How Do We Know When A Hunk Of Rock Is Actually A Stone Tool?
The first time archaeologist John Shea looked at what might be the oldest stone tools ever found, he almost blew them off. “Are you kidding me?” he remembers asking Sonia Harmand, his colleague at Stony Brook University who found the tools in 2011 along the shores of Kenya’s Lake Turkana, at a site now known as Lomekwi 3. Harmand’s analysis suggested that the tools were 3.3 million years old — 700,000 years older than the previously known “oldest” tools. And they were huge. The mean weight of the pointy flakes — the cutting tools that are “flaked” off larger rock cores — was 2 pounds. In comparison, the next-largest group of ancient hominin tool flakes have a mean weight of 0.06 pounds. It seemed like a lot for the hands of a primate that was probably half the size of the average modern human. Maybe, this time, a rock was just a rock. But then Shea looked at the Lomekwi tools more closely, and he saw multiple fractures, all running in the same direction — a telltale sign that the flakes weren’t just the lucky product of one rock bumping into another as it tumbled off a cliff or rolled through a stream. Something had pounded one rock against another in the same place over and over and over … until a sharp piece broke off.
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