Lost Worlds, Vanished Lives Attenborough's Passion Projects

I've been making natural history films for over 60 years

and in the process, I've been to some very interesting places.

But every now and again, I've been allowed to make a film

about my other enthusiasms, about the history of exploration,

about tribal objects or the life of a great scientist.

You could call them my passion projects.

After about 40 years of making programmes about living creatures

that populate our world, I wondered whether I might try

to make some programmes about the ones that had disappeared.

They were the creatures that first interested me

in the natural world - fossils.

But how can you make programmes about animals and plants

that no longer exist?

Well, I thought we'd have a go.

It's always seemed to me that fossils

are some of the most romantic things on this planet.

I mean, if you came across a pebble, like this, for example, and you

just happened to knock it with your geological hammer,

which happened to be around at the time...

But if you just hit it with a hammer

and split it and it opened like that,

wouldn't you think that was remarkable?

And that hasn't seen the light of day for 400 million years.

And you're the first person ever to clap eyes on it.

Isn't that the most romantic thing ever? I certainly find it so.

Where I lived in Leicester, when I was a boy,

we didn't find trilobites like that, but you did find things like this.

This actually comes from Kimmeridge,

but they're ammonites.

And I collected them like mad, I would be off on my bicycle

and sitting around in disused iron quarries, just knocking rocks.

And they come in all different kinds and sizes and actually,

this particular piece as well is

interesting, because if you turned

it over, you'll see the outside

of the shell of a simply enormous one!

That these others somehow or other have got stuck inside it.

So fossils, for me, have always been thrilling.

And I don't make these programmes out of some kind of proselytising

view that people ought to be interested,

I do it because I'M interested in them and it gives me a huge pleasure

and I think other people can get pleasure from it, too.

RUMBLE OF THUNDER

Animals and plants flourished on this earth

for millions of years before human beings appeared on it.

And the direct evidence of that comes from one source only -

from their remains that can be found in rocks.

From fossils.

Some are spectacular and dramatic, complete skeletons of huge reptiles.

Others are the merest trace of imprints,

left by such insubstantial creatures as jellyfish.

Many are the remains of creatures quite unlike any that exist today,

and fossils can be found all around us if we know where to look.

The South of England, the Dorset coast,

and a world-famous fossil site.

Heavy rains have drenched the clay-and-limestone cliffs,

the rocks are slipping, new surfaces are being exposed,

fresh fossils could have been revealed overnight.

Peter Langham regularly patrols this coast, searching for them,

and he knows that the day after a storm is the very best time

for finding something interesting.

This looks like a couple of likely looking bits of stone.

Why? They look like all the rest to me!

THEY LAUGH

Really, if we see this from the right horizon...

'It takes a lot of experience to be able to judge which out of the many

'boulders in a cliff like this is likely to have a fossil inside it,

'but then, Peter has been doing this for years.'

Let's see what happens.

-There we go.

-Oh, gosh!

That is one of the most well-known ammonites.

That's beautiful.

Fossils don't always appear every time you hit a nodule of rock

with a hammer.

But they do so surprisingly frequently

if you can recognise the right sort of nodule

and know where to find it.

I used to come to these old ironstone quarries

in Leicestershire as a boy to look for them.

The moments of success when the rock fell apart

and revealed a shell that hadn't seen the sun for 200 million years

and that I was the first human being to see, seemed to me then,

as, to be truthful, it still seems to me now, to be moments of magic.

It's a beguiling business.

For you know that even if you've not found anything much so far,

the very next blow of your hammer

may suddenly reveal something amazing.

That's not bad but if I keep looking,

I should be able to do rather better than that.

Slowly you begin to get your eye in and soon you will start

to recognise the particular glint,

the telltale curve, the slight change in colour

that indicates the tip of a fossil sticking out from the rock.

It doesn't take long to gather quite a varied collection.

They all seem to be the remains of animals that lived in the sea,

but the local people, some of them at any rate, refuse to believe that.

"How could they be?" they would say,

when here we are in the middle of England

about as far away from the sea as you could get

and when these fossils are buried in the rock,

far below the surface of the earth, how could that be?

Instead they have their own explanations.

They said, for example, that...

these,

these, they said, were the toenails of the devil.

And this, these impressive

bullet-shaped objects

and there are some actually in this boulder on which I'm sitting...

Those, they said, were thunderbolts.

They were made when lightning struck the earth.

And the most beautiful of them all,

these ammonites.

Well those, they said, were snake stones and they came in two kinds.

Big ones like that, and little ones.

