Darwin's Tree of Life 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.

Well, the year 2009 was

the bicentenary of Charles Darwin's birth.

And I think any naturalist,

any biologist will agree that his theory,

and his thought,

is the most important step forward in zoological science.

Before this book, the natural world and natural history,

and zoology, could be regarded as

a glorified form of stamp collecting.

You've got one animal, and then you've got another animal,

and you said it was slightly different from this animal.

But that was all. But this book made sense of those differences.

You know, if you look in the garden and you see a coal tit,

and a great tit, and a blue tit,

it just makes common sense to think that they are related.

And what Darwin showed you is that, of course they're related.

They evolved one from the other.

And not only that but actually,

birds as a whole evolved from reptiles,

and reptiles as a whole evolved from amphibians,

and amphibians as a whole developed from fish.

So it...

But he explains the mechanisms in which this happens in this book.

Which is one of the great books of the world.

So it was obvious I had to make a film about it.

Our earth is the only known planet that sustains life -

and it does so in abundance.

I have been fortunate enough, over the years, to travel to some of the

most extraordinary and remote places on earth to find and film animals.

This is the biggest flower in the world.

The Blue Whale!

It's the biggest creature that exists on the planet.

The sheer number and variety of animals and plants is astonishing.

Estimates of the number of different species vary from six million

to 100 million.

Nobody knows exactly how many different

kinds of animals there are here.

Wherever you look there's life.

There are often a multitude of variations on a single pattern.

Nearly 200 different kinds of monkeys, for example.

And 315 hummingbirds.

Nearly a thousand bats.

And beetles - at least 350,000 species of them.

Not to mention,

a quarter of a million different kinds of flowering plants.

The variety is astounding.

Even in this one small English woodland,

you might see four or five different kinds of finches.

Why should there be such a dazzling variety?

And how can we make sense of such a huge range of living organisms?

200 years ago, a man was born who was to explain

this astonishing diversity of life.

In doing so, he revolutionised the way in which we see the world

and our place in it.

His name was Charles Darwin.

This book - the Holy Bible -

explains how this wonderful diversity came about.

On the third day after the creation of the world,

God created plants.

On the fifth day, fish and birds.

And then on the sixth day - mammals, and finally man.

And when God had finished,

he said to Adam and Eve,

"Be fruitful and multiply and replenish the earth and subdue it,

"and have dominion over the fish of the sea

"and over the fowl of the air,

"and over every living thing that moveth upon the earth."

That made it clear that, according to the Bible,

humanity could exploit the natural world, as they wished.

This view of mankind's superiority

still stood when, in 1831, a British surveying ship, The Beagle,

set off on a voyage around the world.

On board, as a companion to the captain,

was the 22-year-old Charles Darwin.

They crossed the Atlantic and made landfall on the coast of Brazil.

There the sheer abundance of tropical nature

astonishes the new-comer,

as I discovered when I retraced Darwin's steps 30 years ago,

for a television series about the diversity of nature.

Darwin, as a boy, had been a fanatical collector of insects,

and here he was enthralled, almost to the point of ecstasy.

In one day,

in a small area,

he discovered 69 different species of beetle.

As he wrote in his journal,

it's enough to disturb

the composure of the entomologist's mind,

to contemplate the future dimension of a complete catalogue.

They went south, rounded Cape Horn

and so reached the Pacific.

And then, in September 1835,

after they had been away for almost four years,

they landed on the little known islands of the Galapagos.

Here they found creatures that existed nowhere else in the world.

Cormorants that had lost the power of flight.

Lizards that swam out through the surf to

graze on the bottom of the sea.

Darwin, who had studied Botany and Geology at Cambridge University,

collected specimens of the animals and plants.

The British resident in the Galapagos claimed that he

knew from the shape of a giant tortoise's shell,

which island it had come from.

If it had a rounded front,

it came from a well watered island where it fed on lush ground plants.

Whereas one from a drier island had a peak at the front which

enabled it to reach up to higher vegetation.

Were these tortoises, each on their separate islands, different species?

And if so, was each one a separate act of Divine creation?

