Nova (1974–…): Season 34, Episode 9 - Bone Diggers - full transcript

Nova follows the excavation of a paleontologist's gold mine, an Australian cave containing fossils of eight new species of kangaroo, and the ultimate prize, a complete skeleton of the marsupial lion, thylacoleo carnifex, previousl...

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An amateur explorer cruising the
skies of the Australian outback

makes a chance discovery...

A prehistoric cave
that's never been explored.

Inside, something no one's
ever seen before...

A mysterious fossil.

There was one particular
skeleton, and I said, well,

it doesn't look like
an old cow to me.

I wonder what it is.

The strange bones are
the start of an adventure.

A team of researchers launch
an expedition

to hunt for a long lost killer,



as fearsome as any
top predator today.

This is perhaps
one of the most important

Western Australian Museum
field trips

I'm ever going to do.

On a continent full
of unique animals,

they're on the trail of
a powerful, prehistoric lion.

For years, scientists have had
only fragments

of the lost predator to study,

and its mysteries
have remained unsolved.

It's an animal that's
full of paradoxes.

There's nothing quite
like it that exists

anywhere else in the world.

I think it would be quite
a fearful animal to encounter.

Now, struggling
in difficult conditions,



the scientists have only a
short time for a breakthrough.

Time to go, guys.

It's a daring search
deep below the ground...

Each time they do it,
they've got to treat it like

it's their life in their hands.

And a race against the threat
of fossil poachers,

who could steal
the precious bones.

Yeah, I wouldn't come
any closer, actually.

In fact, the whole skeleton
could be right here.

The team will work for
three intense weeks

to rescue the remnants
of a unique ancient beast.

You know, this is something

us paleontologists
dream of every day.

Good one.

This is, perhaps, one of
the most important discoveries

ever made in Australia.

Right now on NOVA...

"Bone Diggers."

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THE HOWARD HUGHES
MEDICAL INSTITUTE,

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The Australian outback...

A vast, trackless wilderness

filled with
extraordinary creatures,

including more than 200
different kinds of marsupials,

which carry their babies
in a pouch.

The outback is also home

to one of the most ancient
cultures on earth...

The Aboriginal people
who came to Australia

about 50,000 years ago.

Their legends conjure up
huge, bizarre beasts,

created in an ancient era
called the Dreamtime,

long before the advent
of humans,

when heroic spirits summoned
the landscape into being.

The stories speak of wombats
the size of buffalo,

killer kangaroos
over eight feet tall.

Could these aboriginal myths

be a distant echo
of something real?

A million or more years ago,

an array of giant animals
flourished here,

distantly related to those
on the outback today.

But all of them died out toward
the end of the last ice age.

In Perth, a team of
Australian paleontologists

are about to embark
on a daring hunt

for one of the lost
prehistoric beasts.

John Long is heading
the expedition,

a journey that started almost
completely by chance.

I was sitting in my office
looking at the computer

and an e-mail came through.

And it was an e-mail from
someone I'd never met before.

And then I saw
there was an attachment.

And I clicked on it,

and as the attachment slowly
opened, my jaw dropped.

The attachment
was a mysterious photo.

It was taken in a newly
discovered cave.

It may be the find
of a lifetime...

The skeleton of an animal that's
puzzled Australian scientists

for over a hundred years.

I was totally elated.

And very excited.

My first thoughts were that
I had to mount an expedition

and we had to go and recover
this remarkable fossil.

Following directions
that came with the e-mail,

Long and his colleagues set off
on three full days

of rugged driving, deep into
the Australian outback.

This is perhaps one
of the most important

Western Australian Museum
field trips I've ever been on

and perhaps one of the most
dangerous missions

I'm ever going to do.

They're heading
to the Nullarbor Plain...

More than 700 miles of almost
uninhabitable land.

The Nullarbor is one
of the great

vast, flat areas of Australia.

It's a huge area covering

several thousand square
kilometers.

It's very easy to get lost in

because there
just aren't any landmarks.

Although it appears empty,
the Nullarbor is home

to many animals today...

Distant relatives of
those enormous creatures

that lived a million years ago.

There were giant goannas, the
order of six meters in length.

