Weird Wonders Fossil Wonderlands: Nature's Hidden Treasures

Most fossils are just the hard bits that nature leaves behind,

shells like these.

The other parts of the organism, the soft parts if you like,

feathers, guts and many kinds of organisms that are soft- bodied,

leave no trace behind.

Except in a few very special places.

And it is to these places that we are going to travel

in search of windows into the past.

From 8,000 feet up in the Rocky Mountains...

..to China's most eccentric museums.

-What is going on here?

-Yeah, yeah, yeah, this is a dinosaur egg.

-Ah!

To the richest seams of fossils discovered in Europe.

Each of these unique fossil sites represents a snapshot

of an ancient vanished world.

A moment of time captured in rock.

Ah!

And filled with fossil treasures.

We'll see fossils exposed by the latest techniques.

And uncover those recently made to order.

-You mean this is a fake?

-It's a fake.

Wow, look at that!

We'll also reveal some spectacular surprises.

Sometimes the scale of the show

really does match the scale of geological time.

To learn about these creatures from the past,

we'll meet their distant descendants still living.

This animal has tracked the habitat it liked.

And, in the name of science, I'll eat a few too.

These rare, exquisitely preserved fossils

are found in just a few very special places in the world.

Extraordinary sites that have revolutionised

our ability to see into the past.

-It looks as delicate as a ballet dancer, doesn't it?

-Yes.

-And yet this poor animal probably died in agony.

-Yeah.

But rather than see through a glass darkly,

we will confront the ancient past face to face.

At the beginning of the last century the origins of complex life were a mystery.

But here, 8,000 feet up in the Rocky Mountains of Canada,

a site was discovered that overturned our views

of the origins of complex life.

Canada's Burgess Shale is one of the greatest fossil sites in the world.

Now elevated in the clouds, this ancient sea bed contains

some of the most bizarre animals ever to be discovered,

trapped in rock when they were buried alive

more than 500 million years ago.

But what were a series of catastrophes for them

provided a miracle for our understanding.

Until the early 20th century

scientists knew little of complex early life.

Then, in 1909, a fossil site was unearthed

like none that had ever been found before.

Buried within it were strange soft-bodied life forms

that challenged previous assumptions about how animals evolved...

..processes of fossilisation

and the richness of early life.

The place where this discovery was made

lies in Canada's Yoho National Park.

It's a rugged part of the Northern Rockies whose highest peaks

rise nearly 12,000 feet into the clouds.

Back in the late 1800s,

the little village of Field was just starting out,

built largely by railroad workers,

making Canada's Transcontinental Railway.

Long freight trains still run through here today.

And it may have been surveyors working for the railroads

that stumbled upon the first fossilised clues,

that there was something special hidden in the mountains.

It's a misty morning in the town of Field in Kicking Horse Pass

in the Rocky Mountains of Canada.

Behind me, the mountains rise, mysterious, invincible,

unreachable, you might think.

I'm full of admiration for those 19th century geologists

who scaled these peaks in search of mineral treasure.

Now I've got to go up there myself in search of the famous Burgess Shale.

The discovery that changed our understanding of the origins

of complex life was made by Charles Doolittle Walcott.

Born into a poor family in 1850, Walcott worked himself up

from being a self-educated geologist's assistant,

to head of the Smithsonian Institution in Washington DC in 1907.

Backed by the resources of the USA's wealthiest museum,

that same year he launched a series of field expeditions

deep into the Rocky Mountains, hunting for fossils.

The site he eventually discovered a year later

can be viewed from nearby Emerald Lake.

It registers as little more than a tiny slash of exposed rock

among the shaley slopes of Mount Burgess.

And that's the nearest all but the hardiest hikers will ever get.

To make the daunting journey up to 8,000 feet,

I'm taking my chances with another mode of transport.

Travelling with me is one of the world's foremost experts on the Burgess Shale.

Jean-Bernard Caron from Canada's Royal Ontario Museum.

The flight is wondrous.

Rarely does the local weather allow such a panoramic view

over the Canadian Rockies.

