Wider WorldMore than 3,000 years, Cupisnique to Chimú periods · Lambayeque Valley Complex, Lambayeque, Peru
Ancient Peru sacrificed people after El Niño floods, yet everyday violence on its coast stayed rare for 3,000 years
Only 1.6 per cent of skeletons from the Lambayeque Valley Complex show injuries from violence, and the rate did not rise with floods or drought.
In brief 3 key points
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- Skeletons from 30 sites in northern Peru cover more than 3,000 years
- Only 25 people showed head injuries from violence outside ritual killings
- Neither violence nor accidents tracked rainfall or El Niño floods
Mass human sacrifices on the desert coast of northern Peru have been linked to catastrophic El Niño floods. A new study asked whether ordinary violence rose with them. In the Lambayeque Valley Complex, it found that violence outside ritual killings was rare for more than 3,000 years.
Thomas Snyder of New York University and Haagen Klaus of George Mason University published the study on 9 November in Frontiers in Environmental Archaeology. Klaus founded the Lambayeque Valley Biohistory Project in 2002.
Sacrifices in times of flood
Around AD 550 to 600, up to 107 adult men were sacrificed at the Moche centre of Huaca de la Luna during a huge El Niño. Around 1450, more than 140 children and over 200 young camelids were sacrificed at Huanchaquito-las Llamas, near the Chimú capital Chan Chan. Both events are tied to layers of mud from flooding.
The valley normally had very little rain but rich rivers and seas. El Niño events killed off fish stocks and brought torrential rain, throwing food production into crisis.
Counting injuries
The sample covers 1,659 individuals from 30 sites. The team counted head injuries as signs of violence and broken bones below the skull as signs of accidents. They compared these with simulated rainfall in the mountain headwaters and a record of El Niño floods from lake sediment cores.
Only 25 people, 1.6 per cent, showed head injuries from violence. Another 77, 5.1 per cent, had injuries from accidents. Neither type tracked rainfall or flood frequency. In other parts of the Andes, regional rates of head injuries reach 30 to 45 per cent.
“Violence and social unraveling are not destined outcomes, ever.”
Haagen Klaus, George Mason University
Why the coast stayed calm
The authors do not claim to know the cause. Sea resources and trade may have cushioned people during dry spells. Moche and Sicán leaders ruled from capitals without defensive walls and kept no large standing armies.
The results are estimates. Dating relied mostly on relative methods, and climate data came in 100-year steps. Wounds to soft tissue leave no mark on bone. The authors propose that mass sacrifice here was a political and religious act, not a consequence of food shortage.
Sources (4)
Peer-reviewed paperfrom New York University and George Mason University
- Despite sacrificing people after catastrophic El Niño flooding, ancient societies were generally peaceful (Phys.org)
- Despite sacrifices tied to El Niño floods, Peru’s ancient coast stayed peaceful for 3,000 years (Archaeology News)
- Despite sacrificing people after catastrophic El Niño flooding, ancient societies were generally peaceful (Frontiers)
- Front. Environ. Archaeol., 09 November 2026 (Frontiers in Environmental Archaeology)
Paper: Snyder and Klaus, Pax Lambayeque? Trauma, interpersonal violence, and environment over 3,000 years in the Lambayeque Valley Complex, Peru, Frontiers in Environmental Archaeology (2026)
Edited by Guiseppe Weijermars
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