Lying about 425 kilometers off the African coast, Madagascar was long thought to be one of the last corners of Earth to be settled. This week in Science Advances , however, researchers report that ancient butchered bones show people made their home on the lush island 10,500 years ago, an astonishing 8 millennia earlier than once thought.

The discovery, by a team led by James Hansford of the Zoological Society of London, rekindles a contentious debate over whether humans are responsible for the extinction of Madagascar's unique megafauna, including giant lemurs and the world's largest bird. All flourished after the island broke away from the Indian subcontinent 88 million years ago, then died out centuries ago, seemingly not long after people arrived. But the blade-scarred bones from the massive elephant bird Aepyornis maximus suggest a long coexistence between humans and megafauna—challenging the belief that people inevitably kill off large mammals and flightless birds when they arrive in a new land.

David Burney, a paleobiologist at the National Tropical Botanical Garden in Koloa, Hawaii, who was not involved in the study, says the results "fly in the face of all that we thought we knew about human arrival in Madagascar." The discovery, along with a few other new finds that also point to early settling, "is big news," he says, although he and others question whether it is enough to resolve the megafauna debates.

Pinning down the arrival date of humans on Madagascar has been difficult, says Ian Tattersall, an anthropologist at New York City's American Museum of Natural History (AMNH), because "archaeological evidence for early human presence … is scarce at best." East Africans and Indonesians are known to have established farming settlements by 500 C.E., but butchered bones of now-extinct lemurs and hippos hinted that humans were present a half-dozen centuries earlier. And on the northeast coast, archaeologists recently found small stone blades that appeared to date to before 2000 B.C.E., although the claim is not widely accepted.

In 2008, anthropologist Patricia Wright of the State University of New York in Stony Brook heard from a colleague's aunt that a man looking for sapphires had unearthed dinosaur bones near Ilakaka, in the south central part of the island. "I didn't believe the aunt, but eventually went to visit," Wright says. With Armand Rasoamiaramanana of the University of Antananarivo, she found the "dinosaurs" were actually the remains of massive lemurs, hippos, giant tortoises, and crocodiles. The trove also included bones from the elephant bird, an ostrichlike creature that stood more than 3 meters high and weighed more than 350 kilograms.

The bones were stored at a nearby field center, where Hansford examined them in 2016. On 2-meter-long leg bones from the elephant bird, he noticed deep grooves, evidently made by humans butchering their prey with sharp stone tools. By measuring carbon-14, the team dated the bones to 10,500 years ago. The find "represents the earliest known evidence of human presence in Madagascar," Hansford and colleagues note.

The date does more than push back humans' arrival. Many archaeologists accept the idea proposed more than 4 decades ago by archaeologist Paul Martin of the University of Arizona in Tucson that megafauna such as mammoths and other giant mammals on northern continents died off because of a "blitzkrieg" by human hunters entering new territory, not because of factors like climate change. Madagascar has since emerged as a key testing ground for the theory.

Hansford argues that his group's results, by showing that humans coexisted with megafauna for as long as 9 millennia, "eliminate the rapid extinction hypothesis or blitzkrieg for Madagascar." Only after farming populations had expanded across the island, altering the environment and increasing hunting pressure, did creatures like the elephant bird finally go extinct, he proposes. Ross MacPhee, an anthropologist at AMNH, says the paper's conclusion is "highly consequential," because such extinctions "are frequently held up as proof of humanity's consistent record of destruction, past, present, and future."

Tattersall, however, says it's "premature" to make generalizations about human impact. He and Burney, a longtime advocate of the blitzkrieg theory, both note that the Madagascar find could be a sign of a small group of humans who sojourned only briefly on the island, with little effect on the fauna. And the blitzkrieg hypothesis remains viable elsewhere: New Zealand's moa—another large flightless bird—went extinct less than 2 centuries after the arrival of the first Polynesians. The Madagascar example may show there is no one-size-fits-all explanation for the extinctions, says Henry Wright, an archaeologist at the University of Michigan in Ann Arbor.

So far, the archaeologists searching through the ancient bones have not found stone tools, which might shed light on the early settlers' way of life and how long they persisted on the island. Resolving the twin debates about Madagascar's settlement and the demise of its megafauna will take more digging and dating, Hansford concedes. He and his team hope to return to the bone pit in the near future, "now that we understand the incredible significance of the site."