Aborigines blamed for Australian extinctions

[Brian G Turner]

There was a recent report in New Scientist again blaming the arriving humans, to the Australian continent, for the extinction of the megafauna - principly through "firing" the landscape. In simple terms, the Aboriginal peoples of Australia are blamed with burning the continent clean of larger animals.

One thing troubles me here though - firstly, the extinctions are not being directly attributed to the actions of humans - the simple inference is this: the arrival of humans and the extinction of the megafauna both occurs at the same short geological span...therefore humans wiped out the megafauna.

I'm sure this has political consequences, not least because of the various legal battles over land ownership and compensation claims in the Australian courts.

Not elast because the two events - arrival or humans and extinction of the megafauna - simply cannot be logically linked. There is no way to establish any form of relationship between the two.

My personal criticism is that the two events are more likely a consequence of a third variable - dramatic climate change. This addresses the reason of why Australia was suddenly able to be settled (change in Ocean currents, etc?) which in itself implies serious ecological damage to Australia.

That removes the politics from the equation. But is it right?

That's impossible to tell without any climatological records for the geography and geological period.

But, equally, it's wrong to make any assertion of a cause and effect link between two variables, without far more substantive evidence. And, currently, the "humans wiped out the megafauna" idea simply hasn't got anything like that.

Simply a cause of personal concern, which is why I raise it as a topic - not least, of the short-term thinking involved in the conclusions of too many scientific studies...but also the possibility of scientific thinking being hi-jacked by political (even racially motivated) ideologies.

Here's the latest New Scientist article on the issue:

http://www.newscientist.com/news/news.jsp?id=ns99994028

Big beast extinction blamed on prehistoric fire starters

Prehistoric fire starters may have unwittingly killed off the big beasts that once roamed Australia. Analysis of ancient eggshells suggests that the animals suddenly became extinct about 50,000 years ago because people burned up their habitat.

Australia's giant carnivorous kangaroos, seven-metre-long lizards, marsupial lions and enormous flightless birds all died off between 45,000 and 55,000 years ago. Most scientists agree that people arrived in Australia somewhere between 50,000 and 55,000 years ago.

This suspicious coincidence of timing has led some to conclude that overzealous hunting by humans caused the extinctions. But others claim that we could not have cleared the entire continent of so many species in such a short time.

Geologist Gifford Miller of the University of Colorado at Boulder and an international team analysed hundreds of eggshell fragments of an extinct flightless bird called Genyornis, dating from 130,000 to 50,000 years ago. They compared them with the eggshells of emus, dating from 130,000 years ago to the present day.

Carbon isotopes in the eggshells reveal what the birds were eating when they laid the eggs. The team found that emus consumed either grasses, shrubs and trees, or a mixture, until 50,000 years ago, when grasses all but disappeared from their diet.

But Genyornis ate a narrow diet that always included grass - and then died out, Miller told an International Union for Quaternary Research meeting in Reno, Nevada, last week.

Climate change is too slow to have killed off most of the grasses, argues Miller. The best explanation is that people began burning the landscape.

Bert Roberts of the University of Wollongong in New South Wales, Australia, says that giant marsupials became extinct around the same time, and the reason could be that burning affected the entire ecosystem.