All language subtitles for BBC Extinct a Horizon Guide to Dinosaurs Eng

Dinosaurs.

Masters of the planet
for 160 million years.

The biggest, baddest animals
ever to walk the Earth.

They had claws a foot long.

And enormous, bone-crushing jaws

with teeth the size
of carving knives.

Weighing up to 80 tons,
the ground would literally shake
when they moved.

But how do we know
so much about them?

For over 40 years,
Horizon and the BBC have followed

the world's palaeontologists
on their quest to find out

what these elusive creatures
were really like.

As a palaeontologist,
I love digging up the possibility

of monsters of my childhood,

looking for strange beasts
that once roamed where I live now.

Over time, with only bones
and tiny fragments of information

to go on, scientists have managed
to piece together

the complex jigsaw puzzle
that is the life of the dinosaurs.

There have been astonishing
new finds,

controversial theories...

And extraordinary revelations
about these giant reptiles.

Quick, agile, fast-moving.

15,000lbs of gut-crunching terror.

These tantalising clues
and breakthrough new technology
have enabled scientists

to reach for the answers
to the biggest questions of all.

Do we really know
what happened to the dinosaurs?

And is there a chance that some
might still be alive today?

When Horizon first began reporting
on dinosaurs over 40 years ago,

palaeontology was a science
based on a lot of speculation

and not that much evidence.

Scientists really had just bits
and pieces to go on.

So it's hardly surprising that the
dinosaurs we came to know and love

were really just a mixture of fact
and fantasy.

The largest flesh eater
the world has ever seen.

I'm not afraid!

All children now learn
at an early age,

but are reluctant to believe
that tyrannosaurus

and all the other dinosaurs followed
a well-trod trail to oblivion.

I see a little hole up in his nose.

They've heard other stories
about dinosaurs too,

many of which are myths,

replacing the fairy stories
of earlier generations.

For our limited knowledge
of these pre-historic monsters

provides numerous questions,
but very few answers.

CHILDREN LAUGH

Look at that. Nine feet tall.
What a monster.

For years, scientists had grappled
with fundamental questions.

They didn't know what dinosaurs ate,
how they bred.

Sometimes they weren't even sure
how the skeletons fitted together.

They also couldn't work out

whether one of the major
groups of dinosaurs,

the sauropods,
lived on land or in water.

But one of the first major finds
covered by Horizon

revealed evidence of sauropod
behaviour frozen in time.

Footprints.

In the bed of the Paluxy
river in Texas are tracks made

by dinosaurs 70 million years ago,

when the hard limestone rock was mud.

This is evidence that convinces
the most doubting tourist.

Some are tracks of the meat-eating
dinosaurs,

Others of the heavy, long-necked,
long-tailed dinosaurs.

It is these which pose a problem.

Were the creatures who made
these tracks swamp dwellers,

or did they move around on land?

30 years ago, the river was dammed
and the tracks photographed

and carefully plotted.
The shallowness of the footprints

and the absence of tail marks
suggested a herd of the animals

living in water sufficiently deep
to keep their tails out of the mud.

It's difficult to believe
that such huge creatures

weighing up to 80 tons could
support themselves out of water.

But here is evidence for just that,
a tail mark.

If these creatures could support
themselves out of water

on one occasion, couldn't
they be ordinary land dwellers

who occasionally ventured
to the swamps?

At the time, a single tail mark
was not enough to convince

the palaeontologists that sauropods
were anything but aquatic.

But as more skeletons
were discovered,

their similarities to animals
living on land became clearer.

So then we have long straight limbs
and a long neck,

adaptations not for a hippo-like
existence,

but for living on land,
feeding high on trees.

Scientists looked again
at the fossil footprints...

And turned to living animals to try
and determine how fast

the sauropods could move.

Dinosaur bones are only one source
of information.

Present day animals are another.

Neil Alexander is Professor
of Zoology at Leeds University.

His main research interest
is analysing how animals move.

Recently he's found a way of applying
his work

to answering a seemingly
impossible question.

How fast did dinosaurs walk?

On the beach at Southport,
some vital evidence was laid out.

These are replicas of some of
the biggest footprints ever found.

They were found in Texas,
and they're not new footprints.

They're footprints made something
like 100 million years ago,

preserved as fossils.

Now, these big fellows,
these are the hind feet.

It was a four legged animal,

and these hind feet

are about three feet long.
Stride length here of eight feet

from right hind foot down
to right hind foot down again.

The dinosaur footprints are only
part of the information needed.

Now something called a Froude number
has to be worked out.

