New Zealand's moas were flightless birds that ruled over the country until the first human settlement arrived. The biggest of the moas had a height of 12 feet with an outstretched neck. The entire moa population composed of nine species had disappeared shortly after the arrival of the first humans in New Zealand in the 13th century.
Since then, scientists have long argued about the reason why the big and diverse birds became extinct. Some theories had contended that the birds were declining due to changes in the environment or volcanic activities before the first humans had arrived on New Zealand's shores.
A new study published in the Proceedings of the National Academy of Sciences (PNAS) had found no such evidence of the previous theories but suggested humans were more likely the culprit behind the moas' extinction.
Scientists had examined two different DNA sets out of 281 specimens from four species, namely the South Island giant moa which was the largest in the family; the heavy-footed moa, the eastern moa and the coastal moa.
Instead of a slow genetic decline, scientists found a different DNA story. New Zealand's moas had been thriving despite the presence of humans in the land. According to lead researcher Morten Allentoft from the University of Copenhagen, the millennia before the moas' extinction had a "remarkable degree of genetic stability" in all species.
Mr Allentoft and his team discovered that some moa populations had thrived right up to the end. Scientists were baffled that the end of the species had come so fast that there was no imprint in the four species' genes. A mark will be usually left behind once species are constricted by genes. Scientists called the extinction of New Zealand's moas as the "most rapid, human-facilitated megafauna extinction documented to date."
The latest findings were in contrast to an earlier study in 2004 which suggested that the moas were already in decline even before the first humans had arrived. However, the previous study was only limited to data using mitochondrial DNA. Mr Allentoft and his team had used mitochondrial DNA and nuclear microsatellite genotyping to generate population trends.
The new study coincides with archaeological findings that revealed mounds of butchered moas and eggs. Like most animals that have seen humans, New Zealand's moas were possibly not afraid of man which made hunting them easy.
Mr Allentoft said heaps of the moas' bones were often found in archaeological sites. Hunting the moas or all animals for that matter in every stage can lead to their extinction.