Though our early ancestors used stone tools for more than two million years, certain techniques used for shaping them into more potent weapons are of relatively recent innovation. Pressure flaking, one of the techniques used to produce sharp-edged points on the tool, was believed to have originated merely 20,000 years ago. But a paper published online in Science shows that our ancestors used this technique 75,000 years ago. The samples studied were collected from the Blombos Cave near southern Cape, South Africa. Pressure flaking involves the use of objects to exert pressure at the tips of stone tools to remove small flakes. The finished tools thus produced have thinner, sharper, and narrower bifacial points that are difficult to achieve by using only percussion. Pressure flaking gives the toolmaker a greater degree of control on the final shape of the tool edge. Detailed study of the flaked points and comparison with experimentally produced pressure-flaked points by the authors helped confirm that the silcrete artefacts from the Blombos Cave were heat-treated prior to flaking. They also revealed that pressure flaking was used only at a final stage and was preceded by percussion with hard and soft hammers.
Stone tools used by early Homo sapiens provide direct evidence of their cognitive and technological evolution. Oldowan tools, which are sharp stone flakes struck from river cobbles, first appeared some 2.6 million years ago. Acheulian tools, also called the hand axes, are teardrop-shaped cutting tools that followed the Oldowan tools about 1.7 million years ago. Researchers recently reported in Science (“Early Pleistocene presence of Acheulian hominins in South India” by Shanti Pappu et al., March 25, 2011) the discovery of hundreds of typical Acheulian artefacts as old as 1.51 million years at Attirampakkam site near Chennai. Despite the simplicity of production, both Oldowan and Acheulian tool-making processes activate different parts of the brain. If these techniques called for manipulative complexity, South African knappers should have possessed a greater degree of cognitive development to produce the Blombos Cave artefacts — combining hard and soft percussion with pressure flaking after heat treatment. Along with other advanced tool-making techniques, the early humans who migrated out of Africa after the Acheulian hominins were probably better wired neurologically and more adept at hunting for food than the Neanderthals.