Analyses of ancient fossils suggest that early Australian Aborigines did not wipe out the continent's megafauna in a frenzied hunting rampage. New research conducted by Australian and British scientists reveals that in fact humans and megafauna, such as gigantic three tonne wombat-like creatures, a ferocious marsupial "lion" and the world's all-time biggest lizard, may have co-existed for around 15 000 years.
In Australia, as in America, megafaunal extinctions broadly correlated with the arrival of humans on the island continent. In Australia around 50 outsized species became extinct.
In a study published in the prestigious scientific journal, Proceedings of the National Academy of Sciences USA, a research team including co-authors Dr Judith Field of the University of Sydney and Dr Clive Trueman of the University of Portsmouth establish that some Australian megafauna, including the largest animals, persisted until around 30,000 years ago, coexisting with humans for at least 15,000 years.
By 30,000 years ago the world was in the grip of a major Ice Age, with dramatic changes to climates and ecosystems. "These findings demonstrate that extinction was a gradual process, strongly implicating climate change as the driving mechanism," said Dr Field, 'and the role of humans in this process has yet to be established'. "More broadly, this finding suggests that the spread of modern humans to new regions did not necessarily result in unsustainable hunting and mass extinction of the native fauna."
It has previously been argued that all Australian megafauna went extinct by 46,000 years ago. Because this may be close to the time of human arrival this conclusion has been used to support a model known as 'blitzkrieg', the near instantaneous mass extinction of megafauna through human hunting.
However, Australian fossil megafauna have been found in sites dated at much younger than 46,000 years old. Advocates of a major human role have argued that sediments in these younger sites were disturbed, arguing that previously buried bones could have been introduced into younger sediments. If correct, this would have meant that dates from these younger sites were unreliable.
The best-known site yielding young megafaunal remains is Cuddie Springs, located in south-eastern New South Wales. The research team used a novel chemical forensic test developed by Dr Trueman to test whether bones had been disturbed and moved after death.
"When an animal dies and is buried, elements in the local environment are adsorbed into its bones, forming a permanent 'fingerprint' of the original burial locality. Fossils deposited at different times will have different concentrations of these elements," said Dr Trueman. The team compared the rare earth element (REE) fingerprints of bone fragments found at different levels within the Cuddie Springs site and proved that bones in each layer came from animals that lived and died together. This showed that the sediments were not disturbed, validating much younger dates for the fossil megafauna and demonstrating that humans and megafauna co-existed on the Australian continent for at least 15,000 years.
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