David Attenborough's Conquest of the Skies 3D Page #3

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Its immense wingspan allowed it

to ride on the currents of warm air

that rise up from sun-heated land.

It could then glide great distances,

searching for food.

Small creatures like lizards,

or the dead bodies

of much larger ones, dinosaurs.

But the Pterosaurs,

with their wings of toughened skin,

weren't the only group of reptiles

to make it into those ancient skies.

About 150 million years ago,

another reptilian group appeared

on the planet that also flew.

Like most reptiles, including Pterosaurs,

these creatures began their lives

inside an egg.

But they had evolved

a revolutionary new design for flight,

one that would usher in

a remarkable fresh chapter, in our story.

And unlike the Pterosaurs,

they're still with us today.

There are of course, the birds.

Some today can provide clues,

about how their ancestors

managed to get into the air.

This is the chick of a bird

found in farmyards everywhere:

A Bantam Hen.

And at this very early stage in its life,

it can show us something very interesting

about the origin of that crucial piece

of flying equipment, a feather.

Its feathers are downy, that's to say,

they're made up of simple filaments,

and their function is not for flight,

but insulation,

to keep this little creature warm.

And back in the Jurassic period,

long before the arrival of true birds,

very similar looking feathers

appeared on very different animals,

reptiles, dinosaurs to be precise.

To find evidence

for that astonishing statement,

which not so long ago was highly

controversial, we're heading for China.

Northeast of China's Great Wall,

near the borders of Mongolia,

lies the chilly province of Liaoning.

Here, there are great areas

of rocks that were laid down as mud,

in the bottom of immense

fresh water lakes.

The bodies of animals that

were swept down into these lakes,

were slowly entombed

by the fine-grained sediment

that preserved them entire

and in exquisite detail.

And from these rocks have come specimens

that solve one of the most hotly debated

of evolutionary arguments:

The origin of the birds.

The key specimens are now in Beijing,

where they've been delicately prepared,

under the microscope.

They have been studied here, by one

of the world greatest dinosaur experts,

Professor Xing Xu.

First, he showed me

one of his oldest specimens,

part of a dinosaur's arm.

But thanks to the fineness

of the mud of those ancient lakes,

there is more here than just bones.

You see here, this species

is called a Beipiaosaurus,

So because this is an animal

like two or three metres long,

so quite a big animal. And here

is an arm, hand, you see here...

dark filamentous structures...

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