Wonders of Life (2013–…): Season 1, Episode 3 - Endless Forms Most Beautiful - full transcript
The universe is almost entirely devoid of life. Earth, the planet we call home, seems to defy the laws of physics. It is teeming with life in all colors, shapes and sizes. No-one knows for sure how many different species are alive right now, our best guess is close to 8.7 million. In this film, Professor Brian Cox asks how, from a lifeless cosmos ruled by the laws of physics and chemistry, it is possible that a planet can produce so much wonderful, varied biology. It's an epic journey through time that begins with Brian undertaking a species count in the cloud forests of Madagascar. Here, creatures exist that are unique to this isolated Indian Ocean island. He searches for clues to how species have become so diverse by considering the chemistry of a lion, tracing their molecular connection to the heavens with a visit to the Southern African Large Telescope. Witnessing the ancient formation of stars Brian follows carbon, life's most precious ingredient, as it is captured by the living world. From plants to insects, through grazing herds, all the way up to Africa's big cats, Brian follows carbon as it passes through the food chain. This leads him to the one carbon rich molecule that controls it all: DNA, the blue print for all living things. On the ancient Karoo plains Brian discovers how once DNA arrived it was inevitably changed. He shows that the universe itself plays an important part in shaping this molecule. Finally he returns to Madagascar to search for its most famous inhabitants: lemurs. There are over 90 different species across the country, but perhaps one of the most bizarre is known locally as the aye-aye. Being nocturnal and living in some of the densest, most mountainous terrain makes them incredibly difficult to find. Yet Brian is determined to find one because they hold one of the best demonstrations of how DNA is shaped by the environment. For Brian the aye-aye holds the key to understanding why we find ourselves on such a rich, varied and complex living world.
In 2009, a new species of spider
was identified.
A spider with superpowers.
It was named exactly 150 years
after the publication of Darwin's
On The Origin Of Species,
in which he explained why life on
Earth is so diverse and so complex.
Darwin's theory of evolution
by natural selection
was built on the work of naturalists
who were discovering
thousands of new species
across the world.
That process of finding species
new to science and naming them
continues to this day.
And it's recognised in the name
of this newly discovered arachnid.
Darwin's bark spider.
The spider occupies a unique niche.
It can hunt
where no other spider can.
That spider creates the largest webs
found anywhere on Earth.
In order to do that, it has to
produce the strongest silk
of any spider. They can span over
25 metres across lakes and rivers.
And actually,
no-one knows how they get their webs
across such a large distance.
But Darwin's bark spider
is one of thousands of unique
species of animals and plants
that you find in Madagascar.
The rainforests here are
one of the most bio-diverse places
on the planet.
And each year, more discoveries
are made
as researchers try to understand
why this tiny corner of the universe
is so prolific.
All of these living things were
found within a five-minute walk
of this field station.
And the diversity is remarkable.
There's a chameleon there.
These are orchids.
This big green leaf
is a traveller's palm.
There are four species of mushroom
on that branch alone.
Across Madagascar, there are over
14,000 species of plants,
there are hundreds of species
of mammals, birds and reptiles
and over 90% of them
are unique to this island.
How could it be
that so many diverse living things,
so beautifully adapted to their
environment, could've emerged
from a universe that's governed
by a simple set of natural laws?
The fact that we know the answer
to that question
is one of the greatest achievements
in science.
In this film, I want to explore how
these endless forms, most beautiful,
have emerged from a lifeless cosmos.
Africa. A whole continent
full of creatures utterly different
from those in Madagascar.
But the diversity of life
doesn't stop at what you see.
Because within each individual
lies another world of complexity.
This, believe it or not,
is the top predator in Africa.
Or she will be when she's older.
She's only about
eight weeks old now.
Her body is built from a host
of different molecules
and by far the most diverse
group are known as proteins.
We can see the proteins here.
Those claws,
so vital for a lion's survival,
are made of a protein
called keratin.
Her eyes, also absolutely vital
for her survival,
have a protein called opsin which
is bound to a pigment
to make structures called rhodopsins
which allow her to see in colour
and also to allow her to see very
well at night when she's hunting.
There are also proteins
in her muscles...
..myosin and actin, which are the
things that allow her to run away.
The proteins in a lion
come in countless different forms.
But they all share something
in common.
A backbone of carbon.
An atom that's able to form
long, complex molecules.
Of all the 92 elements,
there really is only one
which has that appetite for bonding
its four electrons -
to share them with other molecules.
Carbon will share those electrons
with nitrogen, oxygen, hydrogen,
and critically, with other carbons,
to build up these immensely complex
chains,
the amino acids and the proteins
which are
the building blocks of life.
So to understand our planet's
endless diversity,
we must begin by considering
this life-giving element.
I've got a few scratches now because
of you! Because of your proteins!
After all, to build a lion,
you must first build carbon.
And that's a story that stretches
back to a time
long before there were even stars
in the universe.
13.5 billion years ago,
just a few hundred million years
after the Big Bang,
the universe was a carbon-free zone.
An infinite, sterile gloom
of hydrogen and helium clouds.
Until, one day,
those vast clouds began to collapse
under the force of gravity.
Long before the solar system,
Earth or life existed...
..the first stars were born.
The birth of the first stars
did much more than illuminate
the universe,
because that set in train
a sequence of events
which is necessary for the existence
of life in the universe.
And we can still see that process
playing out in the universe today.
This is the brand-new
South African Large Telescope.
TECHNICIAN: Number three amps,
gear right, gear box.
Its mirror is 11 metres wide,
making it the largest optical
telescope
in the southern hemisphere.
And it recently helped to pin down
what's happening in an object
some 650 million light years
from Earth.
This beautiful, almost lifelike
system is known simply as the Bird.
It's the spectacular result
of what we used to think
was two galaxies colliding.
It's events happening
in the head of the Bird
that are most interesting from a
perspective of life in the universe.
Because the head is formed
by another galaxy,
a third galaxy, an island
of billions and billions of stars,
colliding with two galaxies
that form the wings and the body
at a speed of around
250 miles a second.
The turbulence, the disturbance,
that that creates is causing
many new stars to be formed.
These stars begin their lives
by burning hydrogen,
to produce ever more helium.
But as they age, as the hydrogen
runs out, they turn to this helium.
The temperature at their core rises
increasing the chances
of three helium nuclei
fusing together
to form a new element - carbon.
That process has been going on
for almost the entire
history of the universe,
back 13 billion years,
and it's the formation of stars
that is the vital first step
in the formation of life,
because stars produce
the heavy elements in the universe
including carbon.
From the universe's earliest times,
carbon has been created
inside ageing stars.
And over time,
this carbon has built up,
drifting through the cosmos
as dust...
..until some of it was caught up
in the formation
of a planet called Earth.
And it's here that we can see this
ancient carbon
brought vividly to life.
Today, the universe is old enough
that countless stars
have lived and died.
So, there's been plenty of time
to synthesise
the primordial hydrogen and helium
into the heavy elements.
