Dramatic changes

The time period from A.D. 1200 to 1540 has been long known as a period of dramatic change in the American Southwest. Deterioration of environmental conditions on the Colorado Plateau during the late 1200s led to widespread abandonment of settlements in the Four Corners area. This exodus and related migrations ushered in a period of widespread demographic upheaval. By the early 1500s many transformations had taken place across the Southwest, and the movement of Spanish soldiers and Catholic missionaries into northwestern New Spain was about to initiate even greater processes of change.

What happened to the Hohokam?

In 2004, Center archaeologists began work on research to more precisely model the population collapse that occurred in the Hohokam region of southern Arizona between A.D. 1300 and 1450. This process resulted in the disappearance of 40,000 people from the area nearly a century before the introduction of European diseases.

Results from earlier research in the San Pedro River Valley indicate that population reduction occurred gradually, and was a complex process associated with the long distance migration of groups from northern Arizona as well as the aggregation of local groups already settled in southern Arizona. After a century of gradual population loss, social boundaries slowly dissolved as groups tried to maintain irrigation systems and exchange networks. By A.D. 1450, most of the valley's remaining population, comprised by descendants of both local and immigrant groups, left the region.

Study of Existing Archaeological Collections.

In light of new insights gained from the San Pedro research, including advances in chronological control, Center researchers are reexamining artifacts from a number of Classic period sites in the Phoenix, Tonto, and Safford basins, and Perry Mesa, in order to better understand the processes of demographic decline and coalescence in other areas of the southern Southwest. Research is focused on collections curated at the Pueblo Grande Museum, Archaeological Research Institute, Western Archeological and Conservation Center, and Arizona State Museum.

The Big Picture.

The power of modern computer technology is key to this research project, especially the ability to manage and manipulate large amounts of related information via a Geographic Information System database. The Coalescent Communities GIS Database was created by the Center for Desert Archaeology, Museum of Northern Arizona, and Geo-Map, Inc. to give researchers a firm empirical grasp on demographic change in the Southwest. The Coalescent Communities Database now includes information on more than 3,900 prehistoric sites from throughout the Southwest. The ultimate goal is to compile size, temporal, and location data for every settlement in the Southwest with more than 12 rooms dating between A.D. 1200 and 1700.

This research is made possible by grants from the National Science Foundation, the Arizona Heritage Fund, and by gifts from private foundations and individuals.