A germ of an idea

Thirty-four years ago, William H. McNeill, AB’38, AM’39, shed new light on world history—by giving microbes their proper place in the human drama.

By Robert Goodier
Photography by Julie Brown

In the 1960s, historian William H. McNeill, U-High'34, AB'38, AM'39, noticed something missing from other scholars' theories about the history of civilization: disease. Documenting battles in detail, historians conscientiously scoured archives for accurate body counts and troop movements, but they largely ignored some of the most colossal slaughters ever recorded. In 165 AD Roman soldiers returning home from war in Mesopotamia brought with them a microbe—smallpox is the best guess. Rome had suffered disease outbreaks before, but the Antonine Plague of 165-180 AD killed more people than any other; a quarter to a third of Rome's population died, including two emperors: Lucius Verus and Marcus Aurelius Antoninus, who gave the pandemic its name. The Antonine Plague, says McNeill, the Robert A. Millikan distinguished service professor emeritus in history, coincided with the start of the Roman Empire's 300-year decline.

Author and biologist Laurie Garrett says that before McNeill’s Plagues and Peoples, diseases and outbreaks were viewed as “trivial episodes, never having the impact of a war or a coup d’etat.”

The year 251 AD brought another pandemic to Rome, the Plague of Cyprian, which imposed a similar death toll. Ultimately, "about half the population died," McNeill says. "That has an enormous effect on society." And yet, among the myriad theories about what caused the fall of Rome—political corruption, deteriorating morals, constant wars, economic chaos, the tremendous burden of a rapidly expanding empire—historians had said little about disease. The way McNeill sees it, Rome's pandemics left it with a population too small to support its large military and state apparatus, a predicament that led to further civic and economic unraveling. Collapse was inevitable.

Today, it seems difficult to overstate McNeill's case. Looking back across history, it's clear that catastrophic disease has played a role in shaping human affairs. In the 1960s, however, epidemiology was a discipline sequestered among physicians and statisticians. It had not yet found its way to history departments.

In 1976 McNeill forged that path with a sweeping book that took a new approach to disease history. Plagues and Peoples (Anchor Press/Doubleday) focused a biological lens on the ebb and flow of human civilization, from prehistory into the 20th century, and the picture that emerged showed a pattern of what he calls "fateful encounters" between infectious disease and world events: China's ancient Han Dynasty, like the Roman Empire, was brought down in part by epidemic illness, McNeill argues, and during the 14th century the Black Death proved a similarly "shattering experience" for the Mongol Empire. Only by taking disease into account can one explain Athens's failure to defeat Sparta during the Peloponnesian War, a conflict that transformed the ancient Greek world. Greek historian Thucydides described a sudden, devastating plague that struck in 431 BC, wiping out a quarter of Athens's land army and inflicting "a blow on Athenian society," McNeill writes, "from which it never entirely recovered." The historian also brought disease to bear on such diverse phenomena as the rise of Christianity and Buddhism, the caste system in India, and the expansion of the British Empire.

With Plagues and Peoples, McNeill deflated society's confidence, surging in the 1970s, that humans had taken control over infectious disease, and he was alone among his peers in predicting that people had not seen the last of world-altering epidemics. The book amended conventional histories of heroes, states, armies, and artists, giving microbes their place as an important influence in human history. "Before William McNeill wrote Plagues and Peoples, there was the general belief that diseases and outbreaks had never played significant roles," says author and biologist Laurie Garrett, who won a Pulitzer Prize in 1996 with a Newsday series on Zaire's Ebola outbreak. "It was commonly believed these were trivial episodes, never having the impact of a war or a coup d'etat." Plagues and Peoples, she adds, "was such a remarkable contribution, and nobody had pulled it together in a coherent form before."

This past February, President Barack Obama awarded McNeill a 2009 National Humanities Medal. It was the latest honor in a distinguished career. Plagues and Peoples is not his most acclaimed work—he won the National Book Award in 1964 for his world history, The Rise of the West, and he wrote more than 20 other volumes. But 34 years after its publication, Plagues and Peoples still resonates profoundly in a world where the threat of epidemic disease remains ever-present: AIDS, avian flu, H1N1, SARS, drug-resistant tuberculosis.

McNeill's interest in history goes back to childhood. His father was theologian and historian John T. McNeill, PhD'20, and as a ten-year-old, McNeill was already theorizing about history's shapes and patterns. A summer College course with anthropologist Robert Redfield, AB'20, JD'21, PhD'28, taught him to see nations and cultures as interconnected. In 1939, having earned a master's from the Committee on the History of Culture, he headed east to a doctoral program at Cornell. On a visit to the university library there, he chanced upon three volumes of Toynbee's A Study of History and was spellbound. It was a momentous discovery. "History as previously taught to me shrank into no more than a small part of the human past," McNeill told George Mason University's History News Network in 2008, "and the big book I had set my heart on when still an undergraduate suddenly needed to expand and become a real world history."

