The presence of modern humans in Australia dating back 60,000 years is supported by various lines of archaeological evidence, including the discovery of stone tools and ancient human remains.

Johannes-Boyau said what has been found so far in the cave is another piece in the evolution of man in Southeast Asia.

Nothing has been found in the cave such as drawings of stone tools to suggest it was a settlement.

"If anything, it was probably a transit route," he said.

"The remains are significant in that little is known about our journey (out of Africa). Every time we find new fossils we basically rewrite what the human evolution journey has been," he said.

Macquarie University's Westaway said that when trying to reconstruct the migration of Homo sapiens, it always comes down to a question of timing.

"We know what happened; we just don't know exactly when it happened," she said.

"Sites like Tam Pa Ling help us to place Homo sapiens at a certain location at a certain time and this helps to reconstruct how and when they dispersed."

She said finding earlier-than-expected arrival sites in unanticipated locations helps to appreciate the ability of Homo sapiens to adapt to different conditions and to exploit varied and often extreme environments.

Finding evidence of Homo sapiens in Southeast Asia 86,000 years ago also poses a problem for scientists.

Westaway said it calls into question "the accepted timing for the exit out of Africa … at least according to genetic evidence".

"Human dispersal across the globe is not a simple linear path — we believe it's a more complex spread of different migrations; some very early and some much later," she said.

The fossil finds in Laos suggest that the prevailing theory of modern humans moving out of Africa in a single wave about 50-60,000 years ago was incorrect.

"The 50-60,000 years migration across Southeast Asia that contributes to our current gene pool may not have been the first — there may well have been earlier migrations that were not successful and therefore did not contribute their genetics to our modern populations," Westaway said.

"Sites like Tam Pa Ling, Lida Ajer (Sumatra) and Madjedbebe (northern Australia) may well represent these early unsuccessful migrations, but this does not discredit the fact that they had arrived in this region by this time — a truly remarkable achievement."

Westaway added: "This really is the decisive paper for the Tam Pa Ling evidence. Finally, we have enough dating evidence to confidently say when Homo sapiens first arrived in this area, how long they were there and what route they may have taken."

Tam Pa Ling cave is very close to the recently discovered Cobra Cave, which was frequented by Denisovans approximately 70,000 years earlier.

Despite the previous lack of evidence for early arrival in mainland Southeast Asia, this area might have been a dispersal route among our ancestors, long before Homo sapiens.

"We have much to learn from the caves and forests of Southeast Asia," Westaway said.

Prime Sarmiento in Hong Kong contributed to this story.