A combination of geophysical and biological research has uncovered long-term evidence for the existence of the bacterium associated with the bubonic plague and major pandemics, like the ‘Black Death‘ (occurring in Afro-Eurasia from 1346 to 1353). During the optimal time of the ‘Black Death’ around 75 million people globally perished, mainly through lymphadenitis.
The new evidence for the longevity of the disease relates to a man who died over 5,300 years ago in Latvia, where the remains were discovered at a Neolithic burial site (the final division of the Stone Age). An examination of the remains (coded RV 2039) shows the man was infected with an early strain of the current bacterium. The researchers detected three Y. pestis-specific proteins in the sample.
The discovery was made after scientists sequenced DNA from the bones and teeth of all four individuals and proceeded to test the genetic material for bacteria and viruses. This revealed an infection (plague) caused by the bacterium Yersinia pestis. The bacterium is associated with what is known as a zoonotic disease, indicating its ability to be transferred between different species. Several species of rodents serve as the main reservoir for Y. pestis in the environment, with infection occurring from the bite of a flea.
The lead researcher, Dr Ben Krause-Kyora of the University of Kiel in Germany, tells the BBC: “Up to now this is the oldest-identified plague victim we have.”
Around the time of death, researchers think the bacterium sporadically moved from animals to humans but large outbreaks were uncommon. It was only later that the organism adapted to infecting humans, manifest as the bubonic plague, that is spread by fleas and raged through medieval Europe, causing millions of deaths. The ‘Plague of Justinian’ in CE 541–542 is the first known attack on record.
The new discovery challenges the ideas about the development of human civilization in Europe and Asia, in that plague did not seemingly spread as fast or as widely as other researchers postulate. This assumption may change in time given there is currently no experimental information available about the pathogenicity of these ancient Y. pestis strains.
In terms of the mode of transmission, the researchers think it is possible that hunter-gatherers, like the man discovered at the burial site, frequently killed rodents for food or personal decoration. This could explain how people of this era contracted Y. pestis or its antecessor (something that goes before) Y. pseudotuberculosis, which was directly from consuming animals.
In this context, with the burial site, beaver (Castor fiber) was the most frequently recorded species among the archeozoological finds excavated.
Of wider importance, the study additionally shows the power of modern DNA sequencing
technology and its ability to detect ancient pathogens. The research is published in the journal Cell Reports. The research paper is titled “A 5,000-year-old hunter-gatherer already plagued by Yersinia pestis.”
