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I've spent most of my life
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trying to understand the forces
that shaped our planet.
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As a geologist,
it always seemed to me
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that rocks were right
at the heart of things.
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But now, I'm discovering
it's not only volcanoes
and colliding continents
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00:00:26,360 --> 00:00:29,840
that have driven the
Earth's greatest changes,
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because at crucial moments
in its history,
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another force has helped create
the planet we live on...
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..plants.
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Just look at this seed.
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It's small, it's brown.
It weighs hardly anything.
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Looks pretty ordinary,
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but actually nothing
can be further from the truth
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because what it will become
is truly extraordinary.
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These are giant sequoias.
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Some are over 3,000 years old.
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And sequoias are the largest
single life form on Earth.
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All from a tiny seed.
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Yet even that pales
into insignificance
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when compared to what the whole of
the plant kingdom has done
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throughout the history
of our planet.
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They harness light from a star,
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bringing energy to our world.
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They and their ancestors
created our life-giving atmosphere.
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I'm breathing oxygen that was made
two and a half billion years ago.
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They sculpted the very surface
of the Earth
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and they drove the evolution
of all animals...
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..including our own ancestors.
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It's a whole new story
about our Earth...
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..told through remarkable images,
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captured for the very first time,
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and the latest
scientific discoveries.
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Wish me luck.
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This is the start of that story.
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How plants took a barren alien rock,
our planet,
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and transformed it into
the home we know today.
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Ooh! It's a long way down.
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I'm in Central Vietnam
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and I'm descending into one of
the largest caves in the world.
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The structure's
absolutely fantastic.
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Ugh!
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At 7km long,
this is known as Hang Son Doong.
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It's a dark, alien world.
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Down here, very little is alive.
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But I'm not here for the cave.
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Oh! Look at that!
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For goodness' sake!
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It looks like the roof has collapsed
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and the rainforest has just invaded.
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It's a rainforest inside a cave.
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After being in the darkness and
the black for ages, look at that.
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You just suddenly see brilliant
green.
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This isn't the entrance.
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We're three kilometres into the hear
of the cave system.
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It's a thriving lost world
with towering Polyalthia trees.
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00:04:06,120 --> 00:04:11,920
And home to strange creatures
like this Vietnamese
flat-backed millipede.
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Isn't that incredible!
It's got antlers.
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You really feel as if you've left
the confines of that cave
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and just escaped really
into this fantastic forest.
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It's a wonderland, really.
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This rainforest exists
because of one thing above all.
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Something which has enabled
plants to colonise
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almost everywhere on Earth...
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..light.
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Light which has travelled
150 million kilometres from the sun.
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Plants have this truly
remarkable ability
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to harness energy from
outer space to produce food.
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It's this ability to eat the sun,
to manufacture life from light,
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00:05:03,760 --> 00:05:06,520
that's allowed plants
to dominate our planet.
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This is the most important
natural process on Earth.
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It's how the plant kingdom has
transformed a lifeless planet
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into a living world.
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But it wasn't always like this.
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And to see how it started, we need
to go back three billion years.
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To begin with, our planet
was like an alien world.
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There was very little oxygen.
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The atmosphere was a cocktail
of toxic gases,
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like methane and sulphur dioxide.
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00:06:01,280 --> 00:06:04,280
The land was lifeless.
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00:06:08,680 --> 00:06:11,040
This barren saltpan
in southern Kenya
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is about as close as you can get
in the modern day Earth
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to that ancient world
three billion years ago.
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But the one crucial difference
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between the planet then
and the planet now
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is that back then
I'd have been burnt to a crisp.
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That's because the primitive
atmosphere couldn't screen out
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the sun's powerful ultraviolet rays.
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00:06:35,760 --> 00:06:39,560
Back then, these UV rays were
hundreds of times stronger
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than they are now.
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00:06:44,520 --> 00:06:48,000
Nothing could survive on land.
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Yet all this was about to change.
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A momentous event
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that would create the planet's first
life-supporting atmosphere.
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00:07:04,960 --> 00:07:09,200
This event, between three and
two and a half billion years ago,
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00:07:09,200 --> 00:07:14,920
was the single greatest turning poin
in the history of life on Earth.
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00:07:14,920 --> 00:07:19,840
And it was all brought about by
the earliest ancestors of plants.
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Here at the Sishen iron mine
in South Africa,
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evidence of that epic event
can still be unearthed today.
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00:07:38,680 --> 00:07:41,440
But to get to it,
you need a bit of help.
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SIREN
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MUFFLED VOICE
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Thirty seconds.
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Ten.
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LOUD EXPLOSION
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That is 200,000 tonnes of iron ore
just been blasted apart.
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00:08:09,160 --> 00:08:13,760
These explosions open
a cross section back in time
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00:08:13,760 --> 00:08:16,760
to the distant origins
of the plant kingdom.
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This is iron ore.
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It's so heavy.
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00:08:24,480 --> 00:08:28,680
Pure iron's got this metallic glint,
it's shiny,
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00:08:28,680 --> 00:08:32,440
but you can see that this
has got loads of red in it.
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And it's red for a really simple
reason. It's rusted.
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It's rusted because it's come into
contact with oxygen.
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Oxygen produced by the very first
burst of life.
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The miners want the ore
for its iron content.
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But I'm going to use this iron oxide
for a very different reason.
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Something I don't think has
ever been done before...
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which is why I'm a wee bit excited.
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I've taken a chunk of
the iron oxide rock
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00:09:02,320 --> 00:09:05,440
and had it ground up
into fine powder.
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It's then been turned
into a solution.
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One I'm hoping will allow me
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to take a breath from the planet's
earliest oxygen.
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Oxygen made by the ancient
ancestors of plants.
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00:09:21,760 --> 00:09:24,840
And now what I'm going to do is kind
of jump start it, really,
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with this battery.
I'm going to attach a lead
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and pass an
electric current through it.
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And we should see a simple reaction.
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Oh yeah, yeah.
There's some bubbles coming off.
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These bubbles are the gas oxygen.
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00:09:43,640 --> 00:09:48,800
It's being released
for the first time in over
two and a half billion years,
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when it was locked away in the rock.
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There's a lovely little train of
them just rising to the top and
forming a little pocket of gas.
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00:09:59,520 --> 00:10:03,080
You're never sure with these
experiments whether you're really
going to get it or not,
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00:10:03,080 --> 00:10:06,760
but that's exactly
what I was hoping to see.
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00:10:06,760 --> 00:10:11,280
In just one hour, I've collected
enough to fill the whole test tube.
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The thing is, this isn't
any old oxygen.
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This is oxygen that's
come from those iron bands.
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The very oxygen
that changed our planet.
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00:10:26,040 --> 00:10:29,200
In fact, I can't resist it.
I'm going to have to...
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INHALES
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Ah!
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I can't believe it.
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I'm breathing oxygen that was made
two and a half billion years ago.
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It's all gone.
Liberated from the rocks now.
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It's up there somewhere.
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These iron bands tell
a remarkable story.
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Oxygen was now flooding
the Earth's atmosphere.
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00:11:00,840 --> 00:11:04,280
It cleaned out the planet's
toxic gases,
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00:11:04,280 --> 00:11:08,920
leaving the sky a clear blue
for the first time.
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00:11:13,960 --> 00:11:16,560
Geologists call it
the Great Oxidation Event.
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00:11:16,560 --> 00:11:18,240
And it certainly was an event.
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This was an irreversible change
between two very different worlds -
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a planet with virtually no free
oxygen and a planet full of oxygen.
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This was the greatest change
in the history of life on Earth.
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00:11:33,920 --> 00:11:36,760
So how did this great event happen?
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The answer lies with
the first burst of life,
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which emerged not on the hostile
land but under water.
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Back then, water acted as a liquid
sunscreen to the dangerous UV rays.
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Under the protection of water,
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the earliest organisms
on Earth evolved
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in the form of tiny bacteria.
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And here in East Africa
is a rare chance
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to see what it would have been like.
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This is Lake Magadi.
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The waters here
are just super salty.
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Agh! Can feel it nipping away
at my feet.
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But the bacteria I'm wading through
are close descendants
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of the very first microorganisms
that lived three billion years ago.
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It's fantastic to think that swimmin
in the top layer here
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are some of the most primitive
life forms on Earth.