I'm told conditions like this are so rare,

no-one has landed a helicopter in the small mountainside quarry

that now bears Walcott's name, for several years.

It's a long time since I've been here and it still amazes me

that Walcott was able to locate this fossil bed

in this vast area of exposure

and hone it down to one particular place.

Walcott's quarry has since been expanded several times over.

But the original wall he excavated still stands today.

So this is one of the holy sites of palaeontology.

Walcott's original quarry.

That's right. This is the wall of this quarry as he left it

when he last came to this place in the 1920s.

And you can see all these bands here which represent like a rapid burial

of, you know, mud that will have entombed a lot of fossils.

And this dark band here, it looks like,

almost like a layer of chocolate in a chocolate cake, doesn't it?

-And like that chocolate, it's rich - in fossils.

-Extremely rich.

The richness of the discoveries Walcott would make

over the next 15 years, would astound the scientific world.

To understand their impact we must go to the other side of the world,

to a few decades before Walcott was born.

The rugged Pembrokeshire coast of Western Wales

is a place I know well.

It's composed of rocks as old as the Burgess Shale.

These are some of the most magnificent cliffs in Britain,

on the tip of Western Wales.

In the 19th century they yielded some of the first fossils,

the oldest fossils, that had ever been found in the United Kingdom.

They were called Cambrian because Cambria was the Roman name for Wales.

Nowadays, all around the world Cambrian is recognised

for this very, very important early period in the history of evolution.

Now we're going to sneak ashore to see if we can actually discover

some of these very ancient fossils.

And we're just hoping that the notoriously fickle Welsh weather holds out for us.

Geologists first mapped these rocky Cambrian coves in the 1860s.

They were the first to uncover some of the oldest fossils

in the world - fossils that include my own speciality.

The trilobites.

Hard-shelled and with segmented bodies,

they moulted as they grew like modern-day crabs or lobsters.

These extinct marine invertebrates were one of the most successful

and diverse groups that ever lived.

But finding them usually involves a drenching of one kind or another.

God!

Ah-ha-ha!

An empty rock.

Trilobites have been preserved here

because they possessed a hard exoskeleton.

Such hard parts are the raw material of most fossils.

But they are not common.

Eventually my diligence and perseverance are rewarded.

Ah-ha! Not a bad break, actually.

But these are some of the hardest rocks to find fossils in.

I've been looking for a solid hour and I've just found a hint,

just a fragment, but a large fragment, of this trilobite animal.

It's exciting to find even that - to think that it's survived

more than 500 million years of the vicissitudes time can throw at it.

Fortunately, thanks to the National Museum of Wales,

here's one someone else found earlier.

This magnificent specimen was found by a lucky collector in this very locality.

It's a trilobite, of course. It's Britain's largest trilobite,

which grew sometimes to nearly

three quarters of a metre in length.

It's name, Paradoxides,

because the original discoverer

found it somewhat paradoxical.

A high number of trilobite fossils found here in Wales

helped convince 19th century scientists that trilobites dominated the Cambrian world.

Almost to the exclusion of anything else.

Trilobites were also some of Walcott's first finds in the Rocky Mountains,

though their unusual features piqued his curiosity.

Today, the world's premier collection of Burgess Shale fossils

is housed in Canada's Royal Ontario Museum.

Almost all are tucked away behind the scenes,

awaiting a new gallery to show them off in all their glory.

In the meantime, while funds are raised,

they're kept under the watchful eye of Peter Fenton,

whose domain includes millions of years of fossil history.

So we just come this way through the vert prep lab

and we've got everything from people prepping casts, cleaning up casts

and moulds, to actually prepping specimens.

And then just everything requiring a lot of patience and a steady hand.

I feel rather like a hungry boy in Willy Wonka's Chocolate Factory.

And here we are! So these are the invertebrate fossil collections.

-And then...

-Oh, look at that! That is something.

-That's one of our favourites.

-Sea scorpions - a whole line.

-Yes.

It's a death assemblage, I think, because they're all just lying there

un-moulted, all the bits and pieces still in place.

Plus we've got, you know, plants, animals. It kind of...

-Some of these things are like pieces of sculpture, aren't they?

