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 ?00 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
For your Tree Of Life poster,
and to find out more about Charles Darwin
and Open University programmes on the BBC, call -
Or go to -
Subtitles by Red Bee Media Ltd
Email subtitling@bbc.co.uk
我们的地球是唯一已知有生命存在的行星，
地球上的生物数不胜数。
字幕翻译:黄河 QQ:1095678001
我够幸运， 几年来，
游历了地球上 最特别最偏远的地方
寻找并拍摄各种动物。
这是世界上最大的花。
蓝鲸！
这颗行星上最大型的动物。
动物和植物的绝对数和多样性是惊人的。
不同物种的数目估计有六百万到一亿。
没有人知道这里有多少不同的动物类型。
目光所及之处，都有生命存在。
物种常常是多样化的－
举例来说， 猴子就有将近200个不同的类型。
而蜂鸟有315种。
蝙蝠有将近一千种。
而甲虫... 至少有350,000种。
更别提开花植物有25万种了。
生物的多样性令人惊咤。
甚至在英国这一块小小的林地，
你也可能见到四或五个不同类型的雀类。
为什么生物的多样性如此令人眼花撩乱?
而200年前， 我们如何能够了解生活着的
种类如此繁多的生物？
一个将解释生命为何如此的惊人不同 的人诞生了。
他的出现，让我们 看世界的方式发生了革命
我们在这个世界所处的位置也发生了变革。
他的名字是查尔斯·达尔文。
片名 达尔文和生命之树
这本书，圣经，
解释了这令人惊奇的不同如何发生。
在创造世界之后第三天， 上帝创造了植物。
第五天，鱼和鸟，
然后第六天，哺乳动物，
而最后，人类。
整个西欧， 在2,000年的绝大部分时间里
对这一解释深信不疑，
而一代代的画家为信徒们描绘它。
16世纪意大利绘制的版本。
这是伊甸园里的上帝，
现在伊甸园充满了各种各样的动物。
看这里他正把亚当从地上拉起来。
这里...创造出第一个女人 先让亚当睡过去，
然后拿他的一根肋骨 从他身体一侧抽出夏娃。
两位天使协助她来到这个世界。
当上帝完成这些的时候， 他对亚当和夏娃说，
"要生养众多，使你们的后代遍满世界，控制大地，
"我要你们管理海里的鱼 和天上的飞鸟，
"还有地球之上会动的所有生物。"
按照圣经说的， 上帝吩咐得很清楚，
人类可以按他们的意愿 开发利用自然世界。
这种人类占优的观点 一直持续，直到1831 年,
一艘英国测量船， 小猎犬号，进行了一次环球航行。
在船上， 与船长随行的，
是22岁的查尔斯达尔文。
他们越过了大西洋 登陆巴西海岸。
在那里，热带大自然绝对的丰富 使新来者惊讶不已，
正如我在30年前， 循着达尔文的足迹所发现的那样，
当时是为了拍摄一系列关于 大自然多样性的电视节目。
达尔文，还是一个孩子，已经 是狂热的昆虫搜集家，
这里令他着迷， 几乎到了忘我地步。
一天中，在一片小小的地方，
他发现了 69种不同的甲虫。
正如他在日记中写的，
"这足以打破 昆虫学者思想的宁静
"在他们考虑一个完整目录将来的长度时。"
他们往南，绕过合恩角 到达了太平洋。
然后，在1835年九月,
在出航几乎四年后，
他们在鲜为人知的加拉巴哥岛上登陆。
