The children, who were found in 1999 near the summit of the Llullaillaco volcano in Argentina, probably died about 500 years ago in a sacrificial ritual known as capacocha. In the study, published today in Proceedings of the National Academy of Sciences, researchers led by archaeologist Timothy Taylor of the University of Bradford, UK, used mass spectrometry to analyse variations in levels of chemical residues in the children’s hair in the months before their deaths.

The researchers looked for by-products of the metabolization of coca and alcohol — both important in Andean culture and ritual — and found that all three children ingested both substances in the year before they died. But the eldest — a 13-year-old girl known as the Maiden — took much more of both substances than the younger children. The pattern of consumption suggests that a series of rituals preparing her for her fate began about a year before she was left to die on top of the 6,739-metre-high Llullaillaco.

The levels of metabolites in her hair, for instance, increased about a year before her death and then shot up to very high levels about a month and a half before she died — her hair recorded the highest level of coca ever found in Andean archaeological remains, says John Verano, a biological anthropologist at Tulane University in New Orleans, Louisiana.

“In the final stages of her life, we see a use of alcohol far beyond any exposure which she’d been used to, and a concurrent use of alcohol and coca that was very likely a means of sedating her,” says Andrew Wilson, a forensic scientist and archaeologist at the University of Bradford, and a co-author of the paper published today.