-Oh, they're beautifully prepared.

So... This is just one of the many rows, upon rows, upon rows

of Burgess material. We probably have upwards of 150,000.

-150,000?

-Each specimen marked with the level it comes from.

-Yeah.

I know from my own experience if you don't mark every piece of rock,

-you put it down in the wrong place, you're doomed!

-Well that's it.

So we have some beautiful specimens.

Amid these vast collections are also some old friends,

fossils and scholars alike.

-Er, trilobites down this way.

-Oh!

Like myself, David Rudkin is a trilobite man.

So this is the kind of slab that makes a trilobite man's mouth water.

In fact, I want to take it home.

Several specimens dotted at various angles,

and it's this, isn't it, that brought Walcott out West?

Eventually yes, after others had published and written on these,

Walcott took some exception to both the identity

of some of the trilobites and their age, and wanted to find out

for himself what was really going on, and this is what he would have seen.

But Walcott would soon discover trilobites

like he'd never seen before.

Well, this is the kind of regular Cambrian, if you like, isn't it?

-Indeed it is yes.

-And yet here we have a Burgess Cambrian,

and there's the same trilobite, the hard parts,

the shell which is all you normally get - but, in addition, limbs.

Exactly yes. This is what sets the Burgess Shale apart

from virtually all other Cambrian sites,

or it certainly did at the time of its discovery,

is that there are parts of animals, including trilobites, that preserve

not only the hard shelly bits but the soft parts of the anatomy.

So on this I can see antennae.

Yes, and at the front of the animal there are a pair of limbs,

but they're modified as antennae, so there's this pair

of feeler-like structures that come out the front end of the trilobite,

just like many modern arthropods that have that same set of structures of the front end.

But there's something rather special about this particular trilobite?

This particular one has not only a pair of antennae extending out,

the feelers from underneath the head shield,

but there's also a pair of antennae that stick out

the back end of the animal, identical, or more or less identical,

to the ones at the front.

And these are the cerci,

or antennae form like appendages sticking out the back end,

presumably allowed the animal to sense

what was going on behind it as well as in front.

Which could have been useful in a sea in which there were...

-Large predators.

-..quite serious predators.

Yes indeed, yes that's right.

The first fossil Walcott described to science

is still to be found in his quarry today.

He named this little creature, Marrella.

Walcott knew he hadn't found a trilobite

but still tried to compare it with something familiar,

in this case a shrimp-like crustacean.

I've got before me the lace crab.

It's preserved as a kind of silvery sheen

on the surface of the shale.

It's an exquisite little thing. It's no bigger than a small coin.

One of the things that Walcott noticed immediately

was that it had segmented limbs...

..which meant it was an arthropod.

It was an early member of that great group that includes crabs

and lobsters and insects and spiders today.

'In fact, Walcott had not unearthed a relative of the trilobites

or even another crustacean,

but a different kind of arthropod altogether.

But in the pursuit of trying to convince a sceptical world,

he added artistic skills to his paleontological flair.

This is the first scientific description of the lace crab

in a publication of the Smithsonian Institution.

They themselves are almost works of art.

And to a certain extent works of artifice as well,

because Walcott took photographs and then retouched them very,

very carefully to make the limbs more obvious.

They were generally very, very honest interpretations,

but it is art slightly improving upon nature,

and subsequent work showed where his errors were

and where art had perhaps exceeded fact.

But nonetheless, they still remain

a pleasure to look at after all these years.

It took Walcott three years to publish his account of Marrella

and his carefully retouched photographs

subtly emphasised crustacean features.

One of the things that held him back was the apparently different

appearance of the fossils of Marrella.

Walcott later realised that this was a clue to the calamity

that had miraculously preserved these soft bodied creatures.

In search of the unusual event that created the Burgess Shale,

I have come to University College, Dublin.

Here, Dr Paddy Orr studies the geochemical processes

of decay and preservation, called taphonomy.

He's going to show me why being buried alive

was key to their preservation.

Well, it's an arthropod like many Burgess Shale fossils.

-And it's Artemia, the brine shrimp.

-Yeah.

Sometimes called a sea monkey.

