Ashkenazi Jews Have Become More Genetically Similar Over Time

A study of skeletons unearthed from a medieval Jewish cemetery in Germany has revealed a surprising genetic split among defunct medieval Ashkenazi Jews.

The analysis, the first of its kind from a Jewish burial ground and the product of years-long negotiations between scientists, historians and religious leaders, reveals Ashkenazim has become more genetically similar over the past seven centuries. On average, two Jews walking the cobblestone streets of 14th-century Germany were more genetically different than any two Ashkenazi Jews alive today.

“Real wild!” Harry Ostrer, a medical geneticist at the Albert Einstein College of Medicine in the Bronx and a co-author of the new study. “Although the Ashkenazi Jewish population has grown rapidly over the past 700 years, the population has become more homogeneous.”

research, 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 around the world. gender. Previous studies have shown that modern communities are a genetic mix, with Ashkenazim worldwide carrying essentially the same set of DNA sequences.

But medieval ruins tell a different story. They show that European Jews at the time came from two different gene pools.

Each group shares a common genetic origin, originating in a small group of founders who most likely migrated from Southern Europe and arrived in the German Rheinland at the beginning of the first millennium. But DNA analysis also revealed genetic splits between the skeletons, which could have several explanations. In one scenario, both groups were originally from the Rhineland. One branch then stuck around the area, while the other headed east to present-day Poland, the Czech Republic, Austria, and eastern Germany.

Alternatively, Eastern Europe may have been settled by another group of Jews, who then mixed to a limited extent with their Jewish neighbors to the west.

Either way, the two groups remained fairly separate from each other for generations, as evidenced by their sporadic genetic lineage. Then, due to massacres, evictions, and economic opportunities, they reunited in places like Erfurt, a city in central Germany. home to the cemetery where the remains were scattered.

“It’s a great study,” said Itsik Pe’er, a computer geneticist at Columbia University who was not involved in the study. “Ancient DNA sequencing is a cheat code that can take you to places where you have no information today.”

The existence of an east-west community meeting in Erfurt is also supported by historical records, including detailed accounts of a violent massacre on March 21, 1349 – a Saturday. . Angry mobs stormed the local synagogue and attacked Jews in the middle of a prayer service. Few, if any, survived.

After the massacre, the leaders of Erfurt appropriated property and belongings. They even demanded debt from the murdered Jews. But just five years later, the need to lose tax revenue led the city to invite the Jews back.

They come from far and wide. Tax records show names denoting origins from across Europe – including some from far-flung cities that have experienced upheaval of their own. “In the midst of German-speaking lands, here Maria Stürzebecher, a medievalist and curator of the Old Synagogue Museum in Erfurt, said it was worth visiting at the time. At least, that is, until 1453, when the Jews were forced to leave again.

Similar patterns of movement can be seen in the excavated teeth.

The results of isotopic measurements from tooth enamel show that many people are migrants who grew up elsewhere. But DNA took the finding a step further, showing that Erfurtian Jews came from many places and those populations were genetically distinct.

“This evidence both raises new questions and confirms the stories we’ve been told,” said Elisheva Baumgarten, a social historian at the Hebrew University of Jerusalem who was not involved in the study. ages ago long ago.

According to Maike Lämmerhirt, a historian at the University of Erfurt and a co-author of the study, the records kept on money-lending practices show that Jews from each subgroup largely formed alliances. doing business with members of the same type. But both groups prayed in the same synagogue. They were all washed in the same bathing ritual. And in the end, they were all lying next to each other in the same cemetery.

The Erfurt skeletons carried many of the same disease-causing genetic mutations that Ashkenazi Jews worry about today. That suggests a population bottleneck must have occurred before Erfurtians were born – one in which a small number of individuals seeded the entire population, leading to genetic similarity and diffusion. of certain gene variants.

Scientists have previous calculation that the congestion event of the Ashkenazi Jewish population occurred about 600 to 800 years ago. But new research, along with an Englishman Research published this year examined six 12th-century skeletons found in Englandsuggests that it may have gone back even further.

Mark Thomas, an evolutionary geneticist at University College London who led the UK study, said: “Given the dating of these samples, we really put it at the very old end of the estimates. there.