It's a mathematical formula relating
the size of an animal's legs

to the way its stride increases
as it moves faster.

Now we're going along
at about five miles an hour,

and the horse is walking.

Each foot is moving
in its own time.

There are no two feet
going together.

We're going to speed up a bit,
and then you'll see the gait change.

If we go up now to about ten miles
an hour, there we are...

The diagonally opposite feet
are moving together.

Now if we speed up again
and go further, there we are...

Going through a canter
into a full gallop.

In the gallop, we've got the
two forefeet moving about together,

the two hind feet moving, again,
about together.

And now we must be going
at something like 20 miles an hour.

Professor Alexander has studied
dozens of animals,

from tiny gerbils to huge elephants,
and worked out their Froude numbers.

From these, he's able to estimate

what the Froude number
for any animal of any size will be.

And so we find out what the Froude
number is for the dinosaur,

and how fast the dinosaur was going.

And it's awful slow.

Two miles an hour.

Now, two miles an hour,
that's a slow walk for a man.

For something with legs
three times as long as a man,

it's a very slow walk indeed.

Professor Alexander's work
had reinforced the widely held view

that dinosaurs were slow,
lumbering reptiles.

But the discovery of
a new kind of dinosaur

would change our thinking.

We have right over here
one that I discovered myself,

which I think is one of
the most interesting dinosaurs

that's ever been found.
In fact, I also think

it's one of the most important
dinosaurs ever found.

Let me show you
some interesting things

about this fellow. First of all,
it's a carnivorous dinosaur.

But not a big one
like tyrannosaurus,

it's just a little fella,

probably about four or five feet
high,

maybe about eight or nine feet
in length.

Weighed maybe about 175 pounds,
about your weight or mine.

One of the curious things about him
is the construction of his foot.

And the peculiar thing about this
is the very large, sickle-like claw

on the one toe.

And remember that in addition
to this long bony claw,

there was a horny sheath
that fit over that

so that the total claw
was probably half again as long.

Obviously not designed for walking,

and quite certainly
an offensive weapon.

This strange structure

which we had never seen before
in any of the carnivorous dinosaurs

is the reason I coined
the name for this that I did.
Terrible claw. Deinonychus.

But he was a fella

I wouldn't want to meet on a dark
street at night, I'll tell ya.

John Ostrum realised Deinonychus
was a ground-breaking dinosaur,

one that overturned long-held ideas
about how they moved.

So the picture that we get
from Deinonychus

seems to be completely different

from the old picture that we had
of dinosaurs as sort of sluggish,

sun-basking animals
like modern lizards

and turtles. Deinonychus
seems to be a very quick, agile,

fast-moving, two-legged predator.

Good balance control means
a high neurological development.

This discovery is what sort of
pushed me over the brink

into looking at dinosaurs
in a whole new light.

Other dinosaurs too were suddenly
seen as fast-moving, agile creatures.

And Ostrum's new ideas about them
developed like this.

In the animal world, there's
a major division. In one group,

there are mammals which are active,
hot-blooded creatures.

In the other are reptiles,
which are generally less active

and cold-blooded.

Where do dinosaurs fit?

Since like mammals,
they were very active,

Ostrum reasoned perhaps
they were hot-blooded too.

This idea was revolutionary.

Was it really possible
that dinosaurs,

ancient reptiles,
could be warm-blooded?

It would be another 30 years
before deep bone analysis

revealed that he might be right.

For years, palaeontologists
have been looking

at the outsides of dinosaurs.

+On the outsides, we can understand
how dinosaurs evolved

and their anatomy changed over time,

but deep inside the bones,
we can trace dinosaur life.

By analysing thin cross-sections
of fossilised dinosaur bone,

Kristi Curry Rogers
is helping to rewrite

what we know about dinosaurs
from the inside out.

I think let's go with this one.

And the smaller one.

Those two look good. OK.

One of the things we see

when we crack open dinosaur bones is
a story of a very fast growth rate

throughout life history.
We see that dinosaurs

were growing very, very quickly on
a par with modern mammals and birds,

not like reptiles at all.

This is a great example
from a young Apatosaurus,

a young, large sauropod dinosaur.

All of these white spaces we see
are places where blood vessels

used to flow through this bone
when the animal was still alive.

This is completely different
than the bone

we might see of a reptile,
like a crocodile, or a turtle.

Instead this is lot more similar
to those bones of mammals and birds.

What she's discovered from deep
within the dinosaur bones

has reinforced the idea
that at least some of them
were warm-blooded.

