The plague probably didn’t wipe out the Roman Empire and half the world’s population, new study suggests

Plague is often depicted as shifting the course of human history, but scholars say an outbreak that has been blamed for the demise of the Roman Empire likely didn’t kill half the world’s population in just a few years.

A new study published Monday explores the effects of the first recorded plague pandemic, known as the Justinianic Plague, that was thought to have swept the world starting from the year 541. Many scholars believe the outbreak was a landmark event that led to significant demographic, economic and political changes in the period known as Late Antiquity — much as the Black Death devastated Europe in the Middle Ages.

“If this plague was a key moment in human history that killed between a third and half the population of the Mediterranean world in just a few years, as is often claimed, we should have evidence for it — but our survey of data sets found none,” said Lee Mordechai, a postdoctoral fellow at the University of Maryland’s National Socio-Environmental Synthesis Center.

An international team of historians looked at a diverse range of data to investigate the effects of the outbreak, including historical texts, coin circulation, burial practices, pollen samples, stone inscriptions, mortuary archaeology and plague genomes.

They found that the number of deaths caused by the outbreak may have been overestimated, and that the plague did not play a significant role in the transformation of the Mediterranean world or Europe. It also didn’t play a key role in the fall of the Roman Empire.

Mordechai, who is also co-lead of Princeton’s Climate Change and History Research Initiative (CCHRI), said that over the past two decades historians have placed more emphasis on the plague as a cause of historical effect and had increasingly featured it as a factor in the decline of the Roman Empire.

“Extraordinary claims demand extraordinary evidence. We find little evidential support for the claim that the JP [Justinianic Plague] was a watershed event,” the study, which was published in the journal Proceedings of the National Academy of Sciences, concluded.

The authors said previous scholars focused on the most evocative written accounts, applying them to other places in the Mediterranean world while ignoring hundreds of contemporary texts that did not mention the Justinianic Plague.

Data-driven approach to history

Unlike during the Black Death, when the vast numbers of people killed by the plague resulted in mass graves, the team found no significant evidence that the numbers of graves containing more than one person increased.

“We investigated a large data set of human burials from before and after the plague outbreak, and the plague did not result in a significant change whether people buried the dead alone or with many others,” said co-author Janet Kay, a lecturer in the Council of the Humanities and History and the CSLA-Cotsen postdoctoral fellow in Late Antiquity at Princeton University.

Similarly, the amount of cereal pollen — which can be found in lake or peat sediment — did not decrease as it had during the Black Death.

“We used pollen evidence to estimate agricultural production, which shows no decrease associable with plague mortality. If there were fewer people working the land, this should have shown up in pollen, but it has failed to so far,” said co-author Adam Izdebski, a member of CCHRI who is now a research group leader at the Max Planck Institute for the Science of Human History and an assistant professor of history at Jagiellonian University in Krakow, Poland.

Mordechai told CNN this data-driven approach to history did have some limitations.

“None of the data sets is perfect. But at the moment they are the best thing we have,” he said. “Future researchers could find different sources of data that disagree with our conclusions.”

He said that the study was an unusual collaboration between several scholars in different fields, bringing together historians, archaeologists and scientists.

“It’s easy to assume infectious diseases in the past would have catastrophic results. Yet, we used every type of data set we could get our hands on, without assuming a disease outbreak must result in catastrophic results, i.e. that tens of millions died. We found no evidence in any of these data sets to suggest such a destructive outcome,” Mordechai said.

“This paper was only possible by working with a diverse disciplinary team, and we hope our work will start a new collaborative discussion of the impact of past disease outbreaks.”

The plague pandemic is named after Justinian I, who was emperor of the Byzantine, or Eastern Roman, Empire at the time of the initial outbreak. Justinian himself caught the disease but survived.