There were huge
gargantuan birds...

The largest that ever
walked on the planet...

Came from Australia
at this time,

the dromornithids
or "thunderbirds."

We had a whole range
of large animals,

a bunch of giant kangaroos,
and huge wombats

the size of small cars,

and at that time,
it was kill or be killed,

and it was pretty well
cutthroat.

Of all the prehistoric animals,
one of the most mysterious

is a marsupial lion called
Thylacoleo carnifex.

Very little is known
about Thylacoleo.

Fossil fragments have been found

scattered across Australia,
but never a complete skeleton.

And that is what
John Long thinks

is pictured in the e-mail.

At the end of a long drive,
they finally make camp.

For three weeks, they'll live in
harsh and isolated conditions.

We were about, uh, almost
2,000 kilometers from Perth

and almost 900 kilometers
to the nearest town.

You have to bring in
all your food,

all your fuel, all your water,
all your expertise

and then just do your work.

In the middle of this desert,

they'll be at the mercy
of the elements.

Temperatures in the daytime
soar over 100 degrees...

And drop to freezing at night.

And when the wind kicks up,

it can literally
blow the camp away.

But this parched landscape
was formed

in a totally different
environment than today.

Right here where I'm standing,
20 million years ago

was the bottom of the sea.

Limestone rock was formed.

Today the Nullarbor Plain is
vast and featureless,

but below ground
is a different story.

When ground waters rose up,

percolating through
that limestone rock,

dissolving away
calcium carbonate,

the result was the formation
of caves.

Today, there are thousands
of caves

throughout the Nullarbor region.

Only a few of those caves are
known to contain fossils.

Concealing their location
is critical,

because there's a thriving

international black market
in ancient animal bones.

It's very important because
of the security of this cave

that we don't... we do not
all walk in the same line.

They spread out and never take

the same route
to the cave twice.

Leaving tracks in the scrub

could give away the location
of the site to poachers,

and priceless material
could be lost to science.

It's going to be tricky
just getting inside the cave.

The only way down
is on a harness and ropes.

The scientists
carefully build a scaffold

at the mouth of the cave

so they can lower themselves
into the darkness.

I mean, it's just a bolt
that holds it...

This will be
the only safe way out

if anything goes wrong.

It's about an 18-meter drop
to the floor,

and then the caverns go on,
you know,

in all directions
for quite a way.

Just go back, when we first
drop into the cave...

For many members of the team,

this kind of exploring is
a completely new experience.

They spend most of the first day
at the campsite

learning to use their gear.

Any mistake could be fatal.

Basically, each time they do
it, they've got to treat it

like it's their life
in their hands.

Use your legs and keep straight.

No matter how experienced
the scientists are,

the winds at the cave entrance
can be treacherous.

Uh, while you're on the rope

or the ladder, you're
often getting buffeted around,

so you got to be very careful
at all times.

Use your legs.

The next three weeks will be

a test of endurance
and patience.

But it's also the chance

for a unique
scientific discovery.

Skeletons in that cave
that we...

You know, this is something

that us paleontologists
dream of every day...

A wonderful new discovery

that we can then go out
and collect and work on.

Tomorrow, the real adventure
will begin.

Time to go, guys!

So you'll each need
one of these.

The moment has come to descend

into the dark depths
of the cave.

Okay, now, just give Eve a hi

and let her know
you're coming down.
Okay, Eve, I'm coming down.

It's a 50-foot straight drop
from the surface.

It's total pitch-black darkness,
mostly totally silent.

You do get a bit of wind
and a bit of air

diffusing through the caverns
and the rocks at times.

But mostly
it's a pretty isolated...

probably about
as isolated and lonely

as you can get
anywhere in the world.

We dropped down,
and we had to go

right to the bottom
of another large cavern.

And then we had to crawl
on our hands and knees

through another
narrow passageway.

This is the first time
I've ever had to work

in really close spaces
in a cave.

And it was
a bit claustrophobic for me.

I had to sort of adapt to it.

Carefully, the team begins
searching the enormous cave.

Fossils are not always

draped on a nice, flat surface.

One has to often, uh, crawl down

between the spaces
between the rocks and come in

from underneath to get
the remainder of the bones.

