Science http://doi.org/cwws (2018)

The timing and origins of the first arrival of humans in the Americas has been much debated, but less attention has been paid to the internal movements of people once they arrived.

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Oleksiy Maksymenko Photography/Alamy Stock Photo

A study by Víctor Moreno-Mayar, of the Natural History Museum of Denmark, and colleagues aimed to improve this picture by sequencing DNA from 15 ancient humans along a latitudinal gradient across the American continents. The results show that humans arrived in eastern Beringia and experienced several population splits in northern North America 25,000 to 15,000 years ago. After this, human migrations followed a complex history of an initial rapid, southward, cross-continental radiation 14,000 years ago, followed by dispersals and intermixing with pre-existing populations after 8,000 years ago, including a later re-radiation of Mesoamerican populations into the north and south. There is also evidence for Australasian genetic ancestry in a 10,000-year-old South American individual, which hints at a more widespread, earlier-arriving population. These processes gave rise to population continuity in some regions, and replacement and admixture in others.

This ancient genetic evidence begins to provide a more nuanced population history of the Americas and helps to reveal ancestral and cultural congruence and divergences.