All around the world, hidden in museum storerooms,
are the fossil bones of animals most people never knew existed.
They belong to a group of creatures that rivalled the dinosaurs
in size and ferocity.
Now Walking with Beasts has brought these creatures back to life,
and this programme will reveal the incredible story
of how they came to dominate the Earth.
They are the mammals.
Surprisingly, the first very first mammals appeared on Earth
at the same time as the dinosaurs.
(ROARING)
But the dinosaurs quickly took over,
and during their 160-million-year reign,
the mammals made little impression.
The first mammaIs wouId have Iooked Iike shrews or mice.
They were tiny creatures, most of them.
If you find a fossiI, they are minute compared to the dinosaurs.
If you Iook at this tiny jaw -
this is a compIete jaw of one of the earIy mammaIs -
compared to the jaw size of this dinosaur,
this wouId be about the size of one of T Rex's teeth.
The mammals looked destined for obscurity,
but they were dealt an odd stroke of luck.
65 million years ago, the Earth encountered a few problems.
lt was the end of the dinosaurs.
A few groups of animals struggled through this Armageddon,
and the mammals were among them.
Today, the world is dominated by a magnificent variety of mammals.
But they owe their success to a remarkable set of characteristics
that were there from the beginning -
features that made them uniquely adaptable.
A warm-blooded metabolism helps maintain their body temperature
and live life at high speed.
Their fur coat means they can withstand a range of temperatures
and so live in an amazing variety of habitats.
They produce milk and care for their young,
giving them a head start in a dog eat dog world.
And they come equipped with a variety of different shaped teeth,
which means they can munch their way through almost anything.
They even have large brains, so they can learn as they grow,
and are able to adapt as they face new challenges.
To recreate this remarkable story of evolution,
Walking with Beasts teamed up with scientists and special effects artists.
At every stage, the sculptors and model makers
relied on studies of the fossils to put flesh on the bare bones.
They even took expert advice
on where to take their animals to feed and drink.
On the computer, scientists advised animators
on how to get the animals up on their feet.
Perhaps the biggest challenge was working out how they might have behaved,
especially when all that was left of these creatures
were a few bones and teeth.
Fortunately, palaentologists can tell a lot about a mammal from its teeth.
MammaI teeth are hugeIy variabIe.
Whereas dinosaurs onIy had two or three kinds of teeth,
mammaIs have dozens of different kinds and they're hugeIy different.
This is the tooth of a mammoth, just Iike the tooth of a Iiving eIephant.
Here's the root, here's the grinding surface,
and it's ridged with these thickened structures across here.
Other kinds of mammaIs have different sorts of teeth.
This is a cave hyena, a giant hyena.
The teeth are different.
At the front here are the incisors, here are the canines for piercing fIesh.
Towards the back, these extraordinary broad, sharp-edged teeth
used for crushing and smashing bone.
If you Iook at the teeth of a mammaI, you can teII very quickIy what it ate.
This IittIe chap has sharp pointed teeth.
They wouId have been used for piercing the outer carapace of insects.
An insect eater of some sort.
This one is obviousIy a fIesh eater.
Look at these vast pointed teeth.
Here's the canine tooth, used for piercing through fIesh.
The incisors at the front are just as fierce, for cutting up fIesh and bone.
Towards the back are these massive cutting teeth
for shredding fIesh, cutting through bone,
chewing and reducing it before they swaIIowed.
When you Iook at the teeth from this creature from South America,
you can see the shape of the incisors.
They Iook human-Iike, not very sharp - a pIant eater.
Towards the back, the moIar teeth - the cheek teeth -
are broad, grinding surfaces,
rather Iike the teeth of horses or cattIe.
The dinosaurs were lucky.
They lived through a period of stability in the Earth's history.
The weather forecast for 160 million years was warm and humid,
but mammals have had to deal with a different kind of world -
one that would keep the best forecasters guessing.
This unpredictable place saw huge fluctuations in climate.
Seasons arrived, forests came and went,
whole habitats were created and destroyed...
and the icecaps just kept on growing.
The last 65 million years of the Earth's history
has been a roller coaster ride.
For the mammals, it was adapt or die.
Just how they seemed to like it.
Their first test after the Earth recovered from the great extinction
was to adapt to a world completely covered by tropical forests.
South of Frankfurt in Germany there is a spectacular fossil site
with evidence ofjust how different the world was 49 million years ago.