And sometimes the rocks
are fairly precarious.

So, uh,
there's an element of risk.

This is a good one.

Piece by precious piece,

they start to uncover
ancient bones.

Some are so fragile that
just a touch could destroy them.

See, this would be a major job
to get someone here to just,

with a light brush,
brush away the gypsum,

consolidate the bone.

Yeah, it's beautifully
preserved bone, too.

Now, of course,
if we can find some, uh, teeth

or a bit of jaw or a bit
of skull, that'll enable us

to put a definite identification
on this.

Yeah, I wouldn't come
any closer, actually.

I think there's bone
all through this area.

In fact, um, you know, a whole
skeleton could be right here.

The floor of the cave
is littered with fossils.

Here we have the remains
of giant kangaroos,

three meters high, giant wombats
the size of ponies,

and in addition to that,
we've got weird species...

Kangaroos, wallabies...
Species that are quite rare

and haven't been found
in many other places.

All right, Mark,
when you come back,

can you come down slow, please?

It looks like the cave was
a prehistoric death trap.

Next!

They find many of the bones

directly under the small opening
on the surface.

I can imagine
that a giant wombat,

or a kangaroo
just running along,

didn't see the hole,
fell straight down.

Who knows? All we know is that
in terms of geological time

you only have to have one animal

fall down a hole
every hundred years,

and over the course
of several thousand years,

it mounts up
to a lot of skeletons.

They break for the day,

but there's a wealth of fossils
waiting to be recovered.

And they know that somewhere
under this ancient soil

is the big prize...

The skeleton John Long saw
in the e-mail

before they left Perth.

They only have three weeks,
so time is of the essence.

They have to be as efficient
as possible.

Yeah, I'll get the other guys,
Mark and Jeff,

and maybe Benny into
that new chamber.

Move on to the next one.

Leave no corner
of the cave unsearched.

Bound to be more treasures
hidden there somewhere.

As they continue their hunt,
they find hundreds of bones.

Oh, it's a sacrum.

Many are familiar,

belonging to species
found at other sites.

But then comes
a stunning realization.

This cave holds
hidden treasure...

Unique new skeletons
of extinct species

previously unknown to science.

That is the most
weirdest kangaroo

I've ever seen in my life.

Yeah, I've never seen
anything like that.

Great big...
whacking great horn

sticking out over its eyes.

Bloody devil wallaby.

It's certainly a new species,

and I think there's
an excellent chance

it's probably a new genus
and species...
Wow, that's fantastic.

So it's a major find.
Yeah, definitely.

And the complete skeleton, too.

Over the course of several days,

they realize there's
an entire community

of ancient animals in the cave.

They find eight new species

of prehistoric kangaroo
and other lost animals

that are many times bigger
than their relatives today.

It's an unprecedented discovery.

It's one of the most important
finds ever made

in the history of Australian
paleontology.

There's never been a cache
of fossils of this age.

Complete skeletons scattered
around over the cave floor,

so it's given us
an excellent window

into the fauna
of a massive part of Australia

about which we previously
knew nothing.

Clearly picked it clean,
bloody rooting around...

But just as they had feared,

poachers have been here.

In one part of the cave,
there's evidence

that poachers arrived
before they did

and raided some of the fossils.

So it hasn't taken long for
the cave to start to be trashed.

You've got tire marks
going in there

and then you got tracks
all the way along,

then you go to this cave and
there's been people in there.

Some of the specimens
there were disarticulated.

But not only that, we don't
have the complete picture,

when we start logging and
mapping each, bone by bone,

some of the puzzle's missing.

So it's just not good.

If I had my torch,
I'd have a look around.

Could the poachers
have already stolen

the skeleton from the e-mail?

Hours of searching pass,

and then one member of the team
makes a promising discovery.

I was just coming down
the rock pile here

and I saw down the slots
the larger bones of the legs

and then I came around
to get a better look

and there I saw some bones.

Oh, yeah, look at that.

There are some big bones there
that look like the limb bones,

and also vertebrae
and maybe a bit of hip,

and possibly
the other lower jaw.

They immediately recognize
that these bones

are fragments
of a giant extinct lion.

