[tense music playing]
[distant roaring]
[Morgan Freeman] In the four billion years
of life on our planet,
countless species have risen
and fallen.
[distant roaring]
But one remarkable dynasty
has had a greater impact than any other.
[roaring]
The mammals.
This is the story of their epic journey
[roaring]
to become rulers of the world.
[music fades]
[rousing music playing]
[snarling]
[trilling]
[screeching]
[rousing music continues]
[growling]
[wind howling]
[rumbling]
[rousing music intensifies]
[music fades]
[insects chirping]
Hidden in the ancient Jurassic forests
mammals came from humble beginnings
ruled over by the greatest dynasty
that ever lived
[distant bellowing]
the dinosaurs.
[growls softly]
They dominated so totally
[snorting]
that early mammals
were confined to the shadows.
For the most part, they were small,
keeping to the trees
away from the giants.
They became nocturnal,
developing a range of heightened senses
that helped them in the dark.
Under the dinosaurs' rule,
there was a limit
to how far they could rise.
But in time, everything changed.
One of the most violent events
in our planet's history
heralded a new era.
[poignant music playing]
Despite the devastation,
the planet did recover.
Within a few million years,
forests had regrown
and carpeted much of the land.
The climate became hot and wet.
The perfect conditions
for life to flourish.
A world primed
for a new wave of evolution.
- [insects chirping]
- [birds squawking]
The asteroid had inflicted
devastating losses on the mammals
yet some of the smaller ones,
able to hide in holes, had survived.
[creature chattering]
Free of the dinosaurs,
they could finally
venture out of the shadows
and come into the open.
- [birds chirping]
- [chattering]
Like their ancestors,
coatis have many adaptations
that help them thrive
in the rich rainforest.
Extremely social,
they find safety in numbers.
The mother's flexible nose can smell food
hidden beneath the leaf litter.
A supersense honed over millions of years
of foraging in the darkness.
Like all mammals, coatis are warm-blooded,
so can be active at all times.
That means these babies
need plenty of energy.
Fortunately, mammals have evolved
an extraordinary solution.
Milk.
[suckling]
They can feed their young
whenever they choose,
even when food is scarce.
But milk wasn't
the early mammals' only secret w*apon.
They also had brain power.
[tapping]
And it's still just as important today.
In the forests of Costa Rica,
this capuchin monkey
is trying to solve a puzzle.
How to get the meat
from inside a closed clam.
The monkey isn't strong enough
to cr*ck the shell
[tapping continues]
but it's discovered that repeated
hammering will tire the clam
until it finally opens.
Learning this lesson takes a large brain
[clam thuds on ground]
- and coordination.
- [squeaks]
[playful music playing]
This unique intelligence
allowed their primate ancestors
to survive in the forest
of 50 million years ago.
Clever animals tend to be inquisitive
and that can pay huge dividends.
This female has learned
and remembered
where she can find water.
But it's too deep to reach.
Luckily, she has an inspired solution.
She turns her tail into a sponge.
But not all their challenges
are to do with finding food and water.
[squeaks]
Some fruit is collected not to eat
but to rub over their bodies.
This fruit contains citronella,
an oil that mosquitoes can't stand.
[uplifting music playing]
The monkeys have discovered
their very own insect repellent.
Free from pesky biting insects,
the clever capuchins can finally relax.
[music ends]
But just as their ancestors
were beginning to make progress,
the warm, wet conditions
in which they had thrived began to change.
The Antarctic landmass
started to split away from South America
creating the space for new ocean currents
that helped drive a global cooling.
The climate was switching
into a new, colder state.
[poignant music playing]
But that was just the beginning.
As Antarctica became colder
and more isolated,
the huge continent froze,
locking up
much of the planet's fresh water.
As the world further north dried out,
it became a harsher,
more difficult place to live.
Food became more spread out,
harder to find.
And as the Earth changed,
so did the mammals.
[heavy footstep]
[snorting]
Some became enormous.
A male Megacerops.
[grunting]
Two and a half meters tall
[grunting]
four meters long
and three tons in weight.
[snorting]
[grunts]
Its huge size allows it to travel
large distances in search of food
[grunting]
and ensures it has reserves
to get through leaner times.
[majestic music playing]
Mammals were now big enough
to rival the long-lost dinosaurs.
But being big has other implications
especially when it comes
to finding a mate.
[snorting]
[grunting]
This female is already
closely guarded by a male,
much larger than the first.
[snorts]
[growling]
If challenged,
he could seriously injure his opponent.
[roaring]
[snorts]
[grunting]
But the smaller male may be in luck.
Another female,
and she seems to be alone.
[grunts]
It's the chance he's been waiting for.
[grunting]
[growling]
He has a rival.
