The analysis showed that USR1 did not cluster with either the Northern Native American or Southern Native American population branches that together account for the ancestry of the vast majority of later Native Americans.

Instead, USR1 clustered in a position that suggested separation from these branches at an early stage — a deep divergence that the researchers interpreted as reflecting the existence of a third founding lineage, one that had not been previously documented in the genetic record.

The discovery of Ancient Beringian ancestry in USR1 was important because it revealed previously unknown complexity in the founding population history of the Americas.

Rather than a simple model in which a single founding population entered the Americas and then differentiated into Northern and Southern branches, the ancient-genome evidence suggested at least three branches: the Northern Native Americans, the Southern Native Americans, and the Ancient Beringians — a deeper lineage that had separated earlier in Beringian prehistory.