“It is on a stage of the Silk Road that one of the deadliest pandemics in the history of mankind would have started”, begin Nature in an article intended for the general public. The Black Death, which devastated western Eurasia between 1346 and 1353, killing up to 60% of the population in places, was caused by the rod-shaped bacterium Yersinia pestis. But the precise origin of the killer strain remained unknown.
A study published on June 15 in Nature lift the veil on this mystery : the bacterium that would have started it all was found in three graves dating from 1338 and 1339 located in the villages of Kara-Djigatch and Burana, in what is now Kyrgyzstan, Central Asia. Analysis of the ancient DNA of the seven remains of human bodies present revealed the presence of Y. pestis, whose strain turned out to be the ancestor of that of the Black Death.
The genome sequencing of this strain could be compared with that of other historical and current plague bacilli DNA samples, which made it possible to create a “family tree” of Y. pestis. In Nature, American historian Monica Green, who was not involved in the study, rejoices:
“The discovery of the genome of plague bacilli that predate those that caused the Black Death epidemic is a huge leap forward.”
“The Kara-Djigatch strain is also the ancestor of most strains of Y. pestis circulating today – indicating that Y. pestis would have diversified strongly just before the outbreak of the Black Death”, precise on his side Johannes Krausea paleontologist at the Max Planck Institute in Leipzig, Germany, who led this work. At a press conference he added: “It was kind of like the big bang of the plague.”
Currently, the bacteria Yersinia pestis infects several types of rodents in many countries. “But the plague bacilli seen in marmosets in this part of Kyrgyzstan are genetically closer to ancient samples taken from graves,” pointed out New Scientist, who deciphers:
“This proximity suggests that it was in this region of the world that the bacterium was transmitted to humans for the first time.”
Johannes Krause now hopes to be able to reproduce these analyzes in China to study how this pandemic, which has sown so much terror in Europe, has had repercussions in East Asia. “We would really like to know the Asian part of this episode”, he insists.