Walking Through Time - First season

This is Shropshire.

My favourite part of the world to go walking in,

and one of Britain's hidden jewels.

It's a landscape that bears the scars of almost every geological era.

Right up to the glaciers of the last ice age.

Glaciers so high they would have almost buried these mountains.

All you would have seen would have been these jagged ridges of rock poking

up through the top of the ice.

14,000 years ago as that glacier retreated the land below became home to

mammoths, and not just any mammoths but Britain's last mammoths.

We know this because the remains of five animals were found 30 years ago

in a quarry near Shrewsbury.

Previously we'd thought that the last ice age had driven mammoths out of Britain for good,

but this was proof they had returned and thrived after the ice had gone.

So what eventually killed them off?

As an evolutionary biologist this mystery has always fascinated me.

Some experts believe that humans hunted the mammoths to extinction,

but is that really true?

Could there be another reason behind their disappearance?

To try and find the answers to these questions I'm going to walk in the

footsteps of those creatures as they made their last journey through the

landscape below.

I'll piece together the forensic evidence.

I've got the remains of a 14,000 year-old maggot.

And I'll take to the air to picture how that giant glacier changed this

part of Britain.

We've just reached a little over 500 feet up in the sky.

That's not even as high as the ice sheet reached.

I'm going to walk through time and try and bring these magnificent

megabeasts back to life.

Sat on the Welsh border an hour's drive from Birmingham the landscape

between Shrewsbury and Church Stretton is prime walking country.

Around 20,000 years ago it was the edge of a vast ice sheet that extended

across most of Great Britain.

When that ice melted away it revealed a wide flat valley here

which soon filled with tundra-like grassland.

That primitive pasture attracted the woolly mammoth.

My walk will follow in their footsteps and track that retreating glacier.

The walk begins at the iconic Shropshire hill fort, Caer Caradoc.

From there I'll cut across the plain and onto a seven mile range of hills

known as the Long Mynd.

Then I'll head north through Lyth Hill Country Park before finishing at

Bomere Pool. It was formed by the melting glacier and it's right next door

to the quarry where the mystery of the mammoths was unearthed.

And before I start my walk I'm going to check out where they were

discovered, which was here at Condover Quarry, near Shrewsbury.

The machines and diggers here are harvesting gravels and sands which were

deposited during the last ice age.

In September 1986, a local woman called Eve Roberts was walking her dog

through this quarry when something caught her eye.

She saw a strange object poking through the mud and rubble.

She wasn't sure what she'd seen,

she thought it might be of interest

to local museum services and she was right.

What she had found were the remains of the most complete woolly

mammoth skeleton ever to be found in Britain.

But more than that,

her find revolutionised our understanding of ice age Britain.

Until Eve's mammoth came along,

we had thought that mammoths had left Britain for ever before the last

glacial maximum when the ice sheets came down.

But it turned out they came back.

Mammoths returned to Britain as the ice sheet retreated.

This meant there were mammoths in northern Europe

as recently as 14,000 years ago.

This was sensational news.

Even Blue Peter turned up to film the bones being uncovered.

One of the scientists at the dig back then was Professor Adrian Lister.

He's not only one of Europe's leading experts on mammoths and their ice

age world, he's also my boss at the Natural History Museum.

So Adrian, of course the last time you were here.

1986. 1986. It looked very similar?

Well, it was pretty different then actually because all this area has been

dug out, since, for gravel.

It's 30 years of gravel extraction have happened since.

But I think that the water we can see here which is now a pond was the

quarry where the bones were found.

Eve was the local lady who was just walking her dog around here one

morning and spotted these large bones in the middle of the quarry.

She didn't know what they were but she had the foresight to ring

the local museum, she thought it might be something interesting.

And sure enough, you know, it was practically complete mammoth skeleton.

Did you know that straight away?

I mean, did you see it? Yeah. What was there, what did you actually see?

The day that I turned up they'd already got some of the large bones out

including the big jawbone.

And the jawbone with the teeth in is absolutely diagnostic,

and I could see that it was a woolly mammoth skeleton.

And the bones were incredibly fresh.

I've never since, in 30 years,

been involved in something as exciting as that.

Because finding bits and pieces of these animals is not uncommon in gravel

sites like this. You find an odd bit of tusk, odd bit of tooth.

But to find a complete skeleton lying in the ground like that,

and several of them together is almost unique, actually,

and was amazingly exciting.

So what was the moment you realised you had more than one mammoth?

Well, there was the moment in the quarry, it was right at the end,

we had about three weeks to excavate and I think it was on the very last

day, we got the big diggers to go down into the middle of the quarry and

dig out the last remaining patches of the mud and clay that the mammoth

bones were in. And I remember a moment when this enormous digger had dug

up a huge scoopful of mud,

and I could see sitting on the top was a baby mammoth jaw.

