How Our Understanding of the Black Death Has Been Advanced By Genomic Evidence - & A Study Of Medieval History

14th-century painting with Belgian citizens burying the victims of the Black Death

            St. Sebastan Chapel in Garmisch, Germany, showing Black Death striking villagers

In a recent (June 12)  WSJ Review piece (Black Death: Shadow Over the World)  by Kyle Harper, we read:

"In the immediate aftermath of the 14th-century Black Death, a highly educated Venetian wrote a chronicle claiming that the plague had wiped out a third of his city’s population. Another account from Venice, composed around the same time, claimed that more than half were lost in the pandemic. 

"A remarkable inscription in the Scuola Grande di Santa Maria della Carità (a kind of 14th-century Knights of Columbus) carved right after the outbreak put the city’s death toll at two out of three. Yet another Venetian chronicler claimed seven out of 10. And by the reckoning of one observer, the mortality carried off three out of every four inhabitants.

Welcome to the challenges of writing the history of the Black Death, the great pandemic of bubonic plague that ravaged the late medieval world. "

Ravaged is correct. And we saw some of the lasting residue when we traveled to Garmisch, Germany in 2013 and beheld the detailed art work on St.Sebastian Chapel wall, not far from our guest house. 

After ten minutes or so in the chapel, noting the fetid odor, we exited at the rear and walked outside to find a green expanse of about an acre. On entry, we saw a small notice that this hallowed ground (extending behind the chapel)  formed a "cemetery". Oddly, there were no grave markers. Evidently, at least 1, 100 plague victims were simply buried in unmarked graves. Likely these victims made up the faithful of the small congregation, while others ..e.g. unbelievers, witches, or Jews who perished, simply had their bodies consigned to huge funeral pyres -  actually manifested throughout Europe during the Black Death. (Europe lost an estimated one-third of its then population.)

                                       Plague mask displayed in Oberammergau

                                  Plague reaper in Oberammergau town square

A few days later, our German friends Reinhardt and Elli drove us to Oberammergau.  There they pointed out  engraved iron works displaying other unsettling images of the Plague "Reaper".  These were often accompanied by prayers or other pleas to spare the town. Reinhardt related that the plague toll was fearsome with so many corpses piled up in the streets and few places to put them.  Most had to be carted away to be incinerated in open pits.

In regard to the WSJ reviewer's issues, here is the problem: there were multiple waves of the Black Death - with different intensity or 'ferocity' if you will. What he focuses on is the 14th century version. But what we beheld in our German visit were the inescapable residues of the 17th century version.  What gives?  

The 14th-century Black Death and later 17th-century outbreaks (like the Great Plague of London) were later found to be distinct, centuries-separated waves of the same continuous pandemic. They were also found to be genetically related, driven by the same bacteria (Yersinia pestis), but which differed significantly in how rapidly it spread and how society responded in each era.

The target flea for the Yersinias pestis bacterium is Xenopsylla cheopsis. Once it infects this flea, Yersinias' tendency is to keep on multiplying until it eventually totally blocks the flea's oesophagus making the critter chronically thirsty. The flea must then seek blood sources, i.e. rodents, humans. Since rats are the most prolific, and especially at the times of the plague bred relentlessly because of horrific hygienic conditions, they were the primary vectors.

The Black Death (1347–1351) marked the devastating start of the "Second Plague Pandemic." (the first occurring over 527- 565, during the reign of the Roman Emperor Justinian, and hence called 'the Plague of Justinian') This wave did not end in the 1300s; rather, it repeatedly recurred across Europe, the Middle East, and North Africa for over 300 years, culminating in major 17th-century events like the Great Plague of London (1665–1666).

Despite the 300-year gap, medical knowledge barely advanced. In both the 14th and 17th centuries, people did not know about germs and attributed the plagues to divine punishment, the alignment of the stars, or "miasma" (bad air).

During the 14th-century Black Death, the Italian city of Venice originated the concept of isolating victims. By the 17th century, these practices had evolved into highly organized systems. In 1665, London strictly enforced quarantines by boarding up infected households and marking their doors with a red cross.

Ultimately, while the 14th-century Black Death was a sudden, apocalyptic shock to a completely naive population, 17th-century outbreaks were part of a long-established, evolving disease cycle within a society that was actively learning how to isolate and manage the spread.  

The WSJ reviewer specifically zooms in on Thomas Asbridge and his take in a recent book, noting:

"One contemporary Florentine writer considered it the worst natural disaster since the biblical flood. In “The Black Death: A Global History of Humanity’s Most Devastating Pandemic,” a vivid and sweeping new history of the outbreak, Thomas Asbridge concurs, judging it “the worst natural disaster in recorded history.