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And those bacteria, just like
the ones all that time ago,
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have got something
surprising about them.
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They're purple.
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These are hallow bacteria and they
didn't just occupy the occasional
lake.
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Much of the world's oceans
were purple, too.
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Imagine that from outer space.
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A purple Earth.
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00:13:08,200 --> 00:13:12,280
The purple bacteria live by
harnessing energy from the sun.
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00:13:13,680 --> 00:13:16,200
But they only use part of the light.
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Some rays pass deeper into the water
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And over time, down there,
a different type of bacteria evolved
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They had to live off the colours
of light left over.
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This made them appear green.
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00:13:32,920 --> 00:13:35,880
These were the green bacteria.
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This seemingly arbitrary event,
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bacteria absorbing one colour
of light rather than another,
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would have colossal repercussions
for the planet.
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Over time these green bacteria,
a type of Cyanobacteria,
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00:13:53,920 --> 00:13:57,440
came to dominate the waters
of the world.
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Eventually, as we'll see,
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00:13:59,240 --> 00:14:03,840
these green microorganisms became
the ancestor of all plants on Earth.
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00:14:03,840 --> 00:14:07,480
Because right from the start they
were reflecting green light,
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00:14:07,480 --> 00:14:11,640
the stalks of the plants became gree
and the leaves were green.
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00:14:11,640 --> 00:14:14,720
In fact, that's why all plants on
Earth became green,
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00:14:14,720 --> 00:14:16,600
from the grasses to the forests,
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00:14:16,600 --> 00:14:20,840
and it's also why today, instead of
living on a purple planet,
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00:14:20,840 --> 00:14:23,400
we've got a green one.
199
00:14:30,920 --> 00:14:33,400
But it wasn't just about colour.
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00:14:33,400 --> 00:14:36,640
Because the green bacteria
did something
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00:14:36,640 --> 00:14:39,160
their purple cousins couldn't.
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00:14:39,160 --> 00:14:41,000
They produced oxygen.
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00:14:44,800 --> 00:14:48,640
They would breathe life
into the lifeless land.
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00:14:48,640 --> 00:14:52,480
Without them, the story of our plane
would be more like that of Mars.
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00:14:55,080 --> 00:14:58,520
How the green bacteria did this
is so complex
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00:14:58,520 --> 00:15:01,680
that scientists still grapple
with the details.
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00:15:04,440 --> 00:15:09,120
I've come to the Eden Project in
Cornwall to try to understand it.
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00:15:10,560 --> 00:15:13,440
I'm to be the subject
of an experiment
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00:15:13,440 --> 00:15:16,320
that's never been attempted before.
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00:15:16,320 --> 00:15:17,760
Hi! Hello there.
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00:15:17,760 --> 00:15:20,240
I'm the guinea pig.
Doctor, I presume?
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00:15:20,240 --> 00:15:21,280
Indeed. Dan Martin.
213
00:15:21,280 --> 00:15:23,760
Hi there. Hi. Katrina Hope.
Nice to meet you.
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00:15:23,760 --> 00:15:25,800
Look at this! This is fantastic.
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00:15:25,800 --> 00:15:27,320
Incredible, isn't it?
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00:15:27,320 --> 00:15:30,640
I'm about to be locked inside
this airtight chamber.
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00:15:30,640 --> 00:15:36,240
I hope to experience first-hand
my very own Great Oxidation Event.
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00:15:36,240 --> 00:15:37,280
OK, everyone.
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00:15:37,280 --> 00:15:40,640
I'm going to start reducing
the oxygen concentration in here now.
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00:15:40,640 --> 00:15:42,600
BEEPING
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00:15:42,600 --> 00:15:47,040
The first step
is to lower oxygen levels
closer to those of the early Earth.
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00:15:49,160 --> 00:15:50,680
So first of all,
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00:15:50,680 --> 00:15:53,360
this is going to monitor your
heart rate and your oxygen levels
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00:15:53,360 --> 00:15:56,440
so if we pop that on we can just
have a look here.
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00:15:56,440 --> 00:16:01,760
It's a lack of oxygen
that complex life like us
can't operate at for long.
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00:16:01,760 --> 00:16:05,000
So at the top is your heart rate.
227
00:16:05,000 --> 00:16:06,720
How's that? Is that really high?
228
00:16:06,720 --> 00:16:10,000
I think you might be a little bit
anxious about going in there.
229
00:16:10,000 --> 00:16:11,040
I am a little bit.
230
00:16:11,040 --> 00:16:13,880
I'm sure your resting
heart rate's not normally 95.
231
00:16:13,880 --> 00:16:17,280
No, I have been thinking
a lot about it.
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00:16:17,280 --> 00:16:21,720
My vital signs are being monitored,
along with the oxygen levels
in my blood.
233
00:16:21,720 --> 00:16:26,920
Now it's time to be sealed inside
the chamber for the next 48 hours.
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00:16:28,600 --> 00:16:32,560
I'm as ready as I'll ever be, guys,
so can we open this door?
235
00:16:32,560 --> 00:16:34,800
Wish me luck.
236
00:16:38,760 --> 00:16:40,760
It's small, isn't it?
237
00:16:45,240 --> 00:16:49,000
Oxygen levels in the air
are normally 21%.
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00:16:49,000 --> 00:16:50,080
BEEPING
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00:16:50,080 --> 00:16:53,280
Inside the chamber,
they're far lower.
240
00:16:53,280 --> 00:16:55,400
Just over 12%.
241
00:16:56,400 --> 00:16:58,240
At these concentrations,
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00:16:58,240 --> 00:17:01,200
the cellular activity
in my body and brain
243
00:17:01,200 --> 00:17:03,320
is starting to slow down.
Three, two, one...
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00:17:03,320 --> 00:17:06,360
Go! Green, yellow...
245
00:17:06,360 --> 00:17:10,120
red, green, ye... Kind of orange...
246
00:17:10,120 --> 00:17:13,520
Er... purple, blue.
247
00:17:13,520 --> 00:17:16,920
You'll find that thinking
becomes a little bit slower.
248
00:17:16,920 --> 00:17:21,040
My hand-to-eye coordination
is being impaired.
249
00:17:22,600 --> 00:17:26,280
You can put them in any order
you like. That's the way.
250
00:17:26,280 --> 00:17:28,720
Can you just tell us
how exactly are you feeling?
251
00:17:28,720 --> 00:17:34,120
It's funny. I felt very slow.
That slowness is there, definitely.
252
00:17:37,120 --> 00:17:40,840
The doctors calculate
that at the rate I use up oxygen,
253
00:17:40,840 --> 00:17:46,320
if it carried on like this,
I'd be unconscious in just 24 hours.
254
00:17:46,320 --> 00:17:50,200
Your oxygen saturation, sort of 88%.
255
00:17:50,200 --> 00:17:52,200
If that was your level in hospital,
256
00:17:52,200 --> 00:17:54,200
we'd be pretty
worried about you right now.
257
00:17:55,600 --> 00:18:00,440
The next crucial step is to see
if the 300 plants in here with me
258
00:18:00,440 --> 00:18:03,240
can produce enough oxygen
to keep me alive.
259
00:18:05,080 --> 00:18:08,080
It's all to do with the wondrous
ability they inherited
260
00:18:08,080 --> 00:18:10,160
from those green bacteria.
261
00:18:10,160 --> 00:18:13,320
It's photosynthesis, of course.
262
00:18:13,320 --> 00:18:15,520
I think we can have
the lights on, please.
263
00:18:17,720 --> 00:18:20,280
To kick start it, you need light.
264
00:18:21,640 --> 00:18:24,280
Wow! Suddenly the light's hit.
265
00:18:30,440 --> 00:18:33,440
Plants use photosynthesis
to live and grow,
266
00:18:33,440 --> 00:18:35,480
and most importantly for me...
267
00:18:36,720 --> 00:18:38,440
..to make oxygen.
268
00:18:39,880 --> 00:18:45,440
Photosynthesis is
an intricate process that science
is still trying to unlock.
269
00:18:47,320 --> 00:18:52,000
But the production of oxygen
is one of its key features.
270
00:18:52,000 --> 00:18:54,880
To understand what's happening,
271
00:18:54,880 --> 00:18:59,200
you need to enter a complex
and microscopic world.
