Scientists Discover a Rare Genome in an Incan Child Mummy

University of Cuyo Publisher (Argentina) via Salas et al. in Nature
University of Cuyo Publisher (Argentina) via Salas et al. in Nature / University of Cuyo Publisher (Argentina) via Salas et al. in Nature

The boy was only 7 years old when he died more than 500 years ago, chosen for his beauty and health to be sacrificed in an Incan ritual known as capacochain which children were ritualistically killed to mark an important occasion, prevent a natural disaster, or to exert imperial power and control over the then-expanding Incan empire (1438–1533). In 1985, a group of mountaineers discovered his well-preserved mummy more than 17,000 feet up at the edge of the Aconcagua Mountain in Mendoza, Argentina. It was wrapped in different textiles and surrounded by six statuettes. His hair nearly reached his shoulders, and he wore a necklace.

Now scientists have sequenced the child’s genome, and they’ve discovered that he was part of a rare group of people never before identified genetically. Their findings were published today in the journal Nature.

Antonio Salas, of the Universidade de Santiago de Compostela, and his colleagues sequenced the entire mitochondrial DNA genome extracted from the boy’s lung, then compared it against a worldwide database of approximately 28,000 mitochondrial genomes, which are passed down from mother to child. They say he belonged to a haplogroup called C1bi that has not been identified previously. (A haplogroup is population that shares a common ancestor.)

There are 203 C1b mitogenomes in the genetic record, dating back to the earliest Paleoindian settlements a little more than 18,000 years ago. The boy, however, appears to have been a descendant of a rare genetic sub-clade of maternal ancestors that lived about 14,300 years ago in Peru, the researchers say.

Based on a database of haplotypes, or DNA variations that tend to be inherited together, the authors say that genetic relatives of the boy in the C1bi haplogroup may live in Peru and Bolivia today; they found a few C1bi genetic matches for the child in these locations in the database, including one person who was a member of the Wari Empire (circa 600–1100), in the Peruvian Andes.

But we’d have to look closer for them in today's South Americans. “The fact that C1bi is very uncommon in present-day populations from South America could be explained by insufficient sampling of modern populations,” they write. “Alternatively, this rarity could reflect important changes in the gene pool of South America since the period of the Inca civilization.”