The remains of a 5000-year-old man have been discovered had the oldest known strain of Yersinia pestis, the bacteria responsible for bubonic plague or the Black Death.
Scientists can push back the appearance of Y. pestis 2,000 years farther than previously published studies suggested. The genome of the bacteria reveals that the hunter-gatherer’s plague would have been less contagious, and less deadly, than the famous bubonic plague of the 14th century.
Scientists can see already in this early strain more or less the complete genetic set of Yersinia pestis, and only a few genes are lacking. But even a small shift in genetic settings can have an affected influence on virulence.”
The Yersinia pestis found in the ancient man lacked the gene that allowed fleas to transmit the disease, preventing it from spreading so quickly. The development of this gene was responsible for the reach and severity of the Black Death.
The body of the dead man range between a 20 to 30-year-old called “RV 2039” – was first uncovered in the late 1800s at a site called Riņņukalns in present-day Latvia, and then went missing for almost a century before reappearing in the collection of German anthropologist Rudolph Virchow. He was one of four skeletons found in the same area, thought to belong to the same social group.
Y. pestis was found in the bloodstream, leading researchers to conclude he most likely died from the disease. However, because he had a high quantity of bacteria in his bloodstream at the time of his death, the course of the disease was likely slow – in rodent studies, high bacterial loads of Y. pestis are associated with less aggressive infections.
The people he was buried near were not infected, suggesting the disease did not surge through the community.
The scientists thus conclude that this early form of the disease was slow moving and not highly contagious – challenge prevailing theories about the development of civilisation in Eurasia, which suggest that the plague evolved in high-density megacities of 10,000 people or more near the Black Sea. Instead, this early version was found in a low-density hunter-gatherer community, long before the growth of cities.
The examination of the history of Y. pestis could also potentially shed light on human genomic history.