Radiocarbon dating of rat bones and rat-gnawed seeds reinforces a theory that human settlers did not arrive in New Zealand until 1300 A.D. — about 1,000 years later than some scientists believe, according to a study released Tuesday.
The first settlement date "has been highly debated for decades," said Dr. Janet Wilmshurst, a New Zealander who led the international team of researchers in the four-year study.
The team carbon dated rat bones and native seeds, and concluded that the earliest evidence of human colonization in the South Pacific country was from 1280 A.D. to 1300 A.D.
Retired Maori Studies professor Ranganui Walker said the findings supported the oral history of the Maoris, who claim they were the first Polynesians to arrive in New Zealand around that time.
The Morioris, non-Maori Polynesians, have claimed they arrived earlier.
"We now have a clear picture of our country's settlement that lays to rest once and for all the Moriori myth, and so it is something to celebrate," Walker said.
The study, published Tuesday in the U.S. journal Proceedings of the National Academy of Sciences, contradicts findings from a previous radiocarbon dating study of rat bones, published in Nature magazine in 1996.
That study found evidence that man was in New Zealand from around 200 B.C.
Wilmshurst and her team re-excavated and re-dated bones from nearly all the previously investigated sites. They said none of the rat bones that they studied were from earlier than 1280.
"As the Pacific rat or kiore cannot swim very far, it can only have arrived in New Zealand with people on board their canoes, either as cargo or stowaways," Wilmshurst said. "Therefore, the earliest evidence of the Pacific rat in New Zealand must indicate the arrival of people."
The new dating of the rat bones was also supported by the dating of more than 100 woody seeds — many with telltale rat bite markings — that had been preserved in peat and swamp sites on North and South Islands, Wilmshurst noted.
Dr. Tom Higham, a member of Wilmhurst's team and deputy director of the Oxford Radiocarbon Accelerator Unit at Oxford University, said the teeth marks could not be mistaken for those of another animal.
He said the rat-gnawed seeds provided strong additional evidence for the arrival of rats, and therefore humans, and were an indirect way of testing the veracity of the dates done on the rat bones.
Among the seeds analyzed were some that were intact or bird-cracked, and the rat-gnawed ones occurred in both islands only after about 1280.
But Prof. Richard Holdaway, a lead researcher on the earlier human contact theory published in Nature, on Tuesday stood by his 1996 study that found evidence of rats and humans in New Zealand more than 2,000 years ago.
"Rats arrived, people obviously arrived [but] whether they stayed — I have consistently said they didn't," he told TV3 News.
He also suggested that the new research team did not consider all available evidence in its study, leading to the different results.
But University of Adelaide paleontologist Trevor Worthy, a member of the Wilmhurst team, was adamant the new carbon dating results proved the Nature claim wrong.
"There is no supporting ecological or archaeological evidence for the presence of Pacific rat or humans until 1280-1300 A.D. and the reliability of the bone dating from that first study has been questioned," Worthy said. He did not explain why the other study had been questioned, or by whom.