Original subtitles

Twenty thousand years ago,

the world was in the grip of an ice age.

Much of the northern hemisphere was blanketed by snow

and crushing glaciers, miles thick.

An iced earth.

Great beasts,

some familiar and some strange, lived here.

Adapted for the punishing cold.

This was the world of the mammoths.

Kingdom of the titans.

An age of ice.

These bones belonged to giants,

but unlike dinosaurs, these animals,

shared the planet with humans.

We can only imagine their strange calls

that once haunted the dreams of our ancestors.

What happened to these great beasts that once walked among us?

Why was extinction their fate?

The stories of their lives continue to unfold,

as strange new creatures are uncovered.

In 2007, a reindeer herder in northern Russia

discovered this mummified baby woolly mammoth.

She had been buried and frozen for 42,000 years.

Her skin and organs, some fur and even her eyes are extremely well-preserved.

Her tiny tusks, not yet visible.

Named lyuba,

she is the most intact mammoth ever found.

And a rare window to our frozen past.

Two and a half million years ago, an ice age began with a snowflake.

One of nature's most beautiful creations.

One by one they fell, billions upon billions.

Blanketing the north,

chilling the planet.

The pleistocene epoch, our most recent ice age, was born.

Our story begins near the end of the last ice age,

roughly 20,000 years ago.

It was an environment well suited to giants.

Woolly mammoths.

This icon of the pleistocene spread through Europe, Siberia,

and into northern parts of north America,

roaming grasslands called the mammoth steppe.

It is likely the herds were constantly on the move,

seeking their favorite vegetation.

Individuals eating up to 400 pounds per day.

Similar to her elephant cousins,

baby lyuba would have lived in a family clan of about 10 members,

protected by a dominant female, the matriarch.

Standing up to 10 feet and weighing as much as eight tons,

woolly's huge mass helped them to retain body heat.

Three layers of hair and wool, a layer of insulating fat,

and small fur-lined ears also helped them cope with the cold.

Massive curved tusks, up to 16 feet long,

could be used as plows to reach grass buried under the snow.

The calves were curious and playful, but vulnerable to predators,

and always under the watchful eye of their mother.

Sometimes a male bull would challenge another for dominance of the herd.

A clash of these titans could be a violent affair.

Since the birth of our planet, the climate has been changing,

cycling, temperatures rising and falling.

There have been at least five major ice ages.

Some may have covered the whole planet in ice.

Climate cycles have been fundamentally shaped by variations

in the earth's orbit over time.

These variations alter the way the sun strikes the earth,

and can lead to cooling on the surface.

As the ice caps grow,

they act as a mirror, reflecting more sunlight away from the shining ice,

causing heat to escape from the atmosphere.

So cooling speeds up, then more ice,

more reflection and more cooling.

Greenhouse gases in the atmosphere such as methane and carbon dioxide

counterbalance the cooling, trapping the sun's heat like a greenhouse

around the planet.

Volcanoes can produce these gases naturally.

Plants and trees recycle the gases and keep them in check.

Too much greenhouse gas, and the planet can warm.

Too little, and it cools.

Each of these factors, the earth's orbit,

angle to the sun and atmosphere,

all work together to shape earth's climate.

This is the clockwork of nature.

Even the tiniest variation can tip the scale

with profound consequences.

During our most recent ice age,

glaciers blanketed the north.

But most wildlife lived south of the ice sheets

on vast grassy plains.

The grasslands supported immense herds of grazers.

Like today, there were seasons,

but each was about 16 degrees fahrenheit cooler,

and with so much water locked up in ice,

there was less snowfall on the plains.

Animals we know today,

lived among mammoths, mastodons and big cats.

The plains of ice age Europe, Asia and north America

were like the African serengeti.

And like the serengeti,

where there are grass eaters,

there are meat eaters.

Dire wolves.

These intelligent, social carnivores, lived and hunted in packs.

At up to 150 pounds,

they were more powerfully built than today's gray wolves.

And they were aggressive hunters.

The wolves are not alone.

Sabre-toothed cats smell the fresh kill,

and an opportunity.

With large curved fangs and nearly twice the weight of a modern African lion,

they are the top predator.

During the pleistocene epoch,

so much of the earth's water was frozen into the ice caps,

that sea level dropped by over 300 feet, connecting continents.

Many ice age animals arrived in north America from Siberia,

over this land bridge, called beringia.

But they were not the only ones to discover the passage.