This is a unique glimpse into a time when mammals had just begun to take off.
Palaeontologists have discovered
that this abandoned mine was once surrounded by lush tropical forest
and full of an extraordinary collection of animals.
We have some of the weirdest animaIs I know of
in the history of mammaIs at aII.
ExtremeIy smaII horses, about 30cm high.
ExtremeIy Iarge predacious birds, two metres high.
Leptictidium is one of the strangest animaIs which Iived here.
Running or hopping on two Iegs - nothing today is Iike that.
These so-called Messle sediments
gradually built up over millions of years,
capturing an entire ecosystem.
The detail in these fossils is exquisite.
ln some, the fur outline of the entire body is still visible.
ln others, you can see the remains of the last meal inside their stomachs.
The rocks have revealed an extraordinary explosion in diversity.
Almost every group of modern mammal
can trace its earliest members to this time.
It's an amazing time for the history of mammaIs
because we have not onIy these weird mammaIs,
but aIso a Iot of mammaIs which are part of the groups we know today.
Some, like the bats and anteaters,
haven't changed much for millions of years,
but others, like the early horse, were very different then.
If you compare the smaII MessIe horse with the horse today,
you wouId not think that this is the same kind of animaI, but it is.
This is why this site is so fascinating.
Although it was about the size of a cat,
Propalaeotherium is the forerunner of modern horses.
lt has all the same features, but in miniature,
though instead of one hoof it has several hoof-like toes.
OK. Cut there.
Varied though they were,
one thing the mammals had in common was their size.
EarIy mammaIs were smaII, Iiving in tropicaI forests.
They got bigger than in the age of the dinosaurs, but onIy pig size.
They Iived beIow the trees; some couId cIimb and adapt to new diets.
They couIdn't get very big in those forests.
So, if mammals were small, who WERE top of the food chain?
Looking at modern descendants,
it might be hard to believe, but mammals once lived in mortal fear
of birds.
Never underestimate the power of a beak.
I just gave RiIey a braziI nut.
It wouId be extraordinariIy difficuIt for us to crack.
We can't do it with our teeth. It takes tooIs for us to do it,
whereas RiIey, with a skuII this big,
can actuaIIy crack that nut just using its skuII.
Now imagine a very, very big Riley.
The first thing you see in this extinct bird
is that it couId have deIivered an impressive bite.
The skull belonged to a gigantic two-metre-tall bird called Diatryma
or Gastornis.
If we compare RiIey's skuII - about this big -
to the skuII of these gigantic birds,
we can see this animaI is way overbuiIt for cracking anything Iike nuts.
ln fact, Gastornis was over-engineered in many ways,
compared to modern birds.
Large, fIightIess birds are around today, Iike the ostrich.
It's obviousIy buiIt aIong different Iines.
It has a reIativeIy tiny skuII.
CertainIy not the massive skuII,
Iarge skuII, that we see in extinct birds.
Gastornis was big and powerful, and specialised in one thing -
eating mammals.
Gastornis or Diatryma, with such powerfuI jaws,
was abIe to eat struggIing prey, eat vertebrates;
perhaps not just to eat the fIesh but to crack open the bones
and extract the highIy nutritious marrow in the bones.
Gastornis was a gruesome reminder of something that had come before.
These birds were doing the same thing as a Tyrannosaurus
or any other predatory dinosaurs.
These mammaIs may have viewed them much the same way.
lf the world had stayed covered in tropical forest,
it's possible birds, not mammals, would have remained in charge.
But while predatory birds ruled the roost on land,
some mammals found escape
in an unlikely place for a furry, four-legged creature -
the water.
Here they started to grow very, very big indeed,
eventually leading to the largest animals ever - the whales.
Whales are proof of the amazing adaptability of mammals.
But how these 150-tonne beasts evolved from small tree-dwelling creatures
has been one of the greatest scientific mysteries.
For over a century,
scientists have scoured the Earth for fossils of ancestors of whales on land.
ln the 1920s, an intrepid American called Roy Chapman-Andrews
led a huge expedition to Mongolia to discover fossils.
One of his most spectacular finds
was the skull of a large hoofed carnivore.
Close examination of its teeth
revealed surprising similarities to those of whales.
lt turned out to be a distant relative.
