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00:00:08I spent most of my life trying to understand the forces that shaped our planet.
00:00:12And as a geologist, it always seemed to me that rocks were right at the heart of things.
00:00:22But now, I'm discovering it's not only volcanoes and colliding continents
00:00:27that have driven the Earth's greatest changes.
00:00:31Because at crucial moments in its history, another force has helped create the planet we live on.
00:00:39Plants.
00:00:41Just look at this seed.
00:00:43It's small, it's brown, it weighs hardly anything.
00:00:46It looks pretty ordinary.
00:00:48But actually nothing can be further from the truth because what it will become is truly extraordinary.
00:01:02These are giant sequoias.
00:01:05Some are over 3,000 years old.
00:01:10And sequoias are the largest single life form on Earth.
00:01:16All from a tiny seed.
00:01:20Yet even that pales into insignificance when compared to what the whole of the plant kingdom's done
00:01:25throughout the history of our planet.
00:01:29It's a whole new story about our Earth.
00:01:34Told through remarkable images.
00:01:37Captured for the very first time.
00:01:41And the latest scientific discoveries.
00:01:45I love this. This is just fantastic.
00:01:59This programme is about just one type of plant.
00:02:02The most underrated, but perhaps the most important of all.
00:02:08One that, by taking on and conquering the rest of the plant kingdom, shaped the face of the planet.
00:02:14And we're on to help create human civilisation.
00:02:18This is the story of the rise of that underdog.
00:02:38For hundreds of millions of years, throughout the time of the dinosaurs, forests ruled the land.
00:02:49It was so warm, trees extended over most of the Earth.
00:02:54Imagine the Arctic and Antarctic without ice, carpeted with forests.
00:03:05Welcome to the planet of the trees.
00:03:18Today, isolated remnants of those expansive forests still exist.
00:03:23And here in East Africa, it's one of the most impressive.
00:03:28The Kasagu Cloud Forest rises out of the dry plains of Kenya.
00:03:40Clocked in moisture, it's much the same as it was then.
00:03:47Oh, at last, look at that.
00:03:54But millions of years ago, a challenger to the all-dominant trees came onto the scene.
00:04:02And the best way to find it is to climb right down into the depths of the forest.
00:04:11It's never really elegant, this.
00:04:13This is when the adrenaline throw starts to come in.
00:04:18To be honest, I'm not quite sure after you get to, there's a little lip.
00:04:22It just seems to go straight down.
00:04:34This is the oldest forest in Africa up here.
00:04:38A relic, really, of the time when trees dominated the planet.
00:04:45So this really has a feeling of descending into that ancient lost world.
00:04:54A relic, really, of the place of the sky.
00:04:55And we're not.
00:05:05To be honest, the sun was just a little...
00:05:06Because the sun had a will be stretched...
00:05:14And the sun was just a little...
00:05:18That was a very beautiful cold.
00:05:19Back then, trees ruled, because wood gave them the strength to grow ever taller and
00:05:26to gorge on the sunlight all plants need.
00:05:36As you descend, you get a real sense of how trees bully and overshadow everything below.
00:05:50We've come about 10 metres just into the canopy, and I've nicked the cameraman's light
00:05:55mirror just to see what the light levels are doing, and already we've dropped by about
00:06:01a third.
00:06:12Now let's see how that light's doing.
00:06:17It's gone down by half.
00:06:19These huge trees here have stolen half the light.
00:06:29Down here, the trees are intimidating.
00:06:36But it's not complete gloom.
00:06:41Patches of sunlight do break through to the forest floor.
00:06:48And those shafts of precious light offered a chance for a new type of plant, one that
00:06:54would come to take on the trees.
00:07:01So how did scientists discover the identity of the Challenger?
00:07:07It's all thanks to a rather enchanting piece of research involving what's inside this little
00:07:14box.
00:07:15You'll never guess what it is.
00:07:19This is a piece of fossilised dinosaur poo.
00:07:24It stinks.
00:07:26Phew.
00:07:27It's from a titanosaur sauropod, which is kind of like a brontosaurus.
00:07:32My favourite dinosaur as a kid.
00:07:35It weighed about 100 tonnes, which makes me think that this is just a fragment of something
00:07:39the size of, I don't know really, something big anyway.
