What a 5,000-year-old plague victim tells us about the origins of the Black Death

Carl Georg Count Sievers, an amateur archaeologist, performed excavations along the Salaca River in Latvia in 1875. He discovered two graves: one for a 12-to-18-year-old girl (named RV 1852) and another for a 20-to-30-year-old man (designated RV 1853). (RV 2039). Analysis of RV 2039 about 150 years later reveals that not only is he over 5,000 years old, but he also carried an ancient strain of bubonic plague—the oldest instance known to date.

Scientists weren’t expecting to find disease relics when they went in. They were shocked to discover the genome of Yersinia pestis, the pathogenic bacteria that causes the bubonic plague when they genetically tested RV 2039’s remnants. The found strain is the oldest so yet, having separated from its bacterial progenitor almost 7,000 years ago.

It also has a different appearance than the Y. pestis found in recent epidemics. The bubonic plague-inducing germ in the ancient RV 2039 also lacks a vital genetic element: the gene that allows fleas to act as vectors for spreading the plague, which is also the gene that enables the bacterium to infect people efficiently.

Those famed pus-filled buboes (or enlarged lymph nodes, commonly in the armpits or groin) that we associate with the medieval Black Death also caused by the missing gene. Fortunately for RV 2039, his sickness was likely not as terrible, and he avoided the destiny of the Middle Ages’ victims. Scientists determined that his infection was likely modest but long-lasting based on the remnants. Despite this, he most likely died as a result of the infection. The results were reported in the journal Cell Reports.

Instead of being infected by a flea, RV 2039 most likely caught the plague from a larger animal. He was a hunter-gatherer who most likely caught the infection from a bite from an infected rodent—though the study acknowledges that he could have slaughtered a rodent for food or personal decoration and picked it up that way.

Because the plague was still in its early stages, the bacteria couldn’t easily transmit from person to person, which was fortunate for his friends. Y. pestis not found in any of the victims buried in the same area as RV 2039.

“What’s striking is that we see almost the entire genetic set of Y. pestis in this early strain, with only a few genes missing,” said senior author Ben Krause-Kyora, head of the aDNA Laboratory at the University of Kiel in Germany, in a statement. “However, even a minor change in genetic settings can have a significant impact on virulence.”

According to previous views concerning the plague in early human civilization, Y. pestis mainly evolved in cities around the Black Sea, where people lived in close quarters. RV 2039, on the other hand, lived 5,000 years ago, long before humans invented cities. These findings, which reveal that the plague was very weak and non-infectious at the time, also refute claims that the plague was responsible for vast mortality near the end of the Neolithic period, some six millennia ago.

Nonetheless, research like this takes scientists closer to understanding how the Black Death began and how it has altered our genomes. Krause-Kyora explained, “Different pathogens and the human DNA have always developed together.” “We know that Y. pestis destroyed half of the European population in a short period, so it should have a significant influence on the human genome,” says the researcher.