Dinosaurs, just like other
modern animals,

probably were fairly well adapted
for whatever
thermoregulatory strategy.

I think they were
perfectly well adapted to deal

with the problems
of maintaining a body temperature.

Advances in technology
were allowing scientists
to break new ground,

proving that dinosaurs
weren't just giant lizards

but a truly unique kind of reptile.

But like a detective
looking for clues,

finding a whole dinosaur skeleton
was the palaeontologists' dream

and, in 1990, an American
fossil-hunter hit the jackpot.

For Pete Larson, and his then
girlfriend Susan,

the day had started as an ordinary,
everyday fossil hunt.

We were out actually digging
on a triceratops skull

that my ten-year-old son Matthew
had found.

We were just having a grand old time,
it was a very nice, small
triceratops skull.

And all of a sudden, Susan walks up
with a couple of bone fragments.

And I said, "Is there more?"

And she said, "There's lots more."

Nothing could have prepared them
for what they'd found.

I looked up the face of the cliff
and saw an expanse
about eight feet wide

and perhaps two feet deep
with bones jutting out everywhere.

And as I crawled up
to the top of this exposure,

I saw three articulated vertebra.

I knew they had to come from a T rex
because of the size of the curve
of those bones,

they were obviously
parts of vertebrae

from a meat-eating dinosaur.

And when I saw those three
articulated vertebrae,

I knew this was going to be the most
important specimen we'd ever dug up.

I just knew it.

Pete Larson marvelled at the size
of the partially-exposed
killer dinosaur.

And nicknamed it "Sue"
after his girlfriend.

It was like clawing our way
to the top of Mount Everest,

and as we were uncovering it,
we could see the top,

and as we got her out of the
ground, we were there.

We had climbed
the Mount Everest of palaeontology.

We got the biggest, baddest of all
the T rexs that ever was.

And it got even better.

Sue was extremely well preserved
and nearly complete,

exactly what Pete Larson
had dreamed of finding.

At long last, here was a chance
to study the world's
ultimate killing machine

in extraordinary detail

and all from just this one specimen.

Deep within Sue's
well-preserved skull,

scientists were about to discover
something they'd never seen before.

And cutting edge technology
would allow them to see it
in exquisite detail.

Basically, when it comes down to it,
I was told to describe
the thing inside and out

I took that literally.

I knew they wouldn't let me break
the skull apart

so CT scanning is the answer.

CT scanning is an advanced
x-ray imaging technique.

It allowed Chris Brochu to build up

computer images of
slices through the head

which he moulded together to produce

a three-dimensional likeness
of a T rex skull.

Then, painstakingly, millimetre by
millimetre, he followed the contours

on the inside of the skull to reveal
the structure of a T rex brain.

The first time I saw
the individual slices themselves,

they didn't seem all that exciting.

It wasn't until I built
the first animation,

the first flip through a bunch of
slices all going through the skull,

that was when it really struck me

that there were a lot of things
here to see.

The CT scans revealed something
scientists had never before been
able to see in such detail.

Protruding from the delicate network
of brain tissue,

was the optic nerve.

This nerve was
responsible for relaying information

from the eyes to
the visual centres in the brain.

And it was big enough to carry
a LOT of information.

The scans seemed to confirm T rex
did indeed

have a key attribute
of a skilled predator.

It would have been able to seek out
its prey at a distance

and destroy it with
the accuracy of an assassin.

T rex could see its prey, but
that didn't automatically make it

an efficient killer.

To get to grips
with its enormous jaws,

scientists devised
a risky experiment.

Watcha, watcha.

Gators and crocodiles
make a great model

for studying
the feeding biomechanics

of extinct theropod dinosaurs.

They have very similar musculature,
and the basic leverage of their jaws

and things like that are just a good
analogy for tyrannosaur feeding.

OK, grab that pole!

Let's go.

Watch your feet, watch your feet.
Remember she can run forward.

One, two, three...go, go, go!

Watch your feet, Ray.

This is a female American crocodile,
Stevie.

A youngster at 31 years old, she's
only half the size she could become.

She may be small,
but her strength is obvious.

Stay in line with her.
Back up, back up, back up!

Back up. Who's got tape?
I have tape.

She's heavy.

Because her jaws are thought to
work in a similar way to T rex jaws,

Erickson plans to measure her bite
to see what it may reveal

about the power
behind a T rex bite.

Yet, as she's small
and he's not tested her before,

he has no idea what
kind of results he'll get.

All the way with that...

I'm all set.

Erickson needs to get the crocodile
to crunch onto

a specially-designed
pressure sensor,

which will record the force
of the bite.

