Archaeologists Discover Clues to Ancient Migration Route That Brought Humans to Australia

New research offers evidence that humans did not inhabit the island of Timor until around 44,000 years ago, suggesting it was not part of the original migration route from Southeast Asia to Australia

Sue O'Connor (left) and Shimona Kealy (right) study artifacts discovered in Timor-Leste
Sue O'Connor (left) and Shimona Kealy (right) study some of the artifacts found in Timor-Leste, which offer clues that early humans took a more northern path from Southeast Asia to Australia tens of thousands of years ago. Jamie Kidston / Australia National University

Archaeologists on the Southeast Asian island of Timor have unearthed new evidence that helps pinpoint how Homo sapiens may have first migrated to arrive in modern-day Australia.

In central-north Timor-Leste, a country on the eastern side of Timor, scientists discovered tens of thousands of artifacts deep inside a cave called the Laili rock shelter. They uncovered shells of snails, crabs and barnacles; bones from birds, fish, lizards, snakes, frogs and bats; and fragments of stone tools and a grindstone. Using radiocarbon dating, the team estimated the artifacts are about 44,000 years old.

But the significance came not just from what was found, but where: All of these items were discovered atop a layer of sediment that showed absolutely no evidence of human habitation. This boundary above a sterile geologic layer, researchers say, is known as an arrival signature—essentially a bookmark that divides the before and after of when humans were present in an area.

“Looking at the layers in Laili cave, it’s like ‘bang’—you can really see clearly when the people arrive,” Sue O’Connor, an archaeologist at the Australian National University (ANU), tells New Scientist’s James Woodford. “It was like a line had been drawn between the two layers—before people and after people. It was so clear.”

Multiple images depict thin sections of rock layers depicting crushed shells, animal bones, and tool fragments, amidst other organic sediment in a Timor-Leste cave.
Thin sections of rock layers depicting crushed shells, animal bones and tool fragments amid other organic sediment at the Laili site in Timor-Leste. O'Connor et al., Nature Communications, 2024

In a new study published in the journal Nature Communications in late May, O’Connor and others estimate the sterile sediment in Timor-Leste is between 54,000 to 59,000 years old. Because previous research has uncovered evidence of humans in Australia earlier than that—roughly 65,000 years ago—the team proposes that the island of Timor can be ruled out as a potential migration route to Australia.

Tens of thousands of years ago, modern-day Australia was part of the Sahul paleocontinent, which also included Tasmania and New Guinea. Questions around when and where humans settled this region have long puzzled archaeologists.

“When we analyze and compare markers of human occupation from other sites across Timor-Leste and nearby Flores Island, we can confidently say humans were also absent throughout the wider region of the southern Wallacean islands,” which were between Southeast Asia and Sahul at the time, study co-author Shimona Kealy, also an archaeologist at ANU, says in a university press release.

Archaeologists had previously considered two main options for how early humans might have traveled to Sahul from Southeast Asia, according to New Scientist. One route was via Timor—though the new study casts doubt on this—and another was via Sulawesi, an island to the north.

Close-up images of a notch tool discovered deep in the Laili cave in Timor-Leste.
Close-up images of a notch tool discovered in the Laili cave in Timor-Leste O'Connor et al., Nature Communications, 2024

In 2021, archaeologists suggested a cave painting of a warty pig found in Sulawesi and estimated to be 45,500 years old is perhaps the oldest known rock art on Earth.

While not directly related to the migration mystery, the myriad artifacts the team found are valuable clues, offering new insights into how these Pacific communities lived. Evidence of ample seafood, the scientists say, demonstrates a bustling maritime economy with seafaring technologies. Burn marks on fish bones and shells are further evidence of early humans’ presence.

“There’s no question from here […] that people were using mangrove and coastal resources early on, and that coasts were productive and probably always were for the spread of modern humans,” Peter Veth, an archaeologist from the University of Western Australia who was not involved in the research, tells Cosmos magazine’s Matthew Ward Agius.

Get the latest stories in your inbox every weekday.