The Ghost Map: The Story of London's Most Terrifying Epidemic--and How It Changed Science, Cities, and the Modern World

by Steven Johnson

We’re naturally inclined to consider these scavengers tragic figures, and to fulminate against a system that allowed so many thousands to eke out a living by foraging through human waste. In many ways, this is the correct response. (It was, to be sure, the response of the great crusaders of the age, among them Dickens and Mayhew.) But such social outrage should be accompanied by a measure of wonder and respect: without any central planner coordinating their actions, without any education at all, this itinerant underclass managed to conjure up an entire system for processing and sorting the waste generated by two million people.

Because we’re aerobic creatures ourselves, we tend not to think of oxygen as a waste product, but from the point of view of the algae, that’s precisely what it is: a useless substance discharged as part of its metabolic cycle.

Most of that recycling work, in both remote tropical rain forests and urban centers, takes place at the microbial level. Without the bacteria-driven processes of decomposition, the earth would have been overrun by offal and carcasses eons ago, and the life-sustaining envelope of the earth’s atmosphere would be closer to the uninhabitable, acidic surface of Venus. If some rogue virus wiped out every single mammal on the planet, life on earth would proceed, largely unaffected by the loss. But if the bacteria disappeared overnight, all life on the planet would be extinguished within a matter of years.

The social theorist Walter Benjamin reworked Dickens’ original slogan in his enigmatic masterpiece “Theses on the Philosophy of History,” written as the scourge of fascism was enveloping Europe: “There is no document of civilization that is not also a document of barbarism.” The opposition between civilization and barbarism was practically as old as the walled city itself. (As soon as there were gates, there were barbarians ready to storm them.) But Engels and Dickens suggested a new twist: that the advance of civilization produced barbarity as an unavoidable waste product, as essential to its metabolism as the gleaming spires and cultivated thought of polite society. The barbarians weren’t storming the gates. They were being bred from within. Marx took that insight, wrapped it in Hegel’s dialectics, and transformed the twentieth century. But the idea itself sprang out of a certain kind of lived experience—on the ground, as the activists still like to say. It came, in part, from seeing human beings buried in conditions that defiled both the dead and the living.

No one died of stench in Victorian London. But tens of thousands died because the fear of stench blinded them to the true perils of the city, and drove them to implement a series of wrongheaded reforms that only made the crisis worse. Dickens and Engels were not alone; practically the entire medical and political establishment fell into the same deadly error: everyone from Florence Nightingale to the pioneering reformer Edwin Chadwick to the editors of The Lancet to Queen Victoria herself.

The history of knowledge conventionally focuses on breakthrough ideas and conceptual leaps. But the blind spots on the map, the dark continents of error and prejudice, carry their own mystery as well. How could so many intelligent people be so grievously wrong for such an extended period of time? How could they ignore so much overwhelming evidence that contradicted their most basic theories? These questions, too, deserve their own discipline—the sociology of error.

But not all the locals had succumbed to abject fear. As he made his rounds, Whitehead found himself musing on an old saying that invariably surfaced during plague times: “Whilst pestilence slays its thousands, fear slays its tens of thousands.” But if cowardice somehow made one more vulnerable to the ravages of the disease, Whitehead had seen no evidence of it. “The brave and the timid [were] indiscriminately dying and indiscriminately surviving,” he would later write. For every terrified soul who fell victim to the cholera, there was another equally frightened survivor.

Fear might not have been a contributing factor in the spread of disease, but it had long been a defining emotion of urban life. Cities often began as an attempt to ward off outside threats—fortified by walls, protected by guards—but as they grew in size, they developed their own, internal dangers: disease, crime, fire, along with the “soft” dangers of moral decline, as many believed.

Death was omnipresent, particularly for the...

Brewed tea possesses several crucial antibacterial properties that help ward off waterborne diseases: the tannic acid released in the steeping process kills off those bacteria that haven’t already perished during the boiling of the water. The explosion of tea drinking in the late 1700s was, from the bacteria’s point of view, a microbial holocaust. Physicians observed a dramatic drop in dysentery and child mortality during the period. (The antiseptic agents in tea could be passed on to infants through breast milk.) Largely freed from waterborne disease agents, the tea-drinking population began to swell in number, ultimately supplying a larger labor pool to the emerging factory towns, and to the great sprawling monster of London itself.

THE SEARCH FOR UNPOLLUTED DRINKING WATER IS AS OLD as civilization itself. As soon as there were mass human settlements, waterborne diseases like dysentery became a crucial population bottleneck. For much of human history, the solution to this chronic public-health issue was not purifying the water supply. The solution was to drink alcohol. In a community lacking pure-water supplies, the closest thing to “pure” fluid was alcohol. Whatever health risks were posed by beer (and later wine) in the early days of agrarian settlements were more than offset by alcohol’s antibacterial properties. Dying of cirrhosis of the liver in your forties was better than dying of dysentery in your twenties.