00:07:44Scientists love fossil poo.
00:07:46Coprolites we call it.
00:07:47Because they tell us about the diet of animals, and particularly in this case about the plants
00:07:52that were around when dinosaurs were here.
00:07:53And when scientists analysed this one a few years ago, they found it contained something
00:07:58really strange.
00:08:03Under the microscope, the scientists saw a fragment of a plant.
00:08:09It had a distinctive pattern, these figure of eight nodules.
00:08:14They turned out to be the defining feature of a family of plants they were astonished to see.
00:08:20The grasses.
00:08:25It was from 66 million years ago.
00:08:29Evidence for the earliest grass ever found, called matleitis.
00:08:39From its humble birth, grass would eventually become one of the most dominant forces on our planet.
00:08:55But its rise would be a David and Goliath battle with the trees.
00:09:09You can still find descendants of those early challengers today.
00:09:20Plants like this.
00:09:23And we think these are similar to what the first grasses must have looked like.
00:09:28You can just imagine them struggling away on the forest floor,
00:09:32just feeding off little scraps of light making it through the canopy.
00:09:38It's wonderful to think that dinosaurs the size of houses were trampling through forests like this,
00:09:44just grazing on little patches of grass.
00:09:53But the dinosaurs' days of grazing were about to end abruptly.
00:10:0765 million years ago, an asteroid 10 kilometres across killed them off.
00:10:23The grasses survived.
00:10:28But in turn, they would face their own crisis.
00:10:38What was coming had nothing to do with the plants and animals that lived on Earth.
00:10:42It was all to do with the atmosphere.
00:10:45And that was changing for the most surprising of reasons.
00:10:54Our air contains carbon dioxide.
00:10:56It's the gas that plants need to breathe to stay alive.
00:11:03But between 50 and 30 million years ago, this gas began to disappear.
00:11:10Threatening all plants.
00:11:21The crisis started with the creation of huge mountain ranges like the Himalayas.
00:11:35The biggest period of mountain building in Earth's history.
00:11:49The freshly exposed rock was washed away.
00:11:56Some of the minerals ended up in the sea.
00:12:07And here they suck the carbon dioxide gas out of the air, combining with it to form an entirely new
00:12:14type of rock.
00:12:21Limestone.
00:12:26I can show you that limestone's got carbon dioxide in it, because if I put a little bit of acid
00:12:31on it, it should fizz like mad.
00:12:40What this is doing is it's liberating carbon dioxide that had been in the ancient atmosphere.
00:12:45And it has now, for the last few million years, been locked away in this rock.
00:13:00By 30 million years ago, as the mountains had risen, the level of carbon dioxide fell.
00:13:10In fact, carbon dioxide levels dropped to a sixth of what they were beforehand, which is an enormous fall.
00:13:16And for the plant kingdom, it meant crisis.
00:13:24Without enough vital carbon dioxide, many plants, including the grasses, were struggling to survive.
00:13:53One way to reveal the impact that's had on plants is to look at a clever bit of human machinery.
00:14:02The car engine.
00:14:08Because what's under the bonnet shares surprising similarities with plants.
00:14:20The car engine relies on two things to work.
00:14:23It needs petrol, and it needs oxygen from the air.
00:14:26Inside the engine, these two are combined to release the energy to power the car.
00:14:33It's called combustion.
00:14:48Like the engine, plants also need a gas from the air to work.
00:14:51In their case, the carbon dioxide.
00:14:58So for plants, the collapse of carbon dioxide levels was similar to a car engine starved of oxygen.
00:15:09If I block the air intake, you can feel the engine stuttering away because it's struggling to get the oxygen
00:15:16that it needs to work.
00:15:22With less carbon dioxide in the atmosphere, plants also began to stutter.
00:15:29But the grasses were evolving a new and ingenious invention.
00:15:36Again, the engine provides a parallel.
00:15:41There's a piece of shiny machinery here that any petrol head will recognise.
00:15:45What that does is the opposite of my hand.
00:15:48And it forces more oxygen into the engine.
00:15:50It's called a turbocharger.
00:16:00More oxygen means that the petrol burns more fiercely.
00:16:04And that means more power.
