How Mosquitoes Changed Everything

They slaughtered our ancestors and derailed our history. And they’re not finished with us yet.
The insects are estimated to have killed more people than any other single cause.Illustration by Ariel Davis

In 1698, five ships set sail from Scotland, carrying a cargo of fine trade goods, including wigs, woollen socks and blankets, mother-of-pearl combs, Bibles, and twenty-five thousand pairs of leather shoes. There was even a printing press, with which the twelve hundred colonists aboard planned to manage a future busy with contracts and treaties. To make space for the luxuries, the usual rations for food and farming were reduced by half. But farming wasn’t the point. The ships’ destination was the Darien region of Panama, where the Company of Scotland hoped to create a trading hub that would bridge the isthmus and unite the world’s great oceans, while raising the economic prospects of a stubbornly independent kingdom that had just struggled through years of famine. The scheme was wildly popular in the desperate country, attracting a wide range of investors, from members of the national Parliament down to poor farmers; it has been estimated that between one-quarter and one-half of all the money in circulation in Scotland at the time followed the trade winds to Panama.

The expedition met with ruin. Colonists, sickened by yellow fever and strains of malaria for which their bodies were not prepared, began to die at the rate of a dozen a day. “The words that are repeated to the point of nausea in the diaries, letters, and accounts of the Scottish settlers are mosquitoes, fever, ague, and death,” the historian Timothy C. Winegard writes in his sprawling new book, “The Mosquito: A Human History of Our Deadliest Predator” (Dutton). After six months, with nearly half their number gone, the survivors—except those too weak to move, who were left behind on the shore—returned to their ships and fled north. Still, they kept dying in droves, their bodies thrown overboard. When a relief mission arrived in Darien, they found, of all the wigs and combs and shoes and ambition that had left Scotland, only a deserted printing press on an empty beach.

But, Winegard writes, the expedition did have some lasting results: the overwhelming debt from the failure drove the reluctant Scottish to at last accept a unification offer from England. The mosquitoes of Darien led, by an unexpected route, to the birth of Great Britain.

Winegard’s book offers a catalogue of such stories. It turns out that, if you’re looking for them, the words “mosquitoes,” “fever,” “ague,” and “death” are repeated to the point of nausea throughout human history. (And before: Winegard suggests that, when the asteroid hit, dinosaurs were already in decline from mosquito-borne diseases.) Malaria laid waste to prehistoric Africa to such a degree that people evolved sickle-shaped red blood cells to survive it. The disease killed the ancient Greeks and Romans—as well as the peoples who tried to conquer them—by the hundreds of thousands, playing a major role in the outcomes of their wars. Hippocrates associated malaria’s late-summer surge with the Dog Star, calling the sickly time the “dog days of summer.” In 94 B.C., the Chinese historian Sima Qian wrote, “In the area south of the Yangtze the land is low and the climate humid; adult males die young.” In the third century, malaria epidemics helped drive people to a small, much persecuted faith that emphasized healing and care of the sick, propelling Christianity into a world-altering religion.

Winegard finds first-person descriptions of death and suffering caused by mosquito-borne diseases in many eras. Florence Nightingale called the Pontine Marshes, near Rome, “the Valley of the Shadow of Death”; a German missionary visiting the southern United States wrote that it was “in the spring a paradise, in the summer a hell, and in the autumn a hospital”; a Mayan survivor of post-Columbus epidemics remembered, “Great was the stench of death. . . . All of us were thus. We were born to die!” And yet human beings lived with, and died from, mosquito-borne diseases for thousands of years without understanding how they were reaching us. Not until the end of the nineteenth century was it scientifically established that mosquitoes transmitted malaria. Before then, the miasma theory, holding that fevers travelled independently, through fetid environments, held sway, reflected in the very word “malaria”: we thought we were the victims of “bad air.” That these tiny biting insects might be affecting our lives so profoundly was a leap beyond imagining.

Winegard is particularly interested in wars and conquests, and argues that, for much of military history, deaths caused by mosquitoes far outnumbered, and were more decisive than, deaths in battle. Malaria has many strains, of varying deadliness, but survival rates are lowest for people encountering new varieties to which they have not been “seasoned”—to which they have gained no immunity. As a result, endemic malaria has often acted not only as a local curse but also as a strange sort of protector. Fifteen centuries before the Scottish tried to colonize Panama, the Romans tried to colonize them, and were thwarted by a strain of malaria local to Scotland which is estimated to have killed half of the eighty thousand Roman soldiers sent their way. Endemic strains decimated Hannibal’s forces as they made their way through Italy, turned the armies of Genghis Khan away from southern Europe, prevented European crusaders from conquering the Holy Land (malaria killed more than a third of them), and sided with North American colonists and Latin American revolutionaries in their rebellions against armies brought in from a distant, ruling continent.

Military strategists, from Saladin to the Nazis, used mosquitoes as direct weapons of war. At Walcheren, Napoleon breached dikes to create a brackish flood—the ensuing malaria epidemic killed four thousand English soldiers—and declared, “We must oppose the English with nothing but fever, which will soon devour them all.” Often, of course, malaria exacted a toll on both sides. It pushed English Protestants into Catholic Ireland, setting the stage for the Troubles centuries later. But Oliver Cromwell, the Englishman who conquered Ireland, died of malaria, in 1658, rather than take quinine, the only known treatment, because he associated it with its Catholic discoverers, making him a victim of both parasitosis and sectarianism.

