Original subtitles

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A life has expired.

Most species that ever existed on the Earth,

maybe even 99 percent of them, are extinct.

This kangaroo is no longer of this earth.

Oftentimes, death comes at the most unexpected hour.

Of course it does remove sometimes, whole groups.

But, it is also a creative force.

Five mass extinctions have occurred during the

4-billion-year history of life on Earth.

Species died off because they were weak,

or because they could not adapt to changes

in the environment.

Some succumbed to sudden disasters which had

never before occurred.

But the extinction of one species was an

opportunity for another.

This is the story of the destruction and creation

brought on by mass extinctions.

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We are on our way in search of Earth's first animals.

This is the Flinders Ranges, a mountain range

in Southern Australia.

There is no human presence here.

Instead, the area is populated by wild animals.

Dr. Jim Gehling hangs precariously from a cliff

looking for something.

He is a paleontologist from South Australian Museum

who has been researching the fossils found

here for the past 30 years.

He finally discovers something.

This is the fossil of a creature belonging

to the Ediacara biota.

Before the time of the Ediacaran fossils,

we only had microscopic fossils.

For 3 billion years, nothing that you could see with the

naked eye, and then, very rapidly,

we see these strange creatures appear in the fossil record.

These creatures which look like leaves might have been

rooted to the ocean floor.

They swayed in the current while subsisting on the

nutrients floating in the water.

Although some had heads and tails,

many of the creatures seem to have no means of locomotion.

Dickinsonia is the most common species

amongst the Ediacara biota.

They were flat, creased creatures which had neither

a mouth nor muscles.

The smallest were as tiny as a grain of rice,

while the largest creatures grew as large as a cushion.

None of them so much as resembles the creatures

living on Earth today.

So, what was the environment they lived in like?

They lived in the sea 600 million years ago.

Species of the Ediacara biota lived in all

the oceans of the world.

Most of the biota lived stationary lives,

secured to the ocean floor.

And they subsisted on the plankton

floating around in the water.

While there was a diverse array of these creatures,

they were completely different from the creatures

living on earth today.

Within the Ediacara biota, we have some

truly weird creatures.

And we see nothing like that today.

So we assume that these things did not survive

into the Cambrian period.

They were only known in the Ediacaran period.

Although they were the first animals to inhabit the oceans

some 6 hundred million years ago,

they all became extinct before the Cambrian period arrived.

Next, we set out for a place where clues to their mass

extinction can be found.

This is another area of the Flinders Ranges where fossils

from the Ediacara biota have been found.

These slanting geological strata record the

history of life on Earth.

These sandstone rocks are like pages in the geological

history of the evolution of life.

On my right, we have the sandstones of the Ediacaran

period with the soft-bodied fossils of the Ediacara biota.

And here I stand on a boundary.

We move across a most important boundary.

The base of the Cambrian and the beginning of the

Cambrian explosion of life.

This is a geological stratum from the Cambrian period.

Although they merely look like fissures in the rock,

the cracks are evidence that a new page had been turned

in the history of evolution.

This is a fossil from the Ediacaran period.

They are trails left by a creature that crawled

around on the ocean floor.

They are noticeably different from the trace fossils from

the Cambrian period.

This difference reflects the end of one period and

the beginning of another.

Once animals evolved that could eat other soft-bodied

animals, then, the only animals that could survive

could either swim fast, make a protective cover or a shell,

or if they had neither of those abilities,

they had the muscles to dig into the seafloor and hide there.

As it turns out, the fissures in the rock are actually

fossilized holes that creatures dug into the sand in

order to hide from predators.

Here in the Flinders Ranges, there is a borderline between

the Ediacaran and Cambrian periods.

There is another Cambrian fossil on this rock that

Dr. Gehling is kneeling on.

This creature had a hard covering around its body.

In this way, life evolved in order to adjust to the

changing environment.

500 million years ago, Earth's oceans were teeming with

creatures in a wide array of shapes and sizes.

But something changed in the relationship

between the creatures.

Suddenly, they realized that there was food to be had

besides the plankton floating in the water.

They could prey on each other.

In this way, animals began to prey and be preyed upon.

And it was around this time that hard protective shells

and muscles appeared.

So, what effect did such a change have on the creatures

of the Ediacara biota?

This is a fossil of two Dickinsonia.

They are spaced apart, as if uninterested in each other.

