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  • This series is about perhaps the most powerful idea

  • ever to occur to a human mind.

  • The idea is evolution by natural selection.

  • And the genius who thought of it was Charles Darwin.

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

  • throughout my whole career.

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

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

  • What Darwin achieved was nothing less than a complete explanation

  • of the complexity and diversity of all life.

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

  • In this series, I want to persuade you

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

  • than any religious story.

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

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

  • of our world.

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

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

  • and why it matters.

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

  • that evolution is a fact, backed by undeniable evidence.

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

  • which, Darwin realised, drives evolution on...

  • ..natural selection.

  • When Charles Darwin was born 200 years ago,

  • sailors and explorers were sending home

  • a dizzying array of specimens like these

  • from all parts of Britain's growing empire.

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

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

  • At school in Shrewsbury,

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

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

  • Today, thanks to Darwin, we know differently.

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

  • prefer to cling to the old ideas

  • and believe that God created our world

  • and every living creature in it.

  • I think it's scandalous

  • how little our children are taught about evolution at school.

  • A typical class gets just a few hours

  • to study one of the most important ideas in science.

  • This lot got me.

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

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

  • Why do we need to find out about evolution?

  • Why do we need to find out about evolution?

  • Because it is the explanation for our existence and because

  • it explains such a huge number of facts,

  • because everything we know about life is explained by it.

  • I believe in my religion

  • so whenever I read about evolution,

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

  • I just, like, believe my religion.

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

  • and any new book that says anything different,

  • you don't read it?

  • Even if you've got evidence,

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

  • which is the Holy Book, so...

  • So, the reason you believe it

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

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

  • 'for a lifetime of religious indoctrination.'

  • I was brought up to believe it.

  • Is that a good reason to believe something?

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

  • Yeah, and it says it in the Bible.

  • Yes, but in the Hindu sacred scriptures,

  • it says something different, doesn't it?

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

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

  • even though they contradict each other?

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

  • you can be made to believe something in religious studies,

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

  • You can't just say that...

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

  • and I would hate anybody to think

  • I was trying to make anybody believe anything.

  • I'm asking you to look at the evidence.

  • Perhaps you haven't got a full impression

  • of how strong the evidence actually is.

  • Nobody has seen evolution take place over a long period,

  • but they've seen the after effects,

  • and the after effects are massively supported.

  • It's like a case in a court of law

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

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

  • which no reasonable person could possibly dispute.

  • That's sort of the way it is.

  • 'There's only one thing for it -

  • 'I'm going to show them evidence -

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

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

  • 'When Charles Darwin was a teenager,

  • 'he would have been as much of a creationist

  • 'as some of these children.'

  • Darwin was born into a prosperous Shropshire family in 1809.

  • His father was a doctor,

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

  • But the adolescent Charles,

  • more interested in shooting and fishing than academic prowess,

  • was contemplating an easy life as a country parson.

  • Luckily for him, and for us,

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

  • In 1831, as a young man of 22,

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

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

  • Over five years, Darwin collected hundreds and hundreds of specimens

  • to send back to the collections.

  • But increasingly,

  • he wasn't satisfied with just recording

  • the animals and plants he saw.

  • He was beginning to have doubts about the Biblical story

  • of how animals were created.

  • While ashore, riding across the South American flatlands,

  • Darwin amused himself

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

  • But he was puzzled.

  • Why had God bothered to create

  • two very similar but slightly different types of rhea?

  • Had an original group of rhea split in two,

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

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

  • on islands.

  • I was lucky enough to retread Darwin's footsteps

  • on the Galapagos Islands last year.

  • Here, he began to wonder

  • why God would have created distinctive kinds of tortoise,

  • finch or iguana on more or less identical small islands.

  • Were iguanas like these related rather than separately created?

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

  • This pattern of relationships

  • became even more intriguing when Darwin encountered fossils.

  • The evidence of fossils

  • would help Darwin develop a theory of life on Earth

  • far more wonderful and more moving

  • than any religious story of creation.

