I have just pulled a fast one. The Inka history above is as contemporary scholars understand it. They disagree on which social factors to emphasize and on how much weight to assign individual Spanish chronicles, but the outline seems not in serious dispute. The same is not true of my rendering of Pizarro’s conquest. I presented what is more or less the account current when Dobyns arrived in Peru. But in his reading he discovered a hole in this version of events—a factor so critical that it drastically changed Dobyns’s view of native America.

Why did the Inka lose? The usual answer is that Pizarro had two advantages: steel (swords and armor, rifles and cannons) and horses. The Indians had no steel weapons and no animals to ride (llamas are too small to carry grown men). They also lacked the wheel and the arch. With such inferior technology, Tawantinsuyu had no chance. “What could [the Inka] offer against this armory?” asked John Hemming, the conquest historian. “They were still fighting in the bronze age.” The Inka kept fighting after Atawallpa’s death. But even though they outnumbered the Europeans by as much as a hundred to one, they always lost. “No amount of heroism or discipline by an Inka army,” Hemming wrote, “could match the military superiority of the Spaniards.”

But just as guns did not determine the outcome of conflict in New England, steel was not the decisive factor in Peru. True, anthropologists have long marveled that Andean societies did not make steel. Iron is plentiful in the mountains, yet the Inka used metal for almost nothing useful. In the late 1960s, Heather Lechtman, an archaeologist at the MIT Center for Materials Research in Archaeology and Ethnology, suggested to “an eminent scholar of Andean prehistory that we take a serious and careful look at Andean metallurgy.” He responded, “But there wasn’t any.” Lechtman went and looked anyway. She discovered that Inka metallurgy was, in fact, as refined as European metallurgy, but that it had such different goals that academic experts had not even recognized it.

According to Lechtman, Europeans sought to optimize metals’ “hardness, strength, toughness, and sharpness.” The Inka, by contrast, valued “plasticity, malleability, and toughness.” Europeans used metal for tools. Andean societies primarily used it as a token of wealth, power, and community affiliation. European metalworkers tended to create metal objects by pouring molten alloys into shaped molds. Such foundries were not unknown to the Inka, but Andean societies vastly preferred to hammer metal into thin sheets, form the sheets around molds, and solder the results. The results were remarkable by any standard—one delicate bust that Lechtman analyzed was less than an inch tall but made of twenty-two separate gold plates painstakingly joined.

If a piece of jewelry or a building ornament was to proclaim its owner’s status, as the Inka desired, it needed to shine. Luminous gold and silver were thus preferable to dull iron. Because pure gold and silver are too soft to hold their shape, Andean metalworkers mixed them with other metals, usually copper. This strengthened the metal but turned it an ugly pinkish-copper color. To create a lustrous gold surface, Inka smiths heated the copper-gold alloy, which increases the rate at which the copper atoms on the surface combine with oxygen atoms in the air—it makes the metal corrode faster. Then they pounded the hot metal with mallets, making the corrosion flake off the outside. By repeating this process many times, they removed the copper atoms from the surface of the metal, creating a veneer of almost pure gold. Ultimately the Inka ended up with strong sheets of metal that glittered in the sun.

Andean cultures did make tools, of course. But rather than making them out of steel, they preferred fiber. The choice is less odd than it may seem. Mechanical engineering depends on two main forces: compression and tension. Both are employed in European technology, but the former is more common—the arch is a classic example of compression. By contrast, tension was the Inka way. “Textiles are held together by tension,” William Conklin, a research associate at the Textile Museum in Washington, D.C., told me. “And they exploited that tension with amazing inventiveness and precision.”

In the technosphere of the Andes, Lechtman explained, “people solved basic engineering problems through the manipulation of fibers,” not by creating and joining hard wooden or metal objects. To make boats, Andean cultures wove together reeds rather than cutting up trees into planks and nailing them together. Although smaller than big European ships, these vessels were not puddle-muddlers; Europeans first encountered Tawantinsuyu in the form of an Inka ship sailing near the equator, three hundred miles from its home port, under a load of fine cotton sails. It had a crew of twenty and was easily the size of a Spanish caravelle. Famously, the Inka used foot-thick cables to make suspension bridges across mountain gorges. Because Europe had no bridges without supports below, they initially terrified Pizarro’s men. Later one conquistador reassured his countrymen that they could walk across these Inka inventions “without endangering themselves.”

