19x07 - Triumph of Life: The Four Billion Year w*r

[bunniefuu]

Narrator:
Our planet is alive.

From the shores of Antarctica

to the plains of Africa

it's a world of great beauty
and stunning diversity.

But there is also a dark side.

Life is a w*r filled with
predation
...

rivalry...

and brutality.

But what created
this great drama called life

with its beauty
and its violence?

Breakthroughs in our
understanding of evolution

can now explain
how animal life arose

how it fought to survive
in the ancient past...

and still struggles today.

We now know how behavior
has been shaped by conflict...

and battles for mates...

by predators chasing prey...

through the tensions
in family life...

and by mindgames of intelligence.

We share the earth

of life's four-billion-year
w*r for survival.

The astounding variety of
winners in this ancient struggle

is the triumph of life.

NARRATOR:
A tropical shore,


Life has already existed for
more than three billion years.

The struggle to survive
continues.

Trudontid dinosaurs scavenge
the beaches.

Primitive seabirds return
from a hard day's fishing.

Below the waves, turtles
navigate dangerous waters.

Pliosaurs, huge predatory
reptiles, patrol the coast.

The fastest and most alert
survive.

Like all living things, they
fight to continue their lives

and are compelled to nest,
despite the dangers.

In the ancient battle
for survival

there have always been
winners and losers--

those that live
and those that die.

But dinosaurs, not turtles,
were doomed.

Today, only fossil bones testify
to the dinosaurs' ancient rule.

But life itself survived.

Turtles still hatch
on tropical beaches.

The world has changed
in 65 million years.

But the fight to survive
remains the same.

Many set out, but not all
will reach the sea.

Today's predators are waiting.

But they must run the gauntlet.

The race of their lives is on.

Life's path is full of obstacles

the journey always a struggle.

Survival odds are not random.

Each individual is a unique
product of its parents

and some have
the edge on others.

Moving swiftly in company
is safest.

Getting left behind or lost can be fatal.

While the weak succumb,
the strong struggle on.

Vultures take a heavy toll
on both.

Frigate birds now launch
aerial attacks.

Stragglers fall prey
to forest mammals

coatis and coyotes.

While the race
for the sea continues

one hatchling heads inland.

But this is no place
for a sea turtle.

For other creatures

the land has long provided
huge opportunities.

Myriad animals have escaped
the sea

and now carve out a living here.

Crocodiles have barely changed
since the age of dinosaurs

while birds have taken
many forms.

Mammals have also diversified
in body and behavior.

All living things are
triumphant veterans

of the four-billion-year w*r
called evolution

which has raged
since life first appeared.

Survival skills stay sharp

as they are tested anew
every moment of every day.

The cast of life's drama
is never fixed

and changes over time
as the victorious prevail.

The rules of the w*r are harsh.

Some individuals fail;
others triumph.

Only winners emerging
from the battleground of life

carry their family line
forward through time.

Despite the losses

some youngsters do make it
through the ranks of predators

which have gorged
until they can eat no more.

They now face life's
continuing challenge.

Those fittest
for the rigors ahead

may one day return
to breed themselves.

As the secrets
of each generation's success

are passed on, life evolves.

But clues
to life's shared ancestry

remain hidden
within every animal.

Skeletons reveal
remarkable similarities.

Bony fingers, limbs and
backbones, though subtly changed

are recognizable
in very different vertebrates.

Birds, whales and turtles
are far more alike

than they appear on the surface.

Each living form began
the journey that shaped it

way back in the past.

A turtle about to hatch
is clearly a turtle

with an obvious shell
and flippers.

A week or so earlier, these
features are less distinct.

A young embryo could be
almost any vertebrate

with spine, eyes
and four stubby limbs.

Beyond that, it's more fishlike

then just a mass
of dividing cells.

Finally, it's a single cell

but one containing the complete
blueprint for a turtle.

At the heart of the cell
lie the chromosomes...

and within them lies
the key to life itself

the most incredible substance
on earth

a unique molecule
in the shape of a double helix:

DNA.

Evolution is driven
by the way DNA copies itself

with near-perfect accuracy
and the information it contains.

