An ancient skull unearthed in Laos has reset the clock of human migration to southern Asia back 20,000 years.
The discovery suggests that the first modern humans to leave Africa spread around the world much earlier than was previously thought.
The skull, found in a cave in the Annamite Mountains, has been dated to between 46,000 and 63,000 years old.
Lead scientist Dr Laura Shackelford, from the University of Illinois in the US, said: "It's a particularly old modern human fossil and it's also a particularly old modern human for that region.
"There are other modern human fossils in China or in island south-east Asia that may be around the same age, but they either are not well dated or they do not show definitively modern human features.
"This skull is very well dated and shows very conclusive modern human features."
The fossil, discovered in 2009, is described today in the journal Proceedings of the National Academy of Sciences.
Dr Shackelford said it showed that early modern humans migrating out of Africa did not simply follow the coast to the islands of south-east Asia and Australia, as some experts believe. They also travelled northwards into very different types of terrain.
Experts believe the ancestors of people alive today either evolved in Africa and then colonised the world, or evolved in different locations across the globe. Most support the "out-of-Africa" theory.
"This find supports the 'out-of-Africa' theory of modern human origins rather than a multi-regionalism model," said Dr Shackelford.
"Given its age, fossils in this vicinity could be direct ancestors of the first migrants to Australia. But it is also likely that mainland south-east Asia was a crossroads leading to multiple migratory paths."
She added that the find supported genetic studies suggesting that modern humans occupied the region at least 60,000 years ago.
