The Plague Cycle

by Charles Kenny

  Though Columbus was unable to deliver on his promise after his second voyage, the Americas would provide all of this and more in time.11 But the cost that the peoples of the New World would pay for the explorer’s ambitions was foretold by his first return trip: of the seven enslaved Americans that Columbus brought back with him to Spain to prove his discoveries and provide translation on the next expedition, only two survived the voyage.

  When Europeans, including Columbus, first described Native Americans, they praised them as healthy and strong, while American Indians told one another that Europeans were small, weak, smelly, and diseased. This last point was accurate and deadly—because the interlopers passed on those diseases to their unwilling hosts. Meanwhile, the Spanish conquistadors who trekked across the New World didn’t suffer from greatly increased disease mortality themselves—the Americas didn’t host a range of new killer infections that they hadn’t been exposed to before. A Spanish settler, who arrived on Hispaniola in 1502, looked back eighteen years later at what had become of the island as a result. Hernando Gorjon reported that many Spaniards had left, while “the pestilence of smallpox, measles, flu and other illness they had given to the Indians” had killed off most of the natives.12

  The death toll of European discovery mounted as the Spanish moved to the mainland. When Cortés, conquistador and secretary to the Spanish governor, first reached the Yucatan at the start of the sixteenth century, there were still as many as 16 to 25 million people in central Mexico. In 1519, he led twelve hundred Spanish troops into the Aztec capital Tenochtitlán, where he was welcomed by Emperor Montezuma. Cortés briefly imprisoned the king in the palace of Lord Face of Water—and the king was soon dead. Montezuma’s brother Cuitláhuac was quick to revenge the former king, and Cortés was lucky to escape with half his force over a temporary bridge in the dead of night. But Cuitláhuac didn’t press his advantage—perhaps because he was already dealing with the hideous impact of infections that were surging on the mainland within months of Cortés arriving. Some diseases may have hitched a ride aboard one of the first Spanish slaving vessels to travel from Africa to the New World.13

  And so when Cortés tried conquest a second time with the support of local allies two years later, his most important weapon had already been deployed: infection was savaging his opponents, killing as much as one-half the population—including Cuitláhuac in 1520.14 The Annals of the Cakchiquels, records of Mayan people living in what is today’s Guatemala, report that “great was the stench of the dead.… Half of the people fled to the fields. The dogs and vultures devoured the bodies.”15 When Cortés and his army reached Tenochtitlán, they overcame the remaining opposition—although enough survived that Cortés was able to slaughter as many as forty thousand within a day of his arrival. There were so many dead, the explorer boasted, “we were forced to walk upon them.”16

  As Cortés’s triumph suggests, disease was considerably abetted by the immense violence of the new colonists. Bartolomé de Las Casas arrived in the New World only ten years after Columbus had discovered it. In 1502, at the age of eighteen, he became a land and slave owner on the island of Hispaniola. Eight years later, he was ordained a priest, but in that same year he was denied confession by Dominican friars on the grounds he was a slaveholder. It took four years, but the Dominicans’ message eventually had an impact: in 1514 Las Casas accepted that massacring and enslaving the local population might not be a terribly Christian approach, and he spent much of the rest of his life campaigning for their better treatment. In 1542, he wrote his Short Account of the Destruction of the Indes, which described the invaders’ “unjust, cruel, bloody, and tyrannical” warfare. “It is the Spaniards’ custom in their wars to allow only young boys and females to live,” he complained, and added a description of oppression of those who remained: “the hardest, harshest, and most heinous bondage to which men or beasts might ever be bound into.”17 By 1620–25, after repeated bouts of diseases, including smallpox, plague, and measles, exacerbated by violence and maltreatment, the population of central Mexico had collapsed.

  European diseases spread faster than European explorers did. That meant, by the time conquistadors and colonists arrived, local civilizations across North and South America were weakened or falling apart already.18 After infecting the Aztecs, for example, European diseases raged their way south, traveling the roads of the Inca Empire. Smallpox reached the capital of Cuzco by 1524, where it killed the royal family and thousands of warriors. That plunged the civilization into a desperate civil war exploited by Francisco Pizarro, who captured the Inca Emperor Atahualpa in 1532.

  In 1541, Pizarro’s half brother Gonzalo led an expedition into the Amazon in search of the legendary city of El Dorado. While he failed to find the city of gold, his second in command, Francisco de Orellana, did become the first European to navigate the Amazon. A Dominican chaplain accompanying Orellana reported that “the farther we went the more thickly populated” was the land around the river, with villages less than a crossbow-shot apart and numerous large cities. It appears that, before 1492, areas fifty miles wide or more around the Amazon and its major tributaries may have been densely occupied all the way into Peru and the base of the Andes, twenty-five hundred miles from the sea.19

  The scale of infectious destruction along the Amazon was so massive that disease in the Americas achieved what the Black Death had failed to do in Europe: complete social breakdown. The few survivors were reduced to a Stone Age forest existence, their descendants to be found today among “uncontacted tribes” like the Yanomamo. The idea that development is always arrested by tropical climates is simply not true in the case of the Amazon basin. It was reversed in part through the introduction of Old World diseases that thrived in such climates.20

  And the reversal wasn’t limited to South and Central America: agriculture occurred in as much as two-thirds of the territory of the United States before Columbus, argues Charles Mann. The scattered tribes that were met by Lewis and Clark during their exploration of the Louisiana Purchase were remnants of a massive farming culture destroyed by disease.