在这里他们发现了 世界上其他地方所没有的物种。
丧失了飞行能力的鸬鹚。
游出海面的蜥蜴
在海底觅食。
达尔文，在剑桥大学学过植物学和 地质学，
收集动物和植物的样本，
像往常一样， 在他上岸调查的时候，
在他的日记中描述 他旅程中的发现。
"仆人和我在 东北几英里的地方登陆，
"以便我能调查 上面提到的
"象烟囱似的地方． "
照推测，是火山烟囱。
"如果要比喻得更恰当的话
"我该说:' 伍尔弗汉普顿附近的铁炉。'"
笑
加拉巴哥岛的英国居民
声称所他能根据大乌龟的龟壳形状
说出乌龟是哪个岛上的。
如果它壳的前端是圆的，
它就是来自一个水量丰富的岛， 以茂盛的地表植物为食。
壳前端有翘起的则来自较干旱的岛，
这使它能够得着比较高的植物。
这些在各独立岛屿上的乌龟， 是不同种的吗？
如果是的话，那每一个都是 神造物的单独行为吗？
达尔文注意到的
这些加拉巴哥岛动物中的不同点 当然，都很细微，
但是如果他们会进化，
难道不可能经过千百万年
一系列这样的改变积累成
一种革命性的改变？
在返航途中，达尔文 有时间深入思考这些事情。
物种会不会并非永恒不变， 可能，事实上，在慢慢地演变？
他一回来，就把他的样品 分门别类并发送给
有关的专家以便 进行识别和鉴定。
大部份的哺乳动物骨头和化石 送到理查欧恩手上。
欧恩是他那个时代 最才华横溢的动物学家。
他是第一个能辩认恐龙的人
甚至给它们起了不同的名，
他后来成为伦敦自然历史博物馆 的创建者和第一任主管。
许多达尔文收集的样品 仍然被保护并珍藏
跟七千万别的样品一起 收藏在欧恩建立的博物馆中。
这里其中之一。
这显然是某种大型动物的下颚， 当达尔文发现它的时候，
还有一些皮肤和毛发附在上面，
所以起先它被认为了 是某些未知的物种遗留的。
现在我们知道，它是种灭绝了约10,000年的， 生活在地面上的巨型树懒。
欧恩研究了它的大量细节
最后描述了它的样子并 给它起名叫磨齿兽(Mylodon Darwinii)，
以纪念它的发现者。
但二位伟大科学家间的互相尊重 没有持续多久。
航行回来后不久，达尔文在 肯特郡的Down House安了家
在这里他写下他的旅行过程
并埋头撰写关于南美洲的珊瑚、
甲壳类动物、地质和化石的 详细的科学论文。
但他也深深思忖 在加拉巴哥岛和其他地方之所见。
也许物种不是一成不变的。
每一天，他都在花园后面种下的
这片小树林中散步。
这是他开始思考自然历史的地方，
包括那奥秘中的奥秘－
物种如何演变。
他注意到， 多数动物，不是全部
会生下远远超过进行繁殖 所需数量的后代。
这只雌蓝山雀，以它为例， 很可能一年下十二颗蛋－
一辈子大概50颗左右。
然而它只需要两只小鸟存活就能
完成繁衍并维持蓝山雀数目。
存活的，当然， 通常是最健康的
而且最适应它们特别的环境。
然后他们的特性被遗传。
因此有这样的可能，在经过多代之后，
特别是如果环境发生变化之后， 物种很可能也跟着变化。
只有最适应的能幸存， 这才是重点。
他将这个过程称为 "物竞天择".
那能解释他记录下的 从加拉巴哥岛带回来的
雀类的相异性。
这些雀除了喙以外非常的相像。
这一只有用来捕捉昆虫的 细长的喙。
这一只，另一方面，
来自有许多坚果的环境，
有一个大而重的喙 使它能够弄碎坚果。
因此也许，
经过漫长的地质时间，
特别是当物种侵入新的环境，
那些变化确实将达到十分剧烈的程度。
达尔文在他的一本笔记里 画了一个草稿来说明他的想法，
解释一个祖先如何 衍生出几种不一样的后代，
然后在上面写下试探性的 "我认为".