00:16:06Power enough to do this.
00:16:27Evolution often comes up with our cleverest solutions during desperate times.
00:16:37and one group of plants the grasses turned this crisis into an opportunity
00:16:48grasses like this this is elephant grass which is one of the fastest growing plants in the
00:16:53world in three months right this stuff grows four meters that's that much every day this
00:17:02phenomenal growth rate was only possible because of a technology that evolved 30 million years ago
00:17:07a design so effective that if you were a mechanic you'd be blown away the new grasses came up with
00:17:22the equivalent of a turbocharger inside the leaves it's in the cells of the leaves that photosynthesis
00:17:35occurs where carbon dioxide is combined with water to make sugar but the new grasses created an add-on
00:17:46rings of specialist cells known as bundles
00:17:53it all acts as a miniature pump sucking in and concentrating vital carbon dioxide
00:18:08so although there was less carbon dioxide in the air the grasses had the edge over other plants
00:18:28you know when you study the planet you're so used to seeing the big events like
00:18:33ice sheets melting and volcanoes erupting but with the rise of turbocharged grasses you've got something
00:18:41that's the tiniest of events it's something almost invisible tucked away inside the the leaf of a plant
00:18:48it's what makes the story of plants just so fascinating
00:18:59the grasses had found a way to survive the crisis
00:19:09but forests still ruled the world
00:19:16the huge trees had also survived
00:19:24then the underdog unleashed a devastating new weapon
00:19:41eight million years ago
00:19:43by now the climate had altered
00:19:47much of the earth was drier than ever before
00:19:54it was the moment grasses had been waiting for
00:20:03the grasses had evolved unique properties that made them especially flammable
00:20:10when dry they became like a tinderbox all they needed was the spark
00:20:28today there's an ideal place to see what happened eight million years ago
00:20:40here in the national parks of South Africa rangers deliberately start huge fires to manage the land
00:20:53and for me it's the perfect opportunity to see how back then
00:20:57grasses exploited fire
00:21:01so so we're gonna get a chopper coming right down this line dropping incendiaries all the way along here
00:21:09chief fire starter is Chris Austin thanks for the three he coordinates the helicopter crew as they drop fire pellets
00:21:17onto the grass
00:21:19artificial lightning strikes
00:21:24what's going to happen is they just sit there they just open up ignite and then you just see them
00:21:29a rock
00:21:46and then over here we got ourselves another one
00:21:51so this line this whole line now just going to go up into a water plane another one there
00:21:57is this safe now here she's going to go up slope yeah she's going to go away from us and
00:22:02of course if the wind's pushing it it'll accelerate you can see that's now being pulled by the slope
00:22:07oh I can feel it it's just a wall of smoke and flame unbelievable
00:22:28the most aggressive fire that I've seen moved it more than three meters a second which is three meters a
00:22:32second that's phenomenal it's really quick you can't you can't outrun it the fires that kill people are grassland fires
00:22:37because they're so fast moving
00:22:42and that's not all grass burns in a special way a way that was devastating to its enemies
00:22:54I've kind of fallen into it
00:22:58to discover more about its properties I've volunteered to enter into the heart of the fire
00:23:06this stuff that's going in now is not kind of medical monitoring this is actually for monitoring the temperature of
00:23:11the fire
00:23:12it's a it's a thermocouple of wire that's going to go running down in this case down my leg
00:23:16I think it's probably the first time this has been done really
00:23:19the first time I've ever done this
00:23:20first time you put your hand down a man's trousers
00:23:24if you get stuck where that says virtually married
00:23:29once in the flames we hope to combine readings from the heat sensors on my suit
00:23:34with a thermal imaging camera to reveal the secrets of a grass fire
00:23:44the fire is picking up speed
00:23:49I can't believe I'm seeing this
00:23:50it's starting to come towards us
00:23:53this just seems like one of the daftest things I've done
00:24:10grass fires are very different from other fires
00:24:14the readings show that the hottest area of the fire
00:24:17the white parts on this image
00:24:19is not in the burning grass but a metre above it
00:24:24the temperature here is over 360 degrees
00:24:33grass ignites more easily than other plants
00:24:35and is transformed into a volatile gas
00:24:42this gas rises and burns even hotter than the grass itself
00:24:48making it one of the fiercest and fastest fires in nature
00:25:12oh I know this feels sounds really strange but it was actually quite a privilege to be in there
00:25:17you know normally if you're stuck in one of them
00:25:20you just don't come out
00:25:22it was great at one point the flames come up
00:25:25and I just looked down
00:25:27and it was just lapping against the mat
00:25:30you kind of feel sorry for the trees
00:25:40awes
00:25:41awes
00:25:41awes
00:25:49awesaw
00:26:02The next day, the fire still smoulders.
