Chew clues: A fossilised nut of a native New Zealand tree, bearing the distinctive nibble marks of a Pacific rat.
Credit: Landcare Research
"Selective reading of the evidence"
Furthermore, the scientists said that the widespread extinction of New Zealand's native birds – such as the moa – didn't begin until after 1300 which is consistent with the latest finding.
David Lowe, a geoscientist at Waikato University in New Zealand, who was not involved in the study, said he is confident the new results are correct. He argued that the various lines of evidence for first settlement around 1300 are now numerous and substantial.
“The new rat bone ages clearly show that the ‘old’ dates published back in 1996 are untenable because they cannot be reproduced," said Lowe. "The dates on the rat-gnawed woody seed cases from sites in both North and South islands have provided a very strong line of support for the new rat bone ages.”
Richard Holdaway, coauthor of the original 1996 study, and now at Palaecol Research, in Christchurch on New Zealand's South Island, stood by his date of 2,000 years old for the rat bones.
He said that although New Zealand wasn't widely colonised until at least 1290, it had been visited by humans, carrying rats with them, over 1,000 years prior to that. He also disputed the claim that trends in the extinction of New Zealand fauna agreed with an arrival date for rats and people of around 1300.
"There are many data - published and unpublished - which speak to the extinction of small organisms on the main islands of New Zealand before [widespread] human colonisation," said Holdaway. "Only a selective reading and citation of the evidence could unequivocally take the opposing view."
Holdaway further noted that the oldest rat bones would have been the rarest in the sediments, making them the least likely to be found.
