Site preservation at this age is poor in most environments — most organic material has decomposed, most surface sites have been buried or eroded away, and the specific conditions that allowed the White Sands footprints to survive simply did not apply to most of the landscape.

The scarcity of sites from the Last Glacial Maximum may reflect a genuine scarcity of people, but it may also reflect the destruction of the evidence by time and geology.

White Sands survived because of a specific combination of circumstances — fine-grained lakebed sediment, rapid burial, low-energy erosion re-exposing the surfaces — that allowed traces from this period to persist.

Most comparable traces are gone.

The absence of evidence is not, in this case, evidence of absence.

It is evidence of the specific processes of preservation and destruction that operate over twenty thousand years.