Bird’s Extinction Is Tied to the Arrival of Humans

When Maori settlers arrived in New Zealand in the 13th century, they were greeted by some formidable inhabitants: the moa, nine species of flightless birds up to 12 feet tall.

The creatures lacked even vestigial wings; they looked like walking bags of feathers with a small head perched on top. The moa were the dominant large herbivores in New Zealand, which had no native mammals, save for bats.

Over the next century or so, the moa disappeared. Their very existence was unknown until the 19th century, when excavations of Maori shell heaps revealed oven-charred skeletons, gizzard stones and eggshells.

Scientists have long assumed that humans played a role in the moa’s obliteration, but that became a subject of debate. Some researchers believed that the bird was already on the way out when humans arrived, thanks to factors like climate change, volcanic eruptions and disease.

But now scientists have turned to a relatively new DNA examination technique called microsatellite analysis, also used in forensics and paternity suits. The inescapable conclusion, they report in Proceedings of the National Academy of Sciences, is that humans were the sole culprits.

Morten Erik Allentoft, a researcher at the University of Copenhagen, and colleagues analyzed DNA from 281 moas collected from museums and new excavations, and estimated the age of those specimens using radiocarbon dating. They found that in the millenniums before humans arrived in New Zealand, the moa displayed none of the genetic bottlenecking indicative of a declining population.

The South Island giant moa even appeared to be on the rise when people arrived. “Nothing at all suggests a decline in the 5,000 years before the moa’s extinction,” Dr. Allentoft said. “Then humans arrive and it happens very fast: This big, healthy population hits the wall and disappears.”

Even today, though, some people hold out hope that moas survive somewhere. Some hotels offer to take tourists into the mountains to look for them, Dr. Allentoft said, adding, “These birds are too big to walk around undiscovered for that many years.” RACHEL NUWER