(CNN) — Gravestones in what is now Kyrgyzstan have revealed promising details regarding the origins of the Black Death, the world’s most devastating plague outbreak estimated to have wiped out half the European population in the space of seven years during the Middle Ages. .
The origin of that pandemic has been debated by historians for centuries, but inscribed tombstones, some of which referenced a mysterious plague, and genetic material from bodies exhumed from two graves dating back to the 13th century have provided some answers. specific to this old question.
Researchers first excavated the burials in the 1880s. The gravestone inscriptions, written in the Syriac language, were thoroughly re-examined in 2017 by historian Phil Slavin, an associate professor at the University of Stirling, Scotland. He noted that of the 467 burials that were accurately dated, a disproportionate number, 118, occurred in just two years: 1338 and 1339. It’s a revelation he described as “staggering.”
Shown is a view of the Tian Shan mountains in Kyrgyzstan, where scientists have pinpointed the origins of the plague outbreak that caused the Black Death in the Middle Ages.
“When you have one or two years with excess mortality, it means something was going on. But another thing that really struck me is the fact that it wasn’t just any year, because it was only seven or eight years before (the plague) will reach Europe,” Slavin said in a press release.
The inscriptions on the tombstones referred to a mysterious plague.
“I have always been fascinated by the Black Death. And one of my dreams was to be able to solve this enigma of its origins,” he added.
Slavin and his collaborators discovered that the remains of 30 of the individuals buried in the Kyrgyz tombs had been taken to the Peter the Great Museum of Anthropology and Ethnography in St. Petersburg, Russia. The research team got permission to try to extract DNA from the skeletons in order to understand how they had died.
From seven of the individuals, the researchers were able to extract and sequence the DNA from their teeth. In this genetic material, they found DNA from the plague bacterium, which scientists call Yersinia pestis, in three of the individuals, who had the year of death 1338 inscribed on their tombstones.
This confirmed that the plague mentioned on the tombstones was indeed the Black Death, which is transmitted from rodents to humans via fleas.
In 1347, the plague first entered the Mediterranean through trading ships carrying goods from the Black Sea territories. The disease then spread across Europe, the Middle East and North Africa, claiming up to 60% of the population, according to the study published this Wednesday in the journal Nature.
Some historians believe that the strain that caused the Black Death originated in China, while others think that it arose near the Caspian Sea. India has also been raised as a possible origin. The plague strain continued to circulate the world for 500 years.
Shown is the original excavation of the Kara-Djigach cemetery, near Lake Issyk-Kul in Kyrgyzstan.
Evolution of the plague strain
The recent study adds to the wealth of information revealed by the sequencing of ancient pathogens like the plague that leave a genetic imprint on human DNA.
In 2011, scientists for the first time sequenced the genome of the plague bacterium Yersina pestis found in two plague victims buried in a grave in London. Since then, more genetic material has been recovered from graves across Europe and southern Russia.
This work showed an explosion in the diversity of plague strains, a “big bang” that occurred in the evolution of plague bacteria sometime before the Black Death ravaged Europe, most likely in the 10th century. and fourteenth.
Researchers involved in this latest study believe that the area surrounding the two cemeteries near Lake Issyk-Kul in Kyrgyzstan must have been the origin of the plague strain that caused the Black Death, since the two ancient genomes of plague that the team reconstructed from the teeth revealed a single strain of plague that is the most recent direct ancestor of this “big bang” event. This places it right at the beginning of the Black Death outbreak and before it reached Europe.
“We found that ancient strains from Kyrgyzstan lie exactly at the junction of this massive diversification event,” said study lead author Maria Spyrou, a postdoctoral researcher at the University of Tübingen, Germany.
Other evidence supporting the study researchers’ claim comes from comparing plague strains found in modern rodents with those they sequenced from graveyards. They found that the modern strains of plague most closely related to the ancient strain are found today in wild rodents, such as marmots, that live in the Tian Shan mountains in close proximity to the two burial sites.
The epitaph on this tombstone is written in Syriac and reads that “This is the tomb of the believer Sanmaq. [Murió de peste]”.
“What’s really remarkable is that today, in rodents living in that region, we have the closest living relatives of that big bang strain (of plague bacteria),” said lead study author Johannes Krause. , director at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
“Not only did we find the ancestor of the Black Death, but we have found the ancestor of most of the plague strains circulating in the world today.”
There are still many things the team doesn’t know, such as exactly which animal passed the disease to humans. But understanding the origin of the largest pandemic in human history might help prepare for future spreads of the disease, Krause said.
“Like Covid, the Black Death was an emerging disease, and the start of a huge pandemic that lasted for regarding 500 years. It’s very important to understand under what circumstances it emerged,” Krause said.
