Original subtitles

Earth

As far as we know it's the only home to life in the universe.

Why? What is it that makes our planet so special?

The answers are hidden deep in the earth's past.

To find them we must travel back in time to see the first humans walk the earth.

To ride continents on a collision course, face killer dinosaurs.

Dive into oceans full of bizarre life-forms.

Feel the bitter chill of global ice ages

and experience the fury of cosmic missile attacks.

We must travel back in time until we reach the birth of the earth itself.

Then we can piece together our planets incredible story

and discover why all of this all of us are here.

Our journey starts almost 5 billion years ago.

But this can't be right.

There's no sign of our beautiful blue planet.

Just a newborn star, our sun surrounded by all this dust.

We've arrived too early before the earth has even formed.

Speed up time and we can see gravity pull the dust into tiny rocks.

It hardly seems possible but something as complex as a planet

is made from nothing more than dust and rocks.

Over millions of years gravity pulls these rocks together to form the earth.

One of at least a hundred planets circling the sun.

But 4.54 billion years ago our planet looks more like hell than home.

Up close the temperature is over 1'200 degrees Celsius.

There's no air just carbon dioxide, nitrogen and water vapor.

It's so hot, so toxic that if we got any closer

we'd be incinerated and suffocated in seconds.

The newborn planet is a boiling ball of liquid rock.

There are virtually no solid surfaces, just an endless ocean of lava.

A young planet called Theia is heading straight for us.

It's the size of Mars and it's traveling at nearly 15 kilometers a second.

20 times faster than a bullet.

The intruder's gravity is distorting the earth's surface.

The blast wave races out around the planet.

It's as though both young planets turn to liquid.

Trillions of tons of debris blast out into space.

But over the course of just a thousand years

gravity works its magic and turns the rubble into a ring of red-hot dust

and rock that circles the earth.

And now from this ring a ball forms over 3'000 kilometers wide.

We're watching the birth of our moon.

It's much closer than the moon we recognize.

Just 22'000 kilometers away.

Instead of about 400'000 kilometers.

The Sun rises over a cooling earth.

And sets just three hours after it rises.

The impact has set the earth spinning so fast

that an entire day lasts just six hours.

The days may pass quickly but the earth changes slowly.

To understand the making of our planet

we need to fast forward through millions of years.

A hail of meteors.

3.9 billion years ago and we're under attack

from debris leftover from the solar system's formation.

Look at these strange crystals inside the meteors.

They look like grains of salt.

The same salt you pour on your french fries.

And inside these minute droplets of water.

It seems these deadly missiles could contain

the vital ingredient for life on Earth.

There's only a small amount of water inside each meteorite.

But as they bombard the earth for over 20 million years

pools of water grow.

The water collects on solid ground

The earth's core remains molten but its surface is cool

to around 70 or 80 degrees.

Just enough to form a crust.

In the future we could swallow this water when we take a drink.

Every sip, every puddle, every drop of water in every ocean

is billions of years old.

And it may have traveled millions of kilometers to reach us

carried inside a meteor.

The earth looks more familiar, but this is still a dangerous place.

This wind is as fast, perhaps faster than the most destructive hurricane.

It's a mega storm ripped up by the planets rapid rotation.

The moon is so close to Earth that its gravity is overwhelming.

It creates huge tides that race across the planet's surface.

But over time the moon moves away.

The waves calm and the planet spins slower.

700 million years after the planet's birth life-giving water covers its surface.

But not just water.

There's something else down there.

Tiny islands they seem to have appeared from nowhere.

Until

molten rock bursts through the earth's crust and rises up through the ocean.

Over time the lava cools and forms a volcanic island.

This is how these islands formed.

In the future they will join together to form the first continents.

The infant earth has water and land.

It's beginning to look like the planet we call home.

But the atmosphere is toxic and the temperature is scorching.

Nothing could live here.

Meteors.

They've been raining down since the planets formation.

But now 3.8 billion years ago the assault has entered a violent new phase.

Something has disturbed the orbits of these meteorites.

