A Precise Chronology for Polynesian Monumental Architecture via Th-230 Coral Dating

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Throughout both the Old and New Worlds, the development of monumental architecture, such as religious temples and shrines, provides one of the clearest archaeological signals of the emergence of complex, stratified societies from simpler societies organized primarily around kinship. In particular, complex chiefdoms and the early archaic states that emerged from them typically exercised power through a control hierarchy linked to religious ritual and temples. Precise and accurate dating of such ceremonial architecture can therefore provide unprecedented insight into the pace of economic, social, and political developments in ancient societies that lacked calendars and written records. Conventional approaches to dating such monumental architecture constructed in Polynesia prior to European contact have relied principally on the use of oral traditions and radiocarbon dating, supplemented by considerations of architectural style and construction methods. However, the accuracy of uncorroborated oral traditions is uncertain, the precision of radiocarbon dates within key intervals can be severely degraded by the inherent difficulty encountered in converting radiocarbon dates to calendar years, and considerations of construction style and technique do not reveal the tempo of related social changes. In Eastern Polynesia, however, a widespread and ancient association between coral and ritual sites and structures makes it possible to precisely and accurately date a variety of ceremonial architecture using superior radio-isotopic dating techniques applicable to coral offerings. Prof. Patrick Kirch and Dr. Warren Sharp, the principal investigators on this project, have recently shown that a species of branch coral placed by ancient Hawaiians as dedicatory offerings on coastal fishing shrines and inland agricultural temples may be dated with precisions of circa + or - 10 years by using a technique based on the radioactive decay of minute amounts of the element uranium incorporated into coral skeletons during their growth. Preservation of delicate surface structures on archaeological corals selected for dating confirms that ancient Hawaiians collected living corals. Thus the coral dates, which record growth of the coral skeleton, closely correspond to placement of corals on altars or in temple walls. Accordingly, Kirch and Sharp propose a comprehensive program of coral dating applied to monumental ritual structures in two Eastern Polynesian societies, Hawai'i and the Society Islands, where ritual architecture was closely associated with the emergence of sociopolitical complexity. Kirch has extensive experience in both areas and our proposed dating study will build on well-established archaeological contexts based on extensive mapping, site studies and radiocarbon dating developed during previous and ongoing studies by himself, additional collaborators T. Ladefoged (U. of Auckland), L. Holm and J. Kahn (doctoral candidates, U.C. Berkeley), and others.Broader impacts of the proposed research will include developing the application to archaeology of the powerful uranium-decay coral dating technique, with its potentially widespread application to archaeological studies in Polynesia and elsewhere that ancient humans used live corals. The proposed research will also enhance the training of two U.C. Berkeley doctoral candidates in archaeology, and provide "hands-on" laboratory research experience for a U.C. Berkeley undergraduate student. The Society Islands component of the project will be coordinated with l'Universite de Polynesie Francaise, and will enhance recent academic collaborations between that institution and U. S. archaeologist