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00:00There are some great questions that have intrigued and haunted us since the dawn of humanity.
00:12What is out there?
00:18How did we get here?
00:24What is the world made of?
00:26The story of our search to answer those questions is the story of science.
00:37Of all human endeavours, science has had the greatest impact on our lives, on how we see the world, on how we see ourselves.
00:46Its ideas, its achievements, its results are all around us.
00:51So, how did we arrive at the modern world?
00:56Well, that is more surprising and more human than you might think.
01:01The history of science is often told as a series of eureka moments.
01:11The ultimate triumph of the rational mind.
01:14But the truth is that power and passion, rivalry and sheer blind chance, have played equally significant parts.
01:21In this series, I'll be offering a different view of how science happens.
01:30It's been shaped as much by what's outside the laboratory as inside.
01:34This is the story of how history made science and science made history.
01:43And how the ideas that were generated changed our world.
01:48It is a tale of power, proof and passion.
01:55This time, the most personal question we've asked.
02:10How did we get here?
02:12How did we get here?
02:28It's a question that provokes fierce argument and huge controversy.
02:33And that's because it gets to the heart of our human origins.
02:36Our very significance.
02:39And yet, until relatively recently, it was not a question that people felt they had to keep asking.
02:45Most people believed they already knew the answer, handed down in religious text or in creation stories.
02:53We and everything else on earth had been put here by some kind of supernatural power.
03:06What's special about this question is not how long it took to get answered, but how long it took to get asked as a scientific question.
03:21And it's a story that begins over here.
03:24The great voyages of discovery of the 15th century heralded the start of the modern age.
03:43Advances in navigation and shipbuilding allowed European adventurers to explore and exploit the rest of the globe.
04:01We're absolutely stormy along now, powered by the trade winds.
04:06And over there is the Caribbean island of Jamaica.
04:09In 1494, Christopher Columbus landed here.
04:15It was a completely unknown part of the world, at least unknown to Europeans.
04:19It is the Americas.
04:20The discovery of the Americas sent shockwaves through European civilisation.
04:36New peoples, new plants, new animals.
04:39The early explorers arrived utterly convinced that they were special, set apart from the rest of nature.
04:48The pinnacle of God's creation.
04:56Yet what they found here would begin to challenge that.
04:59And for me, the story begins with a man called Hans Sloan, an Irish doctor who arrived in Jamaica in 1687 to take up the lucrative post of personal physician to the island's governor.
05:15To be fair to Sloan, he was more than simply an adventurer in search of a past buck.
05:26He was also a passionate botanist who loved to go exploring the island on horseback with a guide.
05:31Okay, Marlon, you ready to go?
05:33Yep.
05:34Lovely.
05:40Elegantly done.
05:45Don't want to be left behind.
05:46My guide, Marlon Beale, is a botanist, and together we're headed for the Blue Mountains, where Sloan would come face to face with what he described as all that is extraordinary in nature.
06:12Now, I know that Sloan was a doctor and he was particularly interested in plants which had any sort of medicinal quality.
06:20Yes.
06:21So if you see any, do let me know.
06:22Definitely, I will.
06:24Since most 17th century medicines came from plants, it's not surprising that finding new species was high on Sloan's agenda.
06:35Ah, there we go.
06:38Ah, smell it.
06:39Very pretty.
06:40Yeah, taste it if you want.
06:41Which end do I taste?
06:43That end, the cut end.
06:44Okay.
06:47That's ginger, isn't it?
06:49It's wild ginger.
06:53Interesting, because Sloan wrote quite a lot about wild ginger.
06:56He believed that ginger was very good for the stomach.
06:59Don't know about that, but it's certainly good for seasickness, and if you were doing a two-month voyage across the Atlantic, then this would be rather useful.
07:05Sloan also claimed that wild ginger was good for treating cancers. Not sure about that either. Quite tasty there.
07:14What's gonna happen now?
07:15In the US?
07:16What?
07:17Oh no, it's Dang.
07:18Oh, an interest in nature wasn't confined to collectors like Sloan, because in nature, and particularly plants, lay the foundations of European imperial power.
07:29lay the foundations of European imperial power.
07:35Trading vessels crisscrossed the globe,
07:37bringing home all sorts of natural produce.
07:40From tobacco and spices to tea and timber,
07:43the botanical booty was practically limitless.