OK, everybody ready?

The tricky bit is getting
the timing right.

The bite needs to be
a spontaneous one.

Here we go. Hang on.

819lbs. Good bite.

An 800-lb bite is comparable to
what a lion could do or

a spotted hyena, which is the bone
crushing champion among mammals.

A very small crocodilian is
capable of doing bite forces

equal to what some of
these large carnivoran mammals do.

If you matched up an equal-sized
crocodile say to a large lion,

the crocodile will bite three times
more forcefully.

Watch your legs.

If jaws like these give
crocodiles a bite force

well above what their weight
implies,

then Erickson believes the same must
have been true of T rex jaws.

His work suggested
the power of a T rex bite

may have been on a scale beyond
anything we have ever seen.

It's not a natural thing

to stick your hand inside
the mouth of a crocodile, but...

Probably shouldn't
try this at home, kids.

To get an idea of how much
more powerful,

Erickson worked on doing more than
just scale up the bite.

Snout width is 14.2.

He measured every physical detail
of his crocodiles to try to map

the differences in skull shape
and body weight

compared to an animal
the size and shape of a T rex.

50.2 head length...

Erickson's preliminary maximum
estimate of a T rex bite

could be as much
as 40,000lbs of force.

That's about 50 times more powerful
than our crocodile.

T rex would have had easily
the most powerful bite

of any animal that has ever lived.

The combination of new finds
and advanced technology

has enabled palaeontologists
to interpret fossils

with greater certainty.

We now know more than ever before

about what dinosaurs looked like,

how fast they grew,
their skill as predators,

and how they moved.

All building a convincing picture

of how the dinosaurs came
to dominate the Earth

for over 160 million years.

160 million years
is a pretty long time

and makes dinosaurs some of the most
successful animals

ever to have walked the Earth.

After all, modern humans have
only been around for
a couple of hundred thousand years.

Evidence of dinosaur life fills
the geological record

but then suddenly,
65 million years ago,

it all disappeared.

The dinosaurs vanished.

Scientists spent years scrutinising
dinosaur bones, looking for answers.

You got something?
Yeah, this is a vertebrae...

They struggled to come up with ideas
to explain the mass extinction.

Perhaps the climate deteriorated,
becoming too hot...

..or too cold.

Or suddenly too wet...

..or too dry.

There were problems
maybe of reproduction

or maybe their eggs were
eaten by the tiny furry mammals.

IT BURPS

Maybe it was God's will or
lack of standing room in the ark.

But it was only when they turned
their attention to rocks,

rather than bones, that scientists
had a breakthrough.

Geologists searching for clues
to the extinction discovered

an unusual layer of clay in
the geological record that marked

the boundary between the time of the
dinosaurs and the time of mammals.

Nobel prize winning physicist
Luiz Alvarez and his team

took up the challenge.

You see this clay layer here,
about a half-inch thick.

That's when the dinosaurs went out.

We really don't know how long
it took, why it's there.

So I said, "Maybe some of the tricks
I know as a physicist

"might help unravel that story."

And we talked about it
for the next couple of weeks

and finally decided to look for
iridium

as a measure of the deposition rate.

A small quantity of the metal
iridium

constantly falls to Earth
from space,

and the team
expected to find only trace amounts.

But their tests showed
something astonishing.

There was so much iridium in
the clay layer

there could only be one source.

Alvarez's radical idea was that
it had been brought to Earth

by a meteorite.

The vast majority of iridium-bearing
meteorites started life as asteroids.

Most of them, in an orbit between
Mars and Jupiter,

never come anywhere near the Earth.

But the theory goes that a few
are occasionally

swung out of line by the enormous
gravitational pull of Jupiter.

A very few of these finish up in
an orbit which crosses the Earth's.

Most of time they pass harmlessly by,
but every now and then, they collide.

Alvarez's theory is that
65 million years ago a huge asteroid,

six miles wide, smashed into
the Earth with devastating effects.

It was this collision, he believes,
that covered the Earth with iridium

and wiped out the dinosaurs.

It's not all that far-fetched.

Only 25,000 years ago,

a much smaller collision caused
Meteor Crater in Arizona.

There are larger impact craters
on the Earth's surface.

Many have been eroded away over time,

and are rather difficult
to recognise.

Nevertheless, so far, over
the whole world, more than 200

have been identified,

but none of these is both the right
age and size for Alvarez's theory.

However, there's an alternative.

The asteroid may have landed
in the sea.

Dr Cesare Emiliani.

We have no evidence at all

of a crater of the size that
this asteroid this should have made

either on land or on
the ocean floor.

