By Alison George
A reconstruction of the skull of a Homo naledi childBrett Eloff Photography
Archaeological evidence suggests that Homo naledi, a primitive human species with a chimpanzee-like skull, used fires to cook food and navigate in the darkness of underground caves, despite having a brain one third of the size of ours.
“We have massive evidence. It’s everywhere,” says Lee Berger at the University of the Witwatersrand in South Africa. “Huge lumps of charcoal, thousands of burned bones, giant hearths and baked clay.”
This find, which is still being analysed and remains controversial, could revolutionise our understanding of the emergence of complex behaviours that had been thought to be the sole domain of large-brained species, such as modern humans and Neanderthals.Advertisement
H. naledi was first discovered in 2013 in the Rising Star cave system in South Africa when two cavers managed to enter a hitherto unexplored chamber via an incredibly tight passage. The surface was littered with thousands of fossil bones. In 2015, these were declared to belong to a new species.
We now know that H. naledi was about 144 centimetres tall on average and weighed around 40 kilograms. It had a strange mix of primitive and modern features, with ape-like shoulders, a tiny brain only just bigger than that of a chimpanzee and teeth “more reminiscent of something millions of years old”, says Berger.
Yet dating of its fossil remains in 2017 showed that it lived relatively recently, between 230,000 to 330,00 years ago, meaning that it could have co-existed with Homo sapiens, which evolved in Africa around 300,000 years ago.
A hearth possibly made by Homo nalediLee Berger
But questions remained about how H. naledi navigated through the labyrinth of underground passages at Rising Star, which are in complete darkness and require complex manoeuvres through gaps in the rock just 17.5 centimetres wide.
This inaccessibility means that, in the past decade, only 47 people – all small and slightly built – had managed to access the Dinaledi chamber where H. naledi fossils were first discovered. But in August this year, Berger, who is 188cm tall, decided to risk entering this labyrinth, losing 25 kilograms of weight in preparation.
“It’s not a space made for six-feet-two people like me. I’m by far the largest person who’s even been in,” he says. He knew there was a possibility he might not be able to squeeze out again. “I almost died on the way out,” he says.
The risk paid off. When Berger entered the Dinaledi chamber and looked up, he realised that there were blackened areas and soot particles on the rock. “The entire roof of the chamber is burnt and blackened,” he says.
By coincidence, at the same time that Berger was observing the soot, his colleague Keneiloe Molopyane, also at the University of the Witwatersrand, uncovered a tiny hearth with burnt antelope bones in another part of the cave system, then a large hearth next to it 15cm below the cave floor. Then, in another area called the Lesedi chamber, Berger found a stack of burnt rocks, with a base of ash and burnt bones.
This is a remarkable discovery, as many researchers thought it was impossible for such a small-brained hominin to make and use fire within a cave system. Although we have evidence that ancient humans living in what is now Kenya could control fire as far back as 1.5 million years ago, this capacity “is typically associated with larger-brained Homo erectus”, says Berger.
H. naledi also seem to have used the space in interesting ways, with “body disposal in one space and cooking of animals in adjacent spaces”, says Berger. “The capacity to make and use fire finally shows us how Homo naledi ventured so deep into dangerous spaces, and explains how they may have moved their dead kin into such spaces, something likely impossible without light. It also hints at a complex naledi culture becoming visible to us.”
Dating of the charred remains is still underway, so the decision to announce the fire discovery in a talk on 1 December, prior to the publication of the formal scientific analysis, has proved controversial.
“It’s impossible to evaluate Lee Berger’s claims properly without seeing the full evidence, but apparently that is forthcoming,” says Chris Stringer at the Natural History Museum in London. “With all due respect to Lee and his teams for a series of great finds, this is not the way to conduct science or progress scientific debate about potentially very important discoveries.”
However, for Francesco d’Errico at the University of Bordeaux in France, the discovery that H. naledi may have been able to control fire could give insight into the way they treated their dead and their social organisation.
“If Homo naledi were shown to have mastered fire and used it to gain access to the most remote areas of the Rising Star karst system, this could have very important implications for the interpretation of mortuary practices conducted at the site,” he says. “The control of an artificial light source allows the organisation of actions in space and time and, in the case of mortuary practices, facilitates the participation of several members of the group in collaborative and shared actions.”
Charcoal possibly used by Homo nalediLee Berger
For Berger, the fire-use discovery has implications that are even more revolutionary. If these small-brained humans with many primitive features were capable of the complex cognition required to make and control fire, then “we’re beginning to see the emergence of a cultural pathway and behaviour that we thought, until this moment, was the domain of [Homo sapiens and Neanderthals],” he says.
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