-And this is one that's just died.

-That was two days.

-Two days.

-Two days after death, yeah.

-And at this stage I can see it's all nicely filled out.

-Yeah.

-You can see the limbs along here.

-Yeah.

-You can see the eyes, even the antennae.

-Exactly.

And you can see the flesh all the way along

each of the antennae and the appendages on the trunk,

and they're all neatly lined up in a steady row after each other.

-Well, what happens when you allow time to take its course?

-OK.

So, these have been decaying for two weeks now, yeah.

-Oh, goodness me, yes.

-It's miserable looking, isn't it?

The gut has completely disintegrated into a series of pieces

and you see the way all the flesh inside the cuticle

has essentially shrivelled up...

-Turned to a mush.

-..mushed up, exactly.

And all the appendages themselves are now all spread out...

-On either side.

-..collapsed onto the surface, yeah.

-It's flattened?

-Exactly, and that tells us a very important point,

which is these are all coming to rest in their most stable orientation.

They're collapsing down onto the surface.

So, if you had a situation where, inside a bed,

the animals were in all sorts of different orientations,

it's a sign they haven't settled down to the surface,

they've been carried along in some sort of event bed

and buried rapidly in all sorts of higgledy-piggledy orientations.

The apparently random orientation of fossils

suggests the creatures of the Burgess Shale

were engulfed by undersea landslides,

possibly triggered by earthquakes.

If they had not been preserved at the moment of death,

just a few weeks later there would have been nothing left of them.

Well, let's run time on a little bit further and see...

-OK. So that's three weeks.

-Oh, my goodness!

-That looks like brine shrimp soup to me.

-Yes, it's not far off.

It is absolutely right.

Put it under the microscope and we'll see

if we get any sort of detail out of it at all.

-Oh, yeah, there's a few...

-There we are.

-..little wisps.

-The preservation window has now gone away.

-Exactly.

Look how little time it took to do that.

Three weeks at a constant temperature. It's amazing, isn't it?

So that shows what a miracle the Burgess Shale really is.

Absolutely, absolutely.

Often accompanied by his family,

Walcott continued excavating the Burgess Shale

until he was 74 years old.

He had proved the Cambrian seas were thronging with life.

But the sheer number of specimens Walcott discovered,

some 65,000 in all,

meant few questioned his efforts to relate them

to animals already known to science.

A case in point is Anomalocaris.

This is a detective story and the story starts,

like all good stories, with a clue.

When the Canadian Pacific Railway was pushed through the Rockies,

a fossil was discovered.

It was called Anomalocaris,

meaning something like anomalous or strange shrimp.

And Walcott thought it was something to do with the arthropods,

those animals with jointed legs.

Could this be the leg of a very large arthropod?

But nobody really knew what it was.

Walcott, of course, named lots of other fossils

from the Walcott quarry.

And this is the second clue in the story.

Which he called Peytoia.

It's a strange kind of rather large round object.

You can see why it might be thought to be a jellyfish

because it's got radial symmetry and lots of creases running around it,

and a sort of ziggy zaggy hole in the middle.

There was even a third one.

It's called Laggania.

A sort of flappy, rather indefinite, flappy looking thing.

And so the story remained for many years

until the specimens were re-studied.

It wasn't until 1966, long after Walcott's death,

that a team led by Professor Harry Whittington of Cambridge University

began to re-examine the Burgess Shale fossils.

And what they found would turn our understanding

of the Cambrian world on its head.

By looking at the fossils with fresh eyes

they were able to make unexpected connections Walcott had missed.

And one of the first things they found was that Anomalocaris,

Peytoia and Laggania were not, in fact, separate creatures at all.

Now, even in palaeontology you have the equivalent of a Rosetta Stone,

something that puts all things together

and enabled you to translate and understand the meaning of a fossil.

And so it was with this particular collection.

My old prof, Harry Whittington, and his student,

Derek Briggs, made the discovery.

They found, on one and the same specimen,

they found the Peytoia, the jellyfish mouthparts,

the limb, as it now was, and at the back end, the third element.

It was discovered that they actually

all belonged to one very large fossil.

