The discovery of thousands of stone artefacts and animal bones in a deep cave in Timor Island has shed light on the timing and nature of early human migrations through Indonesia to Australia.
Researchers from Griffith University, The Australian National University (ANU), University of Wollongong, Flinders University, University College London (UCL) and the ARC Centre of Excellence for Australian Biodiversity and Heritage dated and analysed the artefacts and sediment at the Laili rock shelter in central-north Timor-Leste, north of Australia, to pinpoint the arrival of the colonists.
They detected an abrupt human "arrival signature" at the site, with no evidence for people in Eastern Timor before this time.
"The site of Laili is especially fascinating as it demonstrates a large human population settled on the island between 49-43,000 years ago," Griffith University's Research Fellow Kasih Norman said, who was the geochronologist on the project.
"The occupation of Laili therefore appears to be part of the large-scale migration of modern humans that took place across the globe between 70-40,000 years ago."
"Since there are sites to the west in Sumatra dated to 73-63,000 years ago and east in Australia by 71-59,000 years ago that are clearly much older than the evidence from Laili, the site may indicate a new, possibly large-scale migration overwhelmed earlier populations living in the broader region."
Norman used optically stimulated luminescence dating of ~17,000 individual quartz minerals to ascertain the burial age of the sediments encasing the artefacts at Laili, and the sterile deposits below them.
This allowed the research team to date the age of the sterile sediments and pinpoint the first arrival of a large colonising group of people at the site.
Study co-author Professor Sue O'Connor, also from the Australian National University, said Timor Island has long been considered a stepping stone island for the first human migration between mainland Southeast Asia and into Australia and New Guinea. But the new findings challenge this theory.
"The absence of humans on Timor Island earlier than at least 50,000 years ago is significant as it indicates that these early humans arrived on the island later than previously believed," she said.
"This provides further evidence to suggest early humans were making the crossing to Australia using the stepping stone island of New Guinea, rather than Timor Island as researchers had previously suggested.
"In addition to prompting a re-evaluation of the route and timing of earliest human migration through Wallacea and into Sahul, our findings highlight the fact that migration into the islands was ongoing with occupation of the southern islands occurring thousands of years after the initial settlement of Australia."
The sediment from the site was analysed at the Flinders Microarchaeology Laboratory by co-author Associate Professor Mike Morley.
"The shift from pre-occupation to intensive human activity at the site was very clear in the sediments," Associate Professor Morley said.
"As soon as people arrived on the scene, their use of the cave was very intensive, with clear evidence of burning and trampling of the shelter floor underfoot."
The research team unearthed lots of small stone tools during the excavation, as well as charred fish bones.
"We know these people specialised in making tiny stone tools, but we're not 100 per cent sure what they were used for," Dr Shimona Kealy (ANU) said.
"Because a lot of their diet was either shellfish or small animals, you don't really need big knives to gather that sort of food. But having small, fine tools is useful for things like stripping leaves to then weave into baskets, but also for creating wooden tools."
Based on the sheer number of artefacts unearthed at the site, the researchers say the migration to Timor Island was a "major" one. According to the researchers, these ancient humans likely made the crossing to Timor from nearby Flores Island and mainland Southeast Asia.
The research 'Abrupt onset of intensive human occupation 44,000 years ago on the threshold of Sahul' has been published in Nature Communications.
