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Daybreak
on North America's great plains.

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Denver International Airport
is coming to life

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and about to receive
the first arrivals of the day.

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By midnight,

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more than fifteen hundred aircraft
will have touched down here,

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delivering tens of thousands of people
to this modern metropolis.

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But when did people first
come to the plains?

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It's not so long ago
in the life story of the continent

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just 13,000 years since this
was virgin territory.

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And back then different giants
cruised the landscape.

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Imagine if we could travel back in time

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and see these plains as they were then,

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emerging from the grip
of the last great Ice Age -

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an area of pristine wilderness,

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stretching for one and
a half million square miles,

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untouched by man

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and brimming
with extraordinary animals.

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But 13,000 years ago, an even more
extraordinary animal arrived.

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What if we could follow in the
footsteps of these first hunters,

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as they entered the unknown

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and staked their claim
to these vast spaces?

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What would this wild new world have
looked like through their eyes?

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And what strange creatures
would they have encountered here

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on the American Serengeti?

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As North America emerged
from the grip of the last Ice Age,

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the door was opened to outsiders
for the very first time.

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As these early immigrants
pushed their way south,

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they found themselves in a land
of unimaginable opportunity,

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overflowing with game animals,

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animals with no experience
of humans or their weapons.

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The arrival of these hunters

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coincided with a time
of great change on the plains.

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Within the next few hundred years,

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many Ice Age animals
vanished forever.

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So 13,000 years on,

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how do we know anything
about this lost world?

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There are still clues to be found

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if you know where to look.

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In the Bighorn Mountains of Wyoming

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is a hidden cave, recreated here,

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where over the millennia,

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thousands of animals have fallen
to their deaths.

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Preserved below the surface

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are bones dating all the way
back to the Ice Age.

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Remains of bison lie alongside
antelope and rabbit

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but they're mixed
with those of camels,

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extinct horses, giant wolves.

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Even the mastodon
is buried here,

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a long-dead relative
of modern elephants.

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And this was once a bear,

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but not like any bear
in North America today.

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Claw marks gouged
into the cave wall

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show the bear was not
killed outright by the fall -

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it made a desperate attempt
to climb back out.

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It was a short-faced bear,

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an Ice Age heavyweight.

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What else can we tell about it
from its bones?

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Its weight was more than 700 kilos,

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twice that of a grizzly bear today.

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Upright, it would have stood
four metres tall.

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It was the largest flesh-eating mammal
that ever walked the earth.

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The Wyoming cave, appropriately
christened 'Natural Trap,'

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provides a unique window
on the Ice Age.

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During its coldest era,

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much of North America was covered by
huge ice sheets up to two miles thick.

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But as the continent
began to warm,

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the ice sheets started shrinking.

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Corridors began to open up along
the coast and through the mountains,

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letting people migrate south
from Alaska for the first time.

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Before them lay the almost
limitless great plains

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stretching all the way
from the Rocky Mountains

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to the Mississippi River

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and beyond to Mexico.

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Across this area, the shifting ice
left deep scars on the land.

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It carved out thousands
of lakes and ponds,

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and left the tapestry of streams
and rivers that drain the plains.

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The death throes
of the last great Ice Age

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left a signature
that we can read today.

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These giant 'potholes'

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were left behind
by blocks of buried ice

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that melted, leaving hollows
that later filled with water.

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For thousands of years since then,

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they've been vital pit stops
for migrating birds,

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the millions of cranes,
geese and ducks

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that follow ancient routes
across the plains.

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These rolling hills are made of debris
dumped by the retreating ice.

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It also left rich grasslands,

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able to support hundreds
of millions of bison -

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vast herds drifting
with the seasons,

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always searching for fresh grazing.

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Pronghorn antelopes are unique
to North America

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and among the toughest creatures
on the plains.

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Surviving year round
in the open

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they must cope with freezing
winter temperatures

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and scorching summer heat.

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Every spring

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these open spaces echo to the sounds
of courting sage grouse,

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as males compete to win a mate.

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Migrating sandhill cranes strut
and dance for their partners

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before heading further north
towards their nesting grounds.

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Small birds breed here,

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after an epic journey
from their winter home.

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These cliff swallows have flown
thousands of miles from South America.

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Mud from the ancient riverbanks
is good for building nests.

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It also holds more evidence

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that will help us to reconstruct
the Ice Age past.

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Every now and then,
new clues surface

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hinting at what else
might lie beneath.