00:26:07It's so strange.
00:26:09Why did grasses evolve to encourage fires to take hold?
00:26:15Ripping through the landscape and destroying plant life.
00:26:19It seems suicidal.
00:26:24Grasses don't just encourage fires to start,
00:26:27they're also designed to survive them.
00:26:29In fact, they're the most fire-resistant plant on Earth.
00:26:33And you can see here, this all looks scotch.
00:26:36Look at it still.
00:26:38Look at that charcoal and smoke there.
00:26:40But the thing is, if you just peel this back,
00:26:42you quickly find it.
00:26:44Look at that.
00:26:45There's a lot of that still alive.
00:26:48In fact, the trick really,
00:26:50the solution to why grasses can survive,
00:26:53isn't on the surface, it's just below the surface.
00:26:57Because if you open up these stalks,
00:27:00you can see that right here is a little bud
00:27:04stuck under a kind of insulated, thick coating.
00:27:07It's kind of tucked away in its underground bunker.
00:27:10It's still alive.
00:27:13So you look around here and you just think everything's dead,
00:27:16and that tree, that tree certainly is.
00:27:18But the grass, the grass is just biding its time.
00:27:22It's very much alive.
00:27:26You know, this scene, this could easily be a scene
00:27:29from 8 million years ago,
00:27:32where the grasses just really quickly recover and recolonise.
00:27:37And the sneaky bedders,
00:27:38they do it much faster than trees.
00:27:41These are the trees.
00:27:43They do it much faster than trees.
00:28:11And they do it much faster than trees.
00:28:11In the wake of this onslaught, the forests started breaking up.
00:28:19The grasses were on a land grab,
00:28:23conquering the territory once held by the trees.
00:28:35The expanding grasses turned off into a flammable planet,
00:28:40a fireball world.
00:28:42It must have seen about a million, million trees burned
00:28:44and black ash filled the sky for hundreds of thousands of years.
00:28:49And for the trees, this was apocalypse.
00:29:02The world was ablaze.
00:29:06The Challenger had sparked a revolution
00:29:08that was changing the face of the planet.
00:29:23But the global rise of grasses wasn't just reshaping plant life.
00:29:28It was transforming the animal kingdom too.
00:29:34So how do we know this?
00:29:59So how do we know this?
00:30:01This is a forensic science.
00:30:03Part of the evidence has been discovered here in North America
00:30:06and it comes literally straight from the horse's mouth.
00:30:10Come on.
00:30:12Oh!
00:30:20When an animal eats a plant,
00:30:22the carbon of the plant is absorbed into its teeth.
00:30:28Studying the teeth tells you whether the herbivore has eaten
00:30:30the leaves of trees or the new grasses.
00:30:34Yeah.
00:30:37And the fossil teeth from millions of years ago
00:30:41tell a remarkable story.
00:30:47This is a result of the scientific analysis of tooth enamel
00:30:51from herbivores in North America.
00:30:53You can see down here, this is us going back in time
00:30:56in millions of years.
00:30:58Now the thing is, up to about 8 million years,
00:31:01to about here,
00:31:02you can see that herbivores are largely eating shrubs and trees.
00:31:05But then there's a really dramatic change
00:31:06about between 7 and 6 million years ago.
00:31:09And after that, they're eating grasses.
00:31:12And the thing is, this sudden switchover
00:31:14isn't confined to North America.
00:31:16Here's a graph for South America.
00:31:18And here's a graph for Africa.
00:31:20And also for Asia.
00:31:22And you put them together.
00:31:23Look at that.
00:31:25What these graphs tell is the same story.
