The new evidence comes from South Africa’s Wonderwerk Cave. Archaeological investigations there in the 1970s through 1990s turned up Acheulean tools—stone handaxes and other implements that were likely produced by Homo erectus. In 2004, Francesco Berna of Boston University and his colleagues began new excavations. They found several signs of fire, including tiny charred bone fragments and ash from burned plants. They also found ironstone—which the hominids used to make tools—with telltale fractures indicative of heating. Using a technique called Fourier transform infrared microspectroscopy, which examines how a sample absorbs different wavelengths of infrared light, the team determined the remains had been heated to more than 900 degrees Fahrenheit, with grasses, leaves or brush used as fuel.
The shape of the bone fragments and the exceptional preservation of the plant ash suggest the materials were burned in the cave—not outside and then transported in by water, the team reports this week in Proceedings of the National Academy of Sciences. Spontaneous combustion of bat guano was also ruled out (apparently this sometimes happens in caves). That left hominids as the most likely source of the fire.
The age of hominid fire is important, because fire is a crucial ingredient of the theory that humans developed bigger brains due to eating cooked food (previously at Neatorama). Read more on this discovery at Smithsonian's Hominid Hunting blog. Link
(Image credit: Wikimedia user 4028mdk09)