Earliest Use of Fire: Not for Cooking?

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Many animals recognize fire and avoid it, and some have even learned to indirectly exploit it. Certain raptors and predators apparently realize that brush fire creates opportunity to catch fleeing rodents, for instance.

Yet only the Homo genus achieved control over the flame: being able to light it at will, nurse the embers and douse. The burning question is why we did that. There is a reason animals avoid fire: It's terrifying at best and deadly at worst.

But once it can be controlled, fire can keep away the nasties. It can transform hard roots into mash and raw, tough meat into mouth-watering roast. Much later, Neanderthals and sapiens would discover that heating the materials would facilitate tool manufacturing as well. But which, if any, of these behaviors drove archaic humans to embrace and develop this dangerous element that arguably led to our domination of the planet and the rise of the military-industrial complex?

So far, the main candidate driver of early fire use has been cooking, plus social elements: We can easily imagine communal huddles by a warm fire on cold nights, swapping stories while supping in the circle of light carved out of the blackness. Cooking meat and plants rendered their nutritive components more accessible and as our nutrition improved, our brain size increased, according to this thesis.

Now archaeologists Ran Barkai and Miki Ben-Dor of Tel Aviv University propose a radically new theory for the earliest utilization of fire at least a million years ago, based purely on bioenergetic analysis, because the math behind cooking as the primary driver of fire adoption doesn't add up.

What does bioenergetic analysis even mean? If a human expends 2,500 calories a day, that is his bioenergetic cost of living. To remain alive, he must eat 2,500 calories a day, which is his bioenergetic income, Ben-Dor explains to Haaretz by telephone.

So bioenergetically, producing fire costs more than cooking can repay. You would expend more strength on producing fire than you will gain from cooking the food you hunt and gather, they calculated. "First of all, you have to collect the wood," Ben-Dor elaborates the cost. "The longer you stay in a place, the more expensive that becomes because first you collect closest, then go further and further."

Resource depletion will naturally depend where the hominins are living, he adds. "If you are in a forest with a lot of dead wood, and it doesn't rain, it's okay – but in the middle of the desert, it's another situation." (Making an open-air fire in the rain using wet wood indeed sounds sub-ideal.) At best collecting wood is energetically expensive, as has been empirically demonstrated separately.

Okay. Dry wood collected, it needs to be ignited, then the fire needs nursing; in effect, babysitting. Meanwhile the extra caloric return from cooked food, as opposed to raw, is lower than people may realize, they calculate.

That sounds surprising, given how accepted it has become that we cooked so we became big-brained clever clogs, but Ben-Dor suggests that the empiric facts of how many net calories cooking adds had not been widely checked, and it's not a lot.

If not cooking, why did we adopt fire? Primarily to scare off scavengers hoping to steal our hunt and to desiccate leftover meat and fat, preventing it from rotting in order to eat later, Ben-Dor and Barkai propose in the journal Frontiers in Nutrition. We would also be protected from predators by the demon flame. Cooking was a secondary benefit.

"For early humans, fire use was not a given, and at most archaeological sites dated earlier than 400,000 years ago, there is no evidence of the use of fire," Ben-Dor adds. "Nevertheless, at a number of early sites there are clear signs that fire was used, but without burnt bones or evidence of meat roasting. We understand that early humans at that time – mostly Homo erectus – did not use fire regularly, but only occasionally, in specific places and for special purposes. The process of gathering fuel, igniting a fire and maintaining it over time required significant effort, and they needed a compelling, energy-efficient motive to do so. We have proposed a new hypothesis regarding that motive."

Fire a million years ago

For the purposes of the paper, Ben-Dor and Barkai define early fire use as spanning from 1.9 million to 780,000 years ago based on accepted evidence of fire in prehistoric archaeological sites. The literature they studied has nine, including Gesher Benot Ya'akov and Evron Quarry in Israel, six sites in Africa, and one site in Spain.

This was the time of Homo erectus, and while some hominins had adopted the cave life starting about 2 million years ago, most hominin archaeology sites are open-air.

