Sorting out the relative contributions of these factors will require additional data and refined analytical methods.

But the hypothesis that the morphological variation reflected a separate founding group — a group that was replaced or absorbed by the ancestors of modern Native Americans — is no longer supported by the available evidence.

It has been tested against the genomic data and found wanting.

The Spirit Cave Man was among the most important tests.

His skull was one of the morphologically distinctive early American specimens that the Paleoamerican hypothesis was designed to explain.

His genome showed that no separate explanation was necessary: he was Native American in the fullest genetic sense, part of the same founding population that gave rise to all the Indigenous peoples of the hemisphere.