May 7, 2013
Humans Not Responsible For Australian Megafauna Extinction
April Flowers for redOrbit.com - Your Universe Online
An international team of researchers led by the University of New South Wales (UNSW) has completed a major review of the available evidence to conclude that most species of gigantic animals that once roamed the Australian continent disappeared before the arrival of humans.
These findings were published in the Proceedings of the National Academy of Sciences and challenge the claim that humans were the primary cause of extinction for the so-called megafauna in a proposed “extinction window” between 40,000 and 50,000 years ago. Instead, the new study points the finger at climate change as the most likely culprit.
"The interpretation that humans drove the extinction rests on assumptions that increasingly have been shown to be incorrect. Humans may have played some role in the loss of those species that were still surviving when people arrived about 45,000 to 50,000 years ago — but this also needs to be demonstrated," said Associate Professor Stephen Wroe from UNSW, who collaborated with scientists from the University of Queensland, the University of New England, and the University of Washington.
"There has never been any direct evidence of humans preying on extinct megafauna in Sahul, or even of a tool-kit that was appropriate for big-game hunting," he said.
During the Pleistocene era, Australia, New Guinea and Tasmania made up a single continent known as Sahul. Approximately 90 giant animal species inhabited Sahul during this time.
"These leviathans included the largest marsupial that ever lived — the rhinoceros-sized“¯Diprotodon“¯— and short-faced kangaroos so big we can't even be sure they could hop. Preying on them were goannas the size of large saltwater crocodiles with toxic saliva and bizarre but deadly marsupial lions with flick-blades on their thumbs and bolt cutters for teeth," said Wroe.
The researchers concluded that there is only firm evidence that about 14 megafauna species were still alive when Aboriginal people arrived on Sahul. Fossil records of the past 130,000 years show an absence of approximately 50 species of giant animals.
Sahul was periodically characterized by a vast desert. According to recent studies of Antarctic ice cores, ancient lake levels in central Australia, and other environmental indicators, Sahul also experienced an increasingly arid and erratic climate during the past 450,000 years.
The previous claims that humans were the cause of the megafauna extinction have focused on the traditional Aboriginal practice of burning the landscape. Recent research, however, indicates that the fire history of the continent was more closely linked to climate than human activity, and increases in burning occurred long before humans arrived on the massive island continent.
"It is now increasingly clear that the disappearance of the megafauna of Sahul took place over tens, if not hundreds, of millennia under the influence of inexorable, albeit erratic, climatic deterioration," said Wroe.