The question now is, how does that
carbon get into the web of life?
Well, today,
it enters via one ingredient
and I'm going to measure it
using this balloon.
The ingredient is carbon dioxide,
which plays a key role
in photosynthesis.
Each night the carbon dioxide
concentration increases,
filling the air around the leaves
at the top of the trees.
This balloon has a carbon dioxide
monitor in it
which is going to measure the change
in the levels of CO2
at the top of the forest canopy
as night turns to day.
As the sun rises,
the trees begin to photosynthesise.
At 6pm last night,
just after sunset,
the concentration
was around 350 parts per million.
Around 10pm, around four hours after
sunset,
the concentration had risen to
about 400 parts per million.
Now, at about midday,
the concentration's back down
to about 345 parts per million.
So that's a variation over a period
of about 18 hours of 10%
in the concentration
of carbon dioxide,
just in that piece of atmosphere
at the top of the forest canopy.
What you are seeing there
is photosynthesis in action.
Every day, across the planet,
photosynthesis uses sunlight
to turn carbon dioxide and water
into simple sugars.
The overwhelming majority
of the carbon
is locked up inside long chains
of sugar molecules
called cellulose and lignin.
Lignin is the stuff that gives
wood its strength.
So, in this form, remember,
that is most of it,
it is very difficult indeed
for animals to access.
For the energy and nutrients locked
away in these long carbon chains
to move through the food web,
they must be broken down.
The best place to see that process
in action is out on the open plain.
It's one vast larder for all
manner of organisms.
By far the most effective
harvester of carbon
is actually one of the smallest
creatures on the savanna.
Termites are social insects,
working together to form
a characteristic sight,
seen all over the bush.
That's a termite mound. Actually,
it's the tip of the iceberg.
The termite city extends
way beyond that underground.
And its function is fascinating.
It's essentially
an air-conditioning system.
What it does is maintain specific
conditions inside the mound -
the conditions of the rainforest.
When the termites first colonised
the savanna 30 million years ago,
they brought the rainforest
with them
to support a form of life that was
already wonderfully adapted
to living off dead wood.
This is what these termite mounds
are all about.
Can you see those structures, those
white honeycomb-like structures?
Those are called fungal combs.
They're wood pulp and possibly
bits of dead grass
that the termites bring in and build
into that structure.
And the reason the conditions have
to be the same as the rainforest
is because they grow a particular
genus of fungus called termitomyces
around those honeycombs.
The job of that fungus
is to break down the lignin
and cellulose inside the wood
and convert it into a form that the
termites can eat,
which you can see there,
the little white nodules,
just present
on the honeycomb structure.
The termites lack the enzymes to
break down the wood efficiently,
so they have become farmers,
tending to one giant social stomach.
There's a very intense relationship
between the termites and the fungus.
You don't find that fungus anywhere
else in the world
as far as we know,
other than inside termite mounds.
It's thought that up to 90%
of the carbon locked up in lignin
in this part of Africa is released
back into the food chain again,
solely by those termites
and that fungus.
So the termites deal with
most of the lignin,
but that still leaves a vast store
of carbon in the form of cellulose.
Across Africa, herds of mammals
graze on grasses and leaves,
turning the cellulose into meat.
Many are a type of mammal
known as a ruminant...
..the largest of which is one of the
easiest animals to spot on safari.
There's a giraffe there as well.
Giraffes live off a diet similar
to termites. They eat cellulose.
Primarily
the tops of the acacia trees
that you see scattering
the African savanna.
And they face that same problem,
they've got to break those
difficult carbon bonds down
and they've come up with a very
similar solution
which is to cultivate
bacteria and fungi.
But they do it inside their stomachs
and ruminants like giraffes
have had to build a very complex
system in order to do that.
They've got four stomachs,
one of them contains their culture
of bacteria and fungi,
and they allow them to digest
that difficult cellulose.
Even with all this hardware,
ruminants must feed
for over two thirds of the day.
But there are other creatures here
that have found a short cut,
after all,
if plant fibres are hard to digest,
why not let someone else do the work
and simply steal a meal?
It's coming for us.
Oh, my God...
ENGINE STARTS
Look what we've just found.
We were out looking for giraffe
this morning,
and we found about ten of them
over there,
but in looking for the giraffe,
we've just found a leopard.
This is one of the top predators
out here.
He's got very little to fear apart
from other leopards and maybe lions.
He's having a good look,
he certainly doesn't care about us.
He's around two years old
and at the moment,
he doesn't have his own territory,
he's too young for that.
So he's lying low.
He'll have to make about two kills
a week, to stay in good condition.
So, maybe he'll catch
an impala every three to four days,
and he's obviously doing that.
Because, look at him!
He's looking for protein.
He likes your boom. >
And I'm a little bit worried,
cos I'm protein!
Oh, wow.
He's after your boom, George. >
He's coming really close to us
because he's after
the sound man's boom pole.
Which is...oh!
That's incredible.
RUMBLING MICROPHONE DISTORTION
I just...
HE LAUGHS
He's taken it...
From its origin
in the death of stars...
..its capture by plants...
..through insects,
mammals and on.
The carbon cycle is
the real circle of life.
Out there tonight, the relentless
recycling of carbon
through the food chain
will continue.
As night falls, you can almost
sense it - the change in the sounds
and the atmosphere.
Some will die,
so that others can live,
as carbon leaps
from branch to branch
across the great tree of life.
And guiding it along its way is just
one very special form of chemistry.
Every living thing is just
a temporary home
for carbon atoms that existed long
before there was life on Earth
and will exist long
after Africa and Earth are gone.
But, the pattern of life,
the information needed
to build a zebra, or a tree,
or a human being or a lion persists.
It's passed on from generation
to generation, in a molecule.
A helical molecule with
a backbone of carbon called DNA.
MUSIC: "Atmosphere"
by Joy Division
There was a time
when Earth appeared empty.
♪ Walk
♪ In silence
♪ Don't walk away
♪ In silence... ♪
Yet despite appearances,
3.8 billion years ago
life was already under way,
in the form of tiny living specks
that probably all shared
the same biochemistry.
We know that every living
thing on the planet today -
so every piece of food you eat,
every animal you've seen,
everyone you've ever known
or will know,
in fact every living thing that WILL
ever exist on this planet -
was descended from that one speck.
♪ Walk
♪ In silence... ♪
We call it the last universal
common ancestor, or LUCA.
So, just as the universe
had its origin at the Big Bang,
all life on this planet
had its origin in that one moment.
Less than a billion years
after its formation,
there was already life on Earth.
It's possible that some of it used
biochemistry
utterly different from the life
we see today.
If so, it has long been extinct.
It's also possible that the first
life may not have been cellular -
just living chemistry in the porous
rocks of some ancient ocean.
We're not sure,
but what's certain is that one day,
a population of organisms showed up
with biochemistry that we WOULD
recognise.
This was LUCA.
The first expression
of a form of life that would in time
throw up a group of humans who left
their mark in this part of Africa.
