Many thousands of years ago, early humans somehow figured out they could make better stone tools by treating the rocks with fire. Evidence of that, dating 72,000 years ago, has been found on the southeastern tip of Africa, researchers report in Friday's edition of the journal Science.
The find pushes back the first evidence of such technology by at least 45,000 years, according to Curtis Marean, a paleoanthropologist at the Institute of Human Origins at Arizona State University, a co-author of the report.
"Heat treatment technology begins with a genius moment -- someone discovers that heating stone makes it easier to flake," Marean said in a statement. The new discovery is then passed on and improved.
The researchers found items made from a stone called silcrete, which usually was poor for tool making. But heating it causes it to change color and alter its grain structure, making it more usable.
To test their idea, the researchers heated some silcrete overnight. In the morning, they found they could flake it into shiny tools similar to the ones they found at the archaeological site in Pinnacle Point in South Africa.
"Here are the beginnings of fire and engineering," said lead author Kyle Brown, a doctoral candidate at the University of Cape Town in South Africa.