Original subtitles

I've come here to Southwestern France to the Pyrenees

and then deep into a mountain, more than half a kilometre

through a labyrinth of damp and dark caves,

into this enormous and remarkable cavern.

But I've come here to show you something very special.

Look at this.

No less than eight bison...

..drawn on this cave wall.

Absolutely beautiful.

But it's not just these bison. Have a look at this panel over here!

Here, we don't just see bison - we see primitive horses, tarpan.

And look there, a Pyrenean ibex.

Absolutely sensational.

Now, I've stood in art galleries all over the world looking at art,

but this is the oldest I've seen by far.

And possibly the most beautiful and most moving.

The drawings of these animals are so fresh,

so accurate, so beautifully made.

For me, this is about being human.

This is about our history.

The cave paintings are the culmination of a story

that began long before the first humans set foot on Earth...

..deep within our planet's past...

LOUD EXPLOSION

..when the world of the dinosaurs...

..was destroyed...

..making way for the rise of the mammals.

It's a tale of turmoil and upheaval,

of millions of years of climate swings

from one extreme to another.

Until, out of the chaos,

our species was born.

A species capable of creating art

on a cave wall in Southern France.

Now, we think that these were drawn around 13,000 years ago.

And that's significant because it constitutes a turning point,

not just for our species, but for the planet,

because we were going on to be a significantly powerful force,

capable of transforming and reshaping the Earth.

In the time since the cave paintings were done,

we've radically altered life on the planet...

..in ways our ancient ancestors could never have imagined.

And so we've reached a unique point in our planet's

4.5 billion year history, when an intelligent species,

with a clear understanding of the Earth,

is transforming it at an incredible speed.

And that species is, of course, us.

66 million years ago,

one form of life dominated the surface of the Earth.

DEEP GROWLING

Dinosaurs.

These magnificent creatures, amongst the largest that have ever lived

on Earth, had reigned supreme for around 150 million years.

They had evolved into many hundreds of species,

spread across every continent on the planet.

But all that was about to change.

What a wonderful place, packed full of life.

I've just been looking up into the forest here.

Tanagers, aracari, orioles -

a mass of species.

Now, of course, all of them are individually beautiful.

But, for me, it's when they form that complex web,

when they knit together to form a dynamic, harmonious,

functional ecosystem that things become even more beautiful.

But I've got to say, of course,

that none of these species were predestined.

They weren't "meant to be".

In fact, they were only here because of a single, freak, chance event.

An event of unimaginable violence

and astonishing destruction.

I'm talking, of course, about that day 66 million years ago

when the asteroid struck the Earth.

You know the one -

the one that's said to have wiped out the dinosaurs.

Now, there has been lots of debate about exactly

what killed the dinosaurs.

Since the 1980s,

scientists have believed the main culprit was an asteroid...

..from the far reaches of the solar system,

the size of Mount Everest...

..and on a collision course with Earth.

An extraordinary claim requires some extraordinary evidence

and, let's be clear, claiming that a six mile wide asteroid

crashed into the planet, unleashing the power

of a billion nuclear weapons is an extraordinary claim.

So where is the evidence?

Where is the smoking gun?

Well, I'm sat in it.

This is called a cenote.

It's a word that comes from one of the Mayan languages.

It literally means hole in the ground filled with water.

Now, take a look at this map of this part of Mexico,

the Yucatan Peninsula.

When I superimpose the cenotes, you see there's an enormous

number of them, the landscape is completely freckled.

But then look again in more detail.

You see this here?

There's an arc of these geological features running across here.

And if we complete the arc, turning it into a circle,

it has a diameter of 110 miles, which corresponds perfectly

with the inner rim of the crater made

when the asteroid struck our planet.

Now, the cenotes weren't formed at the time.

Over millions of years, that impact seems to have weakened

the rock here.

Water has leached through it, forming cave systems,

which have collapsed in some places, giving us this ring of cenotes.

HIGH PITCHED BIRD CALL

A devastating remnant of the asteroid strike...

..that brought the reign of the dinosaurs to a crashing end.

SHARP, LOUD BLAST

DEEP SCREECHING

LOUD RUMBLING

THUNDERING BOOM

The blast annihilates everything within its reach.

