The picture of the founding of the Americas that emerged in subsequent years — from additional ancient genomes, from improved demographic modeling methods, from the analysis of modern Native American genomes with greater depth and breadth than had been possible in 2018 — was more complex than the simple two-branch model suggested.

The founding of the Americas, it increasingly appeared, involved not just one split but multiple splits, at different times, producing a pattern of population differentiation that is still being mapped with growing precision.

The Northern And Southern Branches

One of the most important findings to emerge from the broader body of ancient American genomics — supported by the USR1 analysis and by subsequent research — was the identification of two major branches within the main Native American founding population: the ancestors of Indigenous peoples in northern North America and the ancestors of Indigenous peoples in southern North America and South America.

This north-south split was not a new idea in 2018, but the USR1 analysis contributed to its characterization and to the modeling of when it occurred.