Plagues Past, Paths Forward

July 29, 2019

Just about this time five years ago, I was finishing up what had been an extraordinary adventure. I had spent the year at the Institute for Advanced Study in Princeton, ostensibly to work on the impact Arabic medicine had had on 11th– and 12th-century Europe. I made good headway on that project, discovering at least a dozen new manuscripts, “cracking the code” on several key developments in intellectual history, and finally putting a human face on my key protagonist, the immigrant Tunisian monk, Constantine the African.

But at the opening reception for Visiting Members in September 2013, the Director of the IAS, Robbert Dijkgraaf, had done what directors are supposed to do: he had given us a directive. “Forget the proposal you submitted when you applied last year, and do something big, bold, and urgent.” Those probably weren’t his exact words, but they were what I remembered. So, while I continued my manuscript hunting and textual collations, I jumped headlong into an additional pursuit: figuring out how to turn a new area of genetics into a new kind of history.

The “prompt” to this work were developments in genetics research that had occurred since the beginning of the 21stcentury. That might not sound very “medieval,” but you’d be surprised! New work in genetics had shifted the ground in studies of plague, one of the most lethal diseases in the world and the cause (“alleged cause,” some doubters might have said) of the pandemic events that bookended the Middle Ages: the Justinianic Plague of the 6th to 8th centuries, and the Black Death of the 14thcentury. This was history done not by traditional historians, but by “historians in lab coats.” I had been wrestling with this question myself since around 2005, when I first heard rumors that research was being done by microbiologists who do what microbiologists do: study microbes. (“How dare they?”) It took two iterations of a National Endowment for the Humanities Summer Seminar in London to persuade me, but by 2013 I was finally convinced that maybe this “new genetics paradigm”—studying the history of infectious diseases by working from the molecular level on up—had something going for it.

My bold adventure at the IAS resulted in the inaugural issue of The Medieval Globe, produced under the visionary editorship of Carol Symes at the University of Illinois Urbana-Champaign. The volume, entitled Pandemic Disease in the Medieval World: Rethinking the Black Death, brought together historians, biologists, and anthropologists to address a simple question: “So what?” What difference, we asked, did the new findings from genetics about the mid-14th-century Black Death, or other plague pandemics, make for what we did as historians of medicine, paleopathologists, immunology researchers, or bioterrorism experts? As noted in the review of the volume by historian Lester Little, the enterprise was intended from the outset to be provisional. We knew that new work from the sciences about the evolutionary history of the single-celled bacterium, Yersinia pestis, was coming so fast and thick that keeping up with it was a vertigo-inducing endeavor. With funding from the World History Center at the University of Pittsburgh, we were able to publish open-access, making the volume readily discoverable and facilitating interdisciplinary awareness of our work. 13,500+ downloads later, it has been a stunning success—its own quick obsolescence being the best measure of that.In the past five years, the field of plague studies has transformed several times over. In 2015, researchers discovered Bronze Age plague strains, and in subsequent years have pushed that new chronological horizon back into the Late Neolithic. Studies documenting the existence of what seems to be a unique European lineage of Y. pestis, seeded by the Black Death strain, offer strong support for our initial idea in 2014 that, as Ann Carmichael hypothesized, plague may indeed have focalized within western Europe itself. And while we knew already in 2014 that a Y. pestis genome from the First Plague Pandemic in the sixth century had been successfully sequenced, it has still been flabbergasting, in 2018 and 2019, to see genetic evidence of how early that lineage must have emerged out of the Tian Shan Mountains in Kyrgyzstan and how much the Justinianic Plague strain diverged within Europe.

The work in genetics thus continues to dazzle. But traditional bioarchaeologists and historians have been no sluggards these past years (even if we remain much more poorly funded). Indeed, we’ve been keeping the geneticists on their toes. Medieval Globe contributor Sharon DeWitte has continued her prolific and pioneering studies, looking for factors that might have created differentials in survival or subsequent health of populations in northern Europe. Some of that work has been in alliance with Fabian Crespo, who has continued to investigate the immune competence of historical populations. The work of Anna Colet and her colleagues on the tragic persecution of the Jewish community in Tàrrega has become the focal point for new work by Susan Einbinder exploring the post-Black Death commemorations of Jews for the afflictions they had suffered.

Stuart Borsch has carried forward his efforts to document and quantify the demographic effects of the plague in the Islamic world, while Michelle Ziegler has pushed forward her interests in disease landscapes. Robert Hymes’ work on the possible presence of plague in Mongol China has begun to win converts, with a new book by Timothy Brook set to feature plague as a key factor in the fall of the Yuan (Mongol) dynasty and the rise of the Ming. My work with Kathleen Walker-Meikle and Wolfgang Müller on the “misdiagnosed” leprosy image was taken up and furthered by Lori Jones and Richard Nevell, who not simply turned the mighty juggernaut of Wikipedia around, getting the leprosy image removed from the plague/Black Death pages in multiple languages (which get millions of views every year), but also persuaded numerous Internet outlets and publications to rethink their uses of other “misdiagnosed” images.

