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A Brisbane researcher is on the verge of debunking claims that Aborigines
were solely responsible for the extinction of Australia's megafauna
by hunting 18,000 to 30,000 years ago.
Queensland Museum's Scott Hocknull, who has just completed his honours
thesis, has discovered evidence of dramatic climate change in Australia
at the time the giant animals are believed to have died out.
"I think we have compelling circumstantial evidence that the
Genyornis extinction date is applicable to the vast majority
of Australian megafauna," said Miller. "There are certainly
no secure dates to refute this supposition."
For almost 4 million years, giant marsupials, birds and reptiles
roamed Australia and the rest of the world. In Australia, the megafauna
reached its maximum size about 100,000 years ago, with the largest
beast a herbivorous wombat-like creature the size of a rhinoceros,
called Diprotodon optatum. Other megafauna included a sheep-sized
echidna, the tree-dwelling marsupial lion, 3m-tall kangaroos and
a 600kg carnivorous goanna. Large Tasmanian tigers and Tasmanian
devils inhabited the mainland.
Last year (2000), scientists found one of the most fearsome Australian
megafauna was a 3m, 300kg, meat-eating duck. The animal had a large
brain and is thought to have hunted large mammals.
Most scientists agree that many megafauna species were still around
when the Aborigines arrived in Australia more than 40,000 years
ago. Australian Museum principal researcher Tim Flannery achieved
some notoriety in 1995 with his book The Future Eaters, that
argued the megafauna species were killed off quite quickly by the
Aborigines when they arrived.
Mr Hocknull has added to evidence showing the great climatic changes
in Australia when the megafauna became extinct. "What I'm finding
with my research is that climate has had a profound effect on the
environment," Mr Hocknull said. "Before we can come to
grips with the effects of humans on the environment, we have to
know what was happening before humans arrived. There is little evidence
to suggest a massive extinction, there's little evidence to suggest
a gradual extinction. What that means is you can't pinpoint any
period of time when the megafauna went extinct. The fact is, people
have jumped on the bandwagon saying humans definitely killed them
off."
Mr Hocknell has been digging up evidence west of Rockhampton (in
Queensland) to look at how far rainforests extended and when they
began to contract to their present levels.
He has round rainforests existed in the Rockhampton region 2 million
to 3 million years ago, and have retracted more than 1000km since.
Within a 10sq km area, he has found evidence of deserts, rain forests
and everything in between, having existed over the past 3 million
years. "That just illustrates how fast changes have taken place,"
Mr Hocknull said.
In the northern hemisphere, glaciers created in the ice ages were
blamed for the extinction of megafauna such as mastodons and giant
elks. In Australia, even though there were few glaciers, similar
environmental factors were responsible for megafauna extinction,
Mr Hocknull argues. "People have always been faced with the
conundrum that if there is no ice how do we know the climate change
was so dramatic," he says. "I'm finding that we went from
rainforest to open woodlands to savannah to desert in a relatively
short period of time."
Mr Hocknell believes that hunting may have been the final threat
that drove the megafauna to extinction, but only after the effects
of climate change.
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