girls carry one X chromosome from mum and one X chromosome from dad. Boys, on the other hand, only get their X chromosome from mum, and their Y chromosome from dad. This can lead to other problems like hemophilia, which we've talked about elsewhere.) That's exactly what prompted  Karl Skorecki from the Technion, and colleagues from University College London, to analyze the Y chromosome in Cohanim and compare it to the rest of the Jewish population.  In 1997 they published a paper in Nature that looked at a special bit of the Y chromosome called YAP. Actually, they looked at 6 kinds of the YAP haplotype, (a haplotype being what geneticists call bunches of DNA sequences), and compared their frequency in Cohanim and non-Cohanim.    

Skorecki K, et al. Y Chromosomes of Jewish Priests.  Nature 1997. 385:32.

Skorecki K, et al. Y Chromosomes of Jewish Priests.  Nature 1997. 385:32.

As you can see highlighted, the YAP+ haplotype was found in only 1.5% of those who self-identified as Cohanim, but in over 18% of non-Cohanim.  The different frequency was found in both Ashkenazi and Sephardi Cohanim,  a result that the authors claimed was "consistent with an origin for the Jewish priesthood antedating the division of world Jewry into Ashkenazic and Sephardic communities."

These Y-chromosome haplotype differences confirm a distinct paternal geneology for Jewish priests.
— Skorecki et al. Nature 1997. 385: 32.

David Goldstein, who directs the  Center for Human Genome Variation at Duke University, also published a study on the Y-chromosome of Cohanim, using a sample that included the DNA swabbed "from the mouths of sunbathers on the beaches of Tel Aviv." Here is what Goldstein concluded:

Despite the high levels of variation, we could see a clear difference between Cohen and Israelite chromosomes.  The most common chromosomes observed in the Israelites (that is, non-Cohen and non-Levite Jews) were found in only 12% of the Israelite individuals sampled. By contrast, more that half of the Cohen Y chromosomes were identical at the sites considered - that is, the majority of the self-identified Cohanim had the same type of Y chromosome. Even more remarkable, this same type of Y was found at high frequencies in both Ashkenazi (45%) and Sephardi (56%) Cohanim. (Goldstein, p.31)

Goldstein named this chromosome type the Cohen Modal Haplotype, and claimed that it showed "definitively" that Cohen status was not adopted (i.e. made up by some, eager for the benefits) but inherited.  And now things started to get really interesting. 

Dating the Original Aaron

So all, (OK, not all, but certainly most) of the approximately 500,000 Cohanim alive today seem to have originated from a common ancestor - a primordial Cohen. And just when did he live? Well, by analyzing small differences in the Cohen Modal Haplotype, and assuming that a generation time is 25 years, Goldstein et al. stated (with a confidence interval of 95%) that the origin of the priestly Y chromosome was "sometime during or shortly before the Temple period in Jewish history."

Not So Fast...

OK, a couple of things need to be noted here, before anyone claims that "genetics proves the Bible." First- as Goldstein himself notes in his book, his numbers may be off, by quite a bit:

Permit me here, after what was for me the first - and still one of the few - real thrills of discovery that punctuate the tedium and detail of science, the necessary reality check.  Our results appeared to be a striking confirmation of the oral tradition. It even led to repeated claims in the press that my colleagues and I "found Aaron's Y chromosome." But although three thousand years is our best guess [as to when Primordial Cohen may have lived] the range of possible dates was and is very broad. Given our uncertainty about the ways mutations happen and how fast, we may be off by several hundred years or more in either direction. (Goldstein p.38).

Second, some later work done by Skorecki (he of the Technion 1997 Nature paper) suggests that the class of Cohanim may have had more than one common ancestor.  This work posits that there was not one primordial Cohen, but a few clans of Cohanim, from whom all later Cohanim are descended. (Or more technically stated:"...lineages characterized by the 6 Y-STRs used to define the original Cohen Modal Haplotype are associated with two divergent sub-clades...and thus cannot be assumed to represent a single recently expanding paternal lineage.")

