- 4 weeks ago
How flowering plants transformed barren prehistoric landscapes, outcompeted ancient species like conifers, drove the evolution of animal life, and eventually sculpted human history.....
在花朵进化之前，地球上主要由蕨类植物和针叶树等原始植物组成，它们依靠风力传播花粉。这种方法效率低下，需要植物浪费大量的能量.....
在花朵进化之前，地球上主要由蕨类植物和针叶树等原始植物组成，它们依靠风力传播花粉。这种方法效率低下，需要植物浪费大量的能量.....
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LearningTranscript
00:00:08I spent most of my life trying to understand the forces that shaped our planet.
00:00:12And as a geologist it always seemed to me that rocks were right at the heart of things.
00:00:22But now I'm discovering it's not only volcanoes and colliding continents
00:00:27that have driven the Earth's greatest changes.
00:00:31Because at crucial moments in its history another force has helped create the planet we live on.
00:00:39Plants.
00:00:42It's a whole new story about the Earth.
00:00:46Revealing how from its earliest history plants have shaped our world.
00:00:55So far we've seen how plants and their ancestors began by producing a life giving atmosphere.
00:01:02And breathing oxygen that was made two and a half billion years ago.
00:01:10They'd harnessed light from the sun bringing energy to the world.
00:01:15And they'd formed the fertile soil.
00:01:18Allowing life to colonise the land.
00:01:30But the next chapter will take us even further.
00:01:33Because a powerful newcomer to the plant world was on its way.
00:01:37It would conquer every corner of the planet.
00:01:42It would shape the very surface of the Earth.
00:01:45And it would drive the evolution of animal life.
00:01:50Including our own ancestors.
00:01:53This is its story.
00:02:16These buildings are nearly a thousand years old.
00:02:21The largest religious site in the world.
00:02:24Covering 200 square kilometres.
00:02:29This is the temple of Angkor Wat.
00:02:32In Cambodia.
00:02:36I'm here to witness the importance of one of the most powerful symbols known to humankind.
00:02:45A symbol central to an ancient Buddhist ceremony.
00:02:53Flowers.
00:03:02You see lotus flowers and jasmine just arranged beautifully up there.
00:03:08The lotus, the big ones, and jasmine, a trail of little flowers.
00:03:12See how the lotus petals are all folded in amongst themselves.
00:03:16The different layers representing the various levels of heaven.
00:03:22For these monks, flowers have a crucial role.
00:03:27And this is just one ceremony.
00:03:30From one religion.
00:03:32Flowers are central to cultures throughout the world.
00:03:37They're deeply woven into all our lives.
00:03:43The 6th ayudate.
00:03:44The 21st Henrietta Laptop.
00:03:47TheJiles d pizza at tennis.
00:03:48The transfifical journey.
00:03:48The 2nd Thames.
00:04:09The 23 crit왕.
00:04:09The central Thames depoisema.
00:04:11But it's not only a human obsession, because since they evolved, flowers have been the
00:04:18driving force for the whole of life on earth.
00:04:25They've become enmeshed in the lives of virtually the entire animal kingdom, in all its rich
00:04:31diversity.
00:04:32From the smallest insect to some of the largest mammals, they've all been shaped by flowers.
00:04:38But how did this happen, and why?
00:04:48The emergence of flowers is one of the biggest turning points in Earth's history.
00:04:55To understand how they changed our planet, you need to go right back to a prehistoric
00:05:00time.
00:05:04To the moment when the very first flower appeared.
00:05:12Up until around 140 million years ago, the Earth was very different.
00:05:18The animal kingdom was dominated by dinosaurs, and the separate continents we know today
00:05:25didn't exist.
00:05:28Instead, there had been a single huge continent, Pangaea.
00:05:40It's about as close as you can get to that ancient supercontinent.
00:05:45world.
00:05:46It's in the remote South Pacific, 1,500 kilometres from Australia, the island of New Caledonia.
00:06:08It looks like paradise, doesn't it?
00:06:12I mean, what makes New Caledonia just so interesting is that it's like a Noah's Ark of ancient plants.
00:06:18I mean, this little journey is going to take us back in time 140 million years.
00:06:32Because this part of the world is so isolated, it gives a glimpse of the plant world before
00:06:38flowers existed.
00:06:41Back then, the plant kingdom had two mighty rulers.
00:06:45One of them was the tall conifers, like this prehistoric species of pine.
00:06:56Look at these trees.
00:06:58Bizarre, aren't they?
00:07:00They're huge.
00:07:03Aricaria.
00:07:04Cook pine.
00:07:05Named after Captain Cook who explored this corner of the world.
00:07:10You know, pine trees are a family of conifers that are among the oldest in the world, so
00:07:14when the dinosaurs were around, these were nature's real giants.
00:07:20What made flowers so revolutionary was the limitations of the ancient plants that came before them.
00:07:30To reproduce, conifers like these relied on the vagaries of the wind.
00:07:41This is pollen, the male sex cells of conifers.
00:07:46Each grain has to be magnified a thousand times to really see it.
00:07:54The two air sacs, one on each side, catch the breeze.
