Within a single founding population that was small, mobile, and geographically diverse, skull shapes could vary considerably through genetic drift.

Adaptations to different environments — different diets, different climates, different levels of physical activity — could produce measurable changes in skull shape within just a few thousand years.

The morphological differences between the Spirit Cave Man and later Native American populations were consistent with normal within-population evolution across ten thousand years, not with the replacement of one group by another.

The DNA proved this definitively.

And in doing so, it resolved a debate that had been generating heat — and sometimes misleading implications about Indigenous ancestry and rights — for more than a decade.