Ancient DNA shows moa were fine until humans arrived

All nine species of New Zealand moa, the largest weighing up to 250 kilograms, became extinct shortly after Polynesians arrived in the country in the late 13th century.

Researchers have previously suggested, from limited genetic evidence, that huge populations of moa had collapsed before people arrived and hence influences other than people were responsible for the extinction.

Writing in the Proceedings of the National Academy of Sciences, USA, the researchers analysed the gene pools of four moa species in the 5000 years preceding their sudden extinction using ancient DNA from more than 250 radiocarbon-dated moa.

The huge data sets provided an unprecedented level of insight into what was happening to the populations of an extinct megafauna, allowing a detailed examination of the extinction process.

The genetic study was led by Professor Mike Bunce from Curtin University's Department of Environment and Agriculture, situated in Perth, Western Australia.

"Characterising a people's interactions with the environment is a fundamental part of archaeological research -- it has been portrayed anywhere on a scale from the harmonious to the catastrophic," Professor Bunce said

"Elsewhere the situation may be more complex, but in the case of New Zealand the evidence provided by ancient DNA is now clear: the megafaunal extinctions were the result of human factors.

"Lessons can certainly be learnt from the historical study of megafaunal extinctions. As a community we need to be more aware of the impacts we are having on the environment today and what we, as a species, are responsible for in the past."

Morten Allentoft, a PhD student in Professor Bunce's laboratory and now a Post-Doctoral Fellow at the Centre for GeoGenetics in the Natural History Museum in Copenhagen, performed the genetic work.

"There is nothing in our ancient DNA data that suggests that any of the four species moa was already on the way out when humans arrived," Dr Allentoft said.

"Our detailed genetic analyses, using variable nuclear markers similar to that used in forensic DNA profiling, show that moa gene pools were extremely stable throughout their last 5000 years.

"If anything it looks like their populations were increasing and viable when humans arrived. Then they just disappeared."

Professor Bunce and Dr Allentoft were joined in their research by Professor Richard Holdaway from the University of Canterbury in New Zealand and other co-authors.