Climate shift shaped Aussie extinctions

Stone Age people lived virtually side-by-side with now-extinct animals in western Australia for 6,000 years, a new study has revealed. The finding quashes the proposal by some anthropologists that ancient settlers rapidly hunted the creatures—including a hornless, rhinolike creature, a flightless bird that resembled an emu, and a short-faced kangaroo—out of existence. The defunct animals died out gradually as climate changes reshaped their habitats, say Clive N.G. Trueman of the University of Portsmouth in England and his coworkers.

Trueman’s group studied fossils unearthed at a dry lake bed called Cuddie Springs. Prior dating of charcoal and soil at Cuddie Springs suggested that people and other animals lived there from 36,000 to 30,000 years ago. Scientists had previously noted that there was no good evidence that the extinct animals had lived much beyond 45,000 years ago, shortly after people had arrived.

Evidence in the fossils that the people and animals cohabited for thousands of years comes from measurements of uranium and other elements that were absorbed from ground water during fossilization. In the June 7 Proceedings of the National Academy of Sciences, Trueman and his colleagues report that all the remains contain comparable amounts of these elements. This shared chemical signature confirms that all the bones in the array come from the same time, they assert.