Blood Matters
Page 4
It was an imperfect analogy. The word in Skorecki’s example had built-in protection against falsification: It was a secret. To appropriate the tradition, someone who was not a descendant of the original secret holder would have to guess the word. To pose as a Cohen, all one had to do was claim to be one. Not all Cohanim have Cohen or a variation of it as their last name: Skorecki does not. And Jewish history is ripe with examples of broken lineages, migrations, and other opportunities for impostors. The fact that in most cases a Cohen is a Cohen is a Cohen is, in its way, an affirmation of truth and honesty, which seem to have won out through a hundred generations of humans.
Using DNA evidence, one could try to corroborate any story in the world: All you have to do is ask the right question. Skorecki and his colleagues have been adamant about refusing to help anyone check Cohanim claims through DNA; in any case, rabbinical authorities are not about to institute DNA checks of an oral tradition—though the possibility of doing so will certainly be discussed over and over in the coming years and decades. But anyone who is uncertain of his heritage—say, a Jew raised in the Soviet Union, where the Jewish oral tradition was interrupted—can have his DNA tested for the Cohen modal haplotype through a commercial company.
One story that people have longed to confirm and develop for centuries is the story of the ten lost tribes of Israel, which were said to have been taken away by Assyrian armies some seven centuries before the current era. That was when they disappeared from the written account. Could their progeny be found now, through DNA? Possibly.
A number of small populations in different parts of the world have legends linking them to the ancient Hebrews. One such group is the Lemba, a population that has remained endogamous—has married within the group—despite being scattered throughout southern Africa. The Lemba circumcise their newborn males, keep one day of the week holy, and do not eat pork. None of these traditions is unique to Judaism, but generations of the Lemba have maintained a story of Jewish descent, and have been known to neighbors as the “black Jews.” A closed population with mysterious roots, the Lemba long attracted the attention of geneticists, and a 2000 study in a scientific journal reported that their claim of Jewish provenance seemed to be true. Not only did many of the Lemba carry a haplotype found predominantly among Semites—which might as well have meant that they were of Arabic descent—but one of the Lemba clans had a very high frequency of the Cohen modal haplotype identified by Karl Skorecki and Mike Hammer.
The discovery confirmed the Lemba oral tradition. That dovetailed nicely with a rare occurrence: a burst of Jewish proselytizing among the Lemba. Strictly speaking, Jews are not allowed to seek converts. But the Lemba—at least some of them—had long believed themselves to be Jewish in some sense, and had practiced some rough approximations of Jewish religious customs. So proselytizing among the Lemba might be interpreted as reaching out to less-observant Jews in an attempt to make them observe more of that tradition, and this is certainly allowed. In the three years following the discovery of the Cohen haplotype among the Lemba, at least three rabbinical missions from the United States brought the Lemba books on Jewish tradition, prayer shawls, and other gifts to celebrate their affirmed Jewishness. It seems the Lemba elite, or at least some of it, welcomed the missions and began something of a Judaic revival.
One thing the Lemba did not do, however, was rush to emigrate to Israel—something they certainly could have tried to do, since Israel, in accordance with the Law of Return, grants citizenship to all persons who are born Jewish or have a Jewish parent or grandparent or convert to Judaism. Had the Lemba tried to immigrate en masse, Israel, as a state, would have had to take a position on the relationship between DNA information and ethnic or religious identity. Indeed, Israel is quite likely to face this discussion sooner or later, both because it is one of a few countries that grant citizenship on the basis of ethnicity and because Jewish DNA is arguably the best-studied DNA in the world. Plus, there are still at least nine lost tribes out there.
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The most obvious way to try to match DNA information against history is to try to perform genetic tests on the remains of people who lived many centuries before us. “The problem with ancient DNA is, it is in pieces. It is like reading fragments of words instead of complete sentences,” Marina Faerman told me over coffee in a cafeteria at Hadassah, the Jerusalem medical center. She was a slight woman with wispy dirty-blond hair and large gold-rimmed glasses. A physical anthropologist, she had been casting about for something to do to gain a foothold in Israeli science after she immigrated from Russia in 1990. A couple of her newfound colleagues suggested she try to tackle ancient DNA: The work would be tedious, but the payoff would be publications of notice. She teamed up with several local researchers, including a charismatic senior geneticist-hematologist named Ariella Oppenheim, and began deciphering the DNA of remains found in archaeological digs.
In 1998 they published a paper on determining the sex of infanticide victims found in a dig in Ashkelon. The remains of about a hundred babies had been found beneath a late–Roman Empire bathhouse. Because the babies were newborns, showed no sign of disease, and had been disposed of in what seemed to have been a gutter, and because historical records indicate that infanticide was practiced in that culture, they assumed the babies had been killed soon after birth. They collected their left femurs (this was done to avoid testing the same individual twice) and set out to extract their DNA to see if they had been boys or girls. They should have been girls, for infanticide was known to have been practiced more frequently on girl babies, but most of them turned out to have been boys. Upon consulting with historians and archaeologists, they postulated that the bathhouse may have been a bordello whose staff disposed of their babies but kept some of the girls to rear as courtesans.