272
00:19:01,040 --> 00:19:05,520
Inside every leaf
of every plant on the planet
273
00:19:05,520 --> 00:19:09,560
are the direct descendants
of those first green bacteria.
274
00:19:09,560 --> 00:19:13,440
Magnify a leaf 1,000 times
and you can see them.
275
00:19:13,440 --> 00:19:15,840
They're known as chloroplasts.
276
00:19:15,840 --> 00:19:18,240
Packed into every cell.
277
00:19:21,320 --> 00:19:23,840
They still behave
a bit like bacteria.
278
00:19:23,840 --> 00:19:28,080
This is real footage of them moving
towards a flash of light.
279
00:19:33,640 --> 00:19:37,160
They're just 5,000ths
of a millimetre across.
280
00:19:37,160 --> 00:19:41,920
And it's inside chloroplasts
that photosynthesis happens.
281
00:19:45,240 --> 00:19:48,480
Light rays from the sun
are made of photons.
282
00:19:49,480 --> 00:19:53,800
They're tiny, fast-moving particles
of electromagnetic energy.
283
00:19:55,360 --> 00:20:00,840
When they hit the surface, the energ
of the photons is captured by a ring
284
00:20:00,840 --> 00:20:03,920
called the light-harvesting complex.
285
00:20:07,160 --> 00:20:08,800
Inside this structure,
286
00:20:08,800 --> 00:20:12,800
the energy of two photons is used
to split a water molecule.
287
00:20:17,960 --> 00:20:23,120
It's ripped into its two elements -
hydrogen and oxygen.
288
00:20:26,000 --> 00:20:29,280
The plant uses the hydrogen
to live and grow.
289
00:20:31,600 --> 00:20:35,560
But right now, I'm interested in
the other part of the water.
290
00:20:35,560 --> 00:20:38,840
The part plants pump out
as a waste product -
291
00:20:38,840 --> 00:20:40,440
the oxygen.
292
00:20:53,400 --> 00:20:57,760
Scientists have calculated that
the 300 plants in here with me
293
00:20:57,760 --> 00:21:00,560
should raise oxygen levels
in this chamber
294
00:21:00,560 --> 00:21:04,960
from 12 to 21% within 48 hours.
295
00:21:07,280 --> 00:21:12,600
I'm finding out how reliable the
process of photosynthesis really is.
296
00:21:15,800 --> 00:21:17,360
It is quite concerning.
297
00:21:17,360 --> 00:21:21,040
You've been very busy this afternoon,
a lot of activity,
298
00:21:21,040 --> 00:21:23,680
so we need to restrict the amount
that you're talking
299
00:21:23,680 --> 00:21:26,280
and really get you resting
as much as possible,
300
00:21:26,280 --> 00:21:28,640
not dashing around the chamber
any more.
301
00:21:28,640 --> 00:21:31,000
This is doctor's orders - bed rest.
302
00:21:31,000 --> 00:21:32,440
Night-night!
303
00:21:38,400 --> 00:21:40,480
As I drift off to sleep,
304
00:21:40,480 --> 00:21:43,440
the 11,000 leaves go to work.
305
00:21:46,440 --> 00:21:49,840
They have 30 cubic metres
of the box to fill.
306
00:21:51,280 --> 00:21:55,720
Some plants, like this maize,
and the banana plant
307
00:21:55,720 --> 00:21:59,080
are particularly efficient
at pumping out oxygen.
308
00:22:04,440 --> 00:22:07,240
So we can see the increase
every hour here.
309
00:22:07,240 --> 00:22:08,680
That's incredible really.
310
00:22:08,680 --> 00:22:11,440
They're really pushing out a lot of
oxygen, as you can see.
311
00:22:15,080 --> 00:22:21,120
Every hour, my plants are producing
over 40 litres of oxygen.
312
00:22:21,120 --> 00:22:24,200
Hi, Iain. It's Katrina.
We're now 41 hours in.
313
00:22:24,200 --> 00:22:26,080
Really? 41 hours in?
314
00:22:26,080 --> 00:22:29,200
Yeah. The oxygen levels are still
climbing gradually every hour
315
00:22:29,200 --> 00:22:31,800
so it's going really well.
316
00:22:31,800 --> 00:22:34,800
With my vital signs
returning to normal,
317
00:22:34,800 --> 00:22:37,640
I'm now a top attraction
at the Eden Project.
318
00:22:37,640 --> 00:22:39,080
Hello! Hello!
319
00:22:39,080 --> 00:22:41,560
Can you see him?
What's he doing in that box?
320
00:22:41,560 --> 00:22:43,120
He looks very happy in there.
321
00:22:43,120 --> 00:22:46,280
What's that on his finger?
It's measuring his oxygen levels.
322
00:22:46,280 --> 00:22:48,760
Eat your heart out, David Blaine!
323
00:22:51,000 --> 00:22:54,320
Finally after 48 long hours,
324
00:22:54,320 --> 00:22:57,720
oxygen levels are almost
back to normal.
325
00:22:57,720 --> 00:23:00,520
The plants have triumphed.
326
00:23:05,880 --> 00:23:07,480
Wa-hay!
327
00:23:07,480 --> 00:23:09,600
Oh, I'm out!
328
00:23:09,600 --> 00:23:12,640
Ah! Survived it. Fantastic!
329
00:23:12,640 --> 00:23:17,520
It's amazing just thinking that
I've survived, but actually...
330
00:23:17,520 --> 00:23:20,760
I guess I've really survived
because of them, cos of the plants.
331
00:23:20,760 --> 00:23:23,400
I leave here thinking that
I needed those plants
332
00:23:23,400 --> 00:23:25,320
way more than they needed me.
333
00:23:25,320 --> 00:23:28,120
It's easy to think
of this as just an experiment
334
00:23:28,120 --> 00:23:30,120
but to me,
when you're lying in there,
335
00:23:30,120 --> 00:23:33,600
you realise this place is a metaphor
for something much bigger,
336
00:23:33,600 --> 00:23:34,960
for the planet, really,
337
00:23:34,960 --> 00:23:37,040
and for our relationship with plants
338
00:23:37,040 --> 00:23:40,280
through photosynthesis
to keep life going.
339
00:23:42,920 --> 00:23:45,520
The early Earth was like my chamber.
340
00:23:45,520 --> 00:23:49,200
It was transformed from a world
with very little oxygen
341
00:23:49,200 --> 00:23:51,640
to a world rich in oxygen.
342
00:23:51,640 --> 00:23:55,560
And all that oxygen
began to do something else.
343
00:23:56,560 --> 00:24:00,000
High in the stratosphere,
it created ozone.
344
00:24:03,120 --> 00:24:06,720
This was a protective blanket
which enveloped the Earth
345
00:24:06,720 --> 00:24:10,120
and blocked most of the
sun's dangerous UV rays.
346
00:24:11,960 --> 00:24:15,880
It meant that for the first time
in the planet's history,
347
00:24:15,880 --> 00:24:18,200
plants could move on to the land.
348
00:24:18,200 --> 00:24:21,480
But it was no small step.
349
00:24:32,000 --> 00:24:35,560
If you'd been protected by water
for billions of years
350
00:24:35,560 --> 00:24:39,040
then the move to the land
was going to be a rude shock.
351
00:24:39,040 --> 00:24:44,800
Yet over 400 million years ago,
plants finally made that leap.
352
00:24:47,440 --> 00:24:50,960
Surprisingly, the best evidence
for these pioneers
353
00:24:50,960 --> 00:24:54,200
doesn't come from some
exotic corner of our planet,
354
00:24:54,200 --> 00:24:56,360
but from Britain.
355
00:24:59,720 --> 00:25:03,640
I've come to just outside the villag
of Rhynie in northeast Scotland
356
00:25:03,640 --> 00:25:06,200
to see this - a stone wall.
357
00:25:06,200 --> 00:25:08,480
But not just any stone wall,
of course.
358
00:25:08,480 --> 00:25:13,360
For me, this is the most important
stone wall in the history of science
359
00:25:20,840 --> 00:25:27,560
Back 410 million years ago, Scotland
was located well south of the equato
360
00:25:27,560 --> 00:25:30,120
and looked like another world.
361
00:25:33,880 --> 00:25:38,880
Hot springs and geysers boiled out
across a rocky and barren landscape.
