Recent excavations at a 15th century archaeological site on the coast of Peru have revealed an enormous mass burial of 137 children, three adults, and 200 llamas or alpacas. Archaeologists argue that the sacrifice may have been related to a traumatic climate event.

The burial is part of a site called Huanchaquito-Las Llamas (HLL) in the Province of Trujillo, just 350 meters from the shore and 2 miles north of the ancient city of Chan Chan, which was the largest pre-contact city in South America and the capital of the Chimú state. The latter part of this ancient state’s 11th-15th century AD existence, however, was full of destabilizing events such as warfare, and locations like Punta Lobos and Chan Chan have revealed evidence of mass executions and human sacrifice over the past several years.

In a new research paper published today by PLoS One, archaeologists Gabriel Prieto of the National University of Trujillo, John Verano of Tulane University, and their colleagues consider the meaning of the HLL sacrifice, which is unique in both its scale and its composition. When it was first discovered in 2011, the HLL site immediately revealed a high number of child skeletons in unusual burial positions and with cuts to their breastbone, all within an area of 700 square meters.

The children were wrapped in plain cotton shrouds following their deaths, the archaeologists discovered, and many were buried in groups of three. Some children had their faces painted with red cinnabar, while others wore fabric headdresses. The llamas were placed on top of or next to the children. And trails of footprints of adults, children, and llamas dotted the site, pressed into a thick layer of fresh mud and preserved for nearly 600 years.

Laboratory analysis so far has determined that the boys and girls were in good health and ranged in age from 5 to 14, with a majority of them between 8-12 years old. About a dozen of the children had modified cranial vaults, a practice that indicated their association with a particular ethnic group within the Chimú civilization.

Examples of cranial modification among the children at HLL, Peru.Prieto et al. 2019 / PLOS / CC BY 4.0

What surprised the archaeologists was that “nearly all children with complete sternal elements showed a single transverse cut,” Prieto and colleagues write. “Many of the children had visible spreading and displacement of the ribs, indicating the chest was opened forcefully. Heart removal is a likely motivation.”

Little previous evidence has been found of human sacrifice in this region of Peru. However, old historical records by Spanish chroniclers may provide clues to its purpose. Friar Antonio de la Calancha, for example, claimed that child sacrifices were made by the Chimú during lunar eclipses and were sometimes made to sacred places or huacas. And in the 16th century, Cristóbal de Molina described Inca child sacrifice, writing that children “had their live hearts taken out, and so the priests offered the beating hearts to the huacas to which the sacrifice was made.”

Given the thick layer of mud that the graves of children and llamas were dug into, though, Prieto and colleagues suspect a catastrophic climate event may have precipitated the sacrifice. “It is probably associated with the El Niño-Southern Oscillation (ENSO) phenomenon,” they note, “that periodically brings coastal flooding and elevated sea temperatures that disrupt the marine food chain in northern and central Peru. It is possible that the sacrifices were made in response to the heavy rains.”

Bioarchaeologist Celeste Gagnon of Wagner College, who works at a nearby site in Peru, finds this hypothesis plausible. “Given that the Peruvian north coast is ground zero for ENSO,” she tells me, “the weather pattern would have decimated the marine resources that were so important to their lives. This may also be why at least one event of Moche sacrifice about 700 years earlier near Chan Chan also has ENSO mud evidence.” Matthew Piscitelli, an archaeologist at the Field Museum, concurs that Prieto and colleagues have made a compelling argument about the motivation for the sacrifice. He tells me that since the research “ties together so many lines of evidence–isotopic, genetic, osteological, zooarchaeological–it’s hard not to believe that this was how this prehistoric population reacted to the traumatic effects of ENSO.”

The trauma of the ancient climate events may therefore help explain the sacrifice. Piscitelli suggests that it may be difficult for us to imagine carrying out this sacrifice, “but you need to put yourself in their shoes. How would you react if the world as you know it was crumbling around you, with catastrophic flooding and searing droughts? Without meteorology, where would you turn? In this case, it might have been religion and a belief that only the ultimate sacrifice would appease what the Chimú thought were angry gods.”

But the discovery of this grim graveyard raises the question of another kind of trauma: the emotional effects it had on the archaeologists and may have on the public.

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