That was a neat trick, and Faerman and Oppenheim went on to perform more of these. One of their papers is called “From a Dry Bone to a Genetic Portrait: A Case Study of Sickle Cell Anemia.” This time the DNA they were testing was contemporary, but they had even less information than if they had received the tissue sample from a dig. All they knew about the bone fragment was that it came from a person who had had sickle-cell anemia. A genetic test confirmed the diagnosis. A look at the Y-chromosome DNA (the person had a Y chromosome, which made him a male) showed that his father’s family came from a Bantu heritage (the Bantu actually comprising about four hundred ethnic groups in Africa), while his mitochondrial DNA placed his maternal ancestors in West Africa—possibly Nigeria. This combination of heritages pointed to the Caribbean as the man’s own likely place of origin. Only after creating a DNA sketch of the man whose tiny bone fragment they had tested did the researchers obtain his medical history: He turned out to be a black Jamaican-born male who had died of sickle-cell anemia in the United States. The researchers were so taken with their ability to derive the relevant facts of sex, provenance, and diagnosis from a tiny tissue sample that they published a paper about it.
In fact, they had already performed even more impressive feats: They had used bone fragments to diagnose people who had lived many centuries before. Oppenheim, a hematologist, was particularly interested in blood disorders and had spent many years studying beta-thalassemia, a recessive condition that results in severe anemia and bone deformities. Babies born with beta-thalassemia become weak and lethargic at around the age of three months and, if the disease is allowed to run its course, often die by the age of one. But if patients are given regular blood transfusions—every few weeks starting in infancy and continuing through life—they can have a normal life span. Beta-thalassemia and other thalassemias are the world’s most common genetic disease, with more than 100 million carriers alive today and more than 120,000 affected individuals born annually. Because thalassemias are common in areas that have been affected with malaria, the current theory is that carriers—people with only one copy of a gene with a thalassemia-causing mutation—are better-protected against malaria than those who do not carry an abnormal
gene. There are very few carriers among Ashkenazi Jews but about 20 percent of Kurdish Jews have the mutation, and some Arab communities in Israel have a carrier rate of more than 10 percent. There are, however, only a couple hundred people with beta-thalassemia living in Israel, apparently because births of affected individuals are prevented through prenatal screening and therapeutic abortions or even earlier, via preimplantation screening: When both people in a couple know they are carriers, they may opt for in vitro fertilization, during which only unaffected embryos will be implanted.
In a dig in Akhziv, in Israel, archaeologists found the remains of a child who likely died of anemia two to five hundred years ago: The child’s bone deformities suggested the diagnosis. Ariella Oppenheim’s team performed a DNA analysis and confirmed that the child was a homozygote for one of the roughly hundred mutations that lead to the disease. The odd thing was, the child had lived to be about eight years old—usually victims of the disease cannot make it past infancy in the absence of regular transfusions. The DNA analysis (performed separately on three different fragments of the skull, to ensure that the researchers were testing the remains and not some intruding matter) suggested the answer.
Symptoms of beta-thalassemia do not show up in newborns right away because their blood contains fetal hemoglobin, which the mutation does not affect. Sometime in the first year of life, adult hemoglobin, which is actually a different substance, takes the place of fetal hemoglobin. People with beta-thalassemia cannot produce normal adult hemoglobin, which is why they get weak and their bones stop developing normally. But some of them carry another gene variant, which causes their bodies to continue producing fetal hemoglobin. This was why the boy from Akhziv had lived to the age of eight.
Here was another cool genetic study. Not only were the scientists able to diagnose a long-dead person, they were able to use centuries-old remains to confirm a contemporary clinical hypothesis: The fetal-hemoglobin-producing gene variant actually ameliorated the effects of beta-thalassemia. It would have been impossible to confirm this hypothesis experimentally: No person with beta-thalassemia could be allowed to go without transfusions in order to observe the course of his disease.
Oppenheim’s team had more fun with beta-thalassemia mutations. In another paper, coauthored with Canadian researchers, they reported the simultaneous discovery of the same rare beta-thalassemia mutation in Ashkenazi families in Jerusalem and Montreal—and the consequent discovery that the families were probably related. When two people share not only a particular mutation but also the variants of genes in its particular neighborhood, this sort of mutation is called “identical by descent” and points to the existence of a shared ancestor. The two thalassemia families traced their roots to the Pale of Settlement, where their ancestors appeared to have lived in towns 250 miles apart about 150 years ago. The genetic quest turned into a genealogical one: The families, and the researchers, were now looking for a single common ancestor (they had not found one by the time they published a paper in the journal Human Mutation).
In another study, Oppenheim suggested looking at the many beta-thalassemia mutations found in Israel as a sort of historical map that recorded various migrations to Israel: Here was a mutation that hailed from Kurdistan, there one that came from Turkey, one from Yemen, one from India, and so on. This was the sort of project in which ancient DNA could prove very useful: It could show who came to Israel, when and where from. The tools for analyzing the material were there, but one thing was missing: a genetic picture of the current Israeli population, which would provide a frame of reference.