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In this dried up pond
in South Dakota,

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known as Hot Springs,

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scientists unearthed
great piles of bones.

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What kind of creature
died here?

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The bones reveal it stood
four metres tall

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and weighed more than 10 tons.

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There's nothing fitting
that description living here today.

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Here's the give-away:

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a pair of tusks two metres long,

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the trademark of a Columbian mammoth,

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the biggest animal to roam
the Ice Age plains.

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By comparing it to elephants
in Africa today,

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can we shed light on
how those Ice Age elephants lived

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and what they lived on?

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These are mammoth teeth -

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huge molars the size of bricks.

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They have deep ridges very similar to
those of modern elephants,

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suggesting mammoths, too, survived
by grinding vast amounts of grass.

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Plant fragments trapped
between the ridges

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can still be identified today.

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Thousands of years
after this mammoth died,

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we know exactly what it ate
for its last meal.

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Grass is a tough, abrasive food.

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Even with protective enamel ridges,

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these teeth would gradually
have worn down.

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But just like modern elephants,

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the mammoths had evolved
a way to deal with this.

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As one set of teeth was eroded,

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another grew up to take its place.

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The evidence suggests
they had six sets in all,

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to last a lifetime - up to 60 years.

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The South Dakota mammoth
didn't make it to old age

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and it was not alone.

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The site turned out to be
a mammoth graveyard,

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hiding more than 50 skeletons,

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all from animals in their prime.

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There's no sign they were killed
by hunters,

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so how did so many
healthy mammoths die?

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The site was once
a spring-fed pond, full of water.

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Mammoths were tempted in
to drink,

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but when they tried
to climb back out

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the banks were steep and slippery.

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Just like the short-faced bear,
imprisoned underground,

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some became trapped.

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Scavengers would have been attracted
by the mammoths' plight.

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The bones of wolf, coyote
and the short-faced bear

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have also been recovered
from the dried up sediment.

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The search for food was probably
their downfall too.

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These prairie ponds are
like time capsules,

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and they store another
kind of data

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showing how the plains have changed
across millennia.

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Each spring, pollen from nearby plants
is blown into the water.

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It sinks and settles layer upon layer
on the bottom,

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building into a databank
of local plant life

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that we can still read today.

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And grass pollens aren't the only
clues still sandwiched in the sediment.

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There are a wide variety of
tree pollens too,

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from aspens, spruce and other trees,
both conifers and deciduous.

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This store of pollen paints a picture
of the plains of 13,000 years ago,

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a picture that looks very different

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from the open prairie
grassland of today.

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But why did this region look
so different back then?

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The ice sheets to the north,

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although retreating 13,000 years ago,

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still dominated the climate here.

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It was much milder
and wetter than today,

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ideal conditions
for woodland to flourish.

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This is how much of the northern
plains must have looked

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when the first people arrived;

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not open prairie as it is now,

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but a parkland of trees
and grassy meadows.

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This is a relic of those times -

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the Osage orange.

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Every autumn it produces
these enormous fruits,

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huge numbers of them,

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more the size of grapefruits
than mere oranges.

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But there's no animal alive today

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that's big enough
to pick and eat them,

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so this bumper crop just rots.

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The Osage orange glory days
are long gone,

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but its harvest was once an annual
feast for many Ice Age animals,

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including browsing mammoths.

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Fruit must have been a real treat
for these grass eaters.

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The Osage orange seeds were carried
far across the plains,

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before being deposited

194
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pre-packed in their
fertiliser 'grow-bags'

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ready to take root.

196
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As the Ice Age waned,

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the milder climate
and the mix of vegetation

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meant the plains were able
to support a range of wildlife

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00:17:34,488 --> 00:17:37,658
as diverse as Africa's Serengeti today.

200
00:17:39,193 --> 00:17:41,328
There were at least
five kinds of horse

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including a wild ass

202
00:17:43,430 --> 00:17:46,200
and another that resembled
modern zebra.

203
00:17:56,910 --> 00:18:00,848
And North America's very own antelope -
the pronghorn.

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13,000 years ago several different
species roamed the plains.

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The pronghorn lived alongside
other grazers still around today,

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00:18:18,365 --> 00:18:19,766
including bison.

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00:18:22,336 --> 00:18:24,571
This animal was common, too,

208
00:18:24,805 --> 00:18:27,608
but now it would seem
very out of place.