This is a map that shows
the structure of the ocean floor.

On the other hand,

we have evidence indicating
that plant life on the continents,

in a broad area ranging from
the Urals to the Rockies,

suffered somewhat,
at the end of the Cretaceous.

While plant life west of the Urals,
from the Urals to the Rockies,

around the North Atlantic,

suffered very little
or nothing at all.

That would seem to indicate that
the point of impact of the asteroid

was somewhere between
the Urals and the Rockies.

We have no crater on land, we have
no crater on the visible ocean floor

but a portion of the ocean floor
since then has disappeared
under the continent.

Because the oceanic crust moves
towards the continents

and then dives under the continents.

There is a substantial chance that
the asteroid

might have hit an area
of the ocean floor

that has since disappeared.

If one were to make a wild guess as
to where the asteroid may have hit,

one would say somewhere in
the North Pacific, round here.

Without finding a crater,
it was hard to prove that it was

an asteroid that had
killed off the dinosaurs.

But, by 1997, scientists realised

they'd been looking
in the wrong place.

A number of circular structures
had been found in the Caribbean.

The shape of islands, circular
structures on the sea floor,

circular geophysical anomalies.

When you're looking for an impact
crater, usually the obvious thing,

because most craters are round, is
looking for something big and round.

One of Hildebrand's suspects was on
the Yucatan peninsula of Mexico.

There the state oil company,
Petrolinas Mexicana, had detected

a strange circular anomaly
in the Earth's gravity field.

Chixulub, the dead centre
of the big round hole,

but at the surface there's
no sign of a catastrophe.

The 200km-wide crater is hidden.

It's buried hundreds of metres
beneath the Earth's surface,

so Hildebrand had to investigate it
in some other way.

We've taken another 1,400
measurements and combined
them with the data that

Petroleos Mexicanos already had to
make this map of the gravity field.

Here you can see all this
concentric circular structure

that represents the crater.

From here to here is about 180km.

Petroleos Mexicanos had known
about this big buried structure
for decades.

They'd drilled several wells into it
for oil exploration,
beginning in 1952.

When they did so, they found what
they thought was volcanic rock.

But this contains shock quartz
and impact glass and so on.

These are the classic signs,

the deposits you'd expect
in a big impact crater.

The rock proved to be precisely
65 million years old -

the age of the mass extinction.

Here at last was the first
confirmation that Chicxulub
was ground zero.

Hildebrand confirmed the theory
proposed 17 years earlier

that a devastating asteroid had hit
Earth 65 million years ago.

By 2004, scientists believed they
had proof that the impact

had caused a massive explosion...

..quickly followed by an enormous
shock wave that had destroyed
life for hundreds of miles around

And there was more.
Investigations of the layer of rock

that marks the time when
the dinosaurs disappeared -

known as the KT boundary -

revealed further evidence of what
had happened in the aftermath.

These are called spherals.

They're actually made of
round rock globules,
so we know they're condensed

from a very hot vapour cloud.
And some of the mineralogy in there

tells us these globules originated
at very high temperatures.

That's exciting.

You know something hot happened
and hot is associated
with an impact.

The spherals were evidence
that the fireball had vaporised

billions of tons of rock.

In outer space, the vapour condensed
into tiny droplets which fell back

all over the Earth
as white hot spherals.

From America to New Zealand
there seemed to be

evidence of massive burning
at time of impact.

It looked as if the world's forests
had spontaneously ignited,

as the spherals heated
the atmosphere by up to
1,000 degrees centigrade.

If we're looking at 600, 1,000
degrees, then this would instantly

have ignited all the plant matter
across the world

and it just would have
been sent up in flames.

The impact was also thought
to have created vicious acid rain.

The fireball had release chemicals,
which turned the water deadly.

It was suggested that
the acid rain had a pH

so low it was like battery acid.

If you had something that low,

it would literally burn
everything on the land

from plants, to dinosaurs
to everything else.

Then there was the final clue
from the KT boundary -

a high concentration of fern spores.

Ferns flourish whenever all other
plants have been killed off by
some environmental devastation.

So the predominance of fern spores -
known as a fern spike -

suggested something had wiped out
every plant on the planet.

Fern spikes were found all over
the world, such as in New Zealand.

This, I think, became stronger
and stronger evidence

that there was something LIKE
global darkness caused by an impact.

So the theory grew up
that vast amounts of dust
created by the impact

must have blocked out the sun.

This could have plunged
the world into freezing darkness
for months or years.

Any dinosaurs that escaped burning
either froze or starved to death.