They already brought water to the planet but they're carrying something else too.

As the meteorites dissolve they release their minerals

and transport carbon and primitive proteins, amino acids

from outer space to the bottom of the ocean.

It's dark, the sun's rays can't reach beyond 300 meters .

And it's close to freezing.

This must be a mirage.

A city of underwater chimneys.

It's not smoke, it's some kind of hot liquid.

Seawater has seeped down into the earth through cracks in the crust.

Getting hotter, collecting minerals and gases on the way.

It's this potent mixture that's spewing back out into the ocean,

building these towers.

Add to this all those minerals and chemicals from the meteorites

and the water has become a chemical soup.

It's impossible to know how or when,

but somehow these chemicals have come together to create life .

The water is now full of microscopic organisms.

These single-celled bacteria are the earliest forms of life on Earth.

This is a defining moment in the making of the planet.

Microscopic life is on the way.

To find more complex life we need to travel forwards through time

to 3.5 billion years ago and a shallow ocean.

These look like rocks or even plants.

They seem to grow out of the seabed.

Each is a mountain of living bacteria.

A colony called a stromatolite.

As if by magic these bacteria turns sunlight into food.

This process called photosynthesis uses the power of sunlight

to transform carbon dioxide and water into glucose,

a simple form of sugar and similar to the stuff we put in our coffee.

And this magical transformation releases a byproduct, a gas called oxygen.

Underwater the stromatolites slowly fill the oceans with oxygen.

The oxygen turns traces of iron in the water into rust.

This falls to the ocean floor to form deposits of iron rich rock.

One day we'll use this mineral to build bridges, ships and skyscrapers.

Above the waves the oxygen transforms the atmosphere.

These stromatolites are creating the single most important element

for life on Earth.

Without them virtually every living thing wouldn't exist.

When we take our next breath we're doing it

thanks to these colonies of ancient bacteria.

Over the next two billion years oxygen levels continue to rise.

And as the planet's spin slows the days get longer.

Now they last at least 16 hours.

We're discovering it takes a long time to make a planet.

1.5 billion years ago, three billion years

after the planets birth and there's no complex life.

No plants, no dinosaurs, no humans.

But the earth has something that no other planet has.

A force with the power to change everything.

Our planet, a beautiful blue ball dotted with volcanic islands

One and a half billion years ago it's home to primitive life.

Over millions of years we can see something is rearranging the islands.

Hidden beneath the ocean the earth's crust has broken into vast plates.

Deeper still the Earth's core is at work.

It's hotter than the surface of the Sun.

So hot it generates movement in the rock beneath the crust.

These movements push and pull the plates around the globe

and carry the oceans and the islands with them.

Millions of years raced by.

Seeing it like this our planet seems active, changing, alive.

Over 400 million years a vast new super- continent takes shape called Rodinia.

In the shallow waters around Rodinia stromatolites have been working

their magic for over two billion years.

Pumping oxygen into the atmosphere.

The temperature is 30 degrees Celsius and the days are 18 hours long.

But this looks more like Mars than Earth.

To find life here we need to move on through time.

The state of Washington.

715 million years ago some force

from deep inside the planet itself is ripping the crust to pieces.

It's as though the world is tearing apart.

And there's only one force powerful enough to do this.

Heat.

It escapes from the earth's molten core

stretching and weakening the crust.

Centimeter by centimeter, year by year

the great supercontinent is splitting in two.

The intense geological activity has spawned a mass of volcanoes.

These pump carbon dioxide into the atmosphere.

There's smoke and gas everywhere.

All that carbon dioxide mixes with water to make acid rain.

The rocks absorb the acid rain including its carbon dioxide.

And there are a lot of rocks on the earth right now.

Exposed when the continent tore apart.

So many that vast quantities of carbon dioxide are absorbed

out of the atmosphere and locked up in the earth's rocks.

There's not enough carbon dioxide in the atmosphere to trap

the sun's heat around the planet.

In just a few thousand years the temperature plummets

to around minus 50 degrees.

This frozen wasteland is Southern Australia.

650 million years ago.

