In 2004, construction workers building a mall in Norwich, UK, made a shocking discovery: They found the skeletal remains of seventeen humans at the bottom of a medieval well. The finding grabbed the attention of historians and laypeople alike.
There were indications that suggested the bodies could have been Jewish. Now, scientists have gotten closer to the truth. DNA analysis revealed that they were nearly certain Ashkenazi Jews. The research offers important information on the medical history of the diaspora population and provides the first scientific insights into medieval Ashkenazi Jews’ DNA.
Ashkenazi Jews: A diaspora population
Ashkenazi Jews are a Jewish diaspora population that settled in Germany on the banks of the river Rhine and in Italy sometime before the 12th century. Ashkenazi Jews currently make up about 80% of the world’s Jewish population. They are an interesting group for geneticists because of their low genetic variability.
The high frequency of some of the otherwise uncommon genes in the Ashkenazi Jewish population, and the lack of genetic variability in the population itself, alludes to something called the “founder effect,” which describes a genetic phenomenon that occurs when a small group of individuals becomes separated from a larger population. A population with a founder effect may have genotypes or physical characteristics that are very similar to the original population. This could be due to a “population bottleneck” in America, according the National Human Genome Research Institute.
Geneticists say founder effects happen for different reasons, but often occur in response to something called a “population bottleneck.”
Population bottlenecks occurs when the size of an entire population is sharply reduced by a mass extermination event, like a large volcanic eruption, a tsunami or a genocide.
Researchers found of this sort of bottleneck in the Ashkenazi Jewish population in a 2014 research paper that found that all of the Ashkenazi Jews alive on Earth today can be traced back to around 350 people who lived between 600-800 years ago.
Ashkenazi Jews have experienced a number of bottlenecks over the past centuries due to antisemitic violence, but scientists are particularly interested in this specific bottleneck because it caused genetic variations.
This , published on August 30 in the journal Current Biology, indicates the event could have happened earlier in history. Mark Thomas from University College London, who is the author and evolutionary genetics professor of University College London suggests that the event could have occurred in the middle of the Middle Ages.
Genetic testing on the skeletal remains
The scientists tested in the medieval samples of six individuals found in the well a range of genetic variants known to exist at a higher frequency in Ashkenazi Jews than in non-Ashkenazi Jews today. They found some of the variations.
In order to understand the significance of finding these variations, the researchers did computer simulations, asking the question: How many variations would we expect to find if this population had the same frequencies of disease variants then as Ashkenazi Jews do today? And how many would we expect to find if they had the same frequency as non-Jewish Europeans today?
“The genetic evidence we have seen in these samples suggests that they are from an area where Ashkenazi-associated genetic diseases are about the same as now.” Thomas said. “If that’s the case, then the bottleneck that drove them to high frequency must have [happened] before the vast majority of studies have concluded.”
Ethical issues with the research
This is the first time geneticists have analyzed ancient Ashkenazi Jewish DNA in a peer-reviewed paper, because there are ethical prohibitions against unsettling Jewish graves.
Other inferences regarding the genetic history have been drawn from sequencing Ashkenazi Jewish people who are alive. That’s how researchers made their initial projections about the bottleneck event.
“There is information about the past by looking at DNA today, but it’s not as good as looking at DNA from the past,” said Thomas. It’s better to have your DNA from the past. The same applies if we’re looking at the history of populations, or if we’re trying, for instance, to find signatures natural selection. We can detect it from modern data, but there’s nothing more powerful than detecting it from ancient DNA data.”
Because the researchers did not know anything about the bodies when they began their research, in this instance, it was acceptable.
” In our case, there were no Jewish graves.” Thomas stated. “These were in soil from excavations from a shopping center development, and we would not have known that they were likely Jewish without our work.”
Scientists from Erfurt have published with genetic data from 33 Ashkenazi Jewish people from the 14th century. The paper hasn’t been peer-reviewed, but they say they also observed disease variants associated with Ashkenazi populations.
A scientific view on history
Although this research does not explain how the 17 people died, nor when the bottleneck took place or how, it does help disprove at least one theory about the origins of Ashkenazi Jews: That they descended from the Khazars, a Turkic people who migrated into Europe in the 12th and 13th centuries when their empire was collapsing.
The theory was put forward by Arthur Koestler in his 1976 book The Thirteenth Tribe.
“That’s not going to be true. It’s impossible to explain the data we have on Ashkenazi Jews using that theory. Thomas said, “So that theory is out of the question.”
That’s because this UK data comes from much earlier.
And in regards to the bodies themselves: Once the local Jewish community learned the skeletal remains were of Jewish origin, they facilitated a traditional burial service for them. The researchers have worked closely with the local Chief Rabbi’s office, said Ian Barnes, a molecular evolutionary biologist at the UK’s Natural History Museum. This case has been in his hands for many years.
Edited by: Zulfikar Abbany
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