362
00:25:43,800 --> 00:25:48,160
But something else was happening,
as scientists discovered
363
00:25:48,160 --> 00:25:51,800
when they came across some curious
markings in this wall.
364
00:25:51,800 --> 00:25:53,840
This is one of them. Look at this.
365
00:25:53,840 --> 00:25:57,960
You see these really strange
elongated shapes here.
366
00:25:57,960 --> 00:26:00,880
The first people just didn't really
know what they were.
367
00:26:00,880 --> 00:26:03,440
They thought maybe, at first,
it was some kind of lava
368
00:26:03,440 --> 00:26:05,720
but when they looked really closely,
369
00:26:05,720 --> 00:26:09,360
especially when they got it cut
and polished, this rock literally
came alive.
370
00:26:15,200 --> 00:26:19,320
Because you can see these dark
features here,
371
00:26:19,320 --> 00:26:23,400
they realised that this
was something that was once living.
372
00:26:25,480 --> 00:26:29,240
And when they were alive,
this is what they looked like.
373
00:26:32,480 --> 00:26:36,760
Just a few centimetres tall,
they're called Aglaophyton.
374
00:26:38,480 --> 00:26:41,840
Bulbous shapes
on the end of naked stems.
375
00:26:44,280 --> 00:26:46,920
A time before leaves or roots,
376
00:26:46,920 --> 00:26:52,000
yet somehow these bizarre life forms
survived along the water's edge.
377
00:26:53,080 --> 00:26:56,360
What geologists had found
right here in Scotland
378
00:26:56,360 --> 00:26:58,640
were some of the earliest
pioneering plants
379
00:26:58,640 --> 00:27:02,720
to make that giant leap,
to colonise the land.
380
00:27:06,600 --> 00:27:11,120
And around this time, all along
the margins of lakes and rivers,
381
00:27:11,120 --> 00:27:13,920
primitive plants were coming ashore.
382
00:27:17,320 --> 00:27:20,200
For the first time
when viewed from space,
383
00:27:20,200 --> 00:27:23,120
the land began to look alive.
384
00:27:23,120 --> 00:27:28,800
The beginning of a transformation
from hostile world to fertile Earth.
385
00:27:32,120 --> 00:27:34,960
Yet this wasn't
a full-scale invasion.
386
00:27:34,960 --> 00:27:37,920
Just a toehold.
387
00:27:37,920 --> 00:27:40,840
Plants were still tied
to the water's edge,
388
00:27:40,840 --> 00:27:46,080
unable to head inland and
penetrate the harsh, rocky surface.
389
00:27:47,200 --> 00:27:50,520
But all this was about to change.
390
00:27:52,040 --> 00:27:55,360
Plants evolved an inspired solution
to the problem,
391
00:27:55,360 --> 00:27:58,640
a brilliant device for
collecting water and nutrients
392
00:27:58,640 --> 00:28:01,640
and something that they never
really had before.
393
00:28:01,640 --> 00:28:03,320
Roots.
394
00:28:11,800 --> 00:28:13,200
Cambodia.
395
00:28:13,200 --> 00:28:15,600
The 12th-century temple
here at Ta Prohm
396
00:28:15,600 --> 00:28:18,200
is a wonder of civilisation,
397
00:28:18,200 --> 00:28:21,680
but it's also a wonder
of the natural world.
398
00:28:21,680 --> 00:28:25,560
Although the roots of these
strangler figs are very different
399
00:28:25,560 --> 00:28:27,520
from the first ones to evolve,
400
00:28:27,520 --> 00:28:33,240
it's a superb place to reveal
how roots allowed plants
to invade inland.
401
00:28:36,760 --> 00:28:40,520
Roots are hugely powerful.
I love this one.
402
00:28:40,520 --> 00:28:42,880
Look at it prising
its way into that roof,
403
00:28:42,880 --> 00:28:45,040
just lifting
that whole structure up.
404
00:28:45,040 --> 00:28:46,960
And then boring down here
405
00:28:46,960 --> 00:28:49,840
through these stone blocks
and then disappearing.
406
00:28:49,840 --> 00:28:55,880
Just tiny pressures exerted over
decades of centuries.
407
00:28:57,280 --> 00:29:00,960
Add these up and you get
phenomenal strength.
408
00:29:00,960 --> 00:29:03,920
A pressure of up to 10kg
per square cm.
409
00:29:05,120 --> 00:29:09,320
Around 400 million years ago,
the first roots appeared...
410
00:29:10,680 --> 00:29:16,040
...and gave plants the ability
to smash up the rocky planet.
411
00:29:17,320 --> 00:29:21,880
And this created a vital ingredient
for life on land.
412
00:29:23,320 --> 00:29:26,680
When the tiny, broken-up
fragments of rock
413
00:29:26,680 --> 00:29:29,520
get mixed up with
dead plant material,
414
00:29:29,520 --> 00:29:33,280
it ends up as this ideal environment
for storing water.
415
00:29:33,280 --> 00:29:37,520
An environment that we call soil.
416
00:29:39,360 --> 00:29:43,440
Today, soil covers 40%
of the planet's land.
417
00:29:44,440 --> 00:29:49,640
It takes a long time to form,
1,000 years to make just 2cm of soil
418
00:29:49,640 --> 00:29:54,680
But it's essential for plant life,
just as it was back then.
419
00:29:57,120 --> 00:29:59,800
Because the primitive leafless plant
420
00:29:59,800 --> 00:30:02,240
could now break free
from the water's edge.
421
00:30:04,720 --> 00:30:09,880
Roots, and the soil they created,
made plants unstoppable...
422
00:30:10,920 --> 00:30:15,080
...allowing them to colonise inland
for the first time.
423
00:30:15,080 --> 00:30:20,080
An invasion that would have
a dramatic influence
on all life on Earth.
424
00:30:27,680 --> 00:30:29,560
For millions of years,
425
00:30:29,560 --> 00:30:32,800
animals had been confined
to the rivers and oceans.
426
00:30:33,800 --> 00:30:37,440
Now they could finally
emerge from the water.
427
00:30:39,360 --> 00:30:42,920
We get an idea of those
first tentative steps
428
00:30:42,920 --> 00:30:45,080
by travelling back in time
429
00:30:45,080 --> 00:30:49,400
with a creature that's barely
changed for 500 million years.
430
00:30:58,560 --> 00:31:01,160
I've come to the east coast
of America,
431
00:31:01,160 --> 00:31:05,480
where these ancient creatures
still come ashore at dusk to mate.
432
00:31:08,200 --> 00:31:09,960
Here they are.
433
00:31:09,960 --> 00:31:11,880
Horseshoe crabs.
434
00:31:13,800 --> 00:31:16,080
Looks like something
from another planet.
435
00:31:17,240 --> 00:31:19,400
He sees with two main eyes here,
436
00:31:19,400 --> 00:31:23,640
but they've got something like
ten eyes scattered across their body
437
00:31:23,640 --> 00:31:27,680
and the really weird bit
is if you lift them up.
438
00:31:27,680 --> 00:31:29,320
Look at that.
439
00:31:29,320 --> 00:31:31,560
For a start, they've got
five pairs of legs.
440
00:31:31,560 --> 00:31:33,440
Look - one, two, three, four, five,
441
00:31:33,440 --> 00:31:35,600
whereas normal crabs just have four.
442
00:31:35,600 --> 00:31:38,880
They're actually more related to
the scorpion than to normal crabs.
443
00:31:38,880 --> 00:31:39,920
Look at that.
444
00:31:39,920 --> 00:31:43,040
But the really interesting
bit is tucked under here.
445
00:31:43,040 --> 00:31:45,600
You get these things called book
gills.
446
00:31:45,600 --> 00:31:48,680
Look at that there.
It's like sheaves of a book.
447
00:31:48,680 --> 00:31:51,520
And that allows them
to extract oxygen,
448
00:31:51,520 --> 00:31:54,760
not just from the water
but also from the air.
449
00:31:54,760 --> 00:31:56,840
It's an amazing breathing apparatus.
450
00:31:58,000 --> 00:31:59,600
Better put her back now.
451
00:31:59,600 --> 00:32:01,920
Come on, dear.
There you go.