00:08:00With luck, the male pollen will be blown to a female cone on a nearby tree.
00:08:06But for that to happen, each conifer needs vast amounts.
00:08:13It's very wasteful.
00:08:15Up to 10 billion grains have to be released by a single tree.
00:08:25The other big player back then was the ferns.
00:08:32Their method of reproduction was also restricting.
00:08:38Because ferns evolved in wet, swampy conditions, they needed water to transport their sex cells.
00:08:47And they use a surprising device.
00:08:51What they do is they release a sperm, which swims through the water in the mud to a nearby plant
00:08:57and fertilises its egg.
00:09:01Under a microscope you can see that by thrashing around, the male sperm cell can propel itself through water.
00:09:10It's able to swim for over two hours.
00:09:16It's amazing to think that a plant produces something like a human sperm.
00:09:23But the downside was that ferns had to live near water.
00:09:28It was hugely limiting.
00:09:32All this meant something was lacking in the world of Pangea.
00:09:38Diversity.
00:09:41There were few species of ferns and even fewer types of conifers.
00:09:48Just 1% of the range of plants we have today.
00:09:54And the animal kingdom was also limited.
00:10:02Scientists have found evidence of 700 different dinosaurs.
00:10:07It sounds a lot, but today there are over 5,500 species of mammals alone.
00:10:15There was little variety.
00:10:18It was a monotonous green world.
00:10:23And that's how life on the planet would have continued.
00:10:42140 million years ago, somewhere in Pangea, one plant of one species happened to chance on a new way of
00:10:52reproducing.
00:10:53And it would change the earth forever.
00:11:02I've pushed further into New Caledonia's jungle.
00:11:14The plant I'm after is really rare, which is why I've come so far.
00:11:21This is the only place that you find it.
00:11:23It's died out everywhere else.
00:11:26Mind you, amongst all of this, it's like a needle in a haystack.
00:11:37It looks like the leaves.
00:11:43Now what?
00:11:46Got them.
00:11:49I've come all the way around the world to find that.
00:11:53That is the Ambarella plant.
00:11:59Ambarella trichopoda is the closest living relative of the first flower to evolve.
00:12:05All flowers today have descended from its ancestor.
00:12:19Botanists believe it began when a single plant mutated to leaves that became petals,
00:12:25which instead of being green were probably white, like those of Ambarella.
00:12:31We now consider them to be the very first petals of the very first flower.
00:12:38To grasp the significance of this plant, you have to imagine a scene in some primordial forest where everything is
00:12:46just completely green.
00:12:48And then there's this flash of colour, a glint of white, some chance mutation.
00:12:54And the thing is, it's scurrying amongst it.
00:12:56It's a little beetle.
00:12:57Certainly not a bee, because bees haven't evolved yet, but a beetle spies this.
00:13:01A dash of white and scurries across to have a look.
00:13:04And then munchies on these little white birds that are just packed full of pollen.
00:13:11But not all the pollen is eaten.
00:13:14Some sticks to the beetle, and on it goes to other plants.
00:13:23Unknowingly, it's become a courier, delivering pollen from plant to plant, pollinating them as it looks for food.
00:13:38Plants had evolved an ingenious way of reproducing.
00:13:41They no longer relied on haphazard methods like the wind for conifers or water for ferns.
00:13:50Instead, it was reliable.
00:13:53Insects carried pollen directly to other plants.
00:13:57It was the birth of flowers.
00:14:04It's hard to grasp just how revolutionary this was.
00:14:07You know, I'm used to thinking of momentous changes in the earth as occurring through huge events.
00:14:13Vast continents colliding or mountains uplifting.
00:14:17But this, this was the tiniest of events.
00:14:20A subtle alteration of how a plant looked and a chance encounter with a curious beetle.
00:14:26And on the back of that, the world changed forever.
00:14:40Back then, the supercontinent of Pangaea was splitting up.
00:14:46Smaller continents were forming here.
00:14:51Creating countless new landscapes.
00:14:55With new climates and environments.
00:14:59Rising mountain ranges.
00:15:03And dry, inhospitable deserts.
00:15:08For conifers and ferns so dependent on wind and water.
00:15:13The new landscapes were impregnable.
00:15:17But for flowering plants, it was the chance they'd been waiting for.
00:15:22Because they are a powerful in-built advantage.
00:15:34This is a monkey puzzle tree.
00:15:37And like most conifers, monkey puzzles live for hundreds of years.
00:15:42And crucially, they don't reach sexual maturity until they're 40.
00:15:49Now, this is a campaign flower.
00:15:52Which in the shadow of this thing looks pretty puny.
00:15:56But the campaign flower has a last laugh.
00:15:58Because this, like most flowers, matures much quicker.
00:16:02In fact, the campaign flower can reproduce after just four months.
00:16:07It means that in the time that it takes this conifer to produce just one generation.
00:16:11The flowers can go through 120 generations.
00:16:19What's so fascinating is the impact that this has got on evolution.
00:16:22Because every time there's a new generation, there's a possibility of a genetic mutation.