  * * *

  For many of the colonizers, the disease advantage was a sign of heavenly favor. Pilgrims and missionaries suggested the intervention of “the good hand of God” in the smallpox epidemics killing off Native Americans—a case of the Almighty demonstrating that he “wishes that they yield their place to new peoples.”21 This nod of approval by Providence justified exploitation, and the Spanish colonizers relied on native populations for cheap slave labor—even though directly enslaving them was eventually banned by the Spanish king.

  As native populations collapsed under the weight of infection, colonists had no choice but to look elsewhere for people to mine the metals and harvest the tobacco and sugarcane. In parts of the New World, a second option was indentured servants: Europeans contractually obliged to work for plantation masters until they’d paid off the cost of their transatlantic voyage. About three-quarters of Virginia’s settlers in the seventeenth century, along with the majority of Caribbean field labor until the middle of that century, were indentured.

  From the earliest days of colonization, African slaves were brought in alongside servants to meet the demand for labor. Slavers would often advertise that their merchandise displayed the scars carried by smallpox survivors, which meant they were immune to re-infection. Nonetheless, slaves brought with them a range of tropical diseases. These were deadly not only to Native Americans, but also colonists.

  By the late 1600s, the more lethal form of malaria, falciparum, had been introduced from Africa to the Americas along with yellow fever—a condition that rendered men prostrate with headache and muscle pain before they’d heave black vomit, endure convulsive deliria, and fall into coma and death. Colonist death rates climbed, and new indentured servants became harder to find. Demand for slaves further increased.

  Those slaves who survived the “Middle Passage” across the Atlantic were treated worse than livestock. Anyone who
attempted to flee was burned alive or left to rot in a gibbet.22 Beatings, rape, and malnutrition were the lot of those who stayed. In Haiti, a slave in Saint-Domingue described the conditions: “Have they not hung up men with heads down, drowned them in sacks, crucified them on planks, buried them alive, crushed them in mortars? Have they not forced them to eat shit?”23

  But despite the obscene conditions in which they were kept, slaves were less likely to succumb to falciparum than Europeans or native Americans because they’d been “seasoned” by exposure and some were more genetically resistant to the disease due to the sickle cell trait. The mortality rate for British soldiers of European descent in Jamaica was more than three times higher than that for soldiers of African descent in the colonial period—and malaria plays a significant part in that differential.24 The greater hardiness of slaves from malarial regions was soon plain to see, and these captive workers began collecting particularly high prices at auction—as much as 60 percent higher.

  Elena Esposito of the University of Bologna has uncovered a simple correlation: across countries, the higher colonists’ mortality, the higher the population of slaves. Again, within the US, the greater the risk of falciparum malaria across US counties, the greater the importation of slaves.25 As late as 1860, moving from an area where the risk of falciparum malaria was very low to one where it was very high was associated with an increase of more than one-quarter in the ratio of slaves in the total population, Esposito suggests.

  Farther north, where climate was unfriendly to tropical disease, Europeans remained, if anything, healthier than they’d been in the fetid villages and towns of the Old World. And because they were more seasoned to infections that thrive in cold weather, like influenza, whooping cough, and measles, they were also better adapted to the emerging disease ecology than African slaves.26 Between 1620 and 1642, only about one in twenty English people arriving in the Caribbean and North America landed in New England. But they survived and thrived in newly depopulated territories rather than falling to disease.

  A century after Cortés had triumphed with the vital aid of smallpox, the Pilgrim Fathers were to benefit to a similar extent: an epidemic almost annihilated the Massachusett people of the Algonquin nation only a year or two before the Mayflower arrived.27 With plenty of sparsely populated, pre-cleared, easily occupied land to take from the poxed Algonquin, the pilgrims rapidly multiplied. Parson Malthus was inspired to write his tract on population in part by the explosive growth of the North American colonies that, he estimated, doubled in size every twenty-five years.28 Had he grasped all of the factors behind that growth, he might better have understood the role of disease as a check on population.29

  Ultimately, in both North and South America, Old World peoples and their diseases almost completely displaced local populations. By the year 2000, some parts of the “New World” were made up of populations entirely from the Old, including Jamaica and Haiti. In many more—including the US, Canada, Cuba, Argentina, and Brazil—the descendants of the New World were less than 10 percent of the population. Only in a handful of countries in the Americas are Old World descendants the minority.30

  * * *

  The demand for labor created by collapsing populations in the Americas would have a dramatic impact on the unwilling source for that labor. In fact, the slave trade would prove to be the powerful first blow of European imperialism against Africa, wiping out civilizations there.

