Ancient plague genomes reveal the origins of the Black Death
In 1347, the plague first entered the Mediterranean through merchant ships carrying goods from the area of the Golden Horde in the Black Sea. The disease then spread across Europe, the Middle East and North Africa, claiming up to 60% of the population in a large-scale outbreak known as the Black Death. This first wave expanded further into a 500-year-long pandemic, the so-called Second Plague Pandemic, which lasted until the early 1800s.
The origin of the Second Plague Pandemic has long been debated. One of the most popular theories has supported its origins in East Asia, especially China. Rather, the only archaeological finds available so far come from Central Asia, close to Lake Issyk Kul, in what is now Kyrgyzstan. These findings show that an epidemic devastated a local trading community in the years 1338 and 1339. Specifically, excavations that took place nearly 140 years ago revealed tombstones that indicated individuals died in those years of an unknown epidemic or “pestilence.” Since their initial discovery, the Syriac-language tombstones have been a cornerstone of controversy among scientists over their relevance to Europe’s Black Death.
In their study published in Nature, an international team of researchers analyzed ancient DNA from human remains, as well as historical and archaeological records from two sites found to contain “pestilence” inscriptions. The team’s early results were very encouraging, as DNA from the plague bacterium, Yersinia pestis, was identified in individuals with the year 1338 on their tombstones. “We were finally able to show that the epidemic mentioned on the headstones was indeed caused by the plague,” said Phil Slavin, one of the lead authors of the study and historian at the University of Sterling, UK.
Researchers find the source strain of Black Death
But could this be the origin of the Black Death? Researchers have previously linked the initiation of the Black Death to a massive diversification of plague species, a so-called Big Bang event of plague diversity. But the exact date of this event could not be precisely estimated and it was thought to have occurred sometime between the 10th and 14th centuries.
The team has now put together entire old plague genomes from the locations in Kyrgyzstan and explored how they might relate to this Big Bang event. “We found that the ancient species from Kyrgyzstan are positioned right at the nexus of this massive diversification event. In other words, we have found the source of the Black Death and we even know the exact date [meaning the year 1338]”, says Maria Spyrou, lead author and researcher at the University of Tübingen.
But where does this species come from? Did it evolve locally or spread from elsewhere in this region? Plague is not a disease of humans; the bacterium survives in wild rodent populations around the world, in so-called plague reservoirs. Hence, the ancient Central Asian tribe that caused the epidemic of 1338-1339 around Lake Issyk Kul must have emerged from such a reservoir.
“We found that modern species most closely related to the ancient species are today found in pest reservoirs around the Tian Shan Mountains, so very close to where the ancient species was found. This points to an origin of the Black Death ancestor.” in Central Asia,” explains Johannes Krause, senior author of the study and director of the Max Planck Institute for Evolutionary Anthropology.
The study shows how research into well-defined archaeological contexts and close collaborations between historians, archaeologists and geneticists can solve major mysteries of our past, such as the origin of the infamous Black Death, with unprecedented precision.
Ancient genomes provide insight into the genetic history of the second plague pandemic
Johannes Krause, The Source of the Black Death in 14th-Century Central Eurasia, Nature (2022). DOI: 10.1038/s41586-022-04800-3† www.nature.com/articles/s41586-022-04800-3
Quote: Ancient plague genomes reveal the origin of the Black Death (2022, June 15) retrieved June 15, 2022 from https://phys.org/news/2022-06-ancient-plague-genomes-reveal-black.html
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