They lived outside. Not in a cave, Ben-Dor clarifies. Gesher Benot Ya'akov – where giant elephants trumpeted and hominins lived with them cheek by jowl and likely ate them too – was an open-air site.

So when we think of lighting and nursing a fire, it wasn't protected from the elements and neither were the hominins and their meals. That, says Ben-Dor, is one reason why many anthropologists argue that fire use probably began and likely was broader than we realize – finding any evidence at all from deep prehistory is practically a miracle, let alone in outdoor contexts.

In nature, fire is usually caused by lightning (or a volcano). If a hearth is found deep inside a cave, or evidence indicates repetitive use of a certain spot for burning - the fire had to have been deliberately transported or lit there. Traces of wood ash inside Wonderwerk Cave in South Africa from a million years ago are argued by some to represent not only fire use but control (and argued by others to represent floodwaters transporting bushfire debris).

At Israel's Gesher Benot Yaakov, archaeologists think that concentrations of burned flint imply open-air hearths and control of fire 780,000 years ago. In China's Zhoukoudian caves, charred bones and hearths were found from 400,000 years ago; they were reported almost a century ago, more recently debunked – and even more recently, reinstated.

Whether or not any of the hominins in these cases were lighting the fire is unclear, but they were using it, and many are confident they were, could have, had to have been able to ignite fire as well.

Ben-Dor points out that all you have to do to create a spark is knock a flint against another stone, and at least some hominins were doing that for over three million years.

Where the wild things aren't

Their hypothesis for the primary early use of fire therefore considers the context of the open savannah and their separate finding that hominins preferred to hunt the biggest animals, which had the most fat.

If the group brings down an elephant (or finds a dead one to exploit), there are consequences.

In previous work, Barkai, Ben-Dor and colleagues demonstrated a correlation between hominin spread and megafaunal extinction. Big animals reproduce slowly, and we ate them faster than they could reproduce. How exactly Homo erectus obtained large animals is debated – archaeologist Gonen Sharon at Gesher Benot Ya'akov posits that nobody hunted an elephant with a hand axe, because if you hit an elephant with a rock, it will get angry.

But Lower Paleolithic sites are abound in evidence of cut marks on megafaunal bones. Hominins were obtaining megafauna somehow. And if they bagged a proboscidean or rhinoceros, they couldn't have eaten it all in a day or two, even if a group as big as say, 25 people, gathered for the feast. Just dismembering it using stone tools could take days.

There will be leftovers, and predators and scavengers from the hyena to the lion to the jackal will smell the carcass and converge. Cats, it has been shown to some dubiety, can pick up scent at least up to 4 kilometers. The hominins also probably smelled appetizing enough. How is a clawless and effectively toothless hominin to protect the precious carcass and himself?

So what have we? Making fire is costly. Losing most of your kill to hyenas is very costly. The contribution of cooking to the nutritive value of meat and plants is small.

Barkai and Ben-Dor don't object to the mastery of fire being a turning point in our evolution. They object to cooking as the initial impetus for its adoption.

In other words, Prof. Richard Wrangham - the author of the cooking hypothesis - they propose that preserving the meat from rotting or being eaten by other species would have had a higher positive effect on energy gain for early Homo than by increasing the net caloric gain from meat being cooked, and he agrees that they couldn't eat an elephant in a day or even a few.

"[Their] proposal is attractive in stressing the value of fire as a meat-preserver. I agree with them that the problem of bacterial decomposition of meat would have been important for early Homo. Indeed, my research team has previously noted the value of fire as a preserver, using direct experiments," Wrangham tells Haaretz by email.

But he stands by his hypothesis that cooking would have been responsible for such changes as reduced molar size and smaller guts, which Ben-Dor and Barkai buck. They alternatively suggest that possibly physical reduction of food like by mashing tubers and/or eating fat could have increased digestibility enough to account for the anatomical changes but Wrangham does not agree, pointing to the modern raw-food fad.

