A new study has uncovered evidence that early human ancestors were using fire in South Africa's Wonderwerk Cave between 1.07 and 1.79 million years ago, extending the chronology of one of the earliest known records of fire use associated with hominins. By applying a new method that detects traces of burning in fossil bones, researchers found signs of repeated fire use deep inside the cave, far beyond the reach of natural wildfires. The findings suggest that early humans were bringing naturally occurring fire into the cave and maintaining it there, providing new insights into how our ancestors first began to harness one of the most important tools in human history.
A new study has uncovered evidence that early human ancestors were using fire far earlier than previously confirmed, with traces of fire use dating to between 1.07 and 1.79 million years ago in South Africa's Wonderwerk Cave.
The study was part of an ongoing collaboration between Dr. Liora Kolska Horwitz of the Hebrew University of Jerusalem's National Natural History Collections (co-director of the Wonderwerk Cave project with Prof Michael Chazan, University of Toronto) and and an international team of researchers from Spain, Argentina, Canada, USA, South Africa, Portugal and Israel. Their research combines methods from archaeology, paleontology, geology and a range of scientific techniques to investigate one of the key developments in human evolution: the use of fire.
The current paper builds on the previous discovery of early fire at Wonderwerk Cave, located in the Kalahari Desert of South Africa, that was dated to ~1 million years ago (published by members of the team in 2012 in PNAS), that provided the oldest evidence for intentional use of fire worldwide.
Continuing research at Wonderwerk Cave has now pushed the date for early fire back further, with new evidence fortraces of fire use in archaeological deposits dating between 1.07 and 1.79 million years ago, extending the chronology of one of the earliest known records of fire use associated with hominins. The findings, published in PLOS One, provide new insight into how our ancestors may have interacted with fire long before they learned to create it themselves.
Fire provided warmth, protection from predators, and light after sunset, and eventually enabled cooking. Yet determining exactly when humans first began using fire has remained one of archaeology's most challenging questions.
"Evidence of fire from such ancient sites is often subtle and difficult to detect," said the Dr. Kolska Horwitz. "Our study provides new tools for identifying traces of ancient burning and reveals that fire was repeatedly present deep inside Wonderwerk Cave."
The study also introduces a new method based on the light-emitting properties of burned bone.
When illuminated with specific wavelengths of light, bones that have been exposed to intense heat emit a distinctive glow. By combining this non-destructive luminescence technique with established chemical analyses, researchers were able to identify burned animal bones with a high degree of confidence.
The method is non-invasive, portable, and can be applied to large collections of fossils without damaging them.
The new research applied this method to examine traces of burning on hundreds of tiny fossil bones left behind by owls that once roosted in the cave. Because these remains accumulated naturally on the cave floor, they provide an independent, non-anthropogenic record of ancient events.
The scientists now found clear signs of burning in an archaeological layer associated with artefacts from the initial Acheulean, likely associated with Homo erectus. Importantly, these burned remains were discovered approximately 30 meters inside the cave—far beyond the reach of natural wildfires, and in a layer lacking remains of guano which rules out spontaneous combustion.
The findings do not indicate that these early humans could create fire at will. Instead, the evidence points to the use of naturally occurring fires, such as those sparked by lightning or wildfires on the African savanna. The early humans introduced this fire into the cave on multiple occasions and maintained it there before it eventually died out. The team suggested that they may have used the owl pellets as fuel, resulting in burning of the tiny bones of rodents that were in the pellets.
Nevertheless, bringing fire into a cave and maintaining it represents a significant behavioral achievement.
"These discoveries show that early humans were not simply passive observers of natural fires," Dr. Kolska Horwitz explained. "They were actively engaging with fire and incorporating it into their lives."
Beyond extending the record of fire use, the study provides archaeologists with a new tool for investigating how and when humans first began using fire.
As researchers continue to apply this technique at archaeological sites around the world, it may help clarify the origins and development of one of the most consequential technologies in human history.