Andean textiles were woven with great precision—elite garments could have a thread count of five hundred per inch—and structured in elaborate layers. Soldiers wore armor made from sculpted, quilted cloth that was almost as effective at shielding the body as European armor and much lighter. After trying it, the conquistadors ditched their steel breastplates and helmets wholesale and dressed like Inka infantry when they fought.

Although Andean troops carried bows, javelins, maces, and clubs, their most fearsome weapon, the sling, was made of cloth. A sling is a woven pouch attached to two strings. The slinger puts a stone or slug in the pouch, picks up the strings by the free ends, spins them around a few times, and releases one of the strings at the proper moment. Expert users could hurl a stone, the Spanish adventurer Alonso Enríquez de Guzmán wrote, “with such force that it will kill a horse…. I have seen a stone, thus hurled from a sling, break a swordin two pieces when it was held in a man’s hand at a distance of thirty paces.” (Experimenting with a five-foot-long, Andean-style sling and an egg-sized rock from my garden, I was able, according to my rough calculation, to throw the stone at more than one hundred miles per hour. My aim was terrible, though.)

In a frightening innovation, the Inka heated stones in campfires until they were red hot, wrapped them in pitch-soaked cotton, and hurled them at their targets. The cotton caught fire in midair. In a sudden onslaught the sky would rain burning missiles. During a counterattack in May 1536 an Inka army used these missiles to burn Spanish-occupied Qosqo to the ground. Unable to step outside, the conquistadors cowered in shelters beneath a relentless, weeks-long barrage of flaming stone. Rather than evacuate, the Spanish, as brave as they were greedy, fought to the end. In a desperate, last-ditch counterattack, the Europeans eked out victory.

More critical than steel to Pizarro’s success was the horse. The biggest animal in the Andes during Inka times was the llama, which typically weighs three hundred pounds. Horses, four times as massive, were profoundly, terribly novel. Add to this the shock of observing humans somehow astride their backs like half-bestial nightmare figures and it is possible to imagine the dismay provoked by Pizarro’s cavalry. Not only did Inka infantrymen have to overcome their initial stupefaction, their leaders had to reinvent their military tactics while in the midst of an invasion. Mounted troops were able to move at rates never encountered in Tawantinsuyu. “Even when the Indians had posted pickets,” Hemming observed, “the Spanish cavalry could ride past them faster than the sentries could run back to warn of danger.” In clash after clash, “the dreaded horses proved invincible.” But horses are not inherently unbeatable; the Inka simply did not discover quickly enough where they had an advantage: on their roads.


The conquistadors disparaged steep Inka highways because they had been designed for sure-footed llamas rather than horses. But they were beautifully made—this road, photographed in the 1990 s, had lasted more than five hundred years without maintenance.

European-style roads, constructed with horses and cars in mind, view flatness as a virtue; to go up a steep hill, they use switchbacks to make the route as horizontal as possible. Inka roads, by contrast, were built for llamas. Llamas prefer the coolness of high altitudes and, unlike horses, readily go up and down steps. As a result, Inka roads eschewed valley bottoms and used long stone stairways to climb up steep hills directly—brutal on horses’ hooves, as the conquistadors often complained. Traversing the foothills to Cajamarca, Francisco Pizarro’s younger brother Hernando lamented that the route, a perfectly good Inka highway, was “so bad” that the Spanish “could not use horses on the roads, not even with skill.” Instead the conquistadors had to dismount and lead their reluctant animals through the steps. At that point they were vulnerable. Late in the day, Inka soldiers learned to wait above and roll boulders on their foes, killing some of the animals and frightening others into running away. Men left behind could be picked off at leisure. Multiple ambushes cost the lives of many Spanish troops and animals.

To be sure, horses confer an advantage on flat ground. But even on the plains the Inka could have won. Foot soldiers have often drubbed mounted troops. At the battle of Marathon in 490 B.C., the outnumbered, outarmored Athenian infantry destroyed the cavalry of the Persian emperor Darius I. More than six thousand Persians died; the Greeks lost fewer than two hundred men. So dire had the situation initially appeared that before the fight Athens sent a messenger to Sparta, its hated rival, to beg for aid. In the original marathon, the courier ran more than a hundred miles in two days to deliver his message. But by the time the Spartan reinforcements arrived, there was nothing to see but dead Persians.

