Tree lines in the Rockies moved upslope during the early Holocene warm period — the upper limit of tree growth extended higher than it does today in many mountain ranges.

This would have affected the character of the terrain around Hourglass Cave: what today might be rocky alpine terrain near the cave entrance might have had some scattered tree growth during the early Holocene, modifying the visual landscape and the available resources.

The early Holocene was also the period when the great Pleistocene megafauna extinctions were completing their course in North America.

The mammoths and mastodons — the largest animals of the late Pleistocene — were extinct by approximately 10,000 years before the Hourglass Cave man was alive, or had been reduced to isolated relict populations in specific refugia.