Now, we don't know what
LUCA looked like,
we don't know precisely where it
lived or how it lived.
But we do know this.
If you start to trace my ancestral
line back to my parents,
to their parents, to their parents,
to their parents,
all the way back
through geological timescales
over hundreds of thousands
of millions and billions of years,
there will be an unbroken line
from me all the way back to LUCA.
We know that, because every living
thing on the planet today
shares the same biochemistry.
We all have DNA. It's made of the
same bases, A, C, T and G.
They code for the same amino acids.
Those amino acids build the same
proteins, which do very
similar jobs, whether you're a
plant, a bacterium, or a
bipedal hominid, like me.
So all life uses the same
fundamental biology...
..those four bases, A, C, T and G,
which code for just 20 amino acids,
which in turn build each
and every one of life's proteins.
Be you bacteria, plant,
bug or beast,
your design comes from your DNA.
So it's this molecule that must hold
the key to understanding why
life today is so diverse.
We now know that the answer
to the question,
"Why is life on Earth so varied?"
is actually the answer to
the question, "Why is the DNA
molecule itself so varied?"
What are the natural processes that
cause the structure of DNA to
change?
Well, part of the answer actually
doesn't lie on Earth at all.
It lies up there amongst the stars.
And I can show you what I mean,
using this,
which is a cloud chamber, a piece
of apparatus that has a unique place
in the history of physics.
I'm going to cool it down using dry
ice, frozen carbon dioxide,
just below -70 degrees Celsius.
I'll put the top on.
HIGH-PITCHED SQUEAKING
Hear that?
That's the metal at the bottom
of the tank cooling down very
rapidly to -70.
The cloud chamber works by having
a super-saturated
vapour of alcohol
inside the chamber.
Plenty on there...
Now, I want to get that alcohol,
I want to boil it off,
to get the vapour into the chamber.
So I'm going to put a hot water
bottle on top.
This is the first genuine particle
physics detector.
It's the piece of apparatus that
first saw antimatter.
And it really does consist
only of a fish tank, some alcohol,
a bit of paper,
and a hot water bottle.
There, look at that.
Do you see that?
Cloud vapour trail.
That's a cosmic ray.
That was initiated by a particle,
probably a proton,
that hit the Earth's atmosphere.
It almost certainly originated
outside our solar system
and was accelerated by the magnetic
fields of our galaxy.
It may even have
begun its life BEYOND our galaxy.
Now, imagine if one of those hits
the DNA of a living thing.
What that will do is cause
a mutation.
That mutation may be detrimental,
or,
very, very occasionally it might be
beneficial.
And I think it's quite wonderful
to imagine that maybe
one of the key mutations that was
selected for over the millennia
that led to some trait in ME
was caused by some particle
that began its life perhaps
in a massive supernova explosion,
perhaps outside our galaxy
and went
and hit the DNA of something
and caused some
kind of beneficial mutation.
We don't know,
but you can dream, can't you?
Mutations are an inevitable part of
living on a planet like Earth.
They're the first hint at how
DNA and the genes
that code for every living thing
change from generation to
generation.
Mutations are the spring
from which innovation in the living
world flows.
But cosmic rays are not the only way
in which DNA can be altered.
There's natural background
radiation from the rocks,
there's the action of chemicals
and free radicals.
There can be errors
when the code is copied.
And then all those changes can be
shuffled by sex, and indeed
whole pieces of the code can be
transferred from species to species.
So, bit by bit, in tiny steps
from generation to generation,
the code is constantly
randomly changing.
Now, whilst there's no doubt that
random mutation does alter DNA,
evolution is anything but random.
It can't be,
because the chances of something
with DNA as complex as this
appearing by luck alone
are vanishingly small.
Imagine you just changed one
position in the code at random,
a random mutation.
There are four letters,
A, T, C and G,
so there are four possible
combinations.
If there are two places in the code,
there are four combinations for each
one. So that makes 16.
If there are three,
then there are 64 possibilities.
By the time you get to a code
with 150 letters in it,
then there are more possible
combinations in the code
than there are atoms in the
observable universe.
Now, a hippo has a code
with around three billion
different letters.
So the number of combinations
of those letters, the chances of
producing that code at random, are
absolutely, infinitesimally small.
It's impossible.
So there must be a non-random
element to evolution...
..a natural process,
which greatly restricts this
universe of possibilities,
and shapes the outcome.
We call it natural selection.
And to see it in action,
let's return to where we began
on the island of Madagascar.
Around 65 million years ago,
a group of seafarers were nearing
the end of a long
journey across the Indian Ocean.
These were accidental travellers,
a group of creatures from Africa,
trapped on a natural raft
and carried by the ocean currents.
The land they found was
virgin green territory.
Plants, insects, reptiles and birds
had established themselves,
but there were
none of their own kind.
They were caught up in a saga that
tells of the great
shifting of Earth's
continental plates.
It's impossible to understand
the diversity of life on Earth today
without understanding the
shifting geography of our planet.
Here's a map of Earth's southern
hemisphere as it was
150 million years ago, and you see
it's dominated by a single landmass
called Gondwana.
And then, 90 million years ago,
Gondwana had begun to break up,
to separate,
into something that looks quite
recognisably like Africa,
and these two islands,
Madagascar and India.
Now, subsequently India has
drifted northwards
and bumped into Eurasia,
raising the Himalayas.
But, crucially,
Madagascar has remained isolated.
It's been an island surrounded by
ocean for almost 90 million years.
So, when those seafarers
arrived on their raft of trees
and twigs and leaves,
they had a blank canvas -
two, three,
maybe even a single pregnant
individual
had a whole island to roam across.
And over 65 million years, they have
blossomed into hundreds and
thousands of individuals, and become
Madagascar's most iconic animals.
Finding the descendants of those
ancient mariners is not easy.
But local guide Joseph has been
tracking them for years.
And he's going to help me find them.
There at the top of the tree
is an indri,
which is the largest
lemur in Madagascar.
He's just sat there watching us
quietly at the moment.
This lemur here is a very
special lemur.
He has a name, he's called David.
After Sir David Attenborough.
LEMUR SCREECHES
LEMUR SCREECHES
Now, we can only do this because
Joseph has spent
a lot of time with these lemurs.
So they trust him. And therefore,
it seems, they trust me.
Its enormous hands!
The reason, it's thought, that we
find lemurs here in Madagascar
and Madagascar alone
is because there are no simians,
there are no chimpanzees,
none of my ancestral family,
dating back tens of millions
of years, to out-compete them.
So what's thought to have happened
is that around 65 million years ago
one of the lemur's ancestors
managed to sail across the
Mozambique Channel, and landed here.
There were none of those
competitors here,
and so the lemurs have
flourished ever since.
There are now over 90 species
of lemur, or subspecies,
in Madagascar,
and no species of my lineage,
the simians.
LEMUR SCREECHES
Over a vast sweep of time,
the lemurs have diversified
to fill all manner of different
habitats.
From the arid, spiny
forests of the south...
