Deep inside a cave carved into the dolomite hills of South AfricaAfricaThe cradle of humankind: the continent where the first hominins appeared, then Homo sapiens around 300,000 years ago, before the expansion to the rest of the world.→'s Northern Cape, hominins were maintaining fires long before anyone imagined. A study published in June 2026 in PLOS ONE1 presents new evidence that Wonderwerk Cave was the scene of fire use between 1.07 and 1.79 million years ago -- in the Early PleistocenePleistoceneThe geological epoch of the great ice ages (c. 2.6 Ma–11,700 BP), spanning most of human prehistory.→. The most likely culprits: populations of Homo erectus, bearers of AcheuleanAcheuleanA stone-tool industry (c. 1.7 Ma–300,000 BP) characterised by large, finely worked almond-shaped bifaces. Associated with Homo ergaster and erectus and spread from Africa to Europe and Asia.→ culture, who carried flames from savanna wildfires and brought them deep into the rock.
Wonderwerk Cave -- "miracle" in Afrikaans -- extends horizontally for nearly 140 metres into the base of a dolomite hill, between Danielskuil and Kuruman in the Northern Cape. Studied since the 1940s, its stratified deposits, reaching up to 7 metres in depth, constitute a veritable palimpsest of human occupation stretching back roughly 2 million years. A 2012 study by Francesco Berna and colleagues had already identified combustion traces in layers dating to around one million years ago. The new research dives even further back in time.
Two methods to reveal heat in fossil bones
The international team led by Marin-Monfort and colleagues -- including Yolanda Fernandez-Jalvo of Spain's CSIC -- analysed 161 fossilised bones of small mammals from two Early Pleistocene layers, designated Strata 10 and 11. These animals had not been hunted: their remains most likely arrived in the cave via barn owl pellets, as owls nested and hunted nearby. It is precisely these bones that now bear the marks of heat.
To identify them, the researchers combined two complementary techniques. The first, Fourier Transform Infrared Spectroscopy (FTIR), detects the structural changes that temperature produces in bone mineral. The second, bone luminescence, exploits an optical phenomenon: under blue light with an appropriate filter, a heated bone emits a characteristic reddish glow absent from unheated bone1. This luminescence method was validated in the laboratory on modern bones heated to controlled temperatures, then tested against archaeological material from a Bronze AgeBronze AgeA protohistoric period following the Neolithic, defined by bronze metallurgy (a copper-tin alloy) and the rise of the first cities and states; in Egypt it corresponds to the age of the first pyramids.→ site in Spain: the two techniques agreed.
Applied to the Wonderwerk fossils, both methods reached the same conclusion: every white and grey bone from the oldest layer (Stratum 11) carries unambiguous signs of heating. The concordance between FTIR and luminescence substantially strengthens the result.
Thirty metres underground: the decisive argument
It is the position of the burned bones that constitutes the study's strongest argument. The fossils come from deposits at least 30 metres from the cave entrance. At this depth, no natural savanna fire can reach the sediment: the cave's very geometry prevents it. The hypothesis of accidental combustion from surface fires is therefore ruled out1.
Furthermore, the burned bones are not uniformly spread through the layer: they appear in localised clusters, suggesting repeated burning events at specific spots over long periods. These distribution patterns point to deliberate, recurring behaviour rather than isolated contamination.
Fire carriers, not fire makers
The hominins of Wonderwerk most likely did not know how to produce fire themselves. The study, cautious on this point, proposes that they captured flames from natural savanna wildfires, then transported and maintained them inside the cave1. Such behaviour implies planning and control -- cognitive capacities well beyond mere exposure to flames.
The burned bones were found alongside Acheulean stone tools and large mammal remains -- two classic markers of Homo erectus activity. Fire offered these hominins several advantages: warmth to endure cool Northern Cape nights, light beyond dusk, and protection from the nocturnal predators that were plentiful in the region during the Pleistocene. Food cooking, a later major nutritional benefit, is also possible but harder to document at such temporal depths.
The study also introduces a non-destructive method for detecting ancient hearths: bone luminescence can be measured without damaging the fossils, opening new prospects for the systematic survey of other PalaeolithicPalaeolithicThe oldest and longest period of prehistory (c. 3.3 Ma–12,000 BC), defined by chipped stone tools and a hunter-gatherer way of life.→ sites across Africa and beyond.
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