Extinct Bird Key to Dating Australia’s Oldest Cave Art

When humans first set foot on Australia’s northern shores some 50,000 years ago, Genyornis newtoni, a bird three times the height of an emu, would have been an important item on their menu. This red ochre painting of the extinct bird—the first of its kind—was discovered in a narrow rock shelter in Arnhem Land two years ago, but its significance was recognized only this month after a visit by archaeologists.

“It means either that it was painted at the time of the Genyornis bird, or that the Genyornis had lived longer than we thought,” archaeologist Ben Gunn told the Agence France Press.

​Some of the oldest rock paintings in the world are found in Australia, but putting a hard date on these ancient artworks remains a technical challenge. Scientists are rarely able to use chemical methods to estimate the ages of organic pigments, and must ballpark dates by judging the sophistication of the painting or its geological context. That’s why finding the depiction of an extinct animal is of such importance. Last year, for instance, scientists identified a marsupial lion painted on rocks in the Kimberley region, suggesting those paintings are at least 30,000 years old.

Genyornis is thought to have gone extinct relatively soon after humans arrived on the scene, which means the newly discovered painting could be 40,000 years old, making it the oldest in Australia, if not the world.

But, like most topics in the study of cave art, that interpretation has not been unanimous. Robert Bednarik of the International Federation of Rock Art Organizations told The Australian he was not convinced it depicted a Genyornis and he thought that it was only 5000 years old. “I am not aware of any painting or even petroglyph of an animal anywhere in the world that is more than 10,000 years old located outside of caves.”

Brendan Borrell will be guest blogging this month. He lives in New York and writes about science and the environment; for Smithsonian magazine and Smithsonian.com, he has covered the ecology of chili peppers, diamonds in Arkansas and the world's most dangerous bird.