All language subtitles for C09FA79085E3308ACBCF1198582F8966_eng

This creature is a wonder of life.

A voracious predator,

this male has lived underwater
for nearly five months,

feeding, growing,
preparing for this moment.

He's about to undertake

one of the most remarkable
transformations

in the natural world.

From aquatic predator...
to master of the air.

The brief adult life of a dragonfly

is amongst the most
energetic in nature.

Dragonflies are
the most remarkable animals.

You can see their
incredible agility in flight

just watching them skim across
the surface of this pond.

They can pull two and a half G
in a turn,

and they can fly at 15 mph,

which is fast
for something that big.

They've been around on Earth since
before the time of the dinosaurs,

and in that time they've been
fine-tuned by natural selection

to do what they do - which is
to catch their prey on the wing.

So, dragonflies are beautiful
pieces of engineering.

They're intricate, complex machines.

But is that all they are?

Because once their brief lives are
over, their vitality will be gone.

And this raises deep questions.

What is it that makes
something alive?

And how did life begin
in the first place?

So, what is the difference
between the living and the dead?

What is life?

I've come to one of the most
isolated regions of the Philippines

to visit the remote
hilltop town of Sagada.

It's a two-day drive
from the capital, Manila,

over some of the country's
roughest roads

that wind their way 1,500
metres up into the hills.

This is a place

where the traditional belief is
that mountain spirits give us life

and that our souls return
to the mountain when we die...

..and where the people who live here
still imagine that

the spirits of the dead
walk among the living.

Tonight is November 1st,
and here in Sagada -

in fact across the Philippines -
that means it's the Day of the Dead.

That's the day when people come to
this graveyard on a hillside

and, well, celebrate
the lives of their relatives.

The people light fires to honour
and warm the departed,

inviting their souls
to commune with them.

Now, not matter how
unscientific it sounds,

this idea that there's some kind of
soul or spirit or animating force

that makes us what we are and that
persists after our death is common.

Virtually every culture,
every religion,

has that deeply-held belief.

And there's a reason for that -
because it feels right.

I mean, just think about it. It's
hard to accept that when you die

you will just stop existing
and that you are, your life,

the essence of you,
is just really something

that emerges from an inanimate
bag of stuff.

Don't get too close.

You can see that these people feel

not only do they come to celebrate
the lives of their relatives,

but they're coming in some sense
to communicate with them.

Their relatives, even though
their physical bodies have died,

are still in some sense here.

When you think about it,
that's not so easy to dismiss.

If we are to state that science
can explain everything about us,

then it's incumbent on science
to answer the question,

what is it that animates
living things?

What is the difference
between a piece of rock

that's carved into a gravestone
and me?

For millennia, some form of
spirituality has been evoked

to explain what it means
to be alive, and how life began.

It's only recently

that science has begun to answer
these deepest of questions.

In February 1943,

the physicist Erwin Schrodinger
gave a series of lectures in Dublin.

Now, Schrodinger is almost
certainly most famous

for being one of the founders
of quantum theory.

But in these lectures, which
he wrote up in this little book,

he asked a very different
question - What Is Life?

And right up front, on page one,
he says precisely what it isn't.

It isn't something mystical,
says Schrodinger.

There isn't some magical spark
that animates life.

Life is a process.

It's the interaction between
matter and energy

described by the laws
of physics and chemistry.

The same laws that describe

the falling of the rain
or the shining of the stars.

So, the question is,

how is that this magnificent
complexity that we call life

could have assembled itself
on the surface of a planet

which itself formed

from nothing more than a
collapsing cloud of gas and dust?

To Schrodinger, the answer had to
lie in the way living things process

one of the universe's most elusive
properties - energy.

Energy is a concept
that's central to physics,

but because it's a word
we use every day

its meaning has got a bit woolly.

I mean, it's easy to say
what it is in a sense.

Obviously this river has got energy
because over decades and centuries

it's cut this valley
through solid rock.

But while this description
sounds simple,

in reality things are
a little more complicated.

For me, the best definition is that

it's the length of the space time
four vector and time direction,

but that's not very enlightening,
I'll grant you that.

Over the years,

the nature of energy has proved
notoriously difficult to pin down.

Not least because it has
the seemingly magical property

that it never runs out.

It only ever changes
from one form to another.

Take the water in that waterfall.

At the top of the waterfall,

it's got something called
gravitational potential energy,

which is the energy it possesses

due to its height
above the Earth's surface.

See, if I scoop some water
out of the river into this beaker,

then I'd have to do work to carry
it up to the top of the waterfall.

