Cohen Modal Haplotype (CMH)

 Cohen Modal Haplotype (CMH)

The Cohen Modal Haplotype (CMH) is a specific genetic signature found on the Y-chromosome that is associated with Jewish men who identify as Kohanim, the priestly class in Judaism believed to descend patrilineally from Aaron, the brother of Moses.

The Cohen Modal Haplotype (CMH) is a specific pattern of genetic markers found on the Y-chromosome. It includes a set of short tandem repeat (STR) values that were commonly found among self-identified Kohanim from diverse Jewish communities (Ashkenazi, Sephardi, and Mizrahi).

• “Modal” means it's the most common pattern in a group—in this case, among Kohanim.

• The CMH was first defined in the 1997 study by Dr. Karl Skorecki and Dr. Michael Hammer.

• It originally consisted of six STR markers that formed a distinctive signature.

For example, the original CMH included these STR values:

DYS19 = 14

DYS388 = 16

DYS390 = 23

DYS391 = 10

DYS392 = 11

DYS393 = 12

What Are STR Markers?

• STR stands for Short Tandem Repeat.

• STRs are sections of DNA where a short sequence of bases (letters) — usually 2 to 6 base pairs long — is repeated multiple times in a row.

  For example, a sequence like:
  AGAT AGAT AGAT AGAT — here, “AGAT” is repeated 4 times.

• The number of repeats can vary between individuals.

• Because these repeat numbers change slowly over generations, STRs are useful for tracing family relationships and ancestry.

Term	Meaning

STR	Short Tandem Repeat – repeated DNA segments

Marker

Specific location on the Y-chromosome where repeats are counted

CMH	A particular combination of six STR values common in Kohanim

The original CMH falls within Y-DNA haplogroup J, more specifically:

• J1 (J1-P58) – Common among Middle Eastern populations, and particularly linked to Semitic ancestry.

• A smaller number of Kohanim belong to J2, another Middle Eastern haplogroup.

Haplogroup J (Middle Eastern origin)

│

├── J1 (Most Cohen Modal Haplotype carriers)

│    ├── J1-P58 (Main subclade associated with CMH)

│    │    └── Cohen Modal Haplotype (CMH)

│    │          └── Found predominantly in Kohanim from diverse Jewish communities

│    │

│    └── Other J1 subclades (Less associated with CMH)

│

└── J2 (Some Kohanim belong here)

     └── Various subclades (More common in Mediterranean populations)

            Aaron (c. 1400 BC)

                │

     ┌──────────┴──────────┐

     │                     │

 Eldest Son           Other Sons

     │                     │

     ▼                     ▼

   Kohanim         Other Israelites

     │

     ▼

 [Y-Chromosome passed down unchanged]

     │

     ▼

 Modern Kohanim

 (e.g., men named Cohen, Kahan, Kagan, Katz)

              ◉  Europe (Ashkenazi Jews)

             / \

            /   \  

        ◉ Israel ◉ Iraq / Iran (Mizrahi Jews)

           |     

      ◉ Yemen, Egypt (Yemenite & Sephardic Jews)

           |

       ◉ Ethiopia (Beta Israel - partial)

Mizrahi Jews (from the Middle East, particularly Iraq, Iran, and Yemen)

Sephardi Jews (from Iberia and later the Mediterranean)

Ashkenazi Jews (from Europe)

Timeline and Historical Context

Period	Event / Context
~1300 BCE	Traditional time of Aaron, the first Kohen
1000 BCE – 500 BCE	Formation of the ancient Israelite priesthood
600 BCE	Babylonian exile disperses Jewish populations
1st Century CE	Jewish diaspora expands across the Roman Empire
20th Century	Diverse Jewish populations (Ashkenazi, Sephardi, Mizrahi) spread globally
1990s	Discovery of CMH by geneticists Skorecki & Hammer