“If you put the two papers together, they completely agree with each other,” said Ron Pinhasi, an anthropologist and geneticist at the University of Vienna in Austria who was not involved in both studies. – this is pretty cool.

Rabbinic law often frowned upon exhuming corpses, out of concern for the dignity of the dead. Therefore, scientists cannot excavate Jewish grave sites purely for academic purposes.

But what happened in Erfurt has nothing to do with scientists.

In 2013, a barn built on top of the cemetery more than 500 years ago was converted into a garage. Karin Sczech, an archaeologist then working for the state conservation office, knew that construction could disturb some of the ancient Jewish monuments.

doctor Sczech arrived at the work site a day before the scheduled start of excavation, only to find out that the contractor had broken ground. Inside the barrel of an actively digging excavator are the bones of a small child.

Dr Sczech, now UNESCO World Heritage coordinator for Erfurt, recalls: “I shouted at the driver and said ‘stop’.

She and her team discovered 47 graves in an area roughly the size of a volleyball court. After consulting with the local Jewish community, archaeologists meticulously removed the skeletons and brought them back. back to the local repository.

There, the bones sit for many years. The plan is to bury the bodies as quickly as possible, when scientists have a chance to study the remains. But the anthropologist involved in the effort was tied up, causing years-long delays.

Lucky for the genetics he did. Had the anthropologist been quicker, the skeletons would have returned to the surface before the geneticists who led the new study, David Reich of Harvard and Shai Carmi of the Hebrew University in Jerusalem, knew of existence. of them.

Researchers began in 2017 to find an ancient Jewish cemetery being excavated, in the hope that they could take a small sample for genetic testing.

Dr. Carmi leads. He sought advice from Ephraim Shoham-Steiner, a historian at Ben-Gurion University of the Negev, in Israel. Dr Shoham-Steiner recalls: “I said, ‘If there’s anywhere this could really work, it’s got to be in Erfurt’.

At first, the leading cleric in Erfurt rejected the idea. There are situations that allow DNA testing on Jewish corpses – for example, the family of Missing Yemeni Children in the early years of Israel’s founding may require opening the graves for forensic identification.

But the rationale in those cases focuses on specific benefits for the dead. Scientific research done on anonymous bodies is different.

Dr. Carmi consulted with a rabbinic court judge in Israel — Rabbi Ze’ev Litke, founder of the Simanim Institute in Jerusalem, which helps people determine if they have human ancestors Jewish or not through genetic testing — who ruling that it will be allowed to isolate DNA from teeth or small detached bones of the inner ear, unlike the rest of the skeleton, does not require reburial under Jewish law.

Convinced by the argument, the rabbi in Erfurt changed his mind. The project was successful. Dr. Sczech discovered that 38 skeletons had at least one tooth removed.

Soon, Dr. Reich was flying back to Boston with zipped bags filled with medieval molars, molars, and incisors. Use winning techniques This year’s Nobel Prize in Physiology or MedicineDr. Reich and colleagues successfully extracted DNA from 33 teeth.

The scientists hope their approach to public engagement will provide a route for others hoping to examine the DNA of ancient remains, whether from Jewish cemeteries or are not. “This is really a kind of prototype for what can be done in similar studies,” said Dr. Reich.

Opinions vary among authorities on Jewish law, or Halakha, as to whether the collection of any DNA during archaeological excavations of known Jews is on the board. .

Rabbi Myron Geller, a scholar of Jewish burial practices and a former member of the Committee on Jewish Law and Standards for the Conservatives, described the rationale given by the Rabbi. Litke and the study authors adopted as “the strongest possible halakhic view”.

But others question whether the abstract benefits of scientific knowledge are grounds enough to merit insulting the dead. “That gave me pause,” said Rabbi Joseph Polak, chief justice of the Massachusetts Clergy Court.

On a recent trip to Yad Vashem, the Holocaust memorial atop Mount Herzl in Jerusalem, Dr. Carmi took a stroll through the Valley of Communities. In this massive monument to ravaged Jewish communities, he found the name Erfurt. Just like in the Middle Ages, hundreds of Jewish residents in Erfurt were murdered during the Nazi era.

Standing there, Dr. Carmi pondered over the lost pieces of history his genetic analysis had helped unmask. “Personally, it is a great honor for me to bring their story to life,” he said.


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