One branch led to the Ancient Beringians — the lineage represented by USR1, which remained in or near the Beringian region.

The other branch gave rise to what the paper called the “First Americans” — the ancestral population of most contemporary and ancient Native Americans sampled, which expanded southward as the ice retreated.

Third, the model placed the divergence between these two branches at approximately 20,000 years before the present — consistent with the standstill period, before the southward expansion of the First American branch began.

This model was not derived from the USR1 genome alone.