00:31:28And that is, in a period of about 1 million years,
00:31:31a geological instant,
00:31:32the world's herbivores dramatically change their diet
00:31:35so that they're eating the new grasses.
00:31:45This discovery proves that by 6 million years ago,
00:31:50grasses were dominating the land.
00:31:58It was a domination that would have striking consequences
00:32:02for many animals.
00:32:18And it involved another piece of clever engineering from the grasses.
00:32:30Now this is it.
00:32:31This is the stuff I've been looking for.
00:32:34This is the sharp stuff.
00:32:36I'm pretty sure of it.
00:32:37Let's have a little lick.
00:32:42Ah, yum.
00:32:45Oh!
00:32:46That's something we've all done in the past.
00:32:49Cut ourselves on a blade of grass.
00:32:51Look at that.
00:32:53I'm bleeding.
00:32:55But have you ever wondered why that happens?
00:32:58It's actually all to do with something that coats the edge of the leaf.
00:33:10Grass extracts a mineral called silica from the soil.
00:33:17The silica is built into row upon row of tiny daggers along the leaf.
00:33:26It's a defence to discourage animals from eating it.
00:33:34Although tiny, these weapons led to one of the biggest extinctions of mammals in Earth's history.
00:33:43The world had been full of many different plant eaters, including the vast Balochotherium.
00:33:52These 20-tonne beasts were the largest mammals ever to exist.
00:33:58They fed off trees and shrubs.
00:34:01But as their food source disappeared, these animals died out.
00:34:14In North America alone, grasses led to the extinction of over half of all plant-eating mammals.
00:34:26But some herbivores thrived.
00:34:32It's all down to the teeth again.
00:34:35Who would have thought that gnashers could be so important?
00:34:38You could see how the survivors cope with this skull here.
00:34:41They developed harder teeth to bite through that silica-edged grass.
00:34:46And also, longer grinding teeth so that it didn't matter if they got worn down.
00:34:51The creatures adapted.
00:34:54And this is one of the results.
00:34:55The jaw of a modern-day horse.
00:34:58Like Tank here.
00:35:09By six million years ago, the triumph of grasses had caused the death of many types of animals.
00:35:16While creating vast herds of new ones.
00:35:20The more familiar plant-eaters we know today.
00:35:30But that's just the start.
00:35:33Because if you've got herbivores consuming silica-rich grasses, all that mineral has to go somewhere.
00:35:43As manure.
00:35:46The herds of herbivores were producing millions of tons of manure every day.
00:35:55It's washed away into rivers.
00:35:59Until finally it reached the ocean.
00:36:04And within it was all that silica.
00:36:13It's out in the oceans that things really began to take off.
00:36:18Because it's out here that there's creatures that are addicted to this silica.
00:36:26These creatures are microscopic.
00:36:30A few hundredths of a millimetre across.
00:36:34They're diatoms.
00:36:36A type of green algae.
00:36:41Diatoms are wonderfully delicate.
00:36:44Like some kind of alien architecture.
00:36:50But essential for the construction of their tiny skeletons is silica.
00:36:59Five million years ago they were feasting on huge amounts of silica from the grasses.
00:37:10For the diatoms it was like Christmas.
00:37:13Their numbers exploded.
00:37:23And diatoms are crucial because they form the foundation of the ocean's food chain.
00:37:29With more diatoms came huge shoals of anchovies and herring that eat them.
00:37:35This in turn attracts predators like seabirds and dolphins.
00:37:39And even bigger hunters.
00:37:48But it's from space you really appreciate their importance.
00:37:53They appear as vast green blooms.
00:37:58When they bloom they cover over a tenth of the oceans.
00:38:02They're green because like plants diatoms contain chlorophyll.
00:38:08And like plants they all release oxygen.
00:38:18Those photosynthesising diatoms which is about a quarter of the oxygen in the atmosphere.
00:38:24So I feel like every fourth breath you take on average has been exhaled by the diatoms.
00:38:30They really are the lungs of the ocean.
00:38:37It's remarkable what the humble grasses had achieved by five million years ago.
00:38:46A once forested planet was now dominated by open plains.
00:38:588,000 different species of grasses covering a quarter of all land.
00:39:06They'd selected which animals would live or die.
00:39:15And they'd fundamentally altered the oceans.
