When We Tamed Fire

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fire

. In the early 1980s, archaeologists working at a site in Kenya called Koobi Fora noticed some peculiar markings in the ground they were excavating: distinctive patches of reddish-orange sediment.

This wouldn't have been all that exciting, except that those patches looked a lot like the patches of baked earth left by camp

fire

s made by modern people in the area. Interestingly, the jaw of a fossil hominid and evidence that stone tools were made there had also been found at this site, approximately 1.6 million years ago. So this got researchers thinking: Was it possible that these red spots were signs of an ancient fire that was used by some of our distant ancestors, more than a million and a half years ago? Well maybe. There are still some important questions to be answered.

Could the hominids at this site have made fire? Or did they find some naturally occurring fire, such as from a lightning strike, and just use it for as long as possible? Our ancestors likely started out this way, taking advantage of fire as a passing natural phenomenon. But they finally took it a step further: They picked up a burning twig left by a forest fire and used it to start their own fires. The use of fire would not become truly visible in the archaeological record until it became widespread,

when

fire began to be used consistently at many different sites.

This could have been the moment in our history that caused an evolutionary change, causing an expansion into new environments. And

when

we learned to make fire whenever we wanted, it would forever change our relationship with the world around us. Now, the fact is that we don't know exactly when hominids harnessed the power of fire. And we're not entirely sure which species of our ancestors was the first to master it, although there is one candidate that seems more likely. And it wasn't us. However, we do know that the ability to make and use it has fundamentally changed the arc of our evolution.

The bodies we have today were shaped, in many ways, around the time we first domesticated fire. The use of fire in human history is notoriously difficult to study because fire is ephemeral. It is harder to see in the archaeological record than, say, stone tools, because it is a transient phenomenon that leaves little evidence. Ashes can easily blow away in the wind or be carried away by water. But we know that the use of fire has had enormous impacts on our bodies and our behavior. Therefore, some experts have observed the gradual changes in how hominids looked and how they lived, to hypothesize which of our ancestors may have mastered it.

The first impact that fire has had on our evolution is that it allowed us to cook food. And it's hard to overstate how important that was. The main advantage of cooking is that it breaks down food, making it easier to chew and digest. In fact, you can think of cooking as a way to start the digestion process, even before putting food into your body. Which sounds gross when I say it like that. It's actually delicious, but heat causes the large, complex molecules in food to break down into smaller, simpler nutrients. So, if you heat food with an external energy source, such as fire, you are saving the energy your body would have to invest in chewing and digesting the food if you had eaten it raw.

Cooking also breaks down plant toxins and kills pathogens. And again, this prevents your body from having to invest energy in defending itself from poisons and diseases. Together, these things make cooked foods much more energy efficient than raw foods, so you end up getting more calories from what you eat. And when you're trying to survive, every calorie counts. But of course, the other advantage of fire is that... it keeps you warm. Therefore, the use of fire probably helped our ancestors expand their geographic range, migrating to places with different climates and opening up a whole new world of ecological possibilities for our species.

Now, there is one hominid besides us that fits both descriptions (a species that needed a lot of calories and had to live in many different environments) and that is the first definitive member of our genus, Homo erectus. Some anthropologists propose that Homo erectus could have been able to cook food, based on its physical adaptations. Specifically, it had smaller teeth than its predecessors, suggesting that it did not need to engage in the intense chewing that a raw food diet would require. But perhaps more importantly, he also had many of the traits we know require a lot of calories, such as a larger body size, more muscle mass, and, most importantly, a larger brain.

And in terms of its ability to live in different environments, Homo erectus is the first hominid known to have migrated out of Africa, eventually spreading from what is now the Republic of Georgia to Southeast Asia. But here's the problem: Homo erectus dates back about 1.89 million years. But the earliest possible evidence of repeated and regular cooking does not appear until hundreds of thousands of years after their appearance. Likewise, Homo erectus began its excursions out of Africa hundreds of thousands of years before the first definitive evidence of the widespread use of fire. So how could fire have helped this species develop a larger body and brain and help it migrate to other places?

Well, as with many aspects of the study of the distant past, there are many dots to connect. And in this case... we are simply missing many points. So let's see what the evidence tells us: about the use of fire in general and then about cooking in particular. In recent years, anthropologists have returned to that red-stained site in Koobi Fora, Kenya. And recent excavations have turned up more definitive evidence of the use of fire than the red patches of dirt found in the 1980s. Archaeologists have discovered rock fragments with telltale signs of having been heated to high temperatures, as well as pieces of animal bones burned.

