All language subtitles for BBC.How.to.Grow.a.Planet.3of3.The.Challenger.PDTV.x264.AC3.MVGroup.org.eng

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.

(CHUCKLES) 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.

(WHISPERS) 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.

Phew.

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.

BIRD SONG

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.

ENGINE STARTS

Like the engine, plants also need
a gas from the air to work,

in their case the carbon dioxide.

So, for plants...
ENGINE STARTS

...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.

ENGINE RUNNING
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.

(LAUGHS)

Whoo-hoo!

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.

Hm.

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.
There we go. Come and have a look.

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...

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.

(GIGGLES)

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!

(LAUGHS) First time you've put
your...

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.

OXYGEN HISSES
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.

OXYGEN HISSING

Grass ignites more easily
than other plants

and it's transformed into
a volatile gas.

This grass rises and burns
even hotter than the grass itself,

making it one of the fiercest
and fastest fires in nature.

OXYGEN HISSING

SIGHS AND SNORTS

OXYGEN HISSES
Ah.

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.

SNORTS
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.

Cos 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 recolonise.

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.

HORSE SNORTS
Whoa!

IAIN GRUNTS

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.

Yeah.

All right?

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

and that is in a period of about
one 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...

INSECT BUZZES

...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.

Ah, you...

Ooh. Oh.

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.

SNORTING AND GROWLING

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.

SNORTING AND GROWLING

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.

ELEPHANTS TRUMPETING
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.

SQUAWKING

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.

ELEPHANTS TRUMPET

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.

CHIMPS SCREECHING

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? Yeah. See, that's starting
to blur the boundaries. Yeah.

CHIMPS SCREECHING

The chimps of Fongoli
are the only ones in the world

that have been observed
using spears to hunt mammals.

CHIMPS SCREECHING

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.

BIRDSONG

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.

(LAUGHS) 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.

SCRAPES EARTH

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.

CHILDREN CHATTER

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.

LOW CHATTER

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...
Yeah.

...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.

Subtitles by Red Bee Media Ltd