Farther north up in Yorkshire near Whitby, where exactly the same

fossils are found, the people had a detailed explanation

as how that had come about.

They said that back in the seventh century,

an early Christian saint, St Hilda,

had wanted to found an abbey,

but discovered that the place was infested by snakes.

So, miraculously, she turned them all to stone.

Of course, there's one problem with that explanation.

None of these so-called snake stones have heads.

But when the devout pilgrims came to the site of this miracle,

local craftsmen solved that problem.

They carved on heads onto the snake stones so that they would look

rather more convincing.

But there are some fossils that are so perfectly preserved

that their animal origin simply cannot be denied.

These tiny creatures are imprisoned in amber - a hard,

stony substance that is found in lumps in mudstones and sandstones.

Who can doubt that these, so complete in every bristle

and antenna, are truly ants, scorpions and flies?

But how did they get there?

Amber was once liquid and sticky.

Resin trickling down the trunks of trees that grew in swamps

some 30 million years ago.

Insects were attracted then as now by its sweet smell

and flew or crawled towards it,

with fatal results.

The resin gradually hardens into solid lumps.

Eventually, the tree itself died.

And the long, slow processes that lead to fossilisation began.

Mud and sand washed in by the sea

slowly settled on the resin lumps and buried them.

As millions of years passed,

the layers of sediment were compressed and compacted

under their own weight and turned into mudstones and sandstones.

And then were pushed and buckled by colliding continents

to form mountains like these in the Dominican Republic

on the Caribbean island of Hispaniola.

Since amber is highly valued for making jewellery,

men today burrow deep into the hillsides to look for it.

The shafts are steep and may go as much as 100 yards into the mountain.

The amber miners have to chisel away tonnes of stone

before they find the particular layer where the lumps

of resin have accumulated.

But once they find that seam, they often discover piece after piece.

-Es que el ambar?

-Si.

Grande, eh?

It's difficult to tell what's inside pieces like this

when they've just been dug out

because the surface is all broken and pitted and dirty

but when they are polished,

they may reveal the most extraordinary things.

Many pieces are quite clear with nothing whatever in them

and those are the ones that are valued for jewellery.

But one in every dozen or so has the remains of some kind of creature.

Backboned animals were mostly strong and large enough

to pull themselves free from the resin if they touched it,

but occasionally, they failed,

and these are the rarest of all amber fossils.

A tiny lizard.

And a frog.

Insects are the commonest and were sometimes caught in action.

An ant carrying a pupa.

A bug beside a leaf from which it might have been sucking sap.

A beetle apparently walking up a twig.

Flying insects with even their delicate wings undamaged.

And a whole swarm of ants, so perfectly preserved

that you can even see the facets in their 30-million-year-old eyes.

I suppose the most romantic is the ones that are very, very, very old.

I mean, 550 million years old.

The Burgess Shales up in the Canadian Rockies.

The Burgess Shales come from a period when life was suddenly

burgeoning out into a multitude of different forms.

It's so old that animals with bones had hardly developed.

But in the Burgess Shales, the deposit is so fine-grained

and was developed and put down in such a way that it trapped

a lot of these soft-bodied creatures -

jellyfish, slug-like creatures -

that they left only the faintest impression

in this very, very fine-grained rock.

When it was discovered, it was a revelation,

that suddenly you saw there were forms of life

that people had never dreamed of,

right at the beginning of the historical record.

The sun-lit waters of a shallow sea.

Life here is rich and varied.

Jellyfish, sea gooseberries and all kinds of larvae

drift in the dappled waters.

Creatures like these have a very ancient ancestry.

They were among the first forms of life to appear on earth

and they existed for several hundred million years

before the development of fish - the first animals with backbones.

But when such creatures with no bones in them die,

what remains of them?

Almost nothing.

Their soft tissues simply disintegrate

and dissolve in the water

and there's hardly anything left of them but a little slime in the mud.

Only a minority, a few molluscs with hard shells,

leave any signs of their existence after their flesh has vanished.

This, too, was once mud at the bottom of a sea

but that was over 500 million years ago

and now it's mudstone and high in the Canadian Rockies.

And these rocks too contain the remains of the hard parts

of sea animals, and very extraordinary animals too.

They are now totally extinct and we call them trilobites.

But there's virtually nothing else

but trilobites in these rocks.

So, what did the trilobites live on and what hunted the trilobites?

The answers to questions like those could only be guesswork.

Until, that is, the year 1901.

In that year, an American geologist, Charles Walcott,

was exploring here in the Rocky Mountains of British Columbia.