07:48Even the ships which carried the goods
07:50were themselves made out of plants.
07:53There were trees for the framework,
07:55hemp provided the sails and the ropes,
07:58and they used pine resin to produce pitch,
08:02which was used to waterproof the ships.
08:13What distinguished Sloane from most traders and plantation owners
08:16was an interest in all of nature,
08:19not just plants but also animals.
08:24This interest would open the world's eyes
08:26to the beauty of God's creation
08:29and, crucially, to the puzzle of its incredible diversity.
08:35There aren't very many big animals here in Jamaica,
08:38but there are an awful lot of lizards.
08:40And what Mull's about to do is make a little noose, I think.
08:43Is that right? Yes, a noose.
08:45And hopefully we'll capture a few lizards.
08:47Is this the sort of thing that Sloane might have used?
08:49Possibly, because this would be the most conventional method at that time.
08:53Just tight.
08:54And all we've got to do now is persuade the lizard to stick its head in.
08:58To stick its head in, sir.
09:00Very neat.
09:01A beautiful noose for catching lizards in the style of Hans Sloane.
09:06Where are we likely to find the marlin?
09:11Well, you can find some on the ground or even on trees,
09:14so both looking on the ground and on trees is great.
09:17OK.
09:19It was this type of hands-on approach...
09:21I think there's one over here.
09:23..that enables Sloane to collect so many different specimens of Jamaican wildlife.
09:28Ah!
09:29He jumped.
09:30I think he's gone.
09:31Ah!
09:32Michael.
09:33Do you see something?
09:34Yeah.
09:35So on the right.
09:36Right there.
09:37See?
09:38Let's go have a go.
09:39Brilliant.
09:40There we go.
09:41Is he safe to hold?
09:42Yep.
09:43Maybe a bit feisty.
09:44Yeah.
09:45So I'm going to try and get the noose off of him.
09:48Oh, brilliant.
09:50There we go.
09:51Is he safe to hold?
09:52Yep.
09:53Maybe a bit feisty.
09:54Yeah.
09:55So I'm going to try and get the noose off of him.
09:57How many different species of lizard are there?
10:00There are many different species.
10:02Over 20 different species.
10:04Right.
10:07I think we've done very well.
10:08Yeah.
10:09This book takes illustrations of just some of the things that Sloane captured in Jamaica.
10:29Look at the snake there.
10:31There's our friend the lizards.
10:33I think the one I helped capture is the one in the middle there.
10:36The book is just full of beautiful drawings.
10:40The birds.
10:41The fishes.
10:42The thing is that Hans Sloane came to Jamaica not just to revel in its beauty, but to record
10:49everything he saw, which he did in enormous detail, so that other people who couldn't come here
10:54could enjoy and learn from what he had discovered.
11:04After 15 months on the island, Sloane returned to England.
11:10He brought back with him some 800 samples of flora and fauna.
11:15A fully grown crocodile and a recipe for drinking chocolate.
11:21Unlike many explorers who returned from the Americas with tall tales of giant sea serpents
11:27and men whose heads grow beneath their shoulders, Sloane returned with real data and real specimens.
11:38There was no reason as yet to think that all this diversity had anything to do with us.
11:45But it did unsettle traditional ideas of God's creation of the natural world.
11:51For people who believed that God had created the world and everything in it, permanent and perfect,
11:57this was also utterly bewildering.
12:00Why had God bothered to make so many small and apparently pointless variations on the theme?
12:06Why so many lizards?
12:08Why so many beetles?
12:10The question started to come thick and fast.
12:14By the time Hans Sloane died in 1753, he had put together the world's greatest collection of natural objects.
12:29Most of which are still with us today.
12:32In front of me we have part of the Sloane Herbarium.
12:37There are many, many thousands of objects, about 14,000 of these vegetable substances.
12:44Flowers, fruits, dried objects which we can't press.
12:48And with that there are about 270 bound volumes with many, many thousands of specimens in them.
12:56So vast was Sloane's horde of wonders that it was moved to a new type of institution, beginning to appear across Europe.
13:11The National Museum.
13:13Private collections like Sloane's could now be seen by a much wider audience.
13:23Bringing nature out of the wilderness and into the everyday world.
13:30This new curiosity about life on Earth would bring us closer to the question, how did we get here?
13:49It was fuelled by voyages of discovery and the money to be made from nature.
