What brought down the Roman Empire? By the end of his The Decline and Fall of the Roman Empire, even the great historian Edward Gibbon was sick of the question. He noted that instead of speculating about the reasons for Rome’s long, slow collapse between (depending on whom you ask) the third and seventh centuries C.E., we should instead marvel that it lasted so long in the first place.

Still, something keeps historians fascinated by the fall of Rome. Proposed explanations include mass lead poisoning (mostly disproved) and moral decay (somewhat difficult to test). One hugely influential revisionist theory holds that Rome never fell at all—it simply transformed into something unrecognizable. In response to this “transformation” interpretation, historians have more recently insisted that late antiquity was characterized above all by violence, death, and economic collapse—an idea most aggressively championed in Bryan Ward-Perkins’ 2005 book, The Fall of Rome and the End of Civilization.

While we may never be able to pinpoint one reason for the death of the Roman Empire, historians are inching ever closer to understanding what life was like for its residents as their world crumbled. Two especially innovative papers published in the latest issue of the Journal of Roman Archaeology ask what role epidemic disease played in the twilight of the Roman Empire. The first, by University of Oklahoma historian Kyle Harper, addresses the so-called Plague of Cyprian in the middle of the turbulent 3rd century C.E. The other, written by Harper’s former professor Michael McCormick, a professor of medieval history at Harvard University, takes on the 6th-century C.E. Plague of Justinian.

In the case of the latter plague, we know the offending pathogen. In a blitz of research over the past decade, three teams of scientists have positively and independently identified DNA from Yersinia pestis—the same bacterium responsible for the Black Death—in skeletons known to date from the time of the Justinianic plague.

Ancient sources make the Justinianic plague sound positively apocalyptic. According to one account, the people of Constantinople—which was by that point the capital of the Eastern Roman, or Byzantine, Empire—died at such enormous rates that the emperor Justinian had to appoint a special officer in charge of coordinating the removal of corpses from the city’s streets. The unlucky appointee, whose name was Theodore, arranged to have the bodies carted across the Golden Horn to Galata, which is now an upscale Istanbul neighborhood. In a gruesomely vivid passage, eyewitness John of Ephesus describes the process.

“[Theodore] made very large pits, inside each of which 70,000 corpses were laid down. He thus appointed men there, who brought down corpses, sorted them and piled them up. They pressed them in rows on top of each other, in the same way as someone presses hay in a loft ... Men and women were trodden down, and in the little space between them the young and infants were pressed down, trodden with the feet and trampled down like spoilt grapes.”

Despite the overwhelming numbers of corpses described in this and other textual sources, no ancient mass graves have yet been found by archaeologists in Galata or, indeed, in any other neighborhood of Istanbul. In fact, no burial pits containing anywhere near 70,000 skeletons have been found anywhere in the Mediterranean, whether dating to the 6th century or to any other period. Historians have good reason to be skeptical of any numbers mentioned in ancient texts, but there’s no doubt that the Justinianic plague claimed enormous numbers of victims across the Mediterranean. Where have all the corpses gone?

As McCormick points out, the incompleteness of archaeological excavations—and especially those in major cities, where obtaining permits and digging around modern infrastructure presents serious challenges—must contribute to the lack of known Justinianic “plague pits.” In fact, the one major Roman city of the 6th century that has been thoroughly excavated, Jerusalem, has been found to contain several mass graves, three of which held over a hundred individual skeletons.

But even if such pits could be found, they wouldn’t account for the full scale of the Justinianic Plague. While cities tend to dominate the historical record due to their concentration of the rich and powerful, the ancient world was overwhelmingly agrarian.

Influenced by the archaeology of the Black Death in London, generations of archaeologists have assumed that mass mortality events go hand in hand with large, communal burials. A close examination of the textual sources reveals, however, that even in London plague pits were not employed until the city’s usual burial places were exhausted. It follows, then, that smaller settlements in the countryside may never have faced the same burial crises as large cities: The combination of more open space and less people would have meant that the majority of the population may never have had to change its burial practices.

One case described by McCormick illustrates and supports this hypothesis beautifully. While analyzing DNA taken from skeletons found in a seemingly unremarkable 6th-century cemetery in the German town of Aschheim, just outside of Munich, scientists were shocked to find that eight individuals’ bones contained traces of Y. pestis DNA. Genetic material degrades over time, so finding six separate, securely identifiable instances is, in fact, a huge deal: It’s likely that many more of the individuals buried in the cemetery were also victims of the Justinianic Plague.

Because the Aschheim cemetery served as the primary burial spot for residents of the small town before, during, and after the Justinianic Plague, the bones found within it are likely to reflect the actual population of the settlement with a high degree of accuracy. As a result, archaeologists can use the skeletal evidence to get a sense of the effect the plague had on this discrete population. The resulting model is shocking: based on cemetery data, “this small rural settlement will have lost a minimum of 35-53 percent of its population within the space of a few months” in 555 C.E., a loss from which it would never fully recover.

