David Attenborough's Conquest of the Skies 3D

---

We human beings are

very latecomers to the skies,

and although we might think

that we're now pretty good at it,

the natural world, with the help of

several million years of evolution,

has produced a dazzling range

of aeronauts whose talents

are far beyond ours.

The story of how animals managed

to colonise the air is truly astonishing.

First into the skies were insects.

They initially had two pairs of wings

which in due course,

were modified in many different ways.

But after having had the skies to

themselves for about 100 million years,

a new group of animals took to the air:

Vertebrates, creatures with backbones.

They faced a different challenge,

for their bodies

were much bigger and heavier.

But eventually they evolved

several ways of solving that problem.

We will travel the globe

to trace the details

of the extraordinary skills,

of the backbone flyers.

This is Borneo.

And here there are still

great tracts of pristine rainforest,

forest that is wonderfully rich

in animals of all kinds.

I am being winched-up

into one of the tallest trees here,

in search of a creature

that can give us a hint,

of how backboned animals

first took to the air.

Hidden among these leaves, of this fern,

high up here, in the canopy,

is a very remarkable, little frog.

It's a Harlequin Tree Frog,

and it's a very, very good climber.

It spends most of its life up here,

clambering around in the branches.

Here it's away from

the numerous predators there are

that might attack it

down on the forest floor.

But if in fact, a predator

were able to get up here, to hunt it,

a snake perhaps, well the Tree Frog

has a remarkable trick for defence:

It glides.

It has membranes between

greatly elongated toes,

so that each foot becomes a parachute

which slows the frog's descent,

and so enables it to make

a relatively safe landing.

The vertebrates made their first foreys

into the air around 260 million years ago,

and it's very likely that some

of these pioneers used skinny membranes

to control their falls, in much the

same way as this little frog does.

It has to be said, that it's not

a very good aerial navigator,

it seems as though it just jumps

and hopes for the best.

But there are animals up here,

that glide around from tree to tree,

which are very good navigators indeed,

so good in fact, that they can go

from one tree to another,

and never go down to the ground

in their entire lives.

One of them is

a little lizard called Draco.

Each male has his own little territory

in the branches,

and tries to attract females

and warn off rivals,

by flashing his dewlap.

He also spread coloured flaps

of skin from his flanks,

that when fully extended,

do more or less the same thing.

But there are predators

among the branches.

Snakes also live up here,

and they hunt lizards.

But Draco's side flaps

now serve another purpose.

He uses them to glide, by hidging forward

his specially elongated ribs.

And he is so skilled in the air,

that he can steer and land

on the trunk of his choice.

So, if you live up in the branches,

it's less laborious,

and indeed safer, to travel by air,

than to come down to the ground.

But if you want to be a true flyer,

you have to be able to fly

not only downwards but upwards,

you have to have powered flight.

This is another reptile,

and one with even

greater flying abilities

than that little gliding lizard.

Today, sadly, it's extinct.

This is Dimorphodon.

We can deduce from its fossils

that it had the muscles

needed to beat its wings,

and computer imagery can show

us what it must have looked like.

Dimorphodon was one

of the first large animals

ever to travel by air,

200 million years ago.

It belonged to a group called

the Pterosaurs, the winged reptiles.

It was probably a forest dweller

and a descendant of a tree living glider.

This gliding ancestor might have

had wings like those of Draco's

that were made of skin,

and perhaps extended

from its fingers down to its ankles.

But Pterosaurs had evolved larger wings

with a hugely elongated fourth finger.

The wing membrane

was strengthened internally,

by thin rods of a stiffer tissue.

They were muscles fibres too,

that enabled it to modify

its contours as it flew.

Looking at the wings in section,

reveals a secret of their efficiency.

They have a rounded front edge

and a sharp back edge,

a shape known as an aerofoil.

It works by forcing the air

flowing above the wing, to speed up.

This faster air has a lower pressure,

and the wing is sucked upwards.

The larger the surface area of the wing,

the greater lift it can produce.

So it seem certain that Pterosaurs

were very competent flyers.

And judging from their teeth,

it seems likely, that many fed

on the great variety of insects

that had preceded them into the air.

Insects have had the skies to themselves

for around 100 million years.

Now, bigger creatures had arrived.

Reptiles.

The Pterosaur design for flight

proved hugely successful.

They used their new powers

to spread beyond the forests,

and colonize whole new environments.

A great number of them

lived and fed near water.

We know this because

fossils of many species

occur in rocks that were once mud

at the bottom of lakes and shallow seas.

This one shows the skeleton of an animal

that 150 million years ago,

fell to the bottom of a shallow lagoon.

Rate this script:0.0 / 0 votes