All language subtitles for david.attenboroughs.rise.of.animals.s01e02.1080p.bluray.x264-shortbrehd

Of all the animals
that live on our planet,

one extraordinary group dominates.

It has produced the largest...

The blue whale!

...the fastest,

the most intelligent
creatures that have ever lived.

They're known as the vertebrates.

And they all share one
vital feature: A backbone.

I'm travelling back in time
to look for the key advances

that drove their remarkable success.

So far, I have seen the
vertebrates grow from tiny origins

to dominate the oceans,

colonise the land...

...and take to the skies.

In this programme, I'm going to
track the rise of a whole new branch

of vertebrate life.

The most complex animals
yet to appear on Earth.

They started as a group
of tiny little creatures

scarcely bigger than my little finger.

Nocturnal animals.

But they were to develop into
some of the biggest creatures

the planet has ever seen.

It's a group that also contains us.

This is the story of the mammals.

I want to investigate how the
mammals acquired a new set of key

features that allowed them to
thrive in every corner of our planet.

Features we also have inherited.

We'll find the evidence in a series
of thrilling fossil discoveries

and in living animals.

With the latest scientific analysis,

we'll be able to bring our
ancient ancestors back to life.

Today, animals with
backbones dominate our planet

on land, in the air and at sea.

But how did that evolutionary
takeover come about?

There've been lots
of gaps in the story.

But in recent decades,

exciting new discoveries
have been made here in China,

and I'm here to look at them.

The rocks of China are yielding
up the elusive missing links

in the vertebrate story.

Ancient creatures preserved as fossils.

To find new evidence from the
very start of the mammals' story,

I'm travelling to the south of China,

and the province of Yunnan.

Fossils found here can
reveal the kind of world

those first mammals encountered,
and the kind of animals

they had to compete with
to gain a foothold and survive.

This area of southern China
is known as the Lufeng Basin,

and 180 million years ago,
it was a vast natural hollow

into which waters from all
the surrounding hills flowed.

And with those streams came
sediment, which is now this,

and they also brought the
bodies of the animals that lived

in those hills, including
creatures like this one -

a dinosaur.

Excavators have uncovered
hundreds of specimens like this one

in the surrounding countryside.

The local museum is crowded with
one of the largest collections

of complete dinosaur
skeletons in the world.

But a unique discovery here

has revealed some
of the earliest evidence

for the origins of the animal group
that would eventually succeed them.

At the same time the dinosaurs
were roaming in this area,

there was another very different
creature evolving in their shadow.

One that was on a much,
much smaller scale.

Palaeontologist Wang Tao has spent
his life exploring these hills.

He's used to finding the
remains of large dinosaurs.

But on this hilltop site,
he and his colleagues discovered

something that didn't
match the usual profile.

I came to collect
fossils with my colleagues

in this area here.

At the time, it was not like this.

There were no crops growing here.

After looking around, we
followed this little slope.

And finally we found a small
fossil about two centimetres long.

We thought it might
be something special,

so we sent it to the lab
in Beijing to clean it up.

I have travelled north to Beijing to
see Wang Tao's discovery for myself.

It's now stored in one of
the world's leading institutes

for the study of fossils.

And this is it.

And what seems extraordinary,
near miraculous to me,

is that anybody should notice that
a tiny, tiny little thing like this

is actually a fossil.

But a fossil it is.

It's the head of the tiny animal.

There's the tip of its nose.

That's the back of its neck.

And you can also see
it's got an eye socket.

It's called Hadrocodium.

If I turn it upside down

you can see the bottom of its jaw.

It might be the skull of a
really minute little reptile.

But it's not.

Because reptiles have
simple cone-shaped teeth,

and this one has a tooth
that is rather different.

That has the shape of a little
insect-eating mammal's tooth.

So, this is one of the earliest
mammal fossils we know of.

And to that extent, it's the
ancestor of all mammals alive today,

including ourselves.

As such, Hadrocodium holds a key
position in the evolutionary story

of the backboned
animals, the vertebrates.

