A rapid spread would be consistent with the hypothesis that people were moving through a landscape rich in naive megafauna — large game animals that had never encountered human hunters and were therefore relatively easy to hunt.

It would also be consistent with the growing body of archaeological evidence for pre-Clovis sites scattered across the Americas, which suggests that people were in multiple parts of the hemisphere at times that are difficult to reconcile with a slow, gradual southward movement.

The Spirit Cave Man’s genome also provided evidence about when certain major genetic splits within the Americas occurred.

The differentiation between broadly northern and broadly southern Native American populations appears, based on ancient genomic data, to have occurred at some point in the relatively early post-Beringian expansion — not thousands of years after the initial entry into the Americas, but within a few thousand years of the founding.