A tantalizing clue,

but not a complete skeleton.

Then, the moment
they'd been hoping for.

They find the bones
from the e-mail...

The first complete
head-to-toe skeleton

of Thylacoleo carnifex
ever discovered.

I will never forget that moment
as long as I live,

when I first laid eyes
on the Thylacoleo skeleton.

There it was... it was reality,

not just an image
on the computer screen.

I was totally
gobsmacked, just...

entirely exhilarated
from the inside out.

It was a complete skeleton

of Australia's largest
marsupial killer.

Every bone is still in place.

The skeleton has been resting
here in the darkness

for thousands of years.

It was really quite poignant,

because it was possible to tell,
just from sort of looking

at the way the skeleton
was laid out that...

that animal had taken
its last breath

exactly where it was lying,

and you could just imagine it
wandering along in the dark,

um, dying of thirst
or perhaps soft-tissue injuries,

collapsing exhausted and dying.

It was quite remarkable.

It's been a breakthrough day
for the team.

The find is a landmark
in Australian paleontology.

Time for a beer, I think.

There's still a lot of work
to do, and not a lot of time.

They have an intense two weeks
ahead of them,

as they face the challenge
of bringing

the precious skeleton
to the surface.

Deep in the cave again,

they begin to examine the bones
more closely,

and there's more good news.

The skeleton is untouched,

lying exactly where
the animal perished.

It's a pristine find,

it's never been tampered with,

and it gives our scientists
the opportunity

to go in and not only to study
the bones before we touch them

but to take samples
for dating or ancient DNA,

and we know there's
no contamination down there,

and that's very important
for the science.

They take samples for dating,

because they want to know

exactly how old the skeleton is.

It looks so well preserved,
I was thinking

it might only be
a few thousand years,

it might be one
of the youngest skeletons

of mega fauna yet discovered.

They'll also try to recover
ancient DNA from the bones

to help establish how Thylacoleo
relates to modern species.

In modern creatures,

it's easy to take
a tissue sample

and extract the DNA out of it,

but when we look at fossils,
it's often difficult to get DNA

unless you get
very good preservation.

Very nice. Ah!

Look, perfect.

Absolutely perfect.

Unfortunately, we didn't get
any DNA out of those bones,

but then the reason why
became obvious

when the dating results came in.

The skeleton was far older
than we'd ever imagined.

It wasn't a few thousand years.

It wasn't a few tens
of thousands of years.

It was probably half a million
to a million years old.

The skeleton's age
and excellent condition make it

even more valuable
than the researchers had hoped,

providing intimate details

of the extinct lion's anatomy
and behavior.

Absolutely perfectly preserved.

Okay, what I have here is
the first-ever assembled tail

of Thylacoleo,
the marsupial lion.

This is the only specimen known
that had the tail complete.

What we see is it had a long,
muscular and powerful tail,

the sort of tail befitting
an animal

that was an active predator.

Before they can get the bones

back to the lab, they need
to prepare them carefully.

One false move and the precious
Thylacoleo skeleton

could disintegrate
before their eyes.

The skeleton was so fragile.

Now, had someone actually tried

to pick up the skull
at that stage,

it probably would've
just fallen apart in their hands

or fallen to dust because
it was very, very delicate.

They spend days brushing on
a special glue

to harden the bones.

It's a tedious job,
but they have to do it

before they can even pick up
any of the bones.

Are they often as clean as this?

After four days of painstaking
work preparing the skull,

today we're finally able
to pick it up

and look at it in its entirety,

and what we see is
the powerful dentition.

The big, stabbing incisor
at the front,

and this big shearing premolar.

And when we look
at the lower jaw,

we see a similar arrangement.

A powerful, stabbing incisor
at the front

and a shearing premolar
and molar,

which act
like a pair of secateurs

to cut through the flesh
of giant three-meter kangaroos

or big Diprotadonte marsupials.

The skull indicates

that Thylacoleo's bite
was incredibly powerful,

equivalent to that
of a modern lion

more than twice its size.

As the team continues
to explore deeper into the cave,

they find more specimens
of the fearsome beast.

We need a bigger rock.

