Discoveries of stone tools with fine edges made by pressure flaking at Blombos Cave in South Africa show that this highly skillful and delicate method of sharpening and retouching stone tools appears to have developed at least 75,000 years ago, more than 50,000 years earlier than previously thought.
"Pressure flaking has been considered to be an Upper Paleolithic innovation dating to ~20,000 years ago (20 ka). Replication experiments show that pressure flaking best explains the morphology of lithic artifacts recovered from the ~75-ka Middle Stone Age levels at Blombos Cave, South Africa. The technique was used during the final shaping of Still Bay bifacial points made on heat-treated silcrete. Application of this innovative technique allowed for a high degree of control during the detachment of individual flakes, resulting in thinner, narrower, and sharper tips on bifacial points. This technology may have been first invented and used sporadically in Africa before its later widespread adoption" (Mourre, Villa, Henshilwood, "Early Use of Pressure Flaking on Lithic Artifacts at Blombos Cave, South Africa," Science 29 October 2010: Vol. 330. no. 6004, pp. 659 - 662 DOI: 10.1126/science.1195550)
"The technique provides a better means of controlling the sharpness, thickness and overall shape of bifacial tools like spearheads and stone knives, said Paola Villa, a curator at the University of Colorado Museum of Natural History and a study co-author. Prior to the Blombos Cave discovery, the earliest evidence of pressure flaking was from the Upper Paleolithic Solutrean culture in France and Spain roughly 20,000 years ago."
"Pressure flaking adds to the repertoire of technological advances during the Still Bay (period) and helps define it as a time when novel ideas were rapidly introduced," wrote the authors in Science. "This flexible approach to technology may have conferred an advantage to the groups of Homo sapiens who migrated out of Africa about 60,000 years ago" (http://www.sciencedaily.com/releases/2010/10/101028141753.htm).