Archaeological analysis of Rapa Nui settlement structure : a multi-scalar approach

Ph.D. University of Hawaii at Manoa 2012.Includes bibliographical references.With over 700 megalithic statues (moai) and more than 200 monumental stone platforms (ahu), the small island of Rapa Nui (Easter Island, Chile), boasts one of the world's most remarkable cultural achievements. While substantial archaeological research on Rapa Nui settlement and social organization has been conducted in the past, a number of questions regarding settlement structure remain unresolved. This dissertation addresses three main research questions: first, what was the size and structure of communities on pre-Contact Rapa Nui? Second, did organizational scale include a centralized administrative hierarchy or were communities relatively small autonomous social units? Third, what role did agricultural potential play in population size and structure? These primary research questions are investigated using a Darwinian evolutionary framework incorporating the concepts of cooperation and competition, human territoriality, environmental risk and uncertainty, costly signaling, and multi-level selection. The tenants of Human Behavioral Ecology (HBE) are used to model social group size and structure. Over 3000 archaeological features distributed across seven survey areas were recorded during fieldwork from 2001-2010. A non-site approach to archaeological survey was necessary in order to record the full range of feature classes across the Rapa Nui landscape. Discrete scale archaeological features were the minimal unit of field recording. These discrete archaeological features are aggregated to create larger archaeological units at the scale of activity zones and redundant feature sets. Two spatial statistical techniques, Ripley's K and Kernel Density Estimation are used to identify the spatial scale of social organization and to determine the boundaries of Rapa Nui settlements. Spatial differences in the structure of these settlements across the seven survey areas are mapped and described through paradigmatic classifications of these aggregate scale archaeological units. Additional environmental datasets derived from meteorological observations from 1960-2000, digital elevation models (DEM), and geologic substrate maps, are used to create a soil fertility model for the island. Computer based spatial technologies such as computer simulations and Geographical Information Systems (GIS) technology are used to analyze the temporal and spatial characteristics of rainfall and soil fertility on Rapa Nui. Risk classification maps are produced displaying the location of different productivity zones for Rapa Nui agriculture. Spectral analysis of rainfall data is also conducted. The model results indicate that the Rapa Nui environment is characterized by spatial heterogeneity and temporal uncertainty. The combined archaeological and environmental results of the study suggest that Rapa Nui society was arranged in a dispersed settlement pattern and communities were organized at small spatial scales probably consisting of close genetically related individuals. There is no apparent evidence for centralized hierarchy and/or social stratification. The specific social organization and settlement structure on Rapa Nui developed out of a relationship between cooperative and competitive strategies for survival in an ecologically risky and uncertain context. The scale of organization and settlement structure are a reflection of both agricultural risk minimization, effective cooperation in the face of constant competition and aggression, and heterogeneity in resource distribution. The settlement data also indicate that while communities were highly localized, social groups cooperated at somewhat larger spatial scales in order to construct religious structures (ahu) and statuary (moai). Community based activities on Rapa Nui would have helped to build important social ties which would have facilitated information sharing. Additionally, the construction and transportation of large costly field monuments would have communicated to other groups an important message about the associated costs and/or benefits of engaging in aggressive interactions. Ultimately the results of this study challenge notions about the role of centralized social organization, cooperation, and monumental architecture on Rapa Nui and elsewhere