"Raw-foodist routinely use electric blenders to reduce agricultural foods to liquid form. Yet those raw-foodists, despite having access to high-quality foods all year round, are essentially so starved of energy that the reproductive system of the average woman on such a diet closes down to the point where she cannot reproduce," he says.

A raw foodist today is not the same as an erectus. Ultimately, Wrangham applauds a key aspect of the new thesis: "I very much like BDB's idea that preservation of prey would have been an invaluable consequence of the control of fire; and I agree with them that Homo would have started cooking as soon as they controlled fire," he says. "My disagreement is only that cooking still seems to me likely to have been a vital consequence, particularly during periods of low availability of preferred foods."

By which he means, migratory megafauna wouldn't have been in season all year round, leaving fat-dependent hominins to starve. "These periods when they must rely on "fallback foods" are critical influences on evolutionary adaptations. I contend that such periods would have occurred, during which fat would have been insufficiently available to allow early Homo to survive. During such periods, cooking of various items of low digestibility would have been vital," Wrangham says.

Or it could be that once the hominins noticed fire, it all came together - scaring off predators, cooking and smoking. Could that be? Ben-Dor spells out that they aren't saying this is how it was; they're saying this is what bioenergetics analysis produces.

How would open-air hominins even come up with the idea of fire frightening away scavengers of their precious mega-animal, let alone cutting leftovers into strips and smoking them? Asked to speculate, Ben-Dor obliges.

They could easily observe that fire frightens predators. They had a problem keeping scavengers off their kills, and one day, a smart hominin had a eureka moment – I will light a fire, Ben-Dor suggests.

"That is the very process that led to the development of the brain!" he continues the speculative line. In a competition, the smarter one who could light fire would be likely to prevail because their meat could be protected, while a neighbor who couldn't do that lost his meal and didn't procreate.

And smoking meat? In Mother Nature, one encounters the odd naturally desiccated corpse (not mummified, just dried out) – in the dry season, for instance. Or one may encounter a cadaver that a leopard left in a tree, as leopards do, but this leopard had a terrible accident and didn't return to finish the food, and a hominin happening along found it and recognized the miracle of shriveled dry meat: It lasts longer.

We are a proud species, ion awe of our accomplishments, and it's a little rough to admit that "ape-men" a million years ago could be that wise, Ben-Dor adds. "But when you live in nature, you know a lot. You accrue know-how that today we don't know or understand anymore." The smell of roasting meat may spur dubiety about the theory that we didn't embrace the fire in order to cook the elephant, but, he sums up: The smell just doesn't justify the energetic cost. Cooking didn't provide a bioenergetics benefit that anybody would notice, but preventing theft and decay did.

Once mastery of preservation has been achieved, a single elephant or other giant animal whose flesh and fat are cured can support the tribe for awhile. One paper on Neanderthals hunting and processing gigantic straight-tusked elephants in Europe 125,000 years ago points out that the proboscids could weigh as much as 13 tons, the Neanderthals were clearly butchering and eating them until they went extinct about 100,000 years ago and what could they do with all that meat? That team also suggests that the prey was stripped of meat, and it would be dried or smoked for consumption over time.

In short, once hominins had grasped the concepts of preservation, Ben-Dor and Barkai point out that a single elephant could support the group over time. A 10-ton elephant would have yielded more than 2,500 daily meals of 4,000 calories apiece, according to the 2023 paper. Ben-Dor sums up that the meat and fat of a single elephant would contain millions of calories, enough to feed a group of 20 to 30 people for a month or more.

"A hunted elephant or hippopotamus was thus a real treasure, a kind of meat and fat 'bank' that needed to be protected and preserved for many days, since it was coveted not only by predators but also by bacteria," he says. "I think what happened is they lit the fire and dried the meat." Possibly they laid it in strips over sinews stretched over the open fire, serving as string. They wouldn't have dried meat in caves anyway, because of the smoke hazard, he adds, and wishes to stress that adoring the smell of roast cow is a cultural thing. Who knows what they thought culinarily appealing. Peoples from the Northern Hemisphere reportedly prefer their seal raw.