The differences that Darwin had noticed amongst

these Galapagos animals were, of course, all tiny,

but if they could develop, wasn't it possible that over

the thousands or millions of years, a whole series of such differences

might add up to one revolutionary change?

On his voyage home,

Darwin had time to ponder on these things.

Could it be that species were not fixed for all time,

but could in fact slowly change?

On his return, he sorted out his specimens and sent them

off to relevant experts so that each could be identified and classified.

Most of the mammal bones and fossils he sent to Richard Owen.

Owen was one of the most brilliant zoologists of his time.

He was the first to recognise dinosaurs -

and indeed had invented their very name.

And he would later become the

creator and first director of the Natural History Museum in London.

Many of the specimens that Darwin collected are still preserved,

and treasured - here, among the 70 million other specimens

housed in the museum that Owen founded.

And here is one of them.

It's obviously the lower jaw of some great animal,

and when Darwin discovered it, it had bits of skin

and hair attached to it, so that at first it was thought to be

the remains of some unknown living species.

But now we know that it is a species that was

extinct for some 10,000 years - a giant ground sloth.

Owen examined it in great detail and eventually described it and

gave it the name of Mylodon Darwinii in honour of its discoverer.

But that mutual respect between two great men of science

was not to last.

Soon after his return from his voyage,

Darwin made his home here in Down House in Kent.

Here he wrote an account of his travels

and worked on detailed scientific treatises about corals

and barnacles, and the geology and fossils of South America.

But he also pondered deeply on what he had

seen in the Galapagos and elsewhere.

Maybe species were not fixed.

Every day, he took a walk in this small spinney that he

had planted at the end of his garden.

And it was here that he came to ponder

on the problems of natural history,

including that mystery of mysteries -

how could one species turn into another?

He noted that most, if not all, animals produce

many more young than live to breed themselves.

This female blue tit, for example,

may well lay a dozen eggs a year - perhaps 50 or so in her lifetime.

Yet only two of her chicks need to survive

and breed themselves,

to maintain the numbers of the blue tit population.

Those survivors, of course, are likely to be the healthiest

and best suited to their particular environment.

Their characteristics are then inherited.

So, perhaps over many generations - and particularly

if there are environmental changes - species may well change.

Only the fittest survive - and that was the key.

He called the process "natural selection".

That would explain the differences that he had

noted in the finches that he had brought back from the Galapagos.

They were very similar except for their beaks.

This one has a very thin, delicate beak which it uses to catch insects.

This one, on the other hand,

which came from an environment where there were a lot of nuts,

has a big heavy beak which enables it to crack them.

maybe, over the vastness of geological time,

and particularly if species were invading new environments,

those changes would amount to very radical changes indeed.

Darwin drew a sketch in one of his notebooks to illustrate his idea.

Showing how a single ancestral species might give rise to several

different ones and then wrote above it a tentative,

"I think".

Now he had to prove his theory -

and he spent years gathering abundant and convincing evidence.

He was an extraordinary letter writer.

He wrote as many as a dozen letters a day to scientists

and naturalists all over the world.

He also realised,

that when people had first started domesticating animals,

they had been doing experiments for him - for centuries.

All domestic dogs are descended from a single

ancestral species - the wolf.

Dog breeders select those pups

that have the characteristics that happen to please them.

Nature, of course, selects those young animals

that are best suited to a particular environment,

but the process is essentially the same

and in both cases, it has produced astonishing variety.

In effect,

many of these different breeds could be considered different species

because they do not - indeed they cannot inter-breed.

For purely mechanical reasons,

there's no way in which a Pekinese can mate with a Great Dane.

Of course it's true that

if you used artificial insemination you could get

crosses between almost any of these breeds,

but that's because human beings have been

selecting between dogs for only a few centuries.

Nature has been selecting between animals for millions of years,

tens of millions, even hundreds of millions of years.

So what might have started out as we would consider to be breeds

have now become so different, they are species.

Darwin, sitting in Down House,

wrote to pigeon fanciers and rabbit breeders,

asking all kinds of detailed questions

about their methods and results.

He himself, being a country gentleman and running an estate,

knew about breeding horses and sheep and cattle.

And he also conducted careful experiments with

plants in his greenhouse.

