Scientists studied over 1,500 ancient Peruvians across 3,000 years to understand how societies respond to climate disasters; despite human sacrifices following El Niño flooding, everyday violence was rare.
When drought, flooding or famine arrives, it is often expected to trigger chaos, as food becomes scarce and communities struggle to survive. History offers plenty of examples of societies that were pushed to the brink by environmental disasters. But have climate disasters led to violence? A new study of the Lambayeque Valley on Peru’s northern coast provides a surprising answer. Researchers from New York University and George Mason University examined the skeletons of ancient Peruvians from 30 sites spanning more than 3,000 years. They found that violence was rare, even during El Niño floods that devastated fishing and farming. The findings are published in the journal Frontiers in Environmental Archaeology.
The researchers wanted to understand how societies might react to climate disasters. So they examined social responses to extreme climate events in the past, including instances of human sacrifice. Mass human sacrifices in northern Peru have been linked to catastrophic flooding caused by El Niño. This prompted the researchers to investigate whether such sacrifices were driven by food shortages following environmental disasters. Contrary to popular belief, a new survey of the Lambayeque Valley suggests that violence was extremely rare, even during periods of ecological upheaval. “The main thing that jumped out at us was just how few cases of interpersonal violence we observed outside ritualised contexts,” Dr Thomas Snyder of New York University, co-author of the article in Frontiers in Environmental Archaeology, said. “This really highlights that widespread violence isn’t a predetermined response to climate change. As a society, we both get to and have to choose how we respond to our own climate crisis.” “In Lambayeque, there’s 6,000 years of creative adaptations to El Niño and longer-term changes in climate, and widespread violence wasn’t one of them,” Dr Haagen Klaus of George Mason University, a co-author, explained. “Violence and social unravelling are not destined outcomes, ever.”
The Lambayeque Valley sits on Peru’s arid northern coast, where rainfall is scarce. For thousands of years, residents relied on rivers and the rich waters offshore. El Niño, however, changed that pattern. Warm ocean conditions wiped out fish stocks and brought torrential rain to the valley, leaving farmers and fishers with little to eat. Archaeologists have long linked these disasters to some of the region’s extreme practices. Mass ritual sacrifices took place just before the collapse of the Moche and Sicán political systems, raising the question of whether these spectacles reflected a wider breakdown in daily life. The researchers studied the Lambayeque Valley Biohistory Project’s skeletal collection, which covers 30 sites and more than 3,000 years of the valley’s history. They looked for cranial trauma, which usually points to violence, and postcranial trauma, which usually points to accidents. They then compared these injuries with shifts in rainfall and water availability. “The Lambayeque Valley was home to a sequence of creative, innovative, and resilient cultures. The people of ancient Lambayeque were probably very different from us. On the other hand, archaeological evidence shows that in so many ways they were mirrors of us — in how they lived their daily lives, interacted with their world, ran their economies, and confronted (and sometimes contributed to) environmental crises,” Klaus said. The valley received very little rainfall, so its communities depended on rivers and the sea. But El Niño events changed everything, throwing local food production systems into crisis. “Leaders of the Moche and Sicán appear to have held power partly through their claims to be intercessors with the natural world. Large-scale events involving human sacrifice just before the collapse of the Moche and Sicán political systems appear to have been attempts to bring the forces of nature back into balance by offering their most precious lives to the supernatural. It’s here that the most extensive evidence of violence is found in Lambayeque,” Klaus explained. “If these big ritual sacrifices were indicative of some underlying crisis, we hypothesised that these events might have been extending into people’s everyday experience of the world,” Snyder said.
However, what the researchers found was striking. Only 25 individuals, or 1.6 per cent of the sample, showed signs of violence. Another 77, or 5.1 per cent, showed signs of accidental trauma. Neither category correlated with ecological instability. Sex did not predict violence either. The researchers noted that this is uncommon compared with findings from other sites, such as those in the Andes, where cranial trauma is much more common, especially during periods of climatic upheaval. Snyder and Klaus suggest that the valley’s access to the coast may have eased the pressure of scarcity. Another possibility is that the people of Lambayeque organised their societies in ways that deliberately limited bloodshed. “One of the challenges ended up being temporal resolution. With an archaeological sample size this large, it just wouldn’t be feasible to radiocarbon-date every individual. So we’re really looking at long-term associations — or their absence. In an ideal world, I would like to radiocarbon-date the entire sample, to see if any trends appear that we might have missed,” Snyder said. “A lot of people think that archaeological research is interesting, but we really want to emphasise that it is also useful. As the saying goes, ‘there is nothing new under the sun’. By looking to the past, we can answer questions about how people have dealt with similar crises to those we’re facing now and apply that knowledge to the present,” he concluded.