But if we really want to see what this animal looked like...

..we need to bring it back to life by gently...

..putting some water on the specimen like this.

And there, emerging from the rock...

..the body, the great appendages, they are,

great graspers at the front reveal what a huge animal this was.

It was the top of the Cambrian food chain, a predator.

In its own way as remarkable as Tyrannosaurus Rex.

What a creature!

'Anomalocaris Canadensis was the alpha predator in its day.

'Still more than 250 million years before the dinosaurs.'

The realisation that three separate creatures were all parts

of one large predator helped change how the Cambridge team

looked at the creatures of the Burgess Shale.

Suddenly they weren't looking for relatives of trilobites

or other known animals,

they were looking at a lost world of designs for living

previously unknown to science.

Recreated here at several times their actual size,

together they became known as Weird Wonders.

Among the many animals of the Burgess Shales,

there are one or two undoubted Weird Wonders,

and one of the weirdest of all, no bigger than a shrimp, Opabinia.

You see the blobs there at the front, those are the eyes,

no fewer than five eyes.

And at the front it has a great appendage that stretches out...

..rather like an elephant's trunk,

and seems to have a grasping organ at the front.

So on this wonderful specimen,

the trunk appendage is thrown back over its shoulder really,

and along the side of the body a series of flaps, presumably used for

propelling the animal through the water, so it looks like a predator.

Of course it excited much debate

about where it fitted

into the animal kingdom.

But whatever the answer is, this remains one of the most

extraordinary and exciting animals from the Burgess Shale.

This new world of bewildering creatures, all existing at a time

previously thought to be dominated only by a handful of animals,

provoked much hard thinking in the scientific community.

One iconoclastic palaeontologist and best selling writer,

Stephen Jay Gould, seized upon the findings and controversially

argued they required a wholesale reassessment of evolutionary theory.

If Gould was right

and the Cambrian period explosively threw up new designs...

..what could have triggered it?

The Cambrian explosion has since been explained

in a myriad of ways, from tectonic shifts to changes in DNA.

But two of the most convincing theories are based on

what can be thought of as small physical changes which had

a massive knock-on evolutionary effect.

My first stop is the British Optical Association

and a tiny private museum

that contains lenses of every conceivable type.

Here, Dr Andrew Parker of the Natural History Museum,

tries to convince me he has solved the mystery.

What brought you particularly to be interested

in this particular problem?

It was looking at vision today, looking at eyes

and looking at colour,

and how far we could actually take that back through time.

We can see that there are eyes through the fossil record.

So I began to look at where was the first of those.

And that took me right back to somewhere in the early Cambrian,

to the very first trilobites.

Well, of course we've got the trilobite here, this is

a 400 million year old one

and this shows the lenses on the eyes particularly well.

Well, of course trilobite eyes are compound eyes,

that is they're composed of many lenses,

so they see the world in a slightly different way.

I mean this toy...

gives me lots and lots of different images.

Each facet of the compound eye would have seen its own particular segment

of the environment, and those segments would have been

added together to form an image through a number of pixels.

It's only when that lens evolved they have a whole image to decipher.

Whereas previously it was just shades of light and dark.

Before the evolution of complex lenses, some creatures had

eyelike organs that could detect the difference between light and dark.

But the ability to see shape and depth was revolutionary.

So there was a time, what shall we say,

a time almost of darkness, and then suddenly

they could see the world and other things in the world could see them?

Certainly an image was formed on their retina and they could see

the animals around them and pinpoint them with accuracy.

It could see all the other animals as basically chunks of protein

waiting to be eaten.

Well, of course the lumps of protein also would benefit from having eyes

in order to run away.

Absolutely, so this triggered a visual arms race,

but basically the behaviour of animals were totally changing.

It was becoming more similar to the system of animals today.

So you would believe that the sight, the evolution of sight,

complex sight, was the crucial spark that provoked this tremendous burst

of evolution at the base of the Cambrian?

Yes, I do, and a part of that is based on how important vision is

today and how it's perhaps the most powerful universal sense

on earth now.

So in a nutshell, the eyes have it.

