- 4 weeks ago
Category
✨
PeopleTranscript
00:00:08I spent most of my life trying to understand the forces that shaped our planet and as a
00:00:13geologist it always seemed to me that rocks were right at the heart of things but now
00:00:23I'm discovering it's not only volcanoes and colliding continents that have driven
00:00:28the Earth's greatest changes because at crucial moments in its history another
00:00:35force has helped create the planet we live on
00:00:39plants
00:00:43it's a whole new story about the earth revealing how from its earliest history
00:00:49plants 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 allowing life to colonize the land
00:01:30but the next chapter will take us even further because a powerful newcomer to the plant world was
00:01:37on its way it would conquer every corner of the planet
00:01:42it would shape the very surface of the earth
00:01:46and 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 kilometers
00:02:29this is the temple of Angkor Wat
00:02:32in Cambodia
00:02:36I'm here to witness the importance
00:02:39of one of the most powerful symbols known to humankind
00:02:45a symbol central to an ancient Buddhist ceremony
00:02:53flowers
00:03:01you see lotus flowers and jasmine just arranged beautifully up there
00:03:07the 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 from one religion
00:03:32flowers are central to cultures throughout the world
00:03:37they're deeply woven into all our lives
00:03:40the earth as the berks of heaven
00:04:09they're deeplyingers
00:04:10and this is just one werd of timp
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 time.
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.
00:05:23And the separate continents we know today didn't exist.
00:05:28Instead, there had been a single huge continent, Pangea.
00:05:39I'm heading for a place that's about as close as you can get to that ancient supercontinent.
00:05:51island of New Caledonia.
00:06:09Looks 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 flowers 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, Cooke pine, named after Captain Cooke 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.
00:07:14So when 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, up to 10 billion grains have to be released by a single tree.
00:08:26The 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 and 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.
00:09:27It was hugely limiting.
00:09:32All this meant something was lacking in the world of Pangea.
00:09:39Diversity.
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.
00:10:08It 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.
00:11:20This 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.
00:11:37Oh, what am I...
00:11:39That looks like the leaves.
00:11:44Look at that wood.
00:11:46I've got 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, till leaves it became petals, which instead of being green, were
00:12:27probably 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.
00:12:59But a beetle spies this dash of white and scurries across to have a look.
00:13:03And then munchies on these little white buds that are just packed full of pollen.
00:13:11But not all the pollen is eaten.
00:13:14Some sticks to the beetle.
00:13:17And on it goes to other plants.
00:13:23Unknowingly, it's become a courier, delivering pollen from plant to plant.
00:13:29Pollinating them as it looks for food.
00:13:38Plants had evolved an ingenious way of reproducing.
00:13:42They 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.
00:14:56With 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, the new landscapes were impregnable.
00:15:17But for flowering plants, it was the chance they'd been waiting for.
00:15:23Because they had 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 forty.
00:15:49Now, this is a campion flower.
00:15:52Which in the shadow of this thing looks pretty puny.
00:15:56But the campion flower has a last laugh.
00:15:58Because this, like most flowers, matures much quicker.
00:16:02In fact, the campion 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.
00:16:23Because 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.
00:16:33So the faster the life cycles, the more species can adapt to new environments.
00:16:38Which, of course, is crucial to our story.
00:16:53One hundred and forty million years ago, these rapid life cycles help 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.
00:17:25So how do they ensure they're pollinated in time?
00:17:39They evolved colour.
00:17:42They evolved colour.
00:17:55And a struggle to get noticed by insects.
00:17:59And 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, dozens of different colours.
00:18:17Whether 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.
00:18:41Even 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.
00:18:57But 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.
00:20:28That's nice. Look at that.
00:20:29Insects.
00:20:29And 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 look completely different to insects.
00:21:04And the markings are really important because they're like airport runway lights that guide the insect down onto the petals.
00:21:13Like 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.
00:21:38Here 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.
00:21:56Because seeds have this remarkable ability that we don't normally think about.
00:22:03These are seeds of the can of 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.
00:22:41Oh, it's gone right through.
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, that it's said that despite being fired from a gun, they can still
00:23:24germinate.
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 that no other plant possessed.
00:23:49It all starts at the moment of pollination.
