Archaeologists are not saying hominins were using fire at Evron Quarry in northern Israel a million to 800,000 years ago. They’re saying they have developed spectroscopic techniques that can detect whether ancient stone tools were unnaturally heated, even if no visible sign of the fire remains.
And, wondrously, their results indicate that hominins at the time of the Lower Paleolithic were indeed using fire at Evron, Zane Stepka, Ido Azuri and Filipe Natalio of the Weizmann Institute of Science, with Liora Kolska Horwitz of the Hebrew University and Michael Chazan of the University of Toronto, explain Monday in PNAS.
This discovery lines up with the extremely scanty but intriguing evidence that fire may have been key to human evolution going back to the dim reaches of our ancestry. We were, possibly, the Cooking Ape.
An elephant has an accident
Might one have expected evidence of ancient fire at Evron? From the perspective of what we know about human evolution, possibly; from the actual evidence found at Evron to date, no.
They certainly didn’t start with any such expectations of detecting any, explains lead author Stepka. Their research was driven by pure scientific curiosity.
“When Evron was excavated in the 1970s, they looked for evidence of fire but didn’t find any,” she says, discounting one badly burned elephant tusk.
- ‘Galilean Man’ Invented Pyrotechnology Over 300,000 Years Ago, Team Suggests
- Fire Tamed 350,000 Years Ago?
- Stone Tools From 800,000 Years Ago Show Advanced Planning, Archaeologist Says
Why did they think they might find evidence of fire at Evron? Partly because of previous work by Prof. Naama Goren-Inbar and colleagues, demonstrating that hominins were using fire at Gesher Benot Yaakov in northern Israel at the same time, about 800,000 years ago. That is roughly contemporaneous with Evron (though if one calculates sapiens' evolution as taking place in about 200,000 to 300,000 years, that's a pretty wide margin of error.)
Moreover, Gesher Benot Yaakov featured small burned flint fragments in a distribution that suggested non-randomality, i.e., the archaeologists suspect they found actual early hearths.
Evron is an open-air site on the coastal plain of Western Galilee, and those excavations decades ago had detected hominin presence in the form of stone tools. No signs of fire were found: no visual evidence of heat-related “trauma” of the stone tools, no hearths – with the exception of that single burned elephant tusk. We’re going to get back to that tusk. But the poor beast could have accidentally been caught in wildfire, alive or post-mortem.
Now the new suite of spectroscopic techniques the team developed has identified that flint tools at Evron, small flakes and retouched flakes, cores and a small number of “poorly made” handaxes (oh, the shame) had been exposed to a wide range of temperatures. Ditto some of the animal bones: analysis suggests they had been heated to more than 600 degrees Celsius (1,112 degrees Fahrenheit). Not all the bones, mind you.
Their techniques involved harnessing artificial intelligence. “We tested a variety of methods, among them traditional data analysis methods, machine-learning modeling and more advanced deep-learning models,” says Azuri, who headed the development of the models. “The deep-learning models that prevailed had a specific architecture that outperformed the others and successfully gave us the confidence we needed to further use this tool in an archaeological context having no visual signs of fire use.”
AI could find “hidden patterns,” the team explains – thereby elucidating the temperature to which the stone tools were heated.
The team cautions that the evidence of fire detected at Evron by their new technique could have resulted from wildfire, not necessarily pyrotechnology. Yet their new techniques could enrich investigation of our truly distant past. Since its identification has depended on visual clues so far, the early exploitation of fire is probably under-recognized and underestimated, they posit.
The cooking erectus
Who actually lived at Gesher Benot Yaakov (aka “Daughters of Jacob Bridge”) and Evron? We do not know. Hominin fossils are rarer than people tend to assume and there were none in these two sites.
We do know the people at Gesher Benot Yaakov ate elephants and quadrupeds; they snacked on gerbils and probably anything they could catch that didn’t catch them first; they embraced nuts, fruits and plants. Remains of their meals have been found and identified, just not of the hominins.