So, did the development of the eye, and the massive advantage it gave

predators, suddenly accelerate the rise of creatures that

could defend themselves, and lead to the demise of those who could not?

Perhaps.

But a development of another kind altogether might have changed

the very fabric of the Cambrian Seas.

What I have in front of me is a slab of Burgess Shale

and it's covered in what looks like spaghetti.

Well, it's not spaghetti, it's worms.

But the term worm is itself rather meaningless.

It covers a whole range of sort of soft squiggly things

that are zoologically speaking only very loosely related.

There are bristle worms, there are acorn worms, there are penis worms,

there are even worms that look like the ones you dig up

in your garden,

doing different jobs in the Burgess Shale sea,

some of them burrowing, some of them eating sediment.

They were a very, very important part of the ecology,

and some people believe that they may be even the reason

for the Cambrian explosion itself.

My next potential answer to what triggered the Cambrian explosion

takes me back to the coast of ancient Cambria to meet

Dr Martin Brasier of Oxford University.

His surprising solution to the puzzle takes guts - lots of them.

Well, Martin, I can see on the shore here a lot of green slime or scum.

Er, yes this is formed by phytoplankton.

You can see that the hundreds of little cells have been caught

to form bubbles that are blowing in the wind.

So this is a very important lifestyle within the current

marine habitat?

It's absolutely fundamental to many of the things

that are going on here, the sandy shore.

Most of the food is coming from these algae,

-this phytoplankton and just here in fact...

-Ah!

..we can see one of these creatures, in fact there are two here...

-Oh, I can see them here.

-..just emerging from the sand.

The worm is living inside the tube almost entirely made

of tiny pieces of seashell.

And waiting for this, for dinnertime to arrive

and here it is, here's dinnertime coming out across the worms now.

So here's a good example of a lugworm burrow here.

Let's get down and have a look at it.

And you can see this little depression here is where the worm

takes the water and the sediment in, it's formed a great U-shaped

burrow underneath.

And there's a little worm called the lugworm sits at the bottom here,

drawing the water in down here, and full of bacteria

and organic matter and it actually uses its through gut,

the digestive tract, and then it excretes it at the surface here.

-It, er, extrudes it...

-Extrudes it.

-..cos it comes out as a kind of pipe, doesn't it?

-Yes.

OK, you see the water being squeezed out here,

I'm up to try and break it.

Oh...

It looks like an earthquake.

Er...

Could be...

It must be in here somewhere.

There's a lot of hard work trying to find this elusive worm.

Ah, what's that, something?

Oh, here we are, this is the lugworm, er...

and you can see the sort of staining from the food and the bacteria

and it's contracted now to try and make us... Make it less of a target.

-I think we ought to put it back, don't you?

-There we go.

And it looks happy.

So come and see these rocks.

Oh, yeah, I can see it looking quite promising

just at the back of the beach.

Mind the slippery weed.

A great mass, er, of worm burrows, you can see...

It's a sort of tubular mottling, isn't it?

It is. Each of these represents the activity of an individual worm,

burrowing through the sediment,

and it's thought to be the activity of a worm forming a very shallow

U-shaped burrow, moving the burrow up and down...

-A little bit like a lugworm?

-A little bit like the lugworm.

So it's gradually turning the shallow marine environment

into something like a soil, so they're making the whole surface

of the planet much more habitable.

Yes and er, I would have thought that their bringing

the nutrients up to the surface and changing the way that the oxygen

was moved down into the sediment,

absolutely transformed the nature of the marine world at this time.

The development of the gut and the growth of a worm population

extended the food chain into a new dimension - into the sea floor.

In turn, this helped change the chemistry of the seas,

creating opportunities for new species to thrive and, just maybe,

stimulating fast evolution.

Have you looked at any of the Burgess Shale...?

A recently discovered Weird Wonder

helps support just how important the evolution of the gut was.

Lorna O'Brien of the University of Toronto talks me through

a creature commonly known as the Tulip animal.

Well, Lorna, the first thing to say is the Tulip animal,

well, why isn't it a plant?

It certainly looks very much like a plant, but it has features

that lead us to believe that it has a stomach and a digestive tract.