The Aschheim case proves that archaeologists should be looking for victims of the Justinianic Plague in any 6th-century settlement that was connected to the late Roman world, regardless of how small or far from Constantinople it is. The work involved will be enormous, but the data collected from this newly exploded pool of potential plague burials will begin to fill in the gaps in our understanding of how devastating the Justinianic Y. pestis outbreak really was.

By contrast, the microbe responsible for Harper’s chosen epidemic, the 3rd-century Plague of Cyprian, remains stubbornly unidentifiable despite various historians’ guesses ranging from smallpox to measles. Tissue taken from skeletons buried around the time of the epidemic in mass graves recently uncovered in Egypt and Rome will surely be analyzed thoroughly. The micro-bioarchaeological methods integral to McCormick’s research, however, seem unlikely to bear fruit for the Plague of Cyprian: relying on ancient descriptions of the disease, Harper argues that the epidemic was probably an outbreak of a viral hemorrhagic fever similar to Yellow Fever or Ebola.

To be sure, the frightening list of symptoms provided by Cyprian (the Carthaginian bishop and eyewitness for whom the plague is named) will sound familiar to anyone who followed the recent West African outbreak of the Ebola virus.

“As the strength of the body is dissolved, the bowels dissipate in a flow; a fire that begins in the inmost depths burns up into wounds in the throat... the intestines are shaken with continuous vomiting ... the eyes are set on fire from the force of the blood ... as weakness prevails through the failures and losses of the bodies, the gait is crippled or the hearing is blocked or the vision is blinded ...”

Unlike bacteria, the majority of viruses—including the Arenaviruses, Flaviviridae, and Filoviruses responsible for viral hemorrhagic fevers—transmit their genetic information via RNA alone. The single strands of RNA are much more fragile than DNA’s double helix, and so are poorly equipped to survive the ravages of time.

Faced with the unlikelihood of genetic evidence, Harper relies on less high-tech methods to figure out how severe the Plague of Cyprian really was. Instead of bones, his evidence is a body of 23 textual sources—some contemporary with the plague and some written much later—that largely frame the epidemic in terms of religious polemic. Plagues in the Mediterranean antiquity, as in many other periods of history, were frequently understood to be supernatural as well as physical disasters. Because the 3rd century was a crucial time of growth and definition for the early Christian church, the Plague of Cyprian came to take on a deep spiritual meaning for pagan and Christian alike.

For Bishop Cyprian, the plague that came to bear his name was hard proof of the superiority of Christianity over traditional Roman religion. Seeing the pestilence as an opportunity to put their most deeply-held beliefs into action, early Christians beatifically set about caring for the sick and giving proper burials to the dead.

On the other side of the religious divide, the pagan establishment was overwhelmed with fear. Traditionally, Roman priests interpreted epidemics as a sign of displeasure from the gods. Evidence in the form of new iconography on coins and references to extraordinary state-organized sacrifices suggests that the Plague of Cyprian was no different. As Harper notes, sources agree that, “the epidemic undermined the social fabric of pagan society” while “the orderly response of the Christian community, especially in the burial of the dead, presented a stark contrast.”

The clearly biased language of both Christian and pagan sources has caused many scholars to discount them as religious propaganda—despite the fact that, if you strip away the pontification, the Christian and pagan accounts agree on all major points, most importantly how contagious, painful, and deadly the disease was. The tendency of some witnesses to slip into stock phrases taken from classic literary descriptions of plagues in Thucydides and Vergil has similarly worked to discredit the textual evidence—unfairly, as Harper argues, because quoting major cultural touchstones was an extremely common way of processing and even emphasizing the severity of shared trauma in antiquity. The disease, he concludes, was one of the nails in the Roman Empire’s coffin, and an important milestone in the growth of early Christianity.

Distinct as their methods are, Harper’s and McCormick’s articles both open up stunning, if gruesome, new vistas on the biological landscape of late antiquity. McCormick’s reevaluation of plague burials makes it clear that the Justinianic Plague spread far beyond major cities, reaching well into Europe’s hinterland—and that historians and archaeologists have likely severely underestimated of the scale and scope of ancient epidemics.

On the other hand, Harper’s careful reanalysis of religious screeds makes clear the necessity of revisiting old textual evidence to reconstruct plagues for which physical evidence is likely to remain elusive. What’s more, the spiritual nature of Harper’s texts reveals how genuinely terrifying the disease regime of late antiquity was. For early Christians, the devastation was something of an opportunity, but for adherents of Rome’s traditional religion, the waves of disease that unrelentingly crashed down on the Mediterranean world were nothing less than the end of the world.