  • This team of American scientists

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

  • Today, I'm joining the dig

  • because it was fossils like these

  • that made a huge impression on the young Charles Darwin

  • during his voyage on HMS Beagle.

  • To Darwin, they looked like ancient, giant versions

  • of animals he saw around him.

  • (MAN) The ground sloths flourished

  • for millions of years, and were quite successful.

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

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

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

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

  • the fossils closely resembled in every other detail

  • the skeletons of modern sloths living nearby.

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

  • peculiar features that they share with modern armadillos,

  • modern tree sloths and modern anteaters.

  • We can infer that they are related to these animals.

  • (DAWKINS) The discovery of fossils was a huge challenge

  • to the religious orthodoxy of Darwin's youth.

  • What were these animals? When had they lived?

  • And why didn't they exist any more?

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

  • Others claimed

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

  • But Darwin was one of the first scientists

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

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

  • than the Bible led us to believe.

  • And how had he realised this?

  • Through a fascination with geology.

  • During the voyage of the Beagle,

  • Darwin had had time to immerse himself

  • in the pioneering work of Charles Lyell.

  • Lyell argued that the landscape we saw around us was formed

  • by the slow action of vast forces, not thousands,

  • but millions of years of gradual change.

  • So, if the Earth was shaped and reshaped

  • over an immense period of time,

  • was there room, Darwin began to wonder,

  • for life to undergo slow changes as well?

  • You know how old these rocks are?

  • They're about 200 million years old.

  • Back in the 19th century, lots and lots of people

  • came here to look for fossils.

  • And some of the most famous fossils have been found here.

  • 'I'm taking the science class I met earlier to the beach.

  • 'Many of these teenagers have been brought up

  • 'to mistrust the idea of evolution.

  • 'I'm hoping they'll find a small fragment of the kind of evidence

  • 'that made Charles Darwin think again.'

  • Do you know what our ancestors were like 200 million years ago?

  • - They weren't... - They were around,

  • they wouldn't have been here

  • because this would have been the bottom of the sea.

  • They would have been kind of like shrews, little whiskery, twitchy...

  • It seems to be like a dream, but it's real.

  • Yeah, yes, it does, doesn't it?

  • This is all sedimentary rock,

  • meaning it's laid down at the bottom of the sea, mud coming down,

  • layer after layer after layer - that's what fossils are.

  • 'On a beach like this,

  • 'the pounding sea gradually exposes different layers of rock

  • 'and within them, hidden treasure -

  • 'a history of past life on Earth.

  • 'So, each layer you go down to,

  • 'you find a completely different set of animals.'

  • And if you look at the animals that you find, and plants,

  • over the great span of time,

  • you find that they form a kind of ordered sequence,

  • you find fish,

  • 400 million years ago, but you find no mammals at all

  • 400 million years ago.

  • The fish gradually changed into amphibians, changed into reptiles,

  • reptiles changed into birds, changed into mammals.

  • Did you find that?

  • - Yes. - Oh, that's terrific.

  • That's really great. Yeah.

  • That's a beautiful ammonite.

  • That's really beautiful. Well done for finding that. That's wonderful.

  • 'The fossil hunt has been a success.

  • 'Like Darwin, these teenagers have been brought face to face

  • 'with some tangible remnants of evolution.'

  • The evidence Darwin had seen with his own eyes on the voyage of the Beagle

  • seeded huge heretical questions in his mind.

  • And once he started thinking, he couldn't stop.

  • Darwin, once an easily distracted student,

  • returned from the voyage of the Beagle

  • a determined, even obsessive research scientist.

  • The trip had changed him and it was soon to change the world forever.

  • Back in London in the late 1830s, the specimens he'd collected

  • and his reporting of the voyage made Darwin a scientific celebrity.

  • Even more importantly, while cataloguing his finds,

  • Darwin realised that life forms weren't fixed.

  • They had changed over time.

  • They must have evolved.

  • Now, he wanted to pull together all the evidence

  • to understand how and why this had happened.

  • It took Darwin 20 years of research, on and off, to develop the ideas

  • that would eventually be set out in The Origin Of Species.

