Moa were hunted into extinction by humans, and were not wiped out by natural causes, a conclusive fossil study has found.
All nine species of the flightless bird, the largest weighing up to 250kgs, became extinct shortly after Polynesians arrived in New Zealand in the 13th century.
Researchers have previously suggested, from limited genetic evidence, that huge populations of moa had collapsed before people arrived.
And, therefore, influences other than people - like disease, climate change, or volcanic eruption - were responsible for the end of the species.
But now, researchers from New Zealand, Australia, and Denmark believe they have concrete evidence man killed off the moa within 200 years of arriving.
"In the case of New Zealand, the evidence provided by ancient DNA is now clear: the megafaunal extinctions were the result of human factors," said the genetic study's leader, Professor Mike Bunce of Curtin University, Western Australia.
Writing in the Proceedings of the National Academy of Sciences, USA, the researchers, which included Professor Richard Holdaway of University of Canterbury, 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 moa populations at the time, allowing a detailed examination of the extinction process.
"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.
"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 at the Natural History Museum in Copenhagen, performed the genetic work.anima
There was nothing in their ancient DNA data that suggested that any of the four species of moa were 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," he said.
"If anything, it looks like their populations were increasing and viable when humans arrived. Then they just disappeared."