Under this reading, there is biological continuity between the earliest Americans and all subsequent Native peoples.

These two interpretations could not be distinguished from morphological evidence alone, because skull shape is influenced by many factors — genetics, environment, diet, developmental history — and the relationship between skull shape and population ancestry is complex and not fully understood.

Two populations that are genetically closely related can have different skull shapes if they have adapted to different environments or developed different dietary practices over generations.

Two populations that are genetically quite different can have overlapping skull shapes if natural selection has favored similar traits in both.