When Did Early Humans Start Using Fire? To Find Answers, Scientists Enlist Artificial Intelligence

By analyzing flint tools, researchers find new evidence of an 800,000-year-old fire in northern Israel

Flint tools
Researchers analyzed flint tools found at the Evron Quarry in Israel. Photo by Zane Stepka / courtesy of the Weizmann Institute of Science

While scientists have long hypothesized that early humans started using fire about one million years ago, evidence dating back that far is difficult to come by. 

Now, artificial intelligence might be able to change that. In a study published this month in the Proceedings of the National Academy of Sciences, researchers from the Weizmann Institute of Science may have found the remnants of an 800,000-year-old fire in Israel.

Previously, to determine whether a fire had once taken place, researchers relied on finding straightforward evidence (like remnants of charcoal) and analyzing bones to detect atomic changes, writes Science’s Michael Price. But while both methods are effective, evidence of this kind is rarely found at ancient sites. 

Artifacts that are abundant, however: stone tools, often made from flint. 

The researchers heated pieces of flint to different temperatures and then analyzed them using spectroscopy—a technique that measures the absorption of light—in an attempt to determine whether the flint had been burned. However, the resulting data was too complex to be of much use.

“[T]he changes were so subtle that we couldn’t rely on them,” Filipe Natalio, an archaeological biochemist at the Weizmann Institute, tells Science. “That’s when we turned to artificial intelligence.”

Realizing that the data might hold patterns too complex for humans to parse, the team developed an A.I. program to help. Sure enough, the program was successfully able to tell the difference between burned and unburned flint, and it could even report how hot the material got.

Next, to test their program, Weizmann Institute researchers, along with scientists from the Hebrew University of Jerusalem and the University of Toronto, went to the Evron Quarry, an open-air archaeological site in northern Israel.

“When we started this project, the archaeologists who’ve been analyzing the findings from Evron Quarry told us we wouldn’t find anything,” says Natalio in a statement from the Weizmann Institute. “We should have made a bet.”

The site was first discovered in the 1970s; at that time, archaeologists found animal fossils and Paleolithic tools dating back to between 800,000 and 1 million years ago, according to the Times of Israel. None of them showed visible signs of being exposed to fire.

But when Natalio and his team tested their A.I. program on 26 flint tools previously discovered at the site, they found that they had been exposed to hot temperatures, some reaching as high as 600 degrees Celsius. They also analyzed the tusk of an extinct elephant from the site, which yielded similar results.

The team’s findings support the “cooking hypothesis,” the widely accepted belief that harnessing fire was a crucial step in human evolution. Until recently, though, only scant evidence existed to support that theory. Most evidence of fire dates to just 200,000 years ago, and only five archaeological sites have been found with evidence older than 500,000 years, according to the statement.

But now, Natalio says, “We may have just found the sixth site.”

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