The survivors who wrote about the plague leave no doubt that the Black Death was catastrophic. And as Mr. Asbridge points out, thanks to the spread of the new technology that we call paper, there was rather more contemporary writing about the Black Death than previous disasters. Consequently, we know a tantalizing amount about the plague. But the predicament we face in deciphering the Venetian statistics is hardly unique. Modern historians must try to reconstruct the nature, extent and consequences of this horrific calamity from anguished and often contradictory reports.

Mr. Asbridge’s strategy is to explore “a series of representative case studies (or what might be termed micro-histories).” He surveys the general course of the pandemic in Venice but also focuses, for example. In the example of Venice, Mr. Asbridge breezily concludes that the plague took up to two-thirds of the population, without making a compelling case for this figure among the many credible possibilities."

But 'breezily' claimed or not, author Sean Martin, 'The Black Death' (2007) correctly notes what we now refer to as 'the Black Death' was actually the second pandemic of the plague. Also up to two-thirds of the population was wiped out. How? Because there was no effort at serious isolation of the infected or any attempt to target the actual sources (rats), rather giving in to superstitious rot.

Given existing knowledge had not yet accounted for bacterial existence, blame was most often based on "supernatural" or "spiritual" attributes. I.e. blaming people who were likely not pious enough, or committed foul deeds, or were miscreants in some other fashion, e.g. "witches", atheists, heretics or ....Jews. In many regions, alas, Jewish populations were blamed for the plague's spread, part and parcel of the misbegotten German Völkisch tradition.  

Harper, the WSJ reviewer, Harper goes on:

"Anyone bold enough to attempt a new history of the Black Death today deserves our empathy. The topic is unwieldy, and fundamental mysteries abound. Did the plague hit China? How did the plague stick around for nearly half a millennium after the initial wave, causing repeated outbreaks? Why did Europe rebound from demographic catastrophe while much of the Near East stagnated?"

He basically answers these questions himself in subsequent paragraphs, acknowledging Asbridge's  insight into medieval history ( a reader in medieval history at University of London) but giving short shrift to the science. I.e. he was merely guilty of "sidelining the scientific evidence in favor of the written testimony":

"New DNA evidence transformed what we know of the plague even during the eight years that Mr. Asbridge spent researching and writing this book..

Only two decades ago, it was widely doubted by specialists that the Black Death was caused by the bacterium Yersinia pestis, the agent of the bubonic plague. Then technological advances made it possible to sequence DNA recovered from archaeological samples and determine that Y. pestis was indeed the cause. We are also learning more about the evolutionary history of this devastating bacterium, which has haunted human societies since the Stone Age."

This is a critical point and one that can't be emphasized enough.  As Harper elaborates:

The genomic evidence has been critical in pinpointing the reservoir of the plague in Central Asia and in tracing its lightning-fast diffusion along trade routes. The DNA evidence is also helping us understand how the plague stayed around for centuries. (In short, it lurked in local animal reservoirs.) As Mr. Asbridge rightly recognizes, this longevity was a crucial dimension of the bacterium’s historical impact. The Black Death was not a one-off. It was the beginning of a long age of plague."

Indeed, and as I already noted, i.e. this wave did not end in the 1300s; rather, it repeatedly recurred across Europe.  Why? Because the bacterium was endemic.

The final paragraphs of Harper are worth repeating:

"Like any pandemic, the Black Death was simultaneously a biological and a social event—shaped by both the innate characteristics of a microbe and such all-too-human factors as political systems, religious beliefs and public-health responses. "

 Which brings to mind the tens of million of blithering morons in Trump era 1.0 who clamored for "escape" and pursuit of their "freedom" even as Covid-19 deaths soared past 1 million in the U.S. 

And:

"The deepest mystery of the plague is why this bacterium—in normal times a pathogen of wild rodents—erupted to cause some of the most world-altering disease outbreaks on record. "

Author Laurie Garrett's sober take, i.e. in her book The Coming Plague (p. 169), may be the best rejoinder to this:

"An individual microbe's world is limited only by the organism's mobility and its ability to tolerate various ranges of temperature, sunlight, oxygen, acidity or alkalinity.  Wherever there may be an ideal soup for a microbe, it will eagerly take hold,  immediately joining to the local microbial ecosystem of  pushing and shoving struggle for survival.... In this fluid complexity human beings stomp about with swagger, elbowing their way without concern into one ecosphere after another. The human race seems equally complacent about blazing a path through a rainforest with bulldozers and arson  - or using an antibiotic 'scorched earth' policy to chase unwanted microbes across the duodenum."

See Also:

 Visits to Plague Towns in Germany - Some Unsettling Sights

And:

What We Learned In Germany Regarding Its 17th Century Black Death Scourge