00:16:28A mutation that might give a characteristic that helps survival.
00:16:32So the faster the life cycles, the more species can adapt to new environments.
00:16:38Which, of course, is crucial to our story.
00:16:53140 million years ago, these rapid life cycles helped flowers exploit the most hostile environments.
00:17:01Just like Tangkwa Karoo in South Africa.
00:17:09Because beneath this desert is a hidden carpet of flowers.
00:17:15Each year it rains for just two months.
00:17:20The plants only have this brief window to reproduce.
00:17:24So how do they ensure they're pollinated in time?
00:17:39The evolved colour.
00:17:52Each type of flower that you see is using colour in a struggle to get noticed by it.
00:17:57By insects.
00:17:58And there isn't much time.
00:18:00In a few weeks or days, the rains will be gone.
00:18:03And if these flowers aren't fertilised by then, then the plants will die.
00:18:07And the opportunity to reproduce will be lost.
00:18:12Hundreds of different flowers.
00:18:15Dozens of different colours.
00:18:16Whether it be orange gazanias, purple dewflowers, or the red balloon pea plant.
00:18:26And it wasn't random.
00:18:28Many used a different, specific colour to attract insects.
00:18:35They became targets, using insects to transfer the right pollen to the right plant, even over great distances.
00:18:47And flowers evolved a clever way to enhance this colour.
00:18:54To the naked eye, a petal looks smooth.
00:18:58But magnify it a thousand times and you can see its real structure.
00:19:10It's not a flat surface at all.
00:19:14Instead, the petal is made up of countless nodules.
00:19:20Each acts like a tiny prism, which reflects and diffracts light.
00:19:27It gives the petal an iridescence to attract passing insects.
00:19:42And in their use of colour, flowers went even further.
00:20:14It's a heck of a contraption, isn't it?
00:20:16A special camera to give you a kind of insects view of what a flower looks like.
00:20:26That's nice. Look at that.
00:20:28Insects and this camera can see a part of the light spectrum called ultraviolet.
00:20:35That's normally invisible to us humans.
00:20:50The camera reveals how flowers that appear plain to us
00:20:54look completely different to insects.
00:21:04And the markings are really important because they're like airport runway lights
00:21:08that guide the insect down onto the petals.
00:21:12Like neon signs that say, free food here.
00:21:26But once the flowers were pollinated, they still faced a big challenge.
00:21:32Because their offspring then had to make it through the rest of the year.
00:21:39Here in the Karoo, that could be ten months of drought.
00:21:44To survive, flowers perfected another trick which had a powerful impact on life on Earth.
00:21:53Seeds.
00:21:55Because seeds are this remarkable ability that we don't normally think about.
00:22:02These are seeds of the Kanna Indica flower.
00:22:06And this, this is an empty shotgun cartridge.
00:22:10I'm going to pack the seeds in where the lead pellets would have been.
00:22:14The grassže dedans呵 filing.
00:22:42The R it's got right through.
00:22:43Another big screen from getting jumped.
00:22:44The rifle is in which we don't know where we're headed the summer,
00:22:44It's gone right through.
00:22:44And the según things you could expect to see a sense of vielane under the ground
00:22:46Look at that.
00:22:49That looks perfectly intact.
00:22:53The story goes that during the Indian mutiny of the 19th century,
00:22:59soldiers used these seeds instead of lead shot.
00:23:09They're hard enough to be blasted out of a barrel and through wood.
00:23:17These seeds are so tough, in fact,
00:23:20that it's said that despite being fired from a gun,
00:23:23they can still germinate.
00:23:26Sounds unlikely, I know, though we'll see.
00:23:32But a tough shell wasn't all,
00:23:34because seeds from flowering plants developed a further evolutionary advantage
00:23:39that no other plant possessed.
00:23:49It all starts at the moment of pollination.
00:23:56Having been delivered by an insect,
00:23:58two cells from the pollen burrow deep into the flower's ovary.
00:24:04Here, one fertilises an egg to create an embryonic plant.
00:24:14But, and here's the clever bit,
00:24:17the second cell from the pollen does a completely different job.
00:24:22Instead of becoming a new plant,
00:24:24it grows into a food source for the fertilised egg.
00:24:28A kind of packed lunch.
00:24:31It's called double fertilisation.
00:24:35And it's unique to the seeds of flowers.
00:24:46It meant seeds could lie dormant for months or even years
00:24:49until conditions were right.
00:24:56As for my can of indica seeds,
00:24:59well, this is how they fared.
00:25:02Despite being blasted from a shotgun,
00:25:06four weeks later, here they are now,
00:25:10successfully germinating into a tiny flowering plant.
00:25:20By 100 million years ago,
00:25:23flowers were redrawing the global map of where plants could live.
00:25:30They were turning once infertile areas into oases of life.
00:25:42And it wasn't just about plants.
00:25:44Because these flower oases were now luring animals too.
00:25:50There was one ability above all
00:25:53that gave flowers the power to do this.
00:25:58Plants can do something unique
00:25:59that marks them out amongst all other living things on the planet.