Humans made their way to this vast, untamed continent.

Though not physically equipped for a harsh and bitter climate,

our intelligence, curiosity and language

allowed us to cope with new challenges.

Ice age humans were the first to leave symbolic records of their lives.

Their drawings, mostly found in European caves,

evoke a world of fire and ice,

of mammoths,

bison

and horses.

As the ice age giants disappeared,

the bones they left behind fueled wild and chilling speculation.

Siberians imagined that hulking skeletons rising from melting ice

must belong to giant moles that lived in hell.

A mammoth's skull may have been the inspiration for the cyclops

of Greek mythology.

Even early attempts by scientists to assemble mammoth bones

were often just as wild.

Scientists were equally confounded by massive boulders standing alone.

After centuries of speculation,

geologists determined that the boulders, called "erratics,"

had been carried thousands of miles on rivers of ice,

and left behind when the ice melted.

And the mysterious bones from mythology

belonged to extraordinary animals from that lost world.

One unusual place,

hidden within the ice age scrub lands,

tells an exceptional, though grim, story.

Tar pits.

A columbian mammoth, lured by drinking water, has perished,

likely from dehydration and exposure

after getting trapped in the tar.

Its carcass is of interest to this sabre-toothed cat.

She's hungry.

A mammoth is a temptation worth the risk.

On this day, the tar has claimed another victim.

And the smell of death attracts others.

For forty thousand years, countless predators and prey

were mired in this deathtrap.

Their bones sinking into and preserved by the tarry asphalt.

Bones that continue to be pulled from the la brea tar pits today,

in the heart of downtown Los Angeles.

Walls now surround the tar pits to allow the bones to be safely excavated.

These sticky deposits were naturally formed when asphalt, deep in the earth,

gradually rose to the surface, seeping into pools.

Since 1906, more than three millions fossils

have been recovered from over 400 species.

Making this one of the world's richest repositories of ice age animals.

I've never seen that before.

In a glass-walled lab called "the fishbowl,"

la brea paleontologists and volunteers separate ice age fossils from the tar.

They're exposing the skull and jaws of their biggest find yet,

a nearly complete mammoth.

Discovered under a nearby parking lot,

the team has named him zed.

La brea's tar is an ideal medium to preserve bone.

It penetrates them, protecting everything, from the most delicate bird bone

to zed's 200-pound skull.

The bones are so saturated that tar continues to ooze from zed's skull today.

From the size, width and condition of his two large molars,

they confirm zed is a male.

A columbian mammoth,

who was between 48 and 52 years old when he died.

When zed's 10-foot tusks were excavated,

they were encased in a protective jacket of plaster.

As the plaster is removed,

the tusks are seen for the first time

in possibly 40,000 years.

Ice age secrets come in all sizes.

As the asphalt matrix is cleaned from tar pit fossils

like this dire wolf skull,

it is sorted and what remains

is a treasure trove of tiny micro fossils.

In this spoonful of sediment are the fossilized bones from two snakes,

a mouse elbow, and the legs of two beetles.

Even plant seeds and leaves are found.

These micro fossils are a record of what lived in the la brea ecosystem

40,000 years ago,

and clues to the environment and climate at the time.

Zed may have been attracted to la brea's marsh-like setting,

unaware of its hidden dangers.

Once he stepped in, his fate was sealed.

Some creatures trapped in la brea's tar were quite bizarre.

A shasta ground sloth.

This furry plant eater roamed the American west and northern Mexico.

It's massive fore claws may have helped to fend off sabre-toothed attacks.

Though it was as big as a black bear,

it had relatives that were 20 feet long and weighed 6,000 pounds.

But the shasta is best known

for the unlikely climate clues it left behind

in the darkness of caves.

Sloth dung is so well-preserved in some caves

that it smells like fresh manure when broken open.

The content of the dung reveals what these animals ate.

Knowing their diet and the age of the dung,

scientists can track how vegetation and climate was changing.

Larger and less hairy than their woolly cousins,

columbian mammoths ranged all across north America

and into present-day Mexico.

In some places, the warm waters of natural hot Springs

lured them to succulent grasses, even in winter.

But a misstep could be fatal.

There was no escape from these steep, slippery sides.

Over thousands of years, the hot Springs turned into this.

An ice age tomb in south Dakota.

It holds the largest concentration of mammoths ever found.

Looking like an ancient burial ground,

57 columbian mammoths, three woolly mammoths,

and 28 other ice age animals have been discovered.