00:39:18Playing a crucial role in the make up of our atmosphere.
00:39:27Yet perhaps the most important impact of this remarkable plant was still to come.
00:39:40The impact on our story.
00:39:46Human beings.
00:39:47Human beings.
00:39:54And that's why I've come to the savannah of West Africa.
00:40:03I'm in Senegal to see a scientific forest.
00:40:06It's a discovery that's got profound implications for our understanding of our own past.
00:40:12Because it's here in Africa that our earliest ape ancestors emerged.
00:40:19Five million years ago, why did one group of apes leave the trees for the savannah?
00:40:25And develop so differently, eventually becoming human?
00:40:29Well, the chimpanzees here might provide some answers.
00:40:34Because unlike almost all other chimps in Africa, the ones here in Fongoli live on grasslands.
00:40:43Jill!
00:40:44Hi!
00:40:46Welcome.
00:40:47I'm Ian.
00:40:47It's what makes them so fascinating to anthropologist Jill Preetz.
00:40:51This is HQ, Chimpy HQ.
00:40:53Yeah, this is home base.
00:40:54So every day we take off wherever they're at.
00:41:02Jill has spent 10 years studying the Fongoli chimps.
00:41:12She's most interested in parallels between the unusual behaviours of these chimps and what might have happened during the evolution
00:41:20of human beings.
00:41:21It's settled around the water, all like that.
00:41:32I wasn't expecting that.
00:41:33I guess I was expecting them kind of swinging through the trees, but look at them.
00:41:37They're just ambling along and awful.
00:41:41Perfectly happy down here on the ground, walking through the grass.
00:41:46They look so human.
00:41:47I know it's obvious, really obvious thing to say, but they just look so human.
00:41:56The Fongoli chimps have other human attributes.
00:42:02They are proficient at using tools, like sticks for collecting termites.
00:42:10Many chimps in Africa catch termites this way, although these chimps do it more than any others.
00:42:22But what makes them really special is a hunting technique, one that is unique.
00:42:31Well, I think that probably the most exciting discovery we made was that they hunt with tools,
00:42:35which before we had thought only humans did.
00:42:37How is that?
00:42:39They'll fashion branches into sort of like a spear,
00:42:42and they'll use it to jab into these tree hollows where you have another kind of primate, a bush baby,
00:42:47and then they jab it into the hole.
00:42:53Jill's filmed this remarkable behaviour, the first time it's ever been recorded.
00:43:01It shows a chimp using a spear he's made to stab and kill a mammal, a bush baby.
00:43:14Yeah, that was something that, again, we sort of had used that to define humans.
00:43:18Really? Yeah.
00:43:19So that started to blow the boundary.
00:43:21Yeah.
00:43:34The chimps of Fungoli are the only ones in the world that have been observed using spears to hunt mammals.
00:43:44Jill believes they've had to come up with this behaviour to cope with the harsh and dry grasslands.
00:43:52It's a more hostile habitat than the forest, so the chimps here have to be smarter.
00:44:03And Jill has discovered a final extraordinary behaviour of these chimps.
00:44:14It also reveals more about how our ancient ancestors might have evolved as they moved out of the forests.
00:44:24This is a nice one, I think, from the wet season, so this is a grassland.
00:44:29I can see a group of them in there.
00:44:31Oh yeah, what, three or four of them.
00:44:33You can see them just above the grass, but watch what they'll need to do here.
00:44:46One of them just stood up.
00:44:47Yeah.
00:44:48I mean, he obviously has to do that to see over the grass.
00:44:51I want to see that again, yeah.
00:44:52Let me see that.
00:45:05Many scientists think this is perhaps a mirror of what happened as our own forebearers stood up on the grasslands
00:45:12for the first time.
00:45:15It allowed them to keep an eye out for predators and prey, and eventually to evolve walking.
00:45:26That's incredible, seeing chimps in the wild standing proud in the savannah grasslands, and looking incredibly comfortable as well.
00:45:32It's exciting to see it.
00:45:35It's the grasslands that's kind of driving and encouraging them to develop that way.
00:45:40Yeah.
00:45:40What, to be more resourceful, more resilient?
00:45:42I think so.
00:45:43They have to be creative and resilient.