The Inka losses were not foreordained. Their military was hampered by the cult of personality around its deified generals, which meant both that leaders were not easily replaced when they were killed or captured and that innovation in the lower ranks was not encouraged. And the army never learned to bunch its troops into tight formations, as the Greeks did at Marathon, forming human masses that can literally stand up to cavalry. Nonetheless, by the time of the siege of Qosqo the Inka had developed an effective anti-cavalry tactic: bolas. The Inka bola consisted of three stones tied to lengths of llama tendon. Soldiers threw them, stones a-whirl, at charging horses. The weapons wrapped themselves around the animals’ legs and brought them down to be killed by volleys of sling missiles. Had the bolas come in massed, coordinated onslaughts instead of being wielded by individual soldiers as they thought opportune, Pizarro might well have met his match.

If not technology or the horse, what defeated the Inka? As I said, some of the blame should be heaped on the overly centralized Inka command structure, a problem that has plagued armies throughout time. But another, much larger part of the answer was first stated firmly by Henry Dobyns. During his extracurricular reading about Peru, he came across a passage by Pedro Cieza de León, the Spanish traveler who observed three roads between the same two cities. Entranced by the first exhibition of Inka booty in Spain, Cieza de León had crossed the Atlantic as a teenager and spent fifteen years in Peru, Bolivia, Ecuador, and Colombia, traveling, fighting, and taking notes for what would become a massive, three-volume survey of the region. Only the first part was printed in his lifetime, but by the twentieth century historians had found and published most of the rest. Dobyns learned something from Cieza de León that was not mentioned in Prescott’s history, in the Smithsonian’s official Handbook of South American Indians, or in any of the then-standard descriptions of Tawantinsuyu. According to Cieza de León, Wayna Qhapaq, Atawallpa’s father, died when “a great plague of smallpox broke out [in 1524 or 1525], so severe that more than 200,000 died of it, for it spread to all parts of the kingdom.”

Smallpox not only killed Wayna Qhapaq, it killed his son and designated heir—and his brother, uncle, and sister-wife. The main generals and much of the officer corps died, wrote the Inka chronicler Santacruz Pachacuti Yamqui Salcamayhua, “all their faces covered with scabs.” So did the two regents left in Qosqo by Wayna Qhapaq to administer the empire. After the dying Wayna Qhapaq locked himself away so that nobody could see his pustulous face, Salcamayhua reported, he was visited by a terrifying midnight vision. Surrounding him in his dream were “millions upon millions of men.” The Inka asked who they were. “Souls of the lost,” the multitude told him. All of them “would die from the pestilence,” each and every one.

The story is probably apocryphal, but its import isn’t. Smallpox has an incubation period of about twelve days, during which time sufferers, who may not know they are sick, can infect anyone they meet. With its fine roads and great population movements, Tawantinsuyu was perfectly positioned for a major epidemic. Smallpox radiated throughout the empire like ink spreading through tissue paper. Millions of people simultaneously experienced its symptoms: high fever, vomiting, severe pain, oozing blisters everywhere on the body. Unable to number the losses, the Jesuit Martín de Murúa said only that the toll was “infinite thousands.”

The smallpox virus is thought to have evolved from a cattle virus that causes cowpox; a now-extinct equine virus responsible for horsepox; or, perhaps most likely, the camelpox virus, which affects camels, as the name suggests. People who survive the disease become immune to it. In Europe, the virus was such a constant presence that most adults were immune. Because the Western Hemisphere had no cows, horses, or camels, smallpox had no chance to evolve there. Indians had never been exposed to it—they were “virgin soil,” in epidemiological jargon.

Virgin-soil death rates for smallpox are hard to establish because for the last century most potential research subjects have been vaccinated. But a study in the early 1960s of seven thousand unvaccinated smallpox cases in southern India found that the disease killed 43 percent of its victims. Noting the extreme vulnerability of Andean populations—they would not even have known to quarantine victims, as Europeans had—Dobyns hypothesized that the empire’s population “may well have been halved during this epidemic.” In about three years, that is, as many as one out of two people in Tawantinsuyu died.