13:56By obsessive collectors like Hans Sloane, who began to document nature's diversity.
14:05And by museums where ordinary people could see it for themselves.
14:10And it now turned out that all this life also had a history.
14:16A rather rich one.
14:18Paris, just after the French Revolution.
14:34Where the belief that God's creation was fixed and unchanging was about to be further undermined.
14:41By a brilliant anatomist.
14:43And a taste for new buildings.
14:49Paris is a city in love with its own beauty.
14:52Whatever events may have been dominating the headlines,
14:55the fall of the Bastille, the execution of the king,
14:58one thing has remained constant.
15:00The city's determination to build on its rich architectural heritage.
15:11Buildings began to appear which were every bit as magnificent as their predecessors.
15:19While others were added to.
15:21For example, the Louvre.
15:26In the years following the revolution, it grew from a Bourbon palace
15:31into a museum large enough to house France's rapidly expanding art collection.
15:37But I'm less interested in what's in there than what's out here.
15:41And in particular, this stuff. Limestone.
15:47A rock which for centuries had been the mainstay of Parisian architecture.
15:53Now this limestone was hewn from a quarry that is very near to where I'm standing now.
15:59A hidden one.
16:00A hidden one.
16:01One that is down there.
16:12Deep beneath Paris lies an old network of stone quarries,
16:17linked by hundreds of kilometres of connecting tunnels.
16:22Together they form a mirror image of the city above,
16:25right down to the street names.
16:27People began quarrying away underneath Paris in the Middle Ages.
16:38And they went on digging for hundreds of years.
16:41There should be a sign just over here.
16:43Yes. 3R.
16:45This is the old revolutionary calendar,
16:47and it means three years after the start of the French Revolution.
16:51At that time, houses being built over my head
16:53would have contained limestone from quarries just like this one.
17:02Hello.
17:03I'm Gilles. It's a pleasure to meet you.
17:05And you?
17:07I guess actually quarrying down here must have been pretty dangerous.
17:11It could be dangerous.
17:13It's the reason why quarrymen put this handmade pillar
17:15to protect them from falling roof, from collapse.
17:19And who actually dug these areas?
17:22It's specific to France when you are owner of the surface,
17:26you are owner of the underground until the centre of the earth.
17:29To the centre of the earth under French law?
17:31Yes, according to the French law.
17:32How interesting.
17:33As more and more quarries were excavated,
17:44people began to take a greater interest
17:47in the mysterious objects they were finding embedded in the rock.
17:52Ah!
17:54That's magical, isn't it?
17:56You can see that really clear shell.
17:58It must have been very strange for the workmen who first came down here
18:02when they realised they were looking at something
18:04which should be on the ocean floor.
18:08What they were looking at, of course, were fossils.
18:18For a long time, people had no idea what fossils really were.
18:22Some people claimed they had come from the moon.
18:25Others, that they were Mudd's unsuccessful attempt to turn into life.
18:30In fact, it wasn't until the end of the 18th century
18:33that people fully appreciated they had once been living things.
18:37And this realisation opened up a whole new window into the past.
18:41A past that was both ancient and unimaginably different.
18:58Here in France, many of those fossils ended up in the hands of a brilliant scientist.
19:03A man obsessed by old bones.
19:05His name was Georges Cuvier, and he was widely regarded as the world's leading animal anatomist.
19:22There was barely an animal in existence whose remains hadn't come his way.
19:27There's a story about Cuvier, which I like, which I think really sums up the man.
19:36It's late at night, and Cuvier has gone to bed.
19:40When one of his students, dressed in a devil's costume, bursts into his room and cries,
19:46Cuvier, Cuvier, I have come to eat you.
19:49Cuvier opened one eye, calmly looked the student up and down, and said,
19:57All animals that have hooves and horns are herbivores.
20:01You cannot eat me.
20:05Now the point is that Cuvier had realised that from a couple of features
20:10you could work out the essential nature of any animal.
20:13This insight would lead Cuvier to propose a new, and to many minds, unthinkable story of life on Earth.
20:25Now I'm no Cuvier, but I did train as a medical doctor, and so I've seen a lot of bones, albeit human ones.
20:32In here I've got some fossil bones, and I'm going to try and see if I can work out where they came from.
20:36Right, I think this is the sort of end bit of the finger, but in this case it has a big claw attached,
20:45so I'm guessing this comes from a carnivore. I'm going to go and hunt carnivores.
