For the First Time, Scientists Extract Black Plague DNA From an Ancient Bone of an Animal That Died 4,000 Years Ago

Few diseases have left a scar on humanity as deep as the Black Death. The plague killed roughly one-third of Europe’s population in the mid-1300s, powered by Yersinia pestis and its terrifying ability to spread through flea bites. But that medieval catastrophe, as monstrous as it was, was not the first chapter. Scientists have long known, through the DNA of Bronze Age humans, that a related strain of Y. pestis was already circulating across Eurasia for more than two millennia before the medieval outbreak, a darker, older prequel that most people have never heard of.

What they didn’t know, until now, was that livestock were part of the story. A new study, published in the journal Cell, reports the discovery of Y. pestis DNA in the 4,000-year-old remains of a domesticated sheep, originally recovered from Arkaim, a Bronze Age settlement located in the southern Ural mountains, along the border of present-day Russia and Kazakhstan. It is a find that complicates, and enriches, everything researchers thought they understood about how the ancient plague moved.

A Tiny Fragment With a Massive Implication

The work was neither easy nor straightforward. The DNA fragments recovered from the sheep remains were extraordinarily small, some containing only 50 base pairs. To put that into perspective, a full human genome contains around 3 billion base pairs. Working against difficult preservation conditions and the ever-present risk of soil contamination, archaeologist Taylor Hermes and his team at the University of Arkansas painstakingly pieced the evidence together.

What they found stopped them cold. According to Hermes, in a press statement: “It was alarm bells for my team. This was the first time we had recovered the genome from Yersinia pestis in a non-human sample.” The sheep bones had been sitting in excavation storage, largely unremarkable to the outside world, until they weren’t.

The Sintashta Culture and the Perfect Storm

The sheep did not exist in a vacuum. Arkaim, 4,000 years ago, was home to the Sintashta culture, a civilization known for its impressive bronze armaments and, crucially, its mastery of horse riding. Members of the Sintashta also managed large groups of livestock while expanding across the continent. According to the study published in Cell, this combination essentially created a perfect storm of disease transmission through increased animal interaction.

That context matters enormously. The same strain of Bronze Age Y. pestis has been found in populations thousands of kilometers apart, and the sheep discovery begins to explain how. It was, as Hermes put it, “more than people moving.”

One Answer, and a Reservoir Still Unnamed

The find also reopens a question that a 2015 study, also published in Cell, had attempted to settle. That earlier research had found that the Bronze Age strain of Y. pestis was missing the Yersinia murine toxin, the gene that allows the bacterium to survive inside a flea’s gut. Without it, researchers concluded, the ancient plague must have spread through airborne droplets, contaminated food, or the exchange of bodily fluids, not through fleas.

The sheep discovery doesn’t contradict that conclusion, but it adds new dimensions to it. According to Hermes, the picture is now “a dynamic between people, livestock and some still unidentified natural reservoir,” which he suggested could be rodents on the grasslands of the Eurasian steppe or migratory birds. The medieval plague found its reservoir in rats. Ebola found its in fruit bats across sub-Saharan Africa. The Bronze Age plague, it seems, had its own silent carrier, it just hasn’t been identified yet.

As Popular Mechanics reported, the COVID-19 pandemic reminded the world that pestilence is an inevitable part of being human. This discovery, quiet and ancient as it is, carries the same uncomfortable message.