All language subtitles for Charles Darwin and the Tree of Life BBC David Attenborough 720p HDTV TR sub_Subtitles01.ENG

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 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.

HE CHUCKLES

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.

That explanation was believed,
literally,

by pretty well
the whole of Western Europe
for the best part of 2,000 years,

and generations of painters
pictured it for the faithful.

This version was painted in
Italy in the 16th century.

Here is God in the Garden of Eden,

which is now filled
with all kinds of animals.

Here he is pulling Adam
out of the Earth.

And here, creating the first
woman by putting Adam to sleep,

and then taking one of his ribs
and extracting Eve from his side.

She comes out,
assisted by two angels.

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 newcomer,

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,

and as usual,
when he went ashore to investigate,

described what he
found in his journal.

"My servant and self were landed
a few miles to the northeast,

"in order that I might examine
the district mentioned above

"as resembling chimneys."

Volcanic chimneys, presumably.

"The comparison
would have been more exact

"if I had said, 'the iron
furnaces near Wolverhampton.' "

HE CHUCKLES

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.

So 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 Pekingese
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 Down,

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 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 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 is 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 6th 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.

He, and other pioneer
Victorian geologists,

as they established
their comparatively new science,

recognised that the outlines of the
history of life could be deduced

by examining the land around them.

Look at these rocks
in northern Scotland.

We know from fossils that
are associated with them
that they are very ancient.

And they are sand stones.

Compacted sand that was laid
down at the bottom of the sea,

layer upon layer upon layer.

But look how many layers there are!

Clearly, those at the top
must have been laid down

after those beneath them.

So as you descend from layer to
layer, you are in effect
going back in time.

So a fossil species,
if it comes from a particular layer,

is of a particular age.

And if you can recognise each one,
then you can begin to piece together
the outlines of life's history.

Ah, Micraster...

The ability to identify fossils
and place them in their
geological time zone

was still an essential skill when I
was at university a century later.

We worked our way through drawers
like these,

which are full of fossils
of one sort or another -

but none of them
have labels, only numbers.

So you were expected
to be able to pick up one...

..and say,
"Yes, that's a belemnite."

Now, actually which belemnite
it is, I can't remember now.

And when you came to
your practical exam,

your examiners would produce
one of these and say,

"OK, what's that?"

And you either knew
or you didn't,

and the way you knew was because of
all the work you did in drawers
like these, hour after hour.

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 a 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 cayman 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 safekeeping.

It's called Charnia.

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

It has a central stem,
and 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 Ediacra 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 here
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 super-continent,

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.

The genetic code can
also reveal relationships.

Even our law courts accept
that DNA fingerprinting

can establish whether a man is
the father of a particular child.

And it can also reveal
whether one kind of animal
is related to another.

It proves, for example,
that kangaroos -

ground-living animals
that run with great leaps -

are closely related to koalas
that have taken to climbing trees.

That insect-eating shrews
have cousins that took to the air

in search of insects - bats.

And that one branch of the
elephant family,
way back in geological history,

took to the water
and became sea cows.

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 backboned 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.

HE CHUCKLES

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 -

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 CHUCKLES

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