接下来他必须证明他的理论，
他花了数年蒐集充足的、使人信服的证据。
他是一个非凡的写信者。
每天他给全世界的科学家和自然学家 写出上打的信。
他也意识到，
从人们首次开始驯养动物，
就已经为他做了数个世纪的实验。
所有的家犬都驯化自 同一个祖先物种－狼。
养狗人选择了那些刚好 有取悦他们的特质的幼崽来养。
自然界，当然，选择的是那些 最适应当地环境的幼小动物，
但这一过程在本质上是相同，
两种情况下都产生了惊人的多样性。
实际上， 大部份这些不同的品种
之所以会被认为是不同品种是因为它们不是， 实际上也不能够，跨品种杂交。
由于纯粹的机械原因， 京巴狗没办法跟大丹狗交配。
当然，如果你采用人工授精，
你确实能将几乎全部的 这些品种拿来杂交，
但是因为人类对所养的狗的选择
只有数世纪。
而自然界对动物的选择 进行了数百万年－
数千万年， 甚至数亿年，
因此当我们思考为何 物种现在如此不同时
这一过程早已经开始了。
达尔文，坐在Down House里， 写信给鸽子爱好者和养兔人，
询问关于他们的方法和结果 的各种详细问题。
他自己，成了一名乡村绅士 并经营一座庄园，
会饲养马、羊和牛。
他还领导对其温室里的植物 进行的仔细实验。
但达尔文知道 物种出现并没有神的介入
的观点是惊世骇俗的，
也违背他的妻子--艾玛的信仰
她是一个虔诚的基督徒。
也许因为这一点， 他非常注重工作的科学性。
他在公众面前强调 他的宗教信念不会被引诱，
但是在他晚年， 他从加入教会中撤退。
星期天，他会护送艾玛 和孩子到这里教区的教堂，
但是当他们进去礼拜时，
他留在外面 到乡间小路散步。
也许是因为他担心， 他的理论会导致某些方面的愤怒，
他把出版日期推迟 年复一年。
但是他写下一篇长长的摘要，
然后在1844年7月5日, 他给妻子写了这封信。
"我的亲爱艾玛。
”我刚刚完成了 我的物种理论的草稿"
一些草稿－长达240页。
"我写下这些是因为 万一我突然离开人世，
"我希望你会致力于它的出版。"
接下来他列出 他的各个博物学家朋友
那些被要求编辑和检查它的人，
他情意绵绵的结尾，
"我的亲爱妻子...
"你的挚爱，CR 达尔文."
往后的14年里 他继续累积证据并提炼他的理论。
但是后来形势突变。
1858年6月，在他 从加拉巴哥岛回来22年后，
在他搞研究的Down这个地方， 他收到了一个包裹
来自一个在现在的印尼工作的博物学家。
名叫艾佛烈·罗素·华莱士。
他和达尔文已经通信了几年。
但这个包裹不同。
里面有一篇随笔 罗列出和达尔文完全相同的观点...
关于自然淘汰的进化。
这些观点是当华莱士躺在他的小屋， 因患疟疾的发烧成半精神错乱时在脑中产生的。
但是虽然他的关于自然淘汰的 观点与达尔文一样，
但他却没有花20年收集如山的证据 来支持它，而达尔文做了。
那这个理论算谁的？
最后，林奈协会的资深成员们决定 最公平办法是
在伦敦的柏林顿馆里召开的 一次协会会议上，
将两人理论的简短大纲 逐一进行宣读。
林奈，从此成为，
研究自然世界的科学家们 定期举行会议
展现和讨论有关 他们观察和想法的文件的场所。
1858 年7月1日的那次会议 参加者只有大约30人。
两位作者都没出席。
华莱士在10000英里之外 东印度群岛上，
而达尔文病了 被不久前他儿子的夭折所摧垮，
所以呆在肯特郡的家里。
因此，这两份文件 只好由大会秘书宣读，
而我们所知道的是，当时它们 几乎没给什么人留下一点点印象。
第二年达尔文将他的理论 详细的写了出来。
然后他把手稿送至 他的出版人，约翰默里，
其公司－从那里起到现在－ 一直有办公室在Albemarle大街， 就在皮卡迪利大街旁边。
默里是那时的大出版商
出版过珍奥斯汀和拜伦公爵的作品，
首印版还陈列在这些办公室墙上。
达尔文认为他的作品 只是简单的一个摘要，
即便如此，它仍有400页。
1859 年11月24日出版.