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00:18:28,041 --> 00:18:29,776
Bigger than its modern relatives,

210
00:18:29,977 --> 00:18:32,646
the Ice Age camel was
extremely hardy,

211
00:18:32,779 --> 00:18:35,349
able to eat almost any kind of food.

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00:18:39,686 --> 00:18:41,555
Elk, like many Ice Age animals,

213
00:18:41,655 --> 00:18:43,824
survive almost unchanged.

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The rich parkland was ideal
for these large deer.

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But one creature more than any other

216
00:18:50,931 --> 00:18:53,200
has remained a constant symbol
of the plains

217
00:18:53,267 --> 00:18:55,669
since people first set foot here -

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the bison.

219
00:19:07,014 --> 00:19:08,816
Adult bison are formidable -

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two metres tall and weighing
more than a tonne.

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00:19:12,419 --> 00:19:15,155
They too sheltered
near the trees in winter,

222
00:19:15,222 --> 00:19:17,357
taking to the plains again
in spring

223
00:19:17,457 --> 00:19:19,860
when new grass started sprouting.

224
00:19:21,094 --> 00:19:23,297
Bison calves are born in summer

225
00:19:23,397 --> 00:19:26,333
and can run within
a few hours of their birth.

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00:19:26,567 --> 00:19:28,168
They have no choice -

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the herd won't wait in its eternal
quest to find new grazing.

228
00:19:35,809 --> 00:19:38,612
Smaller grazers are still
found here, too,

229
00:19:38,946 --> 00:19:42,282
but they stay put instead
of wandering the plains.

230
00:19:43,550 --> 00:19:46,954
Prairie dogs inhabit rambling
subterranean 'towns'

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that stretch tens of square miles.

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00:19:51,825 --> 00:19:56,129
These highly social creatures stay
within a short dash of their door,

233
00:19:56,363 --> 00:19:59,833
ready to retreat from predators
or bad weather.

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00:20:02,002 --> 00:20:04,071
There's always maintenance work to do,

235
00:20:04,371 --> 00:20:07,407
but major renovations have to wait
until after rain,

236
00:20:07,541 --> 00:20:09,009
when the soil is soft.

237
00:20:18,185 --> 00:20:21,488
All this working and re-working
helps the land recover

238
00:20:21,555 --> 00:20:25,259
from the impact of so many bigger feet
and appetites.

239
00:20:31,431 --> 00:20:32,733
At summer's end,

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00:20:32,833 --> 00:20:36,170
male bison help
to move the sun-baked soil,

241
00:20:36,236 --> 00:20:38,272
as the rutting season starts.

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00:20:38,939 --> 00:20:43,844
They roll in dust and paw the ground
to try to dominate their rivals.

243
00:21:00,127 --> 00:21:04,164
The dust bath also helps
to dislodge irritating insects.

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00:21:08,068 --> 00:21:12,506
A prairie dog colony is usually
surrounded by short, nutritious grass

245
00:21:12,606 --> 00:21:14,842
thanks to the many teeth in town.

246
00:21:15,442 --> 00:21:18,378
This constant grazing
stimulates fresh growth

247
00:21:18,479 --> 00:21:22,416
and also keeps the field of vision
clear for spotting predators.

248
00:21:28,489 --> 00:21:31,758
Larger neighbours are attracted
to these verdant meadows,

249
00:21:31,859 --> 00:21:34,628
just as they were 13,000 years ago.

250
00:21:42,970 --> 00:21:46,006
Columbian mammoths had to feed
almost round the clock,

251
00:21:46,106 --> 00:21:48,242
to fuel their bulky bodies.

252
00:21:56,717 --> 00:21:58,785
But as the Ice Age ended,

253
00:21:58,886 --> 00:22:01,889
food was not
the mammoth's biggest problem.

254
00:22:05,492 --> 00:22:09,463
A new and deadly predator began
to infiltrate the plains,

255
00:22:09,630 --> 00:22:11,732
a match for any prey,

256
00:22:11,932 --> 00:22:13,867
even the mighty mammoth.

257
00:22:38,392 --> 00:22:41,361
These people knew how
to make lethal weapons,

258
00:22:41,662 --> 00:22:43,130
they left spear points,

259
00:22:43,263 --> 00:22:44,464
knife blades

260
00:22:44,565 --> 00:22:47,534
and other tools scattered
all across the plains.

261
00:22:47,801 --> 00:22:49,970
And they spread fast.

