If you have a The Cohen Modal Haplotype badge in the Badges section of your dashboard, it means that you match or are close to the historic Cohen Modal Haplotype (CMH). One of the earliest Y-chromosome population genetics studies documented the CMH.
In 1997, Journal Nature published a study that showed that a high percentage of Jewish males who shared an oral tradition of being Cohanim also shared the same Y-chromosome signature. The authors named the highest frequency Y-chromosome signature (haplotype) the Cohen Modal Haplotype.
The 1997 study used 6 STR (short tandem repeat) markers and allowed a maximum of 1 'step' change on any of these 6 markers to be included in the group. We allow a total of 3 differences from the 12 marker profile for the following reasons:
- We have doubled the number of STR markers from 6 to 12.
- Some of the additional markers have a faster mutation rate.
- The original study conservatively rounded the allowable mutations down (from at least 1.5 to 1), which we applaud.
The CMH is found within Haplogroup J-M267 (J1) on the Y-chromosome ancestral tree. Haplogroup J-M267 (J1) is commonly referred to as 'Semitic' or 'Mediterranean' because of its elevated frequency in those areas. However, Haplogroup J-M267's highest frequency (and greatest diversity) is in Iraq and in the Zagros mountain range found in Western Iran.
If you do not have an oral tradition of being a Cohen or of being Jewish, then your Y chromosome is still part of Haplogroup J-M267 (J1). Your deepest ancestor was likely part of the Neolithic farming expansion that began about 9,500 years ago from the Fertile Crescent. When you upgrade to more markers (Y-DNA37, Y-DNA67, or Y-DNA111), your Jewish matches will usually drop away.
Keep in mind that while the CMH was the most frequent haplotype found in Cohanim men, it was not the only haplotype. Therefore, if you have an oral tradition of being Cohanim, then you most likely are genetically a Cohen. If you do not have a tradition of being Cohanim and if your ancestors were Jewish, then you come from the same genetic Gene Pool. While not being directly from the line of Aaron, you could be descended from one of his numerous male relatives. Three percent of Jewish males who identify as Yisrael have the CMH.
Skorecki, K., S. Selig, S. Blazer, R. Bradman, N. Bradman, P. J. Waburton, M. Ismajlowicz, and M. F. Hammer (1997, January). Y chromosomes of jewish priests. Nature 385 (6611), 32.