Earthquakes and tsunami tear across the planet.

And then it begins to rain.

Not water...

..but scorching hot rock...

DINOSAUR ROARS

..made from the asteroid and the bedrock it had struck.

ANGUISHED ROARS

Truly one of THE worst days in Earth's history.

DINOSAUR ROARS

But was this cataclysm enough to kill the dinosaurs

all over the planet?

For a species to become fully extinct,

every member of that species has to die and not be replaced,

and not just in a small area or even over a continent,

but over the entire world.

That's what extinction's really about, that's what it entails.

And generally, it's not a dramatic process, it's a slow burner.

Have a look at this.

In my bag here, I've got the skull...

..of an ornithomimid dinosaur -

one of a group of dinosaurs.

These creatures looked rather like giant ostrich

and they could run really fast.

But the key thing is that these ornithomimids can be found all over

the world in the fossil record.

So how did they become extinct?

Well, those that were unlucky enough to be living within the blast radius

of the asteroid, the answer's simple -

they just vaporised instantaneously.

LOUD, DEEP BLAST

And those living a little further away,

say within thousands of miles,

well, it's likely they were killed by the aftermath effects

of that strike.

Things like earthquakes, tsunamis,

the glass rain and the forest fires.

But what about the ornithomimids that were living, say,

on the other side of the world, as far away as possible

from the immediate carnage that was caused by that asteroid?

How did THEY die?

Well, something else was needed to cause the worldwide mass extinction.

DEEP RUMBLING EXPLOSIONS

To seek answers to this puzzle,

scientists have drilled deep into the asteroid crater.

The samples they've retrieved reveal important clues.

Such as the fine-grain debris churned up by the powerful tsunami.

As well as rocks like granite, melted by the incredible temperature

and pressure created by the impact.

But, crucially, one type of rock that's known to exist in this area

is missing from the place where the asteroid hit.

This is anhydrite.

Now, I know what you're thinking.

You're thinking this is a rather boring, grey rock.

But what's important is that it contains large amounts of sulphur,

and this is the final piece of our extinction jigsaw

because, when the asteroid struck, it vaporised this rock,

releasing no less than 300 billion tonnes of sulphur

into the atmosphere.

Today, there's virtually no trace of anhydrite in the seabed

within the crater...

..because it was all blasted into the air...

..merging with ash and dust to form a vast, grey cloud...

..sweeping across the entire planet.

With the cloud blocking out most of the sunlight,

temperatures plummet by around 20 degrees.

But the extreme cold isn't the only killer.

In the dark, twilight conditions,

plants struggle to photosynthesise and wither away.

And with virtually no plants to eat, the food chain collapses.

Many dinosaurs starve to death.

When it came to the dinosaurs, only a handful hung on to evolve

into the 10,000 or so species of birds that we have today.

Three quarters of all animal and plant species simply disappear.

This was one of the worst extinction events our planet has ever seen.

And yet, for our world to emerge,

there needed to be some survivors.

And most importantly from that branch of life that we belong to...

..the mammals.

What a place.

It's not representative of humanity's greatest attributes,

is it? It's a mess.

An apocalyptic landfill,

screaming of waste and consumption.

I suppose the one thing we can say is,

"Look, nature's always fighting back, isn't it?"

Look at the plants here and, out there, a whole host of wildfowl.

But let's stick with the mammals

because 66 million years ago they didn't all become extinct

and this is actually quite a good place to find a modern creature

that shares some real characteristics

with those early mammals,

and I happen to have a very friendly one inside my jacket.

What do you reckon?

I'll show you.

Yes! The rat.

Now, I'm rather partial to rats, I've got to say.

Just look at those whiskers.

Those lovely bright eyes.

But you might not be quite so enamoured

when I tell you that our ancient ancestors shared significant

similarities with creatures like this rat.

So what was it that they had that the dinosaurs didn't?

Well, many of the dinosaurs were quite specialised.

The herbivores required very particular species of plants to eat,

the carnivores very particular species of dinosaurs.

But most of the early mammals, they were generalists

and, equally importantly, they were omnivores.

They could eat plant material and flesh.

In fact, they could eat rotting plant material

and rotting flesh, and that was a real asset

when all of that starvation was going on during the impact winter.

