A new study of about 2,500 genomes may finally settle the debate over when modern humans arrived in Australia. Using a diverse database of DNA from ancient and modern Aboriginal people across Oceania, researchers found that people began settling in northern Australia by 60,000 years ago, arriving via two different routes.
Experts have long debated the date when humans first arrived in Australia, which required the invention of the watercraft. Some researchers are using genetic models to support a “short chronology” of arrival between 47,000 and 51,000 years ago, while others marshal archaeological evidence and Aboriginal knowledge to support a “long chronology” of first arrivals occurring between 60,000 and 65,000 years ago.
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“This is the most comprehensive genetic study to date that has addressed this question, and provides strong support for a long rather than a short time span,” study co-author Martin Richards, an archaeogeneticist at the University of Huddersfield in the UK, told Live Science in an email.
The team’s analysis also revealed two distinct groups of people who arrived via the northern and southern routes. “This conclusion agrees very well with archaeological and oceanographic/palaeoclimatic evidence for entry into Sahul about 60,000 years ago,” Richards said.
To reach their conclusion, the researchers used a molecular clock approach, which assumes that mutations in DNA sequences occur at a roughly constant rate over time. By looking at the differences between two DNA sequences, researchers can estimate when the sequences diverged from each other.
In this study, the research team used several statistical methods to analyze mitochondrial DNA (inherited through the maternal lineage) and Y chromosome data (inherited through the paternal lineage). Their statistical models all agreed on a date of about 60,000 years ago for the northern Australian settlements.
But genetic data also revealed two distinct settlements around the same time. One group arrived in Australia via the South Sundas (Indonesian Islands), while another group came from the North Sundas (Philippine Islands).
Richards said the two groups were originally part of the same population that migrated from Africa about 70,000 to 80,000 years ago, and likely split during dispersal into east, south or southeast Asia 10,000 to 20,000 years before reaching Australia.
“Our findings show that Indigenous Australians, like New Guineans, have the oldest continuous ancestry of any group outside Africa,” Richards said.
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Along the way, these early human pioneers likely interbred with archaic humans such as Homo longi, Homo luzonensis, and even the Hobbit’s Homo floresiensis, Richards said, but it’s currently unclear how much modern humans interacted with the region’s ancient humans.
Adam Blum, an archaeologist at Australia’s Griffith University who was not involved in the study, told Live Science in an email that the study supports the idea that early human migration played an important role in the early people of Sahul. “If I had the money, I would put it into a ‘long timeline’ model,” Blum said.
This genetic research has far-reaching implications for the ancient history of Australia’s Aboriginal people. “Many Aboriginal people believe they have always been rural,” study co-author Helen Farr, an archaeologist at the University of Southampton in the UK, told Live Science via email.
“This data confirms the very deep heritage of these communities,” Farr said, “and tells us that people have had a close relationship with their countryside and maritime country for at least 60,000 years.” But it also proves that navigational knowledge and skills not found in the archaeological record were key to early humans’ survival.
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