The first creature with
the beginnings of a backbone

lived over 500 million years ago.

Then fish,

amphibians

and reptiles evolved.

It's from the reptile line
that the first mammals emerge.

The Hadrocodium fossil dates
to 195 million years ago.

These simple origins led to
the vast diversity of mammals

we see around us today.

Over 5,700 living species
have adapted to survive

in every corner of the planet.

We humans dominate and are the
most numerous of the large mammals.

This astonishing journey
was built on a series

of key evolutionary advances
that began in very early forms

like Hadrocodium.

We only have its skull, but we
can work out from modern mammals

what the rest of its
skeleton was like.

So, how did this minute
animal gain a foothold

in the age of the dinosaurs?

Kunming city in southern China.

I've come to this late-night market

to observe one of the first
crucial steps in the mammals' story.

The development of an amazing feature

that gave them a key advantage.

But only after dark.

The mammals found a
niche for themselves

not so much in space as in time...
at night,

when the reptiles are not active.

A simple experiment with two pets

that happened to be for
sale in the market tonight

can demonstrate why this is so.

This is a thermal camera,

and it will show a cold
body as a black or very dark.

So, this lizard which is on
the table is cold-blooded,

and it appears to be very much
the same temperature as the table.

Reptiles get much of their energy
directly from the sun as warmth.

But there is no sun at night.

As a consequence, it's scarcely
got the energy to move.

This puppy, on the other hand,

is very active.

And when you look at
him with the camera,

you can see that his
body is very warm indeed.

And you mustn't eat the lizard!

The mammals, very early
in their history, developed

the remarkable ability to
generate heat within their bodies.

They became warm-blooded,

and they achieved this by
driving their metabolism

at a much higher rate.

But to do that, you need
extra fuel, extra food.

A reptile like a lizard can go
for many days without eating.

But if a mammal is denied its
food for several days, it will die.

So, in order to keep
their fuel bills down,

the mammals used a technique
familiar to any householder -

insulation.

They coated their
bodies, as this puppy has,

with fur.

With warm blood
and a covering of hair,

Hadrocodium was free to hunt for
insects in the cool of the night.

But now came a new challenge -

to find its way around
in pitch darkness.

Detailed analysis of Hadrocodium's
skull is revealing remarkable

new evidence of a set of ingenious
solutions to this problem.

The clues are tiny and
invisible to outside scrutiny.

But professor Zhe-Xi Luo,
an expert on early mammals,

is using a micro CT scanner to
unlock the skull's inner secrets.

X-rays penetrate the rock

and pick out detailed
fossil structures within.

A computer then builds
a 3D model of the bones,

and, in particular, the cavity
that once held the brain.

Professor Luo is able to
identify an area that is clearly

much larger than its
equivalent in a reptile.

If you look at the CT scan here,

you can tell that, despite a tiny
little skull, the brain is enormous.

But one of the most striking
features of this particular fossil

is that it has very
large olfactory bulbs.

When you say olfactory bulbs,

those are the part of the brain
that detects smell. Correct.

This mammal must have had
very refined sensory detection

of all kinds of smell, allowing it
to be active in the dark of the night.

This powerful sense of smell would
have helped Hadrocodium pick out

the scent of the worms
and insects it fed on.

The scanners have also revealed a
radical advance in a second sense

that's vital in the dark.

Hearing.

The tell-tale clue lies,
surprisingly, in Hadrocodium's jaw.

One very interesting feature

that's so unique about
this fossil mammal is...

very flat jaw.

The surface on the inside of
the jaw is perfectly flat.

In the primitive,

pre-mammalian forms,
there are big grooves.

Grooves like these indicate
the presence of two key bones

that are attached
to the jaw of a reptile.

Seen here in green and red.

A third bone, coloured blue,
transmits sound waves in its ear.

In a mammal there has been a truly
amazing evolutionary development.

The two jawbones have shifted
to form, with the third...

...the middle ear.

