During the Pleistocene period (2 million to 10,000 years ago), Australian fauna was as diverse and impressive as the fauna of the African savanna today.

On the Australian grassland were roaming large herds of giant kangaroos (image), 3 m (10 feet tall) and weighing 200 kg, two tonnes giant wombats and other large herbivorous species.

The abundant fauna of wild beasts sustained large carnivorous species like giant goannas (7 m long, 600 kg weight), 5 m long land crocodiles, leopard sized marsupial lions (related to wombats) or 500 kg flightless birds.

But this entire fauna of giants vanished 40,000 years ago.

People, thought to have entered Australia 50-40,000 years ago, were blamed for the extinction of the megafauna.

Now, researchers from the Queensland University of Technology have gathered proof that the great extinction might have been produced by a large drought.

Investigating the fossil-rich Darling Downs area of south-east Queensland, the scientists discovered that the fossils belonging to giant fauna roaming the area to the end of Pleistocene presented signs of drought-stress when they died.

"What makes this research so relevant to climate change theories today is that the profile of the fossil kangaroo populations is identical to that of a modern drought-stressed kangaroo mob," said Dr. Gilbert Price.

"It provides, for the first time, evidence which suggests that the megafauna kangaroos were greatly affected by a series of catastrophic droughts."

"These animals of the prehistoric Australian bush were the largest of their time and included gigantic wombats the size of cars, kangaroos that reached almost 2.5 meters tall, and massive emus and goannas (monitor lizards)."

"But if we can understand how those animals responded to the massive droughts and climate change events of the past, we might be able to go some way in predicting the effects of future climate changes and its impact on the way that we manage and conserve the precious habitats and wildlife of the Australian bush ".

The fossils analysis at the Darling Downs site does not support the theory of megafauna extinction being caused by human hand.

"Some scientists believe in the 'blitzkrieg' megafauna extinction hypothesis which blames humans for over-hunting these giant marsupials," said Price.

"If that was the case, these fossils dating back thousands of years would show the animals dying out at the same point in time. But they don't. These layers of fossils buried at a single site under the Darling Downs show a progressive, three-stage extinction over time that relates to periods of climate change."

Geological clues point to a semi-arid environment 40,000 years ago at the Darling Downs rather than to a subtropical or tropical grassland.

"Sedimentological information shows that the Darling Downs was experiencing repeating cycles of wet and dry conditions, resulting in droughts and periodic flash flooding from storms, during the time when the megafauna populations were declining," said Dr. Gregory Webb.

"The research found no evidence of humans being involved in the accumulation of fossils in the catchment at the time of deposition, but is perfectly consistent with their decline being caused by increasing aridity."

"So it's most likely that Australia's giant kangaroos and other megafauna in this area were driven to extinction by the hands of Mother Nature."