Medieval remains shed light on Ashkenazi Jewish heritage

(CN) — Skeletons found inside a medieval well discovered outside of London have clued scientists in to the genetic history of Ashkenazi Jews.

The development of a shopping center in Norwich, a city northeast of London, was halted in 2004 when a well containing 17 skeletal remains were discovered on site. The bodies appeared to have been thrown in, all on top of each other, in contrast to other medieval mass burial sites where bodies were usually neatly arranged.

The bodies were later dated to the early Middle Ages, and preliminary genetic investigation in 2010 identified the bodies as Ashkenazi Jews. Now, in a study published Monday in Current Biology, researchers present new findings based on these remains, which give new insight on the history of Ashkenazi Jews in the U.K.

Although mass burials could suggest other mass fatality events like disease or famine, the revelation that the individuals had been Ashkenazi Jews led researchers to theorize that the bodies in the well had been victims of antisemitic violence. Early 12th century Norwich has been categorized as an era of particularly severe antisemitic sentiment and is even credited as the documented origin of the blood libel myth.

“These are the oldest Jewish genomes,” said Mark Thomas, co-author of the paper and a professor of evolutionary genetics at University College London.

He emphasized the unique scientific opportunity of the Norwich remains.

“In general, there are no ancient Ashkenazi genomes because it is prohibited to disturb Jewish graves, particularly for scientific study. However, in our case, there was no way of knowing whether they were Jewish or not until we had done the genetic studies; of course, if they had been known to be Jewish at that time, we wouldn’t have been able to do this work in them,” Thomas said.

Researchers utilized updated technology that were not yet available to them even a decade ago when the remains were first identified as having Ashkenazi Jewish heritage, to uncover even more information about the bodies in the well.

“The technology that’s been available to do the kind of work that we do has just improved over time. Twelve to thirteen years ago, when we first did the work, the technology was not as advanced as it is now, so we were working with at a few hundred base pairs of DNA sequence, as opposed to the millions of base pairs currently,” said paper co-author Ian Barnes of London’s Natural History Museum. Barnes was one of the initial researchers that first identified possible Ashkenazi Jewish heritage in the remains.

Significantly, results modelled by these updated computer simulations indicated that the Ashkenazi population to which the individuals in the well belonged had gone through a bottleneck event, where a population undergoes sudden and extreme population reduction, perhaps earlier than previously thought.

“If you look at the scientific literature, most publications where they’ve tried to estimate when that bottleneck took place, place it in the last 800 years. What that means is that most theories about when that bottleneck that drove up the frequencies of certain genetic diseases in Ashkenazi Jews took place, is that it took place after when these individuals were alive,” Thomas said. “If that’s the case, then that predicts that the population from which these individuals come would have a lower frequency of these genetic diseases than Ashkenazi Jews today.”

Bottleneck events are a large part of studies into Ashkenazi genetic history. Frequent bottleneck events and endogamous marriage practices have led to heightened risk for certain hereditary disorders in Ashkenazi populations. Based on these previous studies, researchers expected that disease allele frequencies of the remains to be closer to frequencies of the general European population.

The presence of genetic disorders carried by the individuals in the well showed disease variations in the remains that were unexpectedly nearly level with modern-day numbers.

With the updated technology, researchers were also able to approximate some of the bodies’ physical characteristics and could even determine familial links between several the remains. The 17 individuals in the well were revealed to be a mixture of both children and adults, with the youngest estimated to be toddler aged. Three of the skeletons were discovered to have belonged to sisters.

Although researchers have speculated as to the possible antisemitic fates of the Norwich well individuals, the true reason for their death may never be learned for certain, the study noted, as the bones themselves do not actually show signs of violent trauma.

Genetic testing has given, at least, a context for the remains. After the initial testing revealed signs of Ashkenazi heritage, the remains were able to be reburied in a Jewish ceremony by Norwich’s thriving Jewish community in 2013, centuries after their deaths.

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