Long before the Black Death, the plague entered Europe
Genetic analysis pins a Stone Age arrival for history’s mass killer. Andrew Masterson reports.
In the Late Neolithic period, around about 4800 years ago, waves of people migrated into Europe, coming up through central Asia and the Middle East. They brought with them tools and artefacts and animals – and one other, considerably less welcome, bit of cargo.
The highly virulent, highly lethal and extremely gruesome epidemic mayhem caused by the bacterium Yersina pestis unambiguously enters the European historical record in the Fourteenth Century, in the form of the Black Death.
Few epidemiologists or microbiologists think this was its actual debut, however. Historical records clearly show several other plague-like epidemics in preceding centuries, but the pathology that would allow a definitive identification of the cause is lacking.
The Plague of Athens (430-427 BCE), the Antonine Plague (165-180 CE) and the Plague of Justinian (541-542 CE) may all have been caused by Y.pestis. Without conclusive evidence, however, it remains possible that they were caused by other pathogens, such as smallpox or typhus. One study even suggests that the Athenian tragedy might have been caused by Ebola.
Research by a team from the Max Planck Institute for the Science of Human History, in Germany, has now established that whatever the cause of the ancient plagues, the presence of plague bacteria in Europe was more ancient still.
The scientists, led by Aida Andrades Valtueña, gathered together over 500 samples of human bone and tooth from Latvia, Estonia, Germany, Russia, Hungary and Croatia, all of them dating from between 4800 years ago to the start of the Bronze Age 1000 years later.
Each of the specimens was examined microscopically, with the researchers hunting for signs of Y.pestis. In the end, they recovered six complete genomes of the bacterium, from different locations in the search zone.
Sequencing the recovered DNA, Valtueña and her colleagues discovered that all six were closely related.
"This suggests that the plague either entered Europe multiple times during this period from the same reservoir, or entered once in the Stone Age and remained there," she says.
To try to clarify the picture still further, the researchers turned to population history, and focussed on the well-established large influx of migrants from Caspian-Pontic Steppe 4800 years ago. Today, almost all Europeans carry genetic markers originating in this group.
It did not escape the researchers’ notice that their earliest dating for the arrival of Y.pestis in Europe coincided with this influx.
The evidence therefore suggests that the plague entered Europe with the steppe nomads and successfully established a reservoir.
Ironically, the researchers suggest, the en masse entry of the migrants into Europe might represent a titanic own-goal.
"The threat of Y. pestis infections may have been one of the causes for the increased mobility during the late Neolithic-early Bronze Age period,” says co-author Johannes Krause.
In other words, the people of the steppes might have flooded from their homelands precisely because the plague was laying waste to it.
The research is published in the journal Current Biology.