Monday, November 1, 2010

Origin of skillful stone-tool-sharpening method pushed back more than 50,000 years

ScienceDaily (Oct. 29, 2010) — A highly skillful and delicate method of sharpening and retouching stone artifacts by prehistoric people appears to have been developed at least 75,000 years ago, more than 50,000 years earlier than previously thought, according to a new study led by the University of Colorado at Boulder.

The new findings show that the technique, known as pressure flaking, took place at Blombos Cave in South Africa during the Middle Stone Age by anatomically modern humans and involved the heating of silcrete -- quartz grains cemented by silica -- used to make tools. Pressure flaking takes place when implements previously shaped by hard stone hammer strikes followed by softer strikes with wood or bone hammers are carefully trimmed on the edges by directly pressing the point of a tool made of bone on the stone artifact.

A paper on the subject was published in the Oct. 29 issue of Science. Other study co-authors included Vincent Mourre of the French National Institute for Preventive Archaeological Research in France and Christopher Henshilwood of the University of Bergen in Norway and director of the Blombos Cave excavation. The research was funded by the Wenner Gren Foundation of New York.

"Using the pressure flaking technique required strong hands and allowed toolmakers to exert a high degree of control on the final shape and thinness that cannot be achieved by percussion," Villa said. "This control helped to produce narrower and sharper tool tips." The bifacial points, known as Still Bay points, likely were spearheads, she said.

The authors speculated that the pressure flaking technique may have been invented in Africa and used sporadically before its later, widespread adoption in Europe, Australia and North America. North American archaeologists have shown that Paleoindians used the pressure flaking technique to fashion stone points likely used to hunt a menagerie of now-extinct mammals like mammoths, mastodons and ancient horses.

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Origin of skillful stone-tool-sharpening method pushed back more than 50,000 years

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