29 October 2010

South Africa: Scientists Find Earliest Evidence of Method of Shaping Weapons

Cape Town — Scientists have discovered that people living at Blombos Cave in the southern Cape 75 000 years ago were using a sophisticated technique for shaping stone weapons about 55 000 years before anyone was doing so in Europe.

It is the earliest evidence to date of "pressure flaking", which involves using an animal bone to shave small flakes off a piece of roughly shaped stone, and adds to the growing body of evidence of complex, innovative human activities taking place at the site during the Middle Stone Age.

Scientists earlier found other evidence of modern behaviour at Blombos, such as shell beads and engraved ochre.

Until now, the earliest evidence of pressure flaking came from the Upper Paleolithic Solutrean culture in France and Spain about 20 000 years ago.

"It's a very skilful and advanced technique that no one expected to occur at such an early age in SA," said Dr Paola Villa , a curator at the University of Colorado Museum of Natural History and co- author of a paper describing the find, published in the journal Science today.

The weapons, known as Still Bay points, were probably tied to spears and used to hunt animals such as eland or bovids, Dr Villa said.

Pressure flaking is a time-consuming and complex technique, she said. A piece of silcrete is heated in a sand pit beneath a fire and slowly cooled and then shaped into a bifacial point - first using stone and wood hammers, then pressure flaked to delicately refine its shape.

Dr Villa and her colleagues suspected that silcrete points previously excavated from the Blombos Cave might have been pressure flaked. To gather the scientific evidence they needed to back up their hunch, they replicated the technique on silcrete stones they gathered from rocky outcrops 20km away from Blombos, and compared the two sets of points and the flakes produced under a microscope.

Pressure flaking is an advanced technique that may have given an advantage to the groups of modern humans who migrated out of Africa 60000 years ago, said Dr Villa.

What is not clear is whether it increased the success of a hunt, she said. "The people from Blombos were craftsmen. It is possible these points were more effective, but its also possible people were just taking pride in their craft: it is typical of modern humans to invest more energy in production than is strictly necessary."

Lyn Wadley, an honorary professor of archaeology at the University of the Witwatersrand, said pressure flaking made stone points more fragile, and said they may have been less effective weapons.

Still Bay points have been found at many other sites in the southern and western Cape, as well as the Sibudu and Umhlatuzana sites in KwaZulu-Natal, and it would be worth investigating whether they too had been pressure flaked, she added.

"This is an extremely interesting piece of research that demonstrates clearly the importance of replicating ancient artifacts or techniques before interpreting them," she said.

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