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Although indigenous communities still thrive in Americas, no living human seems to carry any of the ancestral DNA documented in Llamas’ study, which was published in the journal Science Advances. While that doesn’t necessarily mean that the genetic diversity of the pre-Columbian era has been completely wiped out – other lineages not traced in this study may exist, and it’s still possible that the 84 lineages live on in a population that hasn’t been sampled yet. But the find demonstrates what the researchers bluntly term the “high extinction rate” for indigenous American people.

Reconstructed a complicated narrative spanning 23,000 years and three entire continents

But that sobering statistic is just the end of the story of humans in the pre-Columbian Americas. From their analysis of ancient genetic material, Llamas and his colleagues reconstructed a complicated narrative spanning 23,000 years and three entire continents.

They started by sampling 92 skeletons and mummified bodies whose owners lived somewhere in South America between 8600 and 500 years ago for what’s called mitochondrial DNA – compressed loops of genetic material that exist inside the hundreds of tiny structures that power each human cell. Every human inherits this material exclusively from his or her mother, so it’s a good way of tracing matrilineal lines of kinship back through time.

MtDNA is also useful for figuring out the relationships between populations, and measuring how they evolved. Since scientists know roughly how many mutations genetic material is likely to accumulate over the course of a given number of years, they can tally up the differences in mtDNA between two groups and derive from that the number of years it’s been since they were last in contact.