It's the start of what some scientists call Snowball Earth.

A period they believe to be the longest, coldest ice age

ever to grip the planet.

A vast wall of ice, thousands of meters high.

The ice is unstoppable.

The more ice there is, the more sunlight it reflects away

from the planet and the faster the ice spreads.

And there's a second ice sheet just as high.

The two sheets spread away from the poles towards each other

to meet at the equator.

Now an ice sheet up to three kilometers thick

untunes the entire planet.

First the planet was a molten ball of fire

now it's a frozen ball of ice.

Virtually all the sun's light and warmth reflects back into space.

But it can't last forever.

Something must release the earth from this frozen prison

and when it does who knows

whether life will have survived beneath the ice.

The surface is frozen but the core is still hotter

than the sun's surface.

Volcanoes have been erupting since the world began to freeze.

But up until now even their heat and power

made no impact on the ice.

Volcanoes pump out billions of tons of carbon dioxide

before the big freeze the Earth's rocks absorb most of the co2

But now with the rocks smothered in ice

there's nothing to absorb the gas so it fills the atmosphere.

Like a blanket it traps the sun's warmth around the planet.

Temperatures rise until now after 15 million years the ice begins to melt.

It's thought that during Snowball Earth the ice pushed the crust down.

Now as it melts the crust bounces up.

This creates fissures and weak spots and more and more volcanoes.

These volcanoes release more carbon dioxide

and push the temperature up even higher.

The melt gathers momentum.

Oxygen levels rocket.

Through a series of chemical reactions the ice has created oxygen.

While the planet was frozen the sun's ultraviolet rays reacted

with water molecules in the ice to produce a chemical rich in oxygen.

Hydrogen peroxide the same chemical that bleaches head.

Now as the ice melts the hydrogen peroxide breaks down and releases

massive amounts of oxygen.

The earth is waking up and it's a very different place.

Now 600 million years ago the atmosphere is warmer, it feels like a summers day

and the days are about 22 hours long.

Add all this water and it's the perfect recipe for life.

Before Snowball Earth primitive bacteria had emerged in the oceans

but surely they couldn't have survived an ice age

75 times longer than the entire span of human history.

If something has survived then our best chance of finding it

is where we last saw life, in the ocean.

Now 540 million years ago in an ocean full of oxygen

those primitive bacteria have evolved.

A handful must have clung on through the big freeze

there are plants everywhere and something else.

It looks like some kind of armored slug.

It's called Wiwaxia.

It's one of a new generation of complex multi-celled organisms.

We're entering one of the most dynamic periods in the earth story.

The Cambrian explosion.

Increased oxygen levels allow creatures to grow larger and develop bony skeletons.

There are worms, sponges and these.

They're trilobites distant relatives of insects, lobsters even scorpions.

Life in the oceans is blossoming.

From microscopic bacteria to a monster like this.

This is an Anomalocaris.

It's about 60 centimeters long.

Look at its large eyes, its razor-sharp teeth and grasping limbs.

All Anomalocaris has to do is take its pick.

The trilobite caught right itself , its soft belly is exposed.

