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This is Scientific American 60-Second Science. I'm Cynthia Graber. This'll just take a minute.

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Early modern humans didn't just chip away at stones to create their tools.

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They treated stone with fire in a sophisticated fashion, according to research published August 14th in the journal Science.

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About 72,000 years ago, our ancestors along coastal South Africa made tools from silcrete, a cement-like layer of soil.

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The silcrete found at archaeological sites was glossy with a fine grain and a reddish color.

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It didn't match stones in local outcroppings.

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Researchers from the University of Cape Town couldn't find big enough pieces to learn more, until a couple of years ago.

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Then a colleague from Arizona State University remarked that a piece of silcrete reminded him of heat-treated tools in the Southwest.

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So the researchers set up a fire pit and buried a silcrete sample at high temperature.

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The next day, the stone looked like ones used by early humans.

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It flaked easily and provided the basic material for complex tools.

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Until now, heat treatment was thought to have started in Europe 25,000 years ago.

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This discovery pushes it back tens of thousands of years into Africa,

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and suggests that the southern African coast may have been the site of a truly Promethean revolution.

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Thanks for the minute, for Scientific American 60-Second Science. I'm Cynthia Graber.

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