452
00:32:07,200 --> 00:32:09,160
As long as they're kept moist,
453
00:32:09,160 --> 00:32:11,800
these lung-like gills
enable the crabs
454
00:32:11,800 --> 00:32:14,280
to stay out of water
for days at a time.
455
00:32:15,560 --> 00:32:19,000
Fossils show that horseshoe
crabs appeared on land
456
00:32:19,000 --> 00:32:20,600
at least 400 million years ago.
457
00:32:21,800 --> 00:32:24,960
They are some of the first animals
ever to come ashore.
458
00:32:31,040 --> 00:32:34,400
Amphibians and insects
soon followed.
459
00:32:35,440 --> 00:32:39,160
Oxygen allowed them
to move onto land.
460
00:32:39,160 --> 00:32:42,080
But something else
was also enticing them.
461
00:32:43,800 --> 00:32:47,160
It's funny. Plants create oxygen
as a waste product
462
00:32:47,160 --> 00:32:51,480
and it's that waste product that has
transformed our atmosphere.
463
00:32:51,480 --> 00:32:54,480
But of course, the main reason
that plants photosynthesise
464
00:32:54,480 --> 00:32:55,920
is to create sugars.
465
00:32:55,920 --> 00:32:59,240
Sugars that are vital for plants
to live and to grow
466
00:32:59,240 --> 00:33:03,280
and also provide a source of food
for all animals.
467
00:33:08,240 --> 00:33:10,280
Plants make this sugar from water...
468
00:33:12,280 --> 00:33:14,800
..carbon dioxide from the air...
469
00:33:16,000 --> 00:33:17,920
..and energy from the sun.
470
00:33:21,240 --> 00:33:24,880
And again, it all happens
in those tiny chloroplasts.
471
00:33:27,560 --> 00:33:32,080
We've seen how light splits water
into oxygen and hydrogen.
472
00:33:34,120 --> 00:33:36,440
The plant takes that hydrogen
473
00:33:36,440 --> 00:33:40,360
and combines it with carbon dioxide
to make sugar.
474
00:33:43,080 --> 00:33:48,160
By exposing a plant to carbon dioxid
tagged with a radioactive marker,
475
00:33:48,160 --> 00:33:51,240
you can see the sugar being created.
476
00:33:51,240 --> 00:33:52,640
For the first time,
477
00:33:52,640 --> 00:33:56,600
scientists have imaged its creation
and movement through a plant.
478
00:33:56,600 --> 00:33:58,680
In this case - maize.
479
00:34:01,240 --> 00:34:05,360
As soon as carbon dioxide
is sucked into the plant's cells,
480
00:34:05,360 --> 00:34:07,680
they begin to glow.
481
00:34:07,680 --> 00:34:09,760
This is the actual moment
482
00:34:09,760 --> 00:34:14,320
that photosynthesis turns
the carbon dioxide into sugar.
483
00:34:16,440 --> 00:34:20,000
In just 15 minutes,
the newly-formed sugar
484
00:34:20,000 --> 00:34:22,720
is sent to the roots for storage.
485
00:34:22,720 --> 00:34:28,880
The plant can then use this sugar
to grow and thrive.
486
00:34:31,120 --> 00:34:35,440
That's why photosynthesis is nature'
most astonishing achievement.
487
00:34:35,440 --> 00:34:40,280
The ability of plants to be powered
by light from beyond our planet
488
00:34:40,280 --> 00:34:42,600
sets them apart from all other life.
489
00:34:42,600 --> 00:34:46,480
And that connection
with that star, our sun,
490
00:34:46,480 --> 00:34:50,520
makes plants a foundation stone
for all living things.
491
00:34:50,520 --> 00:34:53,040
It's just such a wonderful thought.
492
00:34:57,200 --> 00:34:59,040
400 million years ago,
493
00:34:59,040 --> 00:35:03,440
leafless plants were flourishing
like never before.
494
00:35:06,600 --> 00:35:10,080
But a dramatic transformation
of the atmosphere
495
00:35:10,080 --> 00:35:13,400
was about to throw plants
into a global crisis.
496
00:35:14,360 --> 00:35:16,920
Not only would it change their shape
497
00:35:16,920 --> 00:35:19,880
it would change
all life on our planet.
498
00:35:21,560 --> 00:35:25,280
MAORI CHANTING
499
00:35:38,240 --> 00:35:41,680
This is Lake Tarawera
in New Zealand.
500
00:35:44,520 --> 00:35:47,440
This ancient landscape
is home to a plant
501
00:35:47,440 --> 00:35:52,440
that 360 million years ago
confronted that crisis.
502
00:35:52,440 --> 00:35:54,960
It came up with an inspired solution
503
00:35:57,360 --> 00:36:00,200
Looks like the land that
time forgot, doesn't it?
504
00:36:00,200 --> 00:36:01,720
Just that strange mixture
505
00:36:01,720 --> 00:36:04,120
of different shapes
of plants and trees.
506
00:36:04,120 --> 00:36:06,440
Really unfamiliar and alien.
507
00:36:06,440 --> 00:36:08,880
It's almost primeval.
508
00:36:12,080 --> 00:36:15,960
The early plants had become
victims of their own success.
509
00:36:15,960 --> 00:36:19,920
They were gorging on so much
carbon dioxide in the atmosphere
510
00:36:19,920 --> 00:36:21,680
that they were using it up.
511
00:36:22,840 --> 00:36:25,840
Levels plummeted by 90%.
512
00:36:27,360 --> 00:36:31,760
Without enough of this vital gas,
plants began struggling.
513
00:36:31,760 --> 00:36:36,640
If they couldn't find a way
to breathe in more carbon dioxide,
514
00:36:36,640 --> 00:36:38,400
they'd suffocate.
515
00:36:40,560 --> 00:36:44,560
The early plants, plants like
these gorgeous ferns here,
516
00:36:44,560 --> 00:36:47,680
came up with a remarkable
new structure.
517
00:36:47,680 --> 00:36:52,920
Large, flat surfaces that house
within them a complex breathing
apparatus.
518
00:36:52,920 --> 00:36:55,000
We call them leaves.
519
00:36:59,680 --> 00:37:03,720
Leaves were the answer to
all plants' breathing problems.
520
00:37:04,800 --> 00:37:09,360
They massively increased their
surface area by over a hundredfold,
521
00:37:09,360 --> 00:37:12,680
allowing them to absorb
far more carbon dioxide.
522
00:37:15,720 --> 00:37:17,720
Now, for the first time,
523
00:37:17,720 --> 00:37:23,000
shade was cast by a beautiful
and delicate canopy,
like these Dicksonia.
524
00:37:24,040 --> 00:37:26,600
These ferns are incredible.
525
00:37:26,600 --> 00:37:28,720
They're like giant umbrellas.
526
00:37:31,360 --> 00:37:34,440
The key to this advanced
breathing apparatus
527
00:37:34,440 --> 00:37:37,120
is on the underside
of each fern leaf.
528
00:37:37,120 --> 00:37:41,320
They're microscopic holes
called stomata.
529
00:37:43,240 --> 00:37:46,680
Filmed and actioned with
an electron microscope,
530
00:37:46,680 --> 00:37:48,360
this is them opening and closing.
531
00:37:48,360 --> 00:37:52,400
Speeded up 140 times.
532
00:38:00,600 --> 00:38:04,320
There are thousands of stomata
on every leaf on Earth.
533
00:38:06,400 --> 00:38:08,680
They allow a single fern
534
00:38:08,680 --> 00:38:12,400
to breathe in five litres
of carbon dioxide a day.
535
00:38:21,320 --> 00:38:24,080
The evolution of leaves,
rich in stomata,
536
00:38:24,080 --> 00:38:27,280
saved plants from suffocation.
537
00:38:28,360 --> 00:38:31,840
But leaves also allow plants
to capture more light.
538
00:38:32,880 --> 00:38:36,560
This in turn fuelled
fierce competition,
539
00:38:36,560 --> 00:38:39,640
each plant desperate
for the sun's rays.
540
00:38:42,640 --> 00:38:47,240
This family squabble would
lead to a new type of plant.
541
00:38:47,240 --> 00:38:50,760
One that would have surprising
repercussions for the planet.
542
00:38:52,880 --> 00:38:55,240
How do we know?