这不是首印版，太遗憾了。
首印版现在价值数十万英磅。
这是第6版－我的，
当18岁的时候，我才注意到， 我买它的时候还是个孩子。
它花了我好多钱...一个先令。
第一版的1,250本很快售罄，
然后就再版。
然后再版又再版。
它是一本很少技术术语的书－ 任何人都容易读懂。
象所预测的， 它引发了愤怒，
不只在这个国家各处， 实际上是整个文明世界。
最令人愤慨的， 看起来，是其中所隐喻的
人类并非 象创世记一书所宣称的那样，
由上帝所特别创造出来，
而是类人猿祖先的后裔－
一个为漫画家们提供了 广阔发挥空间的观点。
教会的领袖， 由牛津城的主教塞缪尔威尔伯福斯带领，
攻击它的理由是 它贬低了上帝的地位
并与圣经所说的创世界故事相矛盾。
"达尔文先生脱离了大自然创造的 这条宽广大路
"进入了幻想和假设的丛林， 其恶不小"
"我读你的书痛苦多于快乐..."
"简直是疯狂吸入有毒气体。"
"完完全全的失败。"
达尔文的理论暗示了 生命起始于简单的形式，
然后变得越来越复杂。
他很清楚整个进化的理论 会引发许多疑问。
事实上，其中一些疑问 直到最近才得到答案。
但是在他那个时代， 许多卓著的科学家
提出的问题似乎是 无法克服的困难。
最早是理查欧文，
20年前曾为灭绝的磨齿兽命名 以纪念达尔文。
几年来，这两个人 深深嫌恶对方
并时常争辩。
不是说欧文认为 伊甸园的故事完全正确，
但尽管如此， 他还是一个宗教色彩浓厚的人。
毕竟，他要确保他的博物馆， 要展示出造物的神奇，
与它中古欧洲式大基督教堂 的设计相呼应。
欧恩知道生命的多样性。
毕竟，他花费了整个职业生涯 来进行编目。
但即便如此，他拒绝相信 物种会随时间演化。
他，和另一位 维多利亚女王时代的地质学先驱，
当他们建立其相对新的科学时，
认识到生命史的大致情形
可借助研究身边的土地进行推断。
看这些北苏格兰的岩石。
从它们所带的化石我们可以 知道其年代非常古老。
而且他们是沙石。
密密实实的沙子 堆叠在海底，
一层又一层。
看看这里有多少层！
很显然，顶上的 一定比下面的那些
要晚一些落到海底。
因此你一层一层这么下来， 实际上你就在追溯时间。
因此一个物种化石， 如果它来自特定的某一层，
它就是某一特定年代的东西。
如果你认出每一个， 你就能拼出生命史的大致轮廓。
啊，小蛸枕属...
识别化石并将其放到对应 地质时间段的能力
仍然是一个必要的技能， 即使是一个世纪之后我读大学时。
我们通过这样的抽屉来区分，
装满了这种或那种化石－
但是它们都没有标签，只有数字。
所以你会希望能拿起其中一块...
...然后说， "哦，是块乌贼类化石。 "
现在，它具体是哪种乌贼类化石， 我现在也不记得了。
当你参加实际考试时，
主考者会拿出一块问你，
"好，这是什么? "
你要么就懂要就不懂，
你能看懂要靠你在这些抽屉上 所花的工夫，日积月累。
欧恩没有否认这些不同物种 出现的顺序。
但是他相信每一种都是 独立的，由神逐一创造的。
不管怎样，达尔文的理论需要 不仅仅在相似的物种之间，
还要在庞大的动物群体之间找到联系。
如果鱼类、爬虫动物、鸟类 和哺乳动物都是由别的物种进化而来，
就必定会有中间形式 介于这些庞大的群体之间。
只是没有找不到。
接着， 《物种起源》出版仅两年后，
理查欧文为他的博物馆购买了 最令人惊异的化石。
它在巴伐利亚这个 石灰石采矿场被挖出。
