Symbolically, the symposium began on the Hebrew date of Rosh Hodesh Av, the first day of Av. This is the date of the death of Aharon, the first Jewish High Priest and brother of Moses, whose date of death is the only yahrzeit (date of death) mentioned in the Hebrew Bible.
The four-day conference hosted a mix of rabbis, geneticists and genealogists concerned with the history, duties and obligations of Kohens and Levis. Among them was Prof. Karl Skorecki of the Ramban/Technion Medical Center in Haifa who is renowned for his discovery in 1997 of the Kohen genetic signature.
Prof. Skorecki, a Canadian doctor who today is the director of Nephrology and Molecular Medicine at the Technion Faculty of Medicine, delivered the opening presentation about his research proving that the majority of kohanim alive today are descended from a single common male ancestor.
Skorecki began his lecture by providing a general overview to the subject of human genetics and DNA, noting that “out of the 3 billion DNA letter code, on average any two humans are 99.9 per cent identical. We are one large human family, regardless of geography.”
Focusing on the tiny differences in DNA sequencing, Skorecki explained the two types of mutations which cause human diversity – SNPs (Single Nucleotide Polymorphism) which occur approximately once every 10,000 years, and STRs (Single Tandem Repeats), which occur once in a millennium. Fidelity through the male blood line can be traced through the last of the 23 pair of chromosomes in the nucleus of a human cell, he explained. Similarly the female ancestor can be determined through the mitochondrial DNA, he noted.
Using these SNP and STR genetic markers, Skorecki demonstrated what he called the “Cohen Modal Haplotype” (CMH), a polymorphism on the Y chromosome found in a higher frequency in the Kohen caste than the general Jewish population, suggesting that most if not all Kohens are direct descendants of Aharon through a patrilineal line extending back 3,300 years or more than 100 generations.
Complicating the issue, Skorecki reported that he and his research team have discovered not one but two Cohen Modal Haplotypes, which he called J1 and J2. Pinchas the zealot mentioned in the Bible may be the origin of J2, he suggested.
Why don’t all Kohens share the same genetic markers?
“Halacha provides the answer, not DNA,” Skorecki noted. After the rebirth of the dead in the messianic era, scientists will be able to take a DNA sample of Aharon, settling the issue, he joked.
Adding yet another layer to the Kohen DNA story, Skorecki spoke about the disproportionate presence of the CMH among the males of the Lemba tribe in Mozambique and South Africa, suggesting an ancestral link to the Jewish peple. One sub-clan within the Lemba, the Buba clan, is considered by the Lemba to be their priestly clan. Among a small sample of the Buba, fifty-two percent of males were found to carry the Cohen Modal Haplotype. The Lemba also have a large percentage of genes often found in non-Arab Semites.
More recently Skorecki and his team discovered that some 3.5 million, or 40 per cent, of Ashkenazi Jews are descended from four “founding mothers” who lived in Europe 1,000 years ago.
The only child of Holocaust survivors, Skorecki was born and raised in Toronto. He received his medical degree from the University of Toronto in 1977 and conducted his post-graduate clinical and research training at the Brigham and Women’s and Massachusetts General Hospitals. In 1984, he established a research program in the areas of kidney disease, molecular biology and human genetics at the University of Toronto Division of Nephrology. He was subsequently appointed professor and director of the Division of Nephrology in the Departments of Medicine, Pediatrics, and Clinical Biochemistry at the University of Toronto, and research scientist and director of the Nephrology Division at the Hospital for Sick Children, also in Toronto.
After a sabbatical at the Weizmann Institute in Rehovot in 1991, Prof. Skorecki and his family decided to make aliyah to Israel and he joined the Technion faculty in 1995. In addition to conducting research in molecular biology and human genetics at the Technion, Prof. Skorecki has served as a clinical nephrologist at Rambam Medical Center, and as director of the Nephrology Department and of the Rappaport Research Institute in Haifa.