Washington, June 3 : Paleontologists have found evidence that the Maori people were New Zealand's first inhabitants, by dating remains of 150 tree nuts nibbled by ancient rats.
According to a report by ABC, Trevor Worthy of the University of Adelaide in Australia and colleagues found the evidence.
The research settles a controversy triggered in 1996 when researchers reported that they had found proxy evidence for a human presence in New Zealand 2000 years ago.
The report by Dr Richard Holdaway from the University of Canterbury and colleagues, caused a controversy since most people at the time accepted evidence that Maori were the first humans in New Zealand, and arrived much later.
"The Holdaway paper opened the door to Maori not being the people of the land which is central to their being," said Worthy.
Since then the idea that there were people in New Zealand before the Maori has gained broader acceptance, although scientific debate has raged over the accuracy of the dates in the 1996 report.
"Holdaway's 1996 paper relied on radiocarbon dating of rat bones, from the species Rattus exulans, which is generally taken as a proxy for early human presence in New Zealand," said Worthy.
"They could only get to New Zealand by human transport," according to Worthy, who was involved in the Holdaway excavation in two caves on the South Island, rich with rat bones deposited by owls.
Now, Worthy and colleagues dated bones taken from the same layers of soil excavated in the Holdaway study, as well as digging deeper to recover even older bones.
They found the oldest bones to be just 650 years old.
Worthy and colleagues confirmed their findings using a completely independent line of evidence, by dating 150 tree nuts from other sites, which were attractive food for ancient rats.
"Some of the tree seeds are nearly a centimetre long and you can clearly tell whether they've been chewed by a rat or not," he said.
According to Worthy, grooves in the nut match the width of the teeth of the rats, which were the only gnawing mammal in New Zealand at the time.
"The seeds that were not chewed extended in age back to 3000 years ago, but there was no evidence of rats prior to about 650 years ago," he explained.
Worthy has said that the findings suggest Holdaway's dates were wrong due to errors in radiocarbon dating.
According to him, at that time, radiocarbon dating was not capable of accurately date small amounts of material, which is all Holdaway had.
"Cleaner technology" being used today, together with the more numerous samples of bones and confirmation from the chewed nuts all adds up to a more convincing argument.