June 04, 2008

Rats and the dating of the earliest colonization of New Zealand

This is open access. Related story: Humans May Have Come To New Zealand Later Than Thought

PNAS | June 3, 2008 | vol. 105 | no. 22 | 7676-7680

Dating the late prehistoric dispersal of Polynesians to New Zealand using the commensal Pacific rat

Janet M. Wilmshurst et al.

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 {approx}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 {approx}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.



terryt said...

It's not mentioned in your comments but the scientists involved are now going to apply the same techniques to other islands where the timing of human arrival is disputed.

For anyone interested in the topic in more detail Tim has posted these two essays for me at his stite:



The first deals with environmental change caused by human arrival and the second with connections between New Zealand and the rest of Polynesia. My idea has been to follow these people back to their (and our) origin from Homo erectus.

mathilda said...

I may be stating the bleeding obvious... but what if the first settlers didn't bring rats with them? Outrageous.

I know it's a ground shaking thought; but in a modestly sized craft they may have been too obvious to stowaway. I know the Maori deliberately brought them along, but earlier people may not have.

If South America was showing signs of Australoid habitation about 40k ago there is NO WAY New Zealand was only colonised so recently.