But Darwin knew that the idea that species could

appear without divine intervention would appal society in general,

and it was also contrary to the beliefs of his wife Emma,

who was a devout Christian.

Perhaps for that reason,

he was keen to keep the focus of his work scientific.

He made a point of not being drawn in public

about his religious beliefs,

but in the latter part of his life

he withdrew from attending church.

On Sundays he would escort Emma and the children here,

to the parish church in Downe,

but while they went into the service,

he remained outside and went for a walk in the country lanes.

Perhaps because he feared

that his theory would cause outrage in some quarters,

he delayed publishing it year after year after year.

But he wrote a long abstract of it

and then on July the 5th 1844, he wrote this letter to his wife.

"My dear Emma.

"I have just finished this sketch of my species theory -

"some sketch - it was 240 pages long.

"I therefore write this in case of my sudden death that you will

"devote 400 pounds to its publication."

He then goes on to list his various naturalist friends

who would be asked to edit it and check it,

and he ends the letter charmingly,

"My dear wife, - yours, affectionately, CR Darwin."

He continued to accumulate evidence

and refine his theory for the next 14 years.

But then his hand was forced.

In June 1858, 22 years after he got back from the Galapagos,

here in his study in Down, he received

a package from a naturalist who was working in what is now Indonesia.

His name was Alfred Russell Wallace.

He had been corresponding with Darwin for some years.

But this package was different.

It contained an essay that set out exactly the same

idea as Darwin's - of evolution by natural selection.

The idea had come to Wallace as he lay in his hut,

semi-delirious in a malarial fever.

But although his idea of natural selection was the same as Darwin's,

he had not spent 20 years gathering

the mountain of evidence to support it, as Darwin had done.

But whose idea was it?

In the end, the senior members of the Linnean Society

decided that the fairest thing was for a brief

outline of the theory from each of them to be read out,

one after the other,

at a meeting of the Society, here in Burlington House, in London.

The Linnean, then as now, was the place where scientists

studying the natural world held regular meetings,

to present and discuss papers about their observations and thoughts.

The one held on July 1st, 1858

was attended by only about 30 people.

Neither of the authors were present.

Wallace was 10,000 miles away in the East Indies,

and Darwin was ill and devastated by the death, a few days earlier,

of his infant son - so he was still at his home in Kent.

As a consequence, the two papers had to be read by the secretary and,

as far as we can tell, they made very little impression on anyone.

Darwin spent the next year writing out his theory in detail.

Then he sent the manuscript

to his publisher, John Murray, whose firm, then as now,

had offices in Albemarle Street, just off Piccadilly in London.

Murray was the great publisher of his day,

and dealt with the works of Jane Austen and Lord Byron,

whose first editions still line these office walls.

Darwin regarded his work as simply a summary, but even so it's 400 pages.

It was published on November 24th, 1859.

This is not a first edition - more's the pity.

First editions are worth literally hundreds of thousands of pounds.

This is a sixth edition - my copy, which I bought as a boy -

when I was 18 I notice, and it cost me the princely sum of one shilling.

The first edition of 1,250 copies sold out immediately

and it went for a reprint, and then another reprint and another reprint.

It's a book that contains very few technical terms -

it's easily understood by anybody,

and predictably it caused an outrage,

not only throughout this country but indeed all the civilised world.

What scandalised people most, it seems,

was the implication that human beings

were not specially created by God,

as the Book of Genesis stated,

but were descended from ape-like ancestors -

a notion that provided a lot of scope for cartoonists.

The leaders of the Church, headed by Samuel Wilberforce,

the Bishop of Oxford, attacked it on the grounds that it demoted God

and contradicted the story of creation as told by the Bible.

"That Mr Darwin should have wandered from this broad

"highway of nature's works

"into the jungle of fanciful assumption,

"is no small evil."

"I have read your book with more pain than pleasure."

"It is the frenzied inspiration of the inhaler of mephitic gas."

"Fails utterly."

Darwin's theory implied that life had originated in simple forms

and had then become more and more complex.

He knew perfectly well that the whole idea of evolution

raised a lot of questions.

