The timing of animal extinctions gives an alternative date for human arrival and settlement. Polynesians hunted large birds, such as moa, to extinction. Early archaeological sites of human settlement, which belong to a period after 1300 AD, contain evidence for the extinction of 11 species of moa and other large birds. The moa possibly died out within 100–200 years of people arriving.
Some researchers, such as Richard Holdaway, have attempted to show that extinctions or population declines of bats, lizards, frogs and smaller birds (petrels, the owlet-nightjar, Finsch’s duck) prior to 1300 may be due to the predatory Pacific rat. This would mean that humans had also been present in this earlier period. But proof of extinctions or population declines is hard to find, as most dead animals leave very little evidence as to what killed them. Because of this the decline of species in New Zealand can only be linked circumstantially with rat predation, if at all. Rat-gnawed snail shells from Northland provide the earliest concrete evidence to date, but these only occur after 1250.
If there were rats in New Zealand before 1300, why is there no evidence of them gnawing on snails and seeds? The research on gnawed seeds and snail shells does not support the theory that rats arrived as early as 50–150.
It is only when many different dating methods, from many different parts of New Zealand, on several different lines of evidence, all converge to show similar results that most scientists will feel comfortable in determining a first arrival date earlier than the generally accepted date of 1250–1300. One problem is the short time since first human arrival in New Zealand. Regardless of the debate as to whether this was 700 or 2,000 years ago, most dating techniques have their limitations over such short spans, and interpreting results requires extraordinary care.
Acknowledgements to David J. Lowe (University of Waikato), Bruce McFadgen (independent archaeologist) and Janet Wilmshurst (Landcare Research)