A recent analysis has yielded information about the decline of megafauna (giant animals) in modern-day New Zealand. Evolutionary biologists compared DNA from fossils of nine species of moa, large flightless birds that lived for millions of years on the country's South Island. The birds' genetic information suggests that their populations were stable for at least 4,000 years before declining with extreme rapidity only after the arrival of humans on the New Zealand archipelago, 600 years ago.
In reviewing possible causes for this phenomenon, the scientists dismissed the climatic explanation that accounts for the decline of other megafauna because the extinction happened long after other megafauna had disappeared at the end of the last Ice Age. They ruled out sampling bias because a sample selection impact would not have allowed for the different results observed between the nine species. They rejected the possibility of major impacts by disease or volcanic activity because consistent genetic diversity indicates that no population diminishment occurred prior to the arrival of humans to New Zealand. The lack of population decline prior to human arrival suggests that the moa extinction was caused entirely by human hunting—a hypothesis corroborated by the remains of moa at every life stage found in rubbish piles from the earliest decade of human occupation of the islands. Such evidence leads the researchers to believe that the earliest Polynesian arrivals to New Zealand engaged in indiscriminate hunting of moa and moa eggs because their large size made them attractive as easily obtained food.