  • He wanted to be fully certain of his facts.

  • BIRDS TWITTER

  • The hard graft was done here at Darwin's home,

  • Down House in Kent.

  • Long before the days of the internet, of course,

  • Darwin drew upon the collective knowledge

  • of an entire generation of naturalists all over the world.

  • He sent out thousands of letters asking for data,

  • posing questions, trying out theories.

  • And back the letters flowed

  • from all around the world into Down House, a river of information.

  • Darwin studied the detail of how different mammals

  • share remarkably similar skeletons.

  • Their limbs have the same bones in the same order,

  • just reshaped and resized to suit different ways of life.

  • He was drawn to the similarity of early embryo development

  • in very different types of animals -

  • fish, birds, reptiles.

  • Increasingly, he became convinced

  • that every living thing must be related to every other.

  • Darwin began to see the history of life as a vast family tree.

  • Life began millions of years ago at the base of the tree,

  • and as time went by, our ancestors evolved,

  • split off and multiplied along branches

  • until now, every species on the planet

  • is a twig at the end of a branch -

  • all are related, all cousins.

  • Life had evolved from single cells into complex sophisticated beings.

  • It may seem like a huge leap,

  • but Darwin realised it had been achieved by small steps

  • over a vast span of time.

  • He grasped the immense age of the Earth.

  • Darwin believed the world was hundreds of millions of years old.

  • Today, we know it's over four billion years old,

  • and the life we can actually see around us

  • has existed for an insignificant blink of that time.

  • Darwin's wife Emma used to play to him on the piano

  • in this very room,

  • and Darwin would lie on the sofa and listen.

  • It's not clear how much he got out of it, though,

  • because it was once said of him

  • he was so tone deaf that people had to nudge him to stand up

  • when they were playing God Save The Queen.

  • I want to use this piano

  • to illustrate the vastness of geological time,

  • and yet how comparatively little of it

  • is occupied by those animals and plants that we know anything about.

  • If we have the origin of life at the bottom of the piano there,

  • and recent times at the top,

  • I find it astonishing

  • that we have nothing but bacteria all the way up here,

  • past middle C,

  • way up to about here,

  • when more complicated cells than bacteria first evolve.

  • And then we get the first mini-celled animals,

  • the first large animals somewhere here,

  • fish start around here,

  • the dinosaurs don't come in until about here,

  • and then, the extinction of the dinosaurs around here.

  • About here, the apes and monkeys,

  • and the whole of human history

  • would occupy a space less than the width of one piano STRING

  • right at the top of the keyboard.

  • Life had evolved over time.

  • But how had this happened? Why hadn't creatures stayed the same?

  • WINGS FLAP, PIGEONS COO

  • Darwin wasn't just an abstract theorist,

  • he like to get his hands dirty,

  • testing his ideas,

  • and in the 1850s, he became fascinated by pigeons,

  • by how man had remoulded the wild rock dove

  • into a rich variety of forms.

  • Darwin's bird specimens are now stored

  • at the Natural History Museum at Tring.

  • It's a very weird feeling,

  • these are actually Darwin's own specimens.

  • I see from Darwin's own label here that this is a blue owl pigeon.

  • Tumblers are characterised by this curious tumbling behaviour

  • that they show, sort of falling through the sky.

  • This one has been relabelled, it is a Darwin specimen.

  • This one actually has Darwin's original label here.

  • Darwin realised that, for centuries, through small steps, pigeon breeders

  • had been in the business of evolution.

  • Here was life in constant flux.

  • One of the big things Darwin had to fight against

  • was the feeling that people had

  • that species were species and they never changed into anything else.

  • Artificial selection on dogs, pigeons, cabbages,

  • was a beautiful illustration for Darwin of how plastic things were,

  • you could pull them, it was like modelling clay, almost -

  • you could take a wild animal and pull bits out,

  • press other bits in, enlarge bits.

  • It was showing that there's nothing static about species.

  • Species can change.

  • Now, in his 40s, Darwin became a pigeon fancier.

