“It’s now very plausible to argue that Homo erectus used fire a million years ago. And I won’t be shocked if we find the site goes back to 1.8 millions year ago,” said Chazan.

The team’s analysis showed “unambiguous evidence” of burned animal bones and ashed plant material, which were contained in a layer of soil that had been dated to over a million years old by geologists using processes such as isotope decay. Also present in the cave were stone tools made by the genus of early humans known as Homo erectus.

The use of fire, which provides protection, heat, and light, is a critical benchmark in the timeline of human evolution. The Wonderwerk team’s evidence shows fire was used over 300,000 years earlier than previously thought.

These findings potentially react with a number of influential theories regarding the evolution of human behaviour, including those of U of T anthropology professor Richard Lee. Lee’s pioneering ethnographic studies of contemporary hunter gatherers in Botswana suggest that hunter gatherers developed complex egalitarian societies based around sharing food at sites with fires. Another potentially related theory is Richard Wrangham’s “cooking hypothesis,” which suggests that human evolution was accelerated by the nutrients offered by cooked food.

While these speculations are compelling, Chazan insisted that many questions remain. “It’s really puzzling. You’d think we’d find tonnes of material – but we don’t. It’s very spare. It’s a very low-level occupation.” This sparseness is not wholly consistent with the ‘base camp’ hypothesis of Lee’s work, or the ‘carnivores-that-cook’ hypothesis of Wrangham’s.

“What we don’t know is how they were using fire,” said Chazan. Also unknown is whether the fires were created at the site or whether they began as natural brush fires that were brought deliberately to the site. Analysis shows that none of the fires burned above 700 degrees C , which suggests that they were simple affairs fuelled largely by grasses and leaves.

To get their results, researchers extracted a block of sediment out of the cave, coated the block with plastic to keep its structure from shifting, and cut thin samples that were examined under a microscope as well as an infrared microspectroscope. Chazan highlighted these techniques for making the study the first of its kind on this time period. “I think this will become standard operating procedure.”

For Chazan and his team, the goal now is to start a project that will last somewhere between five to ten years and further detail how the site was used. Chazan plans to be back at Wonderwerk in the summer. Regarding the mysteries that these findings have stoked, Chazan said, “I think we have the methods to resolve them, but it will take a long time.”