Prehistoric Water Wells on the Southern High Plains: Clues to Altithermal Climate

Abstract

Prehistoric water wells were recently discovered at the Mustang Springs site (41 MT 2), along Mustang Draw on the southern Llano Estacado in west Texas. Associated radiocarbon and thermoluminescence dates indicate these features were dug approximately 5000 b.p. (radiocarbon years). The dates help bracket the age of well-digging on the southern High Plains, which is known from only two other sites: Blackwater Locality No.1 and Rattlesnake Draw, both in New Mexico. The presence of water wells, along with stratigraphic and sedimentological evidence, indicates a period of lowered water tables and extreme aridity, perhaps the regional manifestation of the Altithermal climatic stage. This episode of climatic stress must have had a significant impact on human adaptation to the southern High Plains during the middle Holocene, particularly given its effects on bison populations, the animal species on which the human groups depended. Bison populations appear to have been greatly reduced at this time, as a consequence of a lack of available water and a reduction of surface vegetation—evidenced respectively by these water wells and carbon isotope ratios in fossil bison remains.While these middle-Holocene water wells are morphologically almost identical to those being dug on the southern High Plains by native American groups in the late 19th century, the analogy extends no further. In the more ancient instance, well-digging represents an adaptive response to protracted aridity; in the other, a tactical response to warfare on the southern High Plains.