Traces of alcohol and cocaine in the mummified remains of three Incan children provides revelations into how the South American empire performed ritual sacrifice, according to a new study in the journal PNAS.

Unearthed over a decade ago on the 22,000 foot peak of Mount Llullaillaco, the frozen bodies of a teenager and two young kids represent some of the best preserved mummies ever discovered. It is widely assumed that they children were sacrificed as part of religious ritual known as capacocha.

It was considered an honor to be chosen, as the spirits of sacrifices were believed to live among the Incan gods.

This study answers a few questions raised by the historical writings of Spanish conquistadors that arrived in the regions during the mid-1500s. They had written that sacrificial children consumed an alcoholic drink called "chicha" in preparation for the final stage of the ceremony, which involved being placed in underground chamber and freezing to death.

Capitalizing on the fact that compounds in alcohol are naturally incorporated into one's hair over time, the researchers were able to not only confirm this practice, but also found that the 13-year-old girl — known as the Llullaillaco Maiden — may have been heavily sedated when she was placed in her ceremonial chamber. This conclusion was supported by an X-ray tomography of the girl's body, suggesting she was intentionally sat upright, cross-legged, with her head slumping forward.

The Maiden's tightly braided hair, which allowed the scientists to backtrack nearly two years of her dietary history, was also analyzed to cocaine levels. Chewing coca leaves, from which cocaine is derived, was commonplace among the Inca.

Hair analysis revealed that the Maiden increased her coca habits right before her ceremony, with her consumption tripling within the last six months. Coca leaves were found in her mouth and stomach, the latter via X-rays. Her alcohol consumption also peaked during the final weeks of her life.

This is interesting because chewing coca leaves doesn't yield the typical signs addiction, according to the authors, although modest levels of cocaine and other organic compounds can be detected in the bloodstreams of habitual chewers.

The younger children had ingested alcohol and coca leaves too, albeit at a much lower level.

The findings paint an interesting picture of the final moments of the lives of the human sacrificial offerings, but also raise questions about Inca patterns of social control, according to the authors. It is possible that these drugs were used as a quasi-euthanasia/anesthesia to help numb the pain connected to sitting on the cold, mountainous ceremonial platform.

Source: Wilson AS, Brown EL, Villa C, et al. Archaeological, radiological, and biological evidence offer insight into Inca child sacrifice. PNAS. 2013.