In fact, some of those questions would not be answered

until comparatively recently,

but in his own time many distinguished scientists raised

what seemed to be insuperable difficulties.

And foremost among them was Richard Owen, the man who,

20 years earlier,

had named the extinct ground sloth in honour of Darwin.

Over the years the two men had developed a deep

personal dislike of one another and had quarrelled frequently.

It wasn't that Owen thought that the story of the Garden of Eden was

literally correct, but nonetheless he was a deeply religious man.

He had, after all, ensured that his museum which

would display the wonders of creation, echoed in its design

the great Christian cathedrals of medieval Europe.

And Owen knew about the diversity of life.

Indeed he had spent his whole career cataloguing it.

But even so, he refused to believe

that a species could change over time.

Owen did not deny the sequence in which all these

different species appeared.

But he believed that each was separate, each divinely created.

Darwin's theory, however, required that there should be connections

not just between similar species, but between the great animal groups.

If fishes and reptiles and birds

and mammals had all evolved from one another, then surely there must be

intermediate forms between those great groups -

and they were missing.

And then,

just two years after the publication of The Origin of Species,

Richard Owen himself purchased

the most astonishing fossil for his museum.

It had been found in this limestone quarry in Bavaria.

The stone here splits into flat smooth leaves that have been

used as roofing tiles since Roman times.

Most are blank.

But occasionally, when you split them apart,

they reveal a shrimp or a fish.

It's almost impossible to resist

the temptation of pulling down almost every boulder you see

and then opening it, like a book, to look at each unopened

page to see whether maybe it contains yet another fossil.

But this fossil was something unprecedented.

It is still one of the greatest of the treasures

that are stored in the Natural History Museum.

And this is it, it's called Archaeopteryx.

It has unmistakable feathers on its wings and down its tail.

So Owen had no hesitation in calling it a bird,

but it was unlike any other bird that anyone knew of.

Because it had claws on the front of its wings and -

as was later discovered -

it didn't have a beak but jaws with teeth in it.

And a line of bones supporting its tail.

So it was part reptile, part bird.

Here was the link between those two great groups

that was no longer missing.

Gosh, you really can see the filaments there.

Other examples of the same creature

show its feathers even more clearly.

We know from the bones of Archaeopteryx that it was,

at best, a very poor flyer.

So it's not surprising that eventually it was

superseded by more modern, more efficient birds.

And that's the fate of these links between great groups.

Eventually they become extinct and the only way we know

they existed is from their fossilised remains.

Even so, there is a bird alive today that illustrates

the link between modern birds and reptiles.

The hoatzin nests in the swamps of tropical South America.

There are caiman in the water beneath,

ready to snap up any chick that might fall from its nest,

so an ability to hold on tight is very valuable.

And the nestlings have a very interesting way of doing that.

The young still have claws on the front

of their wings, as Archaeopteryx did.

Here is vivid evidence that the wings of birds are modified

forelegs and once had toes with claws on them.

There's another creature alive today that represents

a link between the great animal groups,

a descendant of a group of reptiles that took a different

evolutionary course and evolved not feathers but fur -

the platypus.

When specimens of this creature first reached

Europe from Australia at the very end of the 18th century,

people refused to believe their eyes.

They said it was a hoax - bits

and pieces of different creatures rather crudely sewn together.

And yet in a way those early sceptics were right.

The platypus is the most extraordinary

mixture of different animals.

It's part mammal and part reptile, and so it can give us

some idea of how the first mammals developed.

When it comes to breed it does something that separates

it from all other mammals except one.

In its nest, deep in a burrow, it lays eggs.

It's this that links the platypus with the reptiles,

and this that entitles it to be regarded

as the most primitive living mammal.

So the links between the great animal groups are not,

in fact, missing - but exist both as fossils and as living animals.

Although the fossil record provides

an answer to the problem of missing links it also posed a major problem.

It started very abruptly.

The earliest known fossils in Darwin's time came

from a formation called the Cambrian and there were two main kinds,

these, which look like fretsaw blades and are called graptolite

and these like giant woodlice which are called trilobites.

Could it really be,

that life on Earth started with creatures as complex as these?