..to the rocky canyons in the north,
there is something about this island
that is allowing the lemur's DNA
to change in the most amazing ways.
We're on the hunt for an aye-aye,
the most closely related of all
the surviving lemurs
to their common ancestor.
Oh, yes...
Oh, yeah.
Just shone the light up,
and we saw these absolutely...
Two bright red eyes, shining out.
She's very high up at the moment.
Don't want to lose
sight of her in this forest,
which is very dark and dense.
The team have located a female
aye-aye, and her son.
They want to attach radio collars
to track their movements,
and better understand how far
they range through these forests.
But first, they must sedate them
with a dart.
He's waiting for it to come down
low enough to get that clean shot -
I mean, how you get a clean shot in
this I have no idea.
After two hours of traipsing through
the treacherous forest,
the aye-ayes remain at large.
INDISTINCT CHATTER
Well, here is the aye-aye that was
tranquillised last night.
They finally got her about half
an hour after we left.
I think it was probably
because we were disturbing her.
Apparently as soon as we'd gone,
she came down the tree
and she was tranquillised.
And as you can see
she's pretty well sedated now,
which is fortunate for me
because she has certain adaptations
that I wouldn't like to be deployed.
You can see there her teeth.
Her teeth are very
unusual for a primate -
in fact, unique,
because they carry on growing,
so she's much
more like a rodent in that respect.
And that's so
she can gnaw into wood.
You see, aye-ayes have filled
a unique niche on Madagascar.
It's a niche that's filled by
woodpeckers in many other areas of
the world.
What she does is she feeds on grubs
and bugs inside trees,
and to do that, she has several
unique adaptations
of which her teeth are one.
The most startling is this
central finger here. It's bizarre.
It's got a ball
and socket joint, for a start,
so it has complete 360-degree
movement.
It feels to me almost
as if it's broken, but it isn't,
it's just, you can move it around
in any direction.
And she uses that finger initially
to tap on the trunk of the tree,
and then, listening to the echo from
that tapping, with these huge ears
she can detect where the grubs are.
And then, she gnaws through the wood
with those rodent-like teeth,
and then uses this finger again to
reach inside the hole
and get the bugs out.
So the question is, why?
How could an animal be so precisely
adapted to a particular lifestyle?
She's waking up now!
And the answer is natural
selection.
See, what must have happened is
way back,
when the ancestors of the
lemurs - the Lemuriformes -
arrived in Madagascar,
there must have been a mutation that
lengthened the middle finger ever
so slightly of one of those lemurs.
And that must have given it
an advantage.
That must have allowed it perhaps
to reach into little holes
and search for grubs.
There's some reason why that
lengthened middle finger
meant that that gene was more likely
to be passed to the next generation
and then down to
the next generation.
So that landscape of possibilities
is narrowed,
it's narrowed
because that gene persists.
And it's persisted now
for at least 40 million years,
because this species has been on
one branch of the tree of life now
for over 40 million years.
And so, over those years
that middle finger
has got more and more specialised.
Natural selection has allowed the
aye-aye's wonderfully mutated finger
to spread through the population.
And this same law applies
to all life.
If you have a mutation that helps
you in the struggle to survive,
you are more likely to leave
more offspring.
And in the next generation, that
mutation is more likely to survive.
So this animal is a beautiful
example, probably one
of the best in the world, of how the
sieve of natural selection produces
animals that are perfectly adapted
to live in their environment.
Now, there are many reasons to study
the aye-aye. But here's a good one.
In the 1970s, it was thought
the aye-aye was extinct.
Now, we know there are several
thousand in the forests
of Madagascar -
5,000, 6,000, 7,000,
certainly less than 10,000 -
but over the last 50 years,
50% of this forest has vanished.
This is an animal that's been around
as a species for over
40 million years.
So it's important to know
how these animals are doing,
and how they're surviving in this
diminishing habitat.
Whilst natural selection explains
why the aye-aye evolved,
it alone can't explain how a small
group of individuals, over 60
million years ago,
gave rise to over 90 different
species of lemur today.
But there is another form of life
that can offer us a clue.
Up here in the high forest canopy,
we're in a very different
environment to the one down there
on the forest floor.
It's a more arid environment,
it's almost like a desert.
It's exposed to the sun,
water is harder to come by.
And so, this is
a sea of different niches,
that are able to be occupied
and exploited by animals
that are different to the ones
you'll find down there on the floor.
So, in a very real sense, this is an
island, an island to be colonised.
And sure enough, there are settlers
to be found, even here.
You see that thing that looks like
a muddy ball there, on the branch?
Well, that's an ants' nest,
it's home to a species of
Crematogaster ants
that are unique not only to
Madagascar,
but to the forest canopy.
You see, what makes those ants
unique is that they can
build their own nests.
There are very few species of ants
that can do that.
So that is an island, that is
a niche,
and it's allowed that
species of ant to develop
because they're isolated
from the rest of the ecosystem.
And astonishingly,
within this niche,
another form of life new to science
has been discovered...
..a beetle that manages to
survive here unharmed by the ants.
How it does it is a mystery.
But what IS known is that this
particular species has only
ever been found inside these nests.
So, that really is its own
mini-ecosystem,
with species living in it
that are unique to that island.
We live on an ever-shifting,
dynamic world
that creates islands in abundance.
Earth's mountain ranges,
river valleys and canyons
all create islands for life.
And it's these islands
that those ancestors of the lemurs
found when they arrived
in Madagascar.
Empty niches, where populations
became isolated,
and over great swathes of time
involved into such wonderfully
diverse forms.
150 years on from the Origin
Of Species, the subtlety
and beauty of Darwin's insight is
still revealing itself to us.
It describes how our beautiful,
complex tree of life
has grown from a once desolate
universe.
The chemistry of carbon
allows for the existence of
a molecule that is able to replicate
itself, and pass information on
from generation to generation.
There can be random changes
in the structure of that molecule -
mutations - and they are tested
by their interaction with
the environment
and with living things.
The ones that pass that test
survive,
and the ones that fail that test
are lost.
The separation and isolation
of living things onto islands -
which may be physical,
like Madagascar,
or just the single branch of
a single tree -
results in speciation,
the explosion of living forms
highly specialised to occupy niches
within niches.
And this is the explanation
for the diversity of life on Earth.
"There is grandeur in this
view of life," as Darwin wrote,
and understanding how it happened
surely only adds to the wonder.
As precise as Einstein's theories
of relativity, and as profound
as thermodynamics,
Darwin has given us another
universal law.
Evolution by natural selection.
And if evolution is
the law on this island,
then it will apply
throughout the cosmos.
Which begs a big question.
Could there be other "trees of life
most beautiful" amongst the stars?
In 2011,
we discovered a rocky planet
orbiting around a distant star,
with daytime temperatures not too
dissimilar to those found on Earth.
Now, there must be millions
if not billions of such planets
out there in the universe,
and it's inconceivable to me
that none of them
will have trees of life as complex
or even more complex than our own.
But that doesn't devalue
the existence of OUR tree,
because our tree is unique.