So, I have to tell you, that, all of those millions of years ago,

animals like this represented hope.

And the world that we know today was resting on the shoulders

of creatures just like this rat.

I like that.

Yes, down to you!

It's thought the extreme cold conditions

lasted for more than ten years.

But eventually the sky cleared,

the sun shone down

and life could begin to make a recovery.

For more than 150 million years,

the mammals had been living in the shadows of the dinosaurs.

But now a new chapter could begin.

The age of mammals.

And it would be Earth's geological forces,

rather than an asteroid, that would change the course of life.

Deep within the North Atlantic Ocean,

thousands of hydrothermal vents begin to release

vast quantities of greenhouse gases,

including methane,

a gas around 25 times more potent than carbon dioxide.

THUNDERCLAP

This methane escapes into the atmosphere,

sending temperatures rocketing and triggering rapid climate change.

Violent storms ravage the planet with flash floods...

..and protracted droughts.

This dramatic global warming has profound implications

for the ancient mammals.

BIRDS TWITTER

Look.

Millions of bats.

Millions of mammals.

I can smell them, I can see them,

I can hear them and I can feel them.

There are so many bats out there whirling around

that it's actually generated a breeze,

which is very pleasant given how sweaty I am.

And it's ironic, isn't it, that, just when the planet

was going to see the rise of mammals,

which would ultimately give rise to species like our own,

it was also going through what can only be described as

rapid climate change?

And I can show you that here with this graph.

Now, the Earth was already a few degrees warmer at this time,

but look at this spike.

What this tells us is that, within the space of just

a few thousand years, the global average temperature rose

by five degrees Centigrade.

Incredible but sobering,

because climate scientists today go back through the geological record

and they use this spike as an analogue

for what might be happening to our atmosphere today.

And what really concerns them is how this happened.

What's scary is that it was precipitated by a series of events,

each triggering the next, triggering the next, triggering the next,

until it pushed the Earth past some serious tipping points.

And that is our nightmare.

Scientists believe that 56 million years ago

the hot conditions on Earth led to a very different world.

In the Arctic, where temperatures averaged around 23 degrees,

alligators could be found swimming under palm trees.

But despite this havoc, this hothouse Earth

seems to have had a silver lining.

Because, thanks to the warmer conditions,

subtropical forest or jungle has moved away from the equator

and expanded across much of North America, Europe and Asia.

And this rich, lush habitat would prove to be crucial

to the emergence of new species of mammal.

Ones more like us.

Wow!

Just look at that.

What a landscape.

This is the Calakmul Biosphere Reserve in Mexico

and, with its 2,700 square miles of forest,

it's one of the largest forest reserves in Mexico

and Latin America.

And aside from these Mayan ruins on which I'm standing

and a few other pockets of development, there's very little

human activity here, which means it's packed full of wildlife.

More than 400 species of birds -

toucans, trogons, parrots and tanagers.

And it's not just birds.

Hiding in the forest here are all sorts of other natural wonders -

ocelot, puma, monkeys,

enormous numbers of bats,

not to mention a host of reptiles and amphibians.

So, the question is, why is this place such a biodiversity hot spot?

Now, it's partly due to the vast diversity of plants

that we have here.

We think that in this area alone there are more than 1,500 species.

But it's not just that.

It's also down to something that we very much take for granted.

Have a look at this fossil that I've got here,

and in particular this tiny star-shaped structure.

That is a fossilised flower.

And we know from where this rock came from, in Utah in North America,

that that means that this flower bloomed

around 51 million years ago.

That is incredible.

Flowering plants are one of the great drivers of biodiversity.

And 56 million years ago, Earth's flourishing forests

were full of them.

For insects, flowers offered food in the form of nectar

to tempt them in to spread the plant's pollen for fertilisation.

But for other creatures, there was an even juicier prize.

Something they can eat that helps disperse

the plant's fertilised seeds.

One of the plant kingdom's great gifts to life.

Fruit.

First eaten by birds many tens of millions of years earlier...

..the fruits of the forest were to play a key role in the

evolution of a new type of mammal revealed in the fossil record.

Fruit offered both a reward and a challenge for mammals.

Now, the reward is that this is a perfectly formed capsule

packed full of calories.

