Humans living in Africa used heat to break stones and make sharp blades tens of thousands of years before the technique was developed elsewhere, according to a study published Wednesday.
The new evidence, in the journal Plos One, shows that humans living in South Africa more than 65,000 years ago sharpened rock into blades in the oldest known use of pyrotechnology to transform matter, researchers said.
"This marks a leap in knowledge and skill to use fire in the transformation of matter, which represents a considerable step in the technological evolution of man that is unique to this region," Anne Delagnes, a lead researcher of the study from the French National Center for Scientific Research (CNRS), told AFP.
Conducted at the Klipdrift Shelter -- a recently discovered Middle Stone Age site southeast of Cape Town -- the researchers analyzed heating techniques used to produce blades from silcrete rock.
The researchers found that 92 percent of the rock samples had traces of intentional heating -- a process that would harden and break open the rock, producing sharp pieces to make blades.
"The fire breaks the stone and removes internal impurities, minimizing the risk of fracture during the process -- a fairly sophisticated technique," said Delagnes.
Analysis suggested the stones were rapidly heated early in the process in open fireplaces at temperatures higher than 450 degrees Celsius (842 degrees Fahrenheit).
The humans were apparently making small stone tools with short blades on handles. Some even had multiple blades on one handle -- an ancient ancestor of the Swiss Army knife.
"It was an extremely innovative period in southern Africa," said Delagnes. Besides technological innovations including this form of pyrotechnology, she said there were already symbolic engravings of the first set of the elements on ostrich eggshells.
This most recent finding indicates that the use of intentional heat treatments was used in Africa between 50,000 and 65,000 years ago.
No traces of the technological innovation exist again until some 20,000 years ago when it was discovered in Siberia, and later on in Europe about 18,000 years ago, when heat was sometimes applied to finish tools.
Fire was applied to create blades more systematically in Western Europe just 11,000 years ago during the Neolithic period, which marked the beginning of human civilization with the appearance of agriculture and livestock.