This is the 11th Thylacoleo

we've found
in these caves so far,

and every specimen gives us
new information

that other material
doesn't show.

This particular animal came down
in the cave

and probably got wedged
right here between the rocks.

The head of the animal was here

and the front part of the arms
fell down here.

The unprecedented haul of bones

poses an unexpected problem
for the team.

They can't possibly take
all the fossils back to Perth.

Even if we took these jaws
and left the rest...

But if they leave
anything behind,

it may not be here
when they come back.

There is this whole question
of cave security

and whether other people
will get in and just pinch bones

and walk all over it.

I'd still feel better
if at least we got some

of the better specimens,

and we mark
exactly where they came from.

Yeah, it's a big job.

It begs the question of:
do you want to get

the information
that's available here out,

or do we want to just scoop
the goodies off the top

and leave it at that?

These fossils haven't even been
studied or described,

and there's
whole new species here,

so the loss of knowledge,
the loss of national heritage

is the main concern to me.

They decide to take the eight
new species of kangaroo

and several
Thylacoleo specimens,

including
the rare intact skeleton.

John Long personally tags
and wraps each fragile bone

for the journey back
to the museum.

We numbered every single bone
in the skeleton,

we took loads of photographs

documenting the relationship
of every bone,

and we very carefully
hauled it up in drums,

on a rope,
to the top of the cave.

But there's still
one final hurdle.

The difference in air pressure

above and below the ground
makes the wind howl

through this narrow opening.

One wrong move and
their precious cargo could be

smashed to bits
against the limestone rock.

Fortunately, their treasure
makes the trip safely.

It's been a long,
hard three weeks.

But the journey of discovery
will take a surprising turn

as they return home
to the museum

to start a new exploration
of Thylacoleo.

With the priceless skeleton
back in Perth,

John Long's colleagues from
the Western Australian Museum

join the investigation.

In the lab, they'll be able
to conduct a meticulous study

of Thylacoleo from head to toe.

Finding a complete skeleton
of a marsupial lion

is far more important than
having hundreds and hundreds

of isolated bits and pieces
from different localities

because, for a start, we can
build up an accurate picture

of what the animal was like
and its real proportions,

and we can also start to look at
its functional morphology...

How that animal operated
as a creature.

You know, how did its
feeding mechanism work?

How did its hands and feet work?

How much movement was there in
its shoulder and its backbone?

And from these studies,
we can then start to build up

a realistic idea of Thylacoleo
as a living animal.

19th-century naturalists
were the first to identify

and describe Thylacoleo bones.

And even with only fragments
to go on,

they realized how unusual
a creature it was.

Sir Richard Owen described
this animal back in 1859,

the time Charles Darwin had just
written his book on evolution,

as "The Fellest of
Predatory Beasts,"

and he called it
Thylacoleo carnifex.

"Thylacis" for pouch,
"leo" for lion,

"carnae" for meat
and "fex" for cutting.

So this was the meat-cutting
marsupial lion.

But the name raised more
questions than it answered.

Marsupials share
the characteristic feature

of a pouch the females
use to nurture their young.

The specific bone structure
needed to support a pouch

in marsupials has been found
in Thylacoleo skeletons.

Some marsupials live
in other parts of the world,

but Australia's
geographic isolation

contributed to the evolution
of many unique species

like wombats, koalas
and kangaroos.

So the perplexing question is:

How did Thylacoleo, the extinct,
meat-cutting lion,

come to share features of
both marsupials and big cats?

This is one of
the most fascinating

mammals, I think,
that's ever been discovered.

It's an animal that's
full of paradoxes;

there's nothing quite like it
that exists

anywhere else in the world.

Rod Wells has been
studying Thylacoleo

most of his career.

The best fossils
he's had up till now

are bits and pieces
of skulls and teeth.

So he starts his investigation
of the new, complete skeleton

with the parts he knows best,

and right away,
he finds surprises.

This huge, single cutting tooth
here, or premolar tooth,

and this large premolar tooth,
cutting premolar tooth up here

are unprecedented
in the mammalian world.

If we go to the front
of the jaw here,

we have these two front teeth
that extend here,

a condition that is
known as diprotodonte...