Animals from the Ediacara biota did not prey on other animals.

Instead, they subsisted on nutrients floating in the sea.

But the change in the environment

proved to be fatal to them.

An animal which was soft-bodied like Dickinsonia,

a big sheet of meat lying on the sea floor,

it's dinner waiting for an animal that could eat it.

In the end, the Ediacara biota became extinct.

While these once microscopic creatures managed to grow

significantly in size, they could not adjust to the

appearance of predators.

That's why they are called 'a failed experiment'.

This rocky and barren terrain was once the stage for the

rise and fall of Earth's first animals.

They are testament to the transient nature of life.

So, were the species that adjusted more actively to this

change able to avoid extinction?

The trilobite which first appeared during the Cambrian

period and survived for 300 million years could be called

'a witness of Evolution.'

These creatures were able to survive and flourish through

two mass extinctions thanks to their quick and

varied adaptations to changes in the Earth's environment.

Trilobites are capable of very rapid evolution and this

applied even towards the end of their history.

Some of the trilobites that went out at the end of the

Ordovician had been around in the oceans

since the Cambrian period.

So one could say that they were themselves already

tremendous survivors.

Trilobite fossils are extremely common.

When one takes into account that the average species lasts

for 5 million years before it goes extinct, the

trilobite's 300 million years of survival is an amazing feat.

As their name indicates, trilobites can be

divided into 3 sections.

They wore a hard shell over their backs for protection

from hungry predators.

Also, they were equipped with jointed appendages which

allowed them to move very quickly.

Even the earliest of their species had

well-developed eyes.

And they came in a wide variety of sizes,

with the smallest being as small as a fingernail and the

largest being as large as a cushion.

These creatures were most likely heavily preyed on in the seas.

Some fossilized trilobites have chunks bitten out of them.

So, how did they protect themselves?

Many of the trilobites that survived the End-Ordovician

extinction event were capable of rolling up.

This shows you how beautifully adapted they are, the head and

the tail actually lock together in some of these forms.

So if you're like that, you're protected from the action

of an attacking predator.

Its soft underbelly was the most vulnerable to attack.

But by rolling up in this manner,

the trilobite could keep safe from predators.

This was the first feature the trilobite evolved in order to

survive in the predatory waters of the ancient seas.

But that wasn't all.

This is the head of the trilobite as seen from above.

This trilobite has a pair of compound eyes.

It probably saw the world through thousands of tiny

hexagonal windowpanes.

The waters that the trilobite lived in were full of

predators hungry for a meal.

So it was extremely advantageous to be able to

detect the movements of potential predators and prey.

They had really quite sophisticated visual systems,

even the early ones.

But some of the later ones evolved really sophisticated.

Under a microscope, the eyes of the trilobite are as

intricate and beautiful as a finely-carved sculpture.

The eyes were so advanced that they could focus on objects.

This was another adjustment necessary for survival.

But the evolution of the trilobite did not stop here.

It protected itself using fearsome spines and hard armor.

Sometimes, the protective spines were so large and

elaborate that they looked lugubrious.

But even these were attempts to adjust to the hostile

environment surrounding them.

So, were these heavily armored creatures the last to survive?

Professor Suzuki Yutaro of Shizuoka University,

an expert on trilobites, offers us an entirely

unexpected answer.

The trilobite that managed to survive as its more elaborately

armed kin slowly died off was in fact quite ordinary.

This tiny 4-centimeter-long trilobite was the last to

remain until the species died off completely.

Instead of specifically adapting itself to various

conditions around it, the trilobite proliferated quickly

thanks to its small size, and was able to survive longer

than its more elaborately designed cousins.

Earth changed constantly during the 300 million years

of the trilobite's existence, but the creature was able to

adapt to these changes and survive.

Nevertheless, there were some changes that were all but

impossible to prepare for.

It's just bad luck if you're in the wrong place at the

wrong time, and certainly at the end of the Permian,

as much as 90 percent of species went extinct.

So this is almost all of life and is probably

more sensible to think about the 10 percent who

survived as just being lucky.

Next, let us investigate an incident that occurred at the

end of the Permian period 250 million years ago.

This is a geological stratum from the Permian period

located in Meishan, in Zhejiang Province, China.

This band of dark rock indicates the passage from one

geological period to another.

The slanted layers of rock are marked with

letters and numbers.

They indicate the era when the layer formed.