The challenge is you've got to find it

and then you've got to be able to get it, and in a forest environment

like this that's actually quite difficult.

To find it, you've got to be able to see it

and then identify that it's ripe.

And once you've done so, you've got to be able to reach it,

which means that you've got to be able to climb all the way up there,

20, 30 metres or more.

So what creature could have possibly evolved

that could take advantage of this fabulous resource?

Maybe something like that.

And that is a Geoffroy's spider monkey.

Quite a rare animal these days.

But the key thing is that this animal shares significant

characteristics with those first true primates that arose

56 million years ago.

Look at them, they're beautiful, if not a little weird.

They're highly specialised, but look at the head.

Their eyes are forward-facing, like ours,

good for stereoscopic vision, good for spotting fruit.

They've got a relatively big brain, so they can remember where

they previously found that fruit, but the key thing are the limbs.

Look - long and strong.

And if you look very carefully there,

you can see their hands are like hooks.

And their fifth limb, that prehensile tail,

it's so strong they can hang from it

when they're eating fruits like this.

There's no denying that creatures like this are perfectly adapted

for the high life up there at the top of the forest.

Now, we're not entirely sure where the world's first true primates,

our ancestors, appeared because as soon as they evolved

they started spreading rapidly around the world,

between North America and Asia and on into Europe and Africa.

These primates, they were having the time of their lives,

and very rapidly they'd occupied no less than four

of the world's continents.

They were making it look easy and at this point

it seemed as if the Earth was destined to become

a planet of the apes.

But it wasn't to be.

After more than 20 million years of a hothouse Earth...

..the planet's climate dramatically cooled.

Scientists aren't entirely sure why it happened,

but the result was devastating.

Across the northern continents,

the cooler, drier conditions decimated the jungle.

Destroying much of the habitat of our ancient ancestors.

Sadly, we've been conducting our own perverse experiment

into what happens if you deforest the planet.

This is just one of a multitude of sites all over the world

that have been destroyed.

Until recently, this would have been tropical forest -

lush, green, filled with masses of mammals,

monkeys, tapirs, jaguar.

But they're all gone.

You see, habitat destruction like this

is probably THE leading force when it comes to extinction today,

and it was no different 34 million years ago.

When the tropical forest disappeared from the northern climes,

there were severe consequences.

The primates disappeared from North America completely

and all but disappeared from Europe.

So, on the face of it, this looks like a massive tragedy,

a severe setback for our ancient ancestors.

Or was it?

Because, if the story that we're really telling is the story of us,

Homo sapiens, humans, then it's not that simple.

The path of evolution that would lead from those ancient ancestors

to a creature like us, an upright, bipedal, big-brained ape

with opposing thumbs, was never going to be straight-forward.

For evolution to come up with something like the human species,

it would require a very precise and complex series of events,

and it would need to occur in a very specific environment,

where evolution could be nudged, if you like, towards the human species.

And it would be down to the Earth to create that very special place.

Although primates had mostly disappeared from the cold,

dry, northerly continents...

..in East Africa, where the jungle still remained,

they had survived.

And here, the planet's forces began to shape a new environment.

From deep within Earth, hot magma started to rise up,

lifting the ground and forming large cracks on the surface

as, over millions of years, the continent pulls apart.

It forms the spectacular East African Rift Valley.

Running some 4,000 miles through what will become

Ethiopia, Kenya, Tanzania and Mozambique.

And crucially, with its patchwork of forests and savannah,

it presents the primates with a dilemma.

ENGINE PUTTERS

So what was the dilemma?

Well, the first thing you have to appreciate is that the

Rift Valley in East Africa was no longer a single, great,

vast tract of tropical forest.

It had become fragmented into smaller pockets of forest,

quite analogous to this rather beautiful park that I'm sat in.

So these represent those pockets of forest and the paths in-between

the grassland that had formed between them.

Now, I want you to imagine that you are a highly arboreal,

tree swinging, fruit eating primate

and you've had your breakfast here at point A,

but your lunch is over there at point B.

How do you get between the two?

Because in the old days you could simply swing from tree to tree.

This was the dilemma facing those early primates.

The forest had fragmented, so had their food supply,

and they had no efficient way of getting from A to B.

