The plague ravaged mankind for thousands of years, possibly wiping out up to half the population of Europe in the 14th century during the Black Death. But scientists have long been puzzled about its origin and evolution.
The man in question, called RV 2039, was in his twenties. His skeleton was found at the end of the 19th century, but was later extinct before being rediscovered in 2011. His remains showcase the bacteria. Yersinia pestis, according to this work published in the journal Cell Reports.
Analyzes of the strain we have identified show that Y. pestis evolved earlier than we thought, declared to AFP Ben Krause-Kyora, of Kiel University.
Scientists say this strain is part of a lineage that emerged around 7,000 years ago, 2,000 years older than previously established.
Falling on this bacteria was
really a surprise, said Ben Krause-Kyora. The team of scientists were initially looking to establish a possible family link between this man and three other people found in the same place, when they made this discovery.
Yersinia pestis likely killed the individual, although researchers believe the disease was slow. He had high levels of this bacteria in his blood at the time of his death, which has been associated with less aggressive infections in rodents.
The people around him had not caught the disease, which seems to show that he was not infected with pulmonary plague, a highly contagious form of plague.
RV 2039 must have been infected from a rodent bite, scientists say.
The found bacteria are missing key genes, such as the one that allows fleas to transmit the disease. This old version was therefore less contagious and deadly than the medieval version.
The most recent strain of plague that can be transmitted by fleas dates back around 3,800 years, when cities of more than 10,000 people began to form.
The increasing population density probably caused the evolution of the bacteria.
Trace the history of Yersinia pestis could help to understand how the human himself evolved to defend himself, according to Ben Krause-Kyora:
We are very interested in future studies on how these ancient infectious diseases influenced our current immune system..