Hourglass Cave is unusual for the Colorado Rockies, but it is not entirely unique in the context of cave use by early Americans.

Archaeological evidence of prehistoric cave use — for habitation, for resource extraction, for ceremony, for burial, and for other purposes — extends across North America and South America and goes back to the earliest period of human presence in the hemisphere.

In the American Southwest and the adjacent Great Basin, caves have been archaeological treasure troves.

The same arid conditions that characterize much of the region — low humidity, stable temperatures in cave interiors, limited biological activity — favor the preservation of organic materials that would decompose rapidly in more humid environments.

Spirit Cave in Nevada, discussed elsewhere in this series, is one example of the extraordinary preservation that Great Basin cave environments can provide.