00:23:56Having been delivered by an insect, two cells from the pollen burrow deep into the flower's ovary.
00:24:04Here, one fertilises an egg to create an embryonic plant.
00:24:15But, and here's the clever bit, the second cell from the pollen does a completely different job.
00:24:22Instead of becoming a new plant, it 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.
00:24:45It meant seeds could lie dormant for months or even years until conditions were right.
00:24:56As for my can of indica seeds, well 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.
00:25:15Remarkable.
00:25:21By 100 million years ago, flowers were redrawing the global map of where plants could live.
00:25:30They were turning once infertile areas into oases of life.
00:25:41And it wasn't just about plants.
00:25:44Because these flower oases were now luring animals too.
00:25:51There was one ability above all that gave flowers the power to do this.
00:25:58Plants can do something unique that marks them out amongst all other living things on the planet.
00:26:04Their leaves can capture energy from our nearest star, the sun, and turn it into food.
00:26:14And the total amount of energy photosynthesis brings to the Earth is staggering.
00:26:38I know this is a bit odd, but just imagine that this little scooter and all the fuel that it
00:26:43uses represents all the energy that the USA consumes in just one year.
00:26:50Now imagine that you take all the plants in the world.
00:26:53Now imagine that you take all the plants in the world.
00:26:53All the trees, flowers, and the grasses.
00:26:57All the jungles of forests and savannas, and you add up the total energy harnessed by plants from the sun
00:27:03every year.
00:27:06It's not two scooters worth, or ten.
00:27:10It's all of this.
00:27:12Forty times the amount of energy consumed by America every year.
00:27:22It's 100 trillion watts of energy every year.
00:27:29Astonishing as this is, flowers took all this energy and went even further.
00:27:36An adaptation that would have enormous repercussions for the animal kingdom.
00:27:43They developed this ingenious method of making the sugars available to the pollinators.
00:27:48And if I take this syringe here and just slide it delicately in here,
00:27:54I can show you what they came up with.
00:28:02It's this really sweet tasting liquid.
00:28:05Nectar of course.
00:28:07One of the most energetic sources of food on the planet.
00:28:09And something animals found utterly irresistible.
00:28:15The nectar from this bird of paradise flower has three times the sugar concentration of Coca-Cola.
00:28:27Flowers were now pumping bite-sized packets of liquid energy into the food chain.
00:28:35And this began driving the evolution of entirely new insects.
00:28:44Just take a look at this.
00:28:46Isn't it beautiful?
00:28:49For me this is one of the most incredible fossils ever found.
00:28:53I mean it's such an intricate detail.
00:28:55The material is amber.
00:28:57And inside it is a bee.
00:29:05It's a very primitive bee that got stuck in liquid tree resin.
00:29:10Which then solidified and preserved the hapless insect.
00:29:19Bee fossils like these began appearing roughly 100 million years ago.
00:29:25And what they show is the incredible impact flowering plants were now having on evolution.
00:29:34What I love about this fossil is that it's like a snapshot of an ancient past just captured in time.
00:29:40And it makes you realise that there was a particular point when bees first arrived on Earth.
00:29:48Bees evolved from carnivorous wasps which had turned their backs on meat in favour of pollen and nectar.
00:29:59As they evolved their whole bodies became covered in hair to collect more pollen.
00:30:07They developed sophisticated compound eyes with hundreds of tiny lenses to spot the flowers.
00:30:18Inside were special cells to detect UV light.
00:30:24There are more types of early bees in South Africa than anywhere else in the world so it's thought they
00:30:29originated here.
00:30:30And if you think about it, without the power of flowers, you'd have no bees at all.
00:30:39But by creating insects to pollinate them, the flowers introduced a new problem for themselves.
00:30:48There was a risk that after an insect picked up pollen from a flower,
00:30:52it would then travel onto a different species of flower and fail to fertilise it.
00:30:58The pollen would be wasted.
00:31:02The solution of flowers was inspired.
00:31:08Down under these cliffs on the South African coast, you can see what they came up with.
00:31:17This lovely pink flower is Orpheum frutescens, which flourishes here in these salty conditions near the sea.
00:31:25But what's truly amazing about this plant is that it struck up this exclusive relationship with a particular bee.
00:31:34Orpheum flowers don't contain nectar.