00:45:46I've just got this weird feeling that I'm looking at a bit of video from four or five million years
00:45:50ago.
00:45:51Do you know what I mean?
00:45:52That could be the scene.
00:45:53Mm-hmm.
00:45:56Here at Fungoli, you can actually see what scientists think happened when grasses shaped our ancient ancestors,
00:46:03and encourage them to make those first upright steps onto the savannah.
00:46:09And it really brings home how our human journey began on the grasslands.
00:46:34Over the next five million years, these ape men continued to evolve in Africa.
00:46:43Until eventually, they became homo sapiens.
00:46:48And then, a hundred thousand years ago, these new people, for they really were people now, like you and me,
00:46:57began to migrate across the rest of the world.
00:47:03At this point in time, our ancestors were hunter-gatherers.
00:47:09They were living a tough life in small family groups, killing wild animals and collecting berries and roots to eat.
00:47:19But grasses hadn't finished with us.
00:47:23Because they'd trigger the greatest revolution in humankind's existence.
00:47:45It's not in Africa, but here in southern Turkey, that archaeologists believe they've discovered why that revolution happened.
00:47:56The place is called Gobekli Tepe.
00:48:02For me, this is one of the most exciting sites in modern archaeology.
00:48:07Because here at Gobekli Tepe are some of the oldest buildings in the world.
00:48:12They date to nearly three times the age of the first Egyptian pyramids.
00:48:15And there's a real mystery here.
00:48:18Who built this place?
00:48:20And more importantly, how could they have done it?
00:48:39This astonishing structure is 12,000 years old.
00:48:45It'd be buried and undiscovered until 1994.
00:48:53Hello.
00:48:54Hello, Jan.
00:48:56The archaeologist who unearthed it is Klaus Schmidt.
00:48:59It's great to be here.
00:49:00I welcome you to Enclosure Sea.
00:49:02Enclosure Sea.
00:49:03What a place. It's spectacular, isn't it?
00:49:06I mean, these are great.
00:49:08The big question is, who are they?
00:49:09One thing is very important.
00:49:11Never a face is depicted.
00:49:13They are always faceless.
00:49:14I saw you, as you came down, you were working on a very sophisticated one.
00:49:19Yeah, yeah, yeah.
00:49:19This looks amazing.
00:49:20What is it?
00:49:20This is a masterpiece of craftsmanship.
00:49:22It's one stone.
00:49:23It's one made from one stone.
00:49:24We have a flat relief of a boar, and we have this high relief of a leopard.
00:49:29This is an extremely complex society.
00:49:32Yes, yes.
00:49:33And this is a surprise.
00:49:34We didn't know this.
00:49:35We didn't expect this.
00:49:36What we are doing here, we add a chapter in world history, a chapter which we didn't know it exists
00:49:43before.
00:49:47To construct Gobekli Tepe with its 50-ton megaliths would have needed a huge army of well-organized workers.
00:50:00Yet 12,000 years ago was the Stone Age, a time when people were supposed to be hunter-gatherers living
00:50:08in small groups.
00:50:12How did they sustain the numbers essential to build such a vast temple?
00:50:26The answer lies a short distance away.
00:50:47Within sight of Gobekli Tepe are the Karajadag mountains.
00:50:52Here something happened at this time that would change our world forever.
00:51:04It was all to do with one particular type of grass.
00:51:11It's an ancient type of wheat which grew totally wild, just as it does today.
00:51:17It's called einkorn wheat.
00:51:2312,000 years ago was a time before farming.
00:51:28The people here would have been desperate for whatever nutrition they could gather.
00:51:37Yet collecting it presented a huge problem.
00:51:40Let me show you why.
00:51:43When the head of the wheat is ripe, then just the tiniest of touches and look what happens.
00:51:49It just scatters everywhere.
00:51:55And that's because the seed is attached to the plant so precariously.
00:52:00Imagine if you were trying to collect enough seed for a meal.
00:52:03I mean, I can hardly even see if we're there.
00:52:06There's one.
00:52:09It would drive you mad.
00:52:18Frankly, it's hard to believe anyone would bother.
00:52:22But everything was about to change, triggered by a crucial event.
00:52:30A tiny alteration in the genetic makeup of a wild wheat plant.
