David Attenborough's Rise of Animals: Triumph of the Vertebrates

'Of all the animals that live on our planet,

'one extraordinary group dominates.

'It has produced the largest...'

The blue whale!

'...the fastest,

'and the most intelligent creatures

'that have ever lived.

'They're known as the vertebrates,

'and they all share one vital feature.

'A backbone.

'Now, I want to travel back in time to explore their ancient origins.

'And investigate the key advances that led to their amazing success.'

Advances that can also reveal

how we came to acquire the characteristic features

of our own vertebrate bodies.

Jaws that bite, lungs that breathe, ears that can hear.

Because the story of the rise of animals

is also the story of how you and I came to be as we are.

'I will find evidence in a series of spectacular fossil discoveries

'around the world and within living animals.'

That's it.

'With the latest scientific analysis,

'we can bring our ancient ancestors back to life.'

And understand how, over 500 million years,

they developed the bodily features needed to master the seas...

...colonise the land, and take to the skies.

This is the story of the rise of animals.

The history of life on Earth

has been known in outline for many years,

but there were a number of tantalising gaps in it,

particularly in the history of animals with backbones.

When, for example, did the first signs of a backbone appear?

And is it really true that dinosaurs developed feathers

and turned into birds?

Well, in recent decades,

answers have been found to those extraordinary questions,

here, in China, and I'm here to look at them.

China is the new frontier for fossil discoveries.

Excavations here are unearthing links in the story

of the vertebrates that have so far eluded us.

I have long wanted to see this sensational evidence for myself.

I will be travelling to the frozen north of the country,

and to the capital, Beijing.

But to search for the first step in our journey,

I'm heading south, to Yunnan Province.

This is the site of a thrilling discovery that has given us

new evidence for the very first vertebrates.

Excavators here are exposing a rich seam of rocks

known as the Chengjiang fossil beds.

Remarkably, they contain the remains of creatures that once swam

in the ancient seas 525 million years ago.

'Palaeontologist, Hou Xianguang, was the first to discover

'the unique features of these beds,

'an astonishing perfection of preservation.'

Are these mouth parts?

Yeah. That's very beautiful.

You can see it's got striations on it.

'To find complete bodies like this is extremely rare.'

When an animal dies in the sea,

normally bacteria destroy the soft parts very quickly

so that all we can find afterwards are the hard parts, bone or shell.

Why that didn't happen here in this particular part

of this particular sea is something of a mystery.

It may be something to do with the lack of oxygen,

but whatever it was, it has given us a privileged view

into one of the most exciting chapters

in the whole history of life.

The beds have so far yielded over 200 separate species.

This was a time period known as the Cambrian.

The land was still bare and lifeless,

but, underwater, it was exploding into a multitude of forms.

The major animal groups we know today were appearing on the planet

for the very first time.

They built their bodies entirely of soft tissue.

Some protected and supported it with a hard outer casing.

But none had anything that resembled a backbone.

These were the invertebrates.

'Then, Professor Hou and his team found one intriguing exception.'

Oh, yes, yes, yes.

It's a fossil called Myllokunmingia.

But to examine it in detail,

you've got to look at it under the microscope.

Its features reveal evidence of a new type of support,

not outside the body, but inside.

This is one of about 30 specimens that have already been found

of this tiny little creature.

Under the microscope, it contains an extraordinary amount of detail.

Those marks are marks that have been made by the excavator's needle.

This is the animal itself. This is its head, the top of its back.

And nearly every one of them have these two little black spots

at the front, eye spots.

Looking farther down the animal,

there are just some striations here,

little bars which are thought to have been the gill bars,

the little constructions that carry blood vessels

which enabled the animal to extract oxygen

from the waters it flowed over and breathe.

And behind them, farther down the animal, there are these bars...

...bands of muscle, and they were probably attached to a gristly rod

somewhere in the middle there.

This is called the notochord,

which was the forerunner of the backbone.

Myllokunmingia is the earliest creature we know of

that we can truly call a vertebrate.

And it seems clear that it used its strong inner rod

to move in an entirely new way.

As the muscles contract, they bend the rod from side to side.

This movement pushes against the water and creates forward thrust.

Here was a revolutionary new way to get around.

It allowed Myllokunmingia to roam far and wide and escape

the dangerous invertebrate predators that were prowling the seas.

The vertebrates would diversify over millions of years

to create the spectacular variety of backboned creatures we see today

in every environment on the planet.

Fish dominate the seas, lakes and rivers.

The amphibians live in both water and land.

The reptiles can survive in the driest places on Earth.

The birds rule the skies...

...and the mammals have insulated their bodies

to adapt to every climate.

We humans have used our greater intelligence to overrun the planet.

This astonishing journey

was built on a series of key evolutionary steps

that helped our ancient ancestors to exploit their environments

and overcome huge challenges.

The first of these advances was the development

of that inner support - The notochord.

Back in Europe, you can find a creature that represents

the next critical step in our story.

It lives unobtrusively and often ignored in British rivers.

And it sheds light on the challenges those first vertebrates faced.

Ah, there it is!

This is a lamprey.

You might think at first sight that it was a kind of fish, but it's not.

It's something much, much more primitive.

It has no fins, and even its tail

is nothing more than a flattened blade.

But what is most remarkable about it

is that it doesn't really have a true mouth.

Its mouth is just a simple hole

with little bristles about it.

And it feeds by sucking in water through that mouth

and then filtering out little particles of food.

So this little animal takes us right back to the time

when the first animals with backbones appeared on Earth.

It's a true living fossil.

The first vertebrates seem to have had the same kind of mouth

and they were almost certainly limited

to the same kind of simple food.

Over time, other forms evolved with different shapes and sizes,

many of them rather larger than Myllokunmingia,

but all of them had that very simple mouth,

an opening at the front of the body as the lamprey has today.

If the early vertebrates were going to really take advantage

of the variety of food that was available in those early seas,

they were going to have to develop a much more complex

and powerful form of eating machinery.

Scientists on the east coast of the United States are seeing evidence

of this evolutionary advance, not in fossils but in living creatures.

Maine, New England.

Marine biologists at the University of New England

are studying a group of fish with a very ancient ancestry.

They build their skeletons with the same strong material

that formed the gristly rod of the first vertebrates - cartilage.

They're the sharks, skates and rays.

This group appeared among the vertebrates

over 420 million years ago.

And that means we can use them

to examine the development before that split of a remarkable piece

of engineering that changed the course of evolutionary history.

The jaw.

If you look back on the evolutionary tree,

you'd find that a jaw is a really important feature to have

and it's one of the features that have made skates

and sharks apex predators in the environments in which they live.

A jaw hinged to the skull brought the new ability to grab food,

then rip or grind it into digestible pieces.

But where did this amazing piece of equipment come from?

Scientists have found an answer

by studying the way living vertebrates develop as embryos.

Skates lay their fertilized eggs on the sea bed

inside leathery cases called mermaid's purses.

Scientists can open these up and observe them as they develop,

fed by a generous supply of egg yolk.

The skate embryo has a simple structure

shared by all embryonic vertebrates

that served as the basis of the first jaw.

What we see are these folds...

...and what's really interesting about this,

is that this skate is in about...

four months of its development.

If we take a close look at another vertebrate,

we can see it looks very similar.

Here we have the head, as you can follow it down to the body.

You also see the folds.

Now, this is actually a human being.

It's thought that the embryos of the earliest vertebrates looked

much like this and that each fold developed into a gill.

In a skate embryo, the folds furthest from the head

keep to their original purpose and form the rigid arches of its gills.