Its genes shapes
life's varied patterns.

African hunting dogs
are distinct

from other kinds of dog

and individuals differ
from each other in many ways

including the unique markings
on each dog's coat.

They get their looks from their
parents, through their genes

but they also inherit much more.

Even the urge to hunt,
vital to their survival

is built into them from birth.

Only good hunters live to breed.

A pack has just
one breeding male

and his distinctive white tail

is mirrored in some
of his pups back at the den.

Not all look the same

since half their genes come
from their darker mother.

With a mix of genes
from two successful parents

they've a chance
to grow up strong

and to continue
their family line.

Genes shape every detail
of animal form.

Some have brought
recent innovations

but many originated
way back in time

and have flowed through
countless generations

of triumphant life.

But how did life begin?

What kind of creatures were the
ancestors of those alive today?

And how did the first genes, the
original threads of life, arise?

Primeval earth,
four billion years ago.

The toxic air was
devoid of oxygen.

Molten lava spewed
into a noxious sea.

And yet these were
the perfect conditions

for the building blocks
of life to form.

Such foul waters may have been
the crucibles of creation.

Chemicals rained in

and ultraviolet radiation
and lightning bombarded them.

An organic soup
gradually formed.

All was chaos, but order and
complexity somehow emerged.

A very special molecule with
an elegant spiral shape arose.

It alone copied itself faster
than it was destroyed

and multiplied.

This renewal was
the origin of life

and once it found protection
inside cell walls

life was set
to transform the planet.

When cells first trapped
the sun's energy


life began to blossom.

The oceans teemed
with simple plants

and mats of them
layered with sediment

built the world's first living
monuments-- stromatolites.

For over a billion years,
these three-foot-high mounds

were the pinnacles
of life's progress

but the Earth would be
transformed by their waste--

oxygen.

This new gas,
at first toxic to all life

gave rise to the ozone layer.

Shielded for the first time

from the sun's damaging
ultraviolet rays

life now made huge advances.

Plants, which had produced
oxygen in the first place

now came under threat
from primitive animals

that thrived on oxygen
and consumed them.

Amoebae engulfed plants.

Ciliates wafted them inside.

Two billion years ago

single-celled animals first did
what grazing mammals do now.

They used oxygen
to burn up plant food.

But how did
the spectacle of today

arise from such simple origins?

Progress came
when identical cells

teamed up to form co-operative bodies.

Then life really moved on
as cells specialized.

In jellyfish, some gave propulsion, others caught food.

Multicelled life
was now taking shape.

The advance was driven
by genes deep within.

A recent breakthrough

in understanding
how genes organize bodies

has shed new light on the
evolution of complex animals.

As embryos develop, some genes
control which cells do what.

It was the emergence
of these special genes

which organize bodies
into segments

with head ends and tail ends

that allowed life to take off
like never before.



life exploded into a multitude
of new, complex forms.

Many of those classic designs
survive today.

Segmented worms marched
over the seabed.

Life began to move
in more elaborate ways.

New, strangely shaped
animals appeared

encased in tough skeletons
with flexible joints.

The ancestors of sea spiders and
crustaceans were on the move.

Genes that built better eyes and
successful body shapes survived.

The pace of life increased

and new dynamic breeds of animal
preyed on one another.

Defense became vital

and armor plating
and spines proliferated.

Predatory worms
could be defeated

by tough shells
and escape maneuvers.

With genes shaping life like never before

all the basic animal groups
alive today emerged

in just 50 million years.

The previous three billion
had led

to nothing more complex
than jellyfish.

Life was also threatened
by the first large predator.

More than three feet long

Anomalocariswas the scourge
of the ancient seas.

But the big predator's
days were numbered

for a little creature
had evolved

whose line
would take over the world.

Pikaia gently filtered
food from water

as lancelets still do today.

What made Pikaia special

and ancestral
to our own vertebrate line

was its spine of cartilage
supporting its muscles.

This light, strong design
allowed speedy escapes.

But the ancient seas were still
dominated by invertebrates.