As a boy, I was a passionate collector of fossils.

I grew up in the city of Leicester and I knew

that in this area, not far from the city called Charnwood Forest,

there were the oldest rocks in the world, older even than the Cambrian.

So therefore, by definition, they would be without fossils.

There was no point in me looking for fossils in these ancient rocks.

There were, it's true, very rarely,

some rather odd shapes in these rocks, like this one here.

But they were dismissed as being some kind of mechanical aberration.

I mean, after all, how could there be anything living in these

extremely ancient rocks?

And then in 1957, a schoolboy with rather

more patience and perspicacity than I had, found something really

remarkable and undeniably the remains of a living creature.

And here it is in Leicester Museum,

where it's been brought for safe keeping.

It's called Charnia.

Who could doubt that this is the impression of a living organism?

It has a central stem, branches on either side.

In fact, it seems to have been something like the sea pens

that today grow on coral reefs.

Since its discovery a whole range of organisms have been

found in rocks of this extreme age, not only here

in the Charnwood Forest but in many other different parts of the world.

Fossil hunters, searching these rocks in the Ediacara Hills

of Australia had also been discovering other strange shapes.

At first many scientists refused to believe that these

faint impressions were the remains of jellyfish.

But by now enough specimens had been discovered to make quite sure

that, that indeed is what they are.

So now we know that life did not begin suddenly with

those complex animals of the Cambrian.

It started much, much earlier, first with simple microscopic forms

which eventually became bigger but which were still so soft

and delicate that they only very rarely left any mark in the rocks.

The question of the age of the earth posed another

problem for Darwin's theory.

In the 17th century, an Irish bishop had used the genealogies

recorded in the Bible that lead back to Adam to work out that the

week of creation must have taken place in the year 4004 BC.

That may seem to us to be a very naive way of doing things

but what other method was there anyway?

The Victorian geologists had already concluded that the

earth must be millions of years old.

But how many millions, no-one could say.

Then, less than 50 years after the publication

of The Origin, a discovery was made in what seemed a totally

disconnected branch of science that would ultimately provide the answer.

A Polish woman working in Paris, Marie Curie,

discovered that some rocks contained an element called uranium that

decays over time at a steady rate through a process called radiation.

Today, a century after she made her extraordinary

discovery, the method of dating by measuring

changes in radioactivity has become greatly refined.

This is a sample taken from those very ancient

rocks in Charnwood Forest...

..and these tiny crystals are revealed to be

562 million years old.

That provides more than enough time for natural selection to

produce the procession of fossils that eventually leads to the

living animals and plants we know today.

But there was another objection.

If all animals within a group have a common origin, how is it that

some kinds of animals are distributed throughout

the continents of the world except for Antarctica.

How is it that, for example, frogs in Europe and Africa are also found

in South America on the other side of the Atlantic Ocean, bearing in

mind that frogs have permeable skins and can't survive in sea water?

Darwin himself had a couple of suggestions.

One was that they might have floated across accidentally on rafts

of vegetation and the other is that maybe there were land

bridges between the continents,

but even he was not convinced by either explanation.

Even as late as 1947 when I was a geology student

here at Cambridge there was no convincing explanation.

It's true that back in 1912 a German geologist had suggested that at one

time in the very remote distant past all the continents of the earth that

we know today were grouped together to form one huge supercontinent

and that over time this broke up and the pieces drifted apart.

That would have provided an answer.

But when I asked the Professor of Geology here who was

lecturing to us why he didn't tell us about that in his lectures

he replied, rather loftily I must say,

"When you can demonstrate to me that there is a

"force on earth that can move the continents by a millimetre I

"will consider it but until then the idea is sheer moonshine, dear boy!"

But then in the 1960s it became possible to map

the sea floor in detail and it was discovered not only that the

continents have shifted, in just the way that the German geologist

had suggested but that they were still moving.

New rock wells up from deep below the earth's crust

and flows away on either side of the mid ocean ridges,

carrying the continents with it.

Amphibians had originally evolved on this super continent

and had then travelled on each of its various

fragments as they drifted apart.

Problem solved!