So I told the guys, like, stop immediately.

Stop! And we went over and had a look and sure enough that was a juvenile

mammoth that we later identified as about three or four years old.

And then about ten minutes later they were digging again and another baby mammoth jaw came up.

So by that point we knew we had the adult, two juveniles,

and this was the very last day of the excavation,

so it was really lucky that we got them.

You just sort of think, you know, that was the last day,

if you only had more time, they were still finding things.

I'm sure there's more stuff there.

I mean, we found an enormous amount, considering the limited time,

we were very successful.

But I'm sure there's more of the same under this landscape, no question.

Five different mammoths were eventually identified from the tumble of

bones in the gravel pit.

But how did they die in the first place?

And what can they tell us about the big question,

why did the woolly mammoth go extinct?

My walk starts at the historic hillfort of Caer Caradoc,

which overlooks the town of Church Stretton.

This part of Shropshire isn't just about the mammoths,

it's also packed with amazing geology and history.

What a spectacular place to start my walk.

This is Caer Caradoc.

It's got a commanding view all over the local hills and valleys and I

think because of that view this is also the location of an Iron Age hill fort.

Local legend has it that Caractacus, a chieftain from these parts,

fought his last stand against the Romans here.

If he did, it didn't go very well.

He was defeated and eventually dragged off to Rome in chains.

Caractacus was due to be publicly executed but spoke so eloquently in his

defence he was pardoned and allowed to live in the city, where he became

something of a celebrity.

The fort is one of a number of Bronze and Iron Age settlements in the area.

It was first built here sometime between 600 BC and 100 AD,

placing humans in the landscape about 1,200 years after the mammoths died.

It's just about visible from the air,

the concentric circle defences showing up like rings around the summit.

In its day this was quite a sophisticated settlement.

With a spring-fed pool at the top of the hill providing a fresh water supply.

The fort's builders used the rocky outcrops here as part of the fort's

defences. They took advantage of a natural material which was laid down a long, long time ago.

Caer Caradoc is 450 metres of ancient volcanic rock.

Layer upon layer of lava flow and pyroclastic flows erupted from volcanoes

to the east and west of here 570 million years ago.

That violent past has gifted the area with an amazing geological record.

To help me understand it I have the best possible guide,

the man who literally wrote the book on the subject.

Local resident Doctor Peter Toghill is the author of The Geology Of Britain.

For him this landscape is a product of hundreds of millions of

years of geological change.

And when that process started Shropshire was in a very different part of the planet.

If you were here 600 million years ago you would have been

actually even colder than we are now because you wouldn't be in this

latitude, you'd be near the South Pole, near the Antarctic Circle.

60 degrees south of the equator.

And then for the next 500 million years Britain starts to move northwards

through the subtropics.

And when we go through the subtropics you get lovely limestones forming on Wenlock Edge.

Lovely shallow water coral reefs on Wenlock Edge forming in the

subtropics. And we go further north across the equator and you get coal

measures, and coal seams forming on Clee Hills over there,

lovely coal seams.

And then you go further North to the Sahara sort of desert belt,

you get bright red sandstones in Shropshire.

And then you come nearer and nearer to our present latitude.

It's 12,000km in 500 million years.

And if you do a few sums, that's about four centimetres a year...

That's pretty... Which is about what continental crusts and oceanic crusts move at today.

Imagine the landmass that would eventually be called Britain slowly

floating north across the earth.

At different points on its journey different layers of rock were

deposited, each one a unique souvenir of its travels.

These layers are visible today thanks in part to plate tectonics,

movements of the Earth's continental crust.

The effects of which can still be seen in a huge fault running through the county.

Way down in the valley, there, you can see the Church Stretton Fault,

it follows the line of the valley right down into south Wales,

down the valley, here.

And it goes under Caer Caradoc here and it goes along the left-hand side

of that hill, there, called the Lawley.

And up towards the Wrekin, which is maybe Shropshire's most iconic hill.

So it's a big fault.

The Church Stretton Valley follows this fault line creating a natural corridor

that would have channelled the huge glacier that arrived here with the last ice age.

You know, you'd be sitting here 20,000 years ago,

the ice would have maybe been 100 metres below the top of this hill.

And then maybe 17,000 years ago the ice started melting,

retreating slowly north.

And by 15,000 years ago,

it's quite a long way away and the mammoths start coming up the valley.

That's a wonderful thought, isn't it?

You think of that there, that kind of basin,

filled with these incredible beasts.

And that's where I'm heading next.

Down to the floor of the valley to walk in the footsteps of those prehistoric creatures.