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A map of the Sunda, Sahul and Western Pacific, with arrows showing potential north and south migration routes suggested by genetic analysis. | Credit: Helen Farr and Erich Fisher
A new study of nearly 2,500 genomes may have finally resolved the debate about when modern humans arrived in Australia. Using a diverse database of DNA from ancient and contemporary Aborigines across Oceania, researchers have determined that humans began to settle in northern Australia 60,000 years ago, and that they arrived by two distinct routes.
Experts have long debated when people first arrived in Australiaa feat that required the invention of watercraft. While some researchers have used genetic patterns to support a “short timeline” of 47,000 to 51,000 years ago for arrival, others have organized archaeological evidence and aboriginal knowledge in support of the “long timeline” where the first arrivals occurred 60,000 to 65,000 years ago.
In the new study, published Friday (Nov. 28) in the journal Advances in scienceresearchers analyzed an “unprecedented” dataset of 2,456 human genomes to answer the question of when people traveled from Sunda (the ancient land mass, also known as Sundaland, which included what are today Indonesia, the Philippines and Peninsular Malaysia) chess (a paleocontinent that included present-day Australia, Tasmania, and New Guinea).
“This is the most comprehensive genetic study to date addressing this question and provides strong support for the long rather than the short chronology,” study co-author Martin Richardsan archaeogeneticist at the University of Huddersfield in the UK, told Live Science in an email.
The team’s analysis also revealed two distinct sets of people arriving via northern and southern routes. “This conclusion fits very well with the archaeological and oceanographic/paleoclimatic evidence for an entry into the Sahul around 60,000 years ago,” Richards said.
To reach their conclusions, the researchers used a molecular clock approach, which assumes that mutations in DNA sequences occur at a fairly constant rate over time. By looking at the differences between two DNA sequences, researchers can estimate when those sequences diverged from each other.
In the study, the research team used several statistical methods to analyze mitochondrial DNA (which is passed down through the mother’s line) and Y chromosome data (which is passed down through the father’s line). All of their statistical models were consistent with a date of about 60,000 years ago for settlement in northern Australia.
But the genetic data also revealed two distinct settlements around the same time. One group of people arrived in Australia via the South Sunda (Indonesian Islands), while another came from the North Sunda (Philippine Archipelago).
The two groups were originally part of the same population that moved out of Africa about 70,000 to 80,000 years ago, Richards said, and “we think they separated during the eastward spread into South Asia or Southeast Asia,” possibly 10,000 to 20,000 years before reaching Australia.
“Our results indicate that Aboriginal Australians together with New Guineans have the oldest unbroken ancestry of any human group outside of Africa,” Richards said.
Along the way, these early human pioneers likely interbred with archaic humans such as A tall man, H. luzonensis and even “the hobbit” H. floresiensisaccording to Richards, but it is currently unclear to what extent modern humans interacted with archaic humans in the region.
Adam Brumman archaeologist at Griffith University in Australia who was not involved in the study told Live Science in an email that the research supports the idea that early human movements played a crucial role in the initial population of Sahul. “I’d put my money, if I had it, on the ‘long timeline’ model,” Brumm said.
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This genetic study has broad implications for the antiquity of Aboriginal Australia. “Many Aboriginal people believe they have always been on land,” co-author of the study Helen Farran archaeologist at the University of Southampton in the UK told Live Science in an email.
“These data support a really deep heritage for these communities,” Farr said, and “speak to the close connections people have had with the Land and the Sea of the Sea for at least 60,000 years.” But it also proves that maritime knowledge and skills, not found in the archaeological record, were key to early human survival.