Children selected for Inca ritual sacrifice were "fattened up" with high-protein diets in the months leading up to their deaths, a new study has found.
Researcher Andrew Wilson and his team conducted DNA and chemical tests of hair samples taken from four child mummies found in the Andes mountains in the 1990s.
By studying the ratios of chemicals present in the hair, the team helped show how victims were prepared for death as far as a year in advance, sent on grueling highland journeys, and drugged before the sacrificial ceremonies.
"The findings offer insights into the preparatory stages leading to Inca ritual killing, as represented by the unique capacocha rite," the report reads, referring to the Inca tradition of mountaintop child sacrifice.
Hair logs a chemical record of what an individual consumes, and the information can stay intact in archaeological remains, the study authors point out.
"It is chilling that the children themselves, through their own tissue, give us graphic details and evidence that they were not killed on a whim but were part of a complex process for which they were selected some considerable time before," said Wilson, a lecturer in archaeological sciences at the University of Bradford in Britain.
The study appears online this week in the Proceedings of the National Academy of Sciences and was funded by the U.K. charity the Wellcome Trust.
"Fattened Up" and Drugged
One extremely well preserved mummy—a 15-year-old girl known as "La Doncella" or the "Llullaillaco Maiden"—appears to have been selected for sacrifice a year in advance, Wilson said.
She and two of the other mummies in the new study were discovered in 1999 by a National Geographic Society expedition led by anthropologist Johan Reinhard. (The National Geographic Society owns National Geographic News.)
Tests show the Maiden—whose hair was 9.8 inches (25 centimeters) long, representing more than two years' worth of growth—was raised mostly on a protein-poor "peasant diet" rich in potatoes.
"But 12 months before her death, her diet becomes protein rich," Wilson said, adding that she was likely fed "elite" food such as maize and llama meat.
"We can equate a change in diet of this magnitude with a change in her status, one that occurred as part of her final demise."
But the term "fattening up" is used as an illustration, not necessarily a direct reference to weight gain, he said.
"The tissue on the Maiden's forearm is plump, for example," he said. "This is an illustration that these individuals were in good health and condition."
What's more, the chemical evidence shows another shift several months before death, indicating that the children were forced on a grueling pilgrimage.
The route likely went from Cusco, Peru—the Inca capital—to high-altitude mountain shrines, where the children were drugged and then killed or left to die, Wilson added.
The Maiden, for example, was fed fermented maize beer and chewed coca leaves before her death.
Last Months of Life
"This work gives a very interesting and intimate picture of the last months before the deaths of the individuals involved in the capacocha ceremonies," said Kelly J. Knudson, a bioarchaeologist at Arizona State University.
Sonia Guillén, a Peruvian archaeologist, said the study was interesting and helps confirm much of what is known about this type of sacrifice.
"One key question is how these children differed from others in terms of diet," she said.
Other capacocha victims have been found, and other studies have looked at isotopic signatures in order to measure seasonal variations in diet, study leader Wilson said.
But none "has linked to such a graphic piece of evidence that would suggest a diet shift of this magnitude that could be equated with change in status."
Study co-author Timothy Taylor, also from the University of Bradford, said in a written statement that "the treatment of such peasant children may have served to instill fear and exert social control over remote mountain areas newly incorporated into the empire."