Perhaps the biggest problem of all for most people

was the argument put forward for the existence of God at the beginning

of the 19th century by an Anglican clergyman called William Paley.

He said supposing you were walking in the countryside

and you picked up something like this.

You would know from looking at it that it had been designed to

tell the time.

There must, therefore, be a designer

and the same argument would apply if you

looked at one of the intricate structures found in nature, such as

the human eye and the only designer of the human eye could be God.

Anti-evolutionists maintain that the eye would

only work if it was complete in all its details.

Darwin on the other hand argued that the eye had developed,

becoming increasingly complex over a long period of time.

That would only work if each stage of development was

an improvement on the previous one and today we know

enough about the animal kingdom to know that, that is indeed the case.

Some very simple animals have nothing more

than light-sensitive spots that enable them

to tell the difference between light and dark.

But if a patch of such spots formed even the shallowest of pits,

one edge of the pit would throw a shadow

and so reveal the direction of light.

If the pit got deeper and started to close,

then light would form a blurred image.

Mucus secreted by the cells would bend the light and focus it.

If this mucus hardened it would form a proper lens

and transmit a brighter and clearer image.

All these different fully functional stages at different

levels of complexity are found in living animals today.

This single-celled creature has one of those

light-sensitive spots.

Flatworms have a small pit containing light spots,

so they can detect the shadow of a predator.

A snail's blurry vision is good enough to enable

it to find its way to food, and the octopus

has an eye with a proper lens and can see as much detail as we can.

So the structure of the human eye does not demand

the assistance of a supernatural designer.

It can have evolved gradually with each stage bringing a real

advantage - as Darwin's theory demands.

Natural selection, of course, requires that an

animal's characteristics are handed from one generation to the next.

It's obvious that children resemble their parents.

Anyone knows that.

But when you come to think of it, how does that come about?

In Darwin's time nobody had the faintest

idea about the mechanism or the rules that governed that

process, except perhaps for one man who was

working in the city of Brno in what is now the Czech Republic

at exactly the same time that Darwin was writing his book in Kent.

That man's name was Gregor Mendel.

He discovered the laws of inheritance by breeding

thousands of pea plants

and observing how they changed from one generation to the next.

He found that while many characteristics were

passed down directly from one generation to another,

others could actually skip a generation.

How could that happen?

Mendel explained this by suggesting that each plant,

each organism, contained within it factors which were

responsible for creating those particular characteristics.

Today we call those things genes but nobody had any idea how

they worked until 100 years after Mendel's time

and then the answer was discovered in Cambridge.

In 1953, here in the Cavendish laboratories,

two young researchers, Francis Crick

and James Watson were building models like this.

It was their way of thinking about and investigating the structure

of a complex molecule that's found in the genes of all animals - DNA.

The crucial bit are these chains, which encircle the rod.

And here is a second and entwine. This is a double helix.

The workings of the DNA molecule are now understood in

such detail that we can demonstrate something that is truly astounding.

A gene taken from one animal can function in another.

The gene that causes a jellyfish to be luminous, for example,

transplanted into a mouse, will make that mouse luminous.

So, 150 years after the publication of Darwin's

revolutionary book, modern genetics has confirmed its fundamental

truth - all life is related and it enables us to construct with

confidence the complex tree that represents the history of life.

It began in the sea, some 3,000 million years ago.

Complex chemical molecules began to clump together to form

microscopic blobs.

Cells.

These were the seeds from which the tree of life developed.

They were able to split, replicating themselves as bacteria do

and as time passed they diversified into different groups.

Some remained attached to one another

so that they formed chains, we know them today as algae.

Others formed hollow balls which collapsed upon themselves

creating a body with an internal cavity.

They were the first multi-celled organisms -

sponges are their direct descendents.

As more variations appeared,

the tree of life grew and became more diverse.

Some organisms became more mobile

and developed a mouth that opened into a gut.

Others had bodies stiffened by an internal rod.

They, understandably, developed sense organs around their front end.

A related group had bodies that were

divided into segments with little projections on either side that

helped them to move around on the sea floor.

Some of these segmented creatures developed hard

protective skins which gave their bodies some rigidity.

So now the seas were filled with a great variety of animals.

