A study of skeletons excavated from a medieval Jewish cemetery in Germany has revealed a surprising genetic split among Ashkenazi Jews of the Middle Ages that no longer exists.
The analysis, the first of its kind from a Jewish cemetery and the result of years of negotiations between scientists, historians and religious leaders, shows that Ashkenazim have become more genetically similar over the past seven centuries. Two Jews walking the cobbled streets of 14th-century Germany were, on average, more genetically different than any two Ashkenazi Jews.
“That’s wild!” said Dr. Harry Ostrer, a medical geneticist at Albert Einstein College of Medicine in the Bronx and a co-author of the new study. “Despite the rapid growth of the Ashkenazi Jewish population over the last 700 years, the population became more homogeneous.”
The study, published on Wednesday in the journal Cell, compared DNA extracted from the teeth of 33 men, women and children buried in the cemetery with DNA taken from hundreds of modern Jews from around the world. Previous studies have shown that modern communities are a genetic hodgepodge, with Ashkenazim around the world carrying essentially the same collection of DNA sequences.
But the medieval remains tell a different story. They show that European Jews came from two divergent gene pools at the time.
Each group shared the same genetic ancestry, dating back to a small founder population that most likely emigrated from southern Europe and reached the German Rhineland around the turn of the first millennium. But the DNA analysis also revealed a genetic gap between the skeletons, which could have several explanations. In one scenario, both groups originated from the Rhineland. One branch then lingered in the region, while the other went east to present-day Poland, the Czech Republic, Austria and East Germany.
Alternatively, Eastern Europe could have been inhabited by a different population of Jews who then intermixed to a limited extent with their Jewish neighbors to the west.
Regardless, the two groups remained fairly isolated from each other for generations, as evidenced by their separate genetic lineages. Then, prompted by massacres, expulsions and economic opportunity, they reunited in places like Erfurt, the central German city that home to the cemetery where the remains were exhumed.
“It’s a super cool study,” said Itsik Pe’er, a computational geneticist at Columbia University who was not involved in the study. “Ancient DNA sequencing is a cheat code that can take you places where you have no information today.”
The existence of an east-west community in Erfurt is also supported by the historical record, which contains detailed accounts of a violent pogrom on March 21, 1349 – a Saturday. Angry mobs entered the local synagogue and attacked Jews as they prayed. Few survived.
After the massacre, the leaders of Erfurt took possession of property and assets. They even collected debts from the murdered Jews. But just five years later, the need for lost tax revenue led the city to invite Jews back.
They came from far and wide. Tax records list names drawn from all over Europe, including some from distant cities that have experienced their own anti-Semitic upheavals. “In the middle of the German-speaking countries, this was the place to be at the time,” says Maria Stürzebecher, a medievalist who is curator of the Museum of the Old Synagogue in Erfurt. At least, until 1453, when the Jews were expelled again.
The same migration patterns were seen in the excavated teeth.
Isotope measurements of tooth enamel showed that many people were migrants who had grown up elsewhere. But the DNA took this finding a step further, showing that Erfurtian Jews came from multiple places and those populations were genetically distinct.
“This evidence raises new questions and confirms stories we’ve been telling for a long time,” said Elisheva Baumgarten, a social historian at the Hebrew University of Jerusalem who was not involved in the study.
According to Maike Lämmerhirt, a historian at the University of Erfurt and a co-author of the study, preserved documents of money-lending practices show that the Jews of each subgroup largely formed business alliances with members of their own kind. But both groups prayed in the same synagogue. They were all cleansed in the same ritual bath. And in the end they all lay next to each other in the same cemetery.
The Erfurt skeletons carried many of the same disease-causing gene mutations that worry Ashkenazi Jews today. That suggests a population bottleneck must have occurred before the Erfurtians were born — one in which small numbers of individuals metastasized an entire population, leading to genetic similarities and the amplification of certain gene variants.
Scientists had previously calculated that the bottleneck event of the Ashkenazi Jewish population happened about 600 to 800 years ago. But the new study, together with a Briton study published this year examining six 12th-century skeletons found in Englandsuggest it could have been even further back.
“Given the date of these samples, we really put it at the very, very old end of those estimates,” said Mark Thomas, an evolutionary geneticist at University College London who led the British study.