20:52By examining the form of any body part, Cuvier claimed you could discover everything there was to know about its function.
20:59It's a bit like a crocodile claw, but not really close enough.
21:06And from its function, its likely source.
21:09Bigger. Not bad. That's a dog.
21:13I think that's about right.
21:17I guess that this is from a hyena.
21:21Let's see if I'm right.
21:22No. Close, though. It's from a wolf, apparently. A wolf.
21:31Cuvier was clearly better at this than me, and this allowed him to identify many previously unknown fossils coming out of the ground.
21:42But also some remains that would have unsettling implications.
21:46One of the fossils that Cuvier was sent was this one.
21:52It is, believe it or not, a giant tooth.
21:56You can tell that because this is the enamel or biting there over here.
22:00Now, the people who found this fossil were convinced it came from an elephant.
22:04But Cuvier had other ideas.
22:05The fossil I've got here is obviously much bigger than the elephant tooth you've got there.
22:13But what other features did Cuvier notice were different?
22:16Well, you say the size, of course, you are right.
22:19But in this African elephant tooth, you can see that the enamel is very different on the grinding surface.
22:27There are diamond enamel lamina. Here, there are parallel lamina, and there are more numerus than the African elephant.
22:39So there's a very important difference.
22:41He knows that this tooth was coming from Russia, and this tooth was called by Russian the mammoth.
22:48Ah, it's a mammoth.
22:49A mammoth?
22:50Right. So he was able to look at this and go, it's an elephant, but a much bigger elephant and a very different sort of a third species of elephant.
22:58Right, right.
23:04The revelation that the mammoth was a species totally distinct from any living elephant was nothing compared to Cuvier's next bombshell.
23:15Cuvier thought long and hard about mammoths, and he came to a surprising and radical conclusion.
23:23Now clearly mammoths are enormous beasts, yet no one had ever seen one, which suggested that at some point in the past, mammoths, all of them, must have gone extinct.
23:34And it wasn't just mammoths.
23:46Before long, hundreds of other strange looking fossils began to be identified as creatures that had mysteriously disappeared off the face of the earth.
23:56The claim that some animals that had once lived had gone extinct raised uncomfortable questions.
24:08If every creature in God's fixed universe had a place and a purpose, why had some died off?
24:14The suggestion that most of the creatures who had ever lived were now extinct was both baffling and disturbing.
24:31The only consolation was that this was still a history of life which we humans were separate from.
24:37For now, the most pressing question raised by extinction was one of time.
24:49And whether this fossil record of long lost species was evidence that the earth was older, much older than previously believed.
24:59The 18th century was the age of the experiment.
25:15There were experiments on light, liquids, gases,
25:21gases, but also an experiment to establish the precise age of the earth.
25:30The man behind the experiment was Le Camp de Buffon.
25:34A fabulously wealthy French aristocrat, Buffon was the first person to seriously attempt to measure the age of the earth.
25:41And he did so using some metal balls, a pocket watch and a blacksmith's forge.
25:51Good morning, Brian.
25:54Good morning.
25:55Hi there, Michael Mayersley.
25:56Good morning, Michael.
25:57I have a present for you.
25:58Ah, right.
25:59Two metal balls.
26:00I think you know what to do with them.
26:01Yes, indeed.
26:05You might imagine that back in Buffon's day, most people believed that the world was created in six days and was 6,000 years old.
26:14In fact, a lot of people, including many clerics, did not take the Bible that literally.
26:21Buffon was not unusual in suspecting that the earth might be very old.
26:26Where he was unusual was he was prepared to do an experiment to find out just how old.
26:32Right.
26:35Anything I can do?
26:36Give it a nice long stroke.
26:37Just slow, straight down.
26:39Warm it up nicely.
26:40How long will it actually take to heat up, to red hot?
26:43Probably the best part of an hour, looking at the size of the ball.
26:49The experiment was actually based on a suggestion by Sir Isaac Newton.
26:52He said, imagine the world had started off as a red hot piece of iron.
26:59If you could work out how long it could take him to cool from that state to the present state,
27:04then you could work out just how old the earth really is.
27:11By timing how long it took the different size balls to cool down,
27:16Buffon was confident he could extrapolate his figures
27:19and establish how long it had taken the earth to reach a similar state.