these are pic aiya they're just five or

so centimetres long but they've got what

may be the first ever spine over

millions of years this simple structure

will evolve into the spine that keeps us

standing erect and creatures are

beginning to take on familiar forms

beneath the waves there are already tens

of thousands of plant and animal species

the advance of life seems unstoppable

we're looking to life on land

460 million years ago and the plates

have moved again below lies a new

continent Gondwana

it's a warm 30 degrees Celsius oxygen

levels are close to those in which we

live the land should be covered with

plants crawling with creatures

but there's not much here beside a few

patches of algae

there's only one explanation

the son

it blasts the surface with deadly

radiation

the complex life we've seen in the ocean

doesn't stand a chance on land

but 50 kilometers are where the rays

enter the Earth's atmosphere

something strange is happening when

oxygen meets the sun's radiation the

oxygen turns into another kind of gas

called ozone this gas forms a blanket

around the planet this ozone layer

absorbs the lethal radiation

over 120 million years the ozone layer

gets thicker and stops more and more

radiation from reaching the Earth's

surface without this layer life on land

simply wouldn't exist

now shielded from radiation life

blossoms

those small mossy lumps are the first

land plants and they're pumping out even

more oxygen levels saw

375 million years ago

there's something down there in the

water it's moving swimming

it's a strange fish called a Tiktaalik

you

it's neck allows it to raise itself up

it uses its fins as if their legs

and moves out of the water where Clarke

life is exploding

over 15 million years these creatures

call tetrapods evolve they grow stronger

limbs and spend more time out of the

water until 360 million years ago they

make the land their home

it's from a creature like this that all

four-legged vertebrates will evolve

dinosaurs birds mammals and eventually

you need

we've come a long way from a lump of

burning rock and dust to a Bluegreen

planet bursting with life

there are still no humans but there are

fish plants and this

it's a dragonfly a dragonfly the size of

an eagle

this giant is called meganula

what were once legs have evolved into

wings extending the dragonflies hunting

territory over a vast area

there are millipedes spiders all sorts

of bugs down there

these creatures called arthropods were

among the very first to set foot on land

they've already been around for hundreds

of millions of years they look almost

identical to the bugs that invade our

homes today except for one big

difference like mega Noura they're

monsters

we've stumbled into a lost world of

giants where millipedes are two meters

long and scorpions the size of wolves

all the oxygen in the atmosphere allows

their respiratory systems to be more

efficient and frees up space for their

bodies to grow

a lizard-like creature called anonymous

the creatures we've seen so far laid

their eggs in the water

but these eggs contain all the water and

nutrients the developing Heil anima

Sneed's the babies are growing in their

own self-contained pond

the egg is a major evolutionary

breakthrough

now animals can leave the water behind

and conquer the land

this baby hi Lana mas will lead the

advance

it's a new kind of creature a reptile

inevitably with life comes death there's

so much dead plant matter it builds up

and decays into dense soggy layers

over hundreds of millions of years rocks

will cover these layers heat from the

Earth's core and pressure from the

overlying rocks will transform the

layers of dead plants into seams of coal

each lump of coal we burn today to warm

our homes and fire our power stations is

made of flowers that died 300 million

years ago

amidst the decay hidden from sight life

is stirring

soon seeds will germinate plants will

grow and this wasteland will live again

life seems to have conquered the planet

a herd of creatures graze the Siberian

Plains they're not dinosaurs

they won't set foot on earth for at

least another 20 million years but

they're big evolution has taken a huge

leap forwards the small lizards we saw

earlier and now giant reptiles

these are scooter soars the distant

relatives of turtles they're plant

eaters and if the plant eaters look this

tough the karlik wars must be seriously

mean it's a Gorgon awesome

a perfectly engineered prehistoric

killing machine

the gorgonopsids saber teeth have

wounded the scooter sir

the predator is watching as its prey

grows weak from blood loss until hold on

it's backing off something strange is

happening

the ground is getting hot

you

there must be enormous pressure beneath

the surface

there's larvae but this isn't one single

volcano the entire landscape is erupting

it's a flood basalt eruption a massive

plume of mantle is rising up from deep

inside the earth pushing molten rock out

through fissures in the Earth's crust

the lush paradise is now a lifeless hell

the SCOOTER sores and the gorgonopsids a