This three-bone arrangement

opens up a range of
higher-pitched frequencies

that a reptile cannot hear.

It's the system we have
inherited inside our ears.

So, in Hadrocodium, we
get the earliest indication

that the three ear bones
so important for our hearing

have already originated
with this fossil.

Now ears could pick up the
faintest rustle in the undergrowth

and guide Hadrocodium to
any insects moving nearby.

Professor Luo's analysis
has also identified

a spectacular advance
in a third key sense.

It also has very large areas

responsible for skin touch.

- For touch? That's right.
- Mammals have hairs.

One of the most important
functions of the hair is actually

to give us the sensory touch,

and this animal has
already developed that.

The use of hairs as touch sensors
is perhaps most obvious from the way

modern mammals use their whiskers.

This brown rat relies on them
for finding its way around at night,

or underground.

At the base of each of
those long hairs on its nose,

there is a nerve receptor.

And whenever the hair is touched,

a message is sent up to the rat's brain.

It's not just the whiskers, though.

Hairs all over its body are
wired up to its nervous system.

This creates a sensory bubble,

allowing the rat to map the world
around it just by using its hairs.

195 million years ago,

the hairs on Hadrocodium must
have been wired up in the same way.

This remarkable little
creature now had a whole array

of new powers with which to
meet the challenges of the night.

A heightening of the senses
powered by a growing brain

had enabled the early mammals
to survive in the shadow

of the dinosaurs. And then, they
also developed a radical new way

of nourishing their young.

We can look for clues
to this next crucial step

in our evolutionary
story in Australia.

Not in fossils,

but in the bodies of two highly
unusual creatures that live here.

The first is the platypus,

which uses its rubbery beak
like a radar transmitter

to hunt for shrimp or
molluscs underwater.

And the second is the echidna,

which forages for
ants and termites on land.

The platypus and echidna
are the only two survivors

of a group of mammals
called the "monotremes".

Trace their genetic line back,

and we discover they
split from all other mammals

around 200 million years ago.

Because they retain traits
from that distant time,

they give us a remarkable
insight into very early mammals

like Hadrocodium.

The most extraordinary feature
of all is one that no other

modern mammal has retained.

They lay eggs.

This echidna egg is tiny,

only about the size of a marble.

The hatching process itself has
only rarely been captured on film.

These are newly-hatched platypus young,

filmed in their mother's burrow.

They're only about the
size of jelly beans.

The early mammals must have
laid eggs in the same way,

and they inherited this trait
from their reptile ancestors.

This is a view inside a reptile egg.

The embryo feeds on a supply
of highly nutritious yolk.

By the time reptiles hatch,

they're sufficiently well-developed
to go looking for their own food.

But the platypus and
echidna are very different.

Their smaller eggs contain
only a small amount of yolk,

so their young hatch in
a far less-developed state.

They need a lot more nourishment if
they're going to grow and survive.

But at Healesville
Sanctuary near Melbourne,

we can find delightful evidence
that platypus young do develop

with great success without having
to leave their mother's burrow.

Four months after it hatched,

a youngster is emerging
for the first time.

It has grown from a tiny
hatchling to near adult size.

And that is thanks to an
amazing form of nourishment

that is a defining
feature of all mammals.

Milk.

This rich mixture of proteins,
fats, carbohydrates and minerals

oozes from the bellies of
female platypus and echidna

rather like sweat,

and provides their young with
everything they need to grow.

It's likely that early
mammals like Hadrocodium

nourished their young in the same way.

First with a reduced amount
of yolk, and then with milk.

So, what could explain this
hugely significant step?

New genetic analysis
is providing the answer.

Dr Henrik Kaessmann has been
using the platypus to investigate

the DNA of the early mammals.

The platypus is really
an amazing creature.

It's really this crossover
of a mammal and a reptile, right.

And so it has a key position
in the evolutionary analysis

of all mammals.

First, he looked at
the reduction in egg yolk.

Reptiles have at least
three genes that together

manufacture their large yolk.

