Challenging the Predominant Theory of the Black Death

FROM THE LECTURE SERIES: The Black Death: The World's Most Devastating Plague

By Dorsey Armstrong, Ph.D., Purdue University

The Black Death is among the most important events that shaped the middle ages. It had an undeniable impact on many of the great minds of that era and was the biggest turning point in the entire 1,000-year span of the medieval period.

The painting shows horsemen of death about to attack people.
The Black Death wiped out up to half of the population. (Image: matrioshka/Shutterstock)

Death Comes for All

Starting around 1346, a plague swept across the present-day Western Europe, moving east to west and wiping out up to half of the population. News of the epidemic was spreading ahead of the disease itself, and people who knew it was coming were all the more terrified.

What made matters worse was the utter defenselessness of the public. To ward off the disease, people came up with all sorts of desperate strategies. Some carried flowers or strong-smelling herbs in front of their faces, believing that this might fend off the illness. And many took the commonsensical approach of refusing to use spices or purchase fabrics and other goods that had come by ship from plague-infected areas.

This is a transcript from the video series The Black Death: The World’s Most Devastating Plague. Watch it now, on The Great Courses Plus.

How Did It All Begin?

The predominant theory of the Black Death’s origin points to a climatic event in China around 1346 that caused the black rat population to leave its primary habitat and move into areas that brought them into contact with humans. Based on this theory, when the rat population had a sudden die-off, rat fleas jumped to human hosts.

Thereupon, humans, rats and other animals brought the plague with them along the trade routes that were moving east to west in the medieval world.

Large-scale Urbanization in Europe

Population growth and large-scale urbanization are also believed to have contributed to the outbreak of the plague.

Between the years 1000-1300, the population of the medieval world had doubled. Advances in agricultural practices meant that more people had access to proper food, leading to an increased rate of survival and reproduction.

By the mid-14th century, demand was outstripping supply. People crowded into cities as a merchant economy began to challenge the traditional Three Estates social order of clergy, nobility and commoners that had existed for generations.

New Perspectives

In recent years, several scholars have suggested that while the plague may have been partially responsible for the high mortality rates in the middle of the 14th century, the virulence and speed with which death swept through Western Europe doesn’t completely make sense.

One fact that paves the way for this argument is the natural immunity of 10-20 percent of the population of Western Europe to HIV/AIDS. This mutation appears to be connected to having an ancestor who survived the plague.

At first, this doesn’t make any sense, as the plague is bacterial and HIV/AIDS is viral. But it becomes very clear if we take into account what was sweeping across the continent was not only bubonic plague but some kind of hemorrhagic fever.

There are other theories about different exogenously occurring events that contributed to the devastation of the Great Mortality.

Learn more about the great plague.

Challenging the Official Theory

An image of a black rat.
It is commonly believed that the plague originated from rat fleas. (Image: Everett Collection /Shutterstock)

Late historian David Herlihy, a specialist who worked extensively on medieval Italy, made use of some under-studied contemporary sources related to the plague and drew several interesting conclusions.

He points out that almost nowhere in the accounts of medieval plague’s advance does anyone mention an epizootic event. An example of such an event would be a massive die-off of rats (primary host of black fleas bringing them in contact with humans).

Did medieval people just miss noticing this die-off? It seems unlikely. They sought explanations for the epidemic sweeping through the medieval world from various sources, from erupting volcanoes on other parts of the globe to a particular alignment of the planets.

Other Conclusions by Herlihy

Herlihy also challenges the argument that the Black Death moved along trade routes. Unless dealing with the pneumonic plague, humans cannot infect other humans, so a huge number of infected rats and their fleas would have to be moving westward in caravans and onboard ships for the mainstream theory to hold water.

Furthermore, the plague seemed to move in seasonal cycles—getting worse in the summer, disappearing in winter, and then reappearing again with warmer weather. Usually, in cold weather people are indoors, humans and rats come in repeated contact, and greater proximity of individuals makes the transmission of the pneumonic form of the plague much more probable.

 Learn more about the three predominant varieties of plague.

Multiple Forms of Plague

The medieval physician Guy de Chauliac, who served in the papal court, argued there were multiple forms of the plague, and perhaps diseases other than plague, moving through the world at the time of the Black Death. He described an extremely contagious illness that produced high fever and coughing up of blood (usually killing its victims within three days). This disease sounds more like a virulent strain of tuberculosis than the plague.

Beginning from the first big wave of the plague in 1377, authorities responsible for preparing bodies for burial would note the cause of death. By 1424, however, they came up with a new way of recording the cause. If someone had died of the plague, the notation just mentioned de segno, or with the sign, and there would often be a big P in the margin of the book as well. The evidence suggests that these later outbreaks were considered a new disease.

Many of the documents describing the cause of death don’t mention buboes at all or do so sporadically. In the surviving documents from Viterbo, Italy, marks on the body that resemble freckles are mentioned. In medieval England, we see references to the Blue Sickness.

These diverging descriptions question the legitimacy of bubonic plague as the cause of the Black Death and hint at new and extraordinary alternatives.

Common Questions about the Predominant Theory of Black Death

Q: What were some of the strategies medieval people used to ward off the plague?

People came up with desperate strategies to fight the Black Death. Some carried flowers or strong-smelling herbs in front of their faces. Many refused to use spices or purchase fabrics and other goods that had come by ship from plague-infected areas.

Q: What is the predominant theory of the Black Death’s origin?

The predominant theory of the Black Death’s origin points to a climatic event in China around 1346 that caused the black rat population to leave its primary habitat and move into areas that brought them into contact with humans. When the rat population experienced a sudden die-off, the fleas on the rats jumped to human hosts.

Q: How does David Herlihy challenge the argument that the Black Death moved along trade routes?

David Herlihy challenges the argument that the Black Death moved along trade routes by saying that unless dealing with the pneumonic plague, humans cannot infect other humans. So, a huge number of infected rats and their fleas would have to be moving westward in caravans and onboard ships for the mainstream theory to hold water.

Keep Reading
The Black Death: Is The Plague Still A Threat?
Europe on the Brink of the Black Death: The Plague Begins
How Europe’s Population in the Middle Ages Doubled