543
00:38:55,240 --> 00:38:58,480
Well, it's all thanks
to some rare evidence here
544
00:38:58,480 --> 00:39:01,000
in Nova Scotia in Canada.
545
00:39:03,760 --> 00:39:07,960
To reach it, you have to abseil
to the bottom of this 30m cliff.
546
00:39:09,200 --> 00:39:14,000
Here, scientists discovered
the remains of a mysterious world.
547
00:39:15,280 --> 00:39:17,760
You know, this is just
the best way to see rocks.
548
00:39:17,760 --> 00:39:20,240
You really feel as if
you're a time traveller,
549
00:39:20,240 --> 00:39:23,480
peeling back the layers of history
one by one as you go down.
550
00:39:23,480 --> 00:39:28,240
These rocks are over
300 million years old.
551
00:39:29,520 --> 00:39:33,240
But it's what's locked inside the
rocks at the base of this cliff
552
00:39:33,240 --> 00:39:35,400
that took scientists' breath away.
553
00:39:40,480 --> 00:39:43,880
These fossilised remains
are just spectacular!
554
00:39:43,880 --> 00:39:45,480
I mean, look at the texture.
555
00:39:45,480 --> 00:39:47,240
You can tell it's a plant
556
00:39:47,240 --> 00:39:50,760
but this isn't some big shrub
or overgrown fern.
557
00:39:50,760 --> 00:39:54,240
You can see here, look,
you can get traces of bark.
558
00:39:54,240 --> 00:39:57,240
And down here, you can see
there are some roots coming off.
559
00:39:57,240 --> 00:40:00,400
This is completely extinct,
you don't get this any more,
560
00:40:00,400 --> 00:40:02,520
but what I'm actually
crouching beside
561
00:40:02,520 --> 00:40:05,000
is one of the planet's
very early tree trunks.
562
00:40:05,000 --> 00:40:07,120
And not just one tree, cos look here
563
00:40:07,120 --> 00:40:08,720
There's another one here.
564
00:40:10,680 --> 00:40:11,920
There's another there.
565
00:40:13,280 --> 00:40:16,000
This is a fossil forest.
566
00:40:18,480 --> 00:40:23,160
These Lepidodendron trees had
strange diamond-shaped bark.
567
00:40:24,160 --> 00:40:27,160
Each diamond sprouting
a needle-like leaf.
568
00:40:29,320 --> 00:40:32,080
Over 300 million years ago,
569
00:40:32,080 --> 00:40:36,280
they made up the planet's
first tropical forests.
570
00:40:46,160 --> 00:40:49,240
Found in swamps throughout
the Earth's tropics,
571
00:40:49,240 --> 00:40:51,920
these first forests were so extensiv
572
00:40:51,920 --> 00:40:55,440
you'd have seen a band
of dark green from space.
573
00:40:57,880 --> 00:41:01,920
And all those new leaves
were pumping out oxygen,
574
00:41:01,920 --> 00:41:06,040
so much that levels
of oxygen increased
575
00:41:06,040 --> 00:41:09,320
to not far off double
what they are today.
576
00:41:12,000 --> 00:41:14,760
It was having a very odd
effect on animals...
577
00:41:16,640 --> 00:41:19,800
..in particular,
insects and their cousins.
578
00:41:21,680 --> 00:41:25,480
Instead of lungs, invertebrates
have simple breathing tubes
579
00:41:25,480 --> 00:41:31,000
that rely on diffusion for oxygen
to reach their internal organs.
580
00:41:31,000 --> 00:41:33,760
The size of these animals
is therefore limited
581
00:41:33,760 --> 00:41:36,920
by the concentration of oxygen
in the air.
582
00:41:38,080 --> 00:41:41,800
Increase the oxygen,
just as the first forest did,
583
00:41:41,800 --> 00:41:44,000
and things get interesting.
584
00:41:47,520 --> 00:41:49,960
Do you see these markings
on the rock here?
585
00:41:49,960 --> 00:41:53,280
There's two lines of little dents,
one here and one here.
586
00:41:53,280 --> 00:41:55,520
They are fossilised footprints
587
00:41:55,520 --> 00:41:58,360
that date back to
the very early forests.
588
00:41:58,360 --> 00:42:00,160
When scientists first studied them
589
00:42:00,160 --> 00:42:03,520
they realised they weren't made
by some reptile or amphibian.
590
00:42:03,520 --> 00:42:05,160
They were made by a millipede.
591
00:42:05,160 --> 00:42:09,160
Now, here is one of the
biggest millipede species
592
00:42:09,160 --> 00:42:12,360
alive on Earth today.
593
00:42:12,360 --> 00:42:13,920
That's pretty big.
594
00:42:18,840 --> 00:42:20,880
Using the tracks for scale,
595
00:42:20,880 --> 00:42:25,320
it's clear the ancestors of
this little fellow were massive.
596
00:42:32,360 --> 00:42:37,320
Called Arthropleuridea,
it was over 2m long.
597
00:42:39,080 --> 00:42:41,760
The forests would have been
terrifying.
598
00:42:42,880 --> 00:42:46,760
With giant scorpions
and giant spiders.
599
00:42:50,640 --> 00:42:53,240
And not just on the land.
600
00:42:53,240 --> 00:42:57,280
I think the most impressive
of all were the dragonflies.
601
00:42:57,280 --> 00:43:01,480
Most modern dragonflies have
wing spans up to 10cm across,
602
00:43:01,480 --> 00:43:04,080
but back then they were way larger.
603
00:43:04,080 --> 00:43:07,520
Some were up to a metre across.
604
00:43:14,160 --> 00:43:19,760
These Meganeura were the largest
insects ever to take to the skies.
605
00:43:22,440 --> 00:43:26,640
But in this oversize world
pumped with oxygen,
606
00:43:26,640 --> 00:43:29,320
the plant kingdom
still reigned supreme.
607
00:43:31,200 --> 00:43:34,160
Then, 230 million years ago,
608
00:43:34,160 --> 00:43:38,840
a new group of animals emerged from
the shadows of the swampy forests.
609
00:43:38,840 --> 00:43:42,400
They would become the largest
creatures to roam the Earth
610
00:43:42,400 --> 00:43:46,120
and they were ready to do battle
with the kingdom of the plants.
611
00:43:46,120 --> 00:43:49,000
I'm talking, of course, of dinosaurs
612
00:43:49,000 --> 00:43:50,880
ROARING
613
00:43:52,600 --> 00:43:56,600
It's the meat-eaters
that get all the press.
614
00:43:58,120 --> 00:44:00,520
But recent research has revealed
615
00:44:00,520 --> 00:44:03,400
that out of the
700 species discovered,
616
00:44:03,400 --> 00:44:06,200
over two-thirds were herbivores.
617
00:44:07,240 --> 00:44:12,720
Vegetarians ruled, led by
the biggest herbivores in history...
618
00:44:13,720 --> 00:44:15,520
..the sauropods.
619
00:44:18,640 --> 00:44:22,920
To discover the impact of these
huge dinosaurs on the plant kingdom,
620
00:44:22,920 --> 00:44:26,320
I've come to an animal sanctuary
to see it in the flesh.
621
00:44:29,760 --> 00:44:32,680
Unfortunately this place
doesn't have a living sauropod,
622
00:44:32,680 --> 00:44:35,920
but what it does have
is the biggest herbivore
623
00:44:35,920 --> 00:44:37,560
that the planet's got to offer -
624
00:44:37,560 --> 00:44:39,360
the African elephant.
625
00:44:39,360 --> 00:44:41,200
Come and meet Butch.
626
00:44:42,280 --> 00:44:46,480
This beautiful four-tonne elephant
can help me truly appreciate
627
00:44:46,480 --> 00:44:48,600
the staggering size of the dinosaurs
628
00:44:54,920 --> 00:44:56,600
Can we go up?
629
00:45:00,480 --> 00:45:04,520
Butch here is about as big
as a big African bull gets
630
00:45:04,520 --> 00:45:09,480
and that's already four metres high,
631
00:45:09,480 --> 00:45:13,480
but if we want to get to
the height of a sauropod,
we have to go much higher.
632
00:45:13,480 --> 00:45:17,120
Six metres. We've got
to be higher than that.
633
00:45:17,120 --> 00:45:19,160
We're now at eight metres.
