A 1 million-year-old fire lit by human ancestors has flickered back to life in a South Africa cave.
Microscopic plant ashes and burned bone bits in Wonderwerk Cave come from soil that previously yielded several dozen stone tools, say archaeologist Francesco Berna of Boston University and his colleagues. A member of the Homo genus, perhaps Homo erectus, made a fire that produced those remains, the researchers write April 2 in the Proceedings of the National Academy of Sciences.
Berna’s team regards its data as the oldest secure evidence for controlled fire use. The ashes and charred bone — unearthed earlier in Wonderwerk Cave by Peter Beaumont of the McGregor Museum in Kimberley, South Africa — show no signs of having been carried there by wind, water or wildfires.
Although it’s unclear exactly how members of an extinct Homo species used this fire, the new findings fit with an idea that Homo erectus began to cook food nearly 2 million years ago, the scientists propose.
And human ancestors may have had other reasons for taming fire. “Socializing around a campfire might be an essential aspect of what makes us human,” says archaeologist and study coauthor Michael Chazan of the University of Toronto.
An age estimate for the Wonderwerk fire largely comes from measurements of radioactive elements in soil that signal how long ago dirt covered the burned material. Molecular characteristics of burned bone fragments show they were heated to about 500° Celsius, consistent with a controlled fire of some kind, the researchers say.
Several stone artifacts from the same ancient soil display fractures produced by heating during tool production.
Human ancestors were probably responsible for the Wonderwerk Cave fire, but fires were not produced regularly that far back in the Stone Age, say archaeologists Wil Roebroeks of Leiden University in the Netherlands and Paola Villa of the University of Colorado Boulder. Remains of a hearth or campfire area, where fires would repeatedly have been lit, have not turned up in Wonderwerk Cave.
“Fire use was not a skill that was transmitted from generation to generation, over long periods of time, all over the Old World prior to about 400,000 years ago,” Roebroeks and Villa say.
Early Homo species survived in cold parts of Europe more than 400,000 years ago without habitually using fires, Roebroeks and Villa wrote in a recent review of hundreds of archaeological sites dating to between 1.2 million and 40,000 years ago.