A thumbnail-sized fragment of a ground-edge stone axe found in Australia predates previous discoveries by more than 10,000 years. The axe fragment, which was discovered in a remote area of Western Australia, is estimated to be between 45,000 and 49,000 years old. Archeologists from the University of Sydney believe it was invented soon after humans arrived in Australia around 50,000 years ago in response to new environmental contexts.

The researchers note a similar sudden appearance of ground-edge tools in Asia when people first colonized the Japanese archipelago about 38,000 years ago. They believe this is evidence of a pattern of innovation tied to the colonizing process. "Dispersing humans were often innovating as they entered new territories, rather than maintaining technologies that had been employed previously," they write in a journal paper.

Curiously, the technology does not appear to have spread across Australia with the early settlers. Current evidence suggests that ground-edge axes were only used in the tropical northern regions. The oldest axes found in southern parts of mainland Australia date back no further than a few thousand years.

This indicates that either two different groups colonized the continent or people abandoned the technology as they spread into desert and subtropical woodlands.

Professor Peter Hiscock, who led the study, holds a hafted axe – which he believes is indicative of the kind the fragment came from(Credit: University of Sydney)

The axe fragment comes from a site called Carpenter's Gap 1 in Western Australia's remote Kimberley region that was initially excavated in the early 1990s. The fragment itself was not discovered until 2014. Studies have revealed that it broke off the polished edge of an axe – possibly a rounded-edge hafted axe (an axe with a handle attached) – while its bearer re-sharpened it. The axe was shaped from basalt and smoothed and sharpened by grinding on another rock.

The discovery both provides evidence that ground-edge axe production is older than previously thought and shines new light on the adaptability of early humans. Technological innovation triggered by environmental contexts both impacted and was absorbed into cultural systems and began a process of differentiation between human societies that still goes on to this day.

A paper describing the discovery and its subsequent analysis was published in the journal Australian Archaeology.

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