How is it actually put together then, this remarkable animal?

So these are probably active filter feeders, so unlike many filter

feeders that passively wait for water to pass over them to capture

the food, these were probably actively pumping from

-the base of it.

-Oh, they suck water in?

Yes, so we have one specimen which is beautifully preserved,

actually the cross section of the base of the animal,

and that shows six holes.

And there was also another hole right at the top of the animal

which is interpreted as the anus, so where the food particles are excreted

once it has passed through the stomach and the digestive canal.

So if I used the term, Weird Wonder,

-I might actually be accurate.

-Yes.

I think definitely we could call these a Weird Wonder.

We have nothing else like these at the Burgess Shale

or in any deposit worldwide.

And how big does it grow?

They're actually one of the larger Burgess Shale animals, so...

Oh, my goodness, it looks like a golf club there,

-doesn't it, somewhat?

-Yes, so this specimen here is 25cm in length

and this is actually one of the largest Burgess Shale animals

or specimens that you will find.

But we also have ones that are

no more than a centimetre or 15mm in length.

And the Tulip animals often grew and reproduced in large groups.

So we may not have a plant here

-but we may have one of the earliest gardens?

-Yes.

And a stunning garden at that.

So, in the final analysis,

what triggered the explosion of life in the Cambrian seas?

Was it a change in the levels of oxygen in the atmosphere

or chemistry in the ocean?

Was it perhaps the appearance of animals with sight?

Or was it the activities of burrowing worms?

Or maybe, at a fundamental level, a change in the genome?

Perhaps we'll never know, but what we do know is that the Cambrian

evolutionary explosion changed the course of life on earth forever.

By the late 1980s many scientists agreed with Gould that the

Burgess Shale proved the reality of the Cambrian evolutionary explosion.

But questions remained about many of the creatures themselves

and their relationship to known animals.

By now responsibility for excavating at the site had passed

from Whittington's Cambridge group to a new Canadian team

led by Dr Desmond Collins of the Royal Ontario Museum, or ROM.

The scale and scope of the ROM's fieldwork dwarfed anything

that had gone before it...

..extending the site several times over

and amassing 150,000 new specimens.

And helping the team of professional palaeontologists were fresh-faced

volunteers, including a young Frenchman called Jean Bernard Caron,

who would later take over as expedition leader.

Ah, so here we are at the largest hole...

the one below the Walcott level.

Yeah, actually, we are standing here about 5m below

the original floor of the Walcott quarry.

This is older strata, newer strata up above us.

And as you can see there's a lot of drill marks here, there were...

By 2013 the number of identified species had risen to more than 200.

And using pioneering techniques, the ROM has been able to analyse

the Burgess fossils in more detail than ever before,

with revealing results.

This method using polarising photography achieves

the sort of clarity only seen before with Walcott's famous,

if slightly dubious, touched up photographs.

Such techniques have enriched our understanding

of the Burgess Shale's Weird Wonders.

And recently the discovery of other Burgess Shale-like sites

around the world has proved that the same marine fauna was widespread.

They confirmed the Cambrian explosion

because they include creatures comparable to those

of the Burgess Shale.

Some of the sites even help elucidate longstanding

Burgess enigmas.

As a result, many scientists now conclude that

some of the famous Weird Wonders might not be so weird after all.

I well remember when this animal was unveiled to the scientific public.

Everybody laughed.

It was the weirdest of the Weird Wonders.

An animal called, Hallucigenia, as if it always belonged

in the realm of the imagination.

And then, of course, it defied classification

and this animal was shown wandering around on spindly little spines

with these strange organs on the back,

feeding organs originally.

That's right, the food was thought to be transported

from one of these tentacles to the head.

But we now know that was all wrong.

It was wrong indeed,

and the scientists discover a second row of structures like these ones

here, with small spines at the ends, so now it was not just

a single row, but two rows, and those structures were interpreted as legs.

So in fact another row of these was found by excavating

on the original fossils,

and these became legs, so the animal...

was turned over.

That's right. The head and the back are still quite puzzling today.

