When did man tame fire?
Early humans probably used fire from wild sources, such as lightning strikes, as early as a million years ago. But direct evidence of humanchecked burning from so long ago is hard to find. In June 2022, a group of Israeli scientists and a colleague from Canada published a new paper in Proceedings of the National Academy of Sciences, which describes a new use of artificial intelligence (AI) to seek evidence for controlled fires by early humans. They focused on stone tools excavated at Evron Quarry, a Mediterranean site in Israel that was extensively excavated in the 1970s. The new work suggests that early humans who inhabited the site used controlled fires to cook food and make tools as early as 1 to 0.8 million years ago.
The scientists used artificial intelligence to detect subtle changes in the atomic structure of ancient rocks found in the Evron quarry. It is possible that these stones were burned in some of the earliest known campfires.
Rewriting the story of tamed fire
The scientists were looking for a way to identify evidence of fire, in artifacts that showed no visible signs of fire. The authors said of their study†
[It] reveals the presence of fire in a Lower Paleolithic site with no visible signs of pyrotechnology [controlled fire in ancient times]† And adds a new Lower Paleolithic site to a handful of archaeological sites with evidence associated early humanoids-produced artifacts and fire.
And that’s exciting! It suggests that artificial intelligence could be used as a tool to learn more about our early ancestors. To that end, this research group wants other researchers to use their technique, take a second look at places where early humans lived, and may have left behind other hidden signs of their early fire control.
Thus, the use of artificial intelligence could change how we, modern humans, tell the story of our evolutionary journey.
AI sees what we couldn’t see before
So these researchers used AI to to see which previous scientific research had not previously been able to see.
In the Evron Quarry, archaeologists unearthed simple flint hand axes, flint knives and evidence of their creation in the late 1970s, as well as animal remains. What that excavation failed to reveal was clearly visible evidence of fire use at the site. This was pointed out in the June 13, 2022 research paper, published in the Proceedings of the National Academy of Sciences† Researchers suspected it should be there, given strong evidence of fire use at nearby sites from the same era:
There is no visual evidence of heat-related features on these materials, ie redness of soil, jar lids, discoloration or presence of shine on flint implements, warping, cracking, shrinking or color change of animal remains.
To find that evidence today, the team created an in-depth tutorial that the AI can use. The program focuses on recognizing the effects of fire on flint samples heated to high temperatures in the laboratory. The AI was then able to see the same signs of fire on the Evron Quarry artifacts.
A New Look at Old Evidence
Because the proof of heat is so difficult to detect, researchers had another challenge, which was to develop a way to search for signs that carry the artifacts and bones found at Evron Quarry to this day. Essentially, they developed a spectroscopic “thermometer” based on what’s called Raman spectroscopy, which measures the absorption of ultraviolet light. Add to that the deep learning algorithms developed by these researchers…and the AI could distinguish burnt and unburnt pieces of modern flint and even reveal the temperatures at which they burned.
So the scientists had a new, reliable “thermometer”. It showed them that tools from the Evron Quarry site had been heated to a scorching 1112 degrees Fahrenheit (600 degrees Celsius). She said in their newspaper:
However, a spike in the data developed at a much more moderate 752 degrees Fahrenheit (400 degrees Celsius). And this was the temperature to which most flint tools were exposed.
Animal bones showed signs of being cooked at temperatures in a similar range when tested using more traditional techniques. This included gazelles, cervids, aurochs, hippopotamus, two different species proboscides and a suid†
Fire makers or fire seekers?
The researchers admit there may be other explanations for how the animal remains and tools were heated to such extremes. For example, forest fires can still be the cause. Still, they said the discovery of so many objects in the same location is telling: The arrangement of the artifacts — when they were first excavated in the 1970s — suggests the people who worked and cooked there returned time and time again.
As it turned out, the site had been in use for generations. And that suggests the fires were set on purpose.
In short: when do people tame fire? It is likely that the early humans used fire from lightning strikes a million years ago. But when did we learn to master it? An AI-driven study — released in June 2022 — found evidence that hominins tamed fire as early as a million years ago.