The mastery of fire opened the way to entirely new worlds for early humans, but how and when this mastery occurred has been lost to time. However, some fragments of burnt material suggest that the taming of the flame may have started as early as 1.5 million years ago.

Now, scientists have used artificial intelligence to detect hidden signs of campfires at a Lower Paleolithic site in Israel dating back about 1 million years.

The identification of fire in archaeological sites is usually based on visual clues such as reddening of the soil, discoloration, deformation, cracking and shrinkage of materials.

In the new study, the researchers used a spectroscopic “thermometer” that can detect minute chemical changes analyzed by deep learning algorithms that can estimate the exposure of rocks and fossils to heat.

The mastery of fire opened the way to whole new worlds

Archaeologist Zane Stepka of the Kimmel Center for Archaeological Sciences in Israel and his colleagues used this “thermometer” on flint artifacts from a site in Israel, dated between 1.0 and 0.8 million years ago, he writes Science Alert.

The artifacts were found alongside animal fossils in yellow-gray sand overlying a red clay. There were no obvious visual indications of the use of fire at this site.

But the AI ​​”thermometer” revealed subtle chemical signatures suggesting that a number of stone tools and pieces of tusk had been heated to various temperatures, indicating they had come into contact with fire.

While the team cautions that they cannot completely rule out fires at this point — because the site was in an open location — the grouping of tools and bones suggests that early humans controlled fire.

How did our ancestors tame the flames?

It was previously thought that the use of fire by humans around 150,000 years ago was only opportunistic, such as Australian raptors intentionally spreading flames to help drive away prey. But if these fires were indeed confined to the camps, this suggests otherwise.

Only a handful of archaeological sites this old show signs of early human artifacts alongside evidence of fire, and this adds weight to the idea that our ancestors were already using this powerful technology.

Further use of the new technique could help us learn more about when and how we tamed the flames, the researchers say.

“Reexamination of artifacts excavated from other Lower Paleolithic sites, including those located in the Levant, could potentially broaden our spatiotemporal understanding of the relationship between early humans and fire,” the team writes.

This research was published in PNAS.

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