The exact date that American Indians first occupied the Americas is open to debate. Archaeological evidence suggests that sometime around 14,000 years ago or earlier, the ancestors of American Indians arrived on the North American continent. Archaeologists generally believe that American Indians migrated from northeast Asia across the Bering Straits land bridge, known as Beringia, between Siberia and Alaska during the late Pleistocene Epoch, or last Ice Age. Over the course of centuries, these new arrivals settled both the North and South American continents from Alaska to Tierra del Fuego on the tip of South America.
The first American Indians, called Paleo-Indians (paleo meaning ancient) by archaeologists, were hunters and gatherers. They hunted Pleistocene mega-fauna, or big game animals, such as mammoths, mastodons, giant bison, ancient horses, camels, and giant sloths. Although mammoths and other Pleistocene mammal skeletons have been discovered in the Salt River Valley, no Paleo-Indian remains have yet been recovered. However, several mammoth kill sites containing Paleo-Indian spear points have been excavated in southeastern Arizona.
With the end of the Pleistocene, a warmer climate resulted in mass extinctions of Ice Age megafauna. (Link to 68K file of adjacent image. Photo courtesy of National Museum of Anthropology, Mexico.) Noted paleobotanist Paul Martin has proposed that Paleo-Indians may have hunted the megafauna into extinction, but current data indicate major climatic changes had the greatest influence. With the disappearance of most of the megafauna, the Paleo-Indians were forced to hunt smaller game, which led to the development of a new American Indian culture archaeologists call the Archaic (meaning old).
Sometime around 9,000 years ago, Desert Archaic people lived throughout the American Southwest. These small bands of hunters and gatherers led a nomadic life, traveling from place to place with the seasons, searching out a variety of wild plants. About 3,000 years ago their way of life began dramatically to change as many Archaic peoples of the Southwest adopted an agricultural lifestyle and became more sedentary. As time went on and farming became more established, groups began developing differences in their material culture. Through these differences, cultures of the Southwest became more visibly distinct from one another.
Archaeologists have defined several prehistoric cultures in the Southwest. In the Four Corners area of Utah, Colorado, New Mexico and Arizona, groups known today as the Anasazi (prehistoric Pueblo) began constructing permanent hamlets and villages. The Mogollon people lived along the rim of the Colorado Plateau and the mountains of eastern Arizona and western New Mexico. The Patayan occupied the area along the Colorado River in western Arizona. Finally, the Hohokam, (pronounced ho-ho-KHAM), settled the region of central and southern Arizona.