The discovery of a human settlement in Australia dating back 49,000 years has challenged theories about when the world's oldest continued civilization came to the country, the archaeologist who made the find said on Thursday.

Sophisticated tools and bone fragments from the largest ever marsupial were found in a cave high on a cliff in Flinders Ranges, in South Australia, according to archaeologist Giles Hamm.

Scientists working with Hamm's team had determined the age of the site at 49,000 years.

Aboriginal Australians are the oldest continued civilization in the world, descending from the first people to leave Africa, according to a genetic study published by the University of Copenhagen in September.

But the time of arrival of the first Australians is debated among researchers. The consensus view has been that they had arrived 50,000 years ago.

But Hamm said their presence 49,000 years ago at a site at in southern Australia suggested they must have reached northern parts far earlier.

"If people did come 50,000 years ago, it doesn't give them much time to move so far south," said Hamm, referring to evidence of settlement 49,000 years ago.

"There could have been colonization much earlier than the accepted time frame of 50,000 years ago. It could be 55,000 maybe 60,000 years ago."

The site also contained evidence of human interaction with mega fauna, namely the Diprotodon optatum - a marsupial measuring 2 metres in height and weighing more than 2,500 kilograms.

Scientists have previously puzzled over how humans had interacted with them. But the presence of bones from juvenile animals in a cave on a cliff suggests they had been hunted, said Gavin Prideaux, palaeontologist, at Flinders University in South Australia.

"Those animals weren't built to climb up a cliff into the settlement, the only way they could have got there was through human agency," said Prideaux.