Dating the late prehistoric dispersal of Polynesians to New Zealand using the commensal Pacific rat
- *Landcare Research, P.O. Box 40, Lincoln 7640, New Zealand;
- ‡Department of Archaeology and Natural History, Research School of Pacific and Asian Studies, Australian National University, Canberra ACT 0200, Australia;
- §Oxford Radiocarbon Accelerator Unit, Research Laboratory for Archaeology and the History of Art, Dyson Perrins Building, South Parks Road, University of Oxford, Oxford OX1 3QY, United Kingdom; and
- ¶School of Earth and Environmental Sciences, University of Adelaide, South Australia 5005, Australia
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Edited by Patrick V. Kirch, University of California, Berkeley, CA, and approved April 7, 2008 (received for review February 14, 2008)

Abstract
The pristine island ecosystems of East Polynesia were among the last places on Earth settled by prehistoric people, and their colonization triggered a devastating transformation. Overhunting contributed to widespread faunal extinctions and the decline of marine megafauna, fires destroyed lowland forests, and the introduction of the omnivorous Pacific rat (Rattus exulans) led to a new wave of predation on the biota. East Polynesian islands preserve exceptionally detailed records of the initial prehistoric impacts on highly vulnerable ecosystems, but nearly all such studies are clouded by persistent controversies over the timing of initial human colonization, which has resulted in proposed settlement chronologies varying from ≈200 B.C. to 1000 A.D. or younger. Such differences underpin radically divergent interpretations of human dispersal from West Polynesia and of ecological and social transformation in East Polynesia and ultimately obfuscate the timing and patterns of this process. Using New Zealand as an example, we provide a reliable approach for accurately dating initial human colonization on Pacific islands by radiocarbon dating the arrival of the Pacific rat. Radiocarbon dates on distinctive rat-gnawed seeds and rat bones show that the Pacific rat was introduced to both main islands of New Zealand ≈1280 A.D., a millennium later than previously assumed. This matches with the earliest-dated archaeological sites, human-induced faunal extinctions, and deforestation, implying there was no long period of invisibility in either the archaeological or palaeoecological records.
Footnotes
- ↵†To whom correspondence should be addressed. E-mail: wilmshurstj{at}landcareresearch.co.nz
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Author contributions: J.M.W., A.J.A., T.F.G.H., and T.H.W. designed research, performed research, analyzed data, and wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0801507105/DCSupplemental.
- Received February 14, 2008.
- © 2008 by The National Academy of Sciences of the USA
Freely available online through the PNAS open access option.
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