Dr Kaessmann has found
that the platypus DNA

records a dramatic change taking
place in the early mammals.

We found only one egg yolk
gene in the platypus genome

that really was functional and
was producing the egg yolk protein.

Presumably the fact that
there was only one gene

which was producing yolk
accounts for the fact

that the platypus egg is so small?

Exactly.

The early mammals must have started
to switch off their yolk genes.

And Dr Kaessmann has made
a second key discovery.

The trigger for this shutdown
was the arrival of the genes

that produce milk.

So, you have the milk genes
appearing that then allow

for the subsequent loss
of the egg yolk genes.

The mammals began to favour
milk over egg yolk as a way

to nourish their young.

And that is because milk
has one key advantage.

It's on tap, and that means
that none of it need go to waste.

And there's no limit on how much

and for how long a
mother can feed her young.

Warm bodies, powerful senses,

and now, milk, had allowed
the early mammals like Hadrocodium

to gain a foothold while
the reptiles still ruled.

But combining egg-laying
with milk-feeding

brought a new challenge.

A mammal mother could not leave
the eggs to hatch by themselves

as most reptiles do today.

She had to stay with them.

Then came a truly astonishing solution.

The egg, instead of being laid,

was retained inside the body and
started its development there,

so that the young was born alive.

Apart from the monotremes,

there are two other major groups
of modern mammals around today.

Marsupials and placentals.

It's thought that they first appeared

around 160 million years ago.

Both give birth to live young.

But they do so in
two very different ways.

Spectacular fossil beds in the
north of China have, in recent years,

produced the earliest ancestors
yet found of these two groups.

This is Liaoning province.

125 million years ago,

volcanoes were erupting in this region.

They left layer upon layer
of yellow ash in these rocks.

Excavations have revealed
the fossilised remains of animals

trapped in these layers and
preserved in extraordinary detail.

This is a fossil that's
been called Sinodelphys.

Its skeleton is very easily seen.

But around its skeleton
there are dark marks,

and close examination
shows that they are fur.

So, we can be pretty sure that
this is the fossil of a mammal.

But its skeleton, and
in particular, its teeth,

make it clear that it was a marsupial.

Marsupials were once
distributed throughout the globe.

But most are found
today in Australia.

And they allow us to see

how their ancestors began to bring
their young into the world alive.

This is a sanctuary for breeding
endangered species of wallaby

through the use of foster mothers.

Running the conservation project

is Dr David Taggart of
the University of Adelaide.

Today, he and his team
are conducting a health check

on a newly arrived baby
wallaby, known as a "joey".

This joey looks like it's about
two grams, so about 16 days old.

So, 16 days ago, this
young would have been born.

All marsupial young are
born very immature,

so its ears are folded
and the eyes are closed.

Instead of being enclosed in an
egg when leaving its mother

like a baby echidna, this joey emerged

directly from its mother's birth
canal just 30 days after conception.

Its front legs are more developed

and strong enough for it to
pull itself up through the fur

and wriggle inside a feature that
is unique to marsupials ...a pouch.

Here, there's a highly
developed milk delivery system.

The milk is channelled through
long, fleshy tubes, teats.

A wallaby mother has four of them,

and can even feed young of
different ages at the same time.

She might have a young, just newly born,

attached to one teat,
and she'll have a young

with its head in the pouch
feeding from another teat.

And those two teats
will be producing a milk

that is of different consistency.

So, one will be to
nourish a new-born young

and the other's to nourish a
young that's almost ready to wean.

It's a great system.

The long teats also give
the young a way to cling

onto their mother as she moves around.

This opossum is a marsupial
that lives in South America

and it has no pouch.

Its young seal their mouths
so tightly round the teats,

they stay firmly attached.

This may well be how the early
marsupials, like Sinodelphys,

carried their young around.

They were now no longer
tied to a nest or a burrow

like the egg-laying mammals.

But this method had
one obvious drawback.

Outside their mother's body,

the newborn young were vulnerable
to accident and exposed to disease.