这里的石头成 平整、光滑的片状
自从罗马时期起就被用作屋面瓦。
大部分是空的。
但偶尔， 当你将它们分开时，
会露出一只虾或一条鱼。
你几乎无法抵抗这种诱惑
要把你看到的所有石块弄出来，
然后将它象一本书一样打开， 查看尚未打开的每一页
看是不是也许还夹有另一块化石。
而这一块化石是前所未有的。
它现在仍然是自然历史博物馆中 最宝贵的藏品之一。
这就是它－ 叫做始祖鸟。
在它翅膀上有明显的羽毛
尾巴也有。
因此说它是一只鸟欧文会毫不犹豫。
但是跟人们所知的任何一种鸟都不一样，
因为在它的翅膀前端有爪，
并且，后来发现， 它没有喙却有颌骨，上面还长着牙齿。
有一排的骨头支撑它的尾部。
因此它一部份是爬虫动物，一部分是鸟类。
这正是两个大物种群之间的联系
终于浮出水面。
天哪，你真的能看到 那里的羽毛纤维。
同一生物的其他样本 更清楚地显现出它的羽毛。
我们从始祖鸟的骨头知道， 充其量，它只是一只勉强的飞行者。
因此最后它被更现代，
更有效率的鸟所取代， 并不令人惊讶。
这些过渡物种的命运就是如此。
最终他们灭绝了，
我们只有从它们的化石的遗迹 才能知道它们曾经存在。
即便如此，也有生活在今天的鸟
能作为例子说明 现代鸟和爬虫类动物之间的联系。
何爱青鸟(麝雉)在南美洲的 热带沼泽筑巢。
水下有鳄鱼，随时准备 要吃掉可能从它的巢掉下的小鸟，
因此抓紧能力非常有价值。
刚孵出的雏鸟有种有趣方式来抓紧。
小家伙们的翅尖仍然有爪在， 就象始祖鸟一样。
这是鸟的翅膀其实是进化的前肢 的生动证据
一度曾是长有脚趾的爪子。
还有一种现存生物表现为 不同物种的结合，
一组爬行动物的后裔 采取了不一样的进化过程
进化出来的不是羽毛，而是毛皮－
鸭嘴兽。
当这种生物的样品 在18世纪末
第一次从澳洲来到欧洲，
人们拒绝相信他们的眼睛。
他们说这是恶作剧－
几种不同的动物拼凑起来的。
而在一定程度上 那些早期怀疑论者是正确的。
鸭嘴兽是最特别的 不同动物的混合。
它部份是哺乳动物而部份是爬行动物。
因此它能给我们对 最早的哺乳动物如何进化提供一些思路。
当它繁殖的时候， 它做的事与所有其他哺乳动物不同。
在它的巢中， 洞穴深处，它生蛋。
这点是鸭嘴兽与爬行动物的联系，
而这使它被视做
最原始的现存哺乳动物。
所以庞大动物群体间的链接
事实上，并未失踪，
而是在化石和活生物两者中都有。
虽然化石的记录 给消失的链接
提供了答案， 它也造成一个重大问题。
事发非常突然。
达尔文时期最早的已知化石
来自一种地岩层 叫寒武纪，
有二个主要的类型－
这些，看起来像线锯片的 叫做笔石，
而这些，像巨大的木虱的 叫做三叶虫，
地球上的生命真的始于
象这些一样复杂的生物吗？
小时候，我是一名 热心的化石搜集家。
我在莱斯特市长大，
我知道在离城市不很远， 这个叫做查恩坞森林的地方，
有世界上最古老的岩石， 年代比寒武纪还久远。
因此，根据定义， 它们不会有化石。
我没有理由在这些 远古岩石中寻找化石。
可是有，真的， 极少数，
在这些岩石中，形状相当古怪
象这里这一块。
但是它们被当成机械象差忽视掉了。
我的意思是，毕竟，
在这些极端远古的岩石中 怎么可能有什么生物？
然后在1957年,
一个比我有更多的耐性 和敏锐的男学生
发现一些着实不平凡的东西－
不可否认地，生物的遗迹。
它在这里 莱斯特博物馆里面，
被拿来这里保管。
它叫做Charnia.