And these chunks of rock and bone appear to be grouped together in distinct patches. Which is important, because it suggests that the fires were small and intentionally set, and not a natural wildfire, which would have devastated the entire site. As for who set these fires, all of the burned rocks and bones were found in an area associated with artifacts that were likely made by Homo erectus. But no remains of those hominids are found there. Instead, the only hominid fossils at the site are of Paranthropus boisei, a smaller-brained species. The next oldest site with /widely accepted/ evidence of fire is a site in South Africa dating back 1 million years ago, at a place called Wonderwerk Cave.

There, archaeologists have found burned bones and plants, as well as larger, more complex stone tools, such as hand axes, known as Acheulean tools. These tools have often been associated with Homo erectus. And some experts have speculated that, also based on the date, Homo erectus may be the hominid that started those fires. Other, more recent evidence of fire has been found at a site in Israel called Gesher Benot Ya'aqov. And there, at a site that is approximately 790,000 years old, burned seeds, wood and flint have been found clustered in what researchers call ghost hearths: areas where fire might have been, but without a clear ring of stones for a campfire. .

These groups, and the fact that they occur over time at the site, suggest that the hominids who visited there were very familiar with fire and could create it any time they wanted. Again, no hominin fossils have been found there, but Homo heidelbergensis, a large-brained species that may have been the last common ancestor of humans and Neanderthals, is a candidate. So, that's what we know about when hominids used, and perhaps made, fires. But things get even more interesting when we try to find out which of our ancestors was the first to cook with it. Those pieces of burned bone found at Koobi Fora are not necessarily proof that hominids cooked meat regularly 1.6 million years ago.

Instead, as with the use of fire in general, anthropologists are much more interested in when cooking became widespread enough to really influence our evolution. And evidence of regular cooking behavior doesn't appear until very recently, at least in geological terms: about 350,000 to 400,000 years ago, in the eastern Mediterranean region known as the Levant. Here, another cave, called Qesem, preserves a large central hearth that was used repeatedly and, according to a group of researchers, was commonly used for roasting meat. The hominid teeth found in the cave resemble those of Homo sapiens and Neanderthals. But whoever was cooking in Qesem left many dismembered and burned bones.

Finally, there is still the question of when and where fire was used outside of Africa. If fire was so useful in fueling human migration, can we then trace its use around the world to retrace our steps? Well, the first species we have fossil evidence of outside of Africa is... you guessed it! -- Homo erectus, at a site called Dmanisi in the Republic of Georgia, dating back to 1.8 million years ago. But there is no evidence of a fire at the site, even though winter temperatures likely reached slightly below freezing. And again, as with cooking, we only see really strong evidence for the use of fire in colder climates much, much later: about 400,000 years ago in Europe, in two different sites.

At Beeches Pit in England, areas of sediment burned with heated stone tools and burned bones have been interpreted as remains of hearths. And in Schöningen, Germany, the evidence is heated flints and charred wood. It has been suggested that these two sites are the work of Homo heidelbergensis, the same potential fire-maker as Gesher Benot Ya'aqov. But there are many other hominid sites, both outdoors and in caves, scattered across Europe that show no evidence of fire, even though the winter temperatures there could not have been pleasant without it. Those hominids must have found other ways to cope, perhaps through other cultural adaptations like clothing and shelter, or simply by hugging a lot or migrating, being the Pleistocene equivalent of today's snowbirds.

Thus, the origins and spread of fire in our evolutionary history remain full of paradoxes. For example, how did Homo erectus evolve to have such a large brain and body without the increased energy and calories gained from cooking? We see these changes in the anatomy of our ancestors before we see evidence of fire in the archaeological record, although some researchers have suggested that we didn't need fire, just good cutting tools, to start the process of breaking down meat before consuming it. , allowing us to efficiently extract more calories. And how did this same species migrate from Africa to colder climates without the warmth of a campfire?

Dmanisi, in the Republic of Georgia, has a large number of fossils, but no signs of fire. It seems quite likely that the first fire made intentionally, by the hands of a hominid, came to life somewhere in Africa, probably at an open-air site like Koobi Fora. And maybe those hands belonged to a member of Homo erectus. As with many other early chapters in our history, we have much more research to do. But each of us lives with the legacy of that moment, captured in our own bodies. Our size, our musculature, and our big, intelligent brains are influences from that time (somewhere, by someone) when we first domesticated fire.

Thank you for watching this episode of Eons, produced in partnership with PBS Digital Studios and Complexly. Complexly produces more than a dozen channels, including Nature League, where host Brit Garner explores life on Earth and questions what we think we know about the natural world. For a taste of what to expect, we've linked his "Best of" playlist in the description below. Thank you for joining me in Konstantin Haase's studio today! And many thanks to our current eontologists, Jake Hart, Jon Ivy, John Davison Ng, and STEVE! YeahIf you want to join them and our other patrons in supporting what we do here, visit patreon.com/eons and make your contribution.