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The construction of great houses during the Bonito Phase (ca. AD 850–1200) in Chaco Canyon, New Mexico, required massive amounts of building material and efficient mobilization and coordination of large labor pools. We employ least cost path analysis (LCA) to explore the potential communication network among great house communities in the Chaco “core” area and its relevance in managing sustained labor for constructing great houses. The results suggest that that the primary sources of labor for communal building projects were agricultural communities located within one to three hours of the largest buildings in the canyon.

Pueblo Bonito in Chaco Canyon is one of the most iconic pre-Hispanic archaeological sites in the U.S. Southwest. Archaeologists refer to it as a great house in recognition of its massive scale, and often describe it as the centre of the Chaco world. Yet questions remain about Pueblo Bonito’s origins, sequence of construction, duration of occupation and abandonment. Here, the authors present new research that helps to clarify the early phases of occupation, and illuminates some of the problems inherent in reconstructing a building that was a perennial work in progress.

There are two large mounds comprised of enormous quantities of construction debris and discarded household debris associated with rapid growth of the Pueblo Bonito great house in Chaco Canyon between ca. CE 1040 and 1100. There is some debate among specialists as to whether these features were expedient refuse middens or constructed platform mounds or something in between, and thus whether they index political processes linked to control of labor by elites. Although originally investigated by archaeologists between 1896 and 1927, this study presents the first detailed formation history for each mound, based on recent fieldwork by the University of New Mexico. We argue that the mounds were not the product of institutionalized political power as assumed for platform mounds in other parts of North America but rather reflect local landscape changes associated with complex social negotiations during a period of rapid social transformation.

Modern datasets provide the context necessary for accurate interpretations of isotopic data from archaeological faunal assemblages. In this study, we use the oxygen isotope ratios (δ18O) of modern small mammals from Chaco Canyon, New Mexico, to quantify expected isotopic variation in a local population. The δ18O values of local, modern small mammals encompass a broad range (−6.0‰ to 4.8‰ VPDB), which is expected given the extreme seasonal variation in the δ18O of precipitation on the Colorado Plateau (−11‰ to −3‰ VPDB). Isotopic ratios of small mammals obtained from excavated archaeological sites in Chaco Canyon (ca. AD 800 to 1200) show no significant differences with their modern counterparts, suggesting that there is no difference in the origins of the archaeological small-mammal collection and the modern, local Chaco Canyon small-mammal collection. In contrast, δ18O values of large mammals from Chaco archaeological sites are significantly different from those of modern specimens, reflecting a nonlocal, but also nonspecific, source in the past.

Agricultural intensification is widely assumed by archaeologists to have been a catalytic factor in the development of social complexity in Chaco Canyon, New Mexico, between ca. AD 850 and 1200. In this perspective, water control technology resulted in surplus food production which was controlled by elites to finance the construction of massive buildings (“great houses”). However, recent fieldwork and archival research has been unable to substantiate this view of technological innovation promoting surplus agricultural production. An alternative explanation for economic growth is social transactions involving labor rather than food.

Recent archaeological investigations at Pueblo Bonito in Chaco Canyon reveal that residents constructed a large diversion channel during the eleventh century A.D. as dramatic growth resulted in the expansion of the building onto the main valley floor. Sediments in the diversion channel reflect repeated episodes of flooding, rather than slow moving water typically found in irrigation canals, and archaeobotanical data indicate deposition during late summer or early fall. Although an agricultural function is possible, the channel may have been built primarily to divert floodwaters away from Pueblo Bonito while providing a nearby water source for construction and domestic use. The diversion channel was destroyed by the entrenchment of the “Bonito paleo-channel” in the late A.D. 1000s, and then buried by a combination of cultural debris and valley flooding. Although the canyon stream system changed throughout the occupation of Pueblo Bonito, there is no evidence that the formation of a deep natural channel in the floodplain had any negative effect on the growth of the great house