00:31:37The payment they provide is pollen.
00:31:40But strangely, they keep it locked up.
00:31:43Special twisted stamens stop it being stolen by visiting insects.
00:31:49All that is, except one.
00:31:52The female carpenter bee.
00:31:55Only she has the key.
00:31:59Let me show you what the bee has to do using these tuning forks here.
00:32:05When the bee lands on the flower, it changes the rate at which it beats its wings to just the
00:32:10right frequency.
00:32:11From this note,
00:32:15to this one.
00:32:19Middle C.
00:32:21And it's these vibrations that are the key.
00:32:25Unlocking the stamens, which open up at the top here and just shower the bee with pollen.
00:32:33Ah, look at that.
00:32:35Look at the amount of yellow pollen on there. Fantastic.
00:32:43Now watch the bee do the same, hitting the middle C note with the beat of its wings and unlocking
00:32:54the pollen.
00:32:57No other insect does this.
00:33:00It's incredible, isn't it?
00:33:01One single species of flower, one particular type of bee, have evolved together to give this intimate partnership.
00:33:13It ensured that a flower's pollen was successfully taken to a plant of the same species.
00:33:21But these increasingly tight relationships between insects and flowers had another impact on life on Earth.
00:33:28Because they led to tighter and more isolated populations, that started creating gaps in the overall ecosystem.
00:33:36This in turn, encouraged new species to evolve, filling in those spaces.
00:33:45Flowers were now driving a huge increase in the diversity of life.
00:33:51And they were fueling this increase by pumping nectar into the food chain.
00:34:02The insects, bees, butterflies and moths, such as the hawk moth, were eating it with long probing tongues.
00:34:13There were new species of birds, like the calliope hummingbird with beaks perfect for trumpet shaped flowers.
00:34:23And predators, such as these toucans, that ate the pollinators.
00:34:29Between 120 and about 90 million years ago, all thanks to flowering plants,
00:34:36evolution had entered the most explosive phase in the Earth's history.
00:34:52By now, Pangaea had split up, creating the continent so familiar to us today.
00:34:59And flowers dominated them.
00:35:02They had conquered the ancient conifers and ferns and covered half the Earth.
00:35:13But it wasn't just life they were changing.
00:35:16Because they started altering the very shape of the planet itself.
00:35:28This is Ha Long Bay in Vietnam.
00:35:32I'm here because it's evidence of how flowers unleashed some of the most powerful forces on Earth.
00:35:41This whole landscape just dwarfs you.
00:35:44You can see these pinnacles of limestone just soaring upwards.
00:35:48Limestone that you get all over Vietnam.
00:35:50And it gives this really distinctive, even iconic landscape called karst.
00:35:57I think it's when you look at things as huge as that, you look for huge geological processes to create
00:36:03them.
00:36:03But, you know, it's not always the case.
00:36:10That's because 90 million years ago, flowers began to build an empire across the planet.
00:36:19In a totally unexpected way.
00:36:26They did it by creating vast tropical rainforests.
00:36:44Almost all the trees are really giant flowering plants.
00:36:49You can see one here and flower.
00:36:52And all the trees are doing one thing.
00:37:02Breathe out on a piece of glass and it's pretty obvious that there's moisture in your breath.
00:37:07And in a funny kind of way, plants are breathing out moisture too.
00:37:10It's just much harder to see.
00:37:15But take a look at this.
00:37:17If I tie a clear plastic bag over this big leaf,
00:37:21then we should be able to actually see the plant breathing away.
00:37:27And all we need to do now is wait a couple of hours.
00:37:40Look how much moisture this single banana leaf produces.
00:37:47It's losing water or transpiring through tiny pores in the leaf called stomata.
00:37:58Close up, you can see the veins of the leaf which transport water around the plant.
00:38:05Leaves of flowering plants contain four times more veins than other plants.
00:38:18Because they share the same type of special vein leaves, trees like these act as kind of giant water pumps,
00:38:24drawing moisture up from the soil and pumping it out into the atmosphere.
00:38:28Some of these trees chuck out five tonnes of water every day.
00:38:42All this transpiration meant that 90 million years ago,
00:38:47flowering plants were creating more clouds.
00:38:54Which led to more rain.