It consists of thousands
of branches,
all interdependent
on thousands of others,
and the precise structure depends
on chance events, like the passage
of the lemurs across the ocean
65 million years ago.
So when you go outside tomorrow,
just take a look at a little
piece of your world.
A corner of your garden, or a park,
or even the grass that's
growing in a crack in the pavement.
Because there will be life there,
and it will be unique.
There will be nowhere like that
anywhere else in the universe.
And that makes our tree, from the
sturdiest branch to the most
fragile twig,
indescribably valuable.
MUSIC: "Underneath the Stars"
by Kate Rusby
♪ Underneath the stars you met me
♪ And underneath the stars
you left me
♪ I wonder if the stars regret me
♪ I'm sure they'd like me
if they only met me
♪ They come and go
of their own free will
♪ Go gently... ♪
Subtitles by Red Bee Media Ltd
was identified.
A spider with superpowers.
It was named exactly 150 years
after the publication of Darwin's
On The Origin Of Species,
in which he explained why life on
Earth is so diverse and so complex.
Darwin's theory of evolution
by natural selection
was built on the work of naturalists
who were discovering
thousands of new species
across the world.
That process of finding species
new to science and naming them
continues to this day.
And it's recognised in the name
of this newly discovered arachnid.
Darwin's bark spider.
The spider occupies a unique niche.
It can hunt
where no other spider can.
That spider creates the largest webs
found anywhere on Earth.
In order to do that, it has to
produce the strongest silk
of any spider. They can span over
25 metres across lakes and rivers.
And actually,
no-one knows how they get their webs
across such a large distance.
But Darwin's bark spider
is one of thousands of unique
species of animals and plants
that you find in Madagascar.
The rainforests here are
one of the most bio-diverse places
on the planet.
And each year, more discoveries
are made
as researchers try to understand
why this tiny corner of the universe
is so prolific.
All of these living things were
found within a five-minute walk
of this field station.
And the diversity is remarkable.
There's a chameleon there.
These are orchids.
This big green leaf
is a traveller's palm.
There are four species of mushroom
on that branch alone.
Across Madagascar, there are over
14,000 species of plants,
there are hundreds of species
of mammals, birds and reptiles
and over 90% of them
are unique to this island.
How could it be
that so many diverse living things,
so beautifully adapted to their
environment, could've emerged
from a universe that's governed
by a simple set of natural laws?
The fact that we know the answer
to that question
is one of the greatest achievements
in science.
In this film, I want to explore how
these endless forms, most beautiful,
have emerged from a lifeless cosmos.
Africa. A whole continent
full of creatures utterly different
from those in Madagascar.
But the diversity of life
doesn't stop at what you see.
Because within each individual
lies another world of complexity.
This, believe it or not,
is the top predator in Africa.
Or she will be when she's older.
She's only about
eight weeks old now.
Her body is built from a host
of different molecules
and by far the most diverse
group are known as proteins.
We can see the proteins here.
Those claws,
so vital for a lion's survival,
are made of a protein
called keratin.
Her eyes, also absolutely vital
for her survival,
have a protein called opsin which
is bound to a pigment
to make structures called rhodopsins
which allow her to see in colour
and also to allow her to see very
well at night when she's hunting.
There are also proteins
in her muscles...
..myosin and actin, which are the
things that allow her to run away.
The proteins in a lion
come in countless different forms.
But they all share something
in common.
A backbone of carbon.
An atom that's able to form
long, complex molecules.
Of all the 92 elements,
there really is only one
which has that appetite for bonding
its four electrons -
to share them with other molecules.
Carbon will share those electrons
with nitrogen, oxygen, hydrogen,
and critically, with other carbons,
to build up these immensely complex
chains,
the amino acids and the proteins
which are
the building blocks of life.
So to understand our planet's
endless diversity,
we must begin by considering
this life-giving element.
I've got a few scratches now because
of you! Because of your proteins!
After all, to build a lion,
you must first build carbon.
And that's a story that stretches
back to a time
long before there were even stars
in the universe.
13.5 billion years ago,
just a few hundred million years
after the Big Bang,
the universe was a carbon-free zone.
An infinite, sterile gloom
of hydrogen and helium clouds.
Until, one day,
those vast clouds began to collapse
under the force of gravity.
Long before the solar system,
Earth or life existed...
..the first stars were born.
The birth of the first stars
did much more than illuminate
the universe,
because that set in train
a sequence of events
which is necessary for the existence
of life in the universe.
And we can still see that process
playing out in the universe today.
This is the brand-new
South African Large Telescope.
TECHNICIAN: Number three amps,
gear right, gear box.
Its mirror is 11 metres wide,
making it the largest optical
telescope
in the southern hemisphere.
And it recently helped to pin down
what's happening in an object
some 650 million light years
from Earth.
This beautiful, almost lifelike
system is known simply as the Bird.
It's the spectacular result
of what we used to think
was two galaxies colliding.
It's events happening
in the head of the Bird
that are most interesting from a
perspective of life in the universe.
Because the head is formed
by another galaxy,
a third galaxy, an island
of billions and billions of stars,
colliding with two galaxies
that form the wings and the body
at a speed of around
250 miles a second.
The turbulence, the disturbance,
that that creates is causing
many new stars to be formed.
These stars begin their lives
by burning hydrogen,
to produce ever more helium.
But as they age, as the hydrogen
runs out, they turn to this helium.
The temperature at their core rises
increasing the chances
of three helium nuclei
fusing together
to form a new element - carbon.
That process has been going on
for almost the entire
history of the universe,
back 13 billion years,
and it's the formation of stars
that is the vital first step
in the formation of life,
because stars produce
the heavy elements in the universe
including carbon.
From the universe's earliest times,
carbon has been created
inside ageing stars.
And over time,
this carbon has built up,
drifting through the cosmos
as dust...
..until some of it was caught up
in the formation
of a planet called Earth.
And it's here that we can see this
ancient carbon
brought vividly to life.
Today, the universe is old enough
that countless stars
have lived and died.
So, there's been plenty of time
to synthesise
the primordial hydrogen and helium
into the heavy elements.
The question now is, how does that
carbon get into the web of life?
Well, today,
it enters via one ingredient
and I'm going to measure it
using this balloon.
The ingredient is carbon dioxide,
which plays a key role
in photosynthesis.
Each night the carbon dioxide
concentration increases,
filling the air around the leaves
at the top of the trees.
This balloon has a carbon dioxide
monitor in it
which is going to measure the change
in the levels of CO2
at the top of the forest canopy
as night turns to day.
As the sun rises,
the trees begin to photosynthesise.
At 6pm last night,
just after sunset,
the concentration
was around 350 parts per million.
Around 10pm, around four hours after
sunset,
the concentration had risen to
about 400 parts per million.
Now, at about midday,
the concentration's back down
to about 345 parts per million.
So that's a variation over a period
of about 18 hours of 10%
in the concentration
of carbon dioxide,
just in that piece of atmosphere
at the top of the forest canopy.
