The Black Death plague killed more than 30% of Europe’s population in the mid-14th century and caused hundreds of millions of deaths worldwide. It is considered one of the deadliest pandemics humankind has ever experienced (much more deadly than COVID19, which has claimed 6.31 million lives so far). Surprisingly, however, historians are still unsure when and how it began. Now a team of international researchers have claimed they have discovered the true origin of Black Death bubonic plague.
About 140 years-ago, archaeologists found tombstones with Syriac language inscriptions suggesting that the people who were buried on the tombstones died from an unidentifiable plague. The authors of the latest study collected and examined ancient samples of human DNA collected from 2 sites where the plague (also known as “pestilence”) inscriptions were originally discovered.
According to the researchers, the data obtained from the DNA samples has unearthed information that could finally put an end to the many debates revolve around the origins of the Black Death.
True beginning of Black Death plague
The Black Death is actually a bacterial infection spread by wild rodents. The disease is still diagnosed in humans but is now easily treated with antibiotics. Researchers have discovered several strains (genetic material) in the past, suggesting that the Black Death plague may have appeared between the years 900s & 1300s. However, none of these discoveries could pinpoint the exact year in which the infection first appeared.
The evolutionary event that gave rise to many new branches of the Yersinia pestis lineage (Y.pestis is the bacterium that caused the Black Death infection) is known as the Big Bang of plague diversity. It has led to many-strains discovered by researchers in the past and is responsible for the confusion related to origin of the Black Death.
One of the study’s authors & professor of history at the University of Stirling, Philip Slavin, highligting the dark & deadly nature of the disease He added that “Black Death appears to have been the deadliest human pandemic in known history, claiming approximately 50% to 60% of the total population of western Eurasia over the course of approximately 7 years (1346-53). Its origins were fascinating to contemporary and “modern” historians & scientists of the 14th century. But until now, the geographical & chronological origins of Black Death have been debated but are unknown.”
During their study, the researchers collected DNA samples from the teeth of the human remains of seven people who died from the plague. They didn’t extract DNA from other parts of the body because teeth preserved even after a person dies & contain preserved pathogens. .The analysis of the genetic material revealed the presence of the plague bacterium Yersinia pestis in 3 people.
Professor Slavin found that the genomes of two out of three contained enough information to trace the origin of the plague. He said: “Yersinia pestis was detected in all 3 individuals. As you pointed out, after ‘so many years’, some samples become more susceptible to ‘environmental contamination’ than others, which presents some challenges.” He added: “Only 2 out of 3 teeth had sufficient genomic coverage, but it was good enough to combine them to get increased genomic resolution, giving a very clear picture. The high coverage of 2 (out of 3) samples allowed their evolutionary position to be determined.” on the phylogenetic tree.
Results from DNA analysis showed that the Black Death plague first spread among members of a community living near Lake Issyk-Kul in Central Asia (the place is now called Kyrgyzstan) between 1338 and 1339.
The study’s lead author and postdoctoral researcher at the University of Tübingen, Maria Spyrou, writes: “We found that ancient strains from Kyrgyzstan are positioned right at the node of this massive diversification event (Big Bang). In other words, we have found the source strain of the Black Death and we know its exact date (ie the year 1338).
Why do these findings concerning the Black Death matter now?
The study’s researchers believe that to understand phenomenon of emerging epidemic diseases, it is essential to have as bigger an evolutionary picture as possible. Information (e.g. data collected from different strains) about the origin of past diseases such as plagues can help us understand how pandemics develop & spread over time. In addition, it plays a crucial role in expanding our knowledge of the history and evolution of a disease.
They also emphasize that more research into plague DNA is a rapidly growing area and more studies & experiments need to be conducted to further confirm their findings on the Black Death.
The study is published in the journal Nature.