27:24Do you reckon they're ready yet, Brian?
27:26Well, they're well up to temperature, yes.
27:28It's hot, isn't it?
27:30Yeah.
27:31I'm trying to avoid dropping this on my toes.
27:34Take that down there.
27:38Brilliant.
27:40I've got my pocket watch here now.
27:42So, how long do you think before we can actually touch them?
27:45Looking at at least 25 minutes or even longer for the small one.
27:48The larger one's much more mass, probably an hour.
28:00A little later and I'm finally ready to start to plot my graph.
28:05Extrapolating my timings for the two balls
28:09to allow for the much bigger diameter of the earth.
28:13Right.
28:15Now for the age of the earth using Buffon's method.
28:19I calculate the age of the earth at 92,000 years.
28:24And Buffon, well, he said it was a suspiciously accurate 74,832 years old.
28:34As we now know, both these figures are in fact way out.
28:43Wildly inaccurate, though Buffon's method was, it would be churlish to let that detract from his legacy.
28:49The important point is that by doing the experiments and by publishing the results, Buffon sparked a debate.
29:01Not just about how old the earth actually is, but how and why every creature on earth came into being.
29:07A debate that would now be intensified by a new way of looking at the world.
29:24Standing between Northern and Southern Europe is one of the world's most formidable natural barriers.
29:30The Alps.
29:33Even as late as the mid 18th century, no one had yet climbed this region's highest peak.
29:40Mont Blanc.
29:41In 1760, a young Swiss aristocrat called Horace Benedict the Saussure came to the small alpine village of Chamonix in the foothills of Mont Blanc.
30:04Now, he came originally to collect plants, but he soon became so enchanted by the mountain that he offered a reward to the first person who could climb it.
30:19Despite many attempts, it was 26 years before anyone managed to reach the summit.
30:29De Saussure himself got to the top a year later.
30:32But De Saussure was much more than a rich man with a passion for extreme sports.
30:40For once he'd climbed Mont Blanc, he proceeded to carry out a series of experiments to discover much more about the mountain.
30:49Going to remote places and getting your hands dirty was a new way of trying to understand the processes that shaped the earth.
30:57And De Saussure gave it a name, geology.
31:03With its emphasis on direct observation, this new way of looking at the earth would play a vital role in unravelling not just the mysteries of the planet, but also the entire history of life on earth, including ours.
31:17All across Europe, practically dressed men, armed with small hammers, headed off into the countryside in search of the earth's hidden secrets.
31:35Driven by an intense curiosity that would have surprised their predecessors, they began to notice a number of strange anomalies in the landscape.
31:48I've come here to the east coast of Scotland, to a place called Seca Point.
31:54It is wild, windy and rather beautiful.
31:57And just down there is something truly remarkable.
32:00Something which an early geologist who came here described as like looking into the abyss of time.
32:05This is what I've come to see, and it is very strange indeed.
32:27It's called an unconformity.
32:30What you have down there is layers of rock that appear to be laid down vertically.
32:35And then just above them, a layer of red sandstone, which appears to be laid down horizontally.
32:42But as odd as this may seem, to some there appeared to be a startling explanation.
32:57This layer of rock looks as though it was laid down vertically.
33:01But at some point in the past, it must have been at the bottom of the ocean and formed horizontally by layer after layer of sediment.
33:09Then the whole thing rose to the surface, which flipped through 90 degrees and sank to the bottom of the seas again.
33:16There, another layer formed.
33:19Until finally, the whole thing rose to the surface once again.
33:28All these processes are extremely slow.
33:31And all this implied that the earth is incredibly old, practically eternal.
33:39And it wasn't just Sica Point.
33:44The evidence for slow change was everywhere.
33:48Geologists looked at waterfalls and saw how the constant flow of water had gradually eroded the surrounding rock.
33:58They saw how rain had inexorably worn away the tops of mountains.
34:08And how the slow movement of glaciers had carved out entire valleys.
34:13They came to realise that the single most important factor in why the world looks the way it does was time.
34:26And lots of it.
34:28The moment that people first began to think in terms of deep time is one of the most significant in the history of science.
34:39And it would go on to profoundly affect how people see themselves.
34:43But trying to grasp deep time is extremely difficult because it is so different to human time.
34:48So you have to rely on analogies.