谁会怀疑这是活生物的印痕？
它有一根中央梗， 两面有分支。
事实上，这东西看起来 象是今天长在
珊瑚暗礁上的海鳃。
自从它被发现， 这种极端年龄的岩石里
整个系列的生物找到了，
不只在这的查恩坞森林， 还包括世界上很多不同地方。
化石搜寻者在澳洲的 Ediacra山寻找这些岩石
也发现了别的奇怪的形状。
起先，许多科学家拒绝相信
这些模糊的痕迹是水母的遗迹。
但如今，已发现的足够样品 使人完全确信
它们的确就是。
所以现在我们知道生命并非 由寒武纪那些复杂的动物突然开始。
它在更早更早时候就开始了，
一开始是简单的微生物 逐渐逐渐变大，
但仍然如此柔软脆弱 罕有在岩石中留下任何标志。
地球年龄的疑问给达尔文的理论 造成另一个新问题。
在17世纪，一个爱尔兰的主教 根据圣经里记录的系谱
回溯到亚当并计算出 创世纪的那个星期
肯定是在西元前4004年。
这么做在我们看来是一种 很天真的做事方式，
但无论如何有其他的方法吗？
维多利亚时代的地质学家已经 有结论说地球寿命有数百万年。
但到底是几百万， 没有人说得清。
然后，在《物种起源》出版 之后不到50年，
有了一项发现 使一门似乎完全无关联的分支科学
能最后给出答案。
一个在巴黎的波兰女人， 玛莉居里，
发现一些岩石包含 一种元素叫铀
会通过一种叫放射性衰变的过程 随着时间推移按稳定的比例衰变。
今天， 在她特别的发现一世纪之后，
借测量放射性的变化
推断年代的方法 已经变得非常精密。
这是从Charnwood 森林那些 非常远古的岩石拿的一个样品 。
这些小水晶显示的年龄 是五亿六千二百万岁。
这个时间绰绰有余
足以那些的化石队伍通过自然选择
逐渐演化为今天我们所知活着的动植物。
但是有另一个反对意见。
如果一组里面所有的动物 都有一个共同的起源，
有几个类型的动物是如何
被分配到全世界各大陆的， 除了南极洲没有以外？
怎么做到，举例来说， 欧洲和非洲有青蛙
南美洲也有，
在大西洋另一面，
别忘记青蛙有浸透性的皮肤 不能在海水中存活？
达尔文自己有一些提议。
其中之一是他们可能 偶然以植物为筏飘浮过海，
另一种可能是 也许大陆之间曾有陆桥，
但是连他自己也不能 信服其中任何一种解释。
甚至直至1947年, 当我 成了一名剑桥的地质学学生，
还没有使人信服的解释。
倒真有这么一回事， 在1912年一个德国地质学家
提出在非常遥远古代某个时候，
我们今天所知的地球所有大陆 是聚在一起的
构成一片巨大的超级大陆，
而随着时间的过去， 各大陆板块漂流瓦解。
那应该能提供一个答案。
但是当我问这里正在 对我们演讲的地质学教授
他为什么没有在他的演讲中 告诉我们这些东西的时候，
他回答，我必须讲 他是相当傲慢地答道，
"当你能向我示范地球上有哪一个力量 能将大陆移动一毫米的时候，
"我会考虑它，但是那之前， 这种想法纯属空谈，亲爱的孩子!"
但是然后，在1960年代，
详细地描绘海床成为了可能，
并发现大陆不仅仅如同
德国地质学家所说的发生了漂移，
而且它们仍然在漂移着。
新的岩石从地壳下面深处涌出，
携带着大陆板块， 从中央海脊往两边流动。
两栖动物在这块超级大陆上 进行了初级演化
然后当各个不同板块漂移时 跟着板块旅行。
问题解决!
