Plagues Upon the Earth: Disease and the Course of Human History

By Kyle Harper

ISBN: 9780691192123

Kyle Harper’s Plagues Upon the Earth: Disease and the Course of Human History is longer than your average read these days, clocking in at 509 pages, not including the nearly 200 pages of appendices and indexes. But it’s not as long as you might expect, given the title and the subject matter—in fact, it might almost seem rather short. Despite the book’s length and density—both literal and figurative—Plagues Upon the Earth is a solid read for anyone looking to take a dive into the history of humanity and its diseases.

Harper assumes a rather daunting task as he sets out to document and describe the dual histories of humanity and the infectious diseases to which humans are susceptible. It is a tricky duality to balance between “microorganisms” and “macrohistory,” but Harper does an excellent job, never veering too deeply into the historical context or the microbiological sciences. He interweaves the two narratives quite seamlessly, making it evident that, as impactful as plagues have been on human history, the course of human history has in many ways dictated or influenced the nature and effectiveness of its plagues.

Plagues of the Earth begins with a brief introduction in which Harper dictates his strategy for leading the reader through the intertwined histories of humanity and its diseases. He provides critical contextual information, such as the meaning of the “paradox of progress,” which he revisits repeatedly throughout the book. He also provides a historical roadmap for the history of globalization in the context of the evolution of infectious diseases, breaking it into six separate periods: prehistoric globalization, Iron Age globalization, peak Old-World globalization, the Columbian Exchange, fossil-energy transport, and the age of jet plane travel.

Harper uses this roadmap of periods of human globalization, and subsequent microbial globalization, to break Plagues of the Earth into four parts based on the predominant change in human culture that happened in the given historical period it covers. Each part has three sizable chapters presenting information in predominantly chronological order—like any engaging historical writer, Harper injects critical context where needed without bogging down the narrative.

Part I, “Fire,” starts at the very beginning, both in terms of human history and in terms of any reader’s general understanding of human diseases. Harper answers some fundamental questions like “What is a parasite?” and ‘What is a pathogen?” Before digging too deeply into the different diseases that have plagued humanity, and some that continue to, Harper lays as firm a foundation as he can, explaining that the pathogens that negatively impact humans fall into five evolutionary groups, or taxa: viruses, bacteria, protozoa, helminths (worms), and fungi. From the start, Harper reaffirms his motivations, informing the reader that due to their limited impact on the course of human history, and by corollary the limited impact of human history on the spread of fungal diseases, fungi will largely be left by the wayside—except, as Harper notes, in their capacity to infect plants, which has had dire consequences for human agriculture (think: Irish potato famine). If you are only here for the fungi, skip to Chapter 11.

Part II, “Farms,” describes the impact of the shift from a hunter-gatherer society to a predominantly agricultural one in conjunction with its impact on increasing potential vectors for the spread of human diseases. One disease readers might recognize from more recent history, tuberculosis, also known as consumption, makes an appearance. This respiratory bacterial infection has been plaguing humans for thousands of years—and still does today, with over 10 million people contracting it annually and 1.5 million succumbing to it.

Part III, “Frontiers,” covers the periods of global expansion and colonization of the last 600 or so years. In it, Harper carefully teases apart the highly contested “virgin-soil” hypothesis, a theory popularized by Jared Diamond's Guns, Germs, and Steel. The idea of European immunological superiority triumphing over indigenous populations is, as Harper makes quite clear, critically and evidently fraught in describing the demographic disaster that defined the era of exploration.

Part IV, “Fossils,” brings us into the modern age, with the advent of fossil fuel usage spurring the Industrial Revolution and all the technological advancements that have followed. As always, the paradox of progress has been a separate plague on humanity—the idea that advancements that bring our society and culture forward ultimately weaken its defenses against pathogens that literally spread overnight. Four hundred years ago, the fastest anyone could cross land was by horse. Disease spread was limited by the speed with which its human and animal vectors could traverse great distances. Now, global jet plane networks enable the spread of pathogens from continent to continent in a matter of hours.

You might be sick and tired of reading about human-borne diseases in this time of ongoing global pandemic and I wouldn’t blame you for thinking Plagues Upon the Earth is worth passing on. Unlike most books of its kind published in the last year or so that capitalize on the renewed popular fascination with pathogens spurred by the current coronavirus pandemic, Plagues Upon the Earth doesn’t end with some trite conclusion designed to make you feel better about a world that seems to be falling apart at the seams. But given its narrative context, Plagues Upon the Earth is almost, even if just the teensiest bit, comforting. Pandemics like COVID-19 are nothing new in the greater context of human history.

Harper makes clear that, for as long as there have been humans, there have been bacterial, viral, and parasitic diseases that prey on evolutionary vulnerabilities in our species. Some of our earliest pre-human ancestors had parasitic worms (and some of us still do); the “so-called Middle Ages,” as Harper puts it, had Black Death (bubonic plague); some of our grandparents and great-grandparents and great-great grandparents had the H1N1 influenza A virus; and we have severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although every pandemic is new and terrifying in its own way, the similarities across the ages can be oddly comforting—or of course, completely disconcerting.

Jeanette S. Ferrara, MFA