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Thu March 28, 2013
Dr. David Burley, Simon Fraser University – Dating Polynesian Settlement
In today’s Academic Minute, Dr. David Burley of Simon Fraser University explains how radiometric dating techniques are improving our understanding of exactly when the settlement of Polynesia began.
David Burley is a professor of anthropology at Simon Fraser University in Burnaby, British Columbia. His teaching and research interests include archaeology and ethnohistory, archaeological theory, maritime adaptations, and the prehistory of Oceania. He has been conducting archaeological field research in Tonga since 1989, and in Fiji since 1996. He holds a Ph.D. from Simon Fraser University.
Dr. David Burley – Dating Polynesian Settlement
It was over two decades ago that I began archaeological research into first Polynesian settlement in the Kingdom of Tonga. Tonga is located on the western edge of the Polynesian triangle, and it would have been the initial set of Polynesian islands to be encountered. These studies have been successful in finding the earliest settlements throughout the length of the archipelago. In fact based on several lines of excavated data, we now pinpoint first Polynesian landfall in the small fishing village of Nukuleka on the island of Tongatapu.
In spite of this success, it has been much more difficult to precisely establish an age for this settlement. We have relied on radiocarbon dates, but radiocarbon years are not calendar years. When they are calibrated, the dates turn into probability statements with quite substantial age spans. At an archaeology conference in Samoa last year, my problems with dating were about to change dramatically. Marshall Weisler and Jin-Xian Zhao from the University of Queensland were looking for early Tongan samples to apply uranium/thorium dating to. U/Th is a radiometric dating technique that works well on calcium carbonate materials such as coral. From excavations at Nukuleka, I had recovered coral files, a type of artifact used as rasps to abrade shell or smooth wood. Coral is subject to diagenetic alteration however, and Weisler and Zhao had to refine the U/Th preparation protocols and develop new ones to guarantee accuracy.
I cant remember being optimistic, but my first review of their results was truly jaw dropping. These dates had a precision of plus or minus 8 to 10 years. The earliest, 888 ± 8 years BC, came from a coral file buried in the sand beneath the Nukuleka site. It is the beach on which the first people into Polynesia walked, and we now know exactly when that happened.
Production support for the Academic Minute comes from Newman’s Own, giving all profits to charity and pursuing the common good for over 30 years, and from Mount Holyoke College.