Aussie beasts a pre-history mystery
Onenews 20/8/2001
Flesh-eating kangaroos, hippopotamus-sized wombats and flightless emu-like ducks weighing
1.5 tonnes freely roamed the vast Australian island continent about 100,000 years ago.
Living off eucalypt forests, grasslands and each other, these giant forebears of today's
kangaroos and koalas co-existed for millions of years after the demise of the dinosaurs.
But who or what destroyed the massive marsupials, horned turtles and monster ducks - the
so-called megafauna which used to dominate ancient Australia - remains a mystery.
But new evidence on dates suggests that man's impact on the environment and climate change
may be to blame.
"This is really the first good set of dates and the largest dating review of
megafauna in Australia since the debate began about 170 years ago," the National
Museum of Australia's head of research and development, archaeologist Mike Smith, said.
"We are in the midst of a dating revolution in Australia but the mystery is not over
yet," Smith says. "If it was going to be easy to solve we would have solved it
by now."
Academic furore over this pre-history mystery flared up again with a new exhibition of
lost kingdoms at the National Museum, coinciding with a ground-breaking scientific paper.
Researchers applied a state-of-the-art dating technique to find these huge animals which
disappeared as long ago as 46,000 years.
If the dates are right, this questions earlier theories blaming the last ice age 21,000
years ago, or man hunting the animals to extinction after arriving about 60,000 years ago.
Smith says the new dates pointed to a third theory - the "slow burn" - in which
the megafauna was gradually wiped out by man changing the landscape plus climate changes.
Size counts
While academics are agreed that dinosaurs were probably wiped out after a huge meteorite
hit the planet about 65 million years ago, causing catastrophic cooling and acid rain, the
jury is still out on the fate of Australia's megafauna that followed.
The heyday of giant animals was the Pleistocene era, about 1.6 million to 40,000 years
ago.
It was during this time, when the world cooled and dried, that plants adapted to better
survive long dry spells and became less lush and nutritious.
Plant-eating animals became larger as they ate more to get the nutrition they needed - and
predators in turn grew bigger to cope with their larger prey.
In Africa, these was the origins of the elephant, giraffe and hippopotamus - megafauna
which thrived as humans and the animals evolved together.
North America became home to the woolly mammoth and sabre-toothed cats, which were wiped
out when man arrived about 12,000 years ago. Here archaeologists have found evidence of
kill sites with tools, arrows and skeletons buried together.
Australia, isolated from other continents for 45 million years, developed its own
distinctive fauna, including monster kangaroos, huge lizards and marsupial lions -- of
which 86 percent or up to 55 species were believed to have been wiped out.
Those that vanished included the large short-faced kangaroo, the Procoptodon, which grew
up to three metres tall and 300 kg in weight, with its foot reduced to a single toe
adapted to move quickly across dry, hard land.
The wombat-like Dipotrodon, the largest marsupial known, was nearly four metres long, 1.5
metres tall and weighed 1.5 tonnes.
Smith says archaeologists discovered the existence of these massive creatures that used to
dominate the continent about 170 years ago and initially put their demise down to climate.
Palaeo-ecologist David Horton argues swings in the global climate, including the last ice
age 21,000 years ago, created extreme, arid conditions, wiping out most of these
creatures.
Man blamed
But by the late 1960s another theory emerged.
Evidence pointed to increasingly early human settlement of the continent, turning the
finger of blame to Australia's Aborigines, who first arrived from Asia at least 60,000
years ago.
Zoologist Tim Flannery, director of the South Australian Museum, puts the megafauna's
extinction down to over-hunting by the first humans - "a blitzkreig" - similar
to North America.
"The likely sequence of events is that people arrived in Australia, hunted these
large animals to extinction, this caused a change in vegetation and then a climate
change," Flannery says.
"This is a tight chronological sequence and we really need a clearer idea of when
humans arrived to test this theory."
But the latest dating of the megafauna's extinction has given weight to the
"slow-burn" theory.
Over three years researchers used refined optically stimulated luminescence techniques,
only recently available, to date grains of sand from rock layers bearing intact megafauna
fossils from 28 sites nationwide, revealing burial times of around 46,000 years ago.
These dates suggest the massive creatures and man co-existed for up to 15,000 years,
panning the "blitzkreig" theory.
"Slow-burn" theorists argue the first people modified landscapes, reduced
habitat by fire-stick farming, took the eggs of flightless birds and reptiles, and wiped
out populations by tethering animals to waterholes during droughts.
Palaeontologist Mike Archer, director of Sydney's Australian Museum, says this appears the
most likely theory - while admitting that the debate is far from over.
He argues that most animals made extinct were browsers that ate soft vegetation while
those that survived - like the red kangaroo, emu and wombat - ate grass, suggesting
climate change had an impact on food available, while man also played a part.
"But whatever the sequence of events was, it will take a long time to unravel... and
people in the middle get irate about those jumping on a single cause explanation," he
said.
END OF
REPORT
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