And finally, work from Brigham Young University (and boy, those guys are really into ancestry) reminds anyone looking to do a quick Cohen DNA test to be careful.

The Cohen Modal Haplotype is observed in high frequency within the Cohanim, but also presents with significant incidence in other non-Jewish populations. The occurrence of the CMH in deeply divergent SNP haplogroups also indicates a lack of specificity of the CMH to the ancient Hebrew population. As such, inference of relation to Jewish populations for individuals or groups should be performed with caution when using the original CMH definition, as a false-positive result is likely.  

 "A false positive is likely" - in other words, the test may show you are a Cohen, but really...you aren't. 

Genetic Testing - It's Not Just for Cohanim

And now that a Cohen "Gene" may have been identified, what about the rest of us non-Cohanim? Some have used genetic testing to discover a forgotten heritage or find long-lost cousins.  One rather keen family member of Polonsky rabbinic lineage (claiming in passing to be descended from King David, the Kalonymos family, and Rashi) used the presence of a "relatively rare R-M124 haplotype" on the Y chromosome to confirm a common ancestor and find a new marker that represents "Polonsky rabbinic lineage." (I confess I am jealous. My grandfather drove a black London taxi, and last time I checked, Rashi was not one of my known ancestors.) 

It's Not About Your Ancestors, It's About You

רמב"ם הלכות שמיטה ויובל פרק יג הלכות יב –יג 

ולמה לא זכה לוי בנחלת ארץ ישראל ובביזתה עם אחיו? מפני שהובדל לעבוד את יי לשרתו ולהורות דרכיו הישרים ומשפטיו הצדיקים לרבים שנאמר יורו משפטיך ליעקב ותורתך לישראל, לפיכך הובדלו מדרכי העולם לא עורכין מלחמה כשאר ישראל ולא נוחלין ולא זוכין לעצמן בכח גופן, אלא הם חיל השם שנאמר ברך יי חילו, והוא ברוך הוא זוכה להם, שנאמר: אני חלקך ונחלתך

ולא שבט לוי בלבד אלא כל איש ואיש מכל באי העולם אשר נדבה רוחו אותו והבינו מדע להבדל לעמוד לפני יי לשרתו ולעובדו לדעה את יי והלך ישר כמו שעשהו האלהים ופרק מעל צוארו עול החשבונות הרבים אשר בקשו בני האדם הרי זה נתקדש קדש קדשים. ויהיה יי חלקו ונחלתו לעולם ולעולמי עולמים ויזכה לו בעה"ז דבר המספיק לו כמו שזכה לכהנים ללוים, הרי דוד עליו השלום אומר: יי מנת חלקי וכוסי אתה תומיך גורלי

Why did the Levi'im not receive a portion in the inheritance in Israel and in the spoils of war like their brethren? Because they were set aside to serve God, to minister to Him and to instruct the masses about His just paths and righteous judgments... Therefore they were set apart from the mundane matters of the world. They do not wage war like the remainder of the Jewish people, nor do they receive an inheritance, nor do they acquire for themselves through their physical power. Instead, they are God's legion...and He provides for them...
Not only the tribe of Levi, but any human whose spirit moves him and who understands with his wisdom to set himself aside and stand before God  - to serve Him and minister to Him and to know Him, proceeding justly as God made him, removing from his neck the yoke of the many mundane things which people seek -  that person is sanctified like the Holy of Holies [in the Temple]. God will be his portion and heritage forever and will provide what is sufficient for him in this world, just as He provides for the Cohanim and the Levi'im...

Maimonides, in his Mishnah Torah,  reminds us about what is really important. It's not bringing a witness into town and telling everyone who your ancestors are. And it's not getting a DNA test to prove your stock. It's about searching for religious meaning in a world of materialism.  And that search is open to anyone, woman or man, Jew or not, Cohen, Levi, or even a plain old Yisrael.  

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