634
00:45:19,160 --> 00:45:20,720
We've still got to go higher.
635
00:45:20,720 --> 00:45:24,840
Where are we at? Ten metres now?
A bit higher than that.
636
00:45:24,840 --> 00:45:27,840
We're still not at the height
of a sauropod yet.
637
00:45:27,840 --> 00:45:29,960
OK, we're getting there. Nearly.
638
00:45:30,960 --> 00:45:33,040
OK, fine.
639
00:45:33,040 --> 00:45:34,440
ELEPHANT ROARS
640
00:45:34,440 --> 00:45:37,400
So my head's now about 12 metres,
641
00:45:37,400 --> 00:45:40,840
which is about the height
of a four-storey building
642
00:45:40,840 --> 00:45:43,880
and also the height of a sauropod.
643
00:45:43,880 --> 00:45:47,120
The thing is, on the
end of a nine-metre neck,
644
00:45:47,120 --> 00:45:50,720
this is the skull of a sauropod.
645
00:45:50,720 --> 00:45:53,320
It seems quite small.
646
00:45:53,320 --> 00:45:57,000
But the point was that this had to b
manoeuvrable and nimble
647
00:45:57,000 --> 00:45:59,600
to get right up at
that high-level foliage.
648
00:46:01,800 --> 00:46:06,280
Sauropods were like nothing else
the planet had ever seen.
649
00:46:06,280 --> 00:46:09,800
They weighed more than ten times
an African elephant.
650
00:46:11,000 --> 00:46:15,720
Now, Butch here eats about 90kg
of foliage every day,
651
00:46:15,720 --> 00:46:17,840
which is roughly about that much hay
652
00:46:17,840 --> 00:46:19,640
But scientists have estimated
653
00:46:19,640 --> 00:46:24,760
that sauropods ate about
1,500kg of hay every day.
654
00:46:24,760 --> 00:46:27,840
In other words,
about 20 times that daily diet.
655
00:46:27,840 --> 00:46:30,880
Or 50 bales of hay.
656
00:46:30,880 --> 00:46:34,960
Now if you imagine you've got herds
of about 30 sauropods,
657
00:46:34,960 --> 00:46:37,320
much bigger than these beasts here,
658
00:46:37,320 --> 00:46:39,720
and you realise
that the plant kingdom
659
00:46:39,720 --> 00:46:42,320
was up against
the ultimate salad predator.
660
00:46:44,960 --> 00:46:48,200
150 million years ago,
661
00:46:48,200 --> 00:46:52,480
dinosaurs were stripping the land
of vast swathes of foliage.
662
00:46:52,480 --> 00:46:57,560
For the first time, the plant kingdo
was under serious attack
663
00:46:57,560 --> 00:46:59,520
from another dynasty.
664
00:47:01,360 --> 00:47:05,320
To fight back, plants began
to evolve a whole arsenal
665
00:47:05,320 --> 00:47:08,200
of defences
for their precious leaves.
666
00:47:10,240 --> 00:47:15,280
Here in California, we can see
just how intense this arms race was
667
00:47:15,280 --> 00:47:18,960
in one of the world's
most unusual gardens.
668
00:47:18,960 --> 00:47:24,680
It's full of a group of bizarre and
extremely rare plants called cycads
669
00:47:24,680 --> 00:47:29,200
but once, they made up a quarter
of all plants on Earth.
670
00:47:34,040 --> 00:47:35,600
This is incredible.
671
00:47:36,760 --> 00:47:40,720
Exactly the kind of place you'd
expect a dinosaur just to pop out.
672
00:47:43,520 --> 00:47:46,960
To stave off attack from
those ravenous dinosaurs,
673
00:47:46,960 --> 00:47:49,800
cycads developed
some clever lines of defence,
674
00:47:49,800 --> 00:47:52,960
the most obvious
being physical weapons
675
00:47:52,960 --> 00:47:57,040
like needles and spikes and...
Agh! These are vicious.
676
00:47:57,040 --> 00:48:01,400
The main point was to make leaves
as painful as possible to eat.
677
00:48:08,600 --> 00:48:12,960
These defences came
in all shapes and sizes.
678
00:48:15,520 --> 00:48:20,080
And some plants also spiced
things up with chemical weapons.
679
00:48:25,080 --> 00:48:27,760
This is a Trapps Valley cycad
from South Africa,
680
00:48:27,760 --> 00:48:31,360
but it's pretty typical in that
the leaves contain a nerve agent
681
00:48:31,360 --> 00:48:34,480
that if you ingest it,
it causes vomiting, diarrhoea,
682
00:48:34,480 --> 00:48:35,840
paralysis of the limbs
683
00:48:35,840 --> 00:48:37,720
and then, of course, death.
684
00:48:37,720 --> 00:48:40,280
Obviously I'm not going
to eat one of the leaves,
685
00:48:40,280 --> 00:48:42,720
but I can eat a plant
whose ancestors emerged
686
00:48:42,720 --> 00:48:44,520
around the time of the dinosaurs
687
00:48:44,520 --> 00:48:47,280
and who also have a chemical weapon
and that is...
688
00:48:48,440 --> 00:48:50,120
..a chilli.
689
00:48:50,120 --> 00:48:53,040
n particular, a habaneros chilli...
690
00:48:54,080 --> 00:48:57,360
...which is supposed to be one of
the most powerful in the world.
691
00:48:59,720 --> 00:49:02,240
There's a chemical in here
called capsicum...
692
00:49:02,240 --> 00:49:05,400
that is contained in the fruit.
693
00:49:07,200 --> 00:49:09,600
And that essentially is a toxin.
694
00:49:10,600 --> 00:49:12,440
COUGHS AND LAUGHS
695
00:49:13,440 --> 00:49:14,680
Agh!
696
00:49:14,680 --> 00:49:15,840
EXHALES
697
00:49:17,440 --> 00:49:20,680
Which is, at this precise moment,
698
00:49:20,680 --> 00:49:24,680
burning and inflaming
all of my mouth.
699
00:49:24,680 --> 00:49:26,080
Oh, my gosh!
700
00:49:30,400 --> 00:49:33,680
The thing is,
the toxins in the cycads were...
701
00:49:33,680 --> 00:49:37,280
they were far more powerful
even than the chillis.
702
00:49:37,280 --> 00:49:38,960
Oh, my gosh!
703
00:49:38,960 --> 00:49:43,200
So you can imagine what...the
dinosaurs would have had to endure.
704
00:49:43,200 --> 00:49:46,720
Oh, my...
I'm going to have to...
705
00:49:51,520 --> 00:49:52,960
Ah!
706
00:49:54,080 --> 00:49:56,360
Can't even say how sore that is!
707
00:49:59,640 --> 00:50:01,640
Mmmm.
708
00:50:03,000 --> 00:50:05,240
Eat a chilli, they said.
709
00:50:06,200 --> 00:50:08,200
It'll be funny, they said.
710
00:50:09,440 --> 00:50:11,640
You know what? Forget about cycads.
711
00:50:11,640 --> 00:50:14,720
That could have brought down
a 70-tonne sauropod.
712
00:50:18,600 --> 00:50:21,240
And the arms race didn't stop there.
713
00:50:21,240 --> 00:50:24,320
Plants evolved a new tactic.
714
00:50:25,640 --> 00:50:30,680
Not so much a line of defence
as a line of communication.
715
00:50:34,960 --> 00:50:37,960
We know that when
some plants are attacked
716
00:50:37,960 --> 00:50:42,120
they activate a quick-acting
toxin that deters herbivores.
717
00:50:43,200 --> 00:50:47,600
Now we're discovering that
this defence goes even further,
718
00:50:47,600 --> 00:50:50,520
because plants can actually
warn other plants
719
00:50:50,520 --> 00:50:52,600
that a herbivore is eating them.
720
00:50:56,840 --> 00:51:00,200
And at last,
scientists here at Exeter University
721
00:51:00,200 --> 00:51:04,080
are beginning to listen in
to this hidden conversation.
722
00:51:08,080 --> 00:51:10,920
They're finding that
when plants are attacked,
723
00:51:10,920 --> 00:51:14,200
they also release an unseen gas
from their leaves.
724
00:51:15,200 --> 00:51:17,840
What it does is extraordinary.