[roaring]
This time, they're evenly matched.
[grunting, growling]
[tense music playing]
[bellows]
[grunting]
[bellows]
[roars]
- [bellowing]
- [growling]
[roaring, growling]
[growling]
[grunting]
With these mammals
[growls]
size matters.
But even the mightiest Megacerops
couldn't overcome
the planet's next great challenge.
The formation of Antarctica
was creating global climate chaos.
As ocean currents shifted
and the planet dried
it became a tinderbox.
[mournful music playing]
Wildfires ravaged the land
clearing the way
for something completely different
something that would challenge mammals
as never before.
As the smoke cleared,
there rose from the ashes
a life-form that had previously
only survived in the margins.
Grass.
Taking root during the great drying
it spread so quickly,
it would soon cover one-fifth of the land.
But the endless plains
were no paradise for the mammals.
Many couldn't digest grass
and soon went extinct.
[insects chirping]
[snorts]
Twenty million years later,
and today's grazing mammals
remain locked in an arms race
with this green invader.
They have evolved a whole swathe
of game-changing adaptations.
Specialized teeth,
strengthened to prevent silica
in the grass
from wearing them out
and huge bellies to process it all.
Their young are born fully formed
[snorting]
able to walk within hours of birth
and follow their herd
in search of fresh growth.
Mammals have truly conquered
the grassy plains
their huge numbers the most obvious sign
of this exceptional success.
But just as some mammals evolved
to feed on the grass,
others evolved to feed on the grazers.
Hunters.
[herd lowing]
The herd has its own defense
against the cheetahs' blistering speed.
- Many eyes
- [snorting, grunting]
spot the danger early.
- [herd grunting]
- [bird squawking]
[tense music playing]
[grunting]
Running bodies create confusion
for the young to hide in.
But the big cat has a plan
forged by its clever mammalian brain.
Panic the herd,
split them up,
and target a lone calf.
[tense, energetic music playing]
Desperate to defend her only calf,
the female wildebeest counters.
The chase is far from over.
The cheetah has lost a lot of ground
but the calf is tiring.
[tense, energetic music continues]
[music slows]
As the youngster turns,
it's the hunter
who must now run for its life.
[herd lowing]
The calf is safe once more
[calm music playing]
but the cheetah will be back
and the w*r between the grassland mammals
will continue
as it has done for millions of years.
[tranquil music playing]
In prehistoric South America,
the grasslands played host
to the same battle
but with very different animals.
[intriguing music playing]
This giant armadillo
is also a mammal
though one the size of a car.
Doedicurus may not be fast,
but what they lack in speed
[trilling]
they make up for with armor
and a lethal tail
[grunts softly, snorts]
adaptations that protect them
and their young
from any would-be predators.
[trilling]
[ominous music playing]
[soft growling]
A Smilodon
but a mere youngster.
- [soft growling]
- [snorting]
[whimsical music playing]
[trilling]
He's not a serious thr*at
[trilling]
[hissing, growling]
even with his dagger-like teeth.
He's never seen a Doedicurus up close,
and their defenses are intriguing.
[hissing]
[soft growling]
His curiosity gets the better of him.
[trilling]
[purring]
[trilling]
- [grunts]
- [hisses]
[whimsical music continues]
[trilling]
He explores every angle.
[snorting]
[trilling]
For the young Doedicurus,
the only option is to stay put.
[trilling]
The giant armadillos' armor
is completely impregnable
[growls softly]
and they know it.
- [trilling]
- [growling]
[growling]
But there is one obvious opportunity.
[trilling]
[growls]
The young Doedicurus is so much smaller.
If he can get a hold on it
- [growling]
- [trilling]
he might be able to turn it over.
[hissing]
[trilling]
But not with the adults around.
[low growling]
- Another stalemate.
- [juvenile moans]
- [trilling]
- [snarling]
Battles between the mammals
have always driven their evolution,
and they don't just happen
in the grasslands.
[wind whistling]
Fifty million years ago,
what are now India and Asia
collided on an epic scale.
The crash forced the land into the sky,
creating the towering Himalayas.
[majestic music playing]
Today, they are 2,500 kilometers long,
almost nine kilometers high,
and still growing.
With their freezing temperatures
and thin air,
these mountains are uninhabitable
for most animals.
[unsettling music playing]
But not all.
Deep in a sunless valley
a male snow leopard
and an ibex that has fallen to its death.
The leopard is very old,
worn and tattered
by his harsh mountain life.
At these altitudes,
mammals must feed regularly to keep warm.
But the Himalayas present
the ultimate hunting challenge.
High above the valley, a female
and her cubs, fathered by the male.
Three of them in total,
all amazingly camouflaged.