debt they're the first casualties in the

greatest mass extinction the world has

ever seen the Permian extinction

on the other side of the continent of

Gondwana it's as if nothing happened

snow

but the temperature is about 20 degrees

Celsius

it's not snow it's ash fallout from the

eruption some 16,000 kilometers away

the ash burns suffocates and kills

animals around the world

the atmosphere is full of sulfur dioxide

from the eruptions and it rains the gas

turns to sulfuric acid and burns

everything it falls on

at first it seemed like this was a local

disaster but now it's gone global

the Siberian eruptions increase the

Earth's carbon dioxide levels

the atmosphere gets hotter

water evaporates

the vegetation dies

we saw life had finally found a foothold

now it looks like we were wrong

there are no signs of life on land but

in the oceans

this can't be right the oceans are

turning pink

and the plants the trilobites

the Predators everything's gone

everything except for this pink algae

the new hotter atmosphere must have

heated the oceans and stripped them of

oxygen

now nothing except algae can survive in

the stagnant water

the Siberian eruptions are transforming

the entire planet

nothing not even the deepest ocean floor

is beyond their reach

look bubbles

but it's not oxygen it's methane

escaping from vast pockets of methane

gas beneath the seabed methane is a

greenhouse gas at least 20 times

deadlier than carbon dioxide

until now the gas has been frozen but as

the sea temperature rises the gas begins

to melt

released into the atmosphere this

powerful gas pushes up temperatures even

further

up to almost 40 degrees six degrees

hotter than before the Siberian

eruptions

now even the creatures that have made it

this far are tuned

it's 500,000 years since the eruptions

first began and all this time for half a

million years the lava has been pouring

out by now it covers an area the size of

the United States with a layer of molten

rock nearly six kilometers deep 250

million years ago we're back where we

started on a lifeless planet

almost it's 50 million years since

virtually all life on Earth was wiped

out and the planet has been transformed

it's now 200 million years ago and

there's just one supercontinent called

Pangea stretching from pole to pole

after the trauma of the mass extinction

the planet is healing

temperatures are stabilizing the acid

rain is neutralizing and vegetation

returning

and with 95% of all life on Earth wiped

out the field is open for a new species

to emerge one that will dominate the

planet like no other before or since

the dinosaurs

these dinosaurs are called Amazon's like

all dinosaurs they've evolved from the

handful of reptiles that survived the

Permian extinction

at four and a half meters tall their

size makes them slow and vulnerable I

don't offer Soros two of them they're

small and fast

you

the Allosaurus is too big a meal for one

Dilophosaurus but not for too

the dinosaurs have repopulated the earth

but no species contain this Restless

volatile planet

the Earth's crust is thinning here it's

releasing lava shaking with earthquakes

as though it's been stretched by some

unseen force

and the same thing is happening all the

way down what will be North America's

eastern seaboard

the Earth's plates are on the move again

190 million years ago the great

supercontinent of Pangaea breaks up

a vast slab of land has broken away you

creates a chasm and this fills with a

new ocean called the Texas over what

will one day be the Middle East

currents are pushing nutrients up into

the coastal waters running along what

will be Saudi Arabia Iraq and Iran

and the nutrients attract fish in their

Millions

and with so much life also comes death

dead fish and plankton carpet the ocean

floor

over the next 10 million years layers of

rock will bury and heat the dead

creatures ancient fish and plankton will

become oil

every litre of fuel in our cars every

piece of plastic on the planet the paint

on our walls the carpet under our feet

even the soap you wash with almost all

originated in this way

180 million years ago and further west

the North American plate is still moving

away from the European and Asian plate

it happens slowly at about two and a

half centimeters each year the same

speed as our fingernails grow

but hit fast-forward and a new ocean

forms right beneath us and new

continents

Montreal moves away from Marrakesh New

York from West Africa

the world as we know it is taking shape

the chasm between the two continents

fills to create a vast ocean

the Atlantic

and they're in the middle a volcano

we've seen plates move before we know

it's caused by currents deep beneath the

earth's crust this process is happening

down there right now

the entire seafloor has been torn in two

and pushed up into a ridge of mountains

and volcanoes it's growing higher than

the Himalayas and longer than the

Rockies

the waters hot here molten lava is

forcing its way out from deep inside the

earth

as the lava cools it's creating a new

