According to a new report in Science magazine last week, one of the modern behaviors exhibited by the Middle Stone Age peoples of South Africa was heat treatment of stone tools, at least by 71,000 bp and perhaps as long ago as 164,000 years.
Overview of Pinnacle Point on the south coast of South Africa. Photo credit: © Science/AAAS
As any dedicated flintknapper can tell you, the intentional and controlled application of heat to certain kinds of fine-grained stone makes it easier to knap. The stone of choice used by people living in Still Bay occupations at Pinnacle Point was silcrete, a fine-grained stone brought to the sites from the South African coast. The authors of the article in Science ran flint knapping experiments on raw silcrete from those sources, and discovered that heating the silcrete made it significantly easier to work, particularly when they attempted to produce the bladelets regularly found in Still Bay and Howiesons Poort occupations of some 60,000 to perhaps as long ago as 164,000 years ago.
Refitted experimentally heat treated silcrete nodule. The yellowish portion of the cobble is the unheated control and the reddish colored flakes are the heated samples from that material. Note the texture and color change after heating and flaking
Photo Credit: © Science/AAAS
Flintknappers and archaeologists have long recognized that heat-treatment often changes the color, texture and lustre of a stone. Objective documentation of heat treatment on stone tools has been developed over the past fifteen years or so.
Techniques used by Brown and colleagues to substantiate the heat treatment of the worked stone at Pinnacle Point included archaeomagnetic analysis, thermoluminescence and maximum gloss studies. Archaeomagnetism is a dating technique that uses the fact that heating stone changes the magnetic polarity of the object. Thermoluminescence is another dating technique, that measures the length of time since the last heating of crystals within a stone. And Maximum Gloss is a direct measure of the changes in lustre created by heating.
Lead author Kyle Brown experimentally reproducing stone tools using heat treated silcrete.e
Photo Credit: © Science/AAAS
Results of the TL and archaeomagnetic studies clearly indicate that the folks at Pinnacle Point were heat-treating artifacts by 71,000 years ago. Maximum gloss results suggest that they may have been heat-treating raw lithic material as long ago as 164,000 bp. Now that's what I call "behavioral modernity".
More Information
Brown, Kyle S., et al. 2009 Fire As an Engineering Tool of Early Modern Humans. Science 325:859-862.
News Stories on Heat Treatment at Pinnacle Point
- BBC: Early toolmakers were 'engineers' (14 Aug 09)
- Christian Science Monitor: Stone Age humans found new use for fire: making tools (15 Aug 09)
- Telegraph: Stone Age man used fire to make tools - 50,000 years earlier than we scientists thought
- Live Science: Fire Used to Make Better Tools 75,000 Years Ago
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