It is likely that humans had some ability to control fire earlier than this, given that there is evidence that Homo erectus had done it in some way as early as 200-300 ky BP. Still, this is quite a step forward at this point.
The discovery has its roots in experimental archaeology. Kyle Brown, an archaeologist at the University of Cape Town in South Africa, and colleagues were trying to recreate the axes and hafted tools they were finding in the Pinnacle Point caves--a site containing many artifacts of early human activity--to learn more about how they were made. One of the local rocks that these early humans fashioned tools from is silcrete, which is similar to flint. But when the researchers tried to recreate the tools, they couldn't quite get it right. "We were having a really hard time coming up with [something] that looked like what we were finding at the site," Brown says.
So the researchers began experimenting with heat treatment. After much trial and error, they found that it took 20 to 40 kilograms of hardwood and almost 30 hours to create the 300°C temperatures in silcrete needed to fashion tools like those seen at Pinnacle Point. Those conditions alone were a good sign that the stone tools were no campfire accident, the team reports tomorrow in Science. "It requires a lot of planning," Brown says. "It's not the kind of thing people would do with an ordinary cooking fire." Heating makes the stones easier to flake and shape into blades.
Now playing: Anthony Phillips - Which Way the Wind Blows (2008 Remaster)