Artist’s impression of sparks from flint and pyrite

Craig Williams, The Trustees of the British Museum

Around 400,000 years ago, a band of Neanderthals, or their ancestors, in Britain struck flint with pyrite and built a fire repeatedly in the same spot. Archaeologists studying the site think it is the earliest evidence of humans starting fires ever found.

Early humans may have been opportunistically using fire for around 1.5 million years. But it is likely that these hominins simply made use of fire that had been ignited in other ways, such as through lightning strikes.

Evidence of more extensive use of fire increased in Europe from around 400,000 years ago. However, until now, we had only direct evidence that humans could control ignition from around 50,000 years ago.

Nick Ashton at the British Museum in London says there are three crucial pieces of evidence from the site his team has studied at Barnham quarry in Suffolk: pyrite, heated sediment and heat-shattered handaxes.

Pyrite is an extremely important mineral in the history of humans and fire, as it can be struck against flint to make sparks, which, in turn, can ignite kindling such as dry grass to make a fire. However, pyrite doesn’t occur naturally near the quarry site, so it must have been brought there by early humans. “Pyrite is certainly the clincher,” says Ashton.

But the reddish layer of sediment left by the fire is almost as important, he says. Burning alters the iron minerals in the sediment and can therefore change their magnetism. Laboratory experiments showed that the reddish clay sediment may have experienced fire a dozen times – possible evidence that humans returned to the same spot and lit fires repeatedly.

Heating flint can make it easier to shape into sharp tools, but overheating can cause the flint to shatter – as is the case with the handaxes found at Barnham. Tests showed they had reached temperatures of over 700°C, so Ashton suspects they were heated accidentally.