I'd have to expend energy
to get it up there.

So it would have that
energy as gravitational potential.

I can even do the sums for you.

Half a litre of water
has a mass of half a kilogram,

multiply by the height,
that's about five metres,

the acceleration due to gravity's
about ten metres per second squared.

So that's half times five times ten
is 25 joules.

So I'd have to put in 25 joules

to carry this water
to the top of the waterfall.

Then if I emptied it over
the top of the waterfall,

then all that gravitational
potential energy

would be transformed
into other types of energy.

Its sound, which is
pressure waves in the air.

There's the energy of the waves
in the river. And there's heat.

So it'll be a bit hotter down there

because the water's
cascading into the pool

at the foot of the waterfall.

Buy the key thing is
energy is conserved,

it's not created or destroyed.

So, because energy is conserved,

if I were to add up
all the energy in the water waves,

all the energy in the sound waves,

all the heat energy
at the bottom of the pool,

then I would find
that it would be precisely equal

to the gravitational potential
energy at the top of the falls.

What's true for the waterfall is
true for everything in the universe.

It's a fundamental law of nature,

known as the first law
of thermodynamics.

And the fact that energy
is neither created nor destroyed

has a profound implication.

It means energy is eternal.

The energy that's here now
has always been here,

and the story of the
evolution of the universe

is just the story of the
transformation of that energy

from one form to another,

from the origin
of the first galaxies

to the ignition of the first stars

and the formation
of the first planets.

Every single joule of energy
in the universe today

was present at the Big Bang,
13.7 billion years ago.

Potential energy held in
primordial clouds of gas and dust

was transformed into kinetic energy

as they collapsed to form stars
and planetary systems,

just like our own solar system.

In the Sun,

heat from the collapse initiated
fusion reactions at its core.

Hydrogen became helium.

Nuclear-binding energy was released,
heating the surface of the Sun,

producing the light that
began to bathe the young Earth.

And at some point in that story,
around four billion years ago,

that transformation of energy
led to the origin of life on Earth.

Around 350 kilometres
south of Sagada, this is Lake Taal.

Despite its sleepy,
languid appearance,

this landscape has been
violently transformed by energy.

When I think of a volcano,

I usually think of
a pointy, fiery mountain

with a little crater in the top.

Probably a bit like that one.

But actually this entire lake is the
flooded crater of a giant volcano.

It began erupting
only about 140,000 years ago,

and in that time it's blown 120
billion cubic metres of ash and rock

into the Earth's atmosphere.

This crater is 30 kilometres across
and in places 150 metres deep.

That's a cube of rock

five kilometres by five kilometres
by five kilometres

just blown away.

It's a big volcano.

Taal Lake is testament
to the immense power

locked within the Earth
at the time of its formation.

Since the lake was created,

a series of further eruptions
formed the island in the centre.

And at its heart

is a place where you can glimpse
the turmoil of the inner Earth,

where energy from the core
still bubbles up to the surface...

..producing conditions similar
to those that may have provided

the very first spark of life.

The water in this lake
is different from drinking water

in a very interesting way.

See, if I test this
bottle of water with this,

which is called
universal indicator paper,

then you see immediately
that it goes green.

And that means
that it's completely neutral.

It's called PH7 in the jargon.

But then look what happens
when I test the water from the lake.

Now the indicator paper
stays orange.

In fact, it might have gone
a bit more orange.

So that means that this is acid.
It's about PH3.

At the most basic level,

the energy trapped inside the Earth
is melting rocks.

And when you melt rock like this
you produce gases.

A lot of carbon dioxide,

and in this case of this volcano,
a lot of sulphur dioxide.

Now, sulphur dioxide
dissolves in water

and you get H2SO4,
sulphuric acid.

Now, what I mean
when I say that water is acidic?

Well, water is H2O - hydrogen
and oxygen bonded together.

But actually when it's liquid it's
a bit more complicated than that.

It's actually a sea of ions.

So H-plus ions,
that's just single protons.

And OH-minus ions, that's
oxygen and hydrogen bonded together,

all floating around.

Now, when something's neutral,
when the PH is seven,

that means that the concentrations
of those ions

are perfectly balanced.

When you make water acidic,

then you change the concentration
of those ions and, to be specific,

you increase the concentration
of the H-plus ions of the protons.

So, this process of acidification
has stored the energy of the volcano

as chemical potential energy.

The volcano transforms heat from the
inner Earth into chemical energy

and stores it as a reservoir
of protons in the lake.

And this is the same way
energy is stored

in a simple battery
or fuel cell.