00:26:03Their leaves can capture energy
00:26:06from our nearest star, the sun,
00:26:08and turn it into food.
00:26:14And the total amount of energy
00:26:16photosynthesis brings to the earth
00:26:19is staggering.
00:26:38I know this is a bit odd,
00:26:39but just imagine that this little scooter
00:26:42and all the fuel that it uses
00:26:43represents all the energy
00:26:45that the USA consumes in just one year.
00:26:50Now imagine that you take all the plants in the world,
00:26:53all the trees, flowers, and grasses.
00:26:57All the jungles, the forests, and savannas,
00:27:00and you add up the total energy
00:27:01harnessed by plants from the sun every year.
00:27:06It's not two scooters worth,
00:27:08or ten.
00:27:10It's all of this.
00:27:12Forty times the amount of energy
00:27:14consumed by America every year.
00:27:23It's 100 trillion watts of energy every year.
00:27:29Astonishing as this is,
00:27:31flowers took all this energy
00:27:33and went even further.
00:27:36An adaptation that would have
00:27:38enormous repercussions
00:27:39for the animal kingdom.
00:27:43They developed this ingenious method
00:27:45of making the sugars available
00:27:47to the pollinators.
00:27:48And if I take this syringe here
00:27:50and just slide it delicately in here,
00:27:54I can show you
00:27:55what they came up with.
00:28:02It's this really sweet-tasting liquid.
00:28:05Nectar, of course.
00:28:06One of the most energetic sources
00:28:08of food on the planet.
00:28:10And something animals found
00:28:11utterly irresistible.
00:28:15The nectar from this bird-of-paradise flower
00:28:18has three times the sugar concentration
00:28:20of Coca-Cola.
00:28:28Flowers were now pumping
00:28:29bite-sized packets of liquid energy
00:28:32into the food chain.
00:28:35And this began driving the evolution
00:28:37of entirely new insects.
00:28:43Just take a look at this.
00:28:46Isn't it beautiful?
00:28:48For me, this is one of the most
00:28:50incredible fossils ever found.
00:28:53I mean, it's such intricate detail.
00:28:55The material is amber.
00:28:57And inside it is a bee.
00:29:05It's a very primitive bee
00:29:07that got stuck in liquid tree resin,
00:29:10which then solidified
00:29:12and preserved the hapless insect.
00:29:19Bee fossils like these began appearing
00:29:22roughly 100 million years ago.
00:29:26And what they show
00:29:27is the incredible impact
00:29:29flowering plants
00:29:30were now having on evolution.
00:29:34What I love about this fossil
00:29:35is that it's like a snapshot
00:29:37of an ancient past
00:29:38just captured in time.
00:29:40And it makes you realise
00:29:42that there was a particular point
00:29:43when bees first arrived on Earth.
00:29:48Bees evolved from carnivorous wasps,
00:29:51which had turned their backs on meat
00:29:53in favour of pollen and nectar.
00:29:58As they evolved,
00:30:00their whole bodies
00:30:01became covered in hair
00:30:02to collect more pollen.
00:30:07They developed sophisticated compound eyes
00:30:10with hundreds of tiny lenses
00:30:13to spot the flowers.
00:30:17Inside were special cells
00:30:20to detect UV light.
00:30:24There are more types of early bees
00:30:26in South Africa
00:30:27than anywhere else in the world,
00:30:28so it's thought they originated here.
00:30:30And if you think about it,
00:30:32without the power of flowers,
00:30:34you'd have no bees at all.
00:30:39But by creating insects
00:30:41to pollinate them,
00:30:42the flowers introduced
00:30:43a new problem for themselves.
00:30:48There was a risk
00:30:49that after an insect
00:30:50picked up pollen
00:30:51from a flower,
00:30:52it would then travel
00:30:53onto a different species of flower
00:30:55and fail to fertilise it.
00:30:58The pollen would be wasted.
00:31:02The solution of flowers
00:31:04was inspired.
00:31:08Down under these cliffs
00:31:10on the South African coast,
00:31:11you can see what they came up with.
00:31:17This lovely pink flower
00:31:18is Orpheum frutescens.
00:31:22Which flourishes here
00:31:23in these salty conditions
00:31:24near the sea.
00:31:25But what's truly amazing
00:31:27about this plant
00:31:28is that it struck up
00:31:29this exclusive relationship
00:31:31with a particular bee.
00:31:34Orpheum flowers
00:31:35don't contain nectar.
00:31:36The payment they provide
00:31:38is pollen.
00:31:40But strangely,
00:31:41they keep it locked up.
00:31:43special twisted stamens
00:31:45special twisted stamens
00:31:45stop it being stolen
00:31:46by visiting insects.
00:31:48All that is
00:31:50except one.
00:31:52The female carpenter bee.
00:31:54Only she
00:31:55has the key.
00:31:59Let me show you
00:32:00what the bee has to do
00:32:01using these
00:32:02tuning forks here.
00:32:04When the bee
00:32:05lands on the flower,
00:32:06it changes the rate
00:32:08at which it beats its wings
00:32:09to just the right frequency.
