Tuesday, August 18, 2009

Archaeology: "Early Man Used Fire 72,000 Years Ago"

"Early Man Used Fire 72,000 Years Ago"

"Just as raising temperature can change the properties of iron and other metals, early humans heated stone to make it easier to flake. The process transformed a stone called silcrete into an outstanding raw material for tool manufacture. Doctoral student Kyle Brown, who led the research at the University of Cape Town in South Africa, said: ''Our illumination of the heat treatment process shows that these early modern humans commanded fire in a nuanced and sophisticated manner.

''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.'' Previously, the first use of heat treatment was thought to have been in Europe 25,000 years ago. The technique was not believed to have been invented until long after the ancestors of modern humans had left Africa and settled in Europe and Asia.

Scientists had been puzzled by the fine-grained and often reddish coloured silicate blades and axes excavated from prehistoric sites at Pinnacle Point on the South African coast. None of the material used to make these advanced tools matched local silcrete outcrops. The raw stone ''was just not suitable for tool production'' said Mr Brown. Then a large flake of silcrete almost 10 centimetres in diameter was found embedded in ash in an ancient fire pit. It was only at that moment the researchers began to suspect that the stone had been heat-treated.

Many of the tools had a sheen or gloss reminiscent of much later North American artefacts made from heated material. To test the theory, the scientists recreated what ancient tool makers might have done by heating a pile of silcrete stone in a fire pit. The next day the silcrete had become a deep red colour and was easily flaked. Using the heated stone, the researchers were able to produce realistic copies of silcrete tools.

''Here are the beginnings of fire and engineering, the origins of pyrotechnology, and the bridge to more recent ceramic and metal technology,'' said Mr Brown. The research is described in the journal "Science." Knowing how to use fire may have helped the early humans who left Africa 50,000 to 60,000 years ago to cope with colder conditions in Europe.

It may also have given them a big advantage over the resident Neanderthals they encountered. By 35,000 years ago the Neanderthals, a sub-species of human whose own origins were in Africa, were mostly extinct. Professor Curtis Marean, another member of the research team from Arizona State University in the US, said: ''The command of fire, documented by our study of heat treatment, provides us with a potential explanation for the rapid migration of these Africans across glacial Eurasia. ''They were masters of fire and heat and stone, a crucial advantage as these tropical people penetrated the cold lands of the Neanderthal.''

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