  • He kept some 90 birds of 16 types,

  • devoured books on breeding and attended numerous pigeon shows.

  • What excited Darwin was the powerful comparison that could be drawn

  • between domestic breeding and what he'd observed of nature

  • acting on wild animals

  • like the finches he'd collected in Galapagos.

  • In the pigeon's case, it's artificial selection,

  • it's human breeders using their eye to choose -

  • I think I'll breed from that one, I want the beak longer, or shorter,

  • I want the plumage to be whiter or fluffier.

  • So, breed from the one that has the quality you want,

  • and then, after surprisingly few generations, you can produce

  • a change in the breed. In nature, it's not like that, of course.

  • Nobody comes along and says,

  • "I want one that has a great big, thick beak."

  • Nevertheless, given that there are tough seeds

  • that only a thick beak can crack,

  • natural selection favours those individual birds

  • that succeed in cracking the seeds,

  • until you end up with this sort of climax beak, which is really huge,

  • the product of tens of thousands of generations of...

  • natural selection breeding for ability to open tough seeds.

  • BARKING

  • Man had utterly transformed many animals and plants

  • by selecting for particular characteristics

  • over and over again.

  • Nature was also doing this.

  • But how could nature make specific choices, as humans could?

  • Darwin's answer would come in understanding

  • exactly what nature is.

  • 150 years ago,

  • Charles Darwin's work revolutionised the way we understand our world.

  • For 20 years, he had pieced together evidence that proved the fact of evolution

  • and developed a theory of how nature, not God,

  • selects life in a similar way to humans breeding pigeons.

  • How does nature select?

  • In the cruellest way.

  • Today, much of the world is controlled and cultivated by man,

  • but there are still a few remote places red in tooth and claw.

  • I've come to Kenya, where I was born.

  • It's one of the wilder places on Earth,

  • where the full force of natural selection can still be seen.

  • As night falls, it's kill, or be killed.

  • ANIMALS GRUNT

  • The total amount of suffering in the natural world

  • is beyond all decent contemplation.

  • During the minute that it takes me to say these words,

  • thousands of animals are running for their lives,

  • whimpering with fear, feeling teeth sink into their throats.

  • Thousands are dying from starvation or disease

  • or feeling a parasite rasping away from within.

  • There is no central authority, no safety net.

  • For most animals, the reality of life is struggling, suffering, and death.

  • For Darwin, grappling with nature's horrors must have been a huge challenge.

  • As a young man,

  • he had wanted to become a country parson.

  • He had believed in an orderly and harmonious animal kingdom.

  • Now, he contemplated the brutal reality of nature.

  • Darwin's brilliance was to connect what he was seeing

  • with an idea from a completely different discipline - economics.

  • Thomas Malthus had written a popular influential diatribe

  • about the perils of population growth in early industrial Britain,

  • and how this would inevitably be stopped by food shortage and disease.

  • Darwin seized upon Malthus's warning about a human struggle for resources,

  • and he applied it to what was happening in nature.

  • As more individuals are produced than can possibly survive,

  • there must in every case be a struggle for existence.

  • Nature is an arena of pressure.

  • Of every individual born,

  • the chance of it surviving to reproduce the next generation is very, very small.

  • Most animals die young.

  • The next step for Darwin was to realise this -

  • what makes the difference between success and failure

  • in the struggle for existence isn't just chance.

  • All living things vary,

  • even if only slightly.

  • Darwin realised this was the key,

  • a tiny variation - sharper teeth or faster legs, keener eyes,

  • better camouflage, better sense of smell can make a crucial difference

  • in an animals chances of survival.

  • If an animal survives, it is more likely to reproduce

  • and crucially, pass those variations on to its offspring.

  • Nature's struggle for existence means that organisms with helpful variations

  • tend on average to survive and reproduce.

  • Those without die without offspring.

  • The race is survival.

  • The finishing line is reproduction.

  • This is what Darwin defined as natural selection...

  • ..the key to evolution.