34:51One of my favourites is to imagine the age of the earth as a length from my shoulder to my fingertip.
34:58On that scale, the whole of human history, everything we have achieved in the last few thousand years, would be wiped away by the single swipe of a nail file.
35:09So, why did this concept of deep time take root now?
35:18There was the expansion of quarrying and mining, exposing more of the hidden earth.
35:25The fossils of extinct creatures that were being uncovered.
35:31And the emergence of geology, a new scientific view of the planet.
35:35Finally, the pieces were in place to try and answer the question, how did we get here?
35:52The Industrial Revolution was a time of rapid, dizzying change.
35:58Great industrial cities spread across Victorian Britain,
36:02their factories drawing in workers from far and wide.
36:09New railways snaked across the landscape, cutting journey times,
36:14and bringing cheap goods to the masses.
36:20It was a whirlwind of new ideas, new methods, and all of it in the name of progress.
36:27Belief in progress was one of the defining characteristics of the Victorian age.
36:36Factory owners from humble origins had country houses, even seats in Parliament.
36:42Britain was the leading industrial country in the world, thanks to the ingenuity of her people.
36:46It was out of this belief in progress that a radical theory of how we got here exploded onto the scene.
37:02The theory proposed that not only were societies and nations capable of progressive change, but also nature.
37:18In 1844, this slim, rather ordinary looking book was first published, and it swiftly became one of the most controversial books of the Victorian age.
37:36It was a literary sensation selling tens of thousands of copies, and it was read by everyone of influence from the Queen downwards.
37:54Adding to its mystique was the fact that its author made strenuous efforts throughout his lifetime to remain strictly anonymous.
38:09The author was a Scotsman, Robert Chambers.
38:13Robert Chambers was born with six fingers and six toes.
38:19When he was young, he had an operation to get rid of the extra digits, which unfortunately went wrong.
38:25Self-conscious, Robert now immersed himself in the world of print.
38:34Few changes embodied the Victorian ideal of progress as much as the 19th century transformation of the print industry.
38:44The steam-powered printing press ushered in a new age of cheap, mass-produced books, creating a hunger for knowledge right across society.
38:57In response to this demand, Robert Chambers helped his brother set up a successful publishing firm,
39:04while still leaving enough time to devote to his first love, writing.
39:09Robert Chambers was not a very original thinker, but he was well-read.
39:16His writing was clear, vivid, and above all, thought-provoking.
39:21It was these qualities, plus the fact that he had an insider's knowledge of the publishing industry,
39:27which ensured his book was a huge success.
39:29Chambers called it vestiges of the natural history of creation, and in it he presented a compelling case for the notion that species are not fixed.
39:42They change.
39:44They change.
39:48That everything had developed from an earlier form.
39:51He called this concept transmutation.
39:55We call it evolution.
40:05Evolution emerged out of a world of progress.
40:08A conviction that all things are capable of change, of improvement.
40:13A history of life that was as diverse as it was baffling.
40:19And a realisation that the earth was almost immeasurably old.
40:26But the real significance of evolution to this story is that it now forced people to confront the uncomfortable question.
40:34How did we get here?
40:35Chambers was not the first person to write about evolution, but he did take the argument further than others had.
40:45Instead of being set apart from the rest of creation, Chambers was saying we were simply an extension of it.
40:51No wonder he wanted to remain anonymous.
40:53For a society where people fervently believed that humans had a special place in God's creation, the claim we were descended from animals was deeply shocking.
41:12And so the backlash began.
41:15There were attacks from the scientific community on the book's accuracy.
41:20And from the clergy for undermining moral and social order.
41:27One particularly scathing review described it as not merely shallow and superficial, but utterly false throughout.
41:37Harsh.
41:39But despite the controversy, or let's face it, probably because of it, the public simply couldn't get enough of this book.
41:44For all its success, what Chambers' book didn't do was come up with an explanation of how evolution happens.
42:01The man who answered that question was, of course, Charles Darwin.
42:05A keen geologist and ardent believer in the Earth's antiquity, Darwin had been working on his own theory of evolution for several years, when vestiges first appeared.
42:19But it would be a further 15 years, by which time much of the fuss surrounding evolution had died down, before Darwin felt ready to publish.
42:33His explanation for how animals evolved had its roots in the same industrial landscape from which Chambers' book had emerged.
42:50According to Darwin, life was one long struggle for survival.
