The chance discovery of 17 skeletons by construction workers building a shopping centre in Norwich has shed light on a centuries-old cold case.
The pile of human bones was found at the bottom of an ancient well at the site of Chapelfield Shopping Centre in 2004.
Gene sequencing revealed the remains of six adults and 11 children which probably belonged to Jews murdered in the medieval period in the 12th century.
That makes them the source of the earliest Jewish genomes, some of which are associated with diseases and population traits, including the presence of red hair.
They may have died tragic deaths because they were not found in a burial ground, suggesting “they may have been victims of a mass fatality event such as famine, disease, or mass murder,” wrote the authors of the study, which has been published in Current Biology.
Radiocarbon dating placed the skeletons in the 11th to 12th centuries.
“The most prominent historically attested mass death in Norwich within this date range was in 1190 CE when members of the Jewish community were killed during anti-Semitic riots precipitated by the beginning of the Third Crusade,” they wrote.
Further confirmation of the link to the cold case came after sequencing found “strong genetic affinities with modern Ashkenazi Jews,” suggesting they were ancestors, and the earliest found so far.
Ashkenazi Jews are a diaspora which established communities in Germany near the river Rhine and in Italy before the 12th century. A number of conditions are found more commonly in the population due to the prevalence of mutated genes.
“We identif[ed] four alleles associated with genetic disease in Ashkenazi Jewish populations and infer variation in pigmentation traits, including the presence of red hair,” wrote the study authors.
They also had gene variations which were believed to have emerged far later in the population.
Analysis showed the victims were also predisposed to some genetic conditions, such as primary ciliary dyskinesia, which are prevalent in modern Ashkenazi Jews. The condition prevents the clearance of mucous from the lungs, paranasal sinuses and middle ears, and leads to frequent respiratory conditions.
Experts say these conditions were caused after the Ashkenazi Jewish population suddenly shrank 500 to 800 years ago, resulting in what is known as a genetic bottleneck.
That occurs when a dramatic decrease in population limits genetic diversity, increasing the frequency of rare variants in future generations.
For this reason, Ashkenazi Jews from the 12th century would not have been expected to have these variations.
So the theory about when the genetic bottleneck occurred may be wrong, according to the authors.
“The bottleneck that drove up their frequency must be before the [Norwich individuals],” study co-author Mark Thomas, an evolutionary geneticist at University College London told Nature.
“That puts it back older than the vast majority of estimates of when that bottleneck occurred.”