The occupants may have been Homo erectus, but could have been some other species, Natalio says.
Some believe hominins, possibly early erectus, had at least some sway over fire almost 2 million years ago in Turkana, Africa. The evidence? A greater incidence of fire hallmarks detected near archaeological sites of these hominins than in nearby locations. That suggests the Turkana fires were contained, not raging landscape-wide conflagrations.
Is that proof? No, but it is intriguing – and in any case, it doesn’t mean these hominins knew how to ignite a fire from scratch, which is one criteria of “controlling” it.
In other indirect and hypothetical evidence of primordial fire utilization, it has been suggested that our distant ancestors underwent profound morphological changes almost 2 million years ago: the brain grew bigger as the gut shortened, which could indicate improved exploitation of our food and time. How? Possibly, cooking.
Cooking meat not only eliminates pathogens such as the demon salmonella, but renders our protein digestion more efficient. The primatologist Richard Wrangham, who isn’t connected with this research, has argued that transitioning from raw to cooked food improved our nutrient gain and spared us hours a day of chewing raw meat – freeing us to do other things, such as hunt more meat.
Separate research by Prof. Ran Barkai and colleagues at Tel Aviv University indicates that at least a couple of million years ago, hominins moved heavily toward carnivory, and the ability to roast that leg of elephant would have been helpful.
In addition, the warmth of the fire could theoretically have helped us lose our fur once and for all, freeing us from at least some parasites. We are the only primate to have bare skin, which did not evolve because of subterranean or marine lifestyle (being able to swim does not make us the “aquatic ape”); and we are the only primate to use fire – though the one doesn’t mean it caused the other. Indirect evidence suggests that our furlessness may have evolved hundreds of thousands of years or more before our ancestors discovered the charms of flames.
But anyway, realizing that fire is useful, and subsequently learning to tame it, had to have been turning points in our evolution. And now science can move beyond identifying early use of fire primarily by observation of its effects in the form of hearths, blackened tools and charred bones.
But maybe the Evron fire they detected despite the absence of visual signals was a natural wildfire?
“We have two pieces of evidence that could point toward the use of fire versus natural fire: differential temperatures in the lithics [stone tools] located at the same height; and only the tusk seems to be burnt,” Natalio answers.
Ah, that burnt tusk. It actually supports the hypothesis that the fire had been intentionally cultivated, not just the result of a passing lightning strike and wind; it takes prolonged exposure to fire for a tusk to burn, he explains.
Is it hypothesized that the hominins could control fire a million to 800,000 years ago? There is no consensus as to what “control fire” means, Stepka explains. Some think it all began when one day Og or Magog realized that an animal caught in a fire tasted terrific; and/or that s/he could stick a deer into an incidental fire; or s/he could pick up a burning bush and haul it into the cave.
In short, it is widely assumed that the first utilizers of fire didn’t know how to ignite one. As a camper who sometimes wishes to light a fire, Stepka can attest that doing so from scratch is not easy – which wood is optimal being just one difficulty. At a personal level, it makes sense to her that the development of “control” took time; hominins could start with a burning stick and actual pyrotechnology came later, she says.
Before Evron, only five sites around the world had evidence of fire earlier than 500,000 years, says Natalio, one of which had been Gesher Benot Yaakov. Now there are six.
Of the other four, three are in Africa (one at Wonderwerk, the cave that keeps on giving) and one is in Spain, Stepka adds. Wonderwerk by the way has been dubbed the oldest home, having been occupied for the last two million years. It also features evidence of fire use from about a million years ago.
So did hominins a million years ago have fire, and control it? There just isn’t enough data: neither Wonderwerk nor the five other sites do not create any certainty. Much more work will be needed, Stepka says.
But before you shrug and wonder what the great trick is in lighting a fire, you try to do it outdoors, without a match.