NOVA

Over four billion years in the making.

An island adrift in southern seas.

It's Australia, the giant Down Under.

A young nation, with all the gifts of the modern age.

But move beyond the cities and an ancient land awaits...

One nearly as old as the Earth itself.

Australia is a puzzle put together in prehistoric times.

And the clues that unlock the mystery can be found

scattered across Australia's sunburnt face.

I'm Richard Smith, and this is an amazing country.

I'll show you that every rock has a history,

every creature a tale of survival against the odds.

Join me on an epic journey across a mighty continent,

and far back in time.

Of all continents on Earth,

none preserve the great saga of our planet

and the evolution of life quite like this one.

Nowhere else can you so simply jump in a car

and travel back to the dawn of time.

In this episode...

The worlabove water has sat silent and lifeless.

But now, armies storm the beaches

and biology conquers the world.

It's the battle for life on Earth.

The struggle for legs and lungs, sunlight and shelter,

even the quest for sex.

From Australia's ancient stones comes the story of our world.

"Australia's First Four Billion Years: Life Explodes,"

right now on NOVA.

Majolf Australia seems is pra little tired and worn,

it's because she's seen a lot happen

over the course of her long life.

In the last episode, our journey down the road of time

began with the Earth's fiery birth

four-and-a-half billion years ago.

We passed the first fumbles of life

in the waters skirting Australia's ancient shoreline.

Along the way,

we've seen the planet change from poisonous to pleasant,

and the first animals begin to swim the seas.

Yet save for a thin smear of slime and bacteria

along the soggiest of margins,

all the continents themselves had lain bare

for over four billion years.

In terms of the lifetime of a continent,

Australia and the world ound it is still an infant,

still attached to its motherland...

the great supercontinent Gondwana...

and still a blank canvas on land.

Your destination is the Paleozoic.

Now with 90% of Earth history behind us,

it's time for conquest.

The tremendous explosion of life

that began in the oceans of the Cambrian

was still going strong at the dawn of the Ordovician,

the second of the six great periods

that make up the Paleozoic.

And it was in Ordovician oceans

that a second wave of animal experimentation began as well,

one that ultimately would lead

to the first Australians coming ashore.

With the seas now crowded with life,

the first tentative footsteps onto land were not far away.

Now at the time,

Australia was just one of an exotic collection of lands,

including India, Africa, South America and Antarctica,

that today we call the supercontinent Gondwana.

Australia's position was just about here, right at the tip,

just north of the equator, and mostly underwater.

Oceans were rising around the planet,

and seawater flooded in across parts of Central Australia.

At the time, the sea of sand we know today as the Simpson Desert

was slap bang in the middle of the Larapinta Seaway,

a tongue of warm ocean water

that licked right across the country.

Back then, this bouncy drive

would have been a bumpy boat crossing.

As the rising waters swept in,

they carried a rich bloom of plankton...

food for some of the earliest fish to swim in the sea.

And they swam right here, right above me.

The last vestiges of the old Larapinta seafloor lie tumbling

from the top of the mesa-shaped hills of the Simpson Desert.

Even in the best of seasons like this,

the Simpson is a harsh, unforgiving landscape.

Now you probably wouldn't expect

to find the world's earliest fish in the dead center

of the driest inhabited continent on the planet today.

But it was on the side of this hill in the Simpson Desert

where the fossil of Arandaspis lay waiting to be discovered.

We only know Arandaspis from the bony head plates

and body scales it left behind...

enough to tell that this was a fish

with a simple tail and no real fins.

Nor did fish like Arandaspis have jaws, or even teeth.

They probably just slurped in

whatever morsels they could find.

But don't underestimate the significance of this fish.

This was an animal with a backbone.

It's one of the first vertebrates,

so we can all trace our ancestry back to an animal like this.

But giant invertebrates ruled these Ordovician seas,

and to them, Arandaspis was just a bite-sized snack.

While the first fish took to swimming out of danger,

their invertebte foes

would soon be flexing their leg muscles in a different way.

Time to put the foot down

and head for the seaside in the Silurian.

On a remote stretch of the Western Australian coast,

the 21st-century Indian Ocean

eats away at an ancient Silurian shoreline.

Wind and water have exposed the burrows of long-gone animals

in the sandy coastal cliffs.

The original inhabitants of the burrows remain a mystery,

but not the predators attracted by such rich pickings

along the prehistoric shoreline.

Clues to their identity are revealed in the rocks

of nearby Murchison Gorge.

Here the river has sliced deep into the Silurian past.

The Murchison Gorg back in the Silurian

wasn't a gorge at all, of course.

It was a vast estuarine flood plain

with rivers winding down from the hills in the distance

carrying sand into the sea.

But for the first time in the history of the planet,

those Silurian shorelines down there were alive

with animal activity.

This may not have been a good time

to take the kids to the beach.

Armies of sea scorpions were massing in the shallows.

Known to paleontologists as Eurypterids,

some of these intimidating arthropods

grew as long as a man is tall.

And they bristled with armored legs and fearsome claws.

Far less threatening was this bloke.

Kalbarria was probably an ancestor of modern crustaceans

and grew about as long as a king prawn.

Whether in search of food, a safe place to mate

or simply to avoid the nasty neighbors,

Kalbarria clambered ashore...

and left clear imprints of its many tiny feet in the rocks.

A desceninto Murchison Gorge

takes you back to those ancient Silurian shorelines.

Down here, it soon becomes clear that the sea scorpions

followed Kalbarria ashore.

This is what we call "Track Central."

I can see why. Yeah.

There were tracks everywhere.

This is probably the best site in the park

to look at these eurypterid tracks.

Our animal's come through here.

So, in shallow water.

Shallow water.

Been slipping and sliding as it comes around the corner.

That's exactly right. But here.

I mean I can see,

clearly there's this kind of sloppy looking track here,

but once you come over here,

you start seeing really discrete footprints.

Clear, graphic demonstration of a creature

walking out of the water and onto dry land.

And where we are here in the depth of the gorge,

we're in the oldest of the Silurian sediments in this area.

Quite an historic little spot you've gohere.

Very, very.

These trackways offer

some of the oldest evidence for animals on land.

And even though these formidable beasts

could not stray far from the water's edge,

a beachhead had been established.

So this seems to be

how the animal invasion of the land began:

with a scary assortment of arthropods with attitude

slinking and scuttling ashore

onto the wet sands of a new frontier.

But this wasn't just a continent to exploit;

there was a whole planet for the taking.

Waiting beyond the breakers

were all the wide, brown lands of Earth.

Australia, already under animal assault,

found itself center stage for the waves of invasion

and conquest that would follow.

But animals were not going to get far inland

without help from plants.

They, too, came out of the sea, first as slime,

then as low, spreading things that clung to dampness.

Seaweeds captured the shoreline,

then tiny forests of lichens, liverworts and mosses

pioneered the move inland.

Today, we take for granted the plants around us.

It's their oxygen we breathe, their food we eat.

But the land can be a tough, dry place to live,

and any plant going to make it big out here

needed a thick skin and a little internal fortitude.

Just such a plant first took root somewhere around here.

If you thought that this was

just another ordinary roadside cutting

on a pretty but ordinary country road,

well, of course, you'd be dead wrong.

It was here nearea in Victoria that fossils