“If you put the two papers together, they’re in complete agreement — which is pretty cool,” said Ron Pinhasi, an anthropologist and geneticist at the University of Vienna in Austria who was not involved in either study.
Rabbinic law generally frowns on the exhumation of corpses, out of concern for the dignity of the dead. Scientists therefore cannot excavate Jewish graves purely out of academic intrigue.
But what happened in Erfurt had nothing to do with the scientists.
In 2013, a warehouse built on top of the cemetery more than 500 years earlier was converted into a parking garage. Karin Sczech, an archaeologist then working at the state conservation agency, knew the construction could disrupt some ancient Jewish remains.
dr. Sczech arrived at the construction site a day before excavation work was to begin, only to find that the contractor had already broken ground. In the bucket of an actively digging excavator were the bones of a small child.
“I yelled at the driver and said ‘stop,'” recalled Dr. Sczech himself, now a UNESCO World Heritage Coordinator for Erfurt.
She and her team discovered 47 graves in an area about the size of a volleyball court. In consultation with the local Jewish community, the archaeologists meticulously removed the skeletons and took them with them back to the local archives.
The bones sat there for many years. The plan had been to rebury the bodies quickly, as soon as scientists had a chance to study the remains. But the anthropologist involved in the effort got tied up, causing a years-long delay.
Lucky for genetic science he did. Had the anthropologist been quicker, the skeletons would have been back in the ground before the geneticists who led the new study, David Reich of Harvard and Shai Carmi of the Hebrew University of Jerusalem, ever knew of their existence.
The researchers set out to excavate an ancient Jewish cemetery in 2017, hoping they could get a small sample for genetic testing.
Dr. Carmi took charge. He sought the advice of Ephraim Shoham-Steiner, a historian at Ben-Gurion University of the Negev, in Israel. “I said, ‘If there’s a role to play anywhere, it’s Erfurt,'” recalls Dr. Shoham-Steiner himself.
At first the highest rabbi in Erfurt dismissed the idea. There are situations where DNA testing on Jewish corpses is possible, for example families of Yemeni children who disappeared in the early years of Israel’s establishment may request that graves be opened for forensic identification.
But the reasoning in those cases focused on concrete benefits to the deceased. The situation is different when it comes to scientific research on anonymous bodies.
Dr. Carmi consulted a rabbinical judge in Israel – Rabbi Ze’ev Litke, founder of the Simanim Institute in Jerusalem, which helps people determine whether they have Jewish ancestry through genetic testing – who ruled that it would be allowed to isolate DNA from teeth or small loose bones of the inner ear which, unlike the rest of a skeleton, must not be reburied under Jewish law.
Convinced by the argument, the rabbi in Erfurt changed his mind. The project was a hit. Dr. Sczech found that 38 of the skeletons had at least one loose tooth.
Soon Dr. Reich returns to Boston with zippered bags full of medieval molars, bicuspids and incisors. Using techniques that have won this year’s Nobel Prize in Physiology or Medicinegot Dr. Reich and his colleagues successfully extracted DNA from 33 teeth.
The scientists hope their approach to community engagement will provide a roadmap for others seeking to examine the DNA of ancient remains, whether they come from Jewish cemeteries or not. “This is really kind of a prototype for what can be done in similar studies,” said Dr. Reich.
Views differ among authorities on Jewish law, or Halakha, on whether obtaining DNA from known Jews during an archaeological dig is illicit.
Rabbi Myron Geller, a scholar of Jewish burial practices and a former member of the Conservative Movement’s Committee on Jewish Law and Standards, described Rabbi Litke’s and the study’s authors’ rationale as the “strongest halakhic perspective possible.” “.
But others doubted that the abstract benefits of scientific knowledge were sufficient grounds for profaning the dead. “It makes me think,” said Rabbi Joseph Polak, Chief Justice of the Massachusetts Rabbinical Court.
On a recent trip to Yad Vashem, the Holocaust memorial atop Mount Herzl in Jerusalem, Dr. Carmi through the Valley of the Communities. In this huge monument to destroyed Jewish communities he found the name Erfurt. As in the Middle Ages, hundreds of Jewish residents of Erfurt were murdered during the Nazi era.
As he stood there, Dr. Carmi reflects on the bits of lost history his genetic analysis had helped uncover. “It was a great honor for me personally to bring their story to life,” he said.