Why Scientists Argue About Which People Mastered Fire

What makes humans human.
Oct. 5 2012 4:00 AM

Who Mastered Fire?

The heated archaeological debate about which hominids first started cooking.

View taken on July 8, 2010 of a mannequin of a Tautavel Man, an ancestor of Neanderthal Man, in the Caune de l'Arago cave.
Mannequin of a Tautavel Man—would he have had known how to make fire?

Photo credit by Eric Cabanis/AFP/Getty Images.

Richard Wrangham, an anthropologist at Harvard, claims that hominids became people—that is, acquired traits like big brains and dainty jaws—by mastering fire. He places this development at about 1.8 million years ago. This is an appealing premise no matter who you are. For those who see cooking as morally, culturally, and socially superior to not cooking, it is scientific validation of a worldview: proof that cooking is literally what makes us human. For the rest of us, it means we have a clever retort the next time one of those annoying raw-food faddists starts going on about how natural it is never to eat anything heated above 115 degrees Fahrenheit.

L.V. Anderson L.V. Anderson

L.V. Anderson is a Slate assistant editor. She edits Slate's food and drink sections and writes Brow Beat's recipe column, You're Doing It Wrong. 

There’s one problem with Wrangham’s elegant hypothesis: It’s hardly the scientific consensus. In fact, since 2009, when Wrangham explained his theory in the book Catching Fire, several archaeologists have come forward with their own, wildly divergent opinions about what is arguably the oldest intellectual property debate in the world. Who really mastered fire, in the sense of being able to create it, control it, and cook with it regularly? Was it Homo erectus, Neanderthals, or modern humans?

A brief primer on these species: H. erectus originated about 1.8 million years ago. These hominids were about as tall as modern humans, but probably hairier and definitely dumber. It’s thought that both Neanderthals and Homo sapiens evolved from H. erectus, with Neanderthals emerging about 600,000 years ago (and going extinct around 30,000 years ago) and modern humans emerging around 200,000 years ago (and still going strong). Neanderthals were shorter and had more complex societies than H. erectus, and they’re thought to have been at least as large-brained as modern humans, but their facial features protruded a little more and their bodies were stouter than ours. It’s thought that Neanderthals died out from competing, fighting, or interbreeding with H. sapiens.

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According to Wrangham, H. erectus must have had fire—just look at their anatomy! H. erectus had smaller jaws and teeth (and smaller faces in general), shorter intestinal tracts, and larger brains than even earlier hominids, such as Australopithecus afarensis, for instance, who were boxier, more apelike, and probably duller. Wrangham argues that H. erectus would not have developed its distinctive traits if the species hadn’t been regularly eating softer, cooked food.

This hypothesis stems from a few modern observations. When you eat cooked food, you have access to many more calories than if you eat the same food raw. There are two reasons: Our digestive systems can extract more calories from a cooked steak (for instance) than a raw steak, and it takes much less energy to cook and eat a steak than to gnaw on a raw one for hours. Access to cooked food means a hominid no longer needs enormous teeth to break down all that raw meat and roughage into swallowable hunks, nor does it need as robust a digestive system to process it all. The combination of more calories and less complicated intestines means more energy can be devote to cogitating—hence H. erectus’ relatively big brains, which suck up a lot of calories. As evidence for his theory, Wrangham likes to point to the fact that modern-day humans can’t thrive on an all-raw diet—raw foodists tend to stop menstruating, precluding reproduction.

Wrangham’s theory is elegant, but the archaeological record is a little more complicated. There is definitely evidence of fire around 1.6 million years ago in what is now Kenya. But archaeologists dispute whether this was manmade or natural fire. Further complicating Wrangham’s hypothesis is evidence that hominids may not have brought fire with them when H. erectus moved out of Africa into Europe around a million years ago. If fire was as transformative and beneficial as Wrangham said it was, you’d think our ancestors would have brought it with them when they moved to colder climes—or died out if they were unable to do so.

If H. erectus didn’t bring fire mastery to Europe, who did? Archaeologists Wil Roebroeks of Leiden University in the Netherlands and Paola Villa of the University of Colorado Museum found evidence for frequent use of fire by European Neanderthals between 400,000 and 300,000 years ago. Roebroeks and Villa looked at all the data collected at European sites once inhabited by hominids and found no evidence of fire before about 400,000 years ago—but plenty after that threshold. Evidence from Israeli sites put fire mastery at about the same time. H. sapiens arrived on the scene in the Middle East and Europe 100,000 years ago, but our species didn’t have a discernible impact on the charcoal record. Roebroeks and Villa conclude that Neanderthals must have been the ones who mastered fire.

