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.