43:07And just as within the cotton industry there was competition between manufacturers, so in nature there was competition between and amongst species.
43:15Just as new technology might give one factory an edge over another, so it was in nature.
43:29Any new trait that gave an organism an edge over its rival would prevail, and become more common in later generations.
43:40Gradually giving rise to the appearance of new species.
43:45A mechanism for change that Darwin called natural selection.
43:58Darwin's followers must have hoped that his theory of natural selection would help answer the question, how did we get here?
44:05But there were holes in the theory.
44:07Although Darwin acknowledged the critical importance of the environment on driving evolution,
44:11he never fully grasped the incredible extent to which life on Earth is shaped by changes in our violent planet.
44:19Something which has only relatively recently come to light.
44:23While biology raced ahead in the early 20th century, geology had more or less settled into a routine.
44:36Stones were dated, fossils examined, collections expanded.
44:43But, as so often happens in the story of science, it's the non-specialists, the enthusiasts who shake things up.
44:51One such enthusiast was Alfred Wegener.
44:56He was a German meteorologist, a weatherman, and with his brother he held a world record for ballooning.
45:03He was not, however, a trained geologist.
45:05But that didn't put him off proposing a radical and controversial new theory about the forces that shaped the Earth.
45:14Forces so powerful as to have shaped even life itself.
45:22The story goes that Wegener was looking at an atlas when he noticed something rather peculiar.
45:27So take a map of the world, a pair of scissors, and cut your way down to Greenland until you get to the coast of South America.
45:38And then it requires a little bit more finesse, working your way carefully round Brazil.
45:45And then at the end just slash away again.
45:47Now, if you now move the coast of South America over the coast of Africa, what you'll notice is that they seem to match very closely.
45:57It's almost as if they were once joined.
46:02Wegener noticed this, but he did nothing about it for around a year until he came across some fascinating fossil finds.
46:17Take a look at this. It's a fossilized leaf, and it's about 250 million years old.
46:27It came from a tree fern that is now extinct.
46:30Now, the odd thing is these tree ferns grew in the tropics, but these fossils have been found in cold, remote places like this one.
46:39In fact, places even colder than here in Iceland.
46:43So how was that possible?
46:47And then there were reptiles.
46:51A particular species of reptile found in South America, but mysteriously matched by exactly the same species in Africa, more than 7,000 kilometers away.
47:04In attempting to explain these mysteries, Wegener would transform geology.
47:09Science would have to embrace a new and very different history of life on Earth.
47:16Wegener developed a theory that was logical, but also, on the surface, completely ludicrous.
47:29He suggested that all the great seven continents had once been clumped together into a single supercontinent that he called Pangaea, meaning all lands.
47:38And then Pangaea had simply split apart.
47:42A process that Wegener attempted to illustrate.
47:47Wegener compared the moving continents to the huge floating icebergs he'd seen on his many field trips to Greenland.
48:03But instead of blocks of ice weighing a few thousand tons, he was talking about great slabs of rock weighing trillions of tons.
48:16The problem for Wegener was nobody was buying his big idea.
48:19To his eternal frustration, Wegener had no way to explain how the slabs moved.
48:28No hard evidence to convince the skeptics.
48:32One of Wegener's many critics described his ideas as utter damned rot.
48:38And you can see why.
48:40The idea that we are floating around seems preposterous.
48:43And it didn't help that Wegener was an amateur geologist.
48:48In many eyes, a jumped up weather forecaster.
48:53Wegener went back to meteorology.
48:56And his theory was shelved.
48:59Until a series of unexpected discoveries made during the height of the Cold War.
49:05In the 1950s, as the Cold War intensified, the United States and the Soviet Union found themselves engaged in a game of cat and mouse deep beneath the ocean.
49:24A game that demanded a much more accurate picture of this underwater landscape.
49:29And so, the oceanographers set to work.
49:39They began taking thousands of photographs of the ocean floor.
49:47Echo soundings plotted the rise and fall of deep sea ridges.
49:52While drill rods were sent down to establish the composition of the sea bed.
50:05But, in mapping the oceans, the scientists discovered something entirely unexpected.
50:10They found that the sea floor didn't consist of one thick uniform crust, as used to be thought, but a number of thin interlocking plates.
50:26And that the boundaries to those plates featured mountain ranges.
50:30Deep rift valleys.