It's extraordinary to Iook at a whaIe or doIphin
and reaIise its ancestor was a Iand-Iiving creature
which wouId have Iooked Iike a pig or a giant dog.
Over the years, the skeIeton, skuII and teeth of mammaIs can adapt,
and has adapted rapidIy.
No one knows what prompted hoofed carnivores to take the plunge
and eventually become swift swimmers.
ln fact, nearly all mammals can swim.
lt's just that most would rather not.
By studying living animals, it is possible to work out
how mammals could have made this remarkable transition.
As it happens, the world's expert
on swimming mammals is Dr Frank Fish.
He believes he's uncovered
how an ancient landlubber could become an expert swimmer.
If we Iook at this dog paddIing,
you see aII four of the Iimbs stroking the water in an aIternate fashion.
What a dog paddIe reaIIy represents is sort of a trot
that the animaI's doing whiIe it's in the water.
It isn't a very efficient gait.
A mammal equally at home in water and on land is the otter.
Otters seem to represent
what a missing link between whales and land mammals might look like,
making them a fascinating animal to study, even if they don't always cooperate.
Dr Fish is trying to record their unique swimming action
on a slow-motion camera.
Great.
ln the lab, he has discovered a few simple changes in swimming style
that enable a land mammal to swim more like a seal, less like a dog.
What we find is, instead of using aII four Iegs,
the otter is instead using just its hind Iegs.
Its front Iegs are tucked up underneath it.
The hind Iegs paddIe simuItaneousIy.
The otters are not just running in the water.
They use their back feet together to act as a paddle,
allowing their spine to flex up and down, driving them forward.
lt's a much more efficient stroke.
Otters represent a transitionaI stage,
something intermediate between both Iand and water.
Because of that, they're reaIIy of interest.
They probabIy represent, at Ieast in a modern form,
what the ancestors of animaIs Iike doIphins may have been Iike.
But otters are modern animals.
No one had ever found an otter-like ancestor to the whales,
a missing link between land and sea.
Then, in 1992, at a remote dig site in Pakistan,
palaeontologists discovered a remarkable set of bones.
They seemed to assemble a creature made up of an assortment of parts -
one that could live on land AND in the water.
lts discovery was a triumph for scientists.
lt was the elusive missing link.
lt was called Ambulocetus,
which appropriately means "walking whale".
When I first saw an AmbuIocetus skeIeton,
the bones were robust.
They remind you of semi-aquatic animaIs such as otters.
AmbuIocetus probabIy moved somewhat Iike otters today.
It had expanded Iimbs, in terms of its hands and feet,
which were probabIy webbed so it couId deveIop thrust in a paddIing manner.
It aIso had a robust taiI,
and probabIy was starting, Iike otters, to use the taiI motion to produce thrust.
Ambulocetus was totally new to science.
Dr Fish's work helped the Walking with Beasts team
to make it move, both on land and in the water.
But Ambulocetus wasn't the end of the whale's tale.
After all, it was an animal still tied to land.
lt didn't explain how whales became larger and truly aquatic.
This was the next stage in the story.
lt's the last place on Earth
you'd expect to find anything to do with water.
But here in the Sahara Desert there is evidence
that underwater creatures once lived here.
lt's a place that intrigues marine palaeontologist Dr Mark D'Uhen.
40 miIIion years ago, this was a vast ocean that we caIIed the Tethys Sea.
It extended from the North AtIantic across the Mediterranean,
covering North Africa and northern India.
The water wouId have covered even the highest peaks.
The Iayers that you see here were once the ocean bottom.
You can see evidence for that here.
Here's an oyster sheII.
Here's a snaiI.
I even found a shark tooth.
These are things you don't expect to find in the desert.
Something else you don't expect to find are giant whales.
When skeletons like these were discovered in the 19th century,
they were thought to be huge sea serpents.
They were named Basilosaurus, which means "king lizard".
But Basilosaurus was no giant lizard.
lt has a mouthful of unmistakably mammalian teeth.
This is the snout and this is the roof of the mouth.
These are the incisors.
These are the front teeth, here, here and here.
As you get further back, the teeth have two roots.
You see two here, two here and two here.
BasiIosaurus has very few teeth compared to modern toothed whaIes.
It has the number of teeth more Iike primitive mammaIs.
They use their front teeth to grab onto prey.
They use their back teeth to chew,
unIike modern toothed whaIes, which swaIIow their food whoIe.
