What We Do: Investigations

HOMES OF THE FIRST TUCSONANS

These are currently the oldest known pithouses in the Tucson Basin, just south of Congress Street. This excavation is part of the Rio Nuevo Project.

These are the oulines of early agricultural period pithouses in the Tucson Basin, just south of Congress Street.

Early Agriculture Across the Southwest

David A. Gregory, Preservation Archaeologist
Fred Nials, Consulting Geologist
William Doelle, Archaeology Southwest Founder, President & CEO

Maize was first domesticated in central Mexico. Recent research in Arizona and New Mexico provides strong evidence for the arrival of maize agriculture in this region slightly more than 4,000 years ago. Together with other researchers, we have developed a broad regional model to help identify environmental settings with a high probability of preserving evidence of early farming activities. This model is focused on general conditions of river floodplains, and its basic premises are as follows:

All arid lands streams are punctuated by locations where specific geological structures, hydrologic characteristics, and geomorphic processes combine to alter the nature of sediment load, characteristic surface flow, and/or groundwater availability. Such locations are of two principal types: 1) those created by the presence of bedrock or relatively impermeable sediments in, beneath, or adjacent to the stream channel, and 2) those created by tributary confluences. These locations are referred to as reach boundaries, and stream segments between such boundaries are defined as stream reaches.

For a broad study area in southern Arizona and southwestern New Mexico, we have mapped and analyzed more than 1,500 linear miles of floodplains, and we’ve evaluated some 300 stream reaches. Statistical tests using known early agricultural sites and known large settlements from the much later A.D. 1200–1450 period show a very strong association between reach boundaries and the locations of sites from both of these time intervals.

Defining these “persistent places” where people settled again and again will help structure regional field research; moreover, Archaeology Southwest staff will use this knowledge to set priorities for landscape-scale preservation activities.