Ancient Weapons Point to First Use of Fire for Tools?

Christine Dell'Amore
National Geographic News
August 13, 2009
With the tell-tale sheen of heat-treated rock, a 72,000-year-old cache of stone weapons found in Africa suggests humans began using fire to create tools nearly 50,000 years earlier than previously thought, a new study says.

Scientists had thought people began manipulating fire to create tools in Europe about 25,000 years ago.

But the new finds suggest that people in what is now South Africa discovered that heating a stone called silcrete would make it easier to flake, allowing them to shape more advanced blades, knives, and other tools.

These early engineers likely used some of these tools, mounted on handles, to hunt and butcher wide range of prey, from the aggressive Cape buffalo (Cape buffalo picture) to the tiny mole rat, according to the authors of the study, to be published tomorrow in the journal Science.

Birth of Modern Humanity?

This sophisticated control over fire reflects advanced smarts, and marks the turning point when we became "uniquely human," said study leader Kyle Brown, an archaeologist at the University of Cape Town in South Africa.

"These people were extremely intelligent," Brown said. "These are not the image of the classic cavemen, of brutish people that are stumbling around the landscape and, in spite of themselves, surviving.

"These are the people that [may have] even colonized the rest of the world," he said.

As part of the study, the researchers replicated the processes the early Africans likely would have used to make the stone tools. Heated over a fire pit, the silcrete flaked and took on a glossy red color.

Such craftsmanship required thinking ahead, a sign of high intelligence, Brown said. People had to collect firewood, build the fire, work the stone, and then afix the handle to the stone using natural adhesives.

"Because [this is] such a sophisticated technology, this is something that would involve language to pass it on to the next generation," he added.


But paleoanthropologist John Shea isn't convinced by the idea that "heat treating" stone was a sign of the transition to modern human behavior.

"People rush immediately to look for evidence of a transforming event in the course of Homo sapiens evolution to distinguish modern humans from so-called early ones," said Shea, of Stony Brook University.

"My position is that you shouldn't assume this transformative event—you have to prove it," Shea said.

To begin with, scientists would need to verify that the various human species preceding H. sapiens in South Africa did not also heat-treat stones.

Even so, Shea praised the study, saying it will inspire people to seek out other heat-treated stone tools undetected in the African record.

Showing Off?

The tools were apparently created during a burst of cultural growth, when the human population was slowly recovering from a severe glacial period.

At the South African sites, humans were designing jewelry, such as shell beads, and grinding up ochre to paint themselves and decorate their caves, study leader Brown said. (See "Oldest Jewelry? 'Beads' Discovered in South African Cave.")

Heat-treating stone could have been "one of the technologies in their toolkits that allowed [them] to adapt to different areas as they expanded out of Africa," Brown said.

(Related: "Innovation Linked to Human Migration Out of Africa.")

But heat treatment probably didn't improve the tools, and may have even made them more likely to shatter, Stony Brook's Shea said.

Instead the flashy artifacts might have been ways that "some humans showed off that they had time on their hands," Shea said.

"Going into woods with a bunch of arrows that would shatter on impact is another way of saying, I'm a really good hunter; I don't need backup."

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