This area in Egypt was named Valley of the Whales
because the desert floor is littered with the remains of Basilosaurus.
These creatures were giant predators,
but they were't quite like modern whales yet.
Their bodies were snake-like
and they still had primitive characteristics
that linked them back to their ancestors on land.
These are the back Iegs of BasiIosaurus.
You can see the peIvis, the femur, the kneecap,
the Iower Ieg, the foot with toes on it.
These tiny hind Iegs weren't attached to the backbone.
Their size shows they couIdn't support their body weight on Iand.
If they didn't use them for waIking, then what?
One idea is they were used as sexuaI cIaspers,
that the maIe and femaIe used them
to hook up during mating and hoId on whiIe they mated.
At 1 8 metres long,
Basilosaurus was probably the largest animal on Earth at that time.
lt was a challenge for the scientists and special effects artists
to make it work properly.
The scale model had to be shrunk to fit
and it still took four people to control it.
Sort of sinister, spooky.
(BLOWHOLE SQUIRTS)
And working out how to get an extinct animal to swim
was a combination of artistic skill and scientific advice.
So, wouId you Iike to see those...
What are these? Back Iegs or...?
Hind, back Iegs. Back Iegs, right.
I'd Iike to see if the joints wiII do it.
Just traiIing,
pointing absoIuteIy straight back.
- Like an otter's feet, for exampIe. - Yeah, sure thing.
Now at last the story can be told
of how hoofed carnivores evolved webbed feet and started to swim.
Eventually, their backbones loosened, their legs got smaller
and their tails turned into flukes.
The mystery of how a group of mammals conquered water was complete.
Whales represented the mammals' first attempt to get truly enormous.
But land mammals were not far behind and they got their chance
once the climate turned against the rainforests.
Life on Earth came under the influence of one continent - Antarctica.
Over millions of years, other continents moved away,
leaving it isolated over the South Pole.
Gradually the continent became colder and colder
until a permanent icecap formed.
This triggered a change in the world's climate.
lt meant a drop in global rainfall.
Rainforests shrank, making way for new habitats.
There were aII sorts of changes going on.
CIimates worIdwide were getting cooIer.
There was the beginnings of the retreat of the forests
as those cIimates changed,
and animaIs were creeping out on to the pIain.
All this change played into the hands of the land mammals.
Birds lost their place at the top of the food chain
and mammals seized the opportunity to move into the open.
So that gave a big advantage to Iarge size.
If you're out of the forest, out of protection,
if you're big, you can escape predation.
You can run faster from predators.
The changing climate created a new breed of giants.
The age of the mammals had truly arrived, and it was ugly.
This is Entelodont,
not the thing you'd want to meet, even in a nightmare...
unless you happened to be a palaeontologist like Dr Scott Foss.
I've thought what it'd be Iike to meet an EnteIodont.
I aIways imagined these as creatures that wouId have an attitude.
They'd waIk in and say, "I'm here!"
No one would argue with such a mouthful of weapons.
The mouth of the EnteIodont is pretty incredibIe,
and we know from these huge muscIes here that wouId puII on the jaw
that these animaIs had a strong, powerfuI bite.
They couId grab onto things and twist and rip it away.
I'd say the words wouId be puIverised, mashing...
crushing, grinding, grabbing things, twisting and puIIing them.
They were scavengers, generaIists. They couId do anything they wanted.
But even the biggest, nastiest creatures have their enemies.
Looking at EnteIodont skuIIs, we find bite marks,
sometimes in the side of the face.
We find it right up here in the forehead.
We even find bite marks in the roof of the mouth.
If you can imagine that, bite marks into these creatures.
What creature couId get its jaws round an EnteIodont?
Another EnteIodont.
We know that because their teeth couId have made those bite marks.
AIso, there's not a singIe other animaI at the time
that couId have made such bite marks.
It was EnteIodonts doing this to each other. The big question is why?
Today animaIs wiII do battIe with other animaIs of their species,
mostIy for mate competition or territory competition.
It's probabIy a form of competition -
a very painfuI form of competition.
Entelodonts were the ultimate all-purpose animals,
built like tanks and able to eat anything -
a typical mammalian success story.
It's hard to say why we don't have EnteIodonts today, why they didn't make it.
If we were to reIease them in North America, they might do very weII.
They wouId eat anything.