range of volcanic mountains and new

ocean floor

this is what's pushing the plates and

Pangaea apart

and rearranging our world

it's this geological activity that makes

the earth Restless creative unique

and every time the planet reinvents

itself the things that live on it must

adapt and evolve

things like these there akia sores

they're reptile ancestors lived on land

but as the planet changed so did they

they grew fins and moved into the newly

formed Atlantic Ocean

this one is six meters long and fast it

travels at about forty kilometres an

hour

it's the oceans fastest creature the

most efficient predator and it's ruled

the Earth's oceans for 50 million years

but now there's a new contender for the

crown

appliance or

longer than a bus as heavy as a truck

its jaws are immense over eight times

more powerful than a great white sharks

and its teeth a 30 centimeters long

the earth and the creatures that live on

it has changed beyond recognition

this was once solid ground now it's the

Atlantic Ocean

it was on this very spot that we stood

and watched

Amazon's graze and I'll office or stalk

their prey the dinosaurs world may be

different but there is dominant as ever

they appear invincible

it's a shrew-like mammal and it's

evolved from the small number of mammals

that survived the mass extinction 185

million years ago it's also prey for the

dinosaurs this is why most mammals live

in the trees or underground and venture

out at night mammals are no threat to

the dinosaurs

nothing on earth can challenge their

dominance

nothing on earth

it's a lump of space rock a large one

this asteroid is about ten kilometers

across bigger than Mount Everest

and it's traveling at over 70,000

kilometers an hour straight towards the

earth

it's heading for the Gulf of Mexico just

off the Yucatan Peninsula

it travels so fast blink and we'd miss

the impact unless we slow down time it's

a split second that will change the

world forever

at the moment of impact the asteroids

back edge is still nearly 11,000 meters

the same height as a commercial aircraft

flies

the asteroid strikes with such immense

force it destroys everything it hits

even the asteroid itself instantly

vaporizes

the impact unleashes the energy of

millions of nuclear weapons

nowhere is safe not even way up here

some of these boulders are as big as

entire city blocks

the blastwave races out from the impact

zone like shrapnel from an exploding

bomb

I mean it's after impact thousands of

kilometers from where the asteroid

struck the earth is under attack from

every direction

boulders rained down

earthquakes shake the ground

and tsunamis batter the coasts

but the onslaught has only just begun

the plume of molten rock and dust

spreads out and engulfs the planet

the entire sky is acting like a giant

sunlit

the Earth's surface heats up to 275

degrees vegetation begins to

spontaneously ignite

even months after the impact smoke and

ash still block out the sun's rays

with less sunlight plants died and the

animals that eat them starve

against this onslaught it's hard to see

how anything can survive the dinosaurs

165 million year reign is over

but the dinosaurs demise is an

opportunity for another species mammals

by living underground they've avoided

the heat in the fires and by eating

anything and everything they thrive

while more selective eaters die

these are the unlikely inheritors of the

dinosaurs crown

and as one story ends another begins

with the dinosaurs out of the way this

could be our ancestors chance the

dinosaurs are long dead the planet is

peaceful

in this new world our mammal ancestors

are evolving

this lake 47 million years ago in what

will one day be Germany should be the

perfect place to spot them

this isn't like the mammals we saw

earlier its eyes and brain are bigger

this is Darwinian massive a or EDA she

looks nothing like us but fossil

evidence from our own time tells us

these creatures could evolve into

monkeys apes and eventually humans

we're looking back through 47 million

years of evolution to what may be one of

our earliest known ancestors

the lake sits on a volcanic crater it

belches out noxious gas

now the lake that killed her will

preserve her in its oxygen-depleted

deaths

one day when the water has gone an EDA

is fossilized in stone we will discover

her and recognize in this primitive

primate what could be the very beginning

of our own story the story of human life

we're closer to understanding how

everything we've seen from ocean

bacteria through walking fish and

subterranean rodents leads to us and to

understanding how our planet was made

47 million years ago and the atmosphere

is much like our own

the temperature is 24 degrees Celsius

and a day lasts just under 24 hours the

earth we're looking at now is almost

identical to the planet we call home

almost

the Earth's plates have been on the move

again with the continents on their backs

India moves north towards Asia

the Indian and Asian plates are locked

in a titanic struggle

you

neither plate is winning both plates

begin to buckle

