Paleo-Indian remains in the Chaco region are rare, due in part to the extensive and continuous re-occupation of the Canyon up to the present and to depositional and erosional patterns over millennia. Recent studies north and west of the canyon indicate a wide-spread and relatively continuous use of the San Juan Basin and greater Four Corners region during the late Pleistocene, from 8,000 to at least 10,000 years ago. People adapted to this period of climatic variability by developing a highly mobile hunting and gathering economy, a subsistence pattern that leaves little archaeological evidence. Unless these transitory sites contain diagnostic tools, particularly those used in specialized hunting/butchering activities, they are difficult to identify or date. No definitive dates or cultural remains from this period were discovered within the park during the initial surveys in the early 1970s, but recovered ‘isolated diagnostic tools suggest a Paleo-Indian presence in the canyon.