The cultural trajectory of Lower Pecos prehistory originates in stereotypic Paleoindian big game hunters who apparently entered the region some twelve thousand to fourteen thousand years ago. Based on the two known sites of this age, the economy was oriented toward the procurement of megafauna such as elephants, camels, horses, and bison, although the earliest kills were probably individuals or pairs of animals that were trapped and slain (Bement 1986). The later Folsom and Plainview hunters had apparently perfected the jump technique of bison hunting, suggesting organizational skills consistent with group procurement strategies that centered upon migratory herd animals (Dibble 1970). The extinction of the large game herds and the onset of a trend toward aridity triggered a transition to Archaic lifeways about ninety-four hundred years ago. The people apparently exploited a broader resource base, developing a reliance on plant products, both as food and as raw material for the burgeoning fiber industry, while retaining established lithic traditions. The transition culminated in a robust adaptation that gives the outward but perhaps misleading impression of great stability for a period of some four thousand years. Rockshelters became the nucleus of the settlement pattern, showing differentiated activity areas of a domestic nature where fiber, wood, bone, and hide were worked, as was the everpresent stone. Mortuary customs included disposal of the dead in convenient vertical shaft caves regardless of age or gender. Then, about fifty-five hundred years ago, the cultural system began a series of internal adjustments, presumably in response to an increasingly arid environment. The end result was the consolidation of traits into the full-blown Archaic expression that defines the Lower Pecos as a distinct cultural entity. A model that parsimoniously explains this development was formulated by analogy to emerging complex societies documented ethnohistorically and archeologically in arid lands around the world. In this model, changes in the distribution of essential resources, most prominently potable water, triggered responses in the settlement pattern and procurement strategies leading to a disproportionate concentration of people along the major rivers. Aridity does not imply a shortage of food, especially if desert succulents increase at the expense of grasslands, but gathering and processing of thorny plant foods and small mammals requires specialized techniques and knowledge. The responsibility for food procurement, especially hunting and gathering in the uplands, would have been delegated to mobile task groups who operated from their bases on the rivers. Diversification broadened the diet to include labor-intensive processing of a wider range of foodstuffs, activities that took place in open camps and rockshelters as well. New methods of social control were mandated by the redistribution of human populations, who were in effect circumscribed by the availability of water. The inevitable tensions introduced by proximity elicited a restructuring of society that was accompanied by the intensification of ritual that was, in turn, manifested by the florescence of publicly produced mural art. A common belief system, rooted in the principles of shamanism and expressed in cave paintings, held sway over the area that is now defined as the Lower Pecos cultural region. This period of time is the apogee of the Lower Pecos cultural trajectory: the consolidation of an ethnic identity that trembled on the verge of societal complexity that was never achieved, possibly for lack of the ability to generate an adequate surplus- the necessary and sufficient condition for sedentism. Sometime around three thousand years ago, the insular Lower Pecos cultural persona relaxed, perhaps disrupted by the advent of new people with a different economic strategy and social structure. A mesic interlude permitted the grasslands of the Great Plains to expand to the Rio Grande, drawing herds of bison and their attendant hunters. Even episodic, perhaps seasonal, influxes of people bearing a fully developed cultural system of their own must have had a perceptible effect on the resident population; at present it can only be discerned in settlement patterns, tool types, and possibly art styles. The return to aridity and the retreat of the grasslands created a vacuum filled by desert-adapted people who came north across the Rio Grande from northern Mexico. Soon, the archeology of the Lower Pecos found affinities with that of central Texas, sharing in the generalized Late Archaic lithic assemblage while perfecting its fiber industry, retaining its characteristic burial customs, and keeping a balance between rockshelters and open camp site occupations. Measures of population density again rise, reaching and exceeding the heights achieved during the Middle Archaic peak, but the processes behind the increase are less clear. The Late Prehistoric period experienced a cultural upheaval, including changes in settlement patterns, site types, mortuary customs, art styles, and artifact types. Pictograph styles show affinities with northern Mexico and the Big Bend region of Texas, lithic tool types are shared with the rest of Texas, and mortuary customs appear to be introduced from the north and northwest. Clearly, people, rather than ideas, were on the move. Late in prehistory, one intrusive group is identified by a distinctive artifact assemblage, including small arrow points and ceramics, a preference for promontories with sweeping views, and residences that used paired stones as pole supports for a thatch or hide cover. The people of the Infierno phase may be precursors to ethnohistorically described bison hunters who again seasonally congregated at the mouth of the Pecos River during yet another mesic interlude. The Spanish found little of value in the Lower Pecos, isolating it as part of the great uninhabitable desert of their northern frontier, but native peoples found refuge in the rugged terrain. Indigenous groups were soon replaced by Apaches who, in turn, were driven south by the Comanches where they sometimes joined the Kickapoos, staunch allies of the Mexicans, in resisting their common enemy. Under American hegemony, a concerted effort to clear the way west resulted in the extirpation of native people by the time the second transcontinental railroad was completed in 1882.