In China, new evidence is
emerging for the pioneers

of an even more radical solution.

At the same time as
the marsupials appeared,

another branch developed on
the family tree of the mammals,

a branch that we belong to.

And it had way of nurturing
their young before birth.

I'm travelling to Beijing and
its museum of natural history,

to see remarkably early
evidence for this group.

This is it.

It's been called Juramaia,

which means "Jurassic mother".

Its bones, and in
particular, its teeth,

identify it as a member of the
mammal group to which we belong.

But the key thing about it is its date.

It's Jurassic
- 160 million years old.

And this makes Juramaia the
earliest creature we know of

that could have nurtured its
young in a revolutionary new way.

Juramaia lived and hunted in a world
still dominated by the dinosaurs.

But it may have had
a powerful advantage -

the ability for a mother
to carry her young,

not outside her body
like the marsupials...

...but inside, in a womb.

To understand how Juramaia could
have achieved this, we can look at

one of its living descendants, the
one that carries its young inside

for the longest period
of all mammals, the elephant.

This is Dokkoon.

She is part of a breeding programme
at Melbourne Zoo in Australia,

and she is pregnant.

Dr Thomas Hildebrandt, one
of the world's leading experts

in mammal birth, is monitoring
progress with an ultrasound scanner.

We study the longest
pregnancy on the planet,

which the elephant has with 22 months.

And so ultrasound allows us

non-invasively to see
all the differences

during the foetal development,

which is quite exciting
and was never done before.

More detailed 3D scans give us

a spectacular view inside her womb.

Even at an early stage of development,

the baby's trunk is
visible and moving.

But we can also see the
presence of a remarkable organ

that evolved to make it possible to
feed a developing baby before birth.

The placenta.

This baby elephant was born
in the zoo just three weeks ago

and its placenta has been
saved for analysis.

Here we have the elephant placenta
of the baby which is running

outside the yard.

These blood vessels
form the umbilical cord,

allowing to move all
the nutrients to the baby

and take all the waste material away.

On the underside is a
ring of sponge-like tissue

that attaches to the
lining of the mother's womb

and allows nutriment to
flow in and waste to flow out.

But it also operates as
a life-saving barrier.

Because half of the unborn
baby's genes are from its father,

it was under threat in the womb
from its mother's immune system.

The baby is foreign materials
and alien to the mother,

and would be rejected if there's
not this very specific system engaged

which protects the baby against
the maternal immune system.

Because the tissues of the
placenta are composed of cells

from both mother and baby, and
the two blood supplies never mix,

the baby is protected.

This allows it to
remain inside the womb

until it's ready to survive
in the outside world.

Mammals equipped with this
miracle of evolutionary engineering

are known as "placentals".

It's likely that their earliest
ancestors, like Juramaia,

were the first to rear their
young inside their bodies

160 million years ago.

By now, the mammals had acquired
all the key characteristics

that define them as a group.

Hairy bodies,

milk

and live birth.

And this combination would
eventually provide them

with the platform for an
astonishing explosion in diversity.

For millions of years,
they remained the small,

shrew-like creatures that
we've encountered so far,

skittering about around
the feet of the dinosaurs.

But then came a
sudden global catastrophe

that threatened to bring the
whole history of the vertebrates

to a sudden end.

A meteor impact that sent
shock waves around the world,

and coincided with the
extinction of the dinosaurs.

We're still not exactly sure
WHY the dinosaurs disappeared,

but certainly 65 million years ago,

they disappear
from the fossil record.

But many other vertebrates survived,

and for them, the dominance
of the world was now up for grabs.

Scientists are unearthing
stunning evidence in Germany

for how the mammals
seized this opportunity.

This natural hollow is
known as the Messel Pit.

An entire community of
animals was entombed here

by an extraordinary freak of nature.

47 million years ago,

this was a lake fringed by
a subtropical rainforest.

But its waters held a dark secret.

The lake was in fact
a flooded volcanic crater.