So, what was the solution?

What did evolution come up with?

Well, some of those early primates decided to stick it out in the

shrinking forest and they evolved into chimpanzees and gorillas.

But another group, our ancient ancestors,

started to do something that we take for granted

but we have to learn to do.

What do you reckon?

I'll tell you - they started walking on two feet.

But our early ancestors didn't just walk out of the forest

never to return. They still spent a lot of time there,

probably even sleeping in the trees.

But walking gave them freedom

and with that freedom came the ability to hunt,

so they started eating meat and then they evolved bigger brains.

And that's why the Rift Valley in East Africa

is known as the Cradle of Humanity.

Now, initially, there were quite a number of human species.

But the key thing is that that is where our species,

Homo sapiens, evolved.

Now, the origins of our species are still shrouded in mystery.

But the East African Rift Valley is where scientists

have discovered many of the most important fossils...

..that tell the incredible story of human evolution...

..and the emergence of Homo sapiens

around 300,000 years ago.

With hindsight, we simply have to marvel at that remarkable

set of factors that came together to produce that highly unlikely

chain of events.

The seemingly impossible had happened.

After the best part of 66 million years,

after continents tearing themselves apart,

mountain ranges forming, the Earth's climate fluxing

and throwing between hot and cold,

a new force was about to be unleashed upon the Earth.

Humans had arrived, and there was no turning back.

Yet whilst our species had been evolving in the warmth of Africa...

..Earth's climate had continued to cool.

Scientists think that part of the reason may be down to Earth's

new mountain ranges -

the Himalayas, Andes and Rockies.

They had formed over tens of millions of years

as the result of plate tectonics pushing up the Earth's crust.

And through the process of weathering,

the exposed rock was reacting with carbon dioxide,

removing it from the air and causing temperatures to drop.

It meant that, as humans migrated out of Africa into Europe,

Asia and Australia, the extreme cold, dry conditions

prevented them from crossing into North America.

Earth was in the midst of an Ice Age.

And yet, despite the extreme challenges

we faced from the climate, it was around this time that humans

began to create something that had never existed on Earth before.

Art.

The oldest that we know of is this painting of a pig in Indonesia,

and it's been dated to around 45,000 years ago.

And closer to home in Europe,

we find cave paintings from more recent periods.

Here we are, back in this spectacular cave

with its remarkable drawings.

They are so, so beautiful that it's worth taking a moment

to think about what's going on here.

Well, around 13,000 years ago,

humans of the same species, exactly the same species as us,

were standing or crouching here in the flickering light of their lamps,

making these beautiful, beautiful drawings.

But what's it about?

Well, art is always about communication.

And this isn't just communicating to me about their intelligence

or their creativity - there's something else going on.

And it's interesting to note that in cave paintings of this age

humans are very rarely depicted.

It's always about nature.

And at this time, all of these species were wild animals.

We were still hunter gatherers, we were in tune with,

connected to and, critically, part of nature.

But for us to go on to become the global force that we've become,

things would need to change.

Our population would have to grow massively

and to achieve that we would need to control nature.

The extreme cold and dry conditions of the Ice Age

were not destined to last.

Subtle changes in Earth's orbit altered the amount of sunlight

reaching the planet's surface.

And together with increasing levels of carbon dioxide,

this pushed up temperatures...

..melting the ice.

For the first time, humans spread across North and South America.

We were now living on every continent except Antarctica.

And it was around 11,000 years ago,

in this warmer and more humid climate,

that humans did something simple but revolutionary.

They began to farm,

first growing crops, then raising livestock.

Within a few thousand years,

nearly all human societies on the planet were farming.

And slowly but surely,

producing food became an industrialised process

with an ever greater impact on Earth's ecosystems.

This is a vast field of soya beans,

stretching all the way to the horizon where the forest remains.

And many people think of this as a natural environment,

but it couldn't be further from natural if it tried.

This is the antithesis of biodiversity.

Now, imagine biodiversity is a rainbow

and the spectrum represents the full breadth of beautiful life

and when we're looking at this

we're looking at a tiny slice of one colour.

All of these regimented rows here are just one species.

This is a monoculture.

And it's not just that because the conditions that this crop

require to grow weren't here naturally.

