Tuesday, August 18, 2009

EARLY HUMANS WERE USING FIRE TO MAKE TOOLS

Evidence that early modern humans living on the coast of the far southern tip of Africa 72,000 years ago employed pyrotechnology - the controlled use of fire - to increase the quality and efficiency of their stone tool manufacturing process, is being reported in latest issue of the journal Science.

An international team of researchers deduce that "this technology required a novel association between fire, its heat, and a structural change in stone with consequent
flaking benefits."

"Our illumination of the heat treatment process shows that these early modern humans commanded fire in a nuanced and sophisticated manner," says lead author Kyle Brown, a doctoral candidate at the University of Cape Town, and field and lab director in Mossel Bay, South Africa, for ASU's Institute of Human Origins. "We show that early modern humans at 72,000 years ago, and perhaps as early as 164,000 years ago in coastal South Africa, were using carefully controlled hearths in a complex process to heat stone and change its properties, the process known as heat treatment," explains Brown.

"Heat treatment technology begins with a genius moment - someone discovers that heating stone makes it easier to flake," says Curtis Marean, project director and a co-author on the paper. Marean is a paleoanthropologist with the Institute of Human Origins and a professor in the School of Human Evolution and Social Change at
Arizona State University's College of Liberal Arts and Sciences. "This knowledge is then passed on, and in a way unique to humans, the technology is slowly ratcheted up in complexity as the control of the heating process, cooling and flaking grows in sophistication," Marean says.

According to Marean, the silcrete bifaces are re-usable tools with many potential functions: effective hunting weapons, excellent knives and items of value for exchange. "Our discovery shows that these early modern humans had this complex cognition," Brown says. "There is no consensus as to when modern human behavior appears, but by 70,000 years ago there is good evidence for symbolic behavior,"
Marean added.

"Prior to our work, heat treatment was widely regarded as first occurring in Europe at about 25,000 years ago," Marean says. "We push this back at least 45,000 years, and, perhaps, 139,000 years, and place it on the southern tip of Africa at Pinnacle Point."

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