The human and social costs are beyond measure. Such overwhelming traumas tear at the bonds that hold cultures together. The epidemic that struck Athens in 430 B.C., Thucydides reported, enveloped the city in “a great degree of lawlessness.” The people “became contemptuous of everything, both sacred and profane.” They joined ecstatic cults and allowed sick refugees to desecrate the great temples, where they died untended. A thousand years later the Black Death shook Europe to its foundations. Martin Luther’s rebellion against Rome was a grandson of the plague, as was modern anti-Semitism. Landowners’ fields were emptied by death, forcing them either to work peasants harder or pay more to attract new labor. Both choices led to social unrest: the Jacquerie (France, 1358), the Revolt of Ciompi (Florence, 1378), the Peasants’ Revolt (England, 1381), the Catalonian Rebellion (Spain, 1395), and dozens of flare-ups in the German states. Is it necessary to spell out that societies mired in fratricidal chaos are vulnerable to conquest? To borrow a trope from the historian Alfred Crosby, if Genghis Khan had arrived with the Black Death, this book would not be written in a European language.

As for Tawantinsuyu, smallpox wiped out Wayna Qhapaq and his court, which led to civil war as the survivors contested the spoils. The soldiers who died in the battle between Atawallpa and Washkar were as much victims of smallpox as those who died from the virus itself.

The ferocity of the civil war was exacerbated by the epidemic’s impact on a peculiarly Andean institution: royal mummies. People in Andean societies viewed themselves as belonging to family lineages. (Europeans did, too, but lineages were more important in the Andes; the pop-cultural comparison might be The Lord of the Rings, in which characters introduce themselves as “X, son of Y” or “A, of B’s line.”) Royal lineages, called panaqa, were special. Each new emperor was born in one panaqa but created a new one when he took the fringe. To the new panaqa belonged the Inka and his wives and children, along with his retainers and advisers. When the Inka died his panaqa mummified his body. Because the Inka was believed to be an immortal deity, his mummy was treated, logically enough, as if it were still living. Soon after arriving in Qosqo, Pizarro’s companion Miguel de Estete saw a parade of defunct emperors. They were brought out on litters, “seated on their thrones and surrounded by pages and women with flywhisks in their hands, who ministered to them with as much respect as if they had been alive.”

Because the royal mummies were not considered dead, their successors obviously could not inherit their wealth. Each Inka’s panaqa retained all of his possessions forever, including his palaces, residences, and shrines; all of his remaining clothes, eating utensils, fingernail parings, and hair clippings; and the tribute from the land he had conquered. In consequence, as Pedro Pizarro realized, “the greater part of the people, treasure, expenses, and vices [in Tawantinsuyu] were under the control of the dead.” The mummies spoke through female mediums who represented the panaqa’s surviving courtiers or their descendants. With almost a dozen immortal emperors jostling for position, high-level Inka society was characterized by ramose political intrigue of a scale that would have delighted the Medici. Emblematically, Wayna Qhapaq could not construct his own villa on Awkaypata—his undead ancestors had used up all the available space. Inka society had a serious mummy problem.

After smallpox wiped out much of the political elite, each panaqa tried to move into the vacuum, stoking the passions of the civil war. Different mummies at different times backed different claimants to the Inka throne. After Atawallpa’s victory, his panaqa took the mummy of Thupa Inka from its palace and burned it outside Qosqo—burned it alive, so to speak. And later Atawallpa instructed his men to seize the gold for his ransom as much as possible from the possessions of another enemy panaqa, that of Pachacuti’s mummy.

Washkar’s panaqa kept the civil war going even after his death (or, rather, nondeath). While Atawallpa was imprisoned, Washkar’s panaqa sent one of his younger brothers, Thupa Wallpa, to Cajamarca. In a surreptitious meeting with Pizarro, Thupa Wallpa proclaimed that he was Washkar’s legitimate heir. Pizarro hid him in his own quarters. Soon afterward, the lord of Cajamarca, who had backed Washkar in the civil war, told the Spanish that Atawallpa’s army was on the move, tens of thousands strong. Its generals planned to attack Pizarro, he said, and free the emperor. Atawallpa denied the charge, truthfully. Pizarro nonetheless ordered him to be bound. Some of the Spaniards most sympathetic to Atawallpa asked to investigate. Soon after they left, two Inka ran to Pizarro, claiming that they had just fled from the invading army. Pizarro hurriedly convoked a military tribunal, which quickly sentenced the Inka to execution—the theory apparently being that the approaching army would not attack if its leader were dead. Too late the Spanish expedition came back to report that no Inka army was on the move. Thupa Wallpa emerged from hiding and was awarded the fringe as the new Inka.