The mystery surrounding the death
of the dinosaurs

finally appeared
to have been solved.

A number of factors may have
influenced the extinction,

but research had shown that
the impact at Chicxulub
WAS the crucial factor.

We should probably be thankful
for that mighty asteroid -

if the dinosaurs hadn't
been wiped out,

mammals may never have flourished
and we might not exist.

So what would have happened if
an asteroid hadn't hit the Earth

and the dinosaurs had survived?

It's a thought that's given rise
to some novel ideas.

I think that some dinosaurs, like
some mammals would have become

increasingly intelligent
at a geometric rate,

as did our own ancestors,

and I think, possibly, by this
time the dinosaurs themselves

would have approached our own level
of brain development.

A sculptor at our museum

and myself have collaborated over
the last several months in trying

to estimate what the appearance
of one of these highly encephalised

or intelligent dinosaurs might have
been, a dinosaur for the 1980s,

and here is an example of what
we think it may have looked like.

Their model of a 20th-century
dinosaur incorporates

many features of the original
reptiles - the binocular vision,

the absence of an external ear,
a deep chest cavity with ribs

all the way down the abdomen,

opposable fingers and
no external genitalia.

But it looks closer to a human being
than a brontosaurus.

In building it, have they perhaps
unwittingly favoured our own kind?

I don't think so.

I think just as the birds,
bats and flying reptiles all have

a crudely avian form, so too there
is a meaning to the human form.

So that we are, in effect,
adapted to interact with

an environment as highly
encephalised bipeds

or walking animals with
a very large brain.

So perhaps were it not for a chance
collision with an asteroid,

creatures like this could be
ruling the world today

just as they did all those
millions of years ago.

Let's imagine that the dinosaurs
really did become some sort

of dinosauroid, the great rock
doesn't fall out of the sky,

there's a bright light in the sky,
the dinosaur says, "What's that?

"No idea". The mass extinction
is postponed. In fact, cancelled.

So what's happening then?

We've got the Apes rapidly evolving
and they're beginning to

look over their shoulders because
just conceivably there are also

these dinosauroids doing
rather similar things.

What would have happened?

Would it have been an evolutionary
race? Maybe there would
have been a winner?

Or maybe, unbelievably, madly, there
could have been a co-operation.

The Utopian notion
of dinosaurs and humans
sharing the planet may appeal,

even be plausible to some,

but most palaeontologists
see the dinosauroid as an insult
to dinosaurs.

There's probably some
good ideas there.

The brain was getting bigger,
and they probably

would have continued to
outcompete other animals.

But for them to become
fully erect like humans
is a little bit fanciful.

Dinosaurs would have continued
to develop, to specialise.

They would have adapted,
but they would have adapted

and specialised as dinosaurs, they
wouldn't have become primate-like.

The idea that a dinosauroid could
exist as a scientific question...

is bogus.
It's about as bogus as it gets.

It is fairly arrogant to think
the endpoint of evolution

should emulate human beings.

If the asteroid had never hit,

life on Earth could have been
very different.

But that's all just
crazy speculation.

Everyone now knows that dinosaurs
were wiped out 65 million years ago

and none of them survived that
catastrophic asteroid impact.

Or did they?

The idea that dinosaurs may
have evolved into something else

was one that had been doing
the rounds for many years.

But it began to gather momentum
when some palaeontologists

began to increasingly suspect
that dinosaurs might still be alive.

The Natural History Museum, London.
Within these hallowed halls

lies the fossil that first
hinted at the origin of birds.

Discovered in Germany 100 ago,

superstitious quarry workers
thought it was a fallen angel.

Archaeopteryx turned out to be
something almost as remarkable.

The size of a pigeon, it possessed
teeth, a long, bony tail,

and claws on its arms.
All features of reptiles.

At the same time,
it was very much like a bird.

It actually has impressions of
the wing feathers, both wings

and long tail feathers,
but the tail has a long set of bones

running down it as well, which
modern birds don't have at all.

So Archaeopteryx really does
seem to be a primitive bird.

These fossils, I find it exciting
to look at them

because they have so much
scientific information in them,

but they're very beautiful objects
to look at in their own right.

They really are an exceptional
snapshot record of evolution.

That fossil was to be the key
to something that John Ostrom

had been thinking about for decades.

When he'd first described
Deinonychus in the 1960s,

he'd noticed that its skeleton was
strangely similar to that of a bird.

Archaeopteryx helped him
refine his ideas.

Neat animal, isn't it?

I think so.

