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