  • "Natural selection is daily and hourly scrutinising throughout the world

  • "every variation, even the slightest,

  • "rejecting that which is bad,

  • "preserving and adding up all that is good,

  • "silently and insensibly working.

  • "We see nothing of these slow changes in progress,

  • "until the hand of time has marked the lapse of ages."

  • Gradually, very gradually, as successful variations are inherited,

  • natural selection sculpts life into different shapes,

  • better and better adapted to eke resources out of their particular surroundings.

  • Longer necks are favoured to feed from tall trees.

  • Thinner fur for warmer climates.

  • Life forms become ever more specialised.

  • And if separated from their ancestral group by geography,

  • by a forest or desert, on an island,

  • they can specialise to such an extent that they no longer breed successfully

  • with that ancestral group.

  • They are then classified as a distinct species.

  • This is the origin of species.

  • But evolution doesn't stop there.

  • These species are then themselves honed by the presence of other species.

  • The environment in the form of lions is getting systematically worse

  • from the point of view of a zebra.

  • And from the point of view of a lion, zebras are getting systematically worse,

  • they're getting better at running away.

  • Predators are getting better at catching prey.

  • Prey are getting better at escaping from predators.

  • So there's a kind of escalation, it's an arms race.

  • Arms races account for the spectacularly advanced

  • engineering of life -

  • camouflage systems,

  • camera lens eyes, venomous stings.

  • Arms races can be seen in unexpected places.

  • Mankind is certainly not immune to the nightmare Darwin called,

  • "the war of nature."

  • We humans are currently in a battle with viruses.

  • It's being fought all round our world.

  • Today, in the slums of Nairobi,

  • natural selection acts through a virulent disease

  • cutting through the population.

  • Nairobi's prostitutes have, on average, seven to ten clients per day

  • with a high prevalence of HIV which causes AIDS.

  • But genetic researchers have found that some lucky individuals

  • have a weapon in the arms race with HIV...

  • Salome? Yeah. >

  • How are you?

  • I'm Richard.

  • '..a remarkable resistance to the virus.'

  • Can I ask, how long have you been a sex worker?

  • 25 years.

  • And during that time, have you lost many friends to AIDS?

  • I have lost many friends.

  • Many friends?

  • When did you first discover that you are resistant to HIV?

  • She knew for a long time,

  • but she actually believed completely in 1990

  • that she was resistant.

  • She feels God has been good to her and she's the lucky one.

  • Yes.

  • It's not God at work here in all this squalor and suffering.

  • And it's not luck either.

  • The Canadian scientist, Larry Gelmon,

  • has studied the odds of survival.

  • We knew the prevalence of HIV

  • in the sex worker population,

  • we knew the prevalence in the clients they were dealing with,

  • we knew how often they were having sex with these people,

  • and it was a mathematical impossibility that they should have been sex workers

  • for as long as they have with the number of contacts they had,

  • and not become HIV infected.

  • The resistance these women have

  • seems to be a variation that can be passed on to their children.

  • Some of the women are related to each other familially,

  • we also think there is some factor in their blood, in their cells

  • that is probably genetically transmitted.

  • (DAWKINS) I suppose if we came back in 1,000 years,

  • we might expect to see a major shift in the frequency

  • of these genes in the population?

  • (GELMON) Yes, I think in any epidemic situation, those people who are

  • very vulnerable and susceptible will get sick and die.

  • And those people who are going to survive are going to have some kind of resistance

  • which they'll transmit on to their descendants.

  • Just as Europeans today are descendents of those who had the genes

  • to survive the plague,

  • so if Africa's AIDS epidemic took its course,

  • natural selection would favour descendents of women with resistance to HIV.

  • This is the unstoppable force of natural selection first revealed by Darwin,

  • now observed by modern science.

  • Back in England at Down House,

  • now 20 years after his voyage on the Beagle,

  • Darwin had worked out the answers to the biggest questions ever asked.

  • But he was strangely reluctant to go public with his idea.

  • Darwin himself said that he'd become a kind of machine

  • for grinding theories out of huge assemblages of facts.