These bottles contain a weak acid

and are connected by
a semi-permeable membrane.

Passing an electric current
through them has a similar effect

to the volcano's energy
bubbling up into the lake.

It causes protons to build up
in one of the bottles.

You can think of it, I suppose,
like a waterfall,

where the protons are up here
waiting to flow down.

All you have to do
to release that energy

and do something useful with it
is complete the circuit.

Which I can do by
just connecting a motor to it.

There you go. Look at that.

That's the protons
cascading down the waterfall

and driving the motor around.

It actually works!

Quite remarkable, actually.

Now, the fuel cell
produces and exploits

its proton gradient artificially.
But there are places on Earth

where that gradient occurs
completely naturally.

Here, for example.

So we've got the
proton reservoir over there,

the acidic volcanic lake.

If you look that way,
there's another lake,

and the reaction of the water
with the rocks on the shore

make that lake slightly alkaline,

which is to say that there's
a deficit of protons down there.

So here's the waterfall,

a reservoir of protons up there,
a deficit down there.

If you could just connect them,

then you'd have a naturally
occurring geological fuel cell.

And it's thought that
the first life on our planet

may have exploited
the energy released

in those natural proton waterfalls.

What do you think?
It's good, isn't it?

These are pictures
from deep below the surface

of the Atlantic Ocean, somewhere
between Bermuda and the Canaries.

And it's a place
known as the Lost City.

You can see why.

Look at these huge towers of rock,
some of them 50-60 metres high,

reaching up from the floor
of the Atlantic and into the ocean.

It's what's known as
a hydrothermal vent system.

So these things are formed by
hot water and minerals and gases

rising up from
deep within the Earth.

But the reason it's thought that
life on Earth may have begun

in such structures is because

these are a very unique
kind of hydrothermal vent

called an alkaline vent.

And, about four billion years ago,
when life on Earth began,

seawater would have been
mildly acidic.

So, here is that proton gradient,
that source of energy for life.

You've got a reservoir of protons
in the acidic seawater

and a deficit of protons
around the vents.

And the vents don't just provide
an energy source.

They're also rich in
the raw materials life needs.

Hydrogen gas, carbon dioxide

and minerals containing iron,
nickel and sulphur.

But there's more than that.

See, these vents are porous - there
are little chambers inside them -

and they can act to concentrate
organic molecules.

You've got everything
inside these vents.

You've got concentrated
building blocks of life

trapped inside the rock.

And you've got that proton gradient,

you've got that waterfall
that provides the energy for life.

So this could be where
your distant ancestors come from.

And places like these could be the
places where life on Earth began.

The first living things
might have started out

as part of the rock
that created them.

Simple organisms
that exploited energy

from the naturally-occurring
proton gradients in the vents.

And we think this because

living things still get their energy
using proton gradients today.

Deep within ourselves,

the chemistry the first life
exploited in the vents

is wrapped up in structures
called mitochondria -

microscopic batteries
that power the processes of life.

This is a picture
of the mitochondria

from the little brown bat.

This is a picture
of the mitochondria from a plant.

It's actually a member
of the mustard family.

This is a picture
of the mitochondria in bread mould.

And this of mitochondria
inside a malaria parasite.

So, the fascinating thing is that
all these animals and plants,

and in fact virtually every
living thing on the planet,

uses proton gradients
to produce energy to live. Why?

Well, the answer is probably

because all these radically
different forms of life

share a common ancestor.

And that common ancestor
was something that lived in

those ancient undersea vents,
four billion years ago,

where naturally-occurring
proton gradients

provided the energy
for the first life.

So, if you're looking for
a universal spark of life,

then this is it.

The spark of life
is proton gradients.

In those four billion years,
that spark has grown into a flame.

And a few simple organisms
clustered around a hydrothermal vent

have evolved to produce
all the magnificent diversity

that covers the Earth today.

Today, life on Earth
is so diverse,

it covers so much of the planet that
you can find places like this lake,

where it's effectively
its own sealed ecosystem.

It's saltwater,
it's connected to the sea,

but it's only connected through
small channels through the rock.

So that means that the marine life
in here is effectively isolated.

This is the Golden Jellyfish,

a unique sub-species only found
in this one lake on this one island,

in the tiny Micronesian
Republic of Palau.

They used to live
like most jellyfish,

cruising the open ocean, catching
tiny creatures, zooplankton,

in their long tentacles.

But today their tentacles
have all but disappeared

because the Golden Jellyfish

have evolved to do something that
very few other animals can do.

It really is incredible.

There are,
I want to say millions of jellyfish,

as far as you can see,

all the way down till the light
vanishes there are jellyfish.