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So Oppenheim, Faerman, and their colleagues took DNA samples from various local groups and went to work trying to answer a few simple earth-shattering questions. Faerman listed them for me: “What is the connection among different populations of Jews? What is the connection between Jews and Arabs? And where did they all come from?” Did they have a hypothesis? “What hypothesis could we have had?” bristled Faerman. “There is the Bible, there is the Tanakh.”
That hypothesis proved pretty much on target. By comparing DNA samples from Israel with DNA samples from Muslim Kurds now living in Kurdistan, the researchers concluded that the current population of Israel hails from there, where the Tanakh—the Hebrew Bible—indicates Abraham came from. They also found that Jews and Arabs are indisputably related, though, for instance, the Cohen genetic signature is found almost exclusively among Jews. They also found that Ashkenazi Jews, who constitute the Israeli elite, are perhaps a bit more closely related to Kurdish Jews, whose social standing places them at the bottom of the population heap, than they are to the Sephardic majority. This gave Oppenheim particular pleasure. She was one of those very rare Israeli Jews whose personal history in the region goes back more than three centuries, when some of her family moved there. Her grandfather wrote poetry in Arabic, and her other grandfather was a dentist in Arab villages. She had always been privy to the little-known fact that Jews and Arabs are brothers, and she hoped, briefly, that their study would open the eyes of her compatriots.
Oppenheim, a professor emeritus at the Hebrew University in Jerusalem by the time I interviewed her in her very cluttered office at Hadassah (where she, being emeritus, went every day solely for the pleasure her work brought her), was a smart woman. A very smart woman. She had the intellectual capacity to know that scientific evidence and facts in general have no impact on ethnic enmity; it was just that these DNA studies, reaching as they do into the depths of our molecules, have a way of enticing magical thinking. Anyway, she said, “Then I thought more about it, and I realized in many families brothers many times fight. So these genetic relationships are no guarantee of good relations. I also found that the ideologies of people don’t change and they just take the facts to fit the ideology. For example, one person said that it’s fantastic because now we can convert all the Palestinians to Judaism, sort of prove to them that they belong to the Jewish state.”
There was a different sort of sensation hidden in that 2001 study. “We found that between 10 and 15 percent of Ashkenazi Jews, from different samples—we took Ashkenazi Jews from the United States, from Africa, from Israel, from many different locations, and it all was quite consistent—about the same percentage appears to have originated from a gene flow that came from Eastern Europe–Central Asia, somewhere in that region,” said Oppenheim. “Gene flow” is just what it sounds like: the flow of genes into a population, from the outside. Gene flow happens, for example, when people begin to intermarry. The researchers traced this genetic signature to the first millennium, to someplace, they thought, in Eastern Europe. Did that mean that the Ashkenazi foremothers, recently settled in Europe, may have mixed with the locals? Possibly. But Oppenheim’s group proposed a more intriguing explanation. They thought the pattern they saw in the Y-chromosome DNA samples they analyzed suggested that the incursion into the Ashkenazi population occurred through the introduction of several men who were related to one another. Perhaps, they thought, they were a group who converted to Judaism. Perhaps they were the Khazars.
The Encyclopedia Judaica says the Khazars were “a national group of general Turkic type” who lived and battled their neighbors somewhere in the Caspian–Caucasus region between the seventh and tenth centuries and then converted to Judaism. The thing the Encyclopedia Judaica does not tell us is whether the Khazars ever actually existed, and hence whether they really had a king and whether the king, along with all his dignitaries, converted to Judaism. That is what legend tells us. And most Jewish population geneticists find this legend unspeakably alluring. This may be because it is like genetic drift: It can be used to explain a great many things. But more likely, this is because it dangles before the population geneticist the ultimate research carrot: the possibility of proving something that has not yet been proved.
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Karl Skorecki and Doron Behar, whom Skorecki had now drafted as a geneticist, also stumbled upon something unexpected when they tried to replicate Skore
cki’s Cohanim finding with a study of the Levites. Membership in the Levite caste, too, is passed from father to son, and Skorecki initially expected the lineage to be even more strongly evident—because, he explained to me, becoming a Cohen impostor would have carried more benefits than becoming a Levite impostor. Levites are those male descendants of Jacob’s son Levi who are not Cohanim. During some of Jewish history, they have enjoyed many of the same benefits and privileges as the Cohanim without some of the restrictions (such as restrictions in marriage, for example). When the researchers started looking at the Y-chromosome DNA of contemporary Levites, they saw that about half those Levites who were Ashkenazi carried a distinctive genetic signature that pointed to a common male ancestor who lived a mere thousand years ago, give or take a thousand years. “We have an event,” said Skorecki. “I think DNA has provided a glimpse into a probable historical event, some minor event perhaps, which has left a remnant today, which I don’t think could have been uncovered in any other way. Maybe one day someone will find some archival record that matches this, but I think it would be very difficult.” For the purposes of genetic research, “an event” is anything that causes changes in the gene pool. A rape can be an event, as can a conversion, a migration, or a pogrom. But what was this particular event? Could it have been the Khazars?