He was in his 60th year and coming towards the end of a long

and distinguished career in which he had made a special study

of the very ancient fossil-bearing rocks of North America.

When he got to this precise point on the trail, where this

slip of loose rocks crosses it, one of his horses stumbled.

Walcott dismounted to clear the path and when he did so, he hit one

of the boulders with his hammer as he must've done 10,000 times before.

Only this time when the boulder fell apart, it revealed

a fossil, the like of which he had never seen before

in all his experience.

To his amazement, he saw that it had its soft parts preserved.

Tentacles, the head and a row of small legs

on either side of his body.

If he didn't do so then, he must have realised very soon afterwards

that this was the most important discovery of his life.

So the next season, he and his sons returned to this place to try

and find out where that boulder had come from.

They climbed up the rock tip, looking for fossils as they went,

and knowing that the highest level in which they found any fragments

with fossils in them must be the place

from which all the fossils were coming.

And that proved to be just here.

And this place has been the site of research ever since.

A band of these shales just seven foot thick produced all the fossils.

Walcott came here for the next eight seasons and in that time,

he collected 61,000 specimens.

Two thirds of the species that he found proved to be new to science.

Animals such as these with delicate legs, with tiny gills

and threadlike antennae, must've been living throughout the seas

of this very ancient period.

They had never been seen before because everywhere else,

being soft-bodied, they had simply dissolved

and disappeared without trace.

Only here, for some extraordinary reason, had they been preserved.

And preserved, what's more, in amazing detail.

These rocks are known as the Burgess Shales.

How is it that one thin band of them

on this particular mountainside preserved signs of life

that are found nowhere else in the world?

That was one of the questions that Walcott

and his successors spent a long time trying to answer.

The latest group of scientists to work on the site here

come from the Royal Ontario Museum and are led by Des Collins.

530 million years ago, this was a muddy sea floor about 400 feet deep.

It was directly in front of a massive, sheer cliff that you can

see in this light-coloured material over here.

The reef front rose in a sheer cliff, about 300 feet high

and you can see at the top, the bedded rock, which is where the

animals lived in a lagoon about 100 feet deep or less.

Every so often, the mud on the top would come down the slump,

picking up the animals, bringing them down here, killing them,

burying them and preserving them in the mud.

This happened at a time when complex animals had only just appeared,

so the ultimate ancestors of all life today

must therefore be among them.

This worm with an internal rod running along its length

may be the ancestor of all backboned animals.

And this, with five pairs of claws on its head,

may be the creature from which scorpions and spiders have

evolved, for it shares some of their most significant characters.

By examining the best of these specimens,

it's possible to deduce from the flattened outlines what it was like

before it was squashed flat, and to reconstruct it in three dimensions.

But some specimens are so strange, it's difficult

to make head or tail of them.

This, for example, three or four inches long, looks like some

kind of shrimp, except that none has ever been found with a head.

And this, rather like a slice of pineapple,

could this be some kind of jellyfish?

Though there are still some speculations,

we now have a picture of a large and varied community,

but if there were so many of these mud-munchers and filter-feeders,

there must surely have been some hunter that preyed on them.

What was that?

That question troubled a British palaeontologist,

Harry Whittington, as he worked on some of Walcott's specimens.

Searching through many thousands of them, he found one in which

that pineapple slice seemed to be attached to some other structure.

What is more, there were several other specimens rather like it,

including one that was not completely cleared of matrix.

And he started very carefully to investigate it.

If you think this is the underside of the body, which I did,

to look and see, well, is there anything perhaps

attached to the underside that goes down into the rock?

And there was a little area here,

and gradually this thing came exposed.

And I realised that was this thing that had been described many

years before, Anomalocaris. The "strange shrimp".

But no whole one had ever been found.

Now here was one attached under the front end of this animal.

Was that an accident, having that there?

If there was one one side, there ought to be one the other.

And indeed there was a layer in the rock here,

and I exposed parts of that

chiselling around here, and

there exposed is part of the companion one

that was attached there.

That predator was revealed.

The headless shrimps were its claws,

and the pineapple slice was its muscular mouth.

This was the terror of the trilobites.

So now we have an even more complete picture of the life that

flourished on the sea floor

530 million years ago.

We knew that it must have contained the ancestors of all

subsequent life, but now we have some idea of what they looked like.

In contrast to the Burgess Shales, which were extremely old,

one of the most recent deposits of extinct animals

is in California, outside Los Angeles, where

there are tar pits, naturally occurring tar pits.

And these pools, which still form today,

look like black, shiny water.

And any animal that came there to drink would find that

suddenly it's trodden into this sticky stuff, which actually

holds them tight and eventually pulls them down and they die.