00:52:35Just one gene in just one single plant.
00:52:46That mutation has been traced back to here, just 30 kilometres from Gobekli Tepe.
00:52:56If you look closely, you can see the difference between the two types of wheat.
00:53:06In the original wild wheat,
00:53:08a special ridge of cells between the stalk and the seed breaks down as the plant ripens.
00:53:15And this allows the seed to fall away.
00:53:21But in the wheat with the genetic mutation, these cells remain as a solid band.
00:53:31It means the new wheat never lets go of its seeds.
00:53:38Now, under normal circumstances in the wild, that would doom the plant, because it just couldn't scatter the seeds.
00:53:43Look, you bang it and nothing happens.
00:53:45But it turns out that for one animal species, this trait was really beneficial.
00:53:52Us.
00:54:18Because the seed remained on the stalk after it had ripened,
00:54:21it meant that not only could the people who lived here collect more grain,
00:54:25they could also begin to farm it.
00:54:27In other words, they could take some of the spare seeds at the end of a season,
00:54:31put it back in the ground, and then harvest the new plants the following year.
00:54:35It was the dawn of domesticated wheat.
00:54:53And this wheat gave us bread.
00:54:58A fabulously concentrated form of energy.
00:55:01It could be carried, it could be divided up, it could be stored.
00:55:08And in turn, bread would lead to something even bigger.
00:55:19In order to build Gobekli Tepe, the Stone Age people turned their back on hunter-gathering.
00:55:29They became the first farmers.
00:55:3612,000 years ago, they began to sustain themselves with bread.
00:55:43Made from the grass we call wheat.
00:55:51Now they could feed the huge workforce required to construct such a vast and sophisticated temple.
00:56:01The mystery of Gobekli Tepe was solved.
00:56:05People had been hunter-gatherers, and now this site marks the end of their time,
00:56:10the end of their period, in the beginning of a new age.
00:56:16So Gobekli Tepe is part of that chain reaction?
00:56:19It's a cultural...
00:56:20The people being in Gobekli Tepe are the first people having bread also in their villages.
00:56:25Not only here, but also in their villages.
00:56:27That's incredible, isn't it?
00:56:28To think that these were the first people to taste bread.
00:56:32And the idea then, that it was bread that was the energy source essentially, the sustenance.
00:56:37Exactly, exactly. It's a turning point in world history.
00:56:59There's one last thing that I find intriguing.
00:57:03Our ancestors must have felt that they were the masters of this new crop.
00:57:07In the same way that we still feel today about farming, you know,
00:57:10we are in control of the plants that we grow and harvest.
00:57:14But think of it for a minute from the wheat's point of view.
00:57:17I mean, here's a plant that's done something really clever.
00:57:20It's attracted an animal that's prepared to sow it, to nurture it,
00:57:24to protect it from competitors and scavengers.
00:57:27It's also prepared to disperse its seed by hand, without the plant having to do a single thing.
00:57:36So it begs the question, who's using who?
00:57:53Human beings had now invented a way of harnessing the power of plants.
00:57:59And once invented, it could never be reversed.
00:58:02Because farming allowed us to come together in bigger and bigger groups.
00:58:07To build villages, towns and eventually cities.
00:58:24A world once dominated by forests and dinosaurs had given way to a world of our own making.
00:58:40I've always been fascinated by how our planet changes over time.
00:58:45Over the four and a half billion years of Earth history.
00:58:49And what's astounding is how important plants have been
00:58:52in changing that original lifeless rock into this vital and vibrant world that we live in today.
00:59:00Our home.
00:59:04Over the series we've seen how plants gave us the oxygen in the atmosphere.
00:59:12We've watched as the rise of flowers painted a drab world with brilliant colour.
00:59:19And we've discovered how plants shape the animal kingdom.
00:59:30And for us, the humble grasses play the most important role of all.
00:59:35They drove the rise of our ape-like ancestors.
00:59:38And ultimately, triggered the birth of civilisation.
00:59:44Plants made us.
00:59:45And the world we live in.
00:59:48Can we tell them, do we know the name of someone?
01:00:17The world we always believed.
01:00:17As the first one for himself is the first one, we've got together and the world to begin.
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