Stone Age Toolmakers Surprisingly Sophisticated

28 October 2010 4:08 pm

When they made tools, our prehistoric predecessors weren’t just pounding rocks. They could also carve with remarkable finesse. A new study suggests that cave dwellers were using a delicate stone-carving technique called pressure flaking 75,000 years ago, 55,000 years before scientists thought the technique was invented. And there are hints that pressure flaking might reach back even further in time.

Compared with haphazardly beating out new tools with a hammer, pressure flaking is a much more controlled, precise way of shaping stone. The researchers, led by Vincent Mourre of the University of Toulouse-Le Mirail in France, examined 127 triangular and leaf-shaped rock points (presumably for spears or knives) buried in the 75,000-year-old soil of a South African cave. Although pressure flaking had been identified in younger rocks before, the rocks had been made of flint. The ones the researchers found were made of silcrete—a much more difficult material to work with. To be sure they could tell which technique had been used, Mourre and colleagues took samples of the same silcrete from around the site. Mourre himself then created replicas of the buried artifacts using two techniques: the earlier hammering method and the later method that used pressure flaking as a retouch after hammering. When Mourre and his colleagues compared the artifacts with the copies, almost three-fifths of the ancient tools showed marks of pressure flaking: They had thinner, straighter edges that could pierce deeper and last longer. The team's results appear in the 29 October issue of Science.

Archaeologist Curtis Marean of Arizona State University in Tempe, who wasn't involved in the study, says the findings are plausible, but he's concerned that the conclusions rely too much on the researchers' general observations about the tools and not enough on mathematical data. Although the team did measure the length and width of scars left on the rocks, many of the conclusions were much more qualitative. "I'm not 100% sure we would get the same result if we put someone else in front of the material," he says.

Before this study, the earliest evidence of pressure flaking came from a region in France and dated to about 20,000 years ago, during a period known as the Solutrean. That age had been seen by many as one of the "hallmarks" of stone technology, according to Britt Bousman, an archaeologist at Texas State University in San Marcos, who was not part of the study. This new paper, he says, could effectively dethrone it.

Some scientists think the dawn of pressure flaking could go back even earlier. Stanley Ambrose, an anthropologist from the University of Illinois, Urbana-Champaign, points to a culture in northern Africa that predates the one in South Africa: the Aterian culture. Although the South African community in this study appeared and disappeared in a few millennia, Ambrose says makers of Aterian tools wandered the warm regions of northern Africa for roughly 100,000 years. A 1946 paper described evidence of pressure flaking in Aterian spear points. But the problem, according to Ambrose, is that it's hard to precisely date material in the Aterian time period, which overlapped with the culture in South Africa, so it's uncertain whether these tools are older than the South African ones.

"The real question is, just how far back does this actually go?" says archaeologist David Braun of the University of Cape Town in South Africa. By his estimate, pressure flaking might date back another hundred thousand years.

Correction: This article originally placed the Aterians in central Africa. It has been corrected to say they lived in northern Africa.

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