  • I think that wasn't really what it was like at all.

  • He was an extraordinarily imaginative, deep thinker.

  • He had a prodigiously curious mind as well.

  • He was drawn to facts that didn't fit.

  • He once said, "I cannot bear to be beaten."

  • Darwin's theory explained how the diversity of life from the planet

  • had evolved spontaneously without interference from any god.

  • But he was acutely aware of how upsetting

  • this flat contradiction of the religious story would be.

  • He hesitated to publish.

  • Then, in June 1858, Darwin received a letter

  • from a naturalist travelling in the Far East, Alfred Russel Wallace,

  • which set our similar ideas.

  • Darwin was in despair about being scooped.

  • He was even ready to drop his life's work.

  • But he was persuaded by Charles Lyell and others

  • to present his unpublished work alongside Wallace's notes,

  • and then complete his masterpiece for publication.

  • I've come to meet Randal Keynes, Darwin's great-great-grandson

  • to try to understand Darwin's frame of mind

  • as he finished his book.

  • This is a book about geology by Mr Greenough.

  • It has this wonderful inscription -

  • "Charles Darwin, Buenos Aires, October 1832."

  • So he's on the Beagle,

  • really getting into his stride as a geologist.

  • This is a scrapbook, a children's scrapbook

  • that belonged to Darwin's daughter Annie.

  • 'Darwin was no aggressive polemicist.

  • 'He didn't take to the stage to publicise his work,

  • 'but sought to influence leading thinkers behind the scenes,

  • 'by sending them proof copies of the book with apologetic letters attached.'

  • He would write things like, "This vile rag of a theory of mine."

  • Was that genuine modesty or was there an element of false modesty about it?

  • It was entirely real, um, and this is a very strange point about him.

  • Through the years when he was steeling himself for publication,

  • um, he was, at different times, enormously confident in it,

  • and at other times, he was utterly uncertain.

  • He had a deep fear, I think,

  • that one species would be discovered

  • that had some element of its make-up

  • that could only have been designed.

  • Doubts may have lingered in Darwin's mind,

  • but finally, 150 years ago, he set out his ideas on evolution

  • and how it worked in The Origin Of Species.

  • The book sold out its first run of 1,250 copies within two days.

  • It has never been out of print since.

  • The Origin turned our world upside down...

  • ..but still there was one big gap in Darwin's understanding.

  • 150 years ago, at the age of 50,

  • Charles Darwin finally published the big idea

  • he had sat on for almost 20 years...

  • ..a natural law that explains life itself

  • and the evidence available to him to back it up.

  • This is the most precious book in my collection.

  • It's a genuine first edition Origin Of Species.

  • But it's not just the most precious book in my library.

  • Charles Darwin's Origin Of Species

  • is one of the most precious books in the entire library of our species.

  • This book made it possible

  • no longer to feel the necessity to believe in anything supernatural.

  • It completely revolutionised the way we see ourselves,

  • the world and our origins.

  • But what Darwin never cracked

  • was how the improvements of natural selection

  • were preserved from generation to generation,

  • why they didn't become diluted by interbreeding.

  • It was only in the 20th century, in the neo-Darwinian revolution,

  • that scientists married evolution with genetics.

  • Genes are the long strings of code,

  • instructions to the cells that build all living things.

  • Scientists now realise that genes from the parents

  • don't blend as they combine during reproduction.

  • Each gene is inherited in its entirety...or not at all.

  • The science of the genes also showed how new variations arose.

  • When animals reproduce, their genes are copied,

  • and put into sperm and eggs.

  • During that copying process,

  • occasionally there's a random mistake.

  • Those mistakes are mutations,

  • which give rise to new characteristics

  • on which Darwinian natural selection then acts.

  • And, what's more,

  • genes can be compared with pinpoint precision.

  • The genes in every cell of every living thing

  • are made up of DNA -

  • a code of the same four chemicals, known as A, T, C and G,

  • which these machines can analyse.

  • Whether the cell builds a hamster, a horse or a human

  • simply depends on the order of the letters in the code.

