New DNA Study Reveals Third Wave of South American Settlement

A massive new DNA study is rewriting the story of how humans first populated South America, and the findings could improve healthcare for millions.

Working directly with Indigenous communities across Argentina, Bolivia, Brazil, Colombia, Ecuador, Mexico, Paraguay and Peru, scientists created the most comprehensive genetic database of Indigenous Americans to date. They sequenced 128 new genomes from 45 ethnic groups and combined them with existing data to analyze 199 contemporary individuals from 53 populations.

The research revealed something unexpected: humans settled South America in three waves, not two. While scientists knew about migrations 15,000 and 9,000 years ago, this study uncovered a third wave starting around 1,300 years ago, when Indigenous groups from central and southern Mexico gradually moved into South America and the Caribbean.

But the migration story is just the beginning. The team discovered more than a million genetic variants that have never been found in other populations worldwide.

These unique variations likely developed as Indigenous peoples adapted to the diverse environments of the Americas over thousands of years. Understanding them could revolutionize medical research and create more equitable healthcare, since the same genetic mutation can affect people differently depending on their genetic background.

The Ripple Effect

This research addresses a major gap in global science. Genomic data has been heavily biased toward populations of European origin, meaning scientists haven't had a complete picture of human genetic variation.

The study also solved an ancient mystery: why some Indigenous South Americans share about 2 percent of their DNA with people from Australia, New Guinea and the Andaman Islands. These Australasian genes, dating back over 10,000 years, appear to have survived because they're beneficial, particularly genes related to fertility and immune response.

The research team found evidence of a genetic bottleneck caused by European colonization over the past 500 years. Today's Indigenous American genetic diversity represents only a fraction of what existed before Europeans arrived.

Study co-author Carlos Eduardo G. Amorim calls this "the most comprehensive view of Indigenous American genomic diversity and evolutionary history to date." One researcher not involved in the study agreed it's "a step forward," though not the end of the story.

The partnership between scientists and Indigenous communities shows how collaboration can unlock discoveries that benefit everyone.