When We Tamed Fire

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DFTBA.com. There’s a link in the description! And we would appreciate it so you can show everybody all over the place how much you love this show Now, it’s time to talk about fire. In the early 1980s, archaeologists working
at a site in Kenya called Koobi Fora noticed some peculiar markings in the land 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 behind by
the campfires made by modern people in the area. Interestingly enough, this site had also turned
up the jawbone of a fossil hominin and evidence of stone tools having been made there, about
1.6 million years ago. So this got the researchers thinking: Was
it possible that these red patches were the 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 big questions
to answer. Like, could the hominins at this site have
actually made fire? Or did they happen to find some fire occurring naturally, like from
a lightning strike, and just used it for as long as they could? It’s likely that our ancestors started out
this way, taking advantage of fire as a fleeting natural phenomenon. But eventually they took it one step further–
scavenging a burning twig left behind by a wildfire, and using it to start their own
fires. The use of fire wouldn’t become truly visible
in the archaeological record until it became widespread – when fire started to be used
consistently, across many different sites. This could’ve been the moment in our history
that sparked evolutionary change, triggering an expansion into new environments. And when we learned how to actually make
fire when we wanted, it would forever change our relationship with the world around us. Now, the fact is, we don’t know exactly
when hominins harnessed the power of fire. And we’re not totally sure what species
among our ancestors was the first to master it — although there’s one candidate that
seems most likely. And it wasn’t us. Nevertheless, 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, in many ways, shaped by that time when we first tamed fire. The use of fire in human history is notoriously
difficult to study, because fire is ephemeral. It’s more difficult to see in the archaeological
record than, say, stone tools, because it’s a transient phenomenon that leaves little
evidence behind. Ashes can easily blow away in the wind or be washed away by water. But we know that the use of fire has had enormous
impacts on our bodies and our behavior. So some experts have looked at the gradual
changes in how hominins 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. You can actually think of cooking as a way
of starting the process of digestion, before you even put the food in your body. Which sounds
gross when I put it like that. It’s actually delicious But heat causes the large, complex molecules
in food to break up into smaller, simpler nutrients. So if you heat food with an external source
of energy, like fire, then you’re saving the energy that your body would have to put
into chewing and digesting the food if you had eaten it raw. Cooking also breaks down toxins in plants
and kills pathogens. And again, this saves your body from having to invest energy in
defending itself from poisons and disease. Together, these things make cooked foods much
more energetically efficient than uncooked foods, so you end up getting more calories
out of what you eat. And when you’re trying to survive, every calorie counts. But of course, the other advantage of fire
is that it like … keeps you warm. And so the use of fire likely helped our ancestors expand
their geographical range, migrating to places with different climates and opening up a whole
new world of ecological possibilities for our species. Now, there’s one hominin, besides us, that
fits both of these descriptions — a species that needed a lot of calories and that had
to live in lots of different environments — and that’s the earliest definitive member
of our genus, Homo erectus. Some anthropologists propose that Homo erectus
might have been able to cook food, based on its physical adaptations. Specifically, it had smaller teeth than its
predecessors, suggesting that it didn’t need to do the heavy-duty chewing that a diet
of raw food would require. But maybe more importantly, it also had many
of the traits that we know require a lot of calories — like a larger body size, more
muscle mass, and most importantly, a larger brain. And as for its ability to live in different
environments, Homo erectus is the first hominin known to have migrated out of Africa, eventually
spreading from what’s now the Republic of Georgia all the way to Southeast Asia. But here’s the problem: Homo erectus dates
back about 1.89 million years. But the earliest possible evidence of repeated,
regular cooking doesn’t show up until hundreds of thousands of years after its appearance. Likewise, Homo erectus began its excursions
out of Africa hundreds of thousands of years before the first definitive evidence of
widespread fire use. So how could fire have helped this species
develop a bigger body and brain, and help it migrate to other places? Well, as in many aspects of studying the distant
past, there are a lot of dots to connect. And in this case … we’re just missing
a lot of dots. So let’s look at what the evidence does
tell us — about the use of fire in general, and then cooking specifically. In the past few years, anthropologists have
gone back to that red-stained site in Koobi Fora, Kenya. And recent excavations have turned
up more definitive evidence of fire use than those red patches of earth found in the 1980s. Archaeologists have discovered shards of rock
with tell-tale signs of having been heated to high temperatures, as well as bits of burned
