The most comprehensive genomic study of Indigenous Australians to date has revealed modern humans are all descendants of a single wave of migrants who left Africa about 72,000 years ago.

Key points: Aboriginal and Papuan ancestors left Africa around 72,000 years ago

Aboriginal and Papuan ancestors left Africa around 72,000 years ago Arrived on supercontinent 'Sahul' around 50,000 years ago

Arrived on supercontinent 'Sahul' around 50,000 years ago By 31,000 years ago, most Aboriginal communities were genetically isolated from each other, giving rise to great genetic diversity

It confirms modern Aboriginal Australians are the descendants of the first people to inhabit Australia — a claim that has previously been the subject of debate.

And the genetic information also shows Aboriginal people living in desert conditions may have developed unique biological adaptations to survive the arid conditions.

The findings are contained in one of three papers published today in Nature that look at the dispersal of modern humans from our evolutionary birthplace in Africa to Europe, Asia and Oceania.

To date, academics have debated whether we all share the same ancestors from a single mass migration event, or that the dispersal took place in distinct waves at different times.

The long history of human occupation of Australia has been cited as evidence that Papuans and Australians stemmed from an earlier migration than the ancestors of Eurasian peoples.

However, taken together, today's papers use the genetic information of people from 280 diverse populations from largely understudied regions of the world to support the single wave theory.

Migration from Africa to Australia

The Aboriginal study, led by Professor Eske Willerslev of the University of Cambridge, was undertaken with the collaboration of elders and leaders of various Indigenous communities.

The international team sequenced the genome of 83 Aboriginal Australians from the Pama-Nyungan-speaking language group, which covers 90 per cent of the continent, and 25 Highland Papuans.

Australian co-author, Dr Michael Westaway of Griffith University said the study showed evidence only for one colonisation event in Australia, and a continuity of occupation from that genomic signature for 40,000-odd years.

It reveals Papuan and Aboriginal ancestors left Africa around 72,000 years ago and then split from the main group around 58,000 years ago.

They reached the supercontinent of 'Sahul' that originally united Tasmania, Australia and New Guinea around 50,000 years ago, picking up the DNA of Neanderthals, Denisovans and another extinct hominin along the way.

Papuans and Aboriginals then split around 37,000 years ago, long before the continents were finally cut off from each other around 8,000 years ago.

Dr Westaway said this was "a bit of a surprise" as it was much earlier than a lot of people expected.

The researchers suggest although Australia and New Guinea remained connected until the early Holocene, the flooding of the Carpentaria basin and its increasing salinity may have promoted population isolation.

Professor David Lambert, who was also involved with the study, said the point of entry into Australia was still unclear, but the data revealed an expansion of people from Cape York.

"What our data shows is not so much that necessarily there was an entry point into the continent via Cape York, but what it shows us is that there was a divergence of a whole lot of people from Cape York, we think about 30,000 years ago," he said.

Remarkable genetic diversity between east and west

Study lead author Professor Eske Willerslev talks to Aboriginal elders in the Kalgoorlie area in southwestern Australia ( Supplied: Preben Hjort, Mayday Film )

The study also revealed remarkable genetic diversity between Aboriginal people of the east and west of Australia.

Dr Westaway said this could be connected to the last Ice Age around 30,000 to 20,000 years ago.

"The onset of the last glacial maximum creates this huge expansion of the arid core in Australia and a dramatic reduction in gene flow between the east and west of the country," he said.

Interestingly the genome sequencing also showed Aboriginal Australians adapted biologically to the environment, a trait Dr Westaway said was reinforced by their long occupation of the continent.

In particular, the evidence suggested desert groups were able to withstand sub-zero night temperatures without showing the increase in metabolic rates observed in Europeans under the same conditions.

"When people first arrived 50,000 years ago arid Australia wasn't like it is today," Dr Westaway said.

"People have changed and adapted over deep time as the country has ... we just don't see that in any other Homo sapiens populations.

"There is greater genetic diversity in Aboriginal people living in the east and west of Australia then there is between people living in Siberia and the Americas.

"[And] that great genetic diversity in Aboriginal populations reflects the huge amount of time they have occupied the continent."

More work needed to clarify gaps

Dr Westaway said the study presented a "lot of new challenges to our current knowledge" about the population history of Australia.

"We only have 83 genomes representing the population history of an entire continent ... I think there is so much more that needs to be done, but most importantly working and partnering with Aboriginal peoples."

In particular, he said, it would be good to sequence the genome of Aboriginal people in the non-Pama language groups.

"Arnhem Land and the Gulf of Carpentaria are non-Pama-speaking language groups so the story could be very different there and could fill in the gaps in this model of dispersion," he said.

Professor Alan Cooper, at the Australian Centre for Ancient DNA, who was not involved in the study, agreed the researchers needed more information.

He said dates within the paper were contradictory as it showed inter-mixing with another group of ancient humans known as Denisovans around 44,000 years at a time when the ancestors of Aboriginal Australians were already meant to be in Sahul.

"They say there is only one invasion of [Sahul] and that happens around 50,000 years ago, but then they go on to say Aboriginal Australians have genetically mixed with Denisovans at 44,000 years.

"So how can you be in [Sahul] after a single invasion, yet 6000 years later you mix with another extinct hominim that is not in Australia?

"This is early days and the first genomic data we've got from this area. Clearly these processes are much more complex than they have modelled, and I think that the dates are wrong as a result.

"All three genomic studies show a single movement Out of Africa, a single invasion of Sahul, but then after that the events in [Sahul] aren't very well resolved."

Important collaboration with Aboriginal community

Indigenous elder Thomas Wales and Griffith University Senior Research Fellow Michael Westerway on a beach at Mapoon in Cape York. World-first genetic research into aboriginal Australians has found that most of the country’s indigenous population was founded from a single colonising event which began in Cape York in far north Queensland more than 30,000 years ago. ( ABC News: Tom Forbes )

Dr Westaway said it was important the genomic information gleaned from the study would remain the property of the Indigenous communities.

Co-author Ms Colleen Wall, a senior Aboriginal woman of the Dauwa Kau'bvai nation from the Mary River catchment area in south east Queensland said she was pleased women were well represented as collaborators in the study, as in the past academics had mainly worked with men.

"It has been difficult over the years for Aboriginal women to maintain their senior status in a mainstream society and be invited to sit at the table to negotiate our issues," she said.

Ms Wall said the study was very important to Aboriginal people.

"As a society we already believe that we are the oldest race on Earth, and from my point of view this research goes some way towards proving that," she said.

Ms Wall said the genetic information could help in properly repatriating Aboriginal remains.

"This information coupled with the technology now used to assist in identifying where our human remains come from exactly, is exciting," Ms Wall said.

"It means that all our old people who are still in collecting institutions across the world may be able to come home and be on their own specific country, not in a museum somewhere in Australia.

"Placing them as close to country as possible will settle them down."

Mr Thomas Wales, an Indigenous elder from the Cape York community of Mapoon and co-author, said the study helped him "learn more about my people, myself and my land."

"We have an oral history, that everyone knows, and you can lose all of your oral (history)," said Mr Wales.

"Science, DNA and carbon dating … you can keep hold of things. Tell us about our past."

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