I imagine they wouId especiaIIy Iike potato chips
and hot dogs and things Iike that.
They'd probabIy do very weII untiI they got into a popuIated area
and that wouId be the end.
I don't think there wouId be room for peopIe and an EnteIodont in suburbia.
(ALARM BLARES)
The Entelodonts were a new breed of large mammal.
But it wasn't long before they were upstaged
by the largest land mammals ever to live.
On Roy Chapman-Andrews' expedition in Mongolia,
the dig diary records the discovery of a single bone,
"Big as a man's body".
Some of those bones found their way to the Natural History Museum in London.
Bones over a metre long should be easy to find,
but there are a lot of bones in the museum
for Professor Mikael Fortelius to search through.
This is the bone of a very Iarge animaI.
If I found this, I wouId probabIy think that it was an eIephant.
It's very, very Iarge.
In some ways, it's Iike a giraffe and, in some ways, Iike a rhinoceros.
But it isn't Iike anything aIive today
and it's much much bigger than anything that Iives today.
lt took scientists a while to work out what sort of creature it was.
The only thing that was clear was that it was big.
This thing here is the neck vertebra
of a medium-sized rhinoceros from the Ice Age.
It's a Iarge bone,
but it's nothing compared to this, which is huge.
They had found an ancient type of rhino called an lndricothere.
When we think of Iarge Iand animaIs, we aIways think of dinosaurs.
Dinosaurs WERE the Iargest animaIs we know about,
but some Iand mammaIs aIso got Iarge,
such as this Indricothere.
It stands seven to eight metres taII.
It's about as Iong
and wouId have weighed perhaps up to 15 tons.
And, as you can see, I don't even reach up to the top of its Iegs.
The lndricotheres were rhinos trying to be giraffes.
Long necks could reach the treetops,
but they were massive and heavy like a rhino.
They were an extraordinary feat of engineering.
But these monsters were gentle giants,
browsing only on tender young leaves.
ln the case of the lndricotheres, that was a lot of leaves.
Why be big? It means you have nothing to hunt you,
no predator big enough to eat you.
But, being big, you can be vuInerabIe,
because popuIation sizes are quite smaII
and it doesn't take much to make a Iarge animaI extinct.
The days of the lndricotheres were numbered as the Earth changed.
Antarctica's increasing isolation brought a shiver to the climate.
As ice spread at the South Pole, it shifted the weather patterns,
bringing new seasonal extremes of drought and deluge.
Out of the turmoil, an astonishing new plant evolved,
one that we couldn't imagine life without.
lt was grass.
PeopIe think grass was aIways here, it's so common.
You'II see pictures of dinosaurs waIking on grass. That's not possibIe.
The first grasses appeared about 30 or 40 miIIion years ago, and they took over.
CIimates became drier and inIand areas became great savannahs.
As the savannahs grew, the grassIands expanded.
The woodIands, the earIy home of the mammaI, disappeared.
MammaIs had to adapt.
They came out from under the trees,
became bigger, Ionger Iegs, hooves, they ran faster and their teeth adapted.
Many of the animals that browsed on leaves went into decline.
ln their place came a new breed of mammals,
the grazers.
But grass is surprisingly difficult to survive on.
Luckily, mammals had the answer.
They developed a battery of teeth, complex stomachs and long legs
to follow the grass wherever it sprouted.
But where there was meat on the hoof, predators quickly followed.
The competition for survival
brought with it some of the most deadly animals on Earth.
If we Iook at the evoIution of cats and of other predators,
we can see that they've got faster,
they've got bigger and better at what they do.
EquaIIy, the prey species have got faster, bigger and better at escaping.
There's what you may caII an evoIutionary arms race between them.
Prey want to get away, predators to catch them.
And so, over time, there has been a tendency to do the best they can,
to reach the optimum soIution.
The cat family are the ultimate predators.
No other mammal is such a finely-tuned assassin.
What makes a cat such an efficient kiIIing mechanism?
These tiger cubs are four months oId
and aIready they've got aII the attributes that they'II need,
just in a smaIIer form.
They've got Iarge feet, very Iarge paws,
Iong cIaws - very sharp.
They've got teeth that are abIe to sIice off meat,
abIe to bite into prey, to kiII it.
They have whiskers to sense
exactIy where the item is, so it can bite preciseIy.
They're strong, weII-muscIed and fast-moving.