And then other animals come along, see a dead wolf or something

and think there's a meal, and comes in to take the trapped animal

and then gets stuck itself.

And amongst the most dramatic of these, of the predators that

come there, are the sabre-toothed tigers. But who would think you'd

get that sort of insight into animals that lived 40,000 years ago?

Well, the La Brea tar pits enable you to do that.

Los Angeles, in America.

Hardly world-famous for its fossils,

but it should be, for right

in the very heart of this most modern of cities is a site

that gives another, wholly exceptional picture

of a vanished world.

BIRDS SQUAWK

40,000 years ago, this was the appearance of the land

on which hotels and freeways now stand.

And firm evidence for every single detail in this most detailed

painting comes from a small park close by one of the city's

main avenues - La Brea.

In one corner of it, through the harmless grass,

oozes a substance that kills - la brea.

Tar.

It wells up from the ground here to form these black pools.

When it rains, water lies on top of it

and it looks like a place where you might get a drink.

But any animal that came down here to do so

would be lucky to escape alive.

Feet sink into the tar, feathers get entangled in it

and the animal is fatally trapped.

That's been happening for 40,000 years and more.

And it's still happening today.

Tar, like oil, is derived from the bodies of animals

and plants that accumulated in swamps.

The sand that was deposited on top of them squeezed their

remains so that droplets of oil were expelled from their tissues.

That accumulated in basins within the texture of the porous sandstone,

and then where there is a fault,

this substance is forced up to the surface.

The earlier flows of tar, containing the most ancient animals, have

now been covered by later flows,

so to reach them, you have to dig down into the tar pit.

And excavations which started back at the beginning of the century

are now being carried on some 30 feet down.

The work is supervised by trained scientists,

but most of the team is made up of local volunteers.

-OK, this is ready to go. You got the bag?

-Yes, I do.

-OK.

-That's a sabre-toothed cat femur.

-Right or left?

That's a right.

-I'll bag up this ulna uncovered here.

-What's it lying on top of?

Well, it's laying right across a sabre-toothed cat skull.

The finds have been put on display in a museum that has recently

been built on the site, and very spectacular they are.

In addition to this magnificent imperial mammoth, the biggest

of all the prehistoric elephants that lived in North America,

there were extinct horses and camels which grazed on these plains.

These dire wolves were about the same size as living wolves,

but with more massive heads.

Struggling trapped animals were obviously something

they couldn't resist. For wolves, in fact,

are the commonest of all the victims of the tar pits.

The most frequently trapped grass eaters were the bison,

so there were probably big herds of them.

But again, the pits contain more bones of the animal

that preyed on them, the American lion.

ROARING

The females were about the same size as African lions,

but the males were 25% bigger.

And there was an even more impressive cat, the sabre-tooth.

At one time it was thought that these extraordinary teeth

were daggers for stabbing.

But now it's believed that they were used to slit open

the belly of the prey.

You might wonder how on earth the animal managed even to

close its jaws, and I asked a scientist at the museum,

George Jefferson, to explain.

As you can see,

the incisors actually interlace between each other.

Allowing the jaw to fully close.

I'm surprised to see how much space there is between those huge

sabre teeth and the lower jaw.

That gap is the same gap

as between the meat-slicing teeth

here on the side of the face.

What that meant is the animal would disengage the incisors,

drop the jaw down, move it slightly sideways and guide the slicing

blades here by running the inside of this flange

against the canine tooth.

-Is that a new discovery?

-It is.

In fact, we didn't know that this gap was that way

until we found this particular specimen.

ROARING

The sheer abundance of the dire wolf skulls also yields information.

They're not, of course, all the same,

and the differences are not all due to age.

The lumps and distortions here that are apparent, compared to the

smooth forehead on this animal, indicate there was

an infection in the frontal sinuses of the forehead.

-Probably the result of being kicked in the face.

-OK.

May have been kicked by a bison, may have been kicked by a camel.

This animal was obviously going after its prey and getting injured.

We also see injuries in the sabre cats.

In this hip, we have a fairly normal hip socket here, but on this side,

you can see a lot of knobbly bone,

a distortion and break.

We think it may have been butted by a bison,

hit very hard or even possibly by a mammoth elephant.

-So, he's really a cripple.

-He really is, yes.

It's astounding it lived as long as it did.

Some researchers believe that this is evidence that the injured

and infirmed were being tolerated within the population

-and possibly cared for.

-So, social behaviour amongst the sabre cats?

Social behaviour.