  The Portuguese captain Diogo Cão explored the mouth of the Congo River and met with representatives of the Kongo kingdom in 1482. By 1526, King Afonso of the Kongo was reduced to writing begging letters to the king of Portugal over the behavior of slavers in his country:

  Merchants are taking every day our natives, sons of the land and the sons of our noblemen and vassals and our relatives, because the thieves and men of bad conscience… grab them and get them to be sold; and so great, Sir, is the corruption and licentiousness that our country is being completely depopulated.31

  The Kongo king’s appeal for controls over the slave trade went ignored—indeed, the trade rapidly expanded. Between the fifteenth and nineteenth centuries, 12 million slaves were exported from Africa—around twice the population of the United Kingdom in the seventeenth century, although still less than the number of Native Americans that died from the conquistadors’ army of disease.32

  The eventual result was the collapse of the Kongo kingdom and others. Slaving set not just kingdom against kingdom but village against village, each vying to capture enough slaves to sell in return for weapons for self-protection and to take yet more slaves in the future. The slave merchants supplying labor to a New World denuded of people by infection couldn’t have created a better mechanism to spread Hobbesian disorder had they tried.

  And the slave trade itself spread infection, perhaps eventually killing off more than those who embarked on slave ships. Prior to the era of European exploration and slaving, trade routes had crisscrossed Africa for centuries. But the routes operated on a relay system—goods would be transported by the local population to the edge of its area of control, then passed on to porters from the next ethnic group. The approach may have evolved as a disease-avoidance technique.33 Certainly it limited contact and kept Africa a continent of many disease pools.

  The relay approach obviously couldn’t work with slavery—moving people was the very essence of the trade. As a result, smallpox spread throughout Africa. Falciparum malaria may have expanded its reach by the same route. Some estimates suggest the population in Africa by the mid-nineteenth century was half what it would have been absent the impact of the slave trade.

  * * *

  Economists, including Daron Acemoglu and James Robinson, authors of the bestselling analysis Why Nations Fail, suggest that colonial disease burdens can explain a considerable amount of variation between rich and poor countries today. That is because places where colonists rapidly succumbed to disease (including Central America and the Caribbean) were left with institutions that favored a small elite raking off incomes as rapidly as possible before retreating from the disease threat.34 These institutions survived decolonization and fostered inequalities that have festered. Meanwhile, Harvard economist Nathan Nunn shows that “the African countries that are the poorest today are the ones from which the most slaves were taken.”35

  Similarly, research by Stelios Michalopoulos and Elias Papaioannou of the Center for Economic Policy Research suggests that areas of Africa controlled by powerful centralized states before colonization are richer today.36 Their measure of regional wealth is how much light is visible from space at night—areas with more street lighting and houses spilling light out of their windows are better off than areas where the roads are unlit and homes are dark. It turns out this is a good indicator of average incomes in a region. Areas ruled by stronger states hundreds of years ago are brighter at night today. Given the slave trades’ terrible impact on precolonial African states, visiting aliens might not even need to land on the planet to witness some of the legacy of slaving and the infectious diseases that spurred its growth.37

  * * *

  The Age of Discovery was the beginning of the age of truly worldwide pandemic threats. Venereal syphilis provides an early example: it may well have been a New World disease brought back to Europe by sailors from Columbus’s original expedition.38 In its initial foray in Europe, it was far more virulent than it has become, causing ulcers, tumors, immense pain, and frequent death.39 As a sign of the increasing integration of the global disease pool, syphilis reached the Middle East by 1499 and China ten years after that.40 India was hit dramatically quickly—in 1498.41 That is because five years after Columbus reached America, Vasco da Gama became the first European of modern times to round Africa’s Cape of Good Hope, and he did it with a syphilitic crew.

  As the sailing ships of Europe circled the globe, island after island suffered similar consequences from an explosion of infections. The final great discovery of the age of exploration occurred in 1769, wh
en James Cook landed in Australia and started the last great continental kill-off of unexposed populations. Where North America was repopulated with slaves and indentured servants, Australia started off with British convicts. The difference was of little significance to the Aborigines. Like the native peoples left in North America, they ended up at the bottom of the pile—overwhelmingly disadvantaged in terms of income, education, and health to this day.

  Owing in part to an almost complete travel and trading ban with the rest of the world that had been in place from the 1630s, Japan held out against the full global microbial apocalypse for another ninety years. The lower disease burden was an important factor supporting one of the densest populations in the world. The city of Edo had a population of about 1 million in the early eighteenth century, considerably larger than the population of London at the time.42 But in 1853, US commodore Matthew Perry led four ships into Tokyo Bay, and returning the next year with a larger squadron, he signed the Treaty of Kanagawa with a grudging Japanese government: the country would open two ports for refueling and provisioning American ships. Disease followed soon after, including epidemic typhus and bubonic plague.43