AItogether, this makes an animaI
that is superbIy equipped for what it needs to do.
A full-grown Siberian tiger can weigh as much as 300kg
and is the largest cat today.
But compared to some of its ancestors,
it would look like a pussycat.
There was a creature that died out a few thousand years ago,
with the most lethal weapons of any carnivore.
lt was called Smilodon, the fabled sabre toothed cat,
with its 20cm-long teeth.
The sabres were Smilodon's most dramatic feature,
but the whole package made it such a lethal killing machine.
(SNARLING)
If you Iook at the skeIeton as a whoIe,
it was a very, very strongIy-buiIt cat.
The forequarters, front Iegs, shouIders and neck are extremeIy heaviIy buiIt.
Like many cats Iiving today, it was fast over a short distance,
probabIy an ambush predator, abIe to sprint out from cover,
using its speed to cIose the distance very quickIy,
then its strength to seize the prey and puII it down.
As usual, it's the teeth that tell you how Smilodon went about its business.
If you Iook at the skuII of a SmiIodon,
your eye is immediateIy drawn to these sabre teeth.
But it's got teeth at the back equipped for sIicing meat.
It's got teeth at the front that are equipped for puIIing meat off,
getting it into the mouth.
It has large upper canine teeth
that are equipped for slicing into the prey once it's heId immobiIised.
Everything about it shouts "predator" at us.
This is not an animaI that can eat grass or vegetation.
It's a predator. It's a kiIIer.
The giant sabres were there for one gruesome purpose.:
to be driven into the neck of the prey
and, in one bite, to rip its throat out.
Although the mammals seemed to be on top of the world,
conquering every habitat,
the Earth was about to create the biggest challenge yet -
life in the freezer.
Both the Earth's poles began to freeze over 2.5 million years ago.
The lce Age had begun.
lce sheets grew beyond the Arctic Circle, over much of the northern hemisphere,
transforming all plant and animal life.
At the height of the lce Age, there were icebergs off the coast of lreland,
permafrost beneath London, and glaciers reached as far south as New York.
For most animals,
it became an inhospitable place.
But some mammals took the cold in their stride.
Europe, North America and Siberia became filled
with some of the most spectacular animals ever seen.
Don't drop it on the ground yet.
Exotic giants from the tropics evolved to suit the conditions further north.
EIephants originaIIy evoIved as tropicaI animaIs,
but mammoths deveIoped a very speciaIised adaptation to extremeIy coId cIimates.
They had thick, wooIIy fur.
They had smaII ears, so they didn't Iose heat.
They had a thick Iayer of subcutaneous fat,
short back Iegs so they, again, did not Iose heat.
The Iong tusks were used to cIear away snow
because they fed on grasses and other smaII pIants.
One of their most speciaIised adaptations was the tip of their trunk...
which had two Iarge fingers
that Iet them feed on the very smaII pIants
that were their main subsistence items.
All these magnificent creatures were around until so recently
that instead ofjust bones,
the remains of their skin and hair are preserved in the ice.
These finds provide unique information on what these extinct animals looked like.
Sometimes it has even been possible to recreate specific events in their lives.
Whole carcasses were found in the prime of life,
having been trapped in frozen ponds.
ln some cases, the flesh from their bodies could still be eaten.
(TRUMPETING)
The lce Age was a harsh environment,
but mammals were tough enough to meet this challenge.
Their trademark fur and assortment of teeth
kept them warm and well fed.
But having survived and thrived for so long,
something mysterious was about to happen.
Giant mammaIs of the Ice Age, such as the mammoth,
the wooIIy rhinoceros, MegaIoceros, the giant Irish eIk,
were aII very successfuI animaIs that survived in a harsh cIimate.
Yet they disappeared reIativeIy abruptIy. Why was that?
Around 30,000 years ago,
most of the giant mammals across the world started to become extinct.
By 10,000 years ago, as the lce Age came to an end,
almost all had died out.
The mammals had flourished despite every change on the Earth.
They'd even survived an ice age.
So why did the large ones suddenly vanish?
There is one group of mammals we haven't talked about - primates.
From the beginning, they kept pace as the Earth changed.
Then, only a few thousand years ago, one species became fantastically successful.
Could humans have had a hand in this catastrophe?
Find out if we wiped out the lce Age giants
in the next programme -
The Beasts Within.
And cut! Thanks, everyone. That's a wrap.