Their heavily armed hordes were
the top predators and scavengers

for another 100 million years.

Today's crustaceans reflect
that ancient armored world.

But the invertebrates are not
the force they once were.

Alongside these
hardened battlers

the vertebrates survived,
and one line evolved into fish.

They had no jaws
like today's lampreys

but compared
to most invertebrates

they had better eyesight
and sharper brains.

When it came to alertness
and reaction speed

the invertebrates were beaten.

Fish became faster and sleeker,
and far more numerous.

They developed a bony spine,
and crucially, toothy jaws.

The sea became a much
more dangerous place.

While the oceans
were full of life

the virgin land beyond the sea
lay empty.

But 450 million years ago

things were about to change.

Life invaded from the sea.

These strange creatures
are horseshoe crabs

ancient relatives of spiders.

To this day they emerge
on just a few tides a year

as their ancestors have done for
hundreds of millions of years.

They come to mate
at the edge of the sea.

Females burrow into the sand
and lay their eggs

beyond the reach,
of the oceans hungry hordes.

Once, they had the beaches
to themselves

but today,
flocks of birds descend.

Gulls gorge on eggs
exposed by the waves...

and vast numbers of shore birds
join this annual feast.

Ancient life and modern life
now converge

as horseshoe crabs
and birds fight

the ongoing battle
for survival.

Flipped over by waves,
some crabs are stranded.

They soon die
as their gills dry out.

But most live on.

Horseshoe crabs
have barely changed

in hundreds of millions of years

and continue
a successful way of life.

Strong skeletons allow them
to venture briefly onto land

but they remain
creatures of the sea.

But such pioneers were
just the first wave of life

to reach the land.

By 400 million years ago

much of the earth
was cloaked in green.

Plants had colonized fresh
waters and spread onto land.

Once they were established,
animals soon followed.

Centipedes were among
the first land creatures.

They developed simple lungs

and skin
that kept vital water in.

Scorpions, cousins
of the horseshoe crabs

also made an early move
onto land.

Their line
of eight-legged predators

has spread far and wide
since then.

The invertebrates were
the first animals ashore

but others were not far behind.

Fish penetrated weed-choked lagoons.

Using bony fins

they forced their way through
the tangles to stalk prey.

As competition increased

fish sought new pastures
to hunt in.

Fins became more
and more like legs.

The vertebrates were on
the verge of a breakthrough.

The first amphibians
emerged from the swamp

some 370 million years ago.

Their soft, moist skins
absorbed some oxygen

and simple lungs allowed them
to breathe air.

The exertion of hauling
themselves over land

required plenty of fuel.

But the land
was now crawling with life.

The first flightless insects
made easy prey.

Despite delicate skin

many amphibians came to live on
land as the feeding was so good

but they were confined
to damp places.

The insects went much further.



some forms underwent
a remarkable change.

Under the control of new genes

they transformed into
very different creatures.

They grew wings.

Life was about
to conquer the air

as well as the land.

The power of flight gave insects
a huge advantage.

They now number more than half

of all kinds of animal
on earth today

and they've reached almost
every corner of the planet.

They have invaded some
of the driest places on earth.

Ants are by far the most
numerous insects of all

and their social habits

have helped them to succeed
around the world.

But here, they are not alone.

Reptiles evolved from amphibians

but with a tougher,
waterproof skin--

ventured where amphibians
could not go.

The skin of horned lizards can
even resist attack by ants...

at least most of the time.

Reptiles also pioneered
another survival strategy:

Waterproof eggs allowed them
to breed in dry places.

Developing young were now bathed

in a miniature ocean
within the eggs.

The reptiles were on the verge of global domination.

One thing held them back:

With their skin now
water- and airtight

breathing became a problem.

Lizards breathe as their chests
expand and contract

but because of how they walk

they often have to hold
their breath.

Their sprawling gait,
inherited from ancestral fish

forces their chests to flex
as they walk.

Their lungs can't expand
to draw in air

and lizards easily
become breathless.

The ancestors
of the crocodiles, though

developed far more stamina.

By standing up on their legs

the crocodile line
began to walk tall.

