Aborigines' ancestors took the fast track to Australia ... but why?

Lambert said the first people reached Australia within 10,000 years of leaving Africa. Photo / Shaana McNaught

A study into the DNA of Aboriginal Australians has shed new light on when their ancestors left Africa and revealed extensive genetic diversity between west and east coast indigenous populations.

Researchers from Griffith University formed part of the first extensive investigation into Aboriginal DNA which found early Australians left Africa somewhere between 51,000 and 72,000 years ago.

The study, published in Nature yesterday, found evidence of a single "out-of-Africa" event, Griffith University professor David Lambert said, setting out in the long march toward Australia virtually straight away, compared to those that would go on to populate Europe. "They did it fast," Lambert said.

"We know now that there were Aboriginal people with very highly developed cultures here in Australia before people ever got to Europe."

Lambert said the first people reached Australia within 10,000 years of leaving Africa.

The study, which analysed the DNA of 83 indigenous people, also discovered a large genetic difference between the east and west coast Aboriginal populations.

"That level of difference between the east and west is kind of equivalent to the level of difference that you find between indigenous people of North America and Siberians," Lambert said.

"They are genetically rather different to one another and that's a really important point."

The research also revealed that Australian Aborigines and Papua New Guineans separated long before the formation of the Torres Strait, which cut off Australia from Papua New Guinea.

Lambert said the evidence suggested the populations separated around 37,000 years ago, almost 30,000 years before the land-bridge was washed away between Australia and Papua New Guinea.

The separation of the populations, who moved down from Africa together, is believed to have occurred somewhere in South East Asia.

Lambert said what the DNA could not explain to researchers was why a stream of early humans walked out of Africa, through Asia and down into Australia thousands of years later. "What made them keep going and going and going? I don't know, it's a fundamentally human thing."

Study co-author and Otago University biological anthropologist Professor Lisa Matisoo-Smith said the findings showed collaborations could piece together whole pictures.

"This is an exciting study, not only in what it tells us about the origins, settlement process and history and subsequent diversification of the indigenous people of Sahul (Australia and New Guinea) beginning around 50,000 years ago, but by the fact that it sets a standard for the collaboration of geneticists, archaeologists, linguists and Aboriginal elders and community representatives," she said.

"It demonstrates how western science and traditional knowledge can be complementary and collaborative."

- AAP