"Di" for two; "proto," front...
Teeth: two front teeth.

And this is the condition
that we find

in all of the marsupials
that are herbivorous.

Things like possums and wombats

and kangaroos
and koalas all have

this diprotodonte condition.

So here we have an animal
that seems to be

telling us with one set of teeth
that it comes

from a herbivore ancestry,
and with another set of teeth,

it's telling us
it's a carnivore.

Most of Thylacoleo's
marsupial relatives today

are plant eaters,

but it seems clear that it was
a hunter, like other lions.

To figure out
this contradiction,

the scientists have to look
beyond its teeth.

I'd like a high-
resolution scan.

One-millimeter slices.

Since this skull
is so well preserved,

it promises to deliver clues

that have eluded
previous researchers.

Mark Walters is
a doctor who uses

forensic techniques to rebuild

shattered human faces
and skulls.

Today, he's using a CT scanner

for a different kind
of detective work.

For the first time, he will peer
deep inside Thylacoleo's skull

and try to reconstruct
the creature's ancient brain.

See the very dense bone
at the top of the skull.

CT data provides us
a stack of images,

and we can bring those
into the computer,

and then we can create
geometrical files.

And from those
geometrical files,

we can do a number of different
types of manipulations,

including taking a cast of the
internal surface of the bones.

The CT images are transformed

into a plastic replica
of the skull.

Then, Walters takes a set

of precise measurements
of the interior cavity.

The final result is a remarkable

three-dimensional cast
of Thylacoleo's brain.

There's a lot of information

that can be derived
from such a cast.

We can see quite clearly
the lumps and bumps on the bone,

and they correspond to
different parts of the brain.

Well, the very first thing
and obvious structure

is that we see these
very large olfactory lobes.

So this animal is
going to be able to detect

specific smells
over very long distances.

Also, we can see
the parts of the brain

associated with sight.

And we can also see the big
nerves that go to the eyes.

And these nerves are
quite large, so you can see

these animals also required
a lot of good vision.

So what we can quickly see
by this cast of the brain

is that this animal had
a very powerful sense of smell;

it also had
a good sense of hearing

and a very good sense of sight.

So it was using
all of its senses

in its day-to-day activities.

Many of today's marsupials
are night creatures

with keen senses of
smell, sight and hearing.

These are traits
also shared by big cats.

With its powerful bite,

Thylacoleo must have been as
fearsome a predator as a lion.

But the question of
how it hunted is complicated

by the strange configuration
of its teeth.

Now, the problem with that is,

of course, is how it actually
catches its prey.

Because, in effect,
these diprotodont teeth,

when they mesh with the other
upper incisors here,

form something analogous
to a parrot's beak.

This animal could puncture
a hole in the prey quite easily,

but it would never be able
to hang on to its prey.

Somewhere in the new bones

could be a clue
to solve this problem.

If Thylacoleo stabbed
its victims

with its large front teeth,
how did it hold onto them

while it finished them off?

The researchers find an answer
in a part of its body

they've never before
been able to study in detail.

And here you will see

the very large slashing claw
on the thumb.

So here was a mechanism whereby

this animal could capture
and hold its prey.

So once Thylacoleo
has grasped its prey,

it's then in a position
to deal the death blow.

And it can deal the death blow

with these sharply pointed
lower incisor teeth.

And of course, this would be
an ideal way of doing things

like severing the spinal cord

or suffocating the prey
by grasping around the trachea.

The evidence suggests that

this ancient marsupial lion
is fundamentally different

from other marsupials,
which lack such powerful teeth,

and from other lions,

which don't have
its slashing claw.

But without obvious parallels

to these
familiar predators today,

its hunting habits
remain a mystery.

Did Thylacoleo chase its prey?

Did it hunt in packs?

Or was it a stalker,

lying in wait for
the best moment to strike?

The scientists turn again
to the new skeleton for answers.

Each bone is carefully scanned,

so that 3-D images
can be manipulated

on a computer screen.

Oh, this is terribly exciting,

because this animal
doesn't exist,

there's no other animal
that exists like it.

Through using
this type of technology,

we can reconstruct
the anatomy of these animals

to a detail that we've
never seen before.

