Parts of a skull found in a cave in Laos are the earliest skeletal evidence for modern human occupation in Southeast Asia, report researchers.

The findings, made by an international team, are published today in the Proceedings of the National Academy of Sciences

"Despite abundant limestone caves, there has been uncertainty about the arrival of modern humans in Southeast Asia because of a lack of dateable evidence," says archaeologist Dr Kira Westaway from Macquarie University, who led the dating component of the project.

Archaeological and genetic evidence to date support the idea that modern humans rapidly migrated out of Africa and were present in extreme Southwest Asia by 90,000 years ago, and in Southeast Asia by 60,000 years ago.

But so far there has been little fossil evidence for early modern human occupation on mainland Southeast Asia, with the oldest evidence in the area being a skull found in Sarawak's Niah Cave, dated at around 40,000 years.

Modern human features

Westaway and colleagues now present skeletal evidence that is older than this - found in a limestone cave known as Tam Pa Ling (Cave of the Monkeys) in northern Laos in 2009.

The latest skull, has modern human features, including facial bones and teeth and has been found to be at least 46,000 years old.

"Because of the lack of other archaeology that might have indicated humans lived in the cave, it is likely that this person died outside the cave," says Westaway, who was also part of the team that discovered the skeleton of Homo floresiensis, known as 'the hobbit' in Indonesia.

"The remains were washed in sometime later during a downpour, and subsequently buried."

Maximum age of around 63,000

The researchers were unwilling to remove any teeth from the intact skull to date them. Instead, they dated the sediments it was buried in using radiocarbon of charcoal found nearby and luminescence dating of quartz particles.

Luminescence techniques measure the time at which buried sediments were last exposed to heat and sunlight. Westaway's team adapted luminescence technology for Southeast Asian quartz's unique signature.

The combined dating techniques provide a minimum age for the sediments of 51-46,000 years. Uranium dating of other bone fragments indicates a maximum age of around 63,000 years.

These skeletal remains provide the earliest evidence for fully modern humans in mainland Southeast Asia and the earliest human fossil east of the Jordan Valley exhibiting modern human morphological features, says Westaway.

"There are a number of sites in the region containing stone tool evidence that are considerably older, but they lack skeletal evidence," she says.

"The significance of a site can only be understood if its age has been properly established ... This new technique will allow us to revisit classical sites and refine our understanding of their importance."