Seasonal changes in the local availability of wild foods must have necessitated a nomadic or seminomadic way of life. The development of agricultural techniques in the later years before the beginning of the Christian Era, however, probably contributed to the development of a semisedentary existence that was eventually to lead to the village life of the later periods. The exact time of introduction of the principal agricultural crops, corn, squash, and beans, is unknown, but evidence from west-central New Mexico indicates their use by the Cochise people by 2500 B.C. PUEBLOAN FARMERS Having acquired the techniques of deliberately planting and raising food crops that could be stored against future needs, local populations of Hunters and Gatherers became less dependent upon the gathering of wild foods and began to construct clusters of more permanent dwellings near cultivable land. Among the earliest recognized houses of this period are the semisubterranean pit houses of the early Mogollon people in the San Francisco River drainage of west-central New Mexico (fig. 4) and of the Anasazi Basketmakers in the San Juan River drainage of northwestern New Mexico. These cultural advances, together with the acquisition of techniques for the manufacture of fired pottery, foreshadowed the development of the Mogollon and Pueblo cultures at a time beginning perhaps as early as 300 B.C. for the Mogollon area and at least by 1 A.D. for the Anasazi area. [Illustration: Figure 3. Milling stones of the type used by the Cochise People Plant foods were ground in a shallow basin metate with the small one-hand mano (hand stone). Socorro, New Mexico.]