About 70,000 years ago , people in South Africa were shoving rocks into fires to heat them and make it easier to reveal off flake that could be used as tools . The first elaborated sketch expect at this mental process has revealed how it was done .
hotness treatment to make tool edges sharper and straighter was used wide around the cosmos in the Late Stone Age , and in all likelihood invented severally by many dissimilar masses . stone modified in this way70,000 yr agoat several sites in South Africa are the onetime evidence of the consistent use of the appendage , although much aged sporadic examples exist , and nearby land site are of similar age . It read 50,000 years before similar high temperature discussion of tool became far-flung in Europe and Asia .
Dr Anne Delagnes , of the University of Bordeaux , found that 90 percentage of the silcrete tools at theKlipdrift Shelterin the southern Cape had been through fervor . Silcrete is a type of stone common in Africa and Australia . In its new form it is hard to work with , but in high spirits temperatures vary the stone bodily structure , make it more brittle and less porous , after which it is easier to break off eccentric suitable for use as tools .
InPLOS ONE , Delagnes reports that heating occurred early in the appendage of turning rocks into tools , with what she and her conscientious objector - authors call “ post - heating scars ” , where tool were broken off the rock . Many cock showed signs of also having been exposed to fire after completion , but this may have been inadvertent rather than part of the instrument - making process ; the floors of living areas were extensively and repeatedly burn off for unsung rationality .
Occasional heating fractures advise the stones were enclose directly into ember , rather than slow - heated in warm sand . Non - silcrete tools at the site were not similarly heated .
A : The line between raspy and smooth open identify a pre - heating cicatrix , B : A heat - induced fracture , C : Post - heating scars , 500 : Potlid fractures make by sudden warming . Delagnes et al / PLOS ONE
Silcrete was so appreciate in the Middle Stone Age that carry out made from it have been found 200 km ( 130 miles ) from where they were quarry , although the people live at Klipdrift had a much curt journey to obtain their materials .
Delanges and her conscientious objector - generator describe the deliberate heat handling of silica rocks as a “ major technical milestone in prehistory … It provides the first grounds of a transformative engineering science , and mark the emergence of ardor engineering . ”
The more we learn about the way some animals use tools , themore sophisticatedthey appear to be . sure birds even appear to havemastered spreading ardor , long thought to be an entirely human activity . Some stone tool antecedently opine to have been made by our ancestors might be theproducts of monkeysinstead .
Still , the combination of fire and stone flaking is distinctively human , set a degree where our engineering science take a step no other species has replicated .