50:34Deep rift valleys.
50:39Even volcanoes.
50:47And this entire landscape was floating on a bed of molten rock, constantly on the move.
50:53And you can also see evidence of this on dry land.
51:11I've come to think back clear in Iceland.
51:14One of the wonders of the world.
51:15It is one of the few places on Earth that you can actually see, with your own eyes, the joins in our patchwork planet.
51:23This may look like an ordinary cliff edge, but it is actually the start of the enormous great slab of rock,
51:30which extends all the way from here in Iceland, across the Atlantic Ocean, across the Atlantic Ocean,
51:36across North America, to the Pacific Ocean, across North America, to the Pacific Ocean.
51:54It is called the North American Plate.
51:57And just over there, well, that is the beginning of another enormous plate.
52:01It is called the Eurasian Plate, and it extends all the way from here to Shanghai.
52:12Now, if I was to stand here long enough, say, a few thousand years,
52:17I'd notice the gap between me and Eurasia was getting wider.
52:24Scientists have measured this movement.
52:26It ranges from a very gradual seven millimetres a year here at Thingvagliir,
52:32to almost ten centimetres a year elsewhere.
52:37Over hundreds of millions of years, this shifting of the Earth's plates has transformed the face of our planet.
52:45A never-ending cycle of change that Wegner had called continental drift.
52:51Sadly, Wegner didn't live long enough to see his theory vindicated.
52:57In 1930, he went on an expedition to Greenland.
53:01There, in temperatures of minus 60, he died of cold and exhaustion.
53:05He was buried on the ice.
53:08Because of continental drift, his body is now two metres further away from home.
53:13But continental drift has done much more than shape the Earth.
53:27By showing how a fossilised tree fern could travel all the way from the tropics to the ice,
53:33or why it is that a single species of reptile can be found on what are now two widely separated continents.
53:41The theory also takes us closer to solving the mystery of how we got here.
53:46And that's because when the Earth moves in this way, the results can also be incredibly violent.
54:02When the Earth's plates collide,
54:06they can trigger volcanic eruptions so powerful as to block out the Sun for months on end.
54:12As those same plates grind against each other.
54:21So they cause devastating earthquakes.
54:27Which themselves can spawn mega tsunamis that destroy everything in their way.
54:33Well, it's easy to imagine that all this violent upheaval brought with it nothing but death and destruction.
54:46The truth is very different.
54:48It's now clear that throughout our four and a half billion year history,
54:53the violence of our planet has been absolutely central to the creation of new life.
54:57Because every time our planet experiences violent change, a new opportunity for life opens up.
55:16Making continental drift one of the great drivers of evolution.
55:21And here are just a couple of ways it has changed life on Earth.
55:27Some 30 million years ago, the plate boundary separating Africa from Arabia began to pull apart.
55:36Causing the land in between to fall away.
55:39A 5,000 kilometer gash in the Earth's crust that we know as the East African Rift Valley.
55:54As a new landscape of broken savannah formed,
55:58it allowed the ancestors of many of today's animals to gain a foothold and to flourish.
56:03And then there is climate change, where continental drift has also played a major role.
56:20Not least by accelerating the onset of ice ages.
56:24By pushing land towards the poles and altering the flow of ocean currents.
56:29Changes which have forced animals to adapt in the most remarkable of ways.
56:42And, just occasionally, we're subjected to violence.
56:49From beyond our planet.
56:51So extreme that many species are wiped out altogether.
57:01Only for others to take their place.
57:11And so, what of us?
57:14How did we get here?
57:15Well, we are just the latest in a long line of lucky survivors.
57:23Born out of death, destruction and the immensity of deep time.
57:32And if this great experiment, that is life on Earth, were to be run again...
57:37We might never even show up.
57:46It's now clear that the story of life and the story of our planet, which were once seen as separate, are actually intrinsically linked.
57:59The evolution of new life has been driven by climate change, by asteroid impacts and by the slow motion collision of continents.
58:11It turns out that we and every other living creature are marching to the drumbeat of our violent planet.
58:18Next time, an ancient human ambition, the search for limitless power.
58:46And the story of science continues here on BBC HD on Tuesday at half past ten.
58:56The Art of the Sea is later this evening at ten.
58:59But first, we're off to the land of the Northern Lights with Joanna Lumley.
59:03interaction focusing
59:12awareness in the environment.
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