These images help decipher

how the bones were
connected to each other

and where muscles
would have been attached.

This gives the scientists

a new understanding
of Thylacoleo's legs

and an important detail
about the hunting techniques

of the ancient predator.

There is nothing in
the back part of the skeleton

to suggest this animal was, in
any way, a fast-moving animal.

The hind legs are low-geared;
they're powerful.

And indeed, if we look
at the position

where the muscle,
the muscle scar,

where the muscle
comes off the thigh bone

for rotating the thigh
about its fulcrum point here,

it's attached way down here,

so it's a very, very low-geared
and powerful hind limb.

Legs that are powerful

but low to the ground mean
Thylacoleo couldn't run fast

for any significant distance.

Chasing its prey would be out
of the question...

It would never
have enough speed.

So I think this animal, really,

is one that carefully
stalks its prey.

The speed comes with the speed

with which it can slash
with that forearm.

As all of the new information

about Thylacoleo's anatomy
is falling into place,

a scientific illustrator

begins reconstructing
its size and shape.

The only things left
to artistic license

are the color
and markings of its coat.

With the finished drawings
as a guide,

a scaled-down model of
Thylacoleo slowly takes form.

Lasers scan the completed 3-D
model to produce digital images.

And finally,

the lost prehistoric predator
comes back to life.

It was a fierce and stunning
beast with a crushing bite

and powerful legs...

But it was low to the ground
and heavy, not built for speed.

Its feet had claws like a lion,
but it walked flat like a bear.

Since it was slow-moving,

and probably able to use
its claws to climb trees,

it may have ambushed its prey
like some big cats today...

Laying in wait from above

and then springing down
on an unlucky victim.

And there's one
final, dramatic clue

that seals its image
as a deadly predator.

The clue comes from the tail

they discovered intact
in the cave.

One of the interesting features

of the tail is that... are these
little tiny bones here,

these little V-shaped bones
that are called chevrons,

like on a roof, a chevron.

And what they actually do is
they protect the blood vessels

that run underneath the tail

at the point where the tail
flexes down to the ground.

This is the sort of thing
that you see in kangaroos

and kangaroos are capable

of propping themselves up
on their tail...

Tripoding, if you like, with
the tail and the two hind legs.

If this animal is
actually catching its prey

with its front legs
and its slashing claw,

being able to tripod back
on the tail and the hind feet

frees up the arm
for slashing or grasping.

I have absolutely no doubt
that an animal the size and bulk

of Thylacoleo could have
pulled down much larger animals,

bigger than itself, like
a giant wombat, Phascolonus...

The size of a small car...

Or giant herbivorous kangaroos.

That's the sort of creature

that would have been fodder
for Thylacoleo.

My perceptions, at this moment,

are of a opportunist carnivore
scavenger that hunted at night;

probably operated
in woody shrub lands.

I wouldn't want to have been
a leaf-eating kangaroo

with one of these guys around.

Um, I would imagine
that he operated on his own.

Probably sneak within very close
range of the prey

and then leap at it...
Now, either

leap directly at it and grasp it
with those big claws,

maybe slash at it
with the big claws,

maybe leap onto its back

and sever the spinal cord
with the incisors.

And then just, just sit down and
sheer off great lumps of flesh.

I would imagine, if there were
any dead animals around,

this guy has got
a very good sniffer.

It would probably
pick up the smell

of carrion very easily.

I think it would be quite
a fearful animal to encounter.

Thylacoleo ruled
the Australian outback

for more than a million years.

Of the many large and formidable
prehistoric animals,

it was the deadliest...
The king of beasts.

But toward the end
of the ice age,

something toppled Thylacoleo
from its throne

and drove it into extinction.

How did this powerful killer

that could attack animals
many times its size

become a victim?

People always think
that big predators are like

the top of the heap, the king of
beasts, the king of the jungle.

And in fact,
those big predators...

Particularly ones
that are highly specialized

and just eat meat...
They're very vulnerable.

Scientists are sharply divided

about what caused Thylacoleo...

And all the other giant animals
in Australia... to die out.

One view is that the final
climax of cold conditions

toward the end of the Ice Age...
30,000 years ago...

Pushed the great creatures
into oblivion.