也许对大部分人来说最大的问题是
对上帝存在的争论
在19世纪初由一名圣公会牧师 叫威廉佩利的人提出。
他说，假设你正走在乡间 捡起象这样一个东西。
你能从察看它知道
它被设计好了可以显示时间。
因此，必定存在一个设计者。
同样的争论也支持这一点 如果你看一下自然界里的一个复杂结构，
比如人类的眼睛。
人类眼睛唯一可能的设计者是上帝。
反进化论者坚持 眼睛只会在它所有的细节
完备之后才能工作。
另一方面，达尔文主张， 经过漫长时间，
眼睛进化了，逐渐变复杂。
这意味着进化的每个阶段
都要比原先的更进步，
而今天我们对动物王国有充分的了解 知道的确是这么一种情形。
一些非常简单的动物 除了一些感光点来辨认
亮和暗的区别之外 什么也没有。
但是如果一片这样的点形成 甚至最浅的凹陷，
凹陷的一个边缘会投下一个影子，
因此显示光的方向。
如果凹陷变深并开始封闭， 那么光就会形成一个模糊的像。
细胞分泌的粘液 会使光弯曲并会聚。
如果黏液变硬， 会形成一个适当的透镜
并传送一个更明亮更清楚的图像。
所有这些复杂程度不一的
不相同的功能完善阶段 都可以在今天生活的动物中被发现。
这个单细胞生物有 一个那种感光点。
扁形虫有一个小凹陷 含有感光点，
因此他们能发觉 掠食者的影像。
蜗牛的模糊视觉 够让它找到往食物的路。
而章鱼有一只含适当透镜的眼睛 且看到的细节不亚于我们。
因此人类眼睛的结构 不需要超自然设计者的协助。
它能逐渐地进化，
每个阶段带来一次真正的进步， 如达尔文理论所说。
自然淘汰，当然，
需要动物的特性 被一代代传承。
很明显孩子长得象父母。
任何人都知道。
但是当你开始思考它时， 这是如何发生的？
在达尔文时代， 对控制这一个进程的机制或规则
根本无人知晓，
可能除了在现在捷克Brno市的一个人，
达尔文在肯特郡写书的同一时间。
此人名叫雷戈·孟德尔。
他发现了遗传法则
靠的是种植数千株豌豆
并观察他们如何一代一代的改变。
他发现当许多性状
直接从一代传至下一代的同时，
另外一些性状会隔代相传。怎么会这样呢？
孟德尔的解释是 每株植物，每个生物，
都含有负责产生
那些特定性状的因素。
今天，我们称之为基因，
但是直到孟德尔时代100 年后 仍没有人知道基因如何工作。
答案在剑桥揭晓。
1953年, 在卡文迪许实验室这里， 两个年轻的研究员，
法兰西斯克力克和詹姆士沃森， 正在建立这样一个模型。
他们用它来思考和调查
在所有动物基因中被发现的 复杂分子－DNA的结构。
关键点是这些链，
围绕着这些杆－
这是第二个－缠绕着。
它是一个双螺旋。
DNA分子的工作原理 现在被了解得如此详细
以致我们能示范 一些真正令人惊骇的事情。
从一种动物取出的基因 能作用于另一种动物。
引起水母发光的基因，以它为例，
移植给老鼠， 会让老鼠发光。
遗传密码还能揭示血缘关系。
我们的法庭甚至接受 DNA指纹
能确定一个男人是不是 某个孩子的父亲。
它也能揭示某一类动物 是否是另一种动物的后裔。
它证明，举例来说， 袋鼠－
生活在地面的 大步跳跃奔跑的动物－
跟会爬树的树袋熊是近亲。
食虫目树鼩的表亲 则是在空中飞来飞去
抓虫子的－蝙蝠。
大象家族的一个分支， 在地质学历史中往回，
则在水里变成了海牛。
因此，在达尔文的革命性著作 出版150年后，
现代遗传学已经确认 它的基本事实－
所有的生命都有关联。
它使我们有信心能够构造
展现生命历史的错综复杂之树。
从海洋中开始，
大约在三百万年前。
复杂的化学分子开始成丛聚集
形成微生物块－细胞。
这些是生命之树发展的种子。
他们能够分裂，复制自己 象细菌一样
随着时间推移，他们 演化为不同的种群。
有一些继续附到另外一些上面， 所以他们形成了链。
