ever to occur to a human mind.

The idea is evolution by natural selection.

And the genius who thought of it was Charles Darwin.

I'm a biologist and Darwin has been an inspiration to me

throughout my whole career.

His masterpiece, On The Origin Of Species, was published 150 years ago.

And it changed forever our view of the world and our place in it.

What Darwin achieved was nothing less than a complete explanation

of the complexity and diversity of all life.

And yet, it's one of the simplest ideas that anyone ever had.

In this series, I want to persuade you

that evolution offers a far richer and more spectacular view of life

than any religious story.

It's one reason why I don't believe in God.

I want to show you how Darwin opened our eyes to the extraordinary reality

of our world.

In this first programme, I'm going to tell you who Charles Darwin was,

explain how he discovered his theory of evolution, what it is,

and why it matters.

By the end, I hope to have convinced you of the truth

that evolution is a fact, backed by undeniable evidence.

And I want to give you a glimpse of the brutal elegance of the force

which, Darwin realised, drives evolution on...

..natural selection.

When Charles Darwin was born 200 years ago,

sailors and explorers were sending home

a dizzying array of specimens like these

from all parts of Britain's growing empire.

Every animal was believed to have a unique place in God's creation,

each made by God according to his perfect, unchanging design.

At school in Shrewsbury,

the young Charles Darwin was taught that God had created the Earth,

and all this rich variety of life just 6,000 years ago.

Today, thanks to Darwin, we know differently.

But even now, according to polls, four out of every ten British people

prefer to cling to the old ideas

and believe that God created our world

and every living creature in it.

I think it's scandalous

how little our children are taught about evolution at school.

A typical class gets just a few hours

to study one of the most important ideas in science.

This lot got me.

I went to meet a science class of 15 to 16-year-olds

at Park High School in London to try to open their eyes to Darwinism.

Why do we need to find out about evolution?

Why do we need to find out about evolution?

Because it is the explanation for our existence and because

it explains such a huge number of facts,

because everything we know about life is explained by it.

I believe in my religion

so whenever I read about evolution,

I can't understand it, I don't believe it,

I just, like, believe my religion.

Right, so you know what you believe when you start,

and any new book that says anything different,

you don't read it?

Even if you've got evidence,

I just like...I've found a stronger evidence,

which is the Holy Book, so...

So, the reason you believe it

is because that's the one you were told first?

'I can see that a few hours in the science lab is no match

'for a lifetime of religious indoctrination.'

I was brought up to believe it.

Is that a good reason to believe something?

Yeah, because I went to church since I was little.

Yeah, and it says it in the Bible.

Yes, but in the Hindu sacred scriptures,

it says something different, doesn't it?

Yeah, they're brought up to believe that...

So everybody should believe what they're brought up to believe

even though they contradict each other?

You can be made to believe something in science, and then,

you can be made to believe something in religious studies,

but it's really up to you what you believe.

You can't just say that...

Well, look, I hate this phrase, "made to believe", that's awful,

and I would hate anybody to think

I was trying to make anybody believe anything.

I'm asking you to look at the evidence.

Perhaps you haven't got a full impression

of how strong the evidence actually is.

Nobody has seen evolution take place over a long period,

but they've seen the after effects,

and the after effects are massively supported.

It's like a case in a court of law

where nobody can stand up and say, "I saw the murder happen",

but yet, you've got millions and millions of pieces of evidence

which no reasonable person could possibly dispute.

That's sort of the way it is.

'There's only one thing for it -

'I'm going to show them evidence -

'something they can touch with their own hands, see with their own eyes.

'Later, we'll see if I can make them think again.

'When Charles Darwin was a teenager,

'he would have been as much of a creationist

'as some of these children.'

Darwin was born into a prosperous Shropshire family in 1809.

His father was a doctor,

and keen that his son should follow in his scientific footsteps.

But the adolescent Charles,

more interested in shooting and fishing than academic prowess,

was contemplating an easy life as a country parson.

Luckily for him, and for us,

he had the opportunity to open his eyes to see the world.

In 1831, as a young man of 22,

Darwin's family connections got him a once-in-a-lifetime invitation -

a round-the-world voyage on the survey ship, HMS Beagle.

Over five years, Darwin collected hundreds and hundreds of specimens

to send back to the collections.

But increasingly,

he wasn't satisfied with just recording

the animals and plants he saw.

He was beginning to have doubts about the Biblical story

of how animals were created.

While ashore, riding across the South American flatlands,

Darwin amused himself

by chasing after rheas - shy, ostrich-like flightless birds.

But he was puzzled.

Why had God bothered to create

two very similar but slightly different types of rhea?

Had an original group of rhea split in two,

and once separated, started to develop in their own way?

The mystery deepened when Darwin noticed an even more marked effect -

on islands.

I was lucky enough to retread Darwin's footsteps

on the Galapagos Islands last year.

Here, he began to wonder

why God would have created distinctive kinds of tortoise,

finch or iguana on more or less identical small islands.

Were iguanas like these related rather than separately created?

Were they cousins of the similar but different iguanas on nearby islands?

This pattern of relationships

became even more intriguing when Darwin encountered fossils.

The evidence of fossils

would help Darwin develop a theory of life on Earth

far more wonderful and more moving

than any religious story of creation.

This team of American scientists

has uncovered the remains of two-million-year-old ground sloths.

Today, I'm joining the dig

because it was fossils like these

that made a huge impression on the young Charles Darwin

during his voyage on HMS Beagle.

To Darwin, they looked like ancient, giant versions

of animals he saw around him.

(MAN) The ground sloths flourished

for millions of years, and were quite successful.

- They were huge, weren't they? - Some of them were.

They were bear-sized, up to...almost rivalling mammoths and mastodons,

up to six metres in height when they reared up onto their hind legs.

(DAWKINS) What struck Darwin was how, apart from their enormous size,

the fossils closely resembled in every other detail

the skeletons of modern sloths living nearby.

(MAN) You can see similarities in the details of their teeth,

peculiar features that they share with modern armadillos,

modern tree sloths and modern anteaters.

We can infer that they are related to these animals.

(DAWKINS) The discovery of fossils was a huge challenge

to the religious orthodoxy of Darwin's youth.

What were these animals? When had they lived?

And why didn't they exist any more?

Some suggested that fossils were just God playfully ornamenting his world.

Others claimed

they were the bones of sinners drowned in Noah's flood.

But Darwin was one of the first scientists

to correctly identify them as long-dead species of animals.

He was starting to grasp that the Earth might be a lot older

than the Bible led us to believe.

And how had he realised this?