Placeholder Image

字幕表 動画を再生する

  • Hi everybody, It's Hank. We've got new merch. I'm wearing it right now. It's this new

  • tee shirt! It's got an Eons pocket on it. It's comfy, it's nice thick fabric, it's

  • got a good design, it has a functional pocket! And now I have one of my very own.

  • If you want one too, you can get one at 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 likekeeps 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 casewe'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 theirBest ofplaylist 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!

Hi everybody, It's Hank. We've got new merch. I'm wearing it right now. It's this new

字幕と単語

動画の操作 ここで「動画」の調整と「字幕」の表示を設定することができます

B1 中級

When We Tamed Fire

  • 2 0
    joey joey に公開 2021 年 05 月 03 日
動画の中の単語