Largest Ancient DNA Study Shows Medieval Ashkenazi Jewry Was Surprisingly Diverse

The excavation at the medieval Jewish cemetery of Erfurt. (TLDA Ronny Krause)
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Around the 14th century, Ashkenazi women in Erfut, central Germany, carried a BRCA 1 mutation indicative of breast and ovarian cancer in their DNA. Unfortunately, this mutation is all too common in the genomes of its modern descendants, which is just a genetic sign that not much has changed in the ensuing 700+ years.

According to research hailed as “the largest ancient Jewish DNA study yet,” posted on wednesday in the prestigious journal Cell Science, by the 14th century Ashkenazi Jews had already received most of their main sources of genetic ancestry. Compared to the DNA markers of modern Ashkenazi Jews, there have been few changes to the genome in the centuries since.

This is just one of the findings provided by the analysis of ancient DNA extracted from teeth taken from a Jewish cemetery that was excavated in a salvage operation carried out in accordance with the wishes of the local Jewish community together with rabbinical advisers. The skeletal remains were later reinterred in a 19th-century Jewish cemetery in Erfut.

In 2013, German archaeologists excavated a part of Erfurt’s old Jewish cemetery ahead of a municipal construction project and discovered some 47 medieval graves. It was just the kind of potential treasure trove of centuries-old DNA that Hebrew University Prof. Shai Carmi and Harvard University co-authors David Reich were looking for and began their study of the remains five years later.

“This work provides a template for how a co-analysis of ancient and modern DNA data can shed light on the past,” Reich said in a press release. “Studies like this hold great promise not only for understanding Jewish history, but for any population as well.”

Through careful analysis of DNA extracted from the teeth of 38 individuals, followed by a comparison of hundreds of thousands of genetic place markers in modern Ashkenazi genomes, an international team of more than 30 interdisciplinary researchers found that the Jews of Erfut “They were markedly more genetically diverse than moderns.” Ashkenazi Jews,” according to co-author Carmi.

“An even closer inspection revealed that the population of Erfurt was divided into two groups: one with more European ancestry compared to modern Ashkenazi Jews, and one with more Middle Eastern ancestry,” Carmi said.

After about three years of testing and analysis, much of which was done in technologically advanced clean rooms at Harvard University, the results also indicated that the “founder event” or “bottleneck” that is evident in the DNA of modern Ashkenazi Jews predates the establishment of the Erfut community, potentially by a millennium.

According to Carmi, some of the genetic diseases associated with modern Ashkenazi Jews, including BRCA 1 mutations and Tay Sachs disease, point to an extremely small starting population; as he grew older, “the pathogenic variants carried by the founders became more widespread.”

Teeth excavated from Erfurt’s medieval Jewish cemetery, from which DNA was extracted for genetic study. Each tooth is shown before and after DNA extraction. (David Reich Ancient DNA Lab/Harvard Medical School)

Among the methodologies used to obtain information from the ancient teeth, the scientists submitted 10 samples for radiocarbon dating, which found that all 10 lived between 1270 and 1400 CE. They also checked dental isotopes to see if the individuals had grown up drinking the same water and concluded that some were, in fact, immigrants.

The results were published in Cell in a paper, “Whole-genome data from medieval German Jews show that the Ashkenazi founder event predates the 14th century.”

rare opportunity

The opportunity to study the DNA of a medieval community like Erfut was just what Carmi and co-author Reich had been hoping for, Carmi told The Times of Israel on Wednesday.

There is some historical documentation of the migration patterns and persecution of medieval Ashkenazi populations. However, Carmi said, “Since no DNA sequences existed for historical Ashkenazi Jews, we sought to generate ancient DNA data for this population. Our hope was to fill in the gaps in our understanding of early Ashkenazi Jewish history.”

The central German city was a thriving Jewish center in the Middle Ages and boasts one of the oldest standing synagogues in Europe. The Jewish community settled there in the 11th century; a massacre decimated the community in 1349, but Jews lived in the area until a final expulsion in 1454. At this time, a granary was built on top of the cemetery, sealing the remains of thousands of Jews.

The barn that was built in the 15th century over the medieval Jewish cemetery in Erfurt. (Shai Carmi/Hebrew University)

“Jews in Europe were a socially segregated religious minority and suffered periodic persecution,” Harvard Reich said in a press release. “Our work gives us a direct idea of ​​the structure of this community.”

Among the 47 excavated graves were two small nuclear families, including children buried near their father, who apparently died of a violent blow to the skull. Other more distant family members were also discovered through genetic testing. Carmi said some eight of the 33 individual viable samples were related, and he conceded that the limited available sample may mean the results do not fully reflect the entire Ashkenazi Jewish community.

“As with other ancient DNA studies, our historical inferences are based on a single site in time and space. This implies that our data may not be representative of the full genetic diversity of early Ashkenazi Jews, as indeed we have inferred,” the authors write in the study.

At the same time, the study indicates that “medieval Ashkenazi Jews are best viewed not as a single, homogeneous community (as it came to be today), but as an ‘archipelago’ of communities, affected differently by founding events and mixing with local populations,” according to a FAQ sheet prepared by Carmi.

Another conclusion is that late medieval Ashkenazi Jewry already carried certain disease-causing variants that became increasingly common among Jews as the years passed.

a question of morals

Because it is against traditional Jewish religious practice to exhume remains for study, there are few opportunities to examine the DNA of Jewish communities.

Associate Professor at the Hebrew University School of Public Health and Faculty of Medicine, Shai Carmi. (Courtesy)

Carmi said he and his co-authors did not want to do anything “unethical” and felt it important and necessary to consult with the local Jewish community and a rabbi before beginning the study. The stipulation of the rabbinical authorities was that they only study the already excavated skeletons and only use loose teeth instead of extracting DNA from the bones.

Carmi also examines modern DNA for medical research in Israel, which, he said, is a “nightmare” to receive permission to conduct, with multiple committees and requirements and restrictions making the research “almost pointless,” he said.

“It is paradoxical or perhaps ironic that in order to carry out a study of ancient DNA, we are self-regulated. We do not need to get permission from any committee. These people are already dead,” he said, adding that if he were in charge of regulation, “I would relax the regulations on studies of living people a lot more but I would regulate the study of ancient DNA a lot more.”

The Old Synagogue of Erfurt’s medieval Jewish community. It is one of the oldest intact synagogues in Europe and now serves as a museum documenting Jewish life in Erfurt. (City of Erfurt Marcel Krummrich)

The reason behind the possible need for greater sensitivity about ancient DNA, he said, is that the results may contradict long-standing community perceptions and traditions. “People can get hurt emotionally. In this sense, it is important to consult with the communities and conduct the study ethically,” said Carmi.

“On the other hand, it can be argued that the history of those deceased people belongs to all of humanity and that no specific community ‘owns’ the remains of a particular place,” he said, acknowledging that working with ancient communities presents researchers with conflicting moral values.

“In the future, it will be interesting to see what the opinion of the rabbis, the scholars is,” Carmi said. “Maybe this study will lead to more openness. But maybe it will backfire and we’ll be told it’s something we shouldn’t do.”

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