It is here that traces of Earth's most devastating mass

extinction can be found.

These rocky mountains harbor clues of a chilling past.

So, what exactly happened on Earth 250 million years ago?

Around the end of the Permian period,

great cascades of lava began to gush out of a volcano near

what is modern-day Siberia.

The lava flow covered the Ural Mountains and Lake Baikal,

and reached all the way to Kazakhstan in the south.

This endless river of lava solidified to create

a layer 20 meters thick.

The lava from this greatest volcanic eruption in Earth's

history covered an area roughly equal to

the American continent.

Creatures were helpless in front of this massive disaster

whose scale was unprecedented.

This disaster triggered even more disasters.

The smoke and ash which gushed out with the lava

filled Earth's atmosphere.

The planet's temperature rose by 6 degrees Celsius due to

the greenhouse effect brought on by carbon dioxide.

Sulfur dioxide and chlorine mixed with the air,

causing acid rain to drench the earth and make its soil

uninhabitable to any form of plant life.

Also, with the balance of the atmosphere broken,

the solid methane in the oceans began to melt,

causing earth's ecosystem to spiral into chaos.

This was the greatest mass extinction in the

history of life, with 97 percent of aquatic animals

succumbing to extinction and 70 percent of terrestrial

vertebrates dying off.

When natural disaster rears its ugly head,

no creature can withstand it.

But, it is only a matter of time before life takes root

once more and flourishes.

This was not so with the mass extinction that occurred at

the end of the Permian period.

What was the reason that this extinction event was so much

more devastating than similar events in the past?

Professor David Jablonsky of the University of Chicago is

an internationally-renowned expert on mass extinctions.

We asked him what factor played the biggest role in determining

whether a species would survive a global disaster.

So it's a real difference in being widespread,

having your evolutionary eggs in more than one basket,

as opposed to being concentrated in just one small area.

Even if those lineages are very well adapted to the

conditions before the mass extinction,

unless they're widespread, they're in serious trouble.

Earth's plate shifts endlessly,

moving the continents with it.

Sometimes, the continents become clustered together.

Such was the situation at the end of the Permian period.

In other words, animals were clustered together as well,

leading to a disastrous result.

Broad geographic ranges of entire evolutionary lineages

whether they are found on multiple continents,

seems to control the survival of major evolutionary

lineages, and other features that used to matter go away.

So, that means that the short, sharp,

extinction events have a disproportionate effect on

the evolutionary process.

So, how did life resurface after the demise of

most of Earth's creatures?

First, a single seed must have been carried

onto shore by the waves.

Full of vitality, such seeds became vast plains of grass

and lush forests, creating an environment hospitable to life.

This newly created ecology opened the doorway

for new species, attracting animals such as small

reptiles that fed on plants.

Also, birds flittered in to feed on the berries and

fruits, spreading their seeds even farther.

Sometimes, during the endless evolutionary cycle of life and

death, the fate of life on earth takes an unexpected turn.

This is Gubbio, a town located in Northeastern Italy.

People stroll leisurely amongst medieval buildings.

Past and present coexist in peaceful harmony here.

But in the mountain on the fringes of the town,

there are vestiges of a mass extinction event that took

place 65 million years ago.

This is part of the Apennine Mountains,

which were once the seabed until they rose up around the

time the Mediterranean appeared.

There is a geological stratum from the end of the Cretaceous

period located on the roadside in the Bottaccione Valley.

These slanted geological strata bear the

traces of scientific research.

The strata harbor the secrets of a truly horrific event.

Called the K-T boundary, the K and T stand for the Cretaceous

and Tertiary periods respectively.

This ordinary looking layer of rock drew scientific interest

due to the presence of a rare metal.

The K-T boundary contained 10 times the iridium found in

other geological strata.

Meteorites which fall from the sky often contain metals that

are extremely rare on Earth.

Iridium is one such metal.

Some scientists even claim that all the iridium on Earth

is the result of collisions with asteroids and meteorites.

The iridium concentrations found in Bottaccione Valley are also

traces of an asteroid impact which occurred 65 million

years ago and had a devastating effect on life on Earth.

Let us find out more about this incident.

After the mass extinction that occurred at the end of the

Permian period, the new masters of the

Earth were giant reptiles.

They ruled supreme over land, air and sea,

and were Earth's dominant predators for

nearly 200 million years.