262
00:22:51,104 --> 00:22:54,074
The evidence suggests
it took them only a thousand years

263
00:22:54,141 --> 00:22:57,110
to spread across
the entire northern continent.

264
00:23:18,565 --> 00:23:19,933
What can we learn today

265
00:23:20,033 --> 00:23:23,203
about the lifestyle
of these butchers of the plains?

266
00:23:23,837 --> 00:23:26,273
They left a string of clues
to how they lived,

267
00:23:26,406 --> 00:23:29,243
including strange pyramids
of rocks.

268
00:23:29,610 --> 00:23:31,612
Inside are bones of animals

269
00:23:31,712 --> 00:23:35,048
that show how they were
slaughtered and cut up for meat.

270
00:23:42,789 --> 00:23:45,826
These cairns are thought
to be cold-weather larders,

271
00:23:45,959 --> 00:23:48,295
marking prehistoric hunting camps.

272
00:23:48,962 --> 00:23:52,132
When hunting parties had more meat
than they could eat or carry,

273
00:23:52,266 --> 00:23:56,737
they would stash the surplus under
these rocks to be collected later.

274
00:24:00,040 --> 00:24:03,010
They seem to have
used bones as markers.

275
00:24:28,669 --> 00:24:33,073
In a Colorado gully, hunters
carried out a mammoth massacre,

276
00:24:33,240 --> 00:24:36,743
leaving behind the remains of
at least 16 animals.

277
00:24:37,144 --> 00:24:38,912
The site recreated here

278
00:24:39,012 --> 00:24:41,081
contains a treasure trove
of evidence

279
00:24:41,148 --> 00:24:43,617
relating to the mammoths' daily life.

280
00:24:44,651 --> 00:24:47,621
Again by comparing mammoth bones
to elephants,

281
00:24:47,754 --> 00:24:52,192
we can calculate the sex and age
of all the animals that died here

282
00:24:52,292 --> 00:24:55,596
and deduce the make-up
of a Columbian mammoth herd.

283
00:25:06,039 --> 00:25:08,008
These are the bones of juveniles,

284
00:25:08,075 --> 00:25:12,412
up to around 14 years old,
both males and females.

285
00:25:15,649 --> 00:25:17,885
Several adults lie here, too,

286
00:25:18,018 --> 00:25:19,319
all females,

287
00:25:21,188 --> 00:25:25,792
including one huge specimen,
at least 40 years old.

288
00:25:33,934 --> 00:25:35,903
This range of age and sex

289
00:25:35,969 --> 00:25:40,007
exactly matches that
of a modern-day African elephant herd.

290
00:25:42,342 --> 00:25:45,279
An older matriarch,
the leader of the herd,

291
00:25:45,379 --> 00:25:48,949
is accompanied by her daughters
and other female relatives

292
00:25:49,082 --> 00:25:53,387
and they in turn are with their young,
both male and female.

293
00:25:58,725 --> 00:26:02,796
But where were the adult males
when this herd was destroyed?

294
00:26:05,399 --> 00:26:09,136
A unique clue to their lives was
uncovered in Nebraska.

295
00:26:09,736 --> 00:26:13,173
Recreated here are the skulls of
two gigantic males

296
00:26:13,240 --> 00:26:15,943
that died with their tusks interlocked.

297
00:26:17,044 --> 00:26:18,846
But how could this have happened?

298
00:26:20,714 --> 00:26:24,451
Again, our best bet is to look
at elephant society.

299
00:26:26,286 --> 00:26:27,621
During the breeding season,

300
00:26:27,754 --> 00:26:32,326
sexually mature bull elephants fight
for access to the female herds.

301
00:26:32,693 --> 00:26:37,664
The tangled tusks are direct evidence
that mammoths were aggressive, too.

302
00:26:42,870 --> 00:26:46,440
Because these two bull mammoths
both had broken tusks,

303
00:26:46,507 --> 00:26:48,308
they could have fought
at closer quarters

304
00:26:48,375 --> 00:26:50,010
than they would do normally,

305
00:26:50,444 --> 00:26:54,982
twisting and turning they became
locked in a deadly embrace.

306
00:27:08,028 --> 00:27:13,467
Even more bizarre, this twist of fate
then caused a third fatality -

307
00:27:13,600 --> 00:27:15,803
beneath one mammoth's
shoulder blade

308
00:27:15,869 --> 00:27:19,306
was the skull of a coyote,
pressed into the ground.

