Our knowledge of the Paleoindian period begins with evidence of Clovis mammoth hunters at the end of the Pleistocene. These people are believed to be of Asian origin having come to North America across the Bering Straight land bridge. The hunting of large game during a period of great environmental change is documented at kill sites where distinctive fluted points sometimes are found imbedded in the bones of now-extinct mammals. Some researchers hypothesize that the hunting of wooly mammoth by Paleoindians was one of the factors that hastened their eventual, albeit unavoidable, extinction. Paleoindian sites are found in caves or eroding from the banks of arroyos.
Documented sites are few in number but their distribution throughout the southwest is fairly broad.
Because the sites often are buried quite deeply their visible impact on the desert is low. The hunter-gatherers of the Archaic period left a more distinctive mark on the landscape. They subsisted on hunting small game and gathering a variety of plants. By the end of the Archaic period a number of cultigens, most notably corn, had been adopted from Mesoamerica. Features of the Archaic period still visible in the desert include trails, sleeping circles, and artifact scatters.