Well, there's no doubt that if you say "fossil, animal",

an awful lot of people immediately say dinosaur.

And to make a programme, or make a whole series, about fossils

and not to mention dinosaurs, well, you couldn't really do that.

On the other hand, the sort of animations that we had

in those days to bring dinosaurs to life were really rather clunky.

They didn't really bring the reality, and I thought it would

be a bit of a challenge, rather fun,

to actually do a programme about dinosaurs in which you didn't

have a single reconstruction, and that you tried to bring the animals

to life in people's imaginations by simply looking at the bones.

We are looking for a dinosaur.

At a time when the dinosaur first appeared, about 200 million

years ago, all the land and the earth was grouped together in one

supercontinent, and the dinosaurs roamed all over it.

And so today their remains can be found in the fragments

of that supercontinent -

in Australia, in North America, in Europe, and here in Africa.

We're on an expedition in the southern fringes of the Sahara,

and the reason we've come here to look for them is that in a desert,

there's very little vegetation to cover the rocks, so that

if there are dinosaurs in them, we'll be able to see them.

One of the expedition leaders, Dick Moody, showed me their first find.

I'm sure you'll find this one, which we haven't touched,

quite a superb specimen, quite exciting.

Oh, it is absolutely magnificent!

This is obviously the backbone. Which way does it lie?

It's running in that direction, we believe, towards the head

-and towards the east.

-Yes.

And in this direction, generally back towards the tail, obviously.

-And the ribs, which side?

-The ribs are running off, as you can see,

they're slightly disarticulated and slightly broken up.

And how long do you think the complete animal was?

-Well, between 20 and 30 metres.

-What, that's 90 feet?

-Yes.

-God, that's enormous.

-It's a large animal, yes.

And how complete do you think it might be?

We're hoping to find some skull material

-and obviously limb material underneath.

-Yeah.

Let me clear these just a little.

'The weathered shales in which the bones were embedded were

'so soft that we could brush them away with our hands.

'After only half an hour,

'we already had some idea of how much of the animal was preserved.

'But it was a further day

'before all the bones at this site were exposed.

'There weren't as many as we had first hoped.

'The base of the tail and the lower part of the spine was there,

'but the legs and most of the body were missing.

'But only half a mile away,

'the rest of the expedition was working on another group of bones.

'These were leg bones, and probably belonged,

'if not to the same animal, then at least to the same kind.'

The huge carcass, whatever it was,

had clearly already been dismembered before it was buried.

Perhaps other scavenging dinosaurs had pulled it apart.

Perhaps the rotting body had disintegrated as it lay in the river

that eventually buried it in mud.

The expedition was from the Natural History Museum and

Kingston Polytechnic in London,

and before the bones could be transported back,

they had to be protected by wrapping

them with strips of sackcloth soaked in plaster.

This will harden into a solid jacket that will hold the whole

specimen together.

The expedition dug up and plastered almost 100 bones in the four

weeks that they worked in the Sahara.

But this was only the start of their work.

Indeed, it won't be until the team gets the bones back to the museum

in London and has cleaned them,

studied them and pieced them together

that they will know for sure exactly what kind of dinosaur they've got.

But one thing is certain.

It's a giant.

These bones too, in the museum in East Berlin,

came from Africa back in 1912.

And when they were pieced together, they proved to belong to the

most massive land animal known up to that time.

It was 74 feet - 22½ metres long.

It stood 39 feet - that's 12 metres high.

And it was estimated to weigh 77 tonnes, which is

as much as 12 bull elephants put together.

This is brachiosaurus.

Its head, perched on top of its immensely long neck,

was comparatively tiny -

Less than three feet long.

But it has huge nostrils high on its forehead, and they led some

people to suggest that this animal lived in lakes, with its head

and nostrils above the surface, while it

walked along the bottom with the water supporting its huge body.

But that, we now know, would have been impossible.

If its nostrils were open at the surface,

the water pressure 30 or so feet

below the surface would have

been so great that its lungs would have collapsed.

Furthermore, the shape of its legs and its deep,

narrow chest all suggest an animal that lived on land.

So now it seems we have to think of brachiosaurus

as a kind of gigantic reptilian giraffe,

browsing the tops of the trees.

In New Mexico, they found remains of an animal that may be even bigger.

They've already given it a name, seismosaurus, the earth shaker.

But the rock in which it is embedded, in contrast to the

soft shales of the Sahara,

is almost as hard as concrete,

and excavating it is a laborious and time-consuming business.

The excavation leader, Dave Gillette, told me the story.

This is where we found the first set of vertebrae that were

discovered in 1979, and we finally excavated in 1985.