Although the predators' large size was an advantage when

hunting prey, it left them vulnerable to sudden

changes in the environment.

Moreover, there was no way that they could prepare for a

catastrophe caused by an extra-terrestrial event.

This is a crater 1.6 kilometers in diameter and 170

meters deep, located in the middle of the Arizonan desert.

It's the impact site of a meteor that collided with

Earth around 50,000 years ago.

The vertical geological strata are testament to the

awesome power of the impact.

Scientists calculate that the crater was created by a meteor

50 meters in diameter travelling at over 10

kilometers per second.

What would happen if an asteroid 200 times larger

than the meteor that created this crater,

collided with the Earth?

Some 65 million years ago, that is exactly what happened.

The asteroid fell in what is known as Mexico today.

At the time, North and South America were divided by a sea.

Scientists say that the impact was similar to having

Mt. Everest collide with Earth travelling

at the speed of a bullet.

Countless dinosaurs were killed by the great ball of

fire that fell from the sky.

None could prepare for such a cataclysmic disaster.

But the initial impact was just the beginning

of an extended tragedy.

Great plumes of black ash rose up into the sky,

causing acid rain to fall.

And clouds of sulfur dioxide hid the sunlight,

causing the temperature to plummet.

The plants were the first to succumb to the sudden

change in the environment.

But they were quickly followed by plant-eating dinosaurs and

the predators that fed on them.

With the sudden scarcity of food,

the large size of the dinosaurs proved to be a tragic weakness.

But this most recent mass extinction was a blessing in

disguise for one species.

It also was an important event for humankind.

People might tend to think of extinction as a disaster.

Well, it is a disaster for a short time for the organisms

that exist prior to the extinction,

and of course it does remove, sometimes, whole groups.

But it is also a creative force because after the

extinction, ecological opportunities are open.

Niches are vacant for new organisms to move into,

for new adaptations to occur.

65 million years ago, an asteroid which was 10

kilometers in diameter, collided with the Earth.

While the dinosaurs were powerless to avoid the

resulting chaos, Eomaia, the tiny mammal, sought shelter.

Even before the disaster, these tiny creatures only came

out at night in order to avoid the much larger dinosaurs.

They were at the bottom of the food chain.

Years passed by.

And around the time when the effects of the most recent

disaster began to fade, this mammal was preparing to open a

new chapter in the history of life.

Unlike dinosaurs whose large size proved to be a fatal

shortcoming, the tiny, warm-blooded mammals were able

to survive the mass extinction.

Ironically, the tiny size of the creatures,

which was a weakness in the past,

was the factor which allowed it to survive.

And when the predatory dinosaurs became extinct,

it was these mammals that began their dominance of earth.

The mass extinction turned out to be a gift for these small

and frail creatures.

After the demise of the dinosaurs,

the mammals began to spread at a breakneck pace.

Their warm blood helped them adapt to the increasingly

seasonal climate of the Earth.

The mammals took on a diverse array of sizes and shapes,

and each species developed characteristics which helped

it adapt to its new environment.

Mammals whose defining characteristic was the fact

that they gave birth to live young and reared them,

continued to evolve.

Until finally man, the crowning achievement of

mammalian evolution appeared.

So, what effect did man with his hyper-developed brain,

have on the natural environment?

have on the natural environment?

This is Naracoorte Caves National Park in

Southern Australia, which has been designated as

a UNESCO World Heritage.

Professor Gavin Prideux of Flinders University passes a

dark and narrow passageway and climbs down into a cave.

This is Victoria Fossil Cave.

Thought to be a giant sink hole in the past,

the floor of this cave is strewn with countless animal bones.

The fossilized remains of some 45,000

animals are preserved in this cave alone.

One can ascertain from the large size of the bones that

the animals themselves were quite large.

There are remains of a kangaroo that was over two

meters in height as well as bones of a 6 meter long lizard.

So, how did these animals meet their death on this cave

floor, 50 meters below the surface of the earth?

After the animals fall in, they can't escape,

and they either die on impact or they die of thirst

or starvation or injuries.

Their remains get incorporated into the sediments and they

sort of slide down through water and just gravity,

and mixed up also from other animals trampling on top and

that is how we excavate them.

Australia possesses a fascinating ecosystem.

It was originally part of a massive supercontinent called

Gondwana located in the southern hemisphere.

This continent also included Africa,

Antarctica, South America and India.

