Man may have killed off Tasmania's biggest beasts

Most giant animals disappeared from mainland Australia soon after humans arrived about 46,000 years ago, and there is continuing debate as to whether this was caused by people or changes in climate.

However, on Tasmania the massive creatures - known as megafauna - were thought to have died out before the arrival of humans, lending support to the idea that climate change was the culprit.

Now a team of Australian and British scientists has published the first evidence that Tasmania's megafauna were still alive when humans settled the island, pointing the finger of blame back at our ancestors.

Using advanced fossil-dating techniques, they discovered that a giant kangaroo-like creature, Protemnodon anak, survived until at least 41,000 years ago - up to 2000 years after humans walked across a land bridge from the mainland to Tasmania.

"This, I think, really adds greater credibility to the idea that it was the presence of humans - rather than any particular changes in climate - that led to these extinctions," said Macquarie University's Professor Tim Flannery, a co-author of the paper, published today in the Proceedings of the National Academy of Sciences.

Fellow author, Professor Bert Roberts of the University of Wollongong, says human hunting could have wiped out the animals relatively quickly. "If you just pick off the juveniles . . . you actually drive the species to extinction within a couple of hundred years," he said. "They are very slow breeders, and on an island setting, there's nowhere to run."

The megafauna of Tasmania included a sloth-like creature known as Palorchestes azael that weighed half a tonne.

There also were giant marsupials that resembled rhinoceroses and leopards, and an egg-laying mammal similar to the echidna.