-How much of it was showing when you first saw it?

-Only the upper part.

It was showing as though it had been

-carved out of the rock in bas relief.

-Wow.

It was perfectly exposed, just in this fashion.

And then?

And then, when we looked closer in the ground, we found a total

of eight vertebrae along this line, all in perfect articulation.

And they're from the basal part of the tail,

leading into the pelvic region. There's another vertebrae here.

And then we took out two large blocks.

One here, and another one from here at the base of the tail that

led right up to the hip region in the skeleton.

-What's that?

-This is a rib,

which has been somewhat displaced from the proper anatomical

position when the animal died.

So, what? Does the animal go on in there, do you think?

We think the animal continues right into the hill to the north

and we expect it continues for another 60 or 70 feet.

What, under the rock?

Under the rock, about eight feet deep,

and we're using sophisticated and experimental remote sensing

techniques to try to see those bones before we excavate.

The site is only a few miles from Los Alamos Atomic Research Station,

and the scientists there, on their days off,

come out to use the most advanced techniques of nuclear physics

to help Dave locate his dinosaur bones deep in the rock.

This sledge carries a still-experimental

remote sensing device.

In fact, a kind of radar that can look into the ground.

And already readings from it are beginning to confirm

the gigantic size of the animal.

I asked Dave how long he thought

seismosaurus might eventually prove to be.

My best estimate just now is 140 feet in length from the tip

of the snout to the tip of the tail.

And how does that compare with others?

Well, the previous record holder was diplodocus at 87 feet.

So we're approaching twice the length of diplodocus.

And when will you actually know whether this is a world beater?

Well, we know now. We have good confidence in our calculations.

Dinosaurs certainly include some gigantic animals.

Stegosaurus, bigger than a rhinoceros.

Ammosaurus, tall as a giraffe.

But they weren't all huge. Some were no bigger than a dog.

Nonetheless, many were very big indeed.

And they certainly include some of the most spectacular animals

ever to walk the Earth.

They dominated the world for over 160 million years.

What did the dinosaurs eat?

Well, flowering plants didn't develop

until about 100 million years ago.

So that means that for most of the time that the dinosaurs

were on Earth,

there were very few of the kinds of plant that dominate the land today.

There was no oak trees or hazel in Europe, upon which deer feed.

In Africa, there was no thorn scrub or acacia, on which elephant

and giraffe browse.

Most important of all, there was

no grass, on which horses or bison or antelope graze.

Instead, there were plants like these.

These are Cycads.

Today, they grow wild in only a very few places,

and mostly in the tropics.

But when the dinosaurs first evolved, they were spread worldwide.

In addition to these, there were also tree ferns

and primitive conifers, rather like pines.

But all these plants had tough, fibrous leaves,

almost indigestible, you might think.

And if you have to keep your food in your stomach for a long time,

then you need a very big stomach to serve as a storage vat.

That in turn means that you have to have a very large body to carry it.

So the ancient pastures of tree ferns may be one of the main

reasons why plant-eating dinosaurs grew so big.

As millions of years passed, however, evolution brought changes.

The first flowering plants appeared.

And so did new kinds of plant-eating dinosaurs.

These are hadrosaurs. They had

no teeth at all in the front of their jaws.

Instead, the rounded bone was almost certainly covered with

a horny sheath.

With this, they could have done little more than just

nip off leaves and twigs.

But inside the mouth, at the back of the jaws,

they had an enormous battery of teeth, row upon row.

As these crushed and ground the tough fibres,

they were inevitably worn down, but could they use them to chew?

Mammals like this camel can chew by moving their lower jaw from side

to side, so they are able to break down the toughest of plant foods.

The dinosaurs were reptiles, and no reptile can do that.

They can only move their jaws up and down,

and that puts a real limit on what they can eat.

The hadrosaurs dealt with that problem in a most remarkable way.

The highlighted upper jaw could actually hinge outwards.

This means that as the lower jaw moves up,

it pushes aside the upper jaw.

In effect, chewing without any sideways movement of the lower

jaw at all.

The most powerful grinding battery of all was that

possessed by triceratops, one of the last of the dinosaurs.

This, the product of 100 million years of development

in the technique of chewing, is perhaps the most powerful

chewing device ever possessed by any animal.

A huge beak in the front served as shears, which could probably

slice clean through a tree trunk.

The branches were then moved to the back of the mouth, where the

massive grinders reduced them to pulp.

But these teeth belong to a very different sort of animal.

This is Tyrannosaurus rex,

the biggest of all the meat-eating dinosaurs,

measuring over 40 feet long and weighing about seven tonnes.