The execution, according to John Rowe, the Berkeley archaeologist, was the result of a conspiracy among Pizarro, Thupa Wallpa, and the lord of Cajamarca. By ridding himself of Atawallpa and taking on Thupa Wallpa, Rowe argued, Pizarro “had exchanged an unwilling hostage for a friend and ally.” In fact, Thupa Wallpa openly swore allegiance to Spain. To him, the oath was a small price to pay; by siding with Pizarro, Washkar’s panaqa, “which had lost everything, had a chance again.” Apparently the new Inka hoped to return with Pizarro to Qosqo, where he might be able to seize the wheel of state. After that, perhaps, he could wipe out the Spaniards.


Although Andean societies have been buffeted by disease and economic exploitation since the arrival of Europeans, indigenous tradition remained strong enough that this chicha seller in Cuzco, photographed by Martín Chambi in 1921, might have seemed unremarkable in the days of the Inka.

On the way to Qosqo, Pizarro met his first important resistance near the river town of Hatun Xauxa, which had been overrun by Atawallpa’s army during the civil war. The same force had returned there to battle the Spanish. But the Inka army’s plan to burn down the town and prevent the invaders from crossing the river was foiled by the native Xauxa and Wanka populace, which had long resented the empire. Not only did they fight the Inka, they followed the old adage about the enemy of my enemy being my friend and actually furnished supplies to Pizarro.

After the battle Thupa Wallpa suddenly died—so suddenly that many Spaniards believed he had been poisoned. The leading suspect was Challcochima, one of Atawallpa’s generals, whom Pizarro had captured at Cajamarca and brought along on his expedition to Qosqo. Challcochima may not have murdered Thupa Wallpa, but he certainly used the death to try to persuade Pizarro that the next Inka should be one of Atawallpa’s sons, not anyone associated with Washkar. Meanwhile, Washkar’s panaqa sent out yet another brother, Manqo Inka. He promised that if he were chosen to succeed Thupa Wallpa he would swear the same oath of allegiance to Spain. In return, he asked Pizarro to kill Challcochima. Pizarro agreed and the Spaniards publicly burned Challcochima to death in the main plaza of the next town they came to. Then they rode toward Qosqo.

To Dobyns, the moral of this story was clear. The Inka, he wrote in his 1963 article, were not defeated by steel and horses but by disease and factionalism. In this he was echoing conclusions drawn centuries before by Pedro Pizarro. Had Wayna Qhapaq “been alive when we Spaniards entered this land,” the conquistador remarked, “it would have been impossible for us to win it…. And likewise, had the land not been divided by the [smallpox-induced civil] wars, we would not have been able to enter or win the land.”

Pizarro’s words, Dobyns realized, applied beyond Tawantinsuyu. He had studied demographic records in both Peru and southern Arizona. In both, as in New England, epidemic disease arrived before the first successful colonists. When the Europeans actually arrived, the battered, fragmented cultures could not unite to resist the incursion. Instead one party, believing that it was about to lose the struggle for dominance, allied with the invaders to improve its position. The alliance was often successful, in that the party gained the desired advantage. But its success was usually temporary and the culture as a whole always lost.

Between the sixteenth and eighteenth centuries, this pattern occurred again and again in the Americas. It was a kind of master narrative of postcontact history. In fact, Europeans routinely lost when they could not take advantage of disease and political fragmentation. Conquistadors tried to take Florida half a dozen times between 1510 and 1560—and failed each time. In 1532 King João III of Portugal divided the coast of Brazil into fourteen provinces and dispatched colonists to each one. By 1550 only two settlements survived. The French were barely able to sustain trading posts in the St. Lawrence and didn’t even try to plant their flag in pre-epidemic New England. European microorganisms were slow to penetrate the Yucatán Peninsula, where most of the Maya polities were too small to readily play off against each other. In consequence, Spain never fully subdued the Maya. The Zapatista rebellion that convulsed southern Mexico in the 1990s was merely the most recent battle in an episodic colonial war that began in the sixteenth century.

All of this was important, the stuff of historians’ arguments and doctoral dissertations, but Dobyns was thinking of something else. If Pizarro had been amazed by the size of Tawantinsuyu after the terrible epidemic and war, how many people had been living there to begin with? Beyond that, what was the population of the Western Hemisphere in 1491?

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