More than 500 years ago, three children climbed Llullaillaco volcano in Argentina and never came down, the probable victims of human sacrifice. Since their well-preserved mummies were discovered in 1999, scientists have studied them in hopes of reconstructing the last months of their lives. New evidence shows that all three regularly ingested coca and alcohol and suggests that the drugs might have played a more-than-ceremonial role in their deaths.

The children—a young boy and girl, and a female archaeologists call the Llullaillaco Maiden, whom new research estimates to have been 13 years old—were part of an Incan sacrificial ritual known as capacocha, in which children were killed or left to die from exposure at the peaks of high mountains. Found sitting within small shrines, the bodies were naturally mummified by the cold, dry climate of the nearly 7000-meter mountain.

Most of what scientists know about the lives of the Llullaillaco mummies comes from their hair. The Maiden, in particular, has long, tightly braided locks that had been growing for at least 2 years before her death. In 2007, scientists analyzed the carbon and nitrogen isotopes found in her tresses and detected a marked change in her diet about 1 year before she died, when she went from eating mostly potatoes to consuming more animal protein and maize.

This time, the team didn't stop with food. “Anything that circulates in the blood will eventually end up in the hair”—including signs that an individual consumed drugs like alcohol and coca, the plant processed to make cocaine, explains Angelique Corthals, a forensic anthropologist at the Stony Brook University School of Medicine in New York, who was not involved in the study. When scientists measured the levels of a few key metabolites along strands of the Maiden's hair, they saw that her consumption of coca and alcohol began to increase around the same time that her diet changed, they report online today in the Proceedings of the National Academy of Sciences. Her coca use peaked about 6 months before she died, while her alcohol consumption skyrocketed in her final weeks. The boy and the girl, both of whom were 4 to 5 years old and had shorter, less kempt hair, also ingested the two drugs but in much smaller amounts than the Maiden.

By analyzing the Maiden's hair, “we’re starting to see a picture … of an emerging sequence of events that culminated in her sacrifice,” says Andrew Wilson, an archaeologist at the University of Bradford in the United Kingdom who led both studies. He suspects that her initial change in diet and drug consumption likely coincided with her selection as an aclla. In Incan culture, these “chosen women” were “selected to live apart from their families at around the age of puberty, probably under the guardianship of priestesses,” he explains. Significantly, acllas were trained to produce chicha, a fermented maize drink that was probably the Maiden's principal source of alcohol. Meanwhile, coca was—and in some Andean cultures, remains—a “revered” ritual substance, Wilson explains. Indeed, radiological scans reveal coca leaves clenched in the teeth of the Maiden’s mummy, suggesting that she was chewing them when she died.

The importance of coca and alcohol in capacocha rites “is something that we hypothesized for a long time, and it’s really, really nice to see it confirmed,” says Corthals, who has studied the mummies in the past. But the drugs’ role in the sacrifices may have gone beyond ritual.

Capacohca rites were complicated religious and political ceremonies that may have been partially intended to instill fear in communities recently conquered by the Incan empire. Although historical sources report that being selected as a capacocha sacrifice was considered an honor, Wilson wonders if the alcohol may have been used to sedate the Maiden in the weeks leading up to her death. What’s more, alcohol impairs the shivering reflex, so if she was left to die of exposure drinking could have hastened her death. But the presence of coca complicates that picture somewhat, because it can slightly increase body temperature by causing the blood vessels to constrict.

Although it’s still not clear how the combination of drugs may have affected the bodies and minds of the Llullaillaco Maiden and children on the mountaintop, Wilson suspects that the Maiden, at least, was likely heavily sedated and placed in the shrine and left to die of exposure. While other high-altitude Incan mummies show signs of head trauma, the Llullaillaco mummies appear to have died peacefully. There were “no outward signs of fear” such as vomiting or defecation in the Maiden’s shrine, Wilson says, and the fact that she was found sitting in a cross-legged position surrounded by intact offerings suggests that she didn’t struggle once inside. Still, it’s possible that her body was arranged in that position just after death, implying that a more deliberate act, like suffocation or poisoning, might have taken her life before the harsh environment of the mountain had a chance to do its work.