  • Just as Darwin might have predicted,

  • animals more closely related by evolution

  • have more similarities in their code than more distantly related animals.

  • And these codes can be printed out right here in this man's lab.

  • In 2000, Craig Venter was among the first scientists

  • to map the human genome, our sequence of code letters.

  • In the process,

  • this unlocked the ultimate proof of Darwin's Tree of Life.

  • 'He was looking at the visible world and seeing how different it was.'

  • We now have the opportunity, with this toolset,

  • to look at the invisible world, that he could only get hints of.

  • And it shows that there's vast continuity

  • from the simplest life forms to the more complex.

  • He, of course, emphasised diversity, because that's what he saw,

  • the whole organism, but you're finding the incredible similarity

  • that there is between creatures. Even bacteria.

  • To me, it's not a theory any more. I've looked at the genetic code

  • of this wide diversity of species, and it's a continuum.

  • Yes. Well, evolution is a fact.

  • That's right.

  • I mean, there's no question about that,

  • and I'm always being asked, "Well, produce the evidence!"

  • And, really, you're producing the best evidence of any.

  • I mean, fossils are nice,

  • but if we haven't got a single fossil anywhere...

  • The genetic code on its own is enough.

  • the evidence from this lab alone would be...

  • Not just enough but overwhelmingly, staggeringly enough.

  • Darwin anticipated problems with his theory.

  • Modern science has answered them.

  • Evolution by natural selection

  • has been triumphantly vindicated as fact.

  • Case closed, surely.

  • But can I convince those school children?

  • What's so beautiful about DNA

  • is that it's turned biology into a kind of branch of computer science,

  • that every animal and plant is carrying around,

  • inside every one of its cells,

  • an instruction book for making that animal and making its children.

  • You've got billions of letters and you can actually line them up

  • and you can take the rat DNA and the mouse DNA

  • and you line them up and you say,

  • "Same, same, same... Ah! A difference there.

  • "..same, same, same, same... A difference there."

  • And that means that when you say that two animals like rats and mice

  • have a common ancestor, you can be totally confident that that's right

  • because the sheer number of similarities is so gigantic,

  • far, far more than Darwin could ever have dreamed of,

  • and Darwin would just have loved to know about DNA.

  • It's such a shame that he didn't live long enough to learn about DNA.

  • I already believed in evolution,

  • but this has just helped me to understand a bit more about it.

  • We have talked about it in class more, but I still do believe in God.

  • But I'm starting to think whether evolution is true or false.

  • I do believe in evolution

  • but I don't think it's ever going to be 100% accepted

  • because there are many religious people out there.

  • I thought about it more

  • but I still believe in what the Bible tells me.

  • When Richard came to our school today,

  • I started learning about evolution

  • and I'd really love to learn more about it but I don't want to, like,

  • leave my religion and go down that path.

  • I think evolution is the main part of how the Earth developed,

  • but I'll still say my prayers and just keep life going.

  • I only had a few hours with these children,

  • but I hope it'll help them begin to open their eyes

  • to the wonderful reality of life and, at the very least,

  • ask questions about what they've been brought up to believe.

  • Darwin used to do a lot of his thinking

  • on solitary walks along this path around his home, Down House.

  • At the end of Origin Of Species, he contemplated how an entangled bank

  • along a lane like this,

  • with its teeming life of plants, birds, worms and insects,

  • had been formed by the unseen laws acting around us.

  • "There is grandeur in this view of life.

  • "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."

  • Thanks to Darwin, we, alone of all species,

  • know that each and every one of us

  • is a thread in the evolved fabric of life.

  • Darwin showed us

  • that the world is beautiful and inspiring without a god.

  • He revealed to us the glory of life

  • and opened our eyes to who we really are

  • and where we've come from.

  • In the next programme,

  • Darwinism applied to mankind and our society,

  • its terrible misuse in attempts to justify cut-throat competition,

  • even genocide.

  • In the world of the selfish gene, what hope for the human species?

This series is about perhaps the most powerful idea

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