And what made me even more excited

was when I saw structures
in that animal

that I subsequently recognised

in Archaeopteryx.

This is the Solnhofen Archaeopteryx.
The Solnhofen specimen, yeah.

John Ostrom's crucial
realisation was that

his beloved Deinonychus
shared many anatomical features
with Archaeopteryx.

He compared in detail the skeletons
of predatory dinosaurs,

Archaeopteryx and modern birds.

He found a whole
set of similarities -
most notably in the skull,

the hind limbs and the forearms.

For a start, they all have
the same number of fingers.

This is the skeleton
of a modern pigeon.

Three fingers in the hand
of a modern bird,

three fingers preserved in the hand
of Deinonychus, and that particular

kind of hand morphology
is also supplemented by

the strange wrist bone that
allows for the flexibility

that produces the flapping strokes.

The similarities between birds

and predaceous dinosaurs
is amazing to me.

But, as with all
groundbreaking new theories,

Ostrom's idea had its detractors.

The dinosaur-bird theory has
tremendous popular appeal,

one can vicariously study dinosaurs
at the back yard bird feeder,

and one can buy a piece
of dinosaur leg at the local
Kentucky Fried Chicken.

So it has tremendous appeal
to the public.

Unfortunately, it seems to be wrong.

Alan Feduccia argued that
birds evolved long before
dinosaurs came along.

They descended from much more
primitive reptiles,

and any similarity between birds and
predatory dinosaurs was superficial.

They resembled each other because
they both walked on their hind legs,

not because
they were closely related.

Such vocal sceptics were going
to need better proof

if they were to be convinced
of the dinosaur-to-bird theory.

And in 1999 in Tucson, Arizona,
fossil collectors thought

they might have come across
a specimen that fitted the bill.

I carried it out to the light

of the sunlight so
that I could see it cross lit.

And there were a number of
beautiful teeth in this skull.

And that was very exciting.

And then we studied also the tail
that was a dinosaur...

a very dinosaur-like tail.

I got this incredible high feeling,

the feeling of discovery -
that wonderful time

when everything clicks
into position.

The two fossil dealers thought
they could be looking at

one of the most
important fossils ever found.

A specimen that would prove
beyond doubt

one of the most controversial
theories in all of evolution.

This fossil,
this clearly cross between a bird

and a dinosaur was what everybody
had been looking for.

And here it was, right there,
right in front of my eyes,

and I was one of the first
people to see it.

I looked it over very carefully.

Literally under a magnifying glass.

And I was looking for any tell-tale
features, particularly on the tail.

I wanted to look at that tail
very carefully

because it was very clearly
a dinosaur tail.

The world of palaeontology
was gripped

and a team of experts was
assembled to investigate.

After several months, they confirmed
that it was the missing link.

It had a bird-like front and legs,
and a dinosaur-like tail.

They called it Archaeoraptor,

ancient hunter,

and proudly presented it
to the world.

Scientists could now say that
dinosaurs evolved into birds.

One of the most important theories
in evolution was finally proved.

But not everyone was convinced.

At the university of Texas,
Tim Rowe had used a CAT scan

to study the fossil.

The results threw up
some serious questions about
how it fitted together.

I'm going to show you two slices.

The first is this slice here
through the skull

and these other elements here,

and the second slice will be back
through the ankle and tail,

this critical region here
through one of the legs.

When we go to these slices,
here's what we see.

Here's the skull.

We can see the skull is part
of this upper layer of shale.

And you can see
the fracture pattern here,

here's very tight fractures
that fit together.

Here, a pair of fractures,
one occurring against the next.

A straight fracture.

The pieces on either side are
the same thickness. Same density.

But when we get to the edge
of the block,

this piece is a little bit thicker

and denser than the piece
it's glued against.

As we move to the tail,
to the critical area,

we can see that it's completely
surrounded by grout,

and that there are no natural
ties between the tail piece

and this piece to the right or left.

In fact, it's just swimming
in this ocean of grout here.

And as we map through the entire
specimen, we found no verifiable fits

between the tail and any of the other
parts anywhere else in the specimen.

The scan clearly showed
what the naked eye couldn't see.

There was no natural skeletal link
between the all-important tail

and the rest of the fossil.

It had simply been glued on
with grout.

The vital evidence that seemed to
prove the link between birds

and dinosaurs was a fake.

The dinosaur fake was
a dreadful blow for supporters
of the bird theory.

But scientists who were committed
to the idea refused to give up.

They were determined to keep
looking for proof.

Although the fossil had been a fake,

its front half was
a new kind of primitive bird.

Fossil hunters flocked to the region
where it had been found.