What you are seeing there
is photosynthesis in action.
Every day, across the planet,
photosynthesis uses sunlight
to turn carbon dioxide and water
into simple sugars.
The overwhelming majority
of the carbon
is locked up inside long chains
of sugar molecules
called cellulose and lignin.
Lignin is the stuff that gives
wood its strength.
So, in this form, remember,
that is most of it,
it is very difficult indeed
for animals to access.
For the energy and nutrients locked
away in these long carbon chains
to move through the food web,
they must be broken down.
The best place to see that process
in action is out on the open plain.
It's one vast larder for all
manner of organisms.
By far the most effective
harvester of carbon
is actually one of the smallest
creatures on the savanna.
Termites are social insects,
working together to form
a characteristic sight,
seen all over the bush.
That's a termite mound. Actually,
it's the tip of the iceberg.
The termite city extends
way beyond that underground.
And its function is fascinating.
It's essentially
an air-conditioning system.
What it does is maintain specific
conditions inside the mound -
the conditions of the rainforest.
When the termites first colonised
the savanna 30 million years ago,
they brought the rainforest
with them
to support a form of life that was
already wonderfully adapted
to living off dead wood.
This is what these termite mounds
are all about.
Can you see those structures, those
white honeycomb-like structures?
Those are called fungal combs.
They're wood pulp and possibly
bits of dead grass
that the termites bring in and build
into that structure.
And the reason the conditions have
to be the same as the rainforest
is because they grow a particular
genus of fungus called termitomyces
around those honeycombs.
The job of that fungus
is to break down the lignin
and cellulose inside the wood
and convert it into a form that the
termites can eat,
which you can see there,
the little white nodules,
just present
on the honeycomb structure.
The termites lack the enzymes to
break down the wood efficiently,
so they have become farmers,
tending to one giant social stomach.
There's a very intense relationship
between the termites and the fungus.
You don't find that fungus anywhere
else in the world
as far as we know,
other than inside termite mounds.
It's thought that up to 90%
of the carbon locked up in lignin
in this part of Africa is released
back into the food chain again,
solely by those termites
and that fungus.
So the termites deal with
most of the lignin,
but that still leaves a vast store
of carbon in the form of cellulose.
Across Africa, herds of mammals
graze on grasses and leaves,
turning the cellulose into meat.
Many are a type of mammal
known as a ruminant...
..the largest of which is one of the
easiest animals to spot on safari.
There's a giraffe there as well.
Giraffes live off a diet similar
to termites. They eat cellulose.
Primarily
the tops of the acacia trees
that you see scattering
the African savanna.
And they face that same problem,
they've got to break those
difficult carbon bonds down
and they've come up with a very
similar solution
which is to cultivate
bacteria and fungi.
But they do it inside their stomachs
and ruminants like giraffes
have had to build a very complex
system in order to do that.
They've got four stomachs,
one of them contains their culture
of bacteria and fungi,
and they allow them to digest
that difficult cellulose.
Even with all this hardware,
ruminants must feed
for over two thirds of the day.
But there are other creatures here
that have found a short cut,
after all,
if plant fibres are hard to digest,
why not let someone else do the work
and simply steal a meal?
It's coming for us.
Oh, my God...
ENGINE STARTS
Look what we've just found.
We were out looking for giraffe
this morning,
and we found about ten of them
over there,
but in looking for the giraffe,
we've just found a leopard.
This is one of the top predators
out here.
He's got very little to fear apart
from other leopards and maybe lions.
He's having a good look,
he certainly doesn't care about us.
He's around two years old
and at the moment,
he doesn't have his own territory,
he's too young for that.
So he's lying low.
He'll have to make about two kills
a week, to stay in good condition.
So, maybe he'll catch
an impala every three to four days,
and he's obviously doing that.
Because, look at him!
He's looking for protein.
He likes your boom. >
And I'm a little bit worried,
cos I'm protein!
Oh, wow.
He's after your boom, George. >
He's coming really close to us
because he's after
the sound man's boom pole.
Which is...oh!
That's incredible.
RUMBLING MICROPHONE DISTORTION
I just...
HE LAUGHS
He's taken it...
From its origin
in the death of stars...
..its capture by plants...
..through insects,
mammals and on.
The carbon cycle is
the real circle of life.
Out there tonight, the relentless
recycling of carbon
through the food chain
will continue.
As night falls, you can almost
sense it - the change in the sounds
and the atmosphere.
Some will die,
so that others can live,
as carbon leaps
from branch to branch
across the great tree of life.
And guiding it along its way is just
one very special form of chemistry.
Every living thing is just
a temporary home
for carbon atoms that existed long
before there was life on Earth
and will exist long
after Africa and Earth are gone.
But, the pattern of life,
the information needed
to build a zebra, or a tree,
or a human being or a lion persists.
It's passed on from generation
to generation, in a molecule.
A helical molecule with
a backbone of carbon called DNA.
MUSIC: "Atmosphere"
by Joy Division
There was a time
when Earth appeared empty.
♪ Walk
♪ In silence
♪ Don't walk away
♪ In silence... ♪
Yet despite appearances,
3.8 billion years ago
life was already under way,
in the form of tiny living specks
that probably all shared
the same biochemistry.
We know that every living
thing on the planet today -
so every piece of food you eat,
every animal you've seen,
everyone you've ever known
or will know,
in fact every living thing that WILL
ever exist on this planet -
was descended from that one speck.
♪ Walk
♪ In silence... ♪
We call it the last universal
common ancestor, or LUCA.
So, just as the universe
had its origin at the Big Bang,
all life on this planet
had its origin in that one moment.
Less than a billion years
after its formation,
there was already life on Earth.
It's possible that some of it used
biochemistry
utterly different from the life
we see today.
If so, it has long been extinct.
It's also possible that the first
life may not have been cellular -
just living chemistry in the porous
rocks of some ancient ocean.
We're not sure,
but what's certain is that one day,
a population of organisms showed up
with biochemistry that we WOULD
recognise.
This was LUCA.
The first expression
of a form of life that would in time
throw up a group of humans who left
their mark in this part of Africa.
Now, we don't know what
LUCA looked like,
we don't know precisely where it
lived or how it lived.
But we do know this.
If you start to trace my ancestral
line back to my parents,
to their parents, to their parents,
to their parents,
all the way back
through geological timescales
over hundreds of thousands
of millions and billions of years,
there will be an unbroken line
from me all the way back to LUCA.
We know that, because every living
thing on the planet today
shares the same biochemistry.
We all have DNA. It's made of the
same bases, A, C, T and G.
They code for the same amino acids.
Those amino acids build the same
proteins, which do very
similar jobs, whether you're a
plant, a bacterium, or a
bipedal hominid, like me.
So all life uses the same
fundamental biology...
..those four bases, A, C, T and G,
which code for just 20 amino acids,
which in turn build each
and every one of life's proteins.
Be you bacteria, plant,
bug or beast,
your design comes from your DNA.