And then around 450 million years ago, some of these

armoured creatures crawled up, out of the water and ventured onto land.

And here,

the tree of life branched into a multitude of different

species that exploited this new environment in all kinds of ways.

One group of them developed elongated flaps on their

backs which over many generations eventually developed into wings.

The insects had arrived.

Life moved into the air and diversified into myriad forms.

Meanwhile, back in the seas, those creatures with the stiffening

rod in their bodies had strengthened it by encasing it in bone.

A skull developed with a hinged jaw that could grab and hold on to prey.

They grew bigger

and developed fins, equipped with muscles that enabled them to swim

with speed and power so fish now dominated the waters of the world.

One group of them

developed the ability to gulp air from the water surface.

Their fleshy fins became weight-supporting legs

and 375 million years ago a few of these backbone creatures

followed the insects onto the land.

They were amphibians with wet skins and they had to return to water

to lay their eggs, but some of their descendents evolved dry, scaly skins

and broke their link with water by laying eggs with watertight shells.

These creatures, the reptiles, were the ancestors of today's

tortoises, snakes, lizards and crocodiles.

And, of course, they included the group that back

then, came to dominate the land - the dinosaurs.

But 65 million years ago a great disaster overtook the earth.

Whatever its cause,

a great proportion of animals were exterminated.

All the dinosaurs disappeared except for one

branch, whose scales had become modified into feathers.

They were the birds.

While they spread through the skies a small, seemingly

insignificant group of survivors began to

increase in numbers on the ground beneath.

These creatures differed from their competitors

in that their bodies were warm and insulated with coats of fur,

they were the first mammals.

With much of the land left vacant after the great catastrophe

they now had their chance.

Their warm insulated bodies enabled them

to be active at all times, at night as well as during the day

and in all places, from the Arctic to the tropics.

In water as well as on land.

On grassy plains and up in the trees.

There can be no doubt about our close relationship

to these chimpanzees.

Our bodies are so similar, the proportions of our limbs

or our faces may differ, but otherwise we are very, very similar.

The arrangement of our internal organs, the chemistry of our blood,

the way our bodies work, all these are almost identical

and DNA confirms that.

Indeed we are as closely related to chimpanzees

and the rest of the apes and monkeys as say lions are to tigers

and to the rest of the cat family.

Suddenly an image from our remote past comes vividly

to light at the time when our distant

ancestors, in order to keep up with the changing environment, had

to wade and keep their heads above water in order to find food.

That crucial moment when our far distant ancestors took a step

away from being apes and a step towards humanity.

The Natural History Museum is one of the most

important museums of its kind in the world.

Richard Owen brought it into existence,

but over a century later, discoveries from many

branches of science have shown that his belief that species can

never change but always remain exactly the same was mistaken.

It was Charles Darwin's profound insights that have

proved to be true.

And now, to mark the 200th anniversary of his birth,

his statue is being taken from its out-of-the-way location to be

placed centre stage in the main hall.

Darwin's great insight revolutionised

the way in which we see the world.

We now understand why there are so many different species,

why they are distributed in the way they are around the world

and why their bodies and our bodies are shaped in the way that they are.

Because we understand that bacteria evolve,

we can devise methods of dealing with the diseases they cause

and because we can disentangle the complex relationships between

animals and plants in a natural community we can foresee some

of the consequences when we start to interfere with those communities.

But above all Darwin has shown us that we are not

apart from the natural world - we do not have dominion over it.

We are subject to its laws and processes as are all other

animals on earth to which indeed we are related.

HE LAUGHS

He was an extraordinary person living there in Downe in Kent.

And yet communicating with naturalists

all over the world by post which took weeks

to meet different people and to produce

at the end this very beautifully written book.

The last paragraph of this book, you know,

is a great piece of literature.

It's a great piece of prose

and it contains a really profound truth

that's worth pondering. Should I read it?

"There is grandeur in this view of life, with its several powers,

"having been originally breathed by the Creator

"into a few forms or into one;

"and that, whilst this planet has gone cycling on according

"to the fixed law of gravity, from so simple a beginning endless forms

"most beautiful and most wonderful have been, and are being, evolved."