When the end came for the first Andean empire, it wasn't pretty. The Wari state controlled most of the Peruvian highlands and coast, integrating disparate cultures and building a network of roads that the Inca would later repurpose for their own empire. But its collapse around 1000 C.E. amid a severe drought unleashed centuries of violence and deprivation, according to new research presented here last week at the World Congress on Mummy Studies.
The work, by Tiffiny Tung, a bioarchaeologist at Vanderbilt University in Nashville, traces violence and hardship so intense that they left a vivid record in people's bones. It combines cutting-edge methods to paint a detailed picture of a centuries-long social breakdown, and how state collapse can lead to indiscriminate violence. "When the state declined, novel ideas emerged regarding who could engage in violence, who could be targeted in violent acts, and how deadly those attacks might be," Tung reported.
"I was really impressed" by the work, said Maricarmen Vega, a bioarchaeologist at the Pontifical Catholic University of Peru here, who studies violence in pre-Columbian societies along the Peruvian coast. Tung's analysis of skeletons from during and after the collapse, in which she tallied injuries and tracked changes in bone chemistry, "goes beyond the traditional studies of trauma."
Beginning around 600 C.E.—800 years before the rise of the Inca—the Wari swept out of their capital of Huari in Peru's southern highlands and conquered nearly the entire Peruvian Andes and coast. Sometimes they used force and took captives; other times they expanded peacefully by building irrigation canals in dry regions and extending the benefits of agriculture to the people there. But by 1000, political infighting, perhaps abetted by the intensifying drought, had cracked apart the Wari state.
Studying bones excavated from Huari, Tung found grisly clues to what life was like for Wari's former subjects during and after the empire's fall. She compared skulls found at two sites in the city. The bones at one site were radiocarbon dated to between 897 and 1150, around the tail end of the Wari empire. The bones at the other dated from 1270 to 1390, several centuries after the Wari collapse.
Even in their heyday, the Wari were no strangers to violence. In earlier work, Tung had studied their practice of decapitating captives from conquered communities to create mummified trophy heads. But as long as the empire was strong, the violence was ritualized and limited. From previous excavations, Tung found that in imperial Huari, only 20% of adult skulls had healed skull fractures, which are evidence of nonlethal head injuries, and barely any had suffered fatal wounds. During and immediately after the collapse, however, nearly 60% of adults of both sexes and 38% of children showed signs of nonlethal head injury.
Centuries later, life in Huari had gone from bad to worse. Rates of nonlethal head trauma hadn't changed much, but fatal injuries had skyrocketed. At the time of the collapse, only 10% of adults had died of a head injury, but now the rate of fatal head injury had risen to 40% among adults and 44% in children. "Violence becomes much more deadly," Tung said in her talk. "These violent deaths aren't from random outbreaks of community brawls. This is much more systematic, lethal violence, but it's unclear at this time if it's from civil war or warfare with those perceived as outsiders."
Diets also seem to have deteriorated in the generations after the collapse, reported Theresa Miller, a chemical engineering student at Vanderbilt who worked with Tung. The mainstay of the Wari diet had been maize, which left a signature ratio of carbon isotopes in their bones. They also ate meat from domesticated camelids like alpacas and llamas, which left a distinctive ratio of nitrogen isotopes. Analysis of the carbon isotopes in bone collagen showed that immediately after the collapse, men, women, and children continued to eat a diet rich in maize, and their protein consumption also held steady.
Several hundred years later, Miller found, men and children were still eating plenty of maize—but women's carbon isotopes had changed drastically, indicating that for them, the staple crop was off the menu. At the same time, the whole population's nitrogen levels shot up. That could mean that they were eating more fish, possibly from increased trade with the coast, or were fertilizing their crops with guano or manure, Miller said. But high nitrogen levels can also be a sign of starvation, generated as the body burns through its own fat and muscle for fuel. By this time, core samples from Andean glaciers and lakebeds show, the drought had been going on for centuries, with what was probably a devastating impact on agriculture.
The social breakdown extended to the treatment of the dead, Tung reported. Many pre-Columbian Peruvian cultures, including the Wari, carefully bundled their dead in layers of textiles and buried them with offerings. In contrast, Tung said, the post-Wari skeletons were discovered jumbled in a ditch along the outside wall of what was once a ritual space. Many bones showed cut marks, indicating that their flesh had been stripped off. It's possible that "part of the attack on the individuals includes the desecration of their bodies," Tung said.
Rick Smith, a doctoral student in anthropology at the University of Texas, Austin, is now looking for other molecular indicators of stress in the bones from Huari. In modern people, chronic stress and violence are known to boost chemical changes in DNA known as methylation, and Smith is looking for the same pattern in ancient genetic material recovered from Tung's skeletons. He is hoping for new insights into life and health during the Wari collapse, such as whether the effects of stress were passed down through generations.
In her talk, Tung pointed out that violence hadn't always been Wari's answer to environmental stress. In fact, the Wari built their empire during a previous drought, thanks in part to their mastery of complex irrigation techniques. But she speculates that once the political system broke apart, the Wari could no longer cope with the increasingly harsh climate. "It's a one-two punch," she said. "The drought is layered on top of these other really intense changes."
Tung now hopes to find skeletons from other times during and after the Wari collapse to pinpoint the moment when the residents of Huari tipped from social cooperation into indiscriminate violence—and perhaps link it to a specific environmental or social shift. "It's the type of research we need," said bioarchaeologist Kenneth Nystrom of the State University of New York at New Paltz, who has worked in Peru and studies the bones of marginalized populations. "Looking at the varying human response to environmental change ... What could be more relevant?"
*Correction, 22 August, 10:20 a.m.: An earlier version of this article stated that Tung led the Huari excavations. The excavations were actually carried out by the Peruvian archaeologists Mario Benavides, Francisco Solano, and Enrique Bragayrac in the 1970s and 1980s.