Some scholars date the origin of native cultures in the southwestern United States to immigrants who crossed the Bering land bridge from Siberia to Alaska, approximately 10,000 B.C. Others maintain that native cultures came to the Americas as early as 25,000 B.C. These immigrants settled in what is present-day southern Utah and Colorado, Arizona, New Mexico and northern Mexico. This culture area is contiguous with the Far West Culture, the Plains Culture (to the northeast) and the southern part of the Eastern Woodland Culture. The Southwest's climate is generally hot and arid. Much of the land is desert dotted with cacti and other water-miser plants. Some areas are characterized by plateaus, spectacular rock formations and mineral wealth. There are forests at higher elevations. The land is graced by a few green river valleys; summer rains in some areas allowed farming by peoples of remote times. Three significant cultures emerged in the region around 300 B.C. All three were based on a farming society augmented by hunting and gathering. They included the Anasazi, who erected cliff houses in northern Arizona and New Mexico, Utah and Colorado; the Hohokam, who dug complex irrigation systems in central Arizona; and the Mogollon, who hunted and farmed along the rivers of western New Mexico and eastern Arizona. Water was a precious natural resource in Southwestern societies, which kept strict rules about its use down to the youngest child. Some argue that these cultures were the most sophisticated of any Native American society north of present-day Mexico during the first 1,200 years A.D. Early ways of life had changed by the time the Spanish arrived around 1600 A.D. The Southwest natives survived this contact, unlike the Mayan and Aztecan cultures in Mexico that were leveled by the Spanish. In some ways, the latter's influence actually enhanced Southwest cultures for a time. Introduced tools, plants, horses and sheep exerted a positive impact on native cultures. Spaniards and later Europeans encountered three subsistence types in the Southwest: villagers, farmers and nomads as well as a mixture of the three. Villagers were descended mainly from the Anasazi. They were dubbed Pueblo (village) by the Spanish. The Pueblo subsisted by farming. They erected imposing terraced houses of adobe (dried clay), which sometimes rose to five stories. The Pueblo raised maize, squash and beans. They also raised cotton and wove it. The men wore breechcloths and blankets and the women wore blanket dresses. When the Spaniards introduced sheep to the area, the Pueblo women began to weave woolen clothing. The Zuni people lived in the area now known as western New Mexico and eastern Arizona. For hundreds of years, the Zuni were farmers and traders. The oldest continuously inhabited village in the United States is the Hopi community of Old Oraibi, located on a mesa in northern Arizona. This village came into being around 1050 A.D. when the Hopi migrated to this area. South of the Pueblo, other natives lived off the land. These groups include the Mojave and Yuma of the Colorado and Gila river valleys, the Pima of the southwestern Arizona desert, and the Yaqui, whose cultural roots are in Mexico. Some of these peoples were probably descended from the Hohokam of earlier times. The Mojave grew melons, pumpkin and maize, and built large houses with grass roofs covered by mud. Around 3,000 Yuma lived in the Southwest in the late 1600s. The Yuma were productive farmers in spite of the hot climate. The Pima were accomplished farmers and capitalized on the Hohokams' already large irrigation system with dams, reservoirs and some 200 miles of irrigation ditches. They developed drought-resistant maize and managed to cultivate several crops a year to barter and store. The third group included the Navajo, Apache and Hopi, among others. They probably migrated from the northwest about a millennium ago, well after other Southwestern natives had settled. When these nomadic tribes arrived, they lived by hunting. Then the Navajo settled near the Pueblo and learned to raise maize and weave cotton. After the Spaniards brought horses and sheep, the Navajo lived by raising sheep, weaving colorfully attractive blankets and crafting fine silver jewelry. They lived in a hogan, or earth lodge. The warlike Apache did not settle down. They preferred hunting and raiding; few of them raised crops. Some lived in brush huts and others lived in tipis like the Plains natives. Most of them dressed in animal skins. There were several language groups prior to European contact. They included Kerasan and Tanoan, languages of the Pueblo; Navajo, from the Athapascan linguistic family traceable to Northern Canada and Alaska; Yuman, spoken by the Havasupai and Mojave; Zuni Pueblo; and sign language, shared among the several tribes to overcome language barriers. Following European contact, the indigenous peoples acquired Spanish, English and a trader language (with whites) whose purpose was similar to sign language. In all, more than 600 native dialects were spoken among a dozen major tribes and their sub-groups. The people of the Southwest supported full-time religious leaders with shrines or temples. Most Southwestern Native Americans believed that in the universe there exists an Almighty, a formless spiritual force that is the source of all life. The sun was venerated as the power of the Almighty. They did not worship the sun, but prayed to the Almighty; the sun was its symbol. Some Southwest Native Americans believed the first people were created in a cavern below the surface of the earth. They climbed through two more caves, occupied by other living things, until they reached the surface. They emerged through a hole called sipapu, from which humans were born. They believed that this fourth world was sacred. Children listened to their parents tell legends, which recounted how people and nature work together. Catholicism was introduced by the Spanish. White contact from the 1600s onward was greedy, ruthless and marginalizing. In addition, the legacy of the Southwest Native Americans following 1845 is marred by promises made and undone by the federal government. Title rights to this region's water and mineral resources lay at the root of the confrontation between native and white cultures. In the long run, native societies were restricted to increasingly smaller reservations—most lacking access to traditional natural resources. Modern descendants of these tribes are noted for their symbol-rich spirituality, reverence for the earth, tightly knit clans, rousing dance and exquisitely rendered crafts. Water and mineral rights are an abiding concern and source of contention with the far more numerous non-natives of the Southwest.