World War II interrupted McNeill's studies. In 1941 he was drafted into the army, serving first in Hawaii and the Caribbean. In 1944 he was dispatched briefly to Cairo and then to Greece as an assistant military attaché. In Athens that November, he saw the Germans retreat, and afterward he watched the country descend into civil war. It was also there that McNeill met his wife, Elizabeth Darbishire, who was in charge of the Office of War Information's Athens library. They were married in 1946.

After the Army, McNeill returned to academia, receiving his PhD at Cornell in 1947 and then making his way back to Chicago, where he joined the history faculty. He remained in Hyde Park, teaching and writing, until 1987, when he and his wife retired to Connecticut.

Since 2006, when Darbishire died, McNeill has lived alone on a piece of land jutting into the woods in the hills skirting Colebrook, Connecticut. His four children and their families gather there for two weeks every year, and the walls are covered with his grandchildren's crayon drawings. At 92 he continues to write, and in 2005 he published a memoir, The Pursuit of Truth.


Back in 1976, many thought the eradication of infection was imminent. Penicillin had been discovered half a century earlier, the first polio vaccine had been created in 1952, and the World Health Organization was on the verge of eliminating smallpox from the planet. Still simmering anonymously, the HIV/AIDS crisis would not be identified until 1981. "It was part of the hubris of the late 20th century to say that we'd taken care of infectious diseases, that they were no longer a problem," says Donald Hopkins, MD'66, health-programs director at the Carter Center in Atlanta. "Authoritative, respected, really, really knowledgeable people were saying things like that. That we've got them under control. Now we need to focus on other problems."

Hopkins remembers Plagues and Peoples as only the third book he'd read that pointed to microbes as actors in human history; it was the first to do so on a global scale, and the first to be written by a historian. "The idea of having somebody write about this who's prominent and formally trained in history is very unusual and very important," Hopkins says. "The concept is certainly important, that diseases do affect history and have done so for as long as people have been writing history."

McNeill first noticed disease lurking in the shadows of historical documents when he was researching The Rise of the West. Like accounts of the Antonine Plague, historical records made passing mention of disease. But there was little analysis of their role in shaping history. "I read the story of Cortéz and couldn't believe it," McNeill says. The conventional story of how Tenochtitlan [modern-day Mexico City] fell to Hernán Cortéz and a small band of Spaniards in 1521 seemed to contradict common sense. At one point, the Aztecs had beaten the Spaniards back but did not press their advantage. "A considerable number of the Spanish were wounded in the retreat but there was no follow-up," McNeill says. "I couldn't figure out why the nephew of Montezuma, who organized the attack, didn't surround the Spaniards and bring them up to the top of that temple and cut their hearts out the next day. It's what should have happened."

And yet, it didn't. Instead, the Spaniards conquered Mexico and converted millions of Aztecs to Christianity. "I was sort of mulling this over in my head," McNeill recalls, "and somebody casually remarked that smallpox had broken out in Mexico City the night of the noche triste"—the night of the Spaniards' retreat—"and Montezuma's nephew died of it that same night."

The plague struck only the Aztecs. The Spaniards, who had developed an immunity to smallpox during repeated childhood exposures, were spared. The implication in the eyes of everyone who lived through the Aztec epidemic, McNeill argues, was the superior power of the Spaniards' God over the Aztecs' deities. "The whole history of the New World hinged on that episode," McNeill says. Suddenly he realized "there was a whole history that had to be written.

Researching the 1521 fall of Tenochtitlan, McNeill wondered why the Aztec army failed to press its advantage against the vastly outnumbered Spaniards. “It’s what should have happened.” But the Aztecs, he discovered, were weakened by smallpox.

But in writing Plagues and Peoples, McNeill encountered a documentation problem. The scarcity of records threatened to derail the project. Where authoritative evidence was unavailable, he stitched together references to disease in documents such as the Old Testament or the Epic of Gilgamesh, cross-referenced with, say, a paper detailing smallpox-like marks on the mummified skin of an Egyptian ruler or mentions of epidemics in Chinese dynastic histories. A medical historian at Oxford University Press rejected the manuscript, calling it too speculative. McNeill agreed, but he had made a decision early in his career to embrace speculation. Shying from it, he says, "is a terrible mistake for a historian to make, because sometimes things that are important are not written down. And sometimes the things that are written down are not true."

Anchor Press, a division of Random House, later published Plagues and Peoples, and reviewers received it enthusiastically, but noted its fragmentary citations. "A hypothesis rather than a demonstration," declared a reviewer in the Journal of the American Medical Association, who went on to say: "Although only the future can tell how much of Professor McNeill's insight is true, we meanwhile have a stimulating account."