00:39:01Water that, when it fell, was then drawn up from the forest floor by the same trees.
00:39:07Forming a self-sustaining cycle of almost perpetual rainfall.
00:39:14In fact, 80% of the water in the rainforests came from the flowering plants themselves.
00:39:23In this new age of rain, water became an ever-powerful sculpting force.
00:39:33And today, you can see its effects in an astonishing hidden world.
00:39:54Deep beneath the rainforest in central Vietnam are the caverns of Hang Song Dung.
00:40:01We are the first British film crew to explore them.
00:40:11Hang Song Dung is the largest cave passage ever discovered.
00:40:16Anywhere on Earth.
00:40:18No one clear information,
00:40:44This single carbon is nearly 2km of earth.
00:40:50all carved from solid rock by nothing more than water.
00:41:02All of which has trickled down from a single source,
00:41:06the 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,
00:41:37is perhaps the greatest of all the wonders of the plant world.
00:41:51Here, at the heart of the cave, a whole rain forest.
00:42:08Where the roof has collapsed, flowering plants have made their home.
00:42:17200 metres below ground level.
00:42:25It is, like, a lost world.
00:42:27And the thing is, just a few minutes ago,
00:42:29there was me in a kind of cool, dark cave,
00:42:32and then ejected into this.
00:42:34Yes, this 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,
00:43:02which 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.
00:43:14This whole food chain is fed by the flowering plants.
00:43:23Flowering plants have created a small but perfect version
00:43:27of 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,
00:43:48just draw it up and then pass it out.
00:43:51So that kind of cycle of transpiration that we see on a big scale
00:43:54up in the tropical forest is 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.
00:44:17As 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
00:44:32was eroding deep canyons, carving 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 tonnes of pulverised rock were blasted into a low orbit.
00:46:14Scientists called it ejecta.
00:46:17And 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.
00:46:57But 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.
00:47:22which fell as acid rain,
00:47:27destroying plants from the roots up.
00:47:48It'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 is like a newly erupted volcano,
00:47:56like 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.
00:48:20Here 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.
00:48:40Because even if a flowering plant had survived the initial calamity,
00:48:45it needed a specific animal to pollinate it.
00:48:48And often, they'd 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 the 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 help 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.
00:50:47This method, it didn't just disperse at metres, but kilometres.
00:50:52And to do that, they again harnessed the hunger of animals.
00:50:55They developed fruit.
00:51:03What is that?
00:51:05Dorian.
00:51:06This is Dorian.
00:51:08OK, yeah.
00:51:11You can't come to Asia without trying the smelliest, most notorious fruit on Earth.
00:51:18Beautiful.
00:51:21I hope it tastes better than it smells, though.
00:51:25Ah.
00:51:25There's the 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 flower itself.
00:51:56The fleshy coating was once the ovary as it grew around the maturing seeds.
00:52:03Lovely.
00:52:04Incredibly sweet.
00:52:06Very subtle.
00:52:08Isn't that great?
00:52:09Just the way that 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 it.
00:52:37All of these different types, all this diversity, is designed to attract animals to eat it.
00:52:55The fruit is one of the most remarkable transformations in nature.
00:53:02What begins as an advertisement for an insect, a flower, becomes 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, and the branches just up there.
00:54:36I'm sure, yeah, 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, allow them to get up
00:55:05into the trees.
00:55:08All 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. It'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.
00:55:46Yeah.
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!
00:57:13The glasses simulate colour-blindness by removing red from the picture.
00:57:20I can kind of tell the difference in contrast between some of them.
00:57:25That's got a very funny shade of bluish-ness.
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.
00:57:35It's just, overall, it's just got a kind of very almost bland grey-ness to it all.
00:57:45For primates to perceive red, they 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, one for green and one for blue.
00:58:13It meant they were colour-blind.
00:58:16But primates evolved a third type.
00:58:20It 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.
00:59:09You know, something that I think we just take for granted.
00:59:20Since they'd evolved 140 million years ago, flowers had transformed our planet.
00:59:27They'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.
01:00:16There's 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 between 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 out of the forests and into the savannah.
01:00:56And go on to trigger the birth of human civilization.
01:01:01Y'know
01:01:29Let's pray.
01:01:29Let's pray
01:01:35Transcription by CastingWords
Comments