But 35 million years ago, Australia became separated

from this continent, and became home to a unique ecosystem.

There are many species in Australia that cannot

be found anywhere else.

This is the result of millions of years of isolation.

This is also the case with the animals fossilized

in Victoria Fossil Cave.

For some reason, placental mammals could

not take root in Australia.

Instead, a wide array of marsupials,

that is mammals with pouches, proliferated on the continent.

Such animals include a kangaroo with a much shorter

face than the kangaroos of today.

Thylacoleo carnifex, the marsupial lion which was the

apex predator of the Australian continent.

And Diprotodon, the giant wombat whose massive size can

be gleaned by the size of its enormous jawbones.

So, how were these animals able to grow so large?

A hundred thousand years ago, Earth's climate became

increasingly cold and dry.

And the only plants able to survive in this environment

were nutrient-poor.

In other words, herbivores had to eat large amounts of food

in order to gain the necessary nutrients,

and this resulted in their growing larger in size.

The predators that fed on these herbivores also

had to grow larger in size.

The marsupial lion which was the apex predator in the

Australian ecosystem weighed more than 150 kilograms.

It would hide in the bushes and pounce on prey,

slashing the victim's neck with its large saber teeth.

The largest kangaroo in Earth's history

grew over 2 meters in height.

It fed by picking and feeding on leaves using its front legs.

Diprotodon, an herbivore which weighted 3 tons,

usually lived in herds by the water.

The large size of these animals was the result of

adapting to an environment which was

becoming increasingly barren.

But this adaptation alone proved to be insufficient.

This was because of a new species which hunted and lived

in an entirely different manner.

What was this species which caused the downfall

of these large animals?

One is that they were hunted to extinction by

people when they first arrived in Australia.

People arrived 60, 50-thousand years ago and make the fauna

become extinct after that.

One of the other explanations is that it was the lighting of

fires by people that changed the nature of the vegetation,

wiped out the food plants the mega fauna were adapted to

eating and then they became extinct and then their

predators became extinct.

Even the marsupial lion which once ruled supreme,

was no match for this new species which was

armed with sharp spears.

To man, these giant mammals were merely a rich

source of fat and protein.

The fire that early man used to hunt would spread

uncontrollably, destroying the habitats of these animals.

To make matters worse, the climate changed drastically.

Man coexisted with these giant animals for 20,000 years.

But in the end, the animals fell victim to

man's fire and spears.

Unlike other animals, humans stood and walked upright.

So their hands were free to make the fire and tools with

which to overcome their weaknesses.

Although man's only advantage was his highly developed

brain, he used it to make the tools necessary to hunt and

kill animals much stronger than him.

Man was not an especially vicious or violent animal.

He merely did what he needed in order to survive, and this

brought about the unfortunate demise of other species.

So, was this an unavoidable course in evolutionary history?

Humans used different devices to encourage its own species

to increase and if this has an impact on totally

unrelated species, then so be it.

The whole process of evolution is an all encompassing

complex panorama. that takes advantage of

every conceivable niche and opportunity.

It's the most opportunistic and selfish system that

you can possibly imagine.

Man's tools have become far more advanced,

but even now, he is in constant struggle

with the nature around him.

It is all but impossible to draw the boundary between the

destruction that is necessary for man's survival,

and the destruction wrought by man's unnecessary greed.

All we can be sure of is that if this destruction continues,

man's days on earth will be limited.

Whether man exists or not, life on this planet will go on

as it has even through the 5 mass extinctions

that have come and gone.

We are now back in the Flinders Ranges where earth's

first life forms were born.

Dr. Jim Gehling is investigating something.

It is a trace fossil, a petrified trail that was left

by some unknown creature.

There's no way to know what the creature was

doing or where it was headed.

Was on its way to find food?

It could have been looking for a mate or running

away from a hungry predator.

There is no way to tell.

All we know is that this creature is now extinct.

Maybe 9 out of every 10 of these species went extinct but

the 10%, one in ten, are enough to take that genetic

material into the future.

These may be the ancestors of all modern animals.

The life form which was born 600 million years ago,

grew in size, proliferated and diversified,

only to disappear once more, leaving all but a few traces.

And with its disappearance, it made room for a new generation

of life to take root and flourish.

In this way, the history of life has been an endless cycle

of birth and death, creation and destruction.

Extinction is an end of everything but at the same

time, it is also a beginning of everything.