New Study Challenges 65,000-Year Timeline for First Humans in Australia, But Debate Remains Unsettled

A newly published research paper has reignited debate about when humans first set foot in Australia, proposing a later date of arrival that contradicts longstanding archaeological evidence. While the genetic model behind this revised timeline has garnered attention, many experts remain unconvinced that it should overturn decades of archaeological research.

In a study released this week in 'Archaeology in Oceania', archaeologists Jim Allen of La Trobe University and James O’Connell of the University of Utah argue that modern humans could not have occupied Australia before about 50,000 years ago. Their reasoning hinges on recent DNA studies suggesting that Homo sapiens only interbred with Neanderthals during a single window between roughly 50,500 and 43,500 years ago.

Because all living non-African human populations, including Indigenous Australians, carry small amounts of Neanderthal DNA, Allen and O’Connell contend that Australia’s first settlers must have arrived after these interbreeding events, not before.

“Archaeological evidence of the initial colonisation of Sahul [the ancient supercontinent that included Australia, New Guinea and Tasmania] largely aligns with this genetic timeframe,” O’Connell told 'Live Science'. “Most sites indicate human presence between 43,000 and 54,000 years ago.”

A Contested Site in the Northern Territory

Yet a major sticking point remains: the Madjedbebe rock shelter in Australia’s Northern Territory, long considered the country’s oldest archaeological site. In 2017, researchers announced that stone tools and ochre “crayons” excavated there dated back at least 65,000 years.

Critics of this interpretation have pointed to challenges in dating the site accurately. The sandy sediments in the shelter are prone to shifting, potentially causing artefacts to sink deeper over time and appear older than they truly are. Although the 2017 research team employed rigorous measures to address this possibility, the dating remains controversial.

“If the data from Madjedbebe are correct, then the people who occupied it might not be ancestral, to any significant degree, to modern Sahul populations,” O’Connell said.

Scepticism from the Archaeological Community

Several archaeologists have voiced reservations about the new model’s reliance on genetic assumptions. In a commentary also published in 'Archaeology in Oceania', Peter Veth of the University of Western Australia questioned whether molecular “clocks” used to estimate genetic divergence are yet robust enough to supersede archaeological evidence.

“Both archaeological and molecular dating of Sahul are still in an early stage of development,” Veth wrote. “Can we rely on current assumptions underlying these molecular clocks to test Australian archaeological evidence?”

Adam Brumm, an archaeologist at Griffith University, highlighted findings from neighbouring Southeast Asia that suggest modern humans were engaged in sophisticated cultural practices earlier than Allen and O’Connell’s timeline allows. In Sulawesi, Indonesia, for example, rock art has been reliably dated to at least 51,200 years ago.

“Remembering that we only have minimum ages for rock art, I think there is a very real possibility that the people who created the earliest artworks from Sulawesi were part of the same broader cultural group that went on to colonise Sahul some 65,000 years ago,” Brumm wrote.

A ‘Behavioural Revolution’

A further point of contention is the idea that a sudden “Palaeolithic Revolution” occurred around the time modern humans met Neanderthals, sparking the rapid spread of complex behaviours, such as like seafaring and elaborate tool-making, across Eurasia and eventually into Australia.

O’Connell and Allen maintain that these behavioural shifts coincided with the dispersal of modern humans beyond Africa. But Huw Groucutt and Eleanor Scerri, archaeological scientists who also contributed commentary, challenged this narrative, arguing that evidence of sophisticated behaviours in Africa predates this supposed revolution by tens of thousands of years.

“In Africa, decades of research now clearly show the presence of complex behaviours occurring in a gradual and piecemeal fashion long before this proposed ‘revolution’,” Groucutt and Scerri wrote.

An Ongoing Puzzle

For now, the question of when humans first settled Australia remains open. While genetic evidence increasingly points towards a post-50,000 year arrival, gaps in both the archaeological and DNA records mean that no single line of evidence can be considered definitive.

“While archaeological evidence does not currently refute Allen and O’Connell’s theory,” Brumm wrote, “I think this evidence is coming, however, and it will have big implications for our understanding of ancient Sahul.”

The debate highlights the complexities of reconstructing the deep past and the need for continued interdisciplinary research combining archaeology, genetics and geology to build a clearer picture of Australia’s earliest inhabitants.

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