Archaeologists in Australia have discovered the remains of the world's oldest axe, a polished Stone Age tool believed to have been made almost 50,000 years ago.
A thumbnail-sized fragment of the carefully polished tool was found in a rock shelter in the Kimberley region of Western Australia and indicates that the earliest stone axes were created some 10,000 years earlier than previously thought.
A study of the fragment found it was about 45,000 to 49,000 years old and dated back to the early arrival of humans in the Australian continent - a discovery which suggests the ancestors of today's Aboriginal people were leading innovators of hunting technology.
"Nowhere else in the world do you get axes at this date," said Professor Sue O'Connor, an archaeologist from the Australian National University.
"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 axe fragment was dug out of a remote rock shelter known as Carpenter's Gap, believed to be one of the first sites in Australia occupied by modern humans. Food scraps, artwork and other tools have also been found in the shelter.
Archaeologists excavated the fragment almost twenty years ago but only discovered the small artefact during further analysis in 2014 of some of the objects recovered from the oldest levels of the shelter.
Professor Peter Hiscock, from the University of Sydney, said axes were only developed in Australia's tropical north. This could indicate there were two waves of settlement in the continent or that humans abandoned the technology as they spread into desert and sub-topical woodlands.
"Since there are no known axes in South-East 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," he said.
"The ancestors of Aboriginal people, arriving on the Australian shores, were adapting to the continent. They were inventing new forms of tools to enable them to explore and settle the landscape." It is believed the fragment is from an axe that was shaped from basalt and polished by grinding it on another rock until smooth. When the axe's edge was re-sharpened, the fragment may have broken off.
"Polished stone axes were crucial tools in hunter-gatherer societies and were once the defining characteristic of the Neolithic phase of human life," said Hiscock.
"But when were axes invented? Now we have a discovery that appears to answer the question."
The findings have been published in the journal Australian Archaeology.