The morphological evidence from Naia’s skull could be read two ways, and the two readings had very different implications.

Reading one: Naia and people like her represent an earlier founding population of the Americas, with distinct ancestry and physical features, who were subsequently replaced or absorbed by a second wave of migrants with different characteristics — the ancestors of most historical Native American peoples.

Under this reading, the gap between early American morphology and later Native American morphology reflects real population discontinuity.

Reading two: Naia and people like her were part of the same founding population as all later Native Americans, and the difference in skull morphology between early and later populations reflects changes that occurred within a single continuous population over time — changes driven by natural selection, genetic drift, dietary shifts, or developmental variation — rather than replacement by a new group of people.