Large study traces prehistoric human expansion into South America, where genomic studies have been lacking

A large-scale genomic study of over 1,500 individuals from 139 underrepresented Indigenous groups across northern Eurasia and the Americas sheds new light on the ancient migrations that shaped the genetic landscape of North and South America. The results reveal distinct ancestry patterns and early diversification of Indigenous South American populations. The late Pleistocene saw the migration of humans from North Asia into North and South America beginning by at least 23,000 years ago, according to archaeological evidence. This expansion was rapid – genetic evidence suggests northern and southern Native American groups began diverging between 17,500 and 14,600 years ago, with human presence in southernmost South America confirmed by 14,500 years ago. However, many questions remain about this expansion and its impact on the genetic architecture of human populations across the continents, especially in South America, where high-resolution genomic studies are still lacking.

To address this knowledge gap, Elena Gusareva and colleagues developed a comprehensive, high-resolution genomic dataset comprising over 1,500 individuals from 139 ethnic groups – many previously unstudied. This dataset, containing more than 50 million high-quality genetic variants, was analyzed alongside ancient and modern DNA from Native American populations. This helped the authors investigate deep patterns of population history, migration, and adaptation. Gusareva et al. found that Siberian populations trace their ancestry to six ancient lineages, with West Siberian heritage broadly shared across the region. A notable population decline around 10,000 years ago may have been driven by climate change and the loss of megafauna. Moreover, genetic and archaeological evidence suggests that Native Americans diverged from North Eurasians between 26,800 and 19,300 years ago, with west Beringian groups like the Inuit, Koryaks, and Luoravetlans being their closest living relatives. In South America, four distinct Indigenous lineages – Amazonians, Andeans, Chaco Amerindians, and Patagonians – rapidly emerged from a common Mesoamerican origin between 13,900 and 10,000 years ago. The four lineages largely reflect distinct geographical and environmental regions, such as the Andes Mountains, the arid lowlands of the Dry Chaco, the humid tropical rainforests of the Amazon Basin, and the frigid polar climate of Patagonia. According to the authors, rapid geographic isolation of these groups likely reduced genetic diversity, particularly in immune-related HLA genes, which may influence susceptibility to infectious diseases.