October 29, 2010

Tool-making Invented 50,000 Years Earlier Than Thought

Researchers have discovered the oldest evidence to date that prehistoric humans in southern Africa had mastered a complex, delicate process to sharpen stones into spears and knives at least 75,000 years ago, more than 50,000 years earlier than previously believed, according to a study published Thursday.

The technique, known as pressure flaking, took place at Blombos Cave in modern day 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 involves using an animal bone or some other object to apply pressure near the edge of a stone and precisely carve out a small flake.  This allows for precision shaping of the stones, making them into better weapons for hunting, said the researchers from the University of Colorado at Boulder. 

The researchers examined the stone tools dating from roughly 75,000 years ago, and found the they had been created using pressure flaking, whereby ancient toolmakers would begin by striking a stone with hammer-like tools to give the piece its initial shape, and then refining the blade's edges and shaping its tip.

"This finding is important because it shows that modern humans in South Africa had a sophisticated repertoire of tool-making techniques at a very early time," said study co-author Paola Villa, a curator at the University of Colorado Museum of Natural History.

"This innovation is a clear example of a tendency to develop new functional ideas and techniques widely viewed as symptomatic of advanced, or modern, behavior."

Pressure-flaking provides a better means of controlling the sharpness, thickness and overall shape of two-sided tools, said Villa.

"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."

"This control helped to produce narrower and sharper tool tips."

To determine whether these prehistoric Africans could have been the first humans to use pressure flaking to construct tools, the researchers compared stone points believed to be silcrete spearheads to points they constructed themselves using heating and pressure-flaking.

The resemblance between the two led them to conclude that many of the artifacts from Blombos Cave were indeed made by pressure-flaking.

"This finding is important because it shows that modern humans in South Africa had a sophisticated repertoire of toolmaking techniques at a very early time," Villa said.

The authors theorized that pressure flaking might have been invented in Africa, and later adopted by people in Europe, Australia and North America.

The research was published in the Oct. 29 issue of the journal Science.


Image Caption: Pictured is a Still Bay bifacial point from Blombos Cave in South Africa made of silcrete and finished by pressure flaking, primarily at the tip. Credit: Image courtesy Science/AAAS


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