The Plague that brought down mighty empires is thousands of years older than thought

The Plague is far older than previously known and later changed to become much more virulent—so virulent that it may have contributed to the decline of Classical Greece and the Roman and Byzantine empires and later killed off 30 to 50 percent of Europe’s population, a new study says.

The bacteria that causes the Plague, Yersinia pestis, diverged from the less-pathogenic Y. pseudotuberculosis bacterium about 5,783 year ago. That divergence, and therefore the bacteria’s possibility of infecting humans, is much earlier than scholars previously estimated.

While the Plague would go on to kill tens of millions of people in Europe and Asia, researchers have found DNA of Y. pestis in the teeth of a Russian person who died 5,000 years ago. They say that although the plague doesn’t appear to have been as prevalent or as virulent in the Bronze Age, even then it may have triggered migrations of populations in Europe and Asia and caused population decreases.

Writing the in the journal Cell, biologist Simon Rasmussen of the University of Denmark and his team say: “Here, we report the oldest direct evidence of Yersinia pestis identified by ancient DNA in human teeth from Asia and Europe dating from 2,800 to 5,000 years ago. … We find the origins of the Yersinia pestis lineage to be at least two times older than previous estimates. … Our results show that plague infection was endemic in the human populations of Eurasia at least 3,000 years before any historical recordings of pandemics.”

This map of Eurasia shows where and in which cultures the plague bacteria were found and dated; the inset show a burial from the Bulanovo site. (Images from Cell, photo by Mikhail V. Khalyapin)

The Plague, which can be transmitted from humans to humans or from fleas to humans, has broken out in three pandemics in history. They werexSee all ReferencesTreille and Yersin, 1894 the Plague of Justinian (541–544 AD), which continued intermittently until about 750 AD; the Black Death in Europe, which included the first pandemic from 1347–1351, the Great Plague from 1665–1666 and into the 18 ^th century; and the Third Pandemic, which emerged in China in the 1850s and erupted into a major epidemic in 1894, then spread worldwide as a series of epidemics until the mid-20 ^th century. Earlier plagues, from 430-427 BC in Athens and a plague in the Roman Empire from 165-180 AD may or may not have been caused by Y. pestis, the authors say.

Scanning electron micrograph of a flea, which carry disease, including the plague, that infect people when they bite them. (CDC photo/Wikimedia Commons)

By sequencing Y. pestis DNA, the researchers determined the bacterium underwent genetic changes that increased its virulence and led to far more deaths and catastrophic impacts on society that may even have contributed to the collapse of empires. The authors wrote in Cell:

The consequences of the plague pandemics have been well-documented and the demographic impacts were dramatic. The Black Death alone is estimated to have killed 30%–50% of the European population. Economic and political collapses have also been in part attributed to the devastating effects of the plague. The Plague of Justinian is thought to have played a major role in weakening the Byzantine Empire, and the earlier putative plagues have been associated with the decline of Classical Greece and likely undermined the strength of the Roman army.

They concluded in their article that plague was common 3,000 years earlier than historic texts indicate and may have caused die-offs of humans in the late fourth millennium BC and into the early third millennium BC across Eurasia.

“However, based on the absence of crucial virulence genes, unlike the later Y. pestis strains that were responsible for the first to third pandemics, these ancient ancestral Y. pestis strains likely did not have the ability to cause bubonic plague, only pneumonic and septicemic plague,” they wrote.

Bubonic plague is transmitted by fleas, so this means the Plague likely was transmitted solely by humans earlier in its epidemiology. Around the late second millennium and early first millennium BC, the plague began to be spread by fleas via rats—an extremely rapid mode of transmission. Pneumonic plague affects the lungs, and septicemic plague affects the blood.

Phys.org, reporting on the new research, wrote that the Books of Samuel in the Old Testament of the Bible tell of a plague among the Philistines in 1320 BC. The people suffering from it had swellings in the groin. The World Health Organization says such swellings are consistent with bubonic plague. The authors say this may indicate that the highly lethal bubonic plague originated in the Middle East.

Featured image: St Macarius of Ghent Giving Aid to the Plague Victims, 1673 painting by Jacob van Oost (Wikimedia Commons)

By Mark Miller