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New research led by UNSW Sydney paleontologists challenges the idea that Indigenous Australians hunted Australia's megafauna to extinction, suggesting instead they were fossil collectors.

The research, published in the journal , focuses on the fossilized tibia (lower leg bone) of a now-extinct, giant sthenurine kangaroo. Found in Mammoth Cave in southwestern Australia around the time of the First World War, the bone was showing that Indigenous Australians hunted megafauna.

Paleontologist and expert on Australia's prehistoric fossil record, UNSW's Professor Mike Archer, was involved in the original study published in that found a distinctive cut in the fossilized bone was evidence of butchery. But he now happily concedes this original finding was wrong.

"As a scientist, it's not just my job but my responsibility to update the record when new evidence comes to light," he says.

"Back in 1980, we interpreted the cut as evidence of butchery because that was the best conclusion we could draw with the tools available at the time. Thanks to advances in technology, we can now see that our original interpretation was wrong."

Smoking gun or shot in the dark?

Prof. Archer says when the bones were analyzed from the 1960s onwards, there was much debate about whether or not First Peoples lived compatibly with Australia's prehistoric megafauna—enormous marsupials, massive flightless birds and giant reptiles that roamed the continent during the Pleistocene, 65,000 years ago—or whether they were the cause of the extinction of these megafaunal animals.

Many saw the incision in the bone as being made by humans with tools—something Prof. Archer says is not under dispute—and that it finally showed that the extinction of megafauna and arrival of humans about 65,000 years ago was no coincidence.

"For decades, the Mammoth Cave bone was a 'smoking gun' for the idea that Australia's First Peoples hunted megafauna, but with that evidence now overturned, the debate about what caused the extinction of these giant animals is wide open again, and the role of humans is less clear than ever," he says.

New technology retells an old story

To re-analyze the same sthenurine leg bone with the incision, the team used high-tech, 3D-scanning (microCT) to look inside the bone without damaging it. They also used updated radiometric dating technology to try to work out how old the bone and the cut really were and detailed microscopic analysis of the cut surfaces.

Their analyses revealed the cut was made after the bone had dried out and had developed shrinkage cracks—meaning it was likely already fossilized when the incision occurred.

The study also analyzed a fossil tooth "charm" given by a Worora Nations man at Mowanjum Mission to an archaeologist working with First Nations people in the Kimberley—Kim Akerman—in the 1960s. The tooth belonged to the extinct Zygomaturus trilobus, a type of giant marsupial, distantly related to wombats, that was part of Australia's Pleistocene megafauna.

Although the tooth was received in the Kimberley, in northwestern WA, its characteristics and composition were a close match with other fossils from Mammoth Cave in southwestern WA.

"The tooth's presence in the Kimberley, far from its likely origin in Mammoth Cave, suggests it may have been carried by humans or traded across vast distances," says Dr. Kenny Travouillon, one of the study's co-authors from the Western Australian Museum.

"This implies a cultural appreciation or symbolic use of fossils long before European science did. You could say that First Peoples may have been the continent's—and possibly the world's—first paleontologists."

Implications

The researchers do not completely rule out the possibility that First Peoples hunted Australia's megafauna. But they say without hard evidence, it's not possible to definitively say Indigenous Australians were responsible for the extinction of Australia's prehistoric megafauna.

"While these are hypotheses, hard evidence is required before it can be concluded that predation on the now extinct megafaunal species by First Peoples contributed to their extinction, particularly given the long history First Nations peoples have had in valuing and sustainably utilizing wildlife in Australia," says Prof. Archer.

"If humans really were responsible for unsustainably hunting Australia's megafauna, we'd expect to find a lot more evidence of hunting or butchering in the fossil record. Instead, all we ever had as hard evidence was this one bone—and now we have strong evidence that the cut wasn't made while the animal was alive."

So if humans weren't solely responsible for the demise of Australia's ancient megafauna, what may have caused it?

The researchers cite evidence that many megafauna species vanished long before humans arrived while others co-existed with humans for thousands of years, but their disappearance often coincides with periods of significant climate change.

"What we can conclude is that the first people in Australia who demonstrated a keen interest in and collected fossils were First Peoples, probably thousands of years before Europeans set foot on that continent," the study authors say in closing.

Prof. Archer says he and his fellow researchers hope that further down the line, additional tests can be run on the bones from Mammoth Cave and on the materials making up the intriguing charm to try to nail down the ages of these items and more about their history.

"But even more important would be more where there is albeit controversial evidence that humans and now extinct megafauna may have coexisted for at least 30,000 years without any hard evidence that any of the megafaunal species had been killed or butchered by people."