So it's this molecule that must hold
the key to understanding why
life today is so diverse.
We now know that the answer
to the question,
"Why is life on Earth so varied?"
is actually the answer to
the question, "Why is the DNA
molecule itself so varied?"
What are the natural processes that
cause the structure of DNA to
change?
Well, part of the answer actually
doesn't lie on Earth at all.
It lies up there amongst the stars.
And I can show you what I mean,
using this,
which is a cloud chamber, a piece
of apparatus that has a unique place
in the history of physics.
I'm going to cool it down using dry
ice, frozen carbon dioxide,
just below -70 degrees Celsius.
I'll put the top on.
HIGH-PITCHED SQUEAKING
Hear that?
That's the metal at the bottom
of the tank cooling down very
rapidly to -70.
The cloud chamber works by having
a super-saturated
vapour of alcohol
inside the chamber.
Plenty on there...
Now, I want to get that alcohol,
I want to boil it off,
to get the vapour into the chamber.
So I'm going to put a hot water
bottle on top.
This is the first genuine particle
physics detector.
It's the piece of apparatus that
first saw antimatter.
And it really does consist
only of a fish tank, some alcohol,
a bit of paper,
and a hot water bottle.
There, look at that.
Do you see that?
Cloud vapour trail.
That's a cosmic ray.
That was initiated by a particle,
probably a proton,
that hit the Earth's atmosphere.
It almost certainly originated
outside our solar system
and was accelerated by the magnetic
fields of our galaxy.
It may even have
begun its life BEYOND our galaxy.
Now, imagine if one of those hits
the DNA of a living thing.
What that will do is cause
a mutation.
That mutation may be detrimental,
or,
very, very occasionally it might be
beneficial.
And I think it's quite wonderful
to imagine that maybe
one of the key mutations that was
selected for over the millennia
that led to some trait in ME
was caused by some particle
that began its life perhaps
in a massive supernova explosion,
perhaps outside our galaxy
and went
and hit the DNA of something
and caused some
kind of beneficial mutation.
We don't know,
but you can dream, can't you?
Mutations are an inevitable part of
living on a planet like Earth.
They're the first hint at how
DNA and the genes
that code for every living thing
change from generation to
generation.
Mutations are the spring
from which innovation in the living
world flows.
But cosmic rays are not the only way
in which DNA can be altered.
There's natural background
radiation from the rocks,
there's the action of chemicals
and free radicals.
There can be errors
when the code is copied.
And then all those changes can be
shuffled by sex, and indeed
whole pieces of the code can be
transferred from species to species.
So, bit by bit, in tiny steps
from generation to generation,
the code is constantly
randomly changing.
Now, whilst there's no doubt that
random mutation does alter DNA,
evolution is anything but random.
It can't be,
because the chances of something
with DNA as complex as this
appearing by luck alone
are vanishingly small.
Imagine you just changed one
position in the code at random,
a random mutation.
There are four letters,
A, T, C and G,
so there are four possible
combinations.
If there are two places in the code,
there are four combinations for each
one. So that makes 16.
If there are three,
then there are 64 possibilities.
By the time you get to a code
with 150 letters in it,
then there are more possible
combinations in the code
than there are atoms in the
observable universe.
Now, a hippo has a code
with around three billion
different letters.
So the number of combinations
of those letters, the chances of
producing that code at random, are
absolutely, infinitesimally small.
It's impossible.
So there must be a non-random
element to evolution...
..a natural process,
which greatly restricts this
universe of possibilities,
and shapes the outcome.
We call it natural selection.
And to see it in action,
let's return to where we began
on the island of Madagascar.
Around 65 million years ago,
a group of seafarers were nearing
the end of a long
journey across the Indian Ocean.
These were accidental travellers,
a group of creatures from Africa,
trapped on a natural raft
and carried by the ocean currents.
The land they found was
virgin green territory.
Plants, insects, reptiles and birds
had established themselves,
but there were
none of their own kind.
They were caught up in a saga that
tells of the great
shifting of Earth's
continental plates.
It's impossible to understand
the diversity of life on Earth today
without understanding the
shifting geography of our planet.
Here's a map of Earth's southern
hemisphere as it was
150 million years ago, and you see
it's dominated by a single landmass
called Gondwana.
And then, 90 million years ago,
Gondwana had begun to break up,
to separate,
into something that looks quite
recognisably like Africa,
and these two islands,
Madagascar and India.
Now, subsequently India has
drifted northwards
and bumped into Eurasia,
raising the Himalayas.
But, crucially,
Madagascar has remained isolated.
It's been an island surrounded by
ocean for almost 90 million years.
So, when those seafarers
arrived on their raft of trees
and twigs and leaves,
they had a blank canvas -
two, three,
maybe even a single pregnant
individual
had a whole island to roam across.
And over 65 million years, they have
blossomed into hundreds and
thousands of individuals, and become
Madagascar's most iconic animals.
Finding the descendants of those
ancient mariners is not easy.
But local guide Joseph has been
tracking them for years.
And he's going to help me find them.
There at the top of the tree
is an indri,
which is the largest
lemur in Madagascar.
He's just sat there watching us
quietly at the moment.
This lemur here is a very
special lemur.
He has a name, he's called David.
After Sir David Attenborough.
LEMUR SCREECHES
LEMUR SCREECHES
Now, we can only do this because
Joseph has spent
a lot of time with these lemurs.
So they trust him. And therefore,
it seems, they trust me.
Its enormous hands!
The reason, it's thought, that we
find lemurs here in Madagascar
and Madagascar alone
is because there are no simians,
there are no chimpanzees,
none of my ancestral family,
dating back tens of millions
of years, to out-compete them.
So what's thought to have happened
is that around 65 million years ago
one of the lemur's ancestors
managed to sail across the
Mozambique Channel, and landed here.
There were none of those
competitors here,
and so the lemurs have
flourished ever since.
There are now over 90 species
of lemur, or subspecies,
in Madagascar,
and no species of my lineage,
the simians.
LEMUR SCREECHES
Over a vast sweep of time,
the lemurs have diversified
to fill all manner of different
habitats.
From the arid, spiny
forests of the south...
..to the rocky canyons in the north,
there is something about this island
that is allowing the lemur's DNA
to change in the most amazing ways.
We're on the hunt for an aye-aye,
the most closely related of all
the surviving lemurs
to their common ancestor.
Oh, yes...
Oh, yeah.
Just shone the light up,
and we saw these absolutely...
Two bright red eyes, shining out.
She's very high up at the moment.
Don't want to lose
sight of her in this forest,
which is very dark and dense.
The team have located a female
aye-aye, and her son.
They want to attach radio collars
to track their movements,
and better understand how far
they range through these forests.
But first, they must sedate them
with a dart.
He's waiting for it to come down
low enough to get that clean shot -
I mean, how you get a clean shot in
this I have no idea.
After two hours of traipsing through
the treacherous forest,
the aye-ayes remain at large.
INDISTINCT CHATTER
Well, here is the aye-aye that was
tranquillised last night.