309
00:27:27,047 --> 00:27:30,584
While we can only speculate on just
how the coyote died,

310
00:27:30,651 --> 00:27:34,488
it's likely it was scavenging
around the decomposing carcasses

311
00:27:34,555 --> 00:27:37,491
when one caved in and crushed it.

312
00:27:40,060 --> 00:27:42,496
Coyotes are still
on the plains today.

313
00:27:42,863 --> 00:27:45,833
They hunt their food
as well as scavenge carcasses,

314
00:27:45,933 --> 00:27:50,804
but small live prey can be more trouble
than large dead ones.

315
00:27:54,975 --> 00:27:57,244
Prairie dogs are always on alert

316
00:27:57,377 --> 00:27:59,446
and once a trespasser is spotted,

317
00:27:59,513 --> 00:28:02,549
the entire town vanishes
into thin air.

318
00:28:08,021 --> 00:28:10,123
Prairie dogs aren't
really dogs at all -

319
00:28:10,190 --> 00:28:11,492
they're rodents -

320
00:28:11,625 --> 00:28:15,729
but coyotes are full-blooded members
of the canine clan

321
00:28:15,829 --> 00:28:17,331
and like all dogs,

322
00:28:17,431 --> 00:28:20,767
they sometimes hunt in groups
to tackle bigger prey.

323
00:28:21,568 --> 00:28:24,171
Some prey, however,
are just too big,

324
00:28:24,271 --> 00:28:26,373
even for a pack of coyotes.

325
00:28:42,055 --> 00:28:46,827
But 13,000 years ago, there was
another kind of canine hunter here

326
00:28:46,927 --> 00:28:50,564
one that gave even the bison
a run for their money.

327
00:28:51,231 --> 00:28:54,635
The wolf...
the ultimate pack hunter.

328
00:29:04,077 --> 00:29:07,147
A lone wolf weighs
as much as four coyotes,

329
00:29:07,247 --> 00:29:11,018
but one on one
it's still no match for a bison.

330
00:29:17,157 --> 00:29:20,694
Wolves, though, live and hunt
in packs of up to 15,

331
00:29:20,894 --> 00:29:25,232
and when they launch a co-operative
attack, they're devastating.

332
00:29:32,840 --> 00:29:35,042
First they get the bison
on the run,

333
00:29:35,375 --> 00:29:37,911
then filter out the weak
and vulnerable

334
00:29:38,011 --> 00:29:40,214
and select the perfect target.

335
00:29:50,624 --> 00:29:55,996
Striking together wolves can bring down
prey many times their own size.

336
00:30:04,771 --> 00:30:08,709
A million such chases must have
taken place across these plains

337
00:30:09,109 --> 00:30:13,814
and we can still find echoes of these
distant life or death encounters.

338
00:30:16,817 --> 00:30:20,120
Not all evidence lies
locked in bone and rock.

339
00:30:20,354 --> 00:30:22,089
These pronghorn antelopes,

340
00:30:22,222 --> 00:30:24,825
among the great survivors
of the Ice Age,

341
00:30:24,992 --> 00:30:27,594
reveal a lot about the distant past.

342
00:30:30,597 --> 00:30:33,967
As well as being tough enough
to stand extremes of temperature,

343
00:30:34,134 --> 00:30:35,969
they're famous for their speed.

344
00:30:39,840 --> 00:30:42,976
A sprinting pronghorn can
top 60 miles an hour

345
00:30:43,343 --> 00:30:46,246
and cruise at 30 for several hours.

346
00:30:48,415 --> 00:30:52,152
This kind of speed requires
a very finely tuned physique.

347
00:30:52,319 --> 00:30:54,188
Pronghorn have a massive heart

348
00:30:54,288 --> 00:30:56,623
and run with their mouths gaping open,

349
00:30:56,723 --> 00:30:59,693
forcing extra air
into their huge lungs.

350
00:31:03,597 --> 00:31:04,932
But what's the point?

351
00:31:05,332 --> 00:31:07,501
No predator can run this fast,

352
00:31:07,868 --> 00:31:10,871
even the wolves can
only manage 40 miles an hour.

353
00:31:11,338 --> 00:31:14,641
So why do pronghorn feel
this need for speed?

354
00:31:18,879 --> 00:31:20,547
This is why.

355
00:31:21,348 --> 00:31:23,150
Once there was a predator here

356
00:31:23,250 --> 00:31:25,452
that could outrun the pronghorn -

357
00:31:25,886 --> 00:31:26,987
a cheetah.