And you can see they've
congregated in the sun.

If you go over there to where
the lake's in shade,

there are just none.

They're in this pool of light,
beneath the sun.

There are millions of them.

Beautifully elegant things
just floating around.

I'm not being unduly hyperbolic,
it's quite remarkable.

MAKES MUFFLED NOISE

This lake is home to
over 20 million jellyfish.

Whose success comes down
to a remarkable adaptation.

Their bodies play host to
thousands of other organisms -

photosynthetic algae that harvest
energy directly from sunlight.

The jellyfish engulf
the algae as juveniles,

and by adulthood algal cells make
up around 10% of their biomass.

Grouped into clusters
of up to 200 individuals,

they live inside the jellyfish's
own cells.

The Golden Jellyfish uses algae

to get most of its energy
from photosynthesis.

They go to the surface and
gently... Wow, there's one there.

They're gently turning.

The reason they do that
is to give all their algae

an equal dose of sunlight.

So they're quite
democratic creatures,

just making sure
they get as much food as they can.

They just come up you, jellying
around, photosynthesising.

They tell me they don't sting.

But I'm sure I've got
a tingling from it.

And it's not just their anatomy

that's adapted to harvest
solar energy.

Every morning as the sun rises,

the jellyfish begin to swim
towards the east.

As the sun tracks across the sky,
they move back again
towards the west,

where they spend their night.

So the jellyfish have
this beautiful, intimate

and complex relationship with
the position of the sun in the sky.

As sunlight is captured
by their algae,

it's converted into chemical energy.

Energy they use to combine
simple molecules,

water and carbon dioxide, to
produce are far more complex one.

Glucose.

Once absorbed by the jellyfish,
glucose and other molecules

not only power their daily voyage
across the lake,

they provide the basic
building blocks the jellyfish

use to grow the elegant and complex
structures of their bodies.

So the jellyfish, through
their symbiotic algae,

absorb the light, the energy from
the sun, and they use it to live,

to power their processes of life.

And that's true,
directly or indirectly,

for every form of life
on the surface of our planet.

But things are a little bit more
interesting than that,

because energy is neither
created nor destroyed.

So life doesn't eat it somehow,
it doesn't use it up,

it doesn't remove
it from the universe.

So what does it do?

To understand how energy
sustains life,

you have to understand exactly what
happens to it as the cosmos evolves.

POWERFUL EXPLOSION BOOMS

In the first instance
after the Big Bang

there was nothing in the universe
but energy.

As it changed from one form
to another, galaxies, stars

and planets were born.

But while the total amount of energy
in the universe stays constant,

with every single transformation
something does change.

The energy itself becomes
less and less useful.

It becomes ever more disordered.

And you can see this process
in action as energy from the sun

hits the surface of the Earth.

So think about think about this
sand on the beach,

it's been under
the glare of the sun all day,

it's been absorbing its light
which has been heating it up,

and now that the sun is dipping
below the horizon,

then the sand
is still hot to the touch

because it's re-radiating all the
energy that it absorbed as heat

back into the universe.

The key word there is "all".
All the energy.

If it didn't do that then
it'd just gradually heat up

day after day after day,

and eventually, I suppose,
the whole beach would melt.

So what's changed?

Well, it's the quality
of the energy, if you like.

Think about it.

If as much energy is coming
back off this sand now
as it absorbed from the sun,

then it should
be giving me a suntan.

I should need sun cream if I sit
looking at this beach all night.

And obviously I don't.

The difference is that this
energy is of a lower quality.

It can do less.

It's heat, which is a very low
quality of energy indeed.

So what the sand's done
is take highly ordered,

high quality energy from the sun

and convert it to an equal amount
of low quality disordered energy.

This descent into disorder

is happening across
the entire universe.

As time passes, every single joule
of energy is converted into heat.

The universe gradually cools
towards absolute zero.

Until with no ordered energy left,
the cosmos grinds to a halt

and every structure in it
decays away.

Yet whilst the universe is dying,
everywhere you look life goes on.

It's a deep paradox that
Schroedinger was well aware of

when he wrote his book in 1943.

"How can it be,"
writes Schroedinger,

"That the living organism
avoids decay?"

In other words, how can it be that
life seems to continue to build

increasingly complex structures

when the rest of the universe is
falling to bits, is decaying away?

Now, that's a paradox, because the
universe is falling to bits,

it is tending towards disorder.

That is enshrined in
a law of physics called

the Second Law Of Thermodynamics.

And I think most physicists
believe that it's the one

law of physics
that will never be broken.

