“This is a 400,000-year-old site where we have the earliest evidence of fire, not just in Britain or Europe, but anywhere else in the world,” said Nick Ashton, one of the study's authors and a curator at the British Museum. Ashton added that this pushes back the first convincing evidence of fire-making by human ancestors to about 350,000 years ago.
Researchers aren't sure what these human ancestors used fire for—perhaps they roasted venison, carved tools, or shared stories by firelight.
Exactly when human ancestors developed the ability to use fire is a key question that may help unlock some of the mysteries of human evolution and behavior.
One theory is that the ability to make fire led to an increase in the brain size of human ancestors during evolution, since cooking increases calorie intake, making them easier to digest. Another idea is that controlling fire could also help create space for people to gather at night, which could increase human sociality and trigger cognitive evolution.
“We know that brain size increased to its current level around this period,” said Chris Stringer, director of the study of human evolution at the Natural History Museum in London and another author of the Nature study. “Our brains are energetically expensive. They use about 20% of our body's energy. So using fire, being able to make fire, will help release nutrients from food, which will help fuel and control the brain. And really, you know, allow larger brains to develop.”
Stringer said the discovery does not mark the beginning of humans' ability to make fire, but is only the earliest example that researchers are confident about. There are other, earlier suggestions that human ancestors used fire in what is now South Africa, Israel and Kenya, but these examples are subject to some debate and interpretation.
From an archaeological perspective, it is difficult to know whether it was a forest fire or whether people started the fire they used.
“The question is, do they collect it from natural sources or just carry it around and treat it? Or are they making it up? On the surface, this is a very compelling case that groups of people knew how to make fire,” said Dennis Sandgat, a senior lecturer in the department of archeology at Simon Fraser University in Canada, who was not involved in the study.
In this new Nature study, the researchers point to sediments containing fire remains, the presence of stone tools such as chipped flint hand axes, and two small fragments of iron pyrite, which geological analysis shows is extremely rare and was likely brought to the site by humans to start fires.
Other outside researchers were less convinced.
In an email, Wil Robroeks, emeritus professor of Paleolithic archeology at Leiden University in the Netherlands, wrote that much of the evidence presented here is “circumstantial.”
Robrocks noted that later Neanderthal sites dating back to about 50,000 years ago yielded flint tools with signs of wear that indicated they had been struck by pyrite to create sparks—a “smoking gun” for human fire production. But that's not the point here.
“The authors have done an excellent job of analyzing the Barnham data, but they appear to be exaggerating the evidence by claiming that this is the ‘earliest evidence of fire starting,’” Roebrooks writes.
For human ancestors, fire was critical for keeping warm, feeding, repelling predators, and melting resin into glue, among other purposes.
But Sandgat said it was important to understand that the development of fire mining was not a linear process, but a piecemeal process that occurred intermittently. There is evidence that groups of human ancestors learned to make fire and then lost this ability or stopped using fire for cultural reasons.
“We have to be careful not to take one example … and just present it as an indication that everyone is fueling the fire from here on out,” Sandgat said, adding that he has reviewed research on about 100 modern hunter-gatherer groups whose lifestyle has been documented in detail by observers. Some groups did not have the opportunity to make fire.
“The best guess is that the fire was discovered by several groups in different regions over time, and then lost, rediscovered, and lost. I'm sure it's a very complex story.”
