Claims that Aborigines had a hand in the extinction of Australia’s gigantic prehistoric animals have been challenged in a new study.
Most of the 60 gigantic animal species supposedly wiped out by the first Australians had probably had died out 85,000 years before humans arrived in Australia, says the study, soon to be published in the international journal Quaternary Science Reviews.
In a new analysis UNSW paleontologist Dr Stephen Wroe and his Sydney University colleague, Dr Judith Field, demonstrate that the disappearance of the majority of these Ice Age leviathans corresponded with a well-documented climatic catastrophe - the Penultimate Glacial Maximum – starting about 130,000 years ago.
Temperatures in Australia plummeted at the time to as much as 9 degrees C lower than today.
As well, long-term climatic records suggest that Australia has been subjected to increasingly arid and erratic conditions over the last 400,000 years or more. That trend amounts to a climatic "smoking gun" to explain the extinctions of the megafauna and has been ignored by advocates of human causation, Dr Wroe says.
“In recent years some scientists have become wedded to the suggestion that all megafauna went extinct by 46,000 years ago,” he says.
“This inference has been presented as key support for the notion that early Aborigines drove extinctions, because this date precedes the most extreme climate change documented in recent prehistory, the Last Glacial Maximum between 30,000 and 19,000 years ago.
“There have been at least 30 glacial maxima [Ice Ages] over the last two million years – if Ice Ages drive extinctions then why didn’t the megafauna go extinct previously?
Dr Wroe and Dr Field contest the notion that all megafauna were extinct by 46,000 years ago, but point out that even if they accepted that claim, Aborigines could hardly be accused of exterminating species that were separated from them by tens of millennia.
“At present only 21 species can be placed within 85,000 years and only 8 within 1,000 years of human arrival,” the researchers say.
“So, even hypothetically, a convincing case could be made for human involvement with respect to only 13% of those species.
“Unfortunately for proponents of human causation not only is there not a single Australian archaeological site demonstrating that humans ever killed megafauna. Only one clearly shows that they even co-existed in the same space and time. This site - Cuddie Springs, in northern NSW- is younger than 46,000 years and has consequently been dismissed by those seeking to establish a human role.”

Supporters of human causation also point to the fact that colonising humans in more recent times have driven extinctions on relatively small islands, the largest indisputable case being New Zealand.
Yet the ecology of continents and islands is very different, with island species being far more vulnerable, the authors note. They argue that the impact of people such as the Maori cannot be sensibly compared with that of Aboriginal societies at least 40,000 years more ancient.
“When the Maori first encountered the giant moa they met a bird that had never known any terrestrial predator,” says Dr Wroe. “It is also clear that the Maori significantly modified these new found habitats and brought with them damaging feral animals, such as dogs and pigs.
“In contrast, Australian megafauna had long known formidable predators such as the marsupial lion and giant goanna; there is no hard evidence suggesting that the first Aborigines significantly modified their habitats; and they brought no ferals with them. The dingo was a far more recent addition brought by Indonesian seafarers.”
Although many scientists believed that humans drove the Australian extinctions , there was no direct evidence for that conclusion.
“To reach this conclusion we must unquestioningly accept that most megafauna were actually here when Aborigines arrived and that the last two Ice Ages were no more severe than those that preceded them,” says Wroe
“But in the absence of any hard data to substantiate the claim this amounts to an expression of faith, not fact.
“Our results suggest that an earlier Ice Age accounted for most extinctions long before human colonisation and that Ice Ages prior to this did not cause major extinctions simply because they were not as extreme as the two most recent ones.”
Drs Wroe and Field accept that their own analysis is not proof positive of wholly climate-driven events.
“It remains possible that a complete account will ultimately testify to some combination of human and climatic influence,” they says.
With few Ice Age sites reliably dated, they conclude that there is too little hard data for anyone to presume that they have the answer.
However, they suggest that “… if taken seriously, increasingly shrill claims to have proven human causation may stifle not only scholarly debate, but research into the impacts of climate change over deep time, an area that many see as being of particular relevance in light of current climate predictions”.
Now more than ever we need to understand how climate affected populations in the deep past if we’re to understand future impacts on biodiversity”.


The full online article is here


Stephen Wroe's homepage is here

Judith Field's homepage is here