Many genetically minded historians believe that the confluence of urban living and the discovery of alcohol created a massive selection pressure on the genes of all humans who abandoned the hunter-gatherer lifestyle. Alcohol, after all, is a deadly poison and notoriously addictive. To digest large quantities of it, you need to be able to boost production of enzymes called alcohol dehydrogenases, a trait regulated by a set of genes on chromosome four in human DNA. Many early agrarians lacked that trait, and thus were genetically incapable of “holding their liquor.” Consequently, many of them died childless at an early age, either from alcohol abuse or from waterborne diseases. Over generations, the gene pool of the first farmers became increasingly dominated by individuals who could drink beer on a regular basis. Most of the world’s population today is made up of descendants of those early beer drinkers, and we have largely inherited their genetic tolerance for alcohol. (The same is true of lactose tolerance, which went from a rare genetic trait to the mainstream among the descendants of the herders, thanks to the domestication of livestock.) The descendants of hunter-gatherers—like many Native Americans or Australian Aborigines—were never forced through this genetic bottleneck, and so today they show disproportionate rates of alcoholism. The chronic drinking problem in Native American populations has been blamed on everything from the weak “Indian constitution” to the humi...

Ironically, the antibacterial properties of beer—and all fermented spirits—originate in the labor of other microbes, thanks to the ancient metabolic strategy of fermentation. Fermenting organisms, like the unicellular yeast fungus used in brewing beer, survive by converting sugars and carbohydrates into ATP, the energy currency of all life. But the process is not entirely clean. In breaking down the molecules, the yeast cells discharge two waste products—carbon dioxide and ethanol. One provides the fizz, the other the buzz. And so in battling the health crisis posed by faulty waste-recycling in human settlements, the proto-farmers unknowingly stumbled across the strategy of consuming the microscopic waste products generated by the fermenters. They drank the waste discharged by yeasts so that they could drink their own waste without dying in mass numbers. They weren’t aware of it, of course, but in effect they had domesticated one microbial life-form in order to counter the threat posed by...

IT IS NEARLY IMPOSSIBLE TO OVERSTATE THE IMPACT THAT Edwin Chadwick’s life had on the modern conception of government’s proper role. From 1832, when he was first appointed to the Poor Law Commission, through his landmark 1842 study of sanitation among the laboring classes, through his tenure as commissioner of the sewers in the late 1840s, to his final run at the helm of the General Board of Health, Chadwick helped solidify, if not outright invent, an ensemble of categories that we now take for granted: that the state should directly engage in protecting the health and well-being of its citizens, particularly the poorest among them; that a centralized bureaucracy of experts can solve societal problems that free markets either exacerbate or ignore; that public-health issues often require massive state investment in infrastructure or prevention. For better or worse, Chadwick’s career can be seen as the very point of origin for the whole concept of “big government” as we know it today.

This is the great irony of Chadwick’s life: in the process of inventing the whole idea of a social safety net, he unwittingly sent thousands of Londoners to an early grave. How could such noble aspirations lead to such devastating results? In Chadwick’s case, there is a simple explanation: he insisted, to the point of obstinacy, on following his nose. The air of London was killing Londoners, he claimed, and thus the route to public health had to begin with removing noxious smells. He expressed this notion most famously—and most comically—in his 1846 testimony to a parliamentary committee investigating the problem of London’s sewage: “All smell is, if it be intense, immediate acute disease; and eventually we may say that, by depressing the system and rendering it susceptible to the action of other causes, all smell is disease.”

Herein lies the dominant irony of the state of British public health in the late 1840s. Just as Snow was concocting his theory of cholera as a waterborne agent that had to be ingested to do harm, Chadwick was building an elaborate scheme that would deliver the cholera bacteria directly to the mouths of Londoners. (A modern bioterrorist couldn’t have come up with a more ingenious and far-reaching scheme.) Sure enough, the cholera returned with a vengeance in 1848–1849, the rising death toll neatly following the Sewer Commission’s cheerful data on the growing supply of waste deposited in the river. By the end of the outbreak, nearly 15,000 Londoners would be dead. The first defining act of a modern, centralized public-health authority was to poison an entire urban population.