Surely the most terrifying hunter ever to roam the earth.

So the bones of dinosaurs, carefully pieced together,

can tell us a great deal about how big these animals were,

what they fed on,

and therefore their relationships with one another,

and how their limbs articulated.

But how fast could they move?

To answer that question, you have to come to a place like this.

150 million years ago,

there was a mud flat here around the margin of a freshwater lake.

The lake filled, and eventually sediments covered the whole area,

and the mud flats turned into mudstones.

In them are preserved huge footprints.

Dinosaur footprints.

These, nearly a yard across,

can only have been made by a huge plant eater,

like a brontosaur such as Diplodocus.

These prints, though, are very different.

Not circular, but with three prominent toes.

At the end of each, there is a deep, sharp mark

that can only have been made by a claw.

They match the three-toed feet of theropods -

medium-sized carnivorous dinosaurs.

From tracks like these, it's been calculated

that some of these hunters could run at up to 30mph.

Moving at such speeds demands a great deal of energy,

and an animal can only produce enough if it has a warm body.

So did the dinosaurs get their energy directly from the sun,

as reptiles do today,

or could they generate warmth internally like birds and mammals?

That is a question of great debate.

This is how Tyrannosaurus rex may have moved,

in the opinion of one of the new generation of dinosaur interpreters,

Robert Bakker of the Museum of Colorado.

OK, Tyrannosaurus rex, the most famous dinosaur,

the most popular dinosaur.

And here it is, running at 40mph -

faster than a rhino,

faster than an elephant.

This T Rex is going faster than a lion.

Yes, but that's your animation,

how do you know it can go as fast as that? HE LAUGHS

Because of the way the muscles were hung on those leg bones,

because of the way the calf muscles were hung on that knee,

because of the way the massive thigh muscles were hung on that ileum.

But why does that prove it was warm blooded?

Let's look at the real one, eh?

Could it really have reared up like that and lifted its immense legs?

Absolutely, and more. It could jump, it could run, it could run fast.

This is a T Rex, a real one, a cast.

With a bloody big knee, right?

But why does that mean it's got to be warm blooded?

Actually, it's the other way around,

because warm bloodedness demands speed.

This animal has to cruise fast,

and it has to go into great bursts of speed,

and it has to kill more often than a cold-blooded animal.

There is no cold-blooded animal today with this great strength.

None.

This is not a scaled-up lizard, this is not a scaled-up tortoise -

this is an enlarged, five-tonne, meat-eating roadrunner.

That's what it is!

And like a roadrunner, it's eating frequently.

And there's another message, too, about speed in the skeleton,

not in the legs, but in the chest.

Because in the chest...

there was housed in these ribs, without doubt,

a gigantic heart, designed to pump,

designed to put out blood flow at emphatically warm-blooded levels.

ROARING

So maybe we should get rid of the image of dinosaurs

as slow, lumbering plodders,

and think of them instead as nimble and agile

in spite of their size.

BELLOWS AND CRIES

The truth is almost certainly that some were warm blooded,

and others were not.

A skeleton can not only give clues

about the temperature of an animal's blood.

It can, perhaps even more surprisingly,

reveal something about the animal's social life.

This is the skull of a hadrosaur.

Like all hadrosaurs, it has a rounded front to its jaws,

lacking in teeth, which in life were probably covered with a horn,

and which give the family as a whole the name "duck-billed dinosaurs."

At the back, there's a battery of powerful, plant-crushing teeth.

In fact, the skulls of all hadrosaurs are very much the same,

except for one feature.

This - a crest.

And this varies amazingly.

This one is thin and forward-pointing.

This one is long and goes right down the front of the skull.

And this one is broad and plate-like,

and sits on top of the skull.

So these are three separate species.

But this is almost certainly a male,

because here's another one with very much the same shape of crest

on top of the skull, but slightly smaller, so it's probably a female.

And there is a third in which the same shape of crest

is only just developing, so that's probably half grown.

So crests in hadrosaurs serve to proclaim

an individual's sex, age and species,

and since such adornments that do that elsewhere in the animal kingdom

are very often made more obvious with colour,

we can speculate that the dinosaurs were indeed

quite spectacular-looking animals,

as the character of their scaly skin has already suggested.

But these crests were more than visual signals.

DEEP BELLOW

Inside, there are air chambers,

which must have acted as resonators when the animals bellowed.

Since the air chambers vary in size and shape as much as the crests,

each species must have had its own characteristic call.

