Carl Zimmer reports:

Some 400,000 years ago, in what is now eastern England, a group of Neanderthals used flint and pyrite to make fires by a watering hole — not just once, but time after time, over several generations.

That is the conclusion of a study published on Wednesday in the journal Nature. Previously, the oldest known evidence of humans making fires dated back just 50,000 years. The new finding indicates that this critical step in human history occurred much earlier.

“A lot of people had a hunch that they were making fire at this date,” said Nick Ashton, an archaeologist at the British Museum and an author of the study. “But now we can convincingly say, ‘Yeah, this was the case.’”

From Charles Darwin on, biologists have looked upon the mastery of fire as a hallmark in the evolution of our species. Early humans may have first used fire to cook their food. That advance let them improve their diet, by removing toxins from food and making it easier to absorb nutrients from their meals. Fires may have also kept them warm at night and kept predators at bay.

Later, they found new uses for fire. They cooked tree bark to create glue, which they used to anchor stone spear tips to wooden shafts. And starting about 10,000 years ago, humans began making fires to smelt copper and other metals, ushering in civilization.

As important as fire has been to our species, tracing its early history has proved an immense challenge. Rain can wash away ash and charcoal, erasing the evidence of a fire. Even when scientists do uncover the rare trace of an ancient blaze, it can be hard to determine whether it was created by people or ignited by lightning.

The oldest evidence for human ancestors using fire, dating back to between 1 million and 1.5 million years ago, comes from a cave in South Africa. Human ancestors left behind tens of thousands of fragments of bones from the animals they butchered to eat. Of those fragments, 270 show signs of having been burned in a fire.

But clues like these don’t offer clear proof that those ancient people knew how to make a fire. They may have just stumbled across a wildfire from time to time, and figured out ways to take advantage of it. They might have learned to light a stick from the fire, and then carry the ember back to their cave to cook a meal.

But that approach had its limits, Dr. Ashton noted. “You’re dependent on local lightning strikes,” he said. “It’s very unpredictable, and you can’t rely on it.”

A crucial step took place when early humans figured out how to make fires on demand, either by using rocks to create sparks or rubbing a piece of wood until the friction started a flame. “Once you can make fire, all those problems evaporate,” Dr. Ashton said.

Dr. Ashton and his colleagues caught their first glimpse of ancient fires in 2013, as they were digging at an archaeological site called Barnham in eastern England. For decades, researchers had found ancient tools and other signs of early humans there. In 2013, Dr. Ashton and his colleagues found something new: pieces of oddly broken flint.

Only an intense heat could have shattered the hard rocks. But Dr. Ashton and his colleagues couldn’t determine if the fire that broke the Barnham flints had been created by humans or lightning.

For years afterward, the researchers returned to Barnham hoping to tackle that question, without any further success. Finally, on a summer day in 2021, Dr. Ashton had a thought. As he prepared to take a nap under an oak tree, he recalled how, a couple of years earlier, he had glimpsed an intriguing streak of red clay. The nap could wait.

“I thought, I’ll have a little poke around,” Dr. Ashton said.

He found the red streak, and quickly realized that it was a two-foot-wide band of burned ancient soil. Had humans burned it, or had lighting? Dr. Ashton and his colleagues put the two possibilities to a test.

Over the next four years, they analyzed the chemistry of the sediment, while conducting further digs around it. Eventually they determined that, about 400,000 years ago, the site had been a watering hole, which Neanderthals probably visited in search of game. [Continue reading…]