358
00:31:39,900 --> 00:31:41,768
13,000 years ago,

359
00:31:41,869 --> 00:31:45,339
the Ice Age cheetah was
the pronghorn's greatest enemy

360
00:31:45,439 --> 00:31:48,976
and pronghorn would have needed
all their amazing speed.

361
00:32:03,724 --> 00:32:07,027
The American cheetah was larger
than its African cousin,

362
00:32:07,161 --> 00:32:09,429
but it had the same Achilles heel.

363
00:32:13,167 --> 00:32:16,804
A cheetah's high-performance muscles
overheat in minutes

364
00:32:16,904 --> 00:32:21,375
and, unlike pronghorn,
it can't switch to cruising speed.

365
00:32:27,381 --> 00:32:29,716
So if the pronghorn managed
to outrun the cheetah

366
00:32:29,783 --> 00:32:32,486
for the crucial first
few hundred metres,

367
00:32:32,686 --> 00:32:34,388
it would probably survive.

368
00:32:38,759 --> 00:32:43,030
The cheetah hasn't roamed the plains
of North America for thousands of years,

369
00:32:43,197 --> 00:32:46,433
but pronghorn are still primed
for the chase.

370
00:33:11,325 --> 00:33:13,427
Other extinct links to Africa

371
00:33:13,527 --> 00:33:17,865
have been found in caves deep
in the Ozark mountains of Missouri.

372
00:33:21,835 --> 00:33:25,806
Preserved in mud were huge
prints recreated here,

373
00:33:25,906 --> 00:33:28,542
more than 18 centimetres wide.

374
00:33:29,143 --> 00:33:30,711
What could have made them?

375
00:33:34,882 --> 00:33:37,551
They belong
to another Ice Age cat,

376
00:33:37,684 --> 00:33:40,020
the top cat of the plains -

377
00:33:40,187 --> 00:33:41,288
a lion.

378
00:33:49,096 --> 00:33:51,832
Larger than any lion alive today,

379
00:33:51,999 --> 00:33:54,535
this would have been
an awesome predator.

380
00:33:56,203 --> 00:33:58,772
These caves were probably
its winter den.

381
00:34:14,188 --> 00:34:17,157
With such abundant game
down on the plains,

382
00:34:17,291 --> 00:34:19,993
this hunter's life must
have been pretty good.

383
00:34:27,801 --> 00:34:29,837
Sheer size and power,

384
00:34:29,937 --> 00:34:32,306
and the benefit of life
within a pride

385
00:34:32,406 --> 00:34:35,442
made it the unmatched
ruler of the plains.

386
00:34:37,077 --> 00:34:39,546
By looking at the
lions of Africa today,

387
00:34:39,746 --> 00:34:43,417
we can imagine how
these Ice Age cats once lived -

388
00:34:43,717 --> 00:34:47,754
in small prides based around
a group of hunting females.

389
00:34:53,360 --> 00:34:57,965
Like wolves, lions work together
to win larger prey.

390
00:35:06,273 --> 00:35:08,909
After a leading hunter
launches the attack,

391
00:35:09,042 --> 00:35:10,344
the others move in,

392
00:35:10,477 --> 00:35:14,081
helping to dispatch the victim
with a suffocating bite.

393
00:35:19,953 --> 00:35:22,489
But even for these rulers
of the plains,

394
00:35:22,589 --> 00:35:24,758
the good life had to end.

395
00:35:25,125 --> 00:35:27,261
They would be toppled
by another predator

396
00:35:27,394 --> 00:35:29,530
with even sharper skills.

397
00:35:35,969 --> 00:35:38,806
The Ice Age lions joined
the list of victims,

398
00:35:39,072 --> 00:35:42,009
animals that had lived here
for hundreds of millennia,

399
00:35:42,075 --> 00:35:44,311
but were soon lost forever.

400
00:35:52,820 --> 00:35:56,723
Today few signs remain that
any of them were ever here -

401
00:35:58,892 --> 00:36:02,629
odd traces scattered far
and wide across the plains.

402
00:36:03,797 --> 00:36:06,400
But if we piece together
bones and teeth,

403
00:36:06,500 --> 00:36:10,571
plant fragments and the clues
from animals alive today,

404
00:36:10,704 --> 00:36:15,108
we can begin to bring
a lost world back to life.

405
00:36:16,443 --> 00:36:21,248
So let's go back in time,
back 13,000 years,

406
00:36:21,381 --> 00:36:27,154
to relive one day in the life of
North America's great Ice Age plains.