00:32:11From this note
00:32:15to this one.
00:32:19Middle C.
00:32:21And it's these
00:32:23vibrations that are the key.
00:32:25Unlocking the stamens
00:32:26which open up at the top
00:32:27here
00:32:28and just
00:32:29shower the bee
00:32:30with pollen.
00:32:33Ah, look at that.
00:32:35Look at the amount
00:32:36of yellow pollen
00:32:37on there.
00:32:38Fantastic.
00:32:43Now watch the bee
00:32:44do the same
00:32:45hitting the middle
00:32:47C note
00:32:49with the beat
00:32:50of its wings
00:32:53and unlocking
00:32:54the pollen.
00:32:57No other insect
00:32:59does this.
00:33:00It's incredible,
00:33:01isn't it?
00:33:01One single
00:33:02species of flower
00:33:03and one particular
00:33:04type of bee
00:33:05have evolved
00:33:06together
00:33:07to give this
00:33:07intimate partnership.
00:33:13It ensured
00:33:14that a flower's
00:33:14pollen was
00:33:15successfully taken
00:33:16to a plant
00:33:17of the same
00:33:18species.
00:33:22But these
00:33:22increasingly
00:33:23tight relationships
00:33:24between insects
00:33:25and flowers
00:33:26had another
00:33:26impact on life
00:33:27on earth.
00:33:29Because they
00:33:29led to tighter
00:33:30and more
00:33:31isolated populations.
00:33:33That started
00:33:33creating gaps
00:33:35in the overall
00:33:35ecosystem.
00:33:37This in turn
00:33:37encouraged new
00:33:39species to evolve,
00:33:41filling in
00:33:41those spaces.
00:33:45Flowers were now
00:33:46driving a huge
00:33:47increase in the
00:33:48diversity of life.
00:33:51And they were
00:33:52fueling this increase
00:33:53by pumping nectar
00:33:54into the food chain.
00:34:02The insects,
00:34:04bees,
00:34:04butterflies and moths,
00:34:06such as the
00:34:07hawk moth,
00:34:08were eating it
00:34:09with long,
00:34:09probing tongues.
00:34:13There were new
00:34:14species of birds,
00:34:16like the
00:34:16calliope hummingbird
00:34:18with beaks
00:34:18perfect for
00:34:20trumpet-shaped
00:34:20flowers.
00:34:22And predators,
00:34:24such as these
00:34:25toucans,
00:34:26that ate the
00:34:27pollinators.
00:34:29Between 120 and
00:34:31about 90 million
00:34:32years ago,
00:34:33all thanks to
00:34:35flowering plants,
00:34:36evolution had
00:34:37entered the most
00:34:37explosive phase in
00:34:39the earth's history.
00:34:41MUSIC
00:34:52By now,
00:34:53Pangea had split up,
00:34:55creating the
00:34:56continent so
00:34:57familiar to us
00:34:58today.
00:34:59And flowers
00:35:00dominated them.
00:35:02They'd conquered
00:35:03the ancient
00:35:04conifers and ferns
00:35:05and covered
00:35:06half the earth.
00:35:13But it wasn't
00:35:14just life they
00:35:15were changing,
00:35:17because they
00:35:17started altering
00:35:18the very shape
00:35:19of the planet
00:35:20itself.
00:35:28This is
00:35:29Ha Long Bay
00:35:30in Vietnam.
00:35:32I'm here
00:35:33because it's
00:35:34evidence of
00:35:34how flowers
00:35:35unleashed some
00:35:36of the most
00:35:36powerful
00:35:37forces on
00:35:38earth.
00:35:40This whole
00:35:41landscape just
00:35:42dwarfs you.
00:35:44You can see
00:35:45these pinnacles
00:35:46of limestone
00:35:47just soaring
00:35:48upwards.
00:35:48Limestone that
00:35:49you get all
00:35:49over Vietnam.
00:35:50And it gives
00:35:51this really
00:35:52distinctive,
00:35:52even iconic
00:35:53landscape called
00:35:54karst.
00:35:57I think it's
00:35:57when you look
00:35:58at things as
00:35:59huge as that,
00:36:00you look for
00:36:00huge geological
00:36:02processes to
00:36:03create them.
00:36:03But it's not
00:36:05always the case.
00:36:10that's because
00:36:1190 million years
00:36:12ago, flowers
00:36:14began to build
00:36:14an empire
00:36:15across the planet
00:36:19in a totally
00:36:20unexpected way.
00:36:26They did it by
00:36:28creating vast
00:36:29tropical rainforests.
00:36:44almost all the trees
00:36:46are really giant
00:36:47flowering plants.
00:36:49You can see one
00:36:50here and flower.
00:36:52And all the trees
00:36:54are doing one thing.
00:37:02Breathe out on a
00:37:03piece of glass
00:37:04and it's pretty
00:37:04obvious that
00:37:05there's moisture
00:37:05in your breath.
00:37:07And in a funny
00:37:07kind of way,
00:37:08plants are
00:37:09breathing out
00:37:09moister too.
00:37:10It's just much
00:37:11harder to see.
