The following is an article excerpt from the Winter 2019 Issue of American Archaeology MagazineBecome a member to subscribe and read the full story! 

By Julian Smith

Last summer and fall, drivers on Interstate 10 in Tucson, Arizona, could see an archaeological dig in progress near the Ruthraff Road exit. Desert Archaeology, a local cultural resource management firm, was excavating part of a prehistoric site called Los Pozos in advance of a highway improvement project. The project is the latest investigation at the site, which stretches for over a mile between the highway and the Santa Cruz River. Los Pozos dates to the Early Agricultural Period, roughly between 2000 B.C. and A.D. 1, a period during which irrigated maize agriculture was introduced to northwest Mexico and the U.S. Southwest from Mesoamerica. Over the past few decades, researchers in the Tucson area have found that farming occurred much earlier than was once thought and that it affected the lives of residents in profound ways.

Archaeologists excavate a Late Cienega-phase structure at Los Pozos. The large storage pits dug into the floors were used to cache tools such as metates, as well as food like dried maize and mesquite beans. | Photo by Helga Worcherl
The two items on the left are fragments of plainware bowls, decorated with punctate designs. The remaining anthropomorphic figurines depict hair styles and perhaps body decoration such as face paint or tattoos. These items were likely used in esoteric or ritual practices related to maize and agriculture, and the reciprocal union between maize and humans. | Photo by Jonathan Mabry
This footprint is one of dozens found at the Rillito Fan site. The footprints suggest how ancient farmers operated their irrigation system. | Photo by Ian Milliken
Jewelry made from shell that came from the Sea of Cortez and the Southern California coast indicates that people who lived in southern Arizona during the Early Agricultural period had extensive long-distance ties with groups throughout the region. Although many items were probably obtained through trade, it is likely that people also made the journey to the coast. | Photo by: Robert Ciaccio


During the two millennia of the Early Agricultural period, local cultures gradually shifted from mobile hunting and foraging to a more sedentary lifestyle centered around growing maize, a transition that had profound effects. The Santa Cruz River floodplains and terraces offered the perfect setting for irrigation agriculture: a dependable and plentiful water source and regular floods of rich sediment, said Ian Milliken, Pima County Cultural Resources Project Manager, who is involved in the Los Pozos investigation. (Tucson is located in Pima County, and the county government is a consulting party in this project.) Residents learned how to build dams, terraces, and canal systems that watered individual garden plots. Their primary crop was maize, which was originally thought to have arrived by 1000 or 500 B.C., according to Jim Watson of the Arizona State Museum, who has worked at numerous Early Agricultural period sites.

Since the 1990s, however, a series of projects in the Santa Cruz River basin near Tucson have pushed these dates back significantly. “They really redefined our understanding of the origins and adoption of agriculture in the Sonoran Desert,” Watson said. Most, if not all, of this research has been done by cultural resource management firms hired by Pima County, the City of Tucson, and the State of Arizona.

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