407
00:36:33,293 --> 00:36:37,197
It's early morning at the end
of a long, hot summer.

408
00:36:37,364 --> 00:36:40,634
Even major rivers are
beginning to run low.

409
00:36:43,036 --> 00:36:46,206
A Columbian mammoth herd follows
the river valley,

410
00:36:46,340 --> 00:36:49,076
they can't risk straying
far from water.

411
00:36:59,219 --> 00:37:01,155
Once they've quenched their thirst,

412
00:37:01,255 --> 00:37:03,423
the next priority is food.

413
00:37:04,024 --> 00:37:06,160
They head out
to the nearby meadows,

414
00:37:06,260 --> 00:37:08,328
where they'll graze
most of the day,

415
00:37:08,428 --> 00:37:11,265
processing mountains
of dry grass.

416
00:37:13,433 --> 00:37:15,335
Autumn is mating season

417
00:37:15,569 --> 00:37:19,339
and a couple of nomadic males
have started shadowing the herd.

418
00:37:19,907 --> 00:37:21,141
By sparring,

419
00:37:21,208 --> 00:37:25,045
they decide who will have access
to the females coming into heat,

420
00:37:26,814 --> 00:37:29,483
who will father the next generation.

421
00:37:34,054 --> 00:37:37,424
Most power struggles are resolved
through ritual intimidation.

422
00:37:37,691 --> 00:37:41,128
But if two evenly matched males
cross paths,

423
00:37:41,228 --> 00:37:44,832
this posturing can escalate
into a full-blown fight.

424
00:37:48,202 --> 00:37:50,537
Both these opponents have a broken tusk

425
00:37:50,637 --> 00:37:53,674
letting them get closer
to each other during combat.

426
00:37:55,542 --> 00:37:58,979
Suddenly, a freak clash
leaves them in a deadlock,

427
00:37:59,112 --> 00:38:01,615
inextricably entwined.

428
00:38:06,787 --> 00:38:08,822
If they can't free themselves,

429
00:38:09,056 --> 00:38:11,592
they'll both end up the losers.

430
00:38:16,363 --> 00:38:18,899
As a constant source
of food and water,

431
00:38:18,999 --> 00:38:21,768
even when there's been
no rain for months,

432
00:38:21,902 --> 00:38:25,005
this valley draws thousands
of other grazers.

433
00:38:39,052 --> 00:38:43,490
And all this meat in one small area
attracts a scavenger -

434
00:38:43,524 --> 00:38:45,092
the short-faced bear.

435
00:38:46,126 --> 00:38:48,562
Led by his super sensitive nose,

436
00:38:48,662 --> 00:38:53,333
his long limbs carry him many miles
a day in search of carrion.

437
00:39:05,946 --> 00:39:07,381
He's picked up a scent,

438
00:39:07,481 --> 00:39:09,249
but where's the carcass?

439
00:39:15,722 --> 00:39:19,760
Sometimes the smaller, speedier
scavenger gets there first,

440
00:39:19,860 --> 00:39:22,229
on this occasion - a coyote.

441
00:39:40,180 --> 00:39:43,917
Right now the short-faced bear will
take whatever he can get -

442
00:39:44,218 --> 00:39:46,653
he hasn't had a decent meal in days,

443
00:39:46,753 --> 00:39:51,325
and needs at least one good-sized
carcass every week to stay alive.

444
00:39:57,598 --> 00:40:00,734
This time the coyote's left him
nothing but the skeleton.

445
00:40:01,201 --> 00:40:03,837
But with his huge, bone-crunching jaws

446
00:40:04,104 --> 00:40:07,708
the bear can crack them open
for the marrow locked inside.

447
00:40:16,183 --> 00:40:18,552
With water so scarce elsewhere,

448
00:40:18,685 --> 00:40:22,089
animals from miles around
converge here in the valley,

449
00:40:24,391 --> 00:40:26,994
which is good news
for the local lions -

450
00:40:27,161 --> 00:40:30,964
their pride territory is
now overflowing with food.

451
00:40:54,221 --> 00:40:56,690
Once the midday heat subsides,

452
00:40:56,790 --> 00:40:59,593
the females rouse themselves
to hunt.

453
00:41:08,669 --> 00:41:12,906
The scene is set
for a daily Ice Age drama.

454
00:41:22,249 --> 00:41:25,619
Only the very largest
are safe now.