It's thought that
lethal carbon dioxide gas

released from its depths
periodically bubbled to the surface,

killing the creatures that drank at
its shore or flew over its waters.

Their bodies drifted
down to the bottom

to be entombed in the muddy sediment.

It's now one of the most remarkable

fossil excavation sites in the world.

Painstaking work is uncovering
creatures sealed inside layers

of the ancient lake bed.

They're preserved
in extraordinary detail.

It's a unique snapshot of
life after the dinosaurs.

There are reptiles,
like lizards and snakes.

Here, too, are ancient birds,

the vertebrate group that
evolved from the dinosaurs.

But the biggest changes
are amongst the mammals.

They have started to specialise.

This, perhaps, is the
least specialised of them.

It's an insect-eater, a
creature like a large shrew,

and its teeth are
still relatively simple.

But then there are also
animals like this.

And this has very big,
gnawing front teeth.

This is an early rodent,
a creature like a rat.

And then bigger still...

...is this animal.

This has grinding molar
teeth at the back,

and long legs.

It's beginning to stand up on its toes.

This is an early horse.

And perhaps the most
specialised and remarkable of all

at this still very early date

is this extraordinary specimen.

This, as you can see, is a bat.

And the preservation is so remarkable

that the skin can be easily seen,

not only on its forelegs,

which turns them into wings,

but even you can see this large ear

on the side of its head,

which suggests that already it
was beginning to echo-locate,

to hear its own calls so
it navigates during flying.

The mammals were displaying
an extraordinary ability

to rapidly adapt their bodies to
fill the range of niches left vacant

by the death of the dinosaurs.

They had new opportunities,

but they also faced a
new evolutionary pressure.

Climate change.

Ten million years of
gradual global-warming

had triggered a surge in plant life.

The land became covered in forests
that grew ever denser and darker.

New mammals emerged with
new features that helped them

to thrive in this
changed environment.

Features that would have
huge significance for humans.

This is an early member
of the group of mammals

that was going to produce us.

This is an early primate.

And you can see that on
its front legs, its hands,

they have an opposable thumb,

so it could grasp.

And the same on the back legs
...the big toe is also opposable.

So, this animal was a climber.

The primates could now reach
food that was high up in trees.

And it's thought that it was
a new type of food that triggered

another astonishing
advance in their bodies.

A major improvement in sight.

Dr Sandra Engels is
part of a team investigating

the diet of the fossilised
primate from the Messel Pit.

Remarkably, she's able to examine
the preserved contents of its gut.

We have particles of the
last meal of this primate,

and we analysed it with
very high magnification

and we found the
oval outline of a seed

which is part of a fruit.

And because we found it
in the gut of this primate,

we know that it fed on fruit.

3D scans of its teeth make it
clear that fruit was a major part

of its diet. This animal was
a specialised fruit-eater.

If we take a closer look
to the shape of the teeth,

we have structures as
deep basins or rounder cusps

that are the right
tools to break up fruit.

47 million years ago,
large, fleshy fruit like this

had only recently been
developed by plants.

It was one of the ways
in which they had adapted

to the new dense forest environments.

Many early plants relied on the
wind to distribute their seeds.

But in the forest, there is little
or no wind, so they had a problem.

They solved it by
recruiting the help of birds,

and they did that by
wrapping their seeds

in an edible, sweet flesh, fruit.

Birds carried the
seeds in their stomachs

and eventually deposited
them elsewhere in the forest.

The primates had clearly begun
to exploit this cosy arrangement,

but to take full advantage,
they needed to improve their vision.

During the age of the dinosaurs,

when the mammals were largely nocturnal,

they had developed better night vision,

but sacrificed a feature
not needed in the dark.

The ability to see colour.

Today, most mammals still see the
world largely in black and white.

But the reptiles and
their cousins, the birds,

retained excellent colour vision.

And the fruit-bearing plants

had evolved a signalling
arrangement to match.

There's no point in having
your seeds distributed

before they're fully formed.

So, the plants evolved
a colour-coding system

to show when that was.

This plant, for example, here
is a young fruit still growing.