And they struck gold.

Extraordinary, well preserved
fossils revealed dinosaurs

and birds not only shared
features like downy feathers,

but also hollow bones and
similar pelvises and hind limbs.

On a remote farm in Colorado,

palaeontologist Brent Breithaupt
presented even more proof

of the close relationship between
the ancient fossils and birds.

Very good. That should make
an excellent track.

Here we have two tracks
that we recently made.

This one here is from the Red Gulch
Dinosaur Tracksite.

This one here preserves
the three-toe impressions,

tridactyl impressions,
of the foot of the dinosaurs.

The small to medium sized theropod
dinosaurs that lived up there.

Now, over here, we have one
that we just got from this site.

Again, a nice tridactyl footprint.

Again, very well preserved.

If we compare both casts,

we can see these particular tracks
look very, very much the same.

But these footprints are
not of a theropod that died
65 million years ago...

These are only a few hours old.

There's dinosaurs
in them there hills.

In fact, dinosaurs are everywhere.

For the first time
on network television,

palaeontologist Julia Clarke
is about to perform
an autopsy on a dinosaur.

Only you are more likely
to know it...

as a roast turkey.

Because you see,
birds ARE dinosaurs.

So today we're going to dissect
the evidence that birds

are living dinosaurs
from this turkey.

What we're pulling off here
is the major flight muscle,

supracoracoideus that is in
velociraptor and oviraptor.

One of the features you see is that
the second finger is the longest.

This is a feature we see going back
as far as early dinosaurs,

even Triassic forms.

We're all familiar with wishbones,
from any kind of turkey meal.

Wishbones actually are one of the
most intuitive pieces of evidence

that birds are living dinosaurs,
because we have wishbones now

from a variety of theropod dinosaurs,
including relatives of tyrannosaurus

and velociraptor, and even earlier
dinosaurs such as coelophysis.

Yes, just as we share 98%
of our DNA with chimps,

turkeys - in fact all modern birds -

are direct descendants
of theropod dinosaurs.

And the freshly-made dinosaur
tracks in the hills of Colorado?

Emus.

Inwardly, outwardly,
even in the way they move,

the similarities between
theropod dinosaurs and birds
are numerous.

But, being warm-blooded,
their ultimate success

was in an evolutionary solution
to the need to keep warm.

Large dinosaurs really don't have
a problem with body heat.

If they have a problem, it's
getting rid of excess body heat.

But small dinosaurs
have this problem.

They're losing their heat
all the time.

So it would be a good thing
if a small dinosaur was

warm-blooded, for it to have some
kind of insulation on its body.

It started with the development
of thin, downy filaments.

In time, those filaments
strengthened and thickened.

As non-flying birds,
emus are one of the best examples

of feathers as they were originally
designed. As an insulating layer.

Once you have those long feathers,
then of course it does give you

an aerodynamic advantage as well.

And if you have that advantage,
then selection starts working
on that advantage.

And it may well be that that
was forcing these feathers
to become longer

and longer until finally that animal
not only jumped across the ditch,

it actually flapped its arms
and flew across the ditch.

And so it seems that flight,
far from being

the reason for the evolution
of feathers, may have been
a by-product.

But with it, some dinosaurs
were already adapting in ways

that would equip them for life
after the meteorite impact.

The fact of the matter is
that the age of the dinosaurs
never actually ended.

Dinosaurs DID survive
the cataclysmic event of
65 million years ago.

So when we talk about dinosaurs
living with us today,

and the fanciful notion
of what it would be like,
it's not so much fantasy.

They're right there.

Dinosaurs have not only survived,
there are far more species of them

on the Earth today than there are
mammals. They're not the biggest
animals any more,

but still there's over 10,000 living
species of descendents of dinosaurs.

They didn't actually go extinct
at the end of the Cretaceous period

like everybody thinks.
They're outside flying around.

You can't go into a forest
without hearing dinosaurs.

In that sense, maybe they won out,

and we just think we're on top.

Over the last half-century,

scientists have hunted all over
the world for new clues

to help them piece together
the fragments which reveal
the life of the dinosaurs.

They've come up with
ingenious new ways of working out

how the dinosaurs lived and behaved,

made extraordinary discoveries,

and battled to answer some of the
oldest, most vital questions of all.

But there are still things
we don't know,

mysteries to be solved,
and one of the exciting things

about palaeontology is that,
in an instant,

perhaps with just the tiniest
of discoveries,

everything we think we know
about dinosaurs today

could all change again.

There are always new discoveries
out there...

waiting to be found.