animal bone. And these bits of rock and bone seem to be
clustered in distinct patches. Which is important, because it suggests that the fires were small
and made intentionally, and not a natural wildfire, which would have burned across the
whole site. As for who made these fires, the burned rocks
and bones were all found in an area associated with artifacts that were likely made by Homo
erectus. But there aren’t any remains of those hominins
to be found there. Instead, the only hominin fossils from the site are of Paranthropus
boisei, a smaller brained species. The next earliest site with /widely-accepted/
evidence for fire is a site in South Africa that dates back 1 million years, in a place
called Wonderwerk Cave. There, archaeologists have found burned bones
and plants, as well as the larger and more complex stone tools, like hand axes, that
are known as Acheulean tools. These tools have often been associated with
Homo erectus. And some experts have speculated that, based on the date as well, Homo erectus
may be the hominin that built 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’s about 790,000
years old, burned seeds, wood, and flint have been found clustered together into what researchers
call phantom hearths – areas where fire might have been, but without a neat campfire ring
of stones. These clusters, and the fact that they occur
throughout time at the site, suggest that the hominins 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 might’ve been the last common
ancestor of humans and Neanderthals, is one candidate. So that’s what we know about when hominins
used, and maybe made, fires. But things get even more interesting when we try to figure
out which of our ancestors was the first to actually cook with it. Those bits of burned bone found at Koobi Fora
aren’t necessarily proof that hominins were regularly cooking meat 1.6 million years ago. Instead, as with fire use in general, anthropologists
are much more interested in when cooking became widespread enough to actually influence
our evolution. And evidence for regular cooking behavior
doesn’t appear until very recently, at least in geologic terms — about 350,000 to 400,000
years ago, in the region of the Eastern Mediterranean known as the Levant. Here, another cave site, called Qesem, preserves
a large, central hearth that was used repeatedly, and which one group of researchers thinks
was commonly used for roasting meat. Hominin teeth found in the cave resemble those
of both Homo sapiens and Neanderthals. But whoever was cooking at Qesem, they left behind
lots of butchered and burned bones. Finally, there’s still the question of when
and where fire was used outside of Africa. If fire was so helpful in fueling human migration,
then can we track its use around the world, to retrace our steps? Well, the first species that we have fossil
evidence of outside of Africa is — you guessed it! — Homo erectus, at a site called Dmanisi
in the Republic of Georgia, which dates back 1.8 million years. But there’s no evidence for fire at the
site, even though winter temperatures likely got just slightly above freezing. And again, as with cooking, we only see really
solid evidence for fire use in colder climates much, much later — at around 400,000 years
ago in Europe, at two different sites. At Beeches Pit in England, areas of burned
sediment with heated stone tools and burned bone have been interpreted as the remains
of hearths. And at Schöningen in Germany, the evidence is heated flints and charred
wood. These two sites have been suggested to be
the work of Homo heidelbergensis, the same potential fire-maker from Gesher Benot Ya’aqov. But there are a lot of other hominin sites,
both open-air and in caves, scattered across Europe that /don’t/ show evidence of fire,
even though winter temperatures there couldn’t have been comfortable without it. Those hominins must have found other ways
to cope – maybe through other cultural adaptations like clothes and shelter, or just cuddling a lot or by migrating
– being the Pleistocene equivalent of today’s snow birds. So the origins and spread of fire in our evolutionary
history remain full of paradoxes. Like, how did Homo erectus evolve to have
such a large brain and body without the bump in energy and calories gained by cooking? We see these changes in the anatomy of our
ancestors before we see evidence of fire in the archaeological record – though 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 out
of Africa and into colder climates without the warmth of a campfire? Dmanisi in the Republic
of Georgia has a wealth of fossils, but no signs of fire. It seems pretty likely that the first fire
made intentionally, by the hands of a hominin, sparked to life somewhere in Africa, probably
in an open-air site like Koobi Fora. And maybe those hands belonged to a member
of Homo erectus. As with many other early chapters of our history,
we have a lot 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, clever brains,
are all influences from that time — somewhere, by someone — when we first tamed fire. Thanks for watching this episode of Eons,
which is produced in partnership with PBS Digital Studios and Complexly. Complexly produces over 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 you can expect, we’ve
linked to their “Best of” playlist in the description below. Thanks for joining me today in the Konstantin
Haase studio! And extra big thanks to our current Eontologists, Jake Hart, Jon Ivy,
John Davison Ng and STEVE! If you’d like to join them and our other
patrons in supporting what we do here, then go to patreon.com/eons and make your pledge!

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