RUMBLING BELLOWS

And they probably roared in deafening choruses,

for we know that plant-eating dinosaurs lived in herds,

as wildebeest do today.

In Montana, deposits have been discovered

where the bones of hadrosaurs are piled up in vast numbers.

Jack Horner, the researcher who discovered the remains of the herds,

has also found in Montana

even more extraordinary evidence of the social life of dinosaurs.

He's actually found their nests and eggs,

and he showed me where I, too, could pick up bits of the shell.

-Is that anything?

-That's just eggshell.

What do you mean, just! LAUGHTER

-Really?

-Well...

We're looking for a nest. What we want to see is...

-Eggshell is important.

-Is it always black?

-Yeah.

-In this formation, it's always black.

-Yeah.

In other formations, it can be other colours.

-If the piece is big enough, you can see the texture of the egg...

-Oh, there's some.

..and then with the microscope, then you can see the pores in it.

Jack has even discovered complete clutches of unhatched eggs,

which he's taken back to his laboratory.

Now, this is... This nest is actually upside down, isn't it,

-because that's the top of the jacket.

-Right.

-And so, these... These are the eggs?

-These are the eggs, yeah.

The... This is the centre egg in the nest.

And the centre egg is always...

..laid upright, and then each egg out from the centre

becomes more and more inclined.

-They were laid spirally?

-Spiral, mm-hm.

This was the first, presumably?

That was the first one, I assume.

Are they loose?

Yes, this one's loose, here. You can see the pointed end of the egg.

And...

the top of the egg has been smooshed down.

And is the shell on there? Yeah, I can see it.

Yeah, this is all shell.

-Do you think there's anything in that?

-Yes.

-I don't THINK there is, I KNOW there is.

-How do you know there is?

Er...

They've been x-rayed and CAT scanned,

and there are indications of little ones in it, yes.

How can you... HE CHUCKLES

How can you wait?

Why don't you hit it with a spoon and see if you can take it out?

I would like to do that,

my preparators tell me I'm not supposed to!

THEY LAUGH

Have you got an open egg?

Yes, we have one from another nest.

Erm...

I think this was a clutch of 19 eggs.

-19?

-19.

And all 19 have embryos.

This is one of the better ones.

What you see here is the thigh bone, the femur...

..the tibia, and then the...

..ankle joint and foot underneath, and then,

very carefully open it up...

And what can we see there?

What we're looking at here is the right leg.

There's the left leg, the tibia,

and then between the knees is the skull, sitting in there.

-Ah!

-Right in here.

So we can see the...

The tiny little teeth had erupted in the jaw.

So it could give you a nip just as soon it hatched?

-Right, mm-hmm.

-Yeah.

-Just like young alligators can today.

-Yes.

BIRDSONG

But 64 million years ago,

the hadrosaurs and all the other dinosaurs vanished.

The reign of the dinosaurs had ended.

There are many theories as to why the dinosaurs

finally became extinct.

One of the most recent is that an asteroid from outer space

collided with the Earth, creating such an immense explosion on impact

that the skies filled with dust, blotting out the sun.

In the darkness, the plants all died,

and the dinosaurs, with nothing to eat, starved to death.

Well, there are two problems with that or any other theory

which depends upon a single catastrophe as the explanation.

The first is that the dinosaurs didn't die out

over a period of a year or a decade, but over thousands of years.

And the second is that although the dinosaurs died out,

many other creatures didn't.

These alligators are reptiles, just as the dinosaurs were.

They evolved on Earth long before the dinosaurs,

yet they've survived to the present.

It seems unlikely that they would have lived through

a sudden global catastrophe in which the dinosaurs perished.

A more likely explanation, to my mind,

is that there was a gradual change in the climate of the Earth,

and some animals, such as birds, for example,

were better able to cope with this than the dinosaurs,

with their less-than-perfect control over their body temperature.

The early birds, like birds today,

were protected by their superbly efficient

insulating coats of feathers, so they survived.

Small reptiles were able to take refuge against the cold

in nooks and crannies, and reptiles that lived in water

were cushioned against extreme temperature changes.

So the Earth still retains representatives

from all these animal groups.

So, today, less than 200 years since we discovered

that these animals even existed,

we've learned so much about them

that we can almost hear the champ of these huge jaws,

visualise the glints in the eye that once revolved in this empty socket,

clothe this immense skeleton with leathery skin and muscles,

and picture, in our imaginations,

in almost as much detail as if they were alive today,

these bellowing, battling,

browsing, nesting, courting,

scavenging, fighting creatures

that disappeared from the Earth

over 50 million years before mankind appeared upon it.