Dozens more lie buried still.

One by one, mammoths died here,

over a period of several hundred years

near the end of the ice age.

The position of this mammoth, facing upward with limbs sprawled,

is sad witness that he died while struggling to climb out.

Every bone here tells a story, like a diary.

Even ancient tusks give us information about the mammoth's life.

Tusks are made of a hard material called dentin,

similar to our teeth.

Each year of tusk growth is recorded in a layer of dentin,

like a tree ring.

A cross section of the tusk shows

that in years with good climate and plenty to eat,

tusks grew faster and rings are thicker.

In times of severe weather and less food, the rings are narrow.

Mammoths grew six sets of teeth over their roughly 60-year lifetime,

like elephants today.

By determining which teeth were present,

we can know the mammoth's age when it died.

Understanding the health and age of the mammoths helps us to know

what was happening in their environment.

Curiously, the bones at the mammoth site reveal another interesting fact.

All of the mammoths that perished here were young males.

Perhaps a little more adventurous and a little less cautious

than the female and adults.

Hot Springs and tar pits preserve many clues about ice age animals,

but these traps did not cause a mass extinction.

Something else was happening at the end of the last ice age.

The world of the mammoth was warming.

Animals adapted for a cooler climate faced a changing landscape.

Forests encroached on the grasslands, altering the food chain.

And just as a warming planet created ecological challenges,

another new threat to wildlife appeared.

A mammoth was no match for human Spears.

Mammoth gifts of food and fur and bone were invaluable survival resources,

but our greatest adaptation to winter

was the remarkable human mind

and the ability to tame the world around us,

to harness the power of fire and flint and bone.

Our ancestors met the cold with a burst of innovation.

They crafted bone tools and needles to sew clothing from hides.

Learn to paint, make music and sing.

They were creative, intelligent beings whose language and song

gave new calls to the winter night.

What ultimately drove the mammoths to extinction

is difficult to know.

Some speculate that the warming climate

reduced mammoth populations dramatically,

just as humans arrived to deal the final blow.

Roughly 4,000 years ago, while the pyramids were being built in Egypt,

the last mammoth perished

and the species ceased to exist.

About 12,000 years ago, the ice began to melt.

The world's climate had shifted again, marking the end of the pleistocene

and the dawn of the holocene epoch.

Our modern climate era had begun.

As the glaciers melted,

trickles became torrents

and north America was awash in rivers and floods.

By the end of the last ice age,

70% of the world's largest land animals had vanished,

gone forever.

A global temperature rise of just 16 degrees fahrenheit

was enough to change the entire face of the planet.

Melt water drained back into the oceans, and sea levels rose once again.

As the glaciers melted away, the sheer power of the bulldozing ice

was revealed in newly-created geography.

Trapped inland water pooled to form huge lakes.

The Great Lakes.

Where cathedrals of ice once stood,

cities of steel arose.

Humans flourished.

Our population grew from one million during the ice age

to many billions today.

Now, our industries create so much greenhouse gas

that we humans have become participants in the climate equation.

As the frozen footprint of the ice age continues to shrink,

the earth is becoming warmer than it has been

in the last 120,000 years.

Now, as at the end of the last ice age,

many animal species are threatened by extinction.

Wildlife again confronts a warming climate,

habitat loss and the pressures of a changing world.

The ice age has left behind cautionary reminders.

And as global warming melts the permafrost of the far north,

occasionally, an entire frozen mammoth is revealed.

Baby mammoth lyuba

was discovered when her icy tomb melted away.

She astounded biologists

because of her completeness and incredible preservation.

Ct scans reveal that all of her internal organs are intact.

And the discovery of mud in her throat and lungs

suggests that she died in a shallow lake.

Lyuba was only one month old when she died,

a sad fate for this young mammoth, but a gift to us

that she has traveled 42,000 years to share her ice age secrets.

We visit ice age relics and hold them in awe,

for they connect us to the past.

To look at lyuba is to look back in time.

Woolly mammoths, once titans of the ice age,

are now extinct,

while we who lived among them, live on.

Creatures from our frozen past continue to yield clues about their lives.

And the more we learn about their world, the better we understand our own.

But perhaps the greatest gift of the ice age

is neither bone nor hide.

It is our minds that helped us survive the ice.

And only our wisdom

may guide us toward a sustainable future.

For the ice age is a climate story more relevant now than ever.