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Genes

Scientists uncover the hidden genetic consequence of an 800-year-old hate crime

Finding a mass grave opened the door to research that would’ve been impossible otherwise.

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In 1190 in what was once East Anglia, one of Europe’s most notorious cold cases transpired. In 2004, 814 years later, construction workers building the Chapelfield shopping mall in what’s now Norwich, U.K., unknowingly dug into the scene of the crime.

They uncovered the skeletal remains of at least 17 people who had been dumped in a medieval well. By analyzing the bones with radiocarbon dating and studying the pottery shards that surrounded them, researchers dated the remains to between the 12th and 14th centuries. History Cold Case on the BBC covered this crime in 2011 in the episode “Bodies in the Well,” and in that same year, the remains were ritually reinterred in a cemetery.

Historical accounts of this crime match the scientists’ estimated date. In this massacre, members of the local Jewish community were killed in an antisemitic riot. At the time, antisemitism was on the rise due to the third crusade, and the first instant of blood libel was in 1144 when the Jews were blamed for the death of William of Norwich.

In the 18 years that we’ve possessed this gruesome data, researchers have found through whole genome sequencing that the DNA of those in the well strongly correlated with that of Ashkenazi Jews, an ethnic community within Judaism that describes those who have Central and Eastern European ancestry. Other Jewish ethnic groups include the Sephardi, or Iberian Jews, and Mizrahi, which encompasses those with African and Middle Eastern ancestry. So, there’s evidence that these remains belonged to the Jews victim of the 1190 murder.

One genetic characteristic of the Ashkenazi Jewish population is having predispositions to particular hereditary disorders, such as Tay-Sachs disease, Gaucher disease, and familial dysautonomia. The rise of this risk is often attributed to genetic bottleneck events — in which a population suddenly shrinks for some reason, thus making the gene pool smaller — and high rates of endogamy or marriage within an ethnic or religious group.

Exactly when the bottleneck leading to a risk for hereditary disorders occurred is a mystery. Current theories suggest that it happened within the last 500 to 700 years.

In 2018, Norwich’s Jewish community approached evolutionary biology researcher at the Natural History Museum Ian Barnes, asking him to re-evaluate the data now that technology had advanced. This new research on six of the 17 people, plus computed predictions, show that these 12th-century Jews already had that elevated hereditary disorder risk. Published this week in the journal Current Biology, a study from University College London (UCL) and the Natural History Museum — on which Barnes is a corresponding author — details how this dark historical moment sheds some light on the history of Ashkenazi Jewish genetics.

What’s new — These U.K.-based researchers demonstrate that the Ashkenazi predisposition for genetic disorders dates all the way back to medieval times, pushing back the expected date of the genetic bottleneck.

“What our data suggests is that we need to push back the date of that bottleneck to before the time of the Chapelfield individuals,” corresponding author and UCL evolutionary biology professor Mark Thomas tells Inverse. “My interpretation is that it’s most likely to have been during the formation of Ashkenazi communities in the early Middle Ages.” Thomas cites genetic evidence of mixtures of Jewish and Italian genetics, indicating Jews had lived in the Roman Empire, and then moved into Northern Europe, which served as the bottleneck.

Molecular geneticist Karl Skorecki, who was not involved in the research, offers a cheery visual for a bottleneck. Imagine a big jar of every Skittle variety. Take a handful of Skittles out, and you create a subset of that population, reducing diversity. This reduction creates the bottleneck, so there’s less genetic variation. A bottleneck could result from one group’s migration, famine, or war.

Dean of faculty of medicine at Bar-Ilan University in Israel, Skorecki notes this finding’s scientific and historical gravity. “This study is remarkable,” he tells Inverse, “and at the same time it’s horrific.” The interdisciplinarity, he says, makes this research remarkable, the blend of archaeology, DNA analysis, and computational biology.

Why it matters — There’s little scientific research on the DNA of ancient Jews because, as in many religions, disturbing graves is prohibited. In a moment of macabre serendipity, these researchers only learned after the fact that it’s likely the individuals they investigated were Jewish.

Thomas highlights three keys that make this discovery matter. First, he says, it’s important to the victims and modern community, who were involved in the research and reburial. Second, this data is available to other geneticists for further analysis to better understand not only the Jewish diaspora but other historical diasporas. Lastly, we now know that the genetic bottleneck leading to increased hereditary disorders in Ashkenazi Jews predates medieval times.

Crucially, the researchers detail how bottlenecking and endogamy are related. “There's no such thing as an Ashkenazi Jewish genetic disease, it’s just genetic diseases that are found at a higher frequency,” Thomas emphasizes. Every regional ethnic group is at risk for certain genetic disorders because of multiplying within a certain population.

“There's no evidence of disease due to incest,” Skorecki clarifies. “DNA similarity comes from just having a community marry within itself, but not incestual relations.” That’s not to say incest didn’t occur during medieval times, but bottlenecking itself is not a result of it.

Furthermore, corresponding author Ian Barnes says he noticed these people had lived with a number of non-genetic disorders and nutritional deficiencies that are often associated with hard labor. This detail helps disabuse assumptions and “flexes away from the stereotype of super-wealthy, medieval Jews,” Barnes notes.

Digging into the details — For this analysis, Barnes and Thomas’s team first listed disease variants that occur at higher frequencies in Ashkenazi populations. They identified over 150 places in the genome where a disease-causing variant occurs more frequently in this group than in, say, non-Jews or Sephardic Jews.

Then, when looking at individual genomes, they focused on those with the best-preserved DNA, coming from six people. They sampled a number of different bones with next-generation gene sequencing, paying special attention to the inner ear bone because it’s more sealed from its environment, which means more genetic material found is likely to be human. Other bones that aren’t as protected may mainly show genetic material from bacteria in the soil.

Thomas explains that most genetic diseases are autosomal recessive, which means in order for someone to have the disease, they need a gene for the disorder from both parents.

Next, researchers used computer simulations to extrapolate whether the data they found from these six individuals translated to a higher-than-average frequency for the time period. “The number we observe in the Chapelfield individuals is about what we would expect, if, as a group, those genetic disease variants were in roughly the same frequency then as they are now,” Thomas says. Thomas and Barnes note that six is an awfully small sample size and that their findings flatten myriad nuances that come with population history.

What’s next — One paper that awaits peer review details the whole genome sequencing of 33 Ashkenazi Jews from 14th-century Erfut, Germany. Their findings also corroborate that the bottleneck event had already happened.

However, there’s a loophole that could allow geneticists to test remains. Teeth, Thomas says a rabbi informed him, aren’t permanent body parts, and can therefore be removed and analyzed without trouble. Thomas says he believes the paper on 14th-century German Jews used this method.

Still, he’s not worried about a dearth of evidence. “The database of genomes from ancient individuals is increasing all the time really rapidly,” he says. Even if their fortuitous discovery is unlikely to be repeated, at least their data is available for others to examine.

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