A team of archaeologists from the University of Sydney has discovered the world's oldest axe fragment in the Kimberly region of Western Australia. The fragment is very small - approximately the size of a thumbnail - and dates back 45,000 to 49,000 years ago during the Stone Age period at, or shortly after, humans made their way onto the continent.

The new finding is from a time period approximately 10 millennia earlier than other previous ground-edge axe discoveries, making it the earliest yet, and sheds light on the role that the Australians played in technological innovation.

"Since there are no known axes in Southeast Asia during the Ice Age, this discovery shows us that when humans arrived in Australia they began to experiment with new technologies, inventing ways to exploit the resources they encountered in the new Australian landscape," said Peter Hiscock of the University of Sydney and lead author of the study.

The fragment stems from Carpenter's Gap, a large rock shelter that is believed to be one of the first sites occupied by humans.

"Nowhere else in the world do you get axes at this date," said Sue O'Connor of the Australian National University and co-author of the study. "In Japan such axes appear about 35,000 years ago. But in most countries in the world they arrive with agriculture after 10,000 years ago."

The world's oldest axe fragment stems from an axe that was shaped from ballast and polished by grinding on another rock. The team believes that the complete axe was taken to another location while the fragment was left behind.

"Polished stone axes were crucial tools in hunter-gatherer societies and were once the defining characteristic of the Neolithic phase of human life," Hiscock said. "But when were axes invented? This question has been pursued for decades, since archaeologists discovered that in Australia axes were older than in many other places. Now we have a discovery that appears to answer the question."

The team believes that the Stone Age axe fragment suggests that this technology was created in Australia after human colonization approximately 50,000 years ago. Furthermore, these technologies were created as humans adapted to their surroundings.

"We know that they didn't have axes where they came from," O'Connor said. "There are no axes in the islands to our north. They arrived in Australia and innovated axes."

"Although humans spread across Australia, axe technology did not spread with them," Hiscock said. "Axes were only made in the tropical north, perhaps suggesting two different colonizing groups or that the technology was abandoned as people spread into desert and sub-topical woodlands."

"These differences between northern Australia, where axes were always used, and southern Australia, where they were not, originated around the time of colonization and persisted until the last few thousand years when axes began to be made in most southern parts of mainland Australia," he concluded.

The findings were published online in the May 9 issue of the journal Australian Archaeology.