Snow leopards have thick fur,
large paws,
and long tails
perfect adaptations for the coldest,
most precipitous nursery on Earth.
[stirring music playing]
[music fades]
Away from the dangerous cliffs
[light, playful music playing]
the mother initiates a hunting lesson.
[soft growling]
[growling]
Teaching and caring for one's young
is a key mammalian trait.
These cubs will stay with their mother
for nearly two years
learning the skills needed to survive
on the very edge of life.
[music ends]
At these altitudes,
every opportunity must be taken.
The old male is tracking a herd.
In this vertical world,
he must get above his prey
[tense music playing]
and close enough
for an ambush.
[tense music continues]
[loose rocks tinkle]
[rocks clattering]
[water splashing]
[snorts]
This time
death has claimed them both.
[poignant music playing]
But the leopard's legacy lives on.
In a few months' time,
his cubs will leave their mother
and start to hunt alone,
having learned all the skills they need
to survive at the top of the world.
Although they had conquered the land,
the mammals didn't stop there.
[insects chirping]
One branched out and went
in an entirely different direction.
Fifty million years ago,
bats opened up a whole new realm
through flight.
[gentle music playing]
Flying allows animals
to search much further for food
and gather in their millions.
Today, one in five of all mammal species
is a bat.
[high-pitched squeaking]
But bats were not the first animals
to take to the skies.
Having spent the night foraging,
these fruit bats are in a race
to return to the roost
[high-pitched squeaking]
for with daylight comes danger.
[tense music playing]
Birds.
[high-pitched squeaking]
They evolved flight
long before the mammals.
[tense music intensifies]
Faster and stronger than bats
eagles are armed with deadly talons.
[squeaking]
[music fades]
[high-pitched squeaking]
But as dusk falls,
the skies belong to the bats once more.
[serene music playing]
Millions take to the wing,
knowing that safety lies in numbers
and in the coming darkness.
At the same time
as bats were first moving into the air,
other mammals were moving into the sea
attracted by the abundance of food
hidden beneath the waves.
The mammals' journey into the oceans
was a gradual one.
[lowing]
These are Maiacetus,
two-and-a-half-meter-long ancestors
of the whales.
[lowing]
But unlike whales, they still spend
much of their time lazing on land.
[peaceful music playing]
It's in the water that they come alive
chasing schools of fish.
His time down here is limited
by how long he can hold his breath.
He seems caught between two worlds,
especially when facing danger.
[ominous music playing]
The mammal's intelligence
is his only defense
but he can't stay down here forever.
[ominous music continues]
Otodus.
Twice the length of a great white shark.
With finely-tuned senses,
it can pinpoint his exact location,
and it's in no hurry to make its move.
The Maiacetus is running out of air.
[tense, hurried music playing]
In open water, there's no escape.
An overhang offers refuge.
But time is running out.
[music intensifies]
A gully provides cover.
[music fades]
[grunting]
Safe
and able to breathe once more.
[lowing]
[grunting]
Mammals had a long way to go
to become masters of the world's oceans,
but it was only a matter of time.
As the planet continued to cool,
it fed an expl*si*n of life
allowing the giants of today to evolve.
[rousing music playing]
The mammals had gone
from tiny land animals
to being bigger than dinosaurs.
With each giant breath,
they use oxygen
far more effectively than Maiacetus.
And being warm-blooded,
their muscles are always at a temperature
for maximum performance
allowing the whales
to generate sustained bursts of energy.
[dark, pulsing music playing]
When competing for a mate,
humpback males
exploit this ability to the full
pursuing a single female.
This is much more than about speed.
The males stay
as close to the female as possible
so she can judge
their strength and stamina.
[dark, pulsing music continues]
Bubble streaming intimidates rivals.
The males plow into each other.
Some get left behind,
still fighting.
[dramatic music playing]
The main group keeps up the chase
hot on the tail of the female.
[music ends abruptly]
Then suddenly,
she stops.
[peaceful music playing]
Hanging in the water
she has called off the race.
She has made her decision
and allows one male
to approach.
The mammals have conquered
every habitat on Earth.
Land, air, and sea.
The asteroid strike had allowed
the mammals to go from lowly underdogs
to become a global power.
Such is the role of chance
in the history of life on our planet.
[music fades]
But there is one more chapter
in the mammal story still to be told.
Two and a half million years ago,
the mammals were faced
with a new challenge.
[wind howling]
[poignant music playing]
What had been
a slow cooling of the planet intensified.
The start of an ice age.
From its frozen wastes
would come a new force
a mammal armed with more intelligence
and adaptability than any before.
The most dangerous animal
the world had ever seen.
[sinister music playing]
[music ends]
[rousing music playing]