abstract: Environmental change has often been cited as affecting choices made whether to pursue cooperative or competitive strategies. The Flagstaff region provides a unique opportunity to address how environmental changes may affect choices made between competition and cooperation. Part of the region was a prehistoric frontier zone between three archaeological cultures and these groups had to contend with a marginal and highly variable climate for agriculture. These regional patterns of climatic variation are well documented and further the eruption of Sunset Crater Volcano in the midst of this frontier zone devastated local environments and reshaped the landscape. As groups re-colonized the frontier zone, they actively sought to negotiate new boundaries using both competitive and cooperative strategies that can be discerned archaeologically, including intergroup violence and the construction and use of communal ritual architecture. Dendroclimatological data is used to identify periods of environmental change and expectations for cooperative and competitive responses to these changes are developed based on anthropological theory and ethnographic case studies. These expectations are then tested against the archaeological record. Three lines of evidence are used to assess changes in levels of competition: (1) use of defensive sites, (2) presence of skeletal trauma, and (3) emergence of specialized social roles and weapons technologies. Two lines of evidence are used to assess changes in levels of cooperation (1) use of communal ritual architecture and (2) patterns of exchange. In some cases the expected relationships between favorable conditions and evidence of increased cooperation and between unfavorable conditions and evidence of increased competition are found. However, in other cases the expectations are not supported, with local historical and cultural contingencies appearing to override environmental influences. Contrasts between patterns of cooperation and competition found in the culturally diverse frontier zone versus the patterns found in the more culturally homogenous heartland are identified that suggest greater likelihood of the emergence of conflict in settings with pre-existing contexts of social differences. / Dissertation/Thesis / Doctoral Dissertation Anthropology 2015

Sarahsaurus aurifontanalis is the most recent sauropodomorph dinosaur to be discovered and named from the Early Jurassic of North America. The dinosaur is represented by a mostly complete and articulated holotype specimen that preserves a unique manual phalangeal count of 2-3-4-2-2 and accessory pubic foramen adjacent to the obturator foramen. The holotype of Sarahsaurus comprises a braincase and isolated cranial elements, but the skull previously referred to this taxon, MCZ 8893, can only be provisionally referred to Sarahsaurus until additional crania are found associated with postcranial material. Sarahsaurus comes from the middle third of the Kayenta Formation, which is considered to be Early Jurassic in age despite the absence of a radiometric date from that unit. A new technique used to obtain a U-Pb radiometric date from the type quarry of Sarahsaurus in the Kayenta Formation was influenced by secondary uranium enrichment in the open system of the fossil bone. That suggests that uranium within the Kayenta Formation may be the result of the movement of groundwater during the Laramide orogeny in the Late Cretaceous and Early Eocene, and lends support to the hypothesis that the uplift of the Colorado Plateau began relatively early in Late Cretaceous to the Eocene. / text