-You still don't know which is front and back?

-No.

So upside down certainly, and back to front possibly?

That's correct. We still don't understand it very clearly.

So this model is more than life-size.

This is one of our specimens.

-Is that all?

-That's it.

Ah, but under the microscope

it reveals wondrous details.

Absolutely, in fact it turns out that these spines are preserved

in other fossil deposits all across the world,

and so therefore we now understand this animal to have a much bigger

family tree than previously thought.

Today Hallucigenia's distant relatives live not in the sea,

but on land.

Like this charming velvet worm from the tropical forests of Australasia.

It seems Walcott's attempt to make the Burgess fossils relate to

known animals might not have been completely misguided after all.

No matter how weird or wonderful these Burgess animals might seem,

we now know that they are related to animals still living today.

A list that includes species

as varied as squid, starfish,

scorpions and even

backboned animals like ourselves.

Not all of the new discoveries are ancient fossils.

And Jean Bernard shows me

some of the more unusual treasures that have been found near the site.

Well, there's more history in the Walcott quarry,

the history of the great man himself.

That's right. All this memorabilia were collected by

the Royal Ontario Museum expeditions, and they found this glove here

which is a small glove and probably belonging to Helen Walcott.

Oh, so, the expedition was a family affair.

It was indeed. So Walcott took his wife and children

to the quarries and they all participated in finding fossils.

But here is a remarkable example of an artefact found in the quarry,

and that was found in a block of ice in 1995, and...

Oh, goodness, and a picture of Teddy Roosevelt on the front.

So, when, when we find this, we can deduct that Walcott was actually

using this newspaper to pack fossils,

not just to read the news there, it would be...

No, no, no, so it's... Well, some things never change,

we still use high quality newspapers to wrap fossils today.

Absolutely. The beauty with this is you know what Walcott

was doing and what he was eating as well.

Pure shamrock lard, it says.

In National Parks the rules are that you have to leave the camp

as you, you found it, so clean and pristine.

But at the time that was not the case, so Walcott left, you know,

all these piles of teapots and cans and so on and so forth.

Well, I'm rather glad he did.

It's given us more history that we wouldn't otherwise have had.

Absolutely.

It's a profound and rather edifying thought that many of the creatures

that still swim in Pembrokeshire's rock pools owe their existence

to the unusual creatures first discovered half a world away.

Perhaps a good place to summarise our continuing connection

with this ancient Cambrian past,

can also be found on the menu of the local beach's snack bar.

This might be the perfect spot for my Burgess buffet.

Hello.

Have you got per chance some arthropods, like crustaceans

will do, maybe some molluscs and some famous Welsh laverbread?

Yeah, yeah, we've got all three. You're in luck.

Well, that would be a truly Cambrian repast.

And I've actually got cooking here a little bit of lobster

-and some spider crab.

-Oh, well, that'll do just fine.

-All fresh, just off the beach here.

-Oh, lovely.

Right.

The seaweed of course, laver, has been around since before

the Cambrian, and we can trace back

the arthropods and the molluscs to the same time.

There you go.

Oh, well, so it's a small diet perhaps,

but might be a tasty one, let's have a go.

Mmm, delicious.

Well, I suppose I ought to try the mollusc as well.

There you are, there we go.

Well, it's a wonderful thing to think of all of these organisms

still being found just off the Cambrian coast.

Delicious.

Today, more than a century after Charles Doolittle Walcott

first set out from Field,

it is difficult to appreciate just how brave and lucky he was when

he ventured into the wild peaks of the Rocky Mountains to find fossils.

The site he found made scientific history,

revealing the full experimental complexity of early animal life

for the first time,

and helping to change

and deepen our understanding of how evolution works.

These tiny, beautifully preserved, soft bodied creatures recall

a time when our planet was still a water world.

When animals were still a set of fully functioning prototypes,

while we humans were an experiment still more than 500 million years

in the future.

In the next episode, I venture forth into the arid North of China,

in search of more miraculous fossils from a hidden period of evolution.

It's the oldest known feathered dinosaur.

A lost world where dinosaurs sprouted feathers

and evolved into the first true birds.