If you go into a maximum ice age
and out of it again

in the period of 10,000 years,

then you could certainly have
major changes that put pressure

on the environment
and the animals that live in it.

But a rival theory places
the extinction much earlier,

around 50,000 years ago.

At that time, climate changes
were probably less severe.

And the first humans to arrive
in Australia...

The ancestors of today's
Aboriginal people...

Were entering the continent.

If we look at what was happening
in Australia 50,000 years ago

or so, we can see
a relatively stable climate,

not that much different
than today,

and we also see that that's when

the first humans colonized
Australia.

And so it raises the question:
could it be a human impact

that's the main driver
for these big extinctions?

There's no way to prove
that humans hunted

prehistoric Australian animals
aggressively enough

to kill them all off.

But other human activities

could have helped
eliminate the beasts.

When humans come to Australia,

we know they have fire
on demand.

And so that's one of the tools

that people use
in modifying landscapes

to their benefit.

And humans burn
for a whole range of reasons.

I mean, partly, they... they
just burn to clear the land

so that they can move across it.

They hunt along the fire front,
they signal distant bands,

they promote the growth
of plants

that respond after burning.

So there's many reasons
why humans might be burning

the landscape in a way that they
thought was a positive impact.

Whatever the reason,

burning could have disrupted
natural cycles

of wildfire and regrowth,
changing the vegetation

and altering the habitat
the giant animals depended on.

Fires set by humans would narrow
the range of plants

to fire-resistant species.

The landscape would turn
to desert scrub land,

and many of the browsing
animals... like giant kangaroos...

Wouldn't have enough food
to get by.

A predator like Thylacoleo

that couldn't suddenly switch
its diet or hunting habits

would be highly vulnerable
as its supply of prey dwindled.

If the humans reduce the prey...

That is,
these other large browsers

on which the big carnivores
are dependent...

The carnivores are very
sensitive to prey abundance.

And Thylacoleo, which is not
a running animal...

It's an animal that depends

on its prey walking by
underneath it,

so it can leap down on it,
where it's extremely efficient...

But if it reduces
the number of potential prey

below a threshold,

then Thylacoleos will starve
to death.

It's sort of like a snowball
rolling uphill, if you like.

Um, the big predators
are the ones

who are going to feel
any effects first,

because they're the ones
on top of the pyramid,

and they're dependent
on everything below them.

But exactly how big a role
humans played

in the extinctions,
alongside climatic factors,

is still hotly debated.

And not only in Australia,
but on other continents,

where a similar pattern
of extinction unfolded

as the Ice Age ended
and humans arrived.

This question is much larger
than Australia

because one of
the characteristics

of the last 100,000 years
is the disappearance

of almost all the large animals
almost everywhere on the planet.

And the one piece of evidence

that's consistently present
in all extinction cases is

that they occur
about the same time

that humans first appear
on the landscape.

I think the lesson to be learned
for the current day is

that these big animals are
very vulnerable.

We think of them, because
they're big and powerful

and could kill us, either, you
know, on purpose or by accident,

as being these strong kind
of survivors.

But they're very fragile.

And once they're gone,
they're gone.

Long after
the magnificent skeleton

takes its final resting place

on proud display at the
Western Australian Museum,

research will continue on the
unique role Thylacoleo played

in the natural history
of the outback.

And the scientists who found it
believe this is just

the beginning of many more
discoveries.

If you pause for a moment
and think about Australia,

what is Australia's
great heritage?

Australia's great heritage is
its flora and its fauna,

and its marsupial fauna is
absolutely unique...

And this is the biggest
marsupial carnivore

that ever lived
on this continent.

I think the discovery all out,
not just the Thylacoleo,

but including everything
we found in those caves,

was a quantum leap
in our knowledge

of Australian megafauna
of that age.

Looking back
on those halcyon days

of the Thylacoleo expedition,
it was one of the greatest times

of my career
as a paleontologist...

Certainly one of
the most exciting times...

To be able to go out,
launch an expedition,

go down those caves, and
find these wonderful skeletons.

It was just the most
amazing thing.

Every paleontologist dreams of
something like that happening.

There's still a very big part
of my heart is still