Before the book went to press, McNeill circulated the manuscript among two dozen specialists to vet his hypothesis and the science. One was Warwick Coppelson, a Chicago surgical pediatrician who echoes a warning from the book. "We just had the 200th anniversary of the birth of Darwin," he says, "and his theory will, in one way or another, defeat, in the short term, whatever we do." He was referring to microbes' rapid evolution and their ability to adapt to whatever circumstances modern medicine throws at them. When the next pestilence comes, it will probably be unlike anything we have seen before, Coppelson says. "The first single-celled organisms had viruses. Those viruses had millions of years to learn the tricks of the trade. And given that amount of time they have learned their trades well." McNeill agrees. "We don't know the future, but we know that it has happened in the past," he said. "History is the history of disease."

Although his contemporaries may not have understood microbes' power to change world events, McNeill sees something more to their omission: the pursuit of meaning. Like everyone, historians crave meaning, he says, searching the past for narratives that bring order to otherwise random events. For most of human history, disease was not such a narrative. Until the invention of the microscope, illness was an act of God or fate. Even when scientists finally saw microbes crawling under the lens, it was difficult to accept their importance. "We do make history to be meaningful," McNeill says. "And something that isn't meaningful, we have a great capacity not to notice, or not to put into our books. There's no other possible explanation."

McNeill's work is not an exception—he simply managed to lend historical meaning to the narrative of disease. "It's a hallmark of his work to try to understand history as a set of outcomes that no one intended, but to which many contributed," says his son John R. McNeill, U-High'71, an environmental historian and Georgetown University professor. In 2003 he and his father coauthored The Human Web: A Bird's-Eye View of World History, a book that explores the interconnectedness of human history and the "webs of interaction," both cooperative and competitive, that help disseminate goods, people, ideas-and diseases. "There is, has been, and still is, within the historical profession," John McNeill says, "a rather naive sense of cause and effect, of actor and outcome." His father, "tried to explain how much more complicated and chaotic human affairs has been and remains." That idea weaves through William McNeill's military history, The Pursuit of Power, his son says, including the "extraordinary development of the destructive power of weaponry. Nobody in the 18th century was hoping that humankind would develop the power to destroy itself several times other."


McNeill's life has been marked by the great world events of his generation, war and disease among them. He was one year old in 1918, at the height of the flu epidemic that killed 50 to 100 million people worldwide, when his entire family contracted the disease. His mother was seven months pregnant. "My sister was born two months prematurely in a time when there was not a single hospital bed available," he says. "It's very possible the baby was born on the kitchen table with no help whatever. She wasn't expected to survive, but she did."

McNeill is known for taking on big ideas. His son believes his World War II experience—"he earned his PhD in difficult times"—may have influenced his research methods. "My father has never done archival research, which is very unusual," John McNeill said. For his first book, The Greek Dilemma: War and Aftermath, published in 1947, McNeill relied on his own overseas experiences and the oral histories he collected while he was there. A book review in the Annals of the American Academy of Political and Social Science called McNeill "at his best" when tracing the rise of communist influence in Greece: "Here we have material that can hardly be secured elsewhere." Instead of narrowing his focus, as archival historians often do, McNeill became a global-scale historian.

That large view also marked his 1961-69 tenure as chair of Chicago's history department. "He was probably the single most important historian at Chicago since 1965," says one of his former students, Dean of the College John Boyer, AM'69, PhD'75. McNeill made the history department into one of the top five in the country, and Boyer remembers him as "bold and capacious in his willingness to teach courses across time and space." A "collegial" leader, McNeill "cared a great deal about his students." As department chair, he changed the character of the faculty, appointing instructors who specialized in regions other than America and Europe.

As a professor, McNeill sought original ideas from his students and gave them latitude to explore. "He has a very strong conviction that history, if it's to prosper, it's got to be something other than just one scholar talking to another about subjects that nobody else cares about," Boyer says. "He believes in the power of history to improve mankind and that it has to be accessible."

Since Plagues and Peoples, there has been a sea change in historical analysis. Journalists, historians, anthropologists, and others have detailed the effect of plagues and outbreaks in hundreds of books. In 1997, UCLA geographer and physiologist Jared Diamond published Guns, Germs and Steel: the Fates of Human Societies, a best-seller demonstrating the influence of microbes on human history. Laurie Garrett's voluminous bibliography includes numerous books on disease-evolution and epidemics, among them 1995's The Coming Plague: Newly Emerging Diseases in a World Out of Balance. Journalist Charles Mann, meanwhile, wrote 1491: New Revelations of the Americas Before Columbus, a startling history of the pre-Columbian Americas crowded with people before European diseases arrived. Accounts of recent brushes with plague also abound: journalist Richard Preston published The Hot Zone (1994), a harrowing chronicle of the 1989 Ebola outbreak in Reston, Virginia; and Demon in the Freezer (2002), about the eradication of smallpox and the last strains that are still kept in storage. The list is long, and Plagues and Peoples is at the head of it.


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