No longer swaying
from side to side

these high-stepping reptiles

breathed easily as they strolled
relentlessly over the land.

And more than just walking,
these reptiles could sprint.

Today, the crocodiles
have returned to the water

and only rarely trek overland.

But 200 million years ago

the small steps
their ancestors took

led to a giant leap forward.

An athletic line of dinosaurs
came to tyrannize the world.

But the future
belonged to mammals

living quietly
in the shadow of the dinosaurs.



the world suffered
a massive upheaval.

All the great dinosaurs
disappeared.

But many creatures survived,
including the mammals.

The earliest were small
and furry

quite like todays tree shrews.

They had evolved from reptiles

whose scales became modified
into hair.

Unlike the dinosaurs

they survived
a cooling of the climate

and dinosaur doom led
to mammalian triumph.

The mammals also had great
strength in their family life.

Mothers reared their young
by providing milk.

In the void left
by the dinosaurs

the mammals stepped into a world
of new opportunities.

Many teamed up for survival

and came to live
in ever bigger families.

This successful
but complex way of living

led to higher intelligence.

In a dazzling range of forms
around the world

the mammals have followed
in the dinosaurs' footsteps.

They have taken over the roles
of powerful predators...

resourceful scavengers...

and grazers.

And they've ventured into
the world's harshest regions.

They still share
an ancient need--

water, where life itself
was born.

A water hole is a meeting place
for many mammals.

Their varied forms reflect both
their different ways of life

and the long evolutionary w*r

their forebears fought
to survive.

The battle to live
has molded mammals

into a huge variety
of shapes and sizes.

Some now need to be wary
of others.

Mammals have taken center stage

but have the dinosaurs
all disappeared?

Perhaps not entirely.

Birds are really
feathered dinosaurs.

One line of small, fast-moving

and, most likely, warm-blooded
dinosaurs evolved into birds.

Birds have become
great successes

thanks to their feathers.

As well as insulating them
from heat and cold

feathers gave birds
a further power...

a power that made life much
harder for their predators.

Flight.

Birds have conquered the air

just as mammals have mastered
the land.

The vertebrates have come
a long way

since their lowly origns in the sea.

Evolution's products
might seem perfect

but the process never ceases.

Where opportunities arise,
further change can always occur.

On the Galapagos Islands,
a variety of creatures

have returned to the cradle
of their ancestors--

the sea.

Marine iguaas evolved
from land lizards

that found the best
feeding on the seashore.

Many would have been washed in.

Those that swam
survived drowning

and today,
their descendants dive in

to reach the rewards below.

These bizarre reptiles, remolded
in form and action by evolution

swim daily out to sea.

Here, by harvesting
the choicest seaweed

they have carved out
a unique way of life.

Fish have lured other animals
to the sea.

Galapagos commarants evolved from flying birds

but their wings have been
shrinking in to feeble vestiges.

They're now grounded, but
the sea provides their living.

Penguins also gave up flight
further back in time

and now have flippers where
their ancestors had wings.

Sea lions, too, evolved
from land creatures

and like all sea mammals,
they must still breathe air

even when asleep in a rock pool.

All these creatures
have returned to the water

and have once more
mastered the ocean.

These mammals and birds have
developed the speed and skills

to hunt the sea's abundant fish.

In the battle for survival

evolution constantly reshapes
life to seize opportunities

wherever they arise.

Today, a sleek swimming mammal
competes for fish

with a supreme aerial master.

Sea lion and frigate bird--

winning designs
evolved from reptiles

and born of the battle for life.

Even at the ends of the earth,
life has found a way to triumph.

Wherever animals are found

they are molded for survival
by the rigors they confront.

King penguins struggle ashore
from Antarctic waters.

Conditions here are harsh

but vibrant life carpets
the frozen land.

Despite all adversities,
countless new lives

continue the battle
for survival.

The young carry the genes
of sucessful parents

forward through time.

Their lives, and their genes,
will be tested to the limits.

Our world is filled
with triumphant survivors

of evolution's
four-billion-year w*r.

Life's struggle continues
to shape everything that lives.