One of the beautiful things about the archaeological record is that archaeologists are always willing to debate about it. Attributing fire to Neanderthals is an overly confident reading of the evidence, according to archaeologist Dennis Sandgathe of British Columbia’s Simon Fraser University. Of course the number of campsites with evidence of fire increased between 1 million and 400,000 years ago, he says—the number of campsites, period, increased during this time in proportion with population growth. But that doesn’t mean the use of fire was universal among European hominids—there are plenty of Neanderthal campsites out there that show little or no evidence of fire, and Sandgathe has personally excavated some of them. What’s more, Sandgathe told me when I asked him about Roebroeks’ and Villa’s data, “We actually have better data than they do when it comes to Neanderthal use of fire.”

According to Sandgathe and his colleagues, hominids didn’t really master fire until around 12,000 years ago—well after Neanderthals had disappeared from the face of the planet (or merged into the human gene pool via interbreeding, depending on your view). Sandgathe and his colleagues excavated two Neanderthal cave sites in France and found, surprisingly, that the sites’ inhabitants used hearths more during warm periods and less during cold periods. Why on earth would Neanderthals not build fires when it was freezing outside? In “On the Role of Fire in Neandertal Adaptations in Western Europe: Evidence from Pech de l’Azé IV and Roc de Marsal, France,” Sandgathe advances the hypothesis that European Neanderthals simply didn’t know how to make fire. All they could do was harvest natural fires—those caused by lightning, for instance—to occasionally warm their bodies and cook their food. (This explains why Sandgathe found more evidence of fire from warm periods: Lightning is far less common during cold spells.)

Roebroeks and Villa think Sandgathe’s reasoning is flawed: After all, there isn’t evidence of fire at every modern human campsite, either, when you look at sites from the Upper Paleolithic period, which concluded about 10,000 years ago. “However, nobody would argue that Upper Paleolithic hunter-gatherers were not habitual users of fire,” they wrote in a response to Sandgathe et al.’s criticism of their work. Wrangham, meanwhile, thinks both Sandgathe et al. and Roebroeks et al. ignore some critical nonarchaeological evidence: his point that contemporary humans can’t survive on a diet of uncooked food. Accepting Sandgathe’s hypothesis, Wrangham wrote in an email, “means that the contemporary evidence is wrong, or that humans have adapted to need cooked food only in the last 12,000 years. Both suggestions are very challenging!”

Why on earth can’t scientists agree on whether people mastered fire 1.8 million years ago or 12,000 years ago? That’s a 150-fold difference. Well, figuring out who burned what, when, is not an easy business. For one thing, archaeologists can’t always tell what caused a fire: a volcano, for instance, a lightning strike, or hominid ingenuity. And even if there is clear evidence of hominid fire use—a hearth at a formerly inhabited cave, for instance—it’s almost impossible to tell whether it was created by people from scratch or merely stolen from a natural fire and then transported to a hearth, where it was kept alive as long as possible. Scientists call this kind of fire use opportunistic.

What’s more, even when people were creating fires, the evidence of said fires doesn’t always stay put. Ashes have a tendency to blow away instead of embedding themselves neatly in the archaeological record, while water can take evidence of fire from its original location and carry it someplace completely different. Then there’s human error: As Sandgathe et al. write in their discussion of the available evidence, “There are … examples where residues originally interpreted as the remains of fires are later identified as something else.” (I hate it when that happens.) At one site in China, for instance, layers of earth originally believed to be ashes were later revealed to be silt and unburned bits of organic matter.

Archaeological methods are improving, and they may well end up bearing out Wrangham’s hypothesis. In a paper published earlier this year, archaeologists used advanced techniques (known as micromorphological and Fourier-transform infrared microspectroscopy) to examine sediment and reveal evidence of fire at a million-year-old South African cave site.

Wrangham is also hopeful that other disciplines will provide evidence for his theory. “I suspect genetics will help,” he says. “If we can pin down the genes underlying the adaptation to cooked food, we may be able to date the control of fire close enough to settle the big question.”

“Sure, that would be pretty compelling evidence,” admits Sandgathe. But he’s hopeful that genetics will bolster his hypothesis: that Neanderthals survived frigid glacial periods not because they regularly used fire, but because they had thick body hair. “At some point someone may announce the discovery of the gene or genes that code for thickness of body hair, and so could answer that question,” he says.

Judging from the way things are going, this debate may rage on for a good while longer. And there is room for more than one right answer: It’s possible that different groups mastered fire independently of one another at different points in time. But laypeople can take comfort in knowing that, even if we don’t know yet who first mastered fire—our simple ancestors almost 2 million years ago, our more advanced cousins 400,000 years ago, or our direct antecedents about 10,000 years ago—there’s no doubt who holds the intellectual property rights to it today. We even put it in an oven and made it our own.