The Lemba, a Bantu-speaking people of southern Africa, have a tradition that they were led out of Judea by a man named Buba. They practice circumcision, keep one day a week holy and avoid eating pork or piglike animals, such as the hippopotamus.
Several groups around the world practice Judaic rites or claim to be descended from biblical tribes without having any ancestral Jewish connection. And there is no Buba in the records of Jewish history.But the remarkable thing about the Lemba tradition is that it may be exactly right. A team of geneticists has found that many Lemba men carry in their male chromosome a set of DNA sequences that is distinctive of the cohanim, the Jewish priests believed to be the descendants of Aaron. The genetic signature of priests -- a hereditary caste, different from rabbis but with certain ritual roles -- is particularly common among Lemba men who belong to the senior of their 12 groups, known as the Buba clan.
The discovery of the Lemba's Jewish ancestry has come about through the intertwining of two unusual strands of inquiry. One was developed by geneticists in the United States, Israel and England who wondered what truth there might be to the Jewish tradition that priests are the descendants of Aaron, the elder brother of Moses.
The other strand was provided by Dr. Tudor Parfitt, director of the Center for Jewish Studies at the School of Oriental and African Studies in London. Parfitt, who has done research among the Lemba for 10 years, says that he has discovered Senna -- Lemba tradition maintains they came from that mysterious northern city -- and that he can retrace their steps from Senna to Africa, maybe a thousand years ago.
The genetic side of the story began when Dr. Karl Skorecki, a kidney expert at the Technion-Israel Institute of Technology, was sitting in a synagogue in Toronto. Skorecki, who is a priest, wondered if a fellow cohen who was being called to attend the first Torah reading might be distantly related to him, as the tradition of priestly descent from Aaron implied.
He called Dr. Michael F. Hammer of the University of Arizona, an expert who studies the genetics of human populations through the male or Y chromosome. Unlike the genetic material of the other chromosomes, the genetic material on the Y chromosome is not shuffled every generation, obscuring the lines of individual descent. Y chromosomes are bequeathed from father to son, more or less unchanged apart from the occasional mutation.
"The problem is there has been intermingling with host populations, and that has obscured their common ancestry," said population geneticist Dr. David B. Goldstein.
He looked at a set of three Y chromosome sites with stable genetic mutations and six sites at which mutations occur quite often, a mix designed to give good resolution between similar Y chromosomes during historical times. The mutations are all at sites on the DNA strand that lie outside the genes, and thus do not contribute in any way to the individual's physical makeup.
He found a particular set of genetic mutations at these nine sites that was strongly associated with the priestly caste, not so common among lay Jews, and very rare in non-Jewish populations.
He finds that 45 percent of Ashkenazi priests and 56 percent of Sephardic priests have the cohen genetic signature, while in Jewish populations in general, the frequency is 3 percent to 5 percent.
Because the cohen genetic signature is rare or absent in all non-Jewish populations tested so far, the findings strongly support the Lemba tradition of Jewish ancestry.