Its flesh is hard and
bitter, and it's green.

But this fruit is fully formed.

Its flesh is good to eat, soft,

and the seed within is ready to go.

And it's red.

To spot a flash of red colour
in amongst the green foliage

is easy for a bird or a reptile.

But for a mammal, with
their night-time vision,

red and green are indistinguishable.

Then, remarkably,

some of the primates managed a
feat no other mammal has achieved.

They put evolution into reverse
and re-acquired colour vision.

The common ancestor
of this monkey, and of me,

lived up in the trees in the daylight.

And they quickly evolved
the ability to see colour,

and therefore, to know which was
ripe and which was unripe fruit,

and so take advantage of the system

that had already been worked out

between the birds and the plants.

Let's just see what
she thinks about that.

Which of those do you like?

There's it.

After the dinosaur extinctions
of 65 million years ago,

the mammals were using their
spectacular adaptability

to evolve and diversify
at an astonishing rate.

In the process, they
laid the foundations

for the major mammal
groups we see today.

But then, around 47 million years
ago, came a new set of problems.

The Earth's climate
changed yet again.

Many places became drier,
and where that happened,

the forest thinned out and was replaced

by low, scattered bushes and grass.

And those new environments
presented new challenges to animals

and ushered in the age
of the mammal monsters.

Scientists are finding
stunning evidence of this change

in the Great Plains of North America.

This dramatic country in South
Dakota is known as the Badlands.

Streams and rivers have eroded
the rocks into fantastic shapes.

But 40 million years ago,

these were layers of sediment laid
down across an open flood plain.

Palaeontologist Clint
Boyd is looking here

for the fossilised remains of
creatures from that ancient time.

And he's finding
mammals that are giants.

This is part of the bone we call
the femur or the upper-thigh bone,

and this round surface right
here is for the hip socket.

And so you can see it's very large.

We'd be talking about
a very large animal.

And not only do we have the
thigh bone but we've got ankle bones

spread out over here, and then
cascading down from that spot,

we've got some of the
tail bones coming down.

So, if we add all this up
together, based on the size,

we're looking at an
animal that's probably

about two metres tall at the hips.

The creature is known as a Titanothere.

It was a herbivore.

It fed on the lush vegetation
that once covered this area

of the United States.

A range of different
specimens have been collected

at Denver Museum of Nature and Science.

And they reveal that
the first Titanotheres

were built on a much smaller scale.

When Titanotheres first appear
on the scene, they look like this.

This is the lower jaw of one
of the first Titanotheres,

and it's one of these
sheep-sized animals.

In only five million years,

members of the group
go from sheep-sized...

...to about the size of a small horse.

Within only 15 million years
of their first appearance,

Titanotheres look like this.

Here you can see the skull
of one of these Titanotheres.

In evolutionary terms, the size
increase is astonishingly quick.

But what drove
this remarkable change?

Another fossil could
provide an explanation.

It dates back to the time of the
first and smallest Titanotheres,

but it's a very different
type of mammal.

This is the skull of
Malfelis Badwaterensis,

the "bad cat from Badwater".

This was the largest
predator at the time.

This is the skull. This large
crest is for large jaw muscles

which would've given a powerful
shearing bite that ran these

blade-like teeth, perfect
for chopping up a Titanothere.

And what's interesting is
that Malfelis was exactly

the same size as the top herbivores
of the time, like Titanotheres.

The earliest Titanotheres
could hide from these bad cats

in the dense forest environments.

But as those forests began to thin out,

the Titanotheres were
more vulnerable to attack.

One way to improve their
chances was to grow bigger.

An herbivore is much more
likely to survive an encounter

with a predator if it's
a little bit larger.

And so there was a bit of an arms race

between the predators and the prey.

And animals like Titanotheres were
able to escape this predator pressure

by becoming the super-sized
giants we see 35 million years ago.

Fossilised remains of Titanotheres
from the Badlands of South Dakota

and elsewhere across the Great Plains

allow us to reconstruct
its rapid growth spurt.