The key to understanding how life
obeys the laws of thermodynamics

is to look at both
the energy it takes in

and the energy it gives out.

This is a thermal camera,
so hot things show up as red,

and cold things show up as blue.

COCKEREL CROWS

So what you're seeing here
is that the chicken is hotter

than its surroundings.

Now, heat is a highly disordered
form of energy,

so the chicken is radiating disorder
out into the wider universe.

By converting chemical
energy into heat,

life transforms energy from an
ordered to a disordered form,

in exactly the same way as every
other process in the universe.

COCKEREL CROWS

In fact, every single human being

can generate 6,000 times more heat
per kilogram than the sun.

And it's by converting so much
energy from one form to another

that life is able to hang on to
a tiny amount of order for itself.

Just enough to resist the inevitable
decay of the universe.

COCKEREL CROWS

So it's no accident
that living things are hot

and export heat
to their surroundings.

Because it's an essential
part of being alive.

Living things borrow
order from the wider universe,

and then they export it
again as disorder.

But it's not precisely in balance.

They have to export more disorder

than the amount of order
they import.

That is the content
of the Second Law Of Thermodynamics.

And living things have
to obey the Second Law

because they're physical structures,
they obey the laws of physics.

Just by being alive, we too are part
of the process of energy

transformation that drives
the evolution of the universe.

We take sunlight that has its
origins at the very start of time,

and transform it into heat
that will last for eternity.

So, far from being a paradox,

living things can be
explained by the laws of physics.

The very same laws that describe
the falling of the rain

and the shining of the stars.

The dragonfly draws its energy
from proton gradients,

the fundamental chemistry
that powers life.

But the real miracles
are the structures

they build with that energy.

Borrowing order to generate cells.

Arranging those cells into tissues.

And those tissues into the intricate
architecture of their bodies.

So we've developed a quite
detailed understanding

of the underlying machinery
that powers these dragonflies,

and indeed all life on Earth.

And whilst we don't have all the
answers, it is certainly safe to say

that there's no mysticism required.

You don't need
some kind of magical flame

to animate these little machines.

They operate according
to the laws of physics,

and I think they're no less
magical for that.

Yet the dragonfly will only maintain
this delicate balancing act
for so long.

Because all living things
share the same fate.

Each individual will die.

But life itself endures.

DRAGONFLIES BUZZ

This is because there's something
that separates life

from every other process
in the universe.

BOAT ENGINE CHUGS

WILD ANIMAL ROARS

MONKEYS CHATTER

This is the
Malaysian state of Sabah,

on the northern tip
of the island of Borneo.

It's one of the most bio-diverse
places on the planet.

INSECT BUZZES

Home to 15,000 plant species...

..3,000 species of tree...

..420 species of bird...

..and 222 species of mammals.

Including those.
ELEPHANTS ROAR LOUDLY

Borneo's rainforests contain
trees that are thought to live

for more than 1,000 years.

But the forest itself has existed
for tens of millions of years.

The reason it persists is because
each generation of animal and plant

passes the information to recreate
itself on to the next generation.

And that's possible

because of a molecule found
in every cell of every living thing.

A molecule called DNA.

Now, all I need to isolate my DNA
is some washing up liquid,

a bit of salt, and the chemist's
best friend, vodka.

Now, to get a sample of DNA
I can just use myself.

If I just swill my tongue
around on the edge of my cheek,

I'll dislodge some cheek cells
into my saliva.

DOG BARKS OUTSIDE

LAUGHS

I missed the test tube.

There we are.
A physicist doing an experiment.

STIFLES LAUGHTER

Then I add a bit
of washing up liquid.

Now, what this will do is it will
break open those cheek cells

and it will also degrade
the membrane that surrounds

the cell nucleus
that contains the DNA.

Salt will encourage
the molecules to clump together.

DNA is insoluble in alcohol.

So you should get a layer of alcohol

with DNA molecules precipitated out.

Yeah. There, can you see?

Those strands of white.

And so in that cloudy,
almost innocuous looking solid

are all the instructions needed
to build a human being.

So that is what makes life unique.

Only living things have
the ability to encode

and transmit information
in this way.

And the consequences of that
profoundly affect

our understanding
of what it is to be alive.

This rainforest is
part of the Sepilok Forest Reserve,

and in here somewhere are some
of our closest genetic relatives.

Shh-shh.

There, there, can you see?

Orang-utans are highly specialised
for a life lived
in the forest canopy.

Their arms are twice as long
as their legs.

And all four limbs
are incredibly flexible.

Each one ending in a hