Why have such regional differences developed?
Although it is tempting to say that the differences among these three regional groups can be traced to environmental differences that determine the degree of certainty regarding the success of the basic means of livelihood, this would be to overlook other key influences. Yes, the use of intensive irrigation did play a role in the development of a more complex political system in the Eastern Tanoan Pueblos and among the Keresan Bridge Pueblos. There we find strong political control invested in the cacique and his council, including the powerful war captain who could revoke permission to live in the pueblo if a person refused to join communal work on the irrigation system. Such strict means of social control contrasted with gossip and avoidance practiced in the Western Pueblos, where smaller work groups based on clans and lineages provided enough manpower to practice dry and flood farming.

Despite the appeal of the irrigation hypothesis, other factors have clearly been operating. Ethnic and linguistic differences existed among the Western Pueblos, the Keresans, and the Eastern Tanoans long before the arrival of the Spaniards. The Zuni, who speak a language unrelated to any other known language in the world, are probably a mixture of Ancestral Pueblo (Anasazi) and Mogollon. Their language alone indicates considerable time depth as a separate people. The Uto-Aztecan proto-Hopi may have arrived in the Four Corners area early enough to participate in the Basketmaker-Anasazi transformation of the Desert Culture. The Keresan-speakers and the Tanoan-speakers also descended from the Ancestral Pueblo (Anasazi). Why did the Ancestral Pueblo peoples leave the Four Corners area to settle elsewhere? Archaeologists identify five stress factors, including raiding by more nomadic groups, inter-pueblo warfare and aggression, disease, the major drought that occurred on the Colorado Plateau between A.D. 1276 and 1299, and erosion of their farmland related to the lowering of the water table through drought. The harsh environment of the Southwest, an area that is marginal for agricultural, forced people to move constantly in search of better conditions. When they migrated, groups of different ethnic backgrounds-the Ancestral Puebloans were not a unified, single entity-and different beliefs and practices.

Warfare provides a third factor in the development of regional differences. Much more important among the Eastern Tanoans, raiding by nomadic Indians, including Apaches, Comanches, and Navajos, led to a greater emphasis on warfare. The Eastern Tanoans had war captains and Warriors' Associations, and the Pueblos were such superb warriors that the Spaniards, to combat nomadic tribes after the reconquest, even enlisted them to serve but allowed them to remain directly under their own captains of war.

There was also influence from other Indians, especially those of the southern Plains, on the people of the northern Tanoan pueblos through trade and other forms of peaceful exchange. As material items were exchanged, beliefs and practices were also borrowed.