Researchers may know the origin of the Black Death that killed 200 million people

The Black Death plague wiped out more than 30 percent of Europe’s population and led to hundreds of millions of deaths globally in the mid-14th century. It is considered one of the deadliest pandemic ever witnessed by humanity (far deadlier than COVID-19, that have taken 6.31 million lives so far). However, surprisingly, historians are still not sure when and how it started. Now a team of international researchers has claimed that they have discovered the true origin of the Black Death bubonic plague.

About 140 years ago, archaeologists found tombstones with inscriptions in Syriac language suggesting that the individuals who were buried in the tombstones died of an unidentifiable plague. The authors of the recent study collected and studied ancient human DNA samples collected from two sites where the plague (also referred to as “pestilence”) inscriptions were initially discovered. 

According to the researchers, the data obtained from the DNA samples have revealed information that can finally put an end to the many debates that revolve around Black Death’s origin.

The true beginning of the Black Death plague    

Black Death is actually a bacterial infection carried by wild rodents. The disease is still diagnosed in humans, but today it can be easily treated using antibiotics. Researchers have discovered multiple strains (genetic material) in the past, suggesting that the Black Death plague may have occurred between the 900s and 1300s. However, none of those discoveries could reveal the exact year when the infection appeared for the first time.

The evolutionary event that resulted in many new branches of the Yersinia Pestis lineage (Y. pestis is the bacteria that caused the Black Death infection) is referred to as the Big Bang of plague diversity. It has led to the many strains discovered by researchers in the past and is responsible for the confusion related to the origin of the Black Death.

While highlighting the deadly and obscure nature of the disease, one of the authors of the study and History Professor at the University of Stirling, Philip Slavin told IE. He added that “the Black Death appears to have been the single deadliest human pandemic in known history, claiming some 50-60 percent of the total population of West Eurasia in the course of some 7 years (1346-53). Its origins have been intriguing to both 14th-century contemporary and ‘modern’ historians and scientists. But up until now, the geographic and chronological origins of the Black Death have been debated, but unknown.”   

During their study, the researchers collected DNA samples from the teeth of the human remains of seven individuals that died because of the pestilence. They didn’t extract DNA from any other body part because teeth stay preserved even after a person’s death and contain preserved pathogens. The analysis of the genetic material revealed the presence of the plague bacterium Yersinia pestis in three individuals.

Professor Slavin pointed out that out of three, the genome from two had enough information to trace the plague's origin. He said, “Yersinia pestis was detected in all three individuals. As you noted, after ‘so many years have passed’ some samples get more prone than others to ‘environmental contamination, which presents some challenges.” He further added, “only 2 out of 3 teeth had sufficient genomic coverage, but it was good enough to combine them together for an increased genomic resolution, which yielded a very clear picture. The high coverage of 2 (out of 3) samples allowed us to determine their evolutionary position on the phylogenetic tree.”

The findings from the DNA analysis revealed that the Black Death plague first spread between 1338 and 1339 among the members of a community living near Lake Issyk Kul in Central Asia (the place is now called Kyrgyzstan). The lead author of the study and postdoctoral researcher at the University of Tübingen, Maria Spyrou, writes, “we found that the ancient strains from Kyrgyzstan are positioned exactly at the node of this massive diversification event (Big Bang). In other words, we found the Black Death’s source strain and know its exact date (meaning the year 1338).

Why do these findings concerning the Black Death matter now?

The researchers of the study believe that to understand the phenomenon of emerging epidemic diseases, it is essential to have as bigger an evolutionary picture as possible. The information (such as the data collected from different strains) about the origin of past diseases like plagues can help us understand how pandemics develop and transmit over the course of time. Moreover, it plays a crucial role in increasing our knowledge of the history and evolution of a disease.

They also highlight that more plague DNA research is a fast-growing field and more studies and experiments need to be conducted to further confirm their finding on Black Death.

The study is published in the journal Nature. 

Abstract: 

The origin of the medieval Black Death pandemic (AD 1346–1353) has been a topic of continuous investigation because of the pandemic’s extensive demographic impact and long-lasting consequences1,2. Until now, the most debated archaeological evidence potentially associated with the pandemic’s initiation derives from cemeteries located near Lake Issyk-Kul of modern-day Kyrgyzstan1,3,4,5,6,7,8,9. These sites are thought to have housed victims of a fourteenth-century epidemic as tombstone inscriptions directly dated to 1338–1339 state ‘pestilence’ as the cause of death for the buried individuals9. Here we report ancient DNA data from seven individuals exhumed from two of these cemeteries, Kara-Djigach and Burana. Our synthesis of archaeological, historical and ancient genomic data shows a clear involvement of the plague bacterium Yersinia pestis in this epidemic event. Two reconstructed ancient Y. pestis genomes represent a single strain and are identified as the most recent common ancestor of a major diversification commonly associated with the pandemic’s emergence, here dated to the first half of the fourteenth century. Comparisons with present-day diversity from Y. pestis reservoirs in the extended Tian Shan region support a local emergence of the recovered ancient strain. Through multiple lines of evidence, our data support an early fourteenth-century source of the second plague pandemic in central Eurasia.