Burned small-mammal bones found deep inside South Africa’s Wonderwerk Cave point to fire use between 1.07 and 1.79 million years ago, potentially extending the known record of controlled fire by hundreds of thousands of years.
Wonderwerk Cave has already provided evidence of ancient fire use. In an upper layer known as Stratum 10, researchers found burned bone, sediment and stone tools altered by heat, dating to about 1 million years ago.
The new evidence comes from Stratum 11, an older layer deeper in the cave. Archaeologists found small mammal bones there that appeared to have been burned.
To test that interpretation, the researchers used a technique called bone luminescence. Under a microscope, fossils are exposed to high-energy blue light. Burned gray and white bones glow red when viewed through a filter, providing a way to identify evidence of burning.
The location of the bones also helped rule out a wildfire as their source. They were found about 30 meters from the cave entrance, well inside the cave.
Dating the possible fires
The researchers used two methods to establish when the sediments containing the bones were deposited: magnetostratigraphy and cosmogenic burial dating.
Together, those methods produced an estimated age of between 1.07 and 1.79 million years for the evidence in Stratum 11.
That places the fire evidence substantially earlier than the roughly 1-million-year-old evidence previously identified in the cave and could make it the oldest evidence of fire use so far.
What the evidence does and does not show
The burned bones from Strata 10 and 11 point to repeated combustion events in parts of the cave. Their location and distribution provide evidence that fire occurred deep inside Wonderwerk Cave rather than simply reaching the site through a natural wildfire.
But the findings do not establish that people routinely cooked food there or had technology specifically for making fire.
Instead, the evidence suggests that early humans may have repeatedly brought fire into this part of the cave and managed it.
The study was published in PLOS One.