They finally got her about half
an hour after we left.
I think it was probably
because we were disturbing her.
Apparently as soon as we'd gone,
she came down the tree
and she was tranquillised.
And as you can see
she's pretty well sedated now,
which is fortunate for me
because she has certain adaptations
that I wouldn't like to be deployed.
You can see there her teeth.
Her teeth are very
unusual for a primate -
in fact, unique,
because they carry on growing,
so she's much
more like a rodent in that respect.
And that's so
she can gnaw into wood.
You see, aye-ayes have filled
a unique niche on Madagascar.
It's a niche that's filled by
woodpeckers in many other areas of
the world.
What she does is she feeds on grubs
and bugs inside trees,
and to do that, she has several
unique adaptations
of which her teeth are one.
The most startling is this
central finger here. It's bizarre.
It's got a ball
and socket joint, for a start,
so it has complete 360-degree
movement.
It feels to me almost
as if it's broken, but it isn't,
it's just, you can move it around
in any direction.
And she uses that finger initially
to tap on the trunk of the tree,
and then, listening to the echo from
that tapping, with these huge ears
she can detect where the grubs are.
And then, she gnaws through the wood
with those rodent-like teeth,
and then uses this finger again to
reach inside the hole
and get the bugs out.
So the question is, why?
How could an animal be so precisely
adapted to a particular lifestyle?
She's waking up now!
And the answer is natural
selection.
See, what must have happened is
way back,
when the ancestors of the
lemurs - the Lemuriformes -
arrived in Madagascar,
there must have been a mutation that
lengthened the middle finger ever
so slightly of one of those lemurs.
And that must have given it
an advantage.
That must have allowed it perhaps
to reach into little holes
and search for grubs.
There's some reason why that
lengthened middle finger
meant that that gene was more likely
to be passed to the next generation
and then down to
the next generation.
So that landscape of possibilities
is narrowed,
it's narrowed
because that gene persists.
And it's persisted now
for at least 40 million years,
because this species has been on
one branch of the tree of life now
for over 40 million years.
And so, over those years
that middle finger
has got more and more specialised.
Natural selection has allowed the
aye-aye's wonderfully mutated finger
to spread through the population.
And this same law applies
to all life.
If you have a mutation that helps
you in the struggle to survive,
you are more likely to leave
more offspring.
And in the next generation, that
mutation is more likely to survive.
So this animal is a beautiful
example, probably one
of the best in the world, of how the
sieve of natural selection produces
animals that are perfectly adapted
to live in their environment.
Now, there are many reasons to study
the aye-aye. But here's a good one.
In the 1970s, it was thought
the aye-aye was extinct.
Now, we know there are several
thousand in the forests
of Madagascar -
5,000, 6,000, 7,000,
certainly less than 10,000 -
but over the last 50 years,
50% of this forest has vanished.
This is an animal that's been around
as a species for over
40 million years.
So it's important to know
how these animals are doing,
and how they're surviving in this
diminishing habitat.
Whilst natural selection explains
why the aye-aye evolved,
it alone can't explain how a small
group of individuals, over 60
million years ago,
gave rise to over 90 different
species of lemur today.
But there is another form of life
that can offer us a clue.
Up here in the high forest canopy,
we're in a very different
environment to the one down there
on the forest floor.
It's a more arid environment,
it's almost like a desert.
It's exposed to the sun,
water is harder to come by.
And so, this is
a sea of different niches,
that are able to be occupied
and exploited by animals
that are different to the ones
you'll find down there on the floor.
So, in a very real sense, this is an
island, an island to be colonised.
And sure enough, there are settlers
to be found, even here.
You see that thing that looks like
a muddy ball there, on the branch?
Well, that's an ants' nest,
it's home to a species of
Crematogaster ants
that are unique not only to
Madagascar,
but to the forest canopy.
You see, what makes those ants
unique is that they can
build their own nests.
There are very few species of ants
that can do that.
So that is an island, that is
a niche,
and it's allowed that
species of ant to develop
because they're isolated
from the rest of the ecosystem.
And astonishingly,
within this niche,
another form of life new to science
has been discovered...
..a beetle that manages to
survive here unharmed by the ants.
How it does it is a mystery.
But what IS known is that this
particular species has only
ever been found inside these nests.
So, that really is its own
mini-ecosystem,
with species living in it
that are unique to that island.
We live on an ever-shifting,
dynamic world
that creates islands in abundance.
Earth's mountain ranges,
river valleys and canyons
all create islands for life.
And it's these islands
that those ancestors of the lemurs
found when they arrived
in Madagascar.
Empty niches, where populations
became isolated,
and over great swathes of time
involved into such wonderfully
diverse forms.
150 years on from the Origin
Of Species, the subtlety
and beauty of Darwin's insight is
still revealing itself to us.
It describes how our beautiful,
complex tree of life
has grown from a once desolate
universe.
The chemistry of carbon
allows for the existence of
a molecule that is able to replicate
itself, and pass information on
from generation to generation.
There can be random changes
in the structure of that molecule -
mutations - and they are tested
by their interaction with
the environment
and with living things.
The ones that pass that test
survive,
and the ones that fail that test
are lost.
The separation and isolation
of living things onto islands -
which may be physical,
like Madagascar,
or just the single branch of
a single tree -
results in speciation,
the explosion of living forms
highly specialised to occupy niches
within niches.
And this is the explanation
for the diversity of life on Earth.
"There is grandeur in this
view of life," as Darwin wrote,
and understanding how it happened
surely only adds to the wonder.
As precise as Einstein's theories
of relativity, and as profound
as thermodynamics,
Darwin has given us another
universal law.
Evolution by natural selection.
And if evolution is
the law on this island,
then it will apply
throughout the cosmos.
Which begs a big question.
Could there be other "trees of life
most beautiful" amongst the stars?
In 2011,
we discovered a rocky planet
orbiting around a distant star,
with daytime temperatures not too
dissimilar to those found on Earth.
Now, there must be millions
if not billions of such planets
out there in the universe,
and it's inconceivable to me
that none of them
will have trees of life as complex
or even more complex than our own.
But that doesn't devalue
the existence of OUR tree,
because our tree is unique.
It consists of thousands
of branches,
all interdependent
on thousands of others,
and the precise structure depends
on chance events, like the passage
of the lemurs across the ocean
65 million years ago.
So when you go outside tomorrow,
just take a look at a little
piece of your world.
A corner of your garden, or a park,
or even the grass that's
growing in a crack in the pavement.
Because there will be life there,
and it will be unique.
There will be nowhere like that
anywhere else in the universe.
And that makes our tree, from the
sturdiest branch to the most
fragile twig,
indescribably valuable.
MUSIC: "Underneath the Stars"
by Kate Rusby
♪ Underneath the stars you met me
♪ And underneath the stars
you left me
♪ I wonder if the stars regret me
♪ I'm sure they'd like me
if they only met me
♪ They come and go
of their own free will
♪ Go gently... ♪
Subtitles by Red Bee Media Ltd