00:37:15But take a look
00:37:16at this.
00:37:17If I tie a clear
00:37:18plastic bag
00:37:19over this big leaf
00:37:21then we should
00:37:22be able to
00:37:22actually see
00:37:23the plant
00:37:25breathing away.
00:37:27And all we
00:37:28need to do
00:37:28now is
00:37:30wait a couple
00:37:31of hours.
00:37:40Look how much
00:37:41moisture this
00:37:41single banana leaf
00:37:43produces.
00:37:47It's losing
00:37:48water or
00:37:49transpiring
00:37:50through tiny
00:37:51pores in the
00:37:52leaf called
00:37:53stomata.
00:37:58Close up
00:37:59you can see
00:37:59the veins
00:38:00of the leaf
00:38:01which transport
00:38:02water around
00:38:02the plant.
00:38:05Leaves of
00:38:06flowering plants
00:38:07contain four
00:38:08times more
00:38:08veins than
00:38:09other plants.
00:38:18because they
00:38:18share the
00:38:19same type
00:38:19of special
00:38:20vein leaves
00:38:21trees like
00:38:21these act
00:38:22as kind
00:38:22of giant
00:38:23water pumps
00:38:24drawing moisture
00:38:25up from the
00:38:26soil and
00:38:26pumping it
00:38:27out into
00:38:27the atmosphere.
00:38:28Some of
00:38:29these trees
00:38:29chuck out
00:38:30five tonnes
00:38:31of water
00:38:32every day.
00:38:42all this
00:38:43transpiration
00:38:44meant that
00:38:4590 million
00:38:45years ago
00:38:46flowering plants
00:38:47were creating
00:38:48more clouds
00:38:54which led
00:38:55to more rain
00:39:01water that
00:39:02when it fell
00:39:02was then
00:39:03drawn up
00:39:04from the
00:39:04forest floor
00:39:05by the
00:39:05same trees
00:39:07forming a
00:39:08self-sustaining
00:39:08cycle of
00:39:09almost perpetual
00:39:10rainfall.
00:39:14In fact
00:39:1580% of the
00:39:17water in the
00:39:17rainforests came
00:39:19from the
00:39:19flowering plants
00:39:20themselves.
00:39:23In this new
00:39:25age of rain
00:39:26water became
00:39:27an ever
00:39:27powerful
00:39:28sculpting
00:39:29force.
00:39:33And today
00:39:34you can see
00:39:35its effects
00:39:36in an
00:39:36astonishing
00:39:37hidden world.
00:39:53Deep
00:39:54beneath the
00:39:55rainforest
00:39:55in central
00:39:56Vietnam
00:39:57are the
00:39:58caverns of
00:39:58Hang Song
00:39:59Dung.
00:40:01We are the
00:40:02first British
00:40:03film crew
00:40:03to explore
00:40:04them.
00:40:11Hang Song
00:40:12Dung is the
00:40:13largest cave
00:40:14passage ever
00:40:15discovered
00:40:16anywhere on
00:40:17earth.
00:40:43this single
00:40:45carbon is nearly
00:40:47two kilometres long, all carved from solid rock by nothing more than water.
00:41:02All of which has trickled down from a single source, the vast jungle above.
00:41:11It's a relentless force that has carved out a dozen enormous caverns.
00:41:19An underground monument to the power of flowering plants.
00:41:33And deep in this labyrinth, this wood, for me, is perhaps the greatest of all the wonders of the plant
00:41:39world.
00:41:51Here, at the heart of the cave, a whole rain forest.
00:42:07Where the roof has collapsed, flowering plants have made their home.
00:42:16200 metres below ground level.
00:42:25It is like a lost world.
00:42:27And the thing is, just a few minutes ago, there was me in a kind of cool, dark cave,
00:42:32and then ejected into this.
00:42:34This place was streaming sunlight.
00:42:37Hot and sticky rain forest.
00:42:42And where there's water and light, flowers have produced life.
00:42:59Plants such as this banana flower thrive, which in turn attracts butterflies and other animals.
00:43:08It's a thriving ecosystem here.
00:43:11And the whole thing is fed, really, everything, this whole food chain is fed by the flowering plants.
00:43:23Flowering plants have created a small but perfect version of the rain forest above.
00:43:36Look at that mist.
00:43:39There's a whole weird microclimate in here.
00:43:42Clouds of moisture envelop everything.
00:43:45And the plants just soak up that moisture, just draw it up and then pass it out.
00:43:51So that kind of cycle of transpiration that we see on a big scale up in the tropical forest
00:43:55is kind of captured in miniature down here.
00:44:04Caves formed under all the world's great rain forests.
00:44:09And this extra water even began to transform the global climate.
00:44:16As water evaporates, it absorbs heat and cools the planet.
00:44:21The Amazon rainforest alone keeps its whole region five degrees colder.
00:44:28Across the planet, water injected into the water cycle was eroding deep canyons,
00:44:36carving high mountains,
00:44:38and sculpting the karst towers so iconic of Asia.
00:44:47It's extraordinary, isn't it?
