Old rat bones provided scientists from Landcare Research and Oxford University with clues about human settlement in New Zealand. The scientists used radiocarbon dating to work out how old the bones are. The scientists also tested seeds which had distinctive tell-tale rat bite marks, preserved in peat and swamp sites from the North and South Islands. The dating project worked out that the rat bones and gnawed seeds are approximately 720 years old.
“The width of the teeth marks left on the woody seeds exactly match those of a rat's two front teeth, and cannot be mistaken for any other seed predator. We have dated over 100 individual seeds, some rat-gnawed, others intact or bird-cracked, which show that rat gnawed seeds only occur in both the North and South Islands of New Zealand after about 1280 AD,” Dr Janet Wilmshurst from Landcare Research explains.
This is significant as rats are not native to New Zealand and are intimately associated with humans. When a large canoe or ship arrives in port it almost invariably brings rats with it. “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. Therefore, the earliest evidence of the Pacific rat in New Zealand must indicate the arrival of people.”
The finding that the rat remains and gnawed seeds are only 720 years old most likely means that people did not settle in New Zealand until 1280 to 1300. This contradicts earlier research which put the time of human settlement much earlier at around 2,000 years ago. However, the findings do support work published several years ago by a palaeoecologist named Dr Matt McGlone. Dr McGlone uncovered evidence of a New Zealand-wide burn-off of forest around the 13th century, implying initial settlement of New Zealand and a large migration at that time. Dr McGlone discovered this by analysing the pollen content of sedimentary deposits throughout New Zealand when he was mapping past vegetation over the last twelve to fourteen thousand years.
Of significance to human history are distinct layers of charcoal in soil horizons and wetland sediments throughout New Zealand. Dr McGlone explains how the observation can be used to date the time of human arrival in New Zealand. “What we’ve found is that at most sites the evidence for human burn-off shows it was rapid. The forest pollen types drop characteristically within a few tens of years really, sometimes fifty or a hundred years perhaps, but mainly they drop off very quickly. Then after the burn-off, either bracken, scrub or grassland dominates the pollen coming into the site.”
“Also, at the same time as deforestation, there is a mass of supporting evidence for early human activity, for example, suddenly many birds became extinct, seal populations declined, and the first evidence for human settlement occurs from kill sites, tool kits, carvings, burials etc.”
A paper about the work done by the international team of researchers, led by Dr Wilmshurst, was published in June 2008 in the prestigious journal Proceedings of the National Academy of Sciences in the United States.