This has been flattened, it's been drained, it's been fertilised.

It's been smothered in pesticides to keep nature out.

Now, forgive me, because for just a moment

I'm going to take on the difficult role of devil's advocate.

Imagine that we could put all of those environmental issues

to one side and take a fresh look at this.

We might consider it to be remarkable

because it's highly efficient crop production like this

which is producing enough food to cater

for our ever increasing human population.

You might say that our ability to invent technologies

and come up with a food production system that can feed

around eight billion people and keep many of them

out of starvation and famine is an incredible achievement.

But I can't forget those environmental issues,

certainly when I tell you that 40%

of the world's land surface that isn't frozen

is now given over to agriculture like this -

bland monocultures devoid of life.

And also, I can tell you that, of all the mammals alive at this point

on planet Earth today,

only 4% of them are wild animals.

96% are humans, their pets

or domestic farm animals.

And that, from my perspective, is terrifying.

But our takeover of the natural world

goes far beyond industrial agriculture.

Humans now have a greater effect in shaping the Earth's surface

than many natural processes.

And human-made materials, like concrete and plastic,

outweigh the combined biomass of all life on the planet.

Behind all of this is the staggering increase in the human population.

From one billion just a couple of hundred years ago...

..to eight billion today.

Welcome to the human planet.

Now, it is awesome but for me it's not wondrous

because, hand on heart, this is not my sort of environment.

I mean, there is some nature here,

but most of it is entirely artificial.

Most of what I can see is made of brick, concrete, steel and glass.

This is Mexico City,

and together with the 59 districts that radiate out to the horizon

it occupies 3,000 square miles,

and it's home to more than 21 million people.

And, staggeringly, it's not unique.

There are more than 30 other megacities across the world

with more than ten million people living in them.

But standing here looking at all of this you've got to ask,

"How can it possibly work?"

One thing that we have to acknowledge

is that agricultural revolution,

our ability to produce food with brutal efficiency.

That's what feeds all of us living in these megacities.

But there's another far more important ingredient,

something that was formed by the Earth and life

hundreds of millions of years ago,

something that we've drilled for and mined for.

I'm talking about coal, oil and gas -

the fossil fuels.

That's what's powered the technology that's allowed us

to build these megacities.

But it comes at a terrible cost

because, as we continue to burn those fossil fuels,

we are pumping CO2 into this atmosphere

at a rate that's comparable with some of those volcanic eruptions

that occurred millions of years ago.

And critically...

..we've started to radically transform our climate.

For most of Earth's 4.5 billion year history,

the most dramatic changes in climate...

..have been driven by asteroids...

LOUD BLAST

LOUD RUMBLING

..the powerful tectonic movement of the continents...

..and the catastrophic eruptions of volcanoes.

BOOMING EXPLOSION

Of course, as we've seen,

there have been moments when life too has had a profound impact.

Like the bacteria that colonised the oceans 2.4 billion years ago...

..and gave us the oxygen we breathe.

Or the swamp forests that sent temperatures spiralling downwards

and created the coal we now burn.

But today, the climate is changing at a faster rate...

..than at any time in the last 66 million years.

Now, I've seen so much of the natural world that I cherish

destroyed that it's difficult not to be pessimistic.

But, ironically, when I go searching for hope,

I don't turn to those planetary forces.

I turn to the power of humanity

because, for all of our flaws, all of our foolishness,

we are a truly remarkable species.

Adaptable, resourceful,

inventive, intelligent, creative.

And you might argue that our most significant turning points

were perhaps standing up on two legs and beginning to walk

or drawing those animals on the cave walls or inventing farming,

or even landing on the moon.

But I need to argue that these were just our dress rehearsals,

because in the very near future our species will need to reach

the zenith of its achievements and that all humanity will have to learn

to put our Earth first.

That unique, fragile, beautiful Earth

that for more than four billion years has been forming this stage

on which we now stand,

and it's waiting for our finest performance.

And if we don't pull it off,

then of course life on this planet will continue to prosper.

But there will be no encore for humanity.

If the Earth could talk, what would it tell us?

Well, the Open University imagine how it might answer

some of our questions.

To experience this interactive presentation,

go to the website on the screen

and follow the links to the Open University.

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