00:44:49Especially when you think that all this comes not from huge forces deep underground,
00:44:55but in part from tiny changes on the leaves of flowering plants.
00:45:0665 million years ago was the age of the rainforests.
00:45:13They'd spread from the equator to cover most of the earth.
00:45:18It meant three quarters of all plants were now flowers.
00:45:23A rich, lush home for millions of new animals.
00:45:29The dominance of the flowering plants seemed unassailable.
00:45:35But it was not to last.
00:45:43A 10-kilometre-wide asteroid coming from deep space was on a collision course.
00:45:58It hit the earth with a force of a billion Hiroshima bombs.
00:46:0470 billion tons of pulverized rock were blasted into a low orbit.
00:46:14Scientists called it ejecta.
00:46:16And travelling at supersonic speeds,
00:46:19its friction with the atmosphere heated the earth up
00:46:22by over 200 degrees Celsius.
00:46:27It spontaneously triggered fires across the land.
00:46:37It was one of the worst mass extinctions in the history of the earth.
00:46:45And famously killed off the dinosaurs.
00:46:56But less well-known is the immediate impact on plants.
00:47:04Scientists believe that for them,
00:47:06the effect of the asteroid was also devastating.
00:47:12Not only were there fires,
00:47:15but the ejecta created clouds of nitric and sulphur dioxide,
00:47:21which fell as acid rain,
00:47:27destroying plants from the roots up.
00:47:48I think it's really hard to imagine what the most recent and powerful extinction event must have been like,
00:47:52but perhaps the closest you can get to it
00:47:55is like a newly erupted volcano like here in White Island, New Zealand.
00:48:02I think it's just a desolation, really.
00:48:05The bleakness, that sense that life's just been obliterated.
00:48:14For plants, the aftermath of the asteroid impact must have been similar.
00:48:19Here on White Island, vegetation has been incinerated by successive eruptions.
00:48:26And the volcanic fumes create acid rain, just like after the asteroid.
00:48:32For flowering plants, it was a disaster.
00:48:35That close, almost inseparable relationship with insects was now their Achilles' heel.
00:48:41Because even if a flowering plant had survived the initial calamity,
00:48:45it needed a specific animal to pollinate it.
00:48:48And often, it's simply been wiped out.
00:49:01But flowers weren't beaten yet.
00:49:05All those evolutionary devices that had allowed them to thrive on a hostile planet in the first place
00:49:11now became their ultimate tools for survival.
00:49:17Coloured petals to attract a few surviving pollinators.
00:49:22Nectar to repay them in desperate times.
00:49:29Above all, flowers could rely on those superb survival capsules.
00:49:34It could have been purpose-built for just such an apocalypse.
00:49:39Seeds.
00:49:51Now, following the asteroid impact, seeds helped flowers to recolonise the Earth.
00:49:58And as they did so, once again, flowers formed an inseparable relationship with animals.
00:50:06The dinosaurs had gone, but another type of animal had replaced them.
00:50:12Mammals.
00:50:18This time, flowers use mammals to help them distribute their seeds.
00:50:32Here in Thailand, this whole floating market celebrates the clever evolutionary device flowers came up with.
00:50:42More sophisticated flowers developed a really sneaky way of spreading the seeds.
00:50:47The method, it didn't just disperse it meters, but kilometers.
00:50:52And to do that, they again harnessed the hunger of animals.
00:50:55They developed fruit.
00:51:03What is that?
00:51:05Taurian.
00:51:06This is Taurian.
00:51:07I cast, you cast.
00:51:09OK, yeah.
00:51:11You can't come to Asia without trying the smelliest, most notorious fruit on Earth.
00:51:18Beautiful.
00:51:20I hope it tastes better than it smells, though.
00:51:24Ah, there's a smell.
00:51:26There's a lot of seeds in there.
00:51:29And then there's flesh.
00:51:32Textures.
00:51:37They're all laughing.
00:51:38They're laughing.
00:51:40It's like an off avocado, really.
00:51:44I think that's what they call an acquired taste.
00:51:48The botanical definition of a fruit is that it must actually develop from the flour itself.
00:51:56The fleshy coating was once the ovary as it grew around the maturing seeds.
00:52:02It's lovely.
00:52:04It's incredibly sweet.
00:52:05It's very subtle.
00:52:08Isn't that great?
00:52:09Isn't that great?
00:52:09Just the way all of them hide this inside, this little seed.
00:52:15You can see why some warm-blooded mammal or bird would want to eat this.
00:52:19It's just packed with nutrition.
00:52:21Now, of course, as you do that, you swallow the seed.
00:52:28And then later on, you pass that out somewhere, miles away, dumped in some little dollop of manure.
00:52:35And that's really the point of all of this different types of food, all this diversity,
00:52:39is designed to attract animals to eat it.
00:52:55Fruit is one of the most remarkable transformations in nature.
00:53:02What begins is an advertisement for an insect, a flower,
00:53:08becomes a protective covering for the seeds inside.
00:53:13And then a final burst swells into the juicy flesh of a fruit.
00:53:3655 million years ago, one group of early mammals was evolving that relied almost entirely on fruit.
