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Cooked Results: Modern Toolmaker Uses Fire to Solve 72,000-Year-Old Mystery

Archaeologists in South Africa have uncovered the earliest evidence of humans using pyrotechnology to shape their stone tools



Science/AAAS

Arrowheads and other Stone Age tools may not look like much to the untrained eye, but try making them yourself and you'll find out just how difficult it can be.

After struggling for years to replicate stone blades excavated in the southern tip of Africa, modern toolmaker Kyle Brown—like early humans before him—stumbled upon the missing ingredient: fire.

Most archaeologists have thought that humans developed pyrotechnology—the controlled use of fire—in Europe about 25,000 years ago. But Brown's discovery, published in Science today, pushes that date back to at least 72,000 years ago—and possibly as far as 164,000.

The new findings complement other discoveries, like shell beads and ochre pigments, revealing advanced technical capabilities in the earliest modern humans, who emerged between 150,000 and 200,000 years ago.

Beginning in 2006 Brown, a doctoral student at the University of Cape Town in South Africa, began hunting for stone outcrops that had the same silcrete (a hard material formed from dissolved silica) found in tools excavated from archaeological sites at Pinnacle Point. He and his colleagues made some 10 trips to the field, lugging the heavy rocks back to the lab and smashing them to try to recreate the stone blades. "I had a pretty high failure rate," he says. The stone never flaked off properly, and the tools he made were larger and thicker than the ancient tools. "We reached a point that we covered the landscape fairly well and we weren't finding any suitable rocks," he says.

The team, however, had recently excavated silcrete tools that had a glossy luster to them and looked a lot like heat-treated Native American tools they had seen before. In 2007 the researchers had also found a large hunk of silcrete embedded in ash. "Out of desperation," Brown says, "I put the materials in a fire." He buried them in a sand, built a fire on top, raised the temperature to 300 degrees Celsius over a period of about eight hours, and then cooked them for another eight. When he pulled the materials out of the sand, the rock flaked off easily, and had a glossy sheen that matched the silcrete artifacts.

Brown, 36, grew up in San Francisco and got his start making stone tools as a teenager. His father, a field biologist, took him on ecological studies in California's Napa Valley where he collected volcanic glass and tried to copy the arrowheads he found in the region. "I wasn't much good at that," he admits. Years later, as a student at the University of California, Berkeley, a toolmaker gave him instruction and he was hooked.

Now, Brown has something to teach the rest of us, something that earlier Homo sapiens figured out tens of thousands of years ago.

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