即我们今天所知的藻类。
其他那些自身塌陷形成了空心球体，
产生一个内空的躯体。
它们是最早的多细胞生物－
海绵是它们的后代。
当越来越多的变化出现， 生命之树成长并变得更多样化。
一些生物变得更好动 进化出嘴巴--连通到内脏。
其他有的身体由内部的杆加强。
他们可理解地 在身体前端进化出感觉器官。
一个种族有一节节的身体
两边都有小小的突出部分 帮助他们在海底四处游动。
其中的一些节肢动物 进化出硬的保护性皮肤
给予他们身体一定硬度。
因此现在海洋充满了丰富多样的动物。
然后， 约四亿五千万年前，
这些甲壳动物中的一些爬出水面， 冒险上到陆地。
在这里，生命之树 分支出浩如烟海的不同种群
用尽所有方式开发这一新环境。
它们中的一族 进化出背部延长的片状垂悬，
这些，经过许多世代， 最终进化为翅膀。
昆虫出现了。
生命进入空中多元化成多种形式。
同时，回到海洋里，
那些有杆加强躯体的生物 用骨头进一步强化。
演化出头盖骨，带着一个铰接的颌 能抓住食物。
他们长得更大， 并进化出鳍
肌肉使他们能够获得 游泳的速度和力量。
所以鱼现在统治了 这个世界的水域。
其中一个族群进化出了 能在水面上呼吸空气的能力。
他们的鳍变成了支撑重量的腿 在三亿七千五百万年前，
少数这些脊椎动物 追逐昆虫上到了陆地。
它们是有湿润皮肤的两栖动物 必须回到水里产卵，
但是它们的一些后裔 进化出干燥有鳞的皮肤
并藉由产下水密性蛋壳的卵 切断了与水的联系。
这些爬行动物是今天的 龟、蛇、蜥蜴和鳄鱼的祖先。
当然还包括了后来 统治陆地的种群－恐龙。
但六千五百万年前， 一场大灾难光临地球。
不管因何而起， 大量动物灭绝了。
所有的恐龙都灭绝了， 除了一个分支以外
它们的鳞变改造成羽毛。
它们就是鸟类。
当它们遍布天空，
一群小小的，看似无足轻重的生还者 令下方地面上的生物数量开始增长。
这些生物与竞争者不同的是
它们是暖血的， 还包裹着毛皮的外套－
它们是最早的哺乳动物。
大灾难之后留下空旷的陆地， 它们获得了机会。
它们温暖有保温能力的身体 使它们在晚上
也能有和白天一样的活动能力。
在所有地方， 从北极圈到回归线。
水中和陆地上。
草原上和树上。
毫无疑问 我们和黑猩猩是近亲。
我们的身体如此相似，
我们四肢的比例 或脸可能不同，
但是其他的 都非常、非常相似。
内脏的排列， 血液的化学成分，
身体工作的原理... 所有这些几乎都一样。
而且DNA确认了这一点。
确实，我们跟黑猩猩和
其他的猿和猴子的关系 正如，嗯，狮子和老虎
和其它猫科动物的关系般紧密。
突然，一个我们遥远过去的图像 逼真的闪现－
当时我们的远祖，
为了适应环境变迁，
必须抬高脑袋涉水
以找寻食物。
那是一个决定性的时刻 当我们的远祖
走出从猿猴迈向人类的一步。
这所自然历史博物馆 是世界同类博物馆中最重要之一。
理查欧文让它的存在成为了现实， 但一个多世纪之后，
许多科学部门的发现显示 他认为物种不变
永恒如初的信条是错误的。
是查尔斯达尔文深刻的洞察力 证明了进化的真实性。
现在，为纪念他200年诞辰，
他的雕像正被偏僻的位置
放置到主厅中央的台阶。
达尔文伟大的洞察力 解放了人们看世界方式。
我们现在明白了为什么 物种如此丰富多样，
为什么它们象这样分布 全世界各地。
以及为什么它们和我们的身体 会形成现在这样子。
因为我们了解细菌演变，
我们能想办法对付 它们导致的疾病。
因为我们能解开 自然社会中
动物和植物之间的复杂关系，
当我们开始干涉大自然的时候 我们能预见部分的结果。
但最重要的，达尔文让我们看到 我们并不独立与自然世界。
我们不能主宰它。
我们服从于它的法则和进程，
象地球上所有其他动物－ 跟我们实际上都有关联...一样。
(完)