[ExI] Humans caused Aussie megafauna extinction

[Damien Broderick]

Humans caused Aussie megafauna extinction
Friday, 29 January 2010

<http://www.cosmosmagazine.com/news/3261/humans-drove-australian-megafauna-extinction>

by Gemma Black
Cosmos Online


SYDNEY: The key anomaly in the Australian megafauna debate has been 
resolved, and "if people hadn't arrived in Australia, we'd still have 
the giants of yesteryear to admire," researchers report.

Giant Australian marsupials, reptiles and flightless birds went extinct 
between 45,000 and 60,000 years ago. The reason behind the extinction of 
Australian megafauna has been the subject of debate for decades, said 
the lead author of the study, Richard Roberts from the University of 
Wollongong near Sydney, Australia.

One theory is that Australian megafauna, including three-metre-high 
kangaroos and flightless birds weighing half a tonne, was driven to 
extinction at around the same time that humans arrived.

The other theory is that the onset of the latest ice age, which peaked 
around 21,000 years ago, caused the extinction of the megafauna.

Cuddie Springs anomaly

While several archaeological sites support the first theory, one site at 
Cuddie Springs stood out as an anomaly. The study, published in the 
journal Science, showed that the supposedly undisturbed fossils had 
actually been moved, resolving the anomaly.

Cuddie Springs, in western New South Wales, has long been promoted as a 
site containing both megafauna fossils and stone tools in the same 
sedimentary layer.

By dating the surrounding sediments researchers found that the fossils 
and tools could be as young as 30,000 years - suggesting that humans and 
megafauna co-inhabited the continent for an extensive period of time.

However, a geologist from the Australian National University, Rainer 
Grun, recently dated the fossils directly, using a combination of 
electron spin resonance (ESR) and uranium-series (U-series) dating.

Cuddie Springs deposits had moved

The results, published online in the journal Quaternary Science Reviews, 
showed that some of the supposedly undisturbed fossils in the 
sedimentary layer were actually more than 450,000 years old, suggesting 
that they had been reworked from much older deposits.

"It seems that none of the fossils in the archaeological levels at 
Cuddie Springs are younger than the extinction window between 51,000 and 
40,000 years ago," said Richard. "This pulls Cuddie back into line with 
all other sites on the continent, and removes its 'anomaly tag'," he said.

"Rainer Grun leads the world in ESR/U-series dating, so his findings for 
Cuddie Springs deserve serious consideration," Richard said.

Extinction is complicated, experts warn

However, Danielle Clode, a zoologist from the University of Melbourne, 
and author of Prehistoric Giants: the Megafauna of Australia, thinks it 
might be misguided to suggest that there was just one cause behind the 
extinction of Australian megafauna.

"I know how incredibly difficult it is to understand what exactly is 
driving species extinction today, even when we can watch and study the 
process directly," she said.

"I think it is very unlikely that the decline of the megafauna was 
caused by a single factor, and even less likely that we are ever going 
to be able to work out what did drive their extinctions, in anything 
other than the most general terms."