It is widely known that the only person who carried the title of cohen (priest) after Israel went out of the land of Egypt was Aaron, the brother of Moses, of the tribe of Levi. The rest of the tribe – including Moses – remained Levites, and were not granted the proper title of the kehunah (priesthood).
In the divine decree appointing Aaron as a Cohen ha-Gadol (High Priest), it was stated that the priesthood would be passed from father to son. For this reason Aaron's sons and descendents, for all generations, were considered cohanim (priests), with the privilege of serving in the Temple, performing the priestly blessing, receiving gifts and tithes designated for the priestly class, and more. Only the daughter of a cohen who marries a non-cohen looses her priestly status, with her sons no longer being considered cohanim.
Certainly, the principle underlying the transmission of the priesthood from father to son is spiritual in nature, just as all of the Torah’s commandments are grounded in spiritual truths. Still, it is astounding to discover that an international research project on present-day cohanim has proven that the principle of “spiritual inheritance” also finds expression in the physical realm. Rousing a great deal of excitement in the world of genetic research, this groundbreaking study was performed by a team under the guidance of Prof. Karl Skorecki, Head of the Department of Nephrology and Molecular Studies at the Technion, Israel and Director of the Department of Nephrology at Rambam Medical Center in Haifa, Israel. Also included were researchers from the United States and England, such as Dr. David Goldstein and Dr. Neil Bradman from the University College of London, and many others. The results of the study were published in 1997 in the journal Discovery and in 1998 in Science News.
The project's data, collected over a number of years, revealed that cohanim from a wide range of Jewish communities – England, Tunisia, Canada, Russia, Yemen, and others – carry a shared genetic marker on their DNA, and this, at a much higher percentage than other demographic group. Approximately 80% of the cohanim tested carried the same genetic trait; whereas Jews that were not cohanim carried a similar genetic trait at a frequency of only 20%. Furthermore, the percentage of this shared trait among non-Jews was less than 5%.
According to project researchers, the high frequency of shared genetic elements among cohanim from such disparate communities testifies that they were linked to a single original family, and are descendents of a single patriarch living before the Jewish people was divided into two main communities – Ashkenazic and Sephardic – as a result of the Diaspora about a thousand years ago.
Furthermore, the most compelling finding of this research is that these shared characteristics are passed on solely from father to son, and not from father to daughter or from mother to son or daughter. This is because the gene in question exists only in the male Y chromosome, which travels from father to son only. In other words, only the male descendents of the prototype father can carry the unique characteristics that relate them to the original family of cohanim – in accordance with the divine decree mentioned above, which stated that the priesthood would be passed from father to son.
As if this evidence of genetic continuity was not convincing enough, certain tests were able to determine the number of generations that have passed since the existence of the original patriarch of this first family. By multiplying the number of generations by the number of years in each generation, we can estimate how many years that have passed since this man lived. But because one cohen might have been born to a father whose age was twenty, and another to a father whose age was forty, it was decided that the average age for every father should be set at thirty years old. Researchers therefore determined that the first father in this lineage must have lived one hundred and six generations ago.
One hundred and six generations times thirty years equal 3180 years.
According to Jewish tradition, Aaron the Cohen lived during the period of the Exodus from Egypt – approximately 3300 years ago! A calculation based on this scientific research has determined a date almost exactly in line with the period in which Aaron lived.
Furthermore, if we recall that the average age for a father was set at thirty years old, whereas in reality, there could have been significant fluctuation, we can conclude that there is an exact match between the facts of genetic research and the date of Aaron's life according to the Torah.
Dr. Abraham Amar, a senior scientist at the Tissue Typing Laboratory of Hadassah Ein-Kerem Medical Center in Israel, summarizes this research as follows:
“Anyone who refuses to believe in the tradition of the Jewish people must bow his head before scientific evidence proving the truth and authority of the Torah’s tradition as it has been passed down precisely from generation to generation.”