Aborigines killed Australia's giant animals: study

By Sid Astbury Jul 9, 2005, 11:19 GMT

Sydney - It's an argument that Australian scientists have wrangled over for decades: was it aborigines arriving on the continent about 50,000 years ago that killed off the megafauna by burning their habitat or was climate change the culprit in the extinction of 300-kilogramme kangaroos and other giant animals?

It's been a debate pitting mighty intellects and egos that at times has threatened to spill over into unseemly fist fights outside the laboratory.

But a rich new study of ancient emu eggs and wombat teeth has tipped the balance in favour of those who subscribe to internationally regarded botanist Tim Flannery's thesis in the book "The Future Eaters".

Accordingly, mankind rather than meteorology killed off the fearsome 100 kilogramme Genyornis flightless bird and the dopey- looking, grass-eating, 1-tonne Diprotodon.

"It does indeed validate my argument in 'The Future Eaters'", Flannery, the director of the Museum of South Australia told Deutsche Presse-Agentur dpa.

He added: "I would say, though, that I'm not certain that it was human-lit fires that caused the change. Instead, as I outline in 'The Future Eaters', I think that changes in nutrient recycling, and changes in vegetation structure following megafaunal extinction, that may have triggered the changes."

The new study is by American geochronologist Gifford Miller of the University of Colorado and Australian geologist John Magee of Canberra's Australian National University.

Published in the latest issue of the learned journal Science, their paper is based on carbon isotope testing on eggshells and teeth going back 140,000 years. They found that diet was consistent until about 50,000 years ago when man arrived on the continent. The diet changed and around 50 species of vertebrates started to die out.

"We speculate that human firing of landscapes rapidly converted a drought-adapted mosaic of trees, shrubs and nutritious grasslands to the modern fire-adapted desert scrub," they wrote. "Animals that could adapt, survived. Those that could not became extinct."

They declared there was no major climate change underway at the time. They also ruled out the possibility that hunting, and perhaps diseases introduced by the new arrivals, could account for the loss of the megafauna. If only spears and disease were to blame, there wouldn't have been a change in diet, they argue.

Aborigines might have set the fires to burn off grass, to flush out game or for smoke signals. There would also be fires lit by lightning strikes just as there are today.

Professor Mike Archer, dean of science at the University of New South Wales and a former director of the Australian Museum in Sydney has become Flannery's ally in the debate.

"Extinctions have to happen," Archer said. "Some animals are just not going to adapt quickly enough (to changes in their habitat)."

Flannery says that the Australian continent has been transformed by humans more dramatically than any other. In megafauna terms, once as rich and varied as Africa, it was robbed of all its big animals and left with oddities like the flightless emu and the kangaroo.

"And the big question is really what happened to these creatures," Flannery said. "Well, I think they might have gone on and on if it hadn't been for a new species developing in far off Africa - and that species was us."

His argument that the arrival of the first Australians unleashed a wave of extinctions across the continent is fiercely contested.

Among the gainsayers is archaeologist Judith Field from the University of Sydney.

"There were a range of factors aiding in the extinction of the megafauna, but I think that climate was probably the driving force," she said. "I don't think that humans were the main agent, because there is evidence of co-existence between humans and megafauna over long periods of time - which knocks Flannery's blitzkrieg theory on the head."

This latest body of research certainly tilts the balance in Flannery's favour.