The most dramatic conquest by mosquitoes came when old diseases encountered a new continent. When Columbus arrived in the New World, the mosquitoes there were pesky but carried no diseases. (Winegard chalks this up to different farming practices here: far less cultivation and disruption of natural ecosystems, and less direct contact with animals through husbandry. Syphilis was perhaps the only disease to ride the Columbian Exchange eastward.) But the blood of the new arrivals, and the mosquitoes that crossed with their ships, changed everything. Just twenty-two years after Columbus stepped onto Hispaniola, a census revealed that the local Taino population had dropped from between five and eight million people to just twenty-six thousand. Along with smallpox and influenza, mosquito-borne diseases led, by Winegard’s estimate, to the deaths of ninety-five million indigenous inhabitants of the Americas, from a pre-contact population of about a hundred million.

To the colonizers, who spread more slowly than the diseases they brought, these were largely invisible deaths, which helped create the pernicious myth of an empty continent and a Manifest Destiny to fill it. A rare account from a marooned Spanish sailor who made his way from Florida to Mexico City in 1536 described seeing native people “so bitten by mosquitoes that you would think they had the disease of Saint Lazarus the Leper. . . . It made us extremely sad to see how fertile the land was, and very beautiful, and very full of springs and rivers, and to see every place deserted and burned villages, and the people so thin and ill.” By the seventeenth century, the losses were so great that a French explorer considered them a justification for racism: “It appears visibly that God wishes that they yield their place to new peoples.” As the recent arrivals cleared land for their own purposes, they also created fresh habitats for mosquitoes, allowing their populations to skyrocket.

The same deaths then drove the development of the transatlantic slave trade (and the arrival, with the first African slaves, of the particularly virulent malaria parasite Plasmodium falciparum, which also decimated the newly arriving Europeans). The grim history is clearly told in the prices paid for slaves in the seventeenth and eighteenth centuries: an indigenous slave, likely to die of imported disease, cost less than an also vulnerable European indentured servant, who cost less than a slave imported directly from Africa. Most expensive of all were Africans who had spent enough time in the Americas to prove their resistance to its mixture of diseases.

Similar calculations could be made about slave owners. In the Caribbean, an eighteenth-century French missionary observed that the death toll of European colonizers corresponded to the length of time that a colonizing force had had to grow accustomed to “the new air,” which is to say, yellow fever and unfamiliar strains of malaria: “Of ten men that go to the islands” from a particular nation, “four English die, three French, three Dutch, three Danes, and one Spaniard.” Today’s Caribbean nations reflect these mortality rates: those colonized by the English, the Dutch, and the French tend to have populations that are of majority African descent; only the former Spanish colonies have significant populations descended from Europeans.

In total, Winegard estimates that mosquitoes have killed more people than any other single cause—fifty-two billion of us, nearly half of all humans who have ever lived. He calls them “our apex predator,” “the destroyer of worlds,” and “the ultimate agent of historical change.”

There’s a long tradition of history books that profess to explain the world through singular factors: salt or cod or the color blue. “The Mosquito” suffers from the necessary myopia of the genre (in addition to some florid writing, repetition, and digressions through blockbuster movies and the Western Civ highlight reel). Winegard notes that wealthy Romans built their houses on hilltops to escape mosquitoes, and says that the fad has continued to the present, with U.S. houses on hills selling at a notable markup. “Add the real estate market to the mosquito’s portfolio of influence,” he concludes, ignoring other possible reasons for this preference. His argument that mosquitoes are responsible for the Magna Carta and, therefore, modern democracy is a cascade of contingencies: the failure of Louis VII’s siege of Damascus during the malaria season of 1148 led to his separation from Eleanor of Aquitaine, which led her to marry Henry II of England, which led to the birth to King John, who sparred with his barons. Winegard doesn’t need these double-jointed reaches to persuade us of the hidden influence mosquitoes have had in shaping history and creating the world that we know today.

In these days of insecticides and drained swamps, those of us who live in the rich, temperate world have become accustomed to the luxury of not thinking very much about mosquitoes and the risks they carry. But the insects are still killing more than eight hundred thousand people a year, primarily in Africa. Winegard’s reminder of their enormous potential for destruction is a timely one for all of us. Globalization is helping to spread a new generation of mosquito-borne illnesses once confined to the tropics, such as dengue, perhaps a thousand years old, and chikungunya and Zika, both of which were first identified in humans only in 1952. Meanwhile, climate change is dramatically expanding the ranges in which mosquitoes and the diseases they carry can thrive. One recent study estimated that, within the next fifty years, a billion more people could be exposed to mosquito-borne infections than are today.

Centuries later, it’s easy to read the tale of the failed Scottish colony in Panama as a farce: all that wool in the tropics, the printing press on the empty beach, an assault of pure optimism foundering against a deadly reality. Yet we modern folk are also guilty of believing that our hopes and our technology will somehow make us exempt from the workings of the natural world. The entire time that humanity has been in existence, the mosquito has been proof that we are not. ♦