Fig. 1: Since 2014 when we first published our study about this image of leprosy in James le Palmer’s Omne bonum, the British Library has scanned the entire two volumes of Royal MS 6 E VI, thus allowing anyone in the world to examine for themselves the chapter “On Ministrations by a Disabled Cleric.”

And as if all those transformations weren’t enough, there has been the stellar success of Nükhet Varlık’s work, which she previewed in her 2014 essay, “New Science and Old Sources: Why the Ottoman Experience of Plague Matters.” Her 2015 book, Plague and Empire in the Early Modern Mediterranean World: The Ottoman Experience, 1347–1600, has earned an astounding four book awards, all from different academic societies, most recently the American Association for the History of Medicine. If ever there was proof of the broad historical significance of the intersections of disease and history, or the value in using the most rigorous methods to explore them, it is this pioneering study.

The most daring offshoot of the Pandemic Disease volume came out in December 2018: a special issue of the online journal Afriques on the theme, “The Black Death and Its Aftermaths in Sub-Saharan Africa: A Critical Exploration of Silence.” “Silence” was the operative word, since aside from a few passing references, the possibility that plague had penetrated Africa below the Sahara has not been a part of Black Death narratives. The work of archaeologists in Europe, where the presence of plague was now confirmed by aDNA, offered a new model of what might be considered a “plague imprint” in the physical, built environment: signs of contracted, or even abandoned, human settlements. Gérard Chouin, on the one hand, and Daphne Gallagher and Stephen Dueppen, on the other, took paradigm-shifting work, such as that by archaeologist Carenza Lewis, as a charge to look for absences in the West African late medieval landscape: things that are not there, signs that, in negation, mark an unnamed catastrophe. Marie-Laure Derat, another contributor to the Afriques volume, looked to the eastern part of Africa and found surprisingly rich documentation in Ethiopian written sources of the effects of plague there, right down to the importation of European plague saints by the local Christian communities.

And where was the “net” of genetics to support this great leap of faith in carrying plague’s story into Africa? What promise did palaeogenetics hold for other parts of the world if no plague aDNA had yet been retrieved outside of Europe and western Russia? As Lori Jones and I muse in a forthcoming paper on infectious disease history in the Indian Ocean World, local aDNA is not necessary to start seeing the larger, global implications of an evolutionary approach to infectious disease history. In my chapter of the 2014 Medieval Globe volume, I had laid out why the new evolutionary understanding of Yersinia pestis was pointing a finger at East Africa and saying “There’s something going on here!” In my essay for the Afriques volume, I revisited that genetics evidence. Just as a philologist infers textual transmission from a stemma, so an evolutionary geneticist can infer lines of biological inheritance from a phylogenetic tree. (In concept, the two kinds of diagrams are identical.) Using my 2016 observations about a split in the branching of Y. pestis’s evolutionary tree right after the Black Death, along with evidence from colonial records and oral traditions, I sketched out how a Russian strain of plague may have reached East Africa in the late medieval period. It survives there to the present day.

Figure 2: Detail of the Yersinia pestis phylogenetic tree marked to show the later medieval polytomy (the “Big Bang,” circled in red) and the new branches it created, both those retrieved from aDNA (black labels) and those from modern isolates (peach-colored labels). The African branch is “1.ANT.” From: Monica H. Green, “Putting Africa on the Black Death Map: Narratives from Genetics and History,” Afriques 9 (2018),

My ultimate goal in diving headlong into plague research had always been pedagogical. The blogpost I wrote for Arc Humanities in 2015 focused on my teaching, and I’m proud to say that my 2018 essay, “On Learning How to Teach the Black Death,” has been the second most frequently viewed and downloaded item on my public webpage.

So yes, this project was “big.” And “bold” (or boldly ambitious), too. But was it “urgent”? Five years ago this month, I left Princeton and was driving home to Arizona. When I had radio reception, I was listening to news coming out of West Africa. The still-uncontained outbreak of Ebola was taking dozens of lives every week. The barely contained panic in the reports was palpable. When I returned home, I knew that my task—the one way I could help as a historian—was to “teach the crisis.” With a new colleague-in-arms, Stephen Casper, I started an Ebola Archive: the crisis could best be understood, we thought, by getting a sense of where the disease came from, where it might be heading, and how those most immediately affected (not simply healthcare providers but the local populace) might have understood what they were experiencing. In other words, we attempted to bring all the perspectives that I and my colleagues had just used to approach the Black Death. In January 2015, I wrote up a new foreword to the print edition to Pandemic Disease: “The Black Death and Ebola: On the Value of Comparison.” It breaks my heart to re-read it now, with a new Ebola epidemic still out-of-control in the Democratic Republic of Congo.

What does the medieval past have to teach the present? Sometimes, looking for “medievalness” is the wrong thing to do. Madagascar’s outbreak of plague in 2017 had nothing to do with the Middle Ages, but everything to do with the modern processes of globalized trade and labor. But we only know when and how to make such comparisons by having a deeply immersed understanding of both past and present. The “new plague paradigm” has proved a powerful tool, not simply for geneticists (for whom Y. pestis has now become a “model organism”), but for historians and archaeologists, too. If I could give a directive to other medievalists, it would likewise be to “do something big, bold, and urgent.”

by Monica H. Green