725
00:51:19,520 --> 00:51:23,280
And this will be the first time
it's been captured on film
726
00:51:23,280 --> 00:51:25,840
using specialist imagery.
727
00:51:25,840 --> 00:51:30,080
These two Arabidopsis plants are
being put inside a chamber.
728
00:51:32,240 --> 00:51:35,440
A third plant is then cut
to mimic an attack.
729
00:51:41,680 --> 00:51:44,760
It's added to the undamaged plants.
730
00:51:48,200 --> 00:51:50,120
The chamber is sealed.
731
00:51:59,920 --> 00:52:03,040
The plant leaves are now
releasing the gas.
732
00:52:05,200 --> 00:52:09,520
As they do so, their biological
activity can be seen changing.
733
00:52:15,160 --> 00:52:18,360
Something remarkable happens.
734
00:52:18,360 --> 00:52:22,000
The gas triggers a change
in the biological activity
735
00:52:22,000 --> 00:52:23,960
in the two neighbouring plants.
736
00:52:29,160 --> 00:52:33,640
They have detected the message
warning them to protect themselves.
737
00:52:42,360 --> 00:52:45,840
Scientists don't know all the detail
of this plant language,
738
00:52:45,840 --> 00:52:50,960
but increasingly they believe
there's a chatter between
plants all around us.
739
00:52:53,760 --> 00:52:57,280
I think most people assume that
plants lead a rather passive life.
740
00:52:57,280 --> 00:53:00,200
That they're static and unresponsive
741
00:53:00,200 --> 00:53:01,640
That's just not true.
742
00:53:01,640 --> 00:53:05,480
In reality they move, they sense,
they communicate.
743
00:53:05,480 --> 00:53:08,760
It's almost as if they show
a kind of intelligence.
744
00:53:12,800 --> 00:53:17,120
For 200 million years,
the dinosaurs and the plants
745
00:53:17,120 --> 00:53:21,200
were locked in a titanic
evolutionary battle,
746
00:53:21,200 --> 00:53:25,080
each trying to gain the upper hand.
747
00:53:26,640 --> 00:53:30,800
But it was now that some plants
played their trump card.
748
00:53:39,200 --> 00:53:43,120
They used wood to grow
taller and taller.
749
00:53:45,360 --> 00:53:50,600
In California's Sierra Nevada,
I'm about to find out just how tall.
750
00:53:53,520 --> 00:53:57,760
To do that, I need the help
of biologist Jim Spickler.
751
00:54:00,720 --> 00:54:02,640
I'm as ready as I'll ever be.
752
00:54:02,640 --> 00:54:05,400
Take your time. We've got time.
I was going to, absolutely.
753
00:54:12,840 --> 00:54:16,880
This is the grandest example
of them all.
754
00:54:16,880 --> 00:54:19,120
The giant sequoia.
755
00:54:20,120 --> 00:54:23,440
What you see is just impossible
for your mind to process.
756
00:54:23,440 --> 00:54:26,840
The scale is so large.
It's extraordinary.
757
00:54:26,840 --> 00:54:29,680
I feel as if I'm in
Lord of the Rings.
758
00:54:29,680 --> 00:54:31,760
GRUNTING
759
00:54:49,760 --> 00:54:51,880
What a great tree!
760
00:54:53,960 --> 00:54:56,560
70 million years ago,
761
00:54:56,560 --> 00:55:01,840
the ancestors of this type of tree,
the conifers, got ever taller.
762
00:55:03,400 --> 00:55:07,000
This was the ultimate
in plant construction.
763
00:55:08,040 --> 00:55:10,240
Conifers like the giant sequoias
764
00:55:10,240 --> 00:55:13,080
raised their precious leaves
out of reach.
765
00:55:14,760 --> 00:55:19,320
The dinosaurs were no longer
the biggest organisms on Earth.
766
00:55:19,320 --> 00:55:22,960
That title had been
well and truly won back
767
00:55:22,960 --> 00:55:25,760
by these giants of the plant kingdom
768
00:55:28,360 --> 00:55:30,960
This is so tall,
but I've still got...
769
00:55:30,960 --> 00:55:33,360
I don't know,
another third to go.
770
00:55:33,360 --> 00:55:36,520
By using wood to grow
really tall like this,
771
00:55:36,520 --> 00:55:39,360
it gave trees another
advantage over plants
772
00:55:39,360 --> 00:55:42,760
because it allowed them first pick
of the sun's strongest rays.
773
00:55:42,760 --> 00:55:47,440
The thing is, of course,
for plants, light means success.
774
00:55:51,440 --> 00:55:56,000
If you had a satellite image of the
dinosaur era 70 million years ago,
775
00:55:56,000 --> 00:55:59,440
you'd see the Earth like
it had never been before
776
00:55:59,440 --> 00:56:01,520
and never would be again.
777
00:56:03,000 --> 00:56:07,160
The climate was so warm
the poles had no ice.
778
00:56:07,160 --> 00:56:10,240
Instead they were covered
with conifers -
779
00:56:10,240 --> 00:56:12,520
a vast polar forest.
780
00:56:14,280 --> 00:56:18,120
And the mighty sequoia trees
were not just found
781
00:56:18,120 --> 00:56:21,880
in small areas of the Sierra Nevada,
as they are today.
782
00:56:21,880 --> 00:56:23,600
They were global.
783
00:56:23,600 --> 00:56:28,520
Stretching along the Pacific coast
and as far south as Australia.
784
00:56:30,720 --> 00:56:34,720
How far are we from the top, then?
We're getting close.
785
00:56:34,720 --> 00:56:36,800
GRUNTING
786
00:56:37,880 --> 00:56:39,440
Ah! It's extraordinary.
787
00:56:44,000 --> 00:56:47,200
This is it.
This is the top of the tree.
788
00:56:47,200 --> 00:56:48,640
Ooh!
789
00:56:49,920 --> 00:56:51,840
Unbelievable!
790
00:56:56,880 --> 00:57:01,520
It's staggering to think that using
just a gas, carbon dioxide,
791
00:57:01,520 --> 00:57:04,240
and a liquid, water,
792
00:57:04,240 --> 00:57:07,640
together with light energy
from beyond our world,
793
00:57:07,640 --> 00:57:13,840
you can construct a cathedral
of wood 90 metres tall.
794
00:57:20,640 --> 00:57:22,840
Since they first appeared,
795
00:57:22,840 --> 00:57:26,160
plants and their ancestors have
revolutionised our planet.
796
00:57:28,440 --> 00:57:31,760
They created oxygen
for the atmosphere...
797
00:57:34,000 --> 00:57:37,280
..which would allow them
to conquer the land
798
00:57:37,280 --> 00:57:39,560
and transform rock into soil,
799
00:57:39,560 --> 00:57:44,000
in turn fuelling the explosion
of all life.
800
00:57:45,320 --> 00:57:50,680
From a barren alien planet,
plants have made a living Earth.
801
00:57:50,680 --> 00:57:55,800
And left on its own, the world
would have continued like this,
802
00:57:55,800 --> 00:58:00,120
dominated by large dinosaurs
and endless forests.
803
00:58:00,120 --> 00:58:02,080
But 65 million years ago,
804
00:58:02,080 --> 00:58:04,400
something happened
that would change everything.
805
00:58:04,400 --> 00:58:07,200
A chance event that would have
dramatic consequences
806
00:58:07,200 --> 00:58:09,560
not just for plants but for all life
807
00:58:09,560 --> 00:58:13,800
And it would originate not on Earth,
but in outer space.
808
00:58:13,800 --> 00:58:15,440
WHOOSH
809
00:58:15,440 --> 00:58:17,280
EXPLOSIONS
810
00:58:22,000 --> 00:58:24,880
The asteroid would kill off
the dinosaurs.
811
00:58:24,880 --> 00:58:27,840
And the next chapter
would see the triumph
812
00:58:27,840 --> 00:58:31,400
of a whole new group of plants...
813
00:58:32,720 --> 00:58:36,320
...flowers transformed the bond
between animal and plant,
814
00:58:36,320 --> 00:58:40,600
even sculpting
the very planet itself.
815
00:58:40,600 --> 00:58:45,880
Above all, plants
would drive our human story.
816
00:58:45,880 --> 00:58:49,000
But all that was still to come.
817
00:59:09,440 --> 00:59:13,400
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