Why would the authorities go to such lengths to destroy the Thames? All the members of these various commissions were fully aware that the waste being flushed into the river was having disastrous effects on the quality of the water. And they were equally aware that a significant percentage of the population was drinking that water. Even without a waterborne theory of cholera’s origin, it seems like madness to celebrate the ever-increasing tonnage of human excrement being flushed into the water supply. And, indeed, it was a kind of madness, the madness that comes from being under the spell of a Theory. If all smell was disease, if London’s health crisis was entirely attributable to contaminated air, then any effort to rid the houses and streets of miasmatic vapors was worth the cost, even if it meant turning the Thames into a river of sewage.

Why was the miasma theory so persuasive? Why did so many brilliant minds cling to it, despite the mounting evidence that suggested it was false? This kind of question leads one to a kind of mirror-image version of intellectual history: not the history of breakthroughs and eureka moments, but instead the history of canards and false leads, the history of being wrong. Whenever smart people cling to an outlandishly incorrect idea despite substantial evidence to the contrary, something interesting is at work. In the case of miasma, that something involves a convergence of multiple forces, all coming together to prop up a theory that should have died out decades before. Some of those forces were ideological in nature, matters of social prejudice and convention. Some revolved around conceptual limitations, failures of imagination and analysis. Some involve the basic wiring of the human brain itself. Each on its own might not have been strong enough to persuade an entire public-health system to empty raw sewage into the Thames. But together they created a kind of perfect storm of error.

MIASMA CERTAINLY HAD THE FORCE OF TRADITION ON ITS side. The word itself is a derivation from the Greek term for pollution; the notion of disease being transmitted by poisoned air dates back to Greek medicine of the third century B.C. Hippocrates was so obsessed with air-quality issues that his medical tracts sometimes sound like instructions for a novice meteorologist. His treatise On Air, Water, and Places begins: “Whoever wishes to investigate medicine properly, should proceed thus: in the first place to consider the seasons of the year, and what effects each of them produces for they are not at all alike, but differ much from themselves in regard to their changes. Then the winds, the hot and the cold, especially such as are common to all countries, and then such as are peculiar to each locality.” (Farr would echo this philosophy centuries later: his Weekly Returns would invariably include a brief weather report, before getting to the body count.) Just about every epidemic disease on record has been, at one point or another, attributed to poisoned miasma. The word “malaria” itself derives from the Italian mal aria, or “bad air.”

Bacteria recycling energy stored in fecal matter releases hydrogen sulfide into the air. Disgust at the scent of any of these compounds is as close to a universal human trait as we know. You can think of it as a form of evolutionary pattern recognition: over millions of years of evolution, natural selection hit upon the insight that the presence of hydrogen sulfide molecules in the air was a reasonably good predictor that microbial life-forms that could be dangerous if swallowed were nearby. And so the brain evolved a system for setting off an alarm whenever those molecules were detected. Nausea itself was a survival mechanism: it was better to void the contents of your stomach than run the risk that the smell was coming from the antelope you’d just finished eating.

But those telltale molecules—hydrogen sulfide, cadaverine—were clues pointing to a threat. They were not the threat itself. If you press your nose up against a decomposing banana or antelope, you might well make yourself vomit, but you won’t contract a disease from the experience, however repulsive. Breathing in pure methane gas or hydrogen sulfide could kill you, of course, but bacterial decomposition doesn’t release anywhere near enough of these gases to saturate the environment. In other words, methane and putrescine and cadaverine are the smoke. Microbes are the fire.

The miasmatists had plenty of science and statistics and anecdotal evidence to demonstrate that the smells of London weren’t killing people. But their gut instincts—or, more like it, their amygdalas—kept telling them otherwise. All of John Snow’s detailed, rigorous analysis of the water companies and the transmission routes of the Horsleydown outbreak couldn’t compete with a single whiff of the air in Bermondsey. The miasmatists were unable to override the alarm system that had evolved so many aeons before. They mistook the smoke for the fire.

To build a case for waterborne cholera, the mind had to travel across scales of human experience, from the impossibly small—the invisible kingdom of microbes—to the anatomy of the digestive tract, to the routine daily patterns of drinking wells or paying the water-company bills, all the way up to the grand cycles of life and death recorded in the Weekly Returns. If you looked at cholera on any one of those levels, it retreated back into the haze of mystery, where it could be readily rolled back to the miasma theory, given the pedigree and influence of miasma’s supporters. Miasma was so much less complicated. You didn’t need to build a consilient chain of argument to make the case for miasma. You just needed to point to the air and say: Do you smell that?

This is how great intellectual breakthroughs usually happen in practice. It is rarely the isolated genius having a eureka moment alone in the lab. Nor is it merely a question of building on precedent, of standing on the shoulders of giants, in Newton’s famous phrase. Great breakthroughs are closer to what happens in a flood plain: a dozen separate tributaries converge, and the rising waters lift the genius high enough that he or she can see around the conceptual obstructions of the age.