The people who entered the Americas through the Bering region had their own internal diversity, their own geographic substructures, and their own range of physical variation.

As that population spread across the hemisphere and adapted to enormously varied environments, its internal diversity expressed itself in different ways in different regions.

The skull shapes that some researchers had interpreted as evidence of separate founding events may reflect this initial diversity, expressed more fully in some regions and at some time periods than in others, and subsequently reduced in later populations through the specific processes of adaptation and genetic drift that affected populations after the founding.

This is a more complex picture than either the simple Clovis-first model or the simple two-migration model offers, and it is a picture that is still being refined.