00:53:45In fact, without it, they'd probably never have existed.
00:53:55It was an animal which would directly link flowers to our human story.
00:54:04They live here, in Thailand's Khao Sok National Park.
00:54:09Somewhere in these trees, there are primates.
00:54:16I'm sure that up there, you see the trees, just the branches moving, but trying to pinpoint the actual gibbons
00:54:23is really tricky.
00:54:27Oh, there's one.
00:54:30Do you see it?
00:54:31It's kind of silhouetted in the branches just up there.
00:54:36I'm sure.
00:54:37Yeah, it's moving.
00:54:40My first gibbon.
00:54:43The primates, lemurs, monkeys and apes, evolved an inseparable partnership with the fruit from flowers.
00:54:51And it determined their whole anatomy.
00:54:55Primates have got the perfect tools for reaching fruit.
00:54:58They've got these really strong hands, which along with their powerful chest and shoulder muscles,
00:55:05allow them to get up into the trees.
00:55:07All these are important traits that we human primates have inherited today.
00:55:15And all came from the need for the first primates to reach the fruit of flowering plants.
00:55:26Norberto Asensio is a primatologist.
00:55:30He studies the crucial role fruit plays in the diet of monkeys.
00:55:36For most primates, fruit is important.
00:55:39It's part of their diet, somewhat.
00:55:42Is it the core of the diet, the essential core, do you think?
00:55:45I would say so.
00:55:46I would say so that most of the primates will have 70 to 90% of their diet on fruit.
00:55:55But back then, flowering plants created a problem for themselves.
00:56:01Primates were so hungry for fruit, they would pick it long before the seeds inside were mature.
00:56:10It meant seeds were being wasted.
00:56:15So flowers came up with a solution.
00:56:25When fruit was ripe, they made it sweet, juicy and brightly coloured.
00:56:31It was a colour-coded time delay.
00:56:34And it encouraged primates to take only fruit that was fully mature.
00:56:43Norberto studies how this colour-coding drove changes in our ancient ancestors.
00:56:50Before now, primates, like all mammals, were colour-blind.
00:56:56This made spotting ripe fruit difficult, as I'm about to find out.
00:57:01Let's do an experiment.
00:57:03Here you have glasses that are going to turn you into a simple mammal.
00:57:10Let's see.
00:57:11Oh, gosh!
00:57:14The glasses simulate colour blindness by removing red from the picture.
00:57:20I can kind of tell a difference in contrast between some of them.
00:57:25That's got a very funny shade of bluishness.
00:57:28The interesting ones are these reds.
00:57:30These reds don't...
00:57:31I mean, I know they're red, but they just don't seem red at all.
00:57:34It's just...
00:57:35Overall, it's just got a kind of very...
00:57:38..almost bland greyness to it.
00:57:45For primates to perceive red,
00:57:48they had to evolve a more sophisticated vision system.
00:57:53In the retina are special photoreceptor cells that detect colour, called cones.
00:58:01There are 150,000 per square millimetre.
00:58:06Early mammals only had two types of cone.
00:58:09One for green and one for blue.
00:58:13It meant they were colour blind.
00:58:16But primates evolved a third type.
00:58:19It was sensitive to red.
00:58:24Now they could spot ripe fruit.
00:58:27Colour vision helped give primates the advantage,
00:58:31kick-starting the evolutionary journey that resulted in us humans.
00:58:37That's why we have colour vision now,
00:58:39and we have this wonderful rainbow of colours that we can see now and enjoy it.
00:58:50Fruit drove the evolution of so many of the traits of our ancient ancestors,
00:58:54but this symphony, the ability to see if fruit was ready to eat or not,
00:58:59had given primates, perhaps for the first time on our planet,
00:59:03this capacity to see in full, glorious technicolour.
00:59:08You know, it's something that I think we just take for granted.
00:59:20It's something that I think we just take for granted.
00:59:20Since they'd evolved 140 million years ago,
00:59:24flowers had transformed our planet.
00:59:26They'd come to dominate the plant kingdom, sculpting the earth itself.
00:59:34Above all, flowers drove the evolution of animals,
00:59:39especially primates, shaping our human evolution.
00:59:56It seems to me that we're rather animal-centric,
01:00:00that by being members of the animal kingdom ourselves,
01:00:03we somehow see them as the thing that's at the heart of driving changes to life on earth.
01:00:08But I don't think that's true.
01:00:11Most of the big changes to life on the planet are being brought around by flowers.
01:00:16They're the ones that are more manipulative, more inventive,
01:00:20more powerful than any of the animals that they're interacting with.
01:00:23Most animals are only here because of flowers, including us.
01:00:29It's an intriguing thought for next time you're out doing the roses.
01:00:35Next, we reveal the epic battle
01:00:38between the forests and their greatest challenger.
01:00:41A new type of plant, the grasses.
01:00:44It was a conflict that would set the world on fire.
01:00:49The victor would force our ancient ape ancestors
01:00:52out of the forests and into the savannah.
01:00:56And go on to trigger the birth of human civilisation.