From modest beginnings,

they increased their
bulk ten times over...

...till the largest stood
over eight feet tall.

On the open grasslands that
increasingly covered the Earth,

many other giant mammals emerged.

Together, they're
known as the "Megafauna".

This giant sloth
was found in California.

In China, I've come to see
the remains of mammoths.

And a remarkable creature that
was the largest land mammal

to walk this Earth.

This great beast is
called Paraceratherium.

It stood five metres tall
and nearly eight metres long.

Those furry little mammals

scampering about in the
shadows had produced descendants

that could stare the
biggest dinosaur in the eye.

Today, the elephant is one of
the few species of Megafauna

to have survived.

But those outsized versions

have otherwise disappeared
from the planet.

So, what happened to them?

Their eventual extinction
coincides with another key event

in the history of the Earth.

From around two and
a half million years ago,

ice sheets spread down from
the North and up from the South

to cover vast areas of the continents.

But it was only when the
ice finally retreated,

just 10,000 years ago,
that the Megafauna vanished.

Some have blamed that on the
rise and falls of the temperature

as the Ice Age finally came to a close.

But others have sought the culprit
amongst the mammals themselves.

A newly-evolved super predator.

To see some of the earliest
evidence for its arrival in China,

I've returned to Beijing.

These fossilised remains
belong to a primate.

It's been dated to
around 68,000 years ago.

This primate had two
new evolutionary features.

First, its pelvis.

An animal with a pelvis like this

would have been able to walk upright.

Secondly, the skull.

Its brain case is enormous.

In proportion to
the size of its body,

it's six times the
average mammal size.

And that would have
brought great intelligence.

And this creature, of
course, was a human being.

The early humans put their
new intelligence to deadly use.

They worked out how to make weapons.

These stones, carefully
chipped to form sharp blades,

were found alongside human remains.

And they developed new
powers of communication

that enabled them to join
forces and hunt in teams.

This was a new kind of predator.

It first appeared in Africa

and then spread to
all the other continents,

and each time its
appearance in that continent

coincided more or less with
the disappearance of the Megafauna.

Which suggests, at the very least,

that this creature had
something to do with that event.

To conclude my journey in China,

and find the last step
in our evolutionary story,

I'm back in Kunming city to visit
one of its busiest maternity wards.

An enlarged brain brought
us huge advantages,

but its size also presented
a basic design problem at birth.

The bony skull encasing the brain

still had to make it out
through the mother's birth canal.

A new addition to our
species, just 12 hours old,

can reveal how this is possible.

This little boy's name is Shao Bao.

It means "little treasure".

He was born because of a
special feature in his skull.

Mammal skulls are made
up of separate bones.

And in most species those are
fused together at the time of birth

to form a hard, bony box to protect
that most special organ, the brain.

But not so with Shao Bao
and other human beings.

They remain separate,

and that allowed his head
to slightly change shape

and squeeze through the
aperture of his mother's pelvis.

This also allows the brain to
continue to grow and develop

after birth.

In fact, the plates
won't start to fuse

until Shao Bao is
around two years old.

It's one of the most recent

in a long line of remarkable
evolutionary developments

that allowed the vertebrates,
animals with a backbone,

to create the dazzling
diversity we see around us today.

Shao Bao's ancestry,
like that of all of us,

stretches back over 500 million years

to a tiny little wormlike creature
swimming in the bottom of the sea.

His backbone and jaw
came from the early fish.

His limbs and lungs from amphibians.

The reptiles gave him
his watertight skin.

Tiny nocturnal mammals
donated a bigger brain...

...sharper senses...

...and the manner in which he was born.

His hands and colour vision
came from the fruit-eating primates.

And his larger brain and greater
intelligence, from the first humans.

So, all our features of
our body can be traced back

to our ancient ancestors,

and there's much more we
have yet to learn about them.

But one thing is certain -

the evolution of the vertebrates
has not yet come to an end.

Subtitles by Red Bee Media Ltd