455
00:41:36,230 --> 00:41:38,165
Patience is the key.

456
00:41:38,499 --> 00:41:40,701
The lionesses close in,

457
00:41:40,801 --> 00:41:43,303
waiting for their opportunity.

458
00:41:59,787 --> 00:42:01,955
The first charge causes chaos

459
00:42:02,055 --> 00:42:04,458
but this is just what the lions want.

460
00:42:04,691 --> 00:42:08,095
In the melee, they've already
pinpointed their prey.

461
00:42:16,537 --> 00:42:19,373
The leader pounces,
and a horse is down.

462
00:42:19,540 --> 00:42:22,943
Meanwhile, the spooked herds
stampede up the valley.

463
00:42:36,890 --> 00:42:39,593
But they're running straight
into another trap -

464
00:42:39,693 --> 00:42:44,031
a hidden cave, already full
of Ice Age victims.

465
00:42:50,938 --> 00:42:53,540
And now it claims another.

466
00:43:03,584 --> 00:43:06,687
Above ground, the members
of the valley pride -

467
00:43:06,753 --> 00:43:10,324
mothers, sisters and cubs feast.

468
00:43:17,064 --> 00:43:20,601
But their success
hasn't gone unnoticed.

469
00:43:23,504 --> 00:43:25,172
From many miles away,

470
00:43:25,305 --> 00:43:28,609
the short-faced bear can smell
blood on the breeze.

471
00:43:28,942 --> 00:43:31,645
He sniffs his way towards the source.

472
00:43:43,924 --> 00:43:47,161
Meanwhile, satisfied and sleepy,

473
00:43:47,261 --> 00:43:49,997
the pride settles down
for a snooze.

474
00:44:13,053 --> 00:44:16,590
More than twice the weight
of the pride's most powerful lion,

475
00:44:16,857 --> 00:44:19,693
the short-faced bear is
a daunting sight.

476
00:44:20,360 --> 00:44:22,863
Its trump card is
to use its massive size

477
00:44:23,063 --> 00:44:25,332
to frighten hunters from their kill.

478
00:44:38,712 --> 00:44:43,150
But the lions won't give up
their hard-won meal without a fight.

479
00:45:13,914 --> 00:45:18,051
This time, the bear's scare tactics
just don't work.

480
00:45:18,652 --> 00:45:20,621
The lions' numbers are against him

481
00:45:20,721 --> 00:45:24,858
and, despite his gnawing hunger,
he backs down.

482
00:45:36,069 --> 00:45:37,905
The autumn winds are rising,

483
00:45:38,105 --> 00:45:40,908
carrying another scent
across the plains

484
00:45:41,108 --> 00:45:45,045
and once again the bear's nose
sets his course.

485
00:45:56,356 --> 00:45:58,392
This trail leads to the cave

486
00:45:58,492 --> 00:46:00,594
and the freshly dead bison,

487
00:46:00,694 --> 00:46:02,496
just out of reach.

488
00:46:12,306 --> 00:46:15,576
Hunger makes the bear
risk everything.

489
00:46:28,856 --> 00:46:32,459
He falls and joins the bison
in its tomb.

490
00:46:33,393 --> 00:46:35,562
Now he can eat his fill,

491
00:46:36,063 --> 00:46:39,333
but after that there's no way out.

492
00:46:45,706 --> 00:46:50,344
In time he'll be just
one more Ice Age specimen.

493
00:46:59,219 --> 00:47:04,057
Outside, another group of predators
head for their cave at dusk,

494
00:47:04,291 --> 00:47:08,796
pack hunters even more effective
than the lion or the wolf.

495
00:47:17,037 --> 00:47:18,939
Still relatively new here,

496
00:47:19,373 --> 00:47:22,976
they'll eventually transform
the Ice Age plains,

497
00:47:23,043 --> 00:47:25,045
and build their own future

498
00:47:25,179 --> 00:47:29,450
by exploiting the herds
of the American Serengeti.

499
00:47:38,959 --> 00:47:42,329
Even the giants that now
dominate this Ice Age world

500
00:47:42,429 --> 00:47:43,964
will soon be gone.

501
00:47:44,565 --> 00:47:46,500
But they'll leave clues behind,

502
00:47:46,633 --> 00:47:51,004
and one day distant generations
will pick up their trail

503
00:47:51,105 --> 00:47:52,673
and tell their story.

504
00:48:05,518 --> 00:48:09,497
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