The most comprehensive genetic study of Indigenous Australians to date indicates that the group is the oldest continuous civilisation on Earth, dating back more than 50,000 years ago – and that modern Indigenous Australians are the descendants of the first people to settle Australia.
The new paper, alongside two others published today in Nature, reveal important information about the origins and migratory history of our species, including insight into the common ancestors of all non-African humans alive today.
According to the DNA results in two of the papers, most modern Eurasians are descended from a single wave of migrants that left Africa around 72,000 years ago.
From that original migration, Indigenous Australians and Papuans (ancestors of indigenous people from New Guinea) split off and ventured across the sea around 58,000 years ago before arriving in Australia roughly 50,000 years ago – and were likely the first humans to cross an ocean.
“This story has been missing for a long time in science,” one of the researchers, Eske Willerslev, an evolutionary geneticist from the University of Copenhagen in Denmark, told Hannah Devlin at The Guardian.
“Now we know their relatives are the guys who were the first real human explorers. Our ancestors were sitting being kind of scared of the world while they set out on this exceptional journey across Asia and across the sea.”
The Papuan and Australian indigenous populations seemed to split from each other around 37,000 years ago, before the continents were separated.
Indigenous Australians remained almost entirely isolated until around 4,000 years ago – but in the thousands of years it took them to get to Australia, it seems they came into contact with a range of other hominin species, and around 4 percent of their genome comes from an unidentified hominin relative.
To come to this conclusion, the international team of scientists sequenced the genomes of 25 Papuans and 83 Indigenous Australians from the Pama-Nyungan-speaking language group, which covers around 90 percent of Australia.
A second study led by a Harvard Medical School team, and also published today in Nature, mapped the genomes of 300 people from 142 diverse populations worldwide, looking for any genetic changes associated with the evolution of modern human traits, such as painting cave art and the use of sophisticated tools – but didn’t find any.
“There is no evidence for a magic mutation that made us human,” Willerslev told The Guardian.
While the results are compelling, they leave a lot of blanks to be filled in – and not everyone is convinced that they settle the question of how we migrated out of Africa.
Even though two of the genetic studies support one single wave of migration out of Africa, the third paperthat came out today has evidence of at least two migrations out of Africa.
Led by Luca Pagani, an biological anthropologist from the Estonian Biocentre in Tartu, the study did also find evidence of a huge migration of humans about 75,000 years ago, but it also found evidence of an earlier migration around 120,000 years ago – which his team says accounts for around 2 percent of modern Papuan genomes.
The key to getting a clearer picture of what went down in our ancient history will now be to combine genetic evidence with archaeological evidence – something the three new studies didn’t fully explore.
“Human history is this really fascinating and complex puzzle, and genetics can tell us about some of the pieces,” Joshua Akey, an evolutionary geneticist from the University of Washington, who wasn’t involved in any of the studies, told Rachel Becker from The Verge.
“It’s really important to integrate information from as many other disciplines as possible.”
Some scientists have also already cast doubt on how accurate the genetic timeline is.
“I don’t think this study will be the final word on this issue, as recent discoveries in places like China cast a big shadow over it,” Darren Curnoe, from the University of New South Wales (UNSW) in Australia, told Rae Johnston from Gizmodo.
“I guess it all comes down to the assumptions you make in your genetic clock, and these are very much up for grabs at the moment, making molecular dates like these rather prone to error.”
So the case definitely isn’t closed on how humans first ventured out of Africa and populated the rest of our planet, but if nothing else, this new research serves as an important confirmation that Indigenous Australians really were the first to inhabit the continent – something that has, in the past, had doubt cast on it.
“This study confirms our beliefs that we have ancient connections to our lands and have been here far longer than anyone else,” Aubrey Lynch, an Indigenous elder from the Goldfields area in Western Australia, told Devlin.