what was once oh she and floor contorts

upwards along a two and a half thousand

kilometer line

a vast mountain range rises up

1,500 meters 4,500 meters

now over 8,000 meters

you

these are the Himalayas

and there it is the highest mountain of

all

Mount Everest

when the snow on the peaks melts it

feeds great rivers the Ganges Indus

Yangtze and yellow rivers

the Himalayas are like a vast water

tower one day their rivers will supply

water for almost half the world's

population

20 million years ago this is our planet

with every continent every ocean just as

we know it

except there's one thing missing us the

human race

for humans to evolve something somewhere

down there has to change

along Africa's East Coast between the

plates that make up the Earth's crust a

great rift opens up

the rift stretches nearly 6,000

kilometers

along its edge mountains grow

there

it looks like a name not a human it

might stay in these trees forever but

its world is changing

the growing mountains act like a wall

they stop moisture from the Indian Ocean

passing over the land it's getting

hotter and drier the lush rainforest is

becoming arid savanna

the new hotter climate destroys the

creatures habitat

it forces them to search further afield

for food to stop dragging their knuckles

on the floor like Apes to stand and walk

on two feet it's the most important step

in the human story

this mountain range along Africa's East

Coast could be the reason we walk on two

feet it seems incredible the random

movement of two plates may have

kick-started a chain of events that will

lead to the first humans

the man and child it could be a scene

from our own time but it's one and a

half million years ago these are an

early species of human called Homo

erectus

and these are the first footprints like

our own civilizations past and present

everyone that's ever lived the greatest

inventions the most brilliant ideas

human history in all its complexity and

splendour begins here and now

the climate changes again 70,000 years

ago sea levels fall the gap between

Africa and Arabia shrinks down to just

13 kilometers the Red Sea is narrow and

shallow enough for this small group to

cross out of Africa

they're another later species of human

called Homo sapiens

they've made it across scientists

believe every man woman and child

outside of Africa is descended from

these 200 or so individuals over time

our ancestors multiply and spread out to

India on to Asia and into Europe

but while humans head north a giant wall

of ice travels south

Europe 40,000 years ago our Homo sapiens

ancestors are arriving only to find a

world that's changing fast it's getting

colder it should be the height of summer

but the plants are frostbitten the

rivers are frozen

natural changes in the Earth's orbit co2

levels and the flow of warm water around

the planet conspire to lower the earth's

temperature

the earth and its inhabitants enter an

ice age

Glacia is as high as skyscrapers creep

over the northern hemisphere at 30

centimeters a day

slow and powerful they sculpt the

landscape as they move over it

gouging out great depressions

the planet will never look the same

again

now around 20,000 years ago they grind

to a halt

much of the Northern Hemisphere is

covered by ice sheets up to two and a

half kilometers thick with trillions of

gallons of water locked up as ice sea

levels fall

twenty thousand years ago a strip of

land emerges from the ocean between

Siberia and Alaska

it's a bridge between two vast

continents a gateway that takes humans

from Asia to a new world America it's

the last great continent to be colonized

the last great human migration and

somewhere down there are the first

Americans

now 14,000 years ago the changes that

triggered the ice age go into reverse as

the ice retreats it reveals a very

different northern hemisphere the

glaciers gouged out huge depressions now

they fill with water to become North

America's Great Lakes

6,000 years ago the ice retreats back to

the poles to the Arctic and Antarctic

after a four and a half billion year

dirty we've made it we're back home this

is our world our time now for the first

time we can piece together our planet's

incredible story we can understand how

and why everything we see around us is

here today from the skies above us to

water the essential ingredient for life

the ground beneath our feet

and finally life

the spectacular result of a chain of

catastrophes and coincidences

each triumph each disaster is a step on

the trail that leads to here

to each and every one of us right now

the earth story doesn't end here

a lot has happened but there's more to

come

the earth will live for at least another

four and a half billion years everything

we've seen on our journey is only half

the story

just imagine what wonders what terrors

what strange creatures lie ahead for our

Restless creative planet

the next chapter of Earth's story is

still to be written

take another epic voyage in journey

through the Milky Way brand-new next

Sunday at 7:00

stay tuned for 2012 the final prophecy