In the summer of 1985, mountaineers discovered a partially unearthed, frozen mummy at an altitude of 5,300 meters (17,400 feet) on the southwestern edge of Cerro Aconcagua at the base of Pirámide Mountain in the Argentinean province of Mendoza. It was a seven-year-old boy wrapped in numerous textiles and surrounded by six statuettes – the victim of an Inca sacrifice ritual called "capacocha" more than 500 years ago, during the empire’s expansion towards the southern cone of South America.
The mummy’s entire mitochondrial genome (or mitogenome) has now been sequenced, and it’s presented in Scientific Reports this week. The child belonged to a genetic lineage that has never been identified in modern Native Americans before.
The Inca constituted the largest civilization in pre-Columbian America. They arose in the Peruvian highlands in the early 13th century, and beginning in 1438, they conquered or peacefully assimilated present-day Peru and portions of Ecuador, Bolivia, Colombia, Argentina, and Chile. The child mummy dates back to this period of southward expansion; it was found at the southernmost edge of the Inca Empire. The ritual sacrifice of children in honor of the gods was performed during or after important events such as a battle victory or in response to natural catastrophes like earthquakes. The last Inca emperor, Atahuallpa, was executed in 1533 by Spanish soldiers, bringing an end to the 300-year-old civilization.
To sequence the entire (maternally inherited) mitogenome of the Aconcagua mummy, Antonio Salas from Universidade de Santiago de Compostela in Spain and colleagues extracted DNA from a 350-miligram piece of the mummy’s dissected lung.
After comparing their results with a worldwide database of about 28,000 mitogenomes, the team found that the Inca mummy belonged to a new haplogroup (or a group of people who share a common ancestor) called C1bi that hadn’t previously been identified. The "i" is for Inca, and it branched off from the root C1b lineage, one of the most typical Native American haplogroups. C1b arose about 18,300 years ago.
Then, using a database of haplotypes (a set of DNA variations that tend to be inherited together), the researchers discovered that a few C1bi members may be living in Peru and Bolivia today. The team also identified an individual from the ancient Wari Empire of the Peruvian Andes as a member of this group.
The Inca child mummy represents a very rare sub-lineage that arose around 14,300 years ago in the Andean side of South America, likely Peru. Although C1bi is very uncommon in South American populations today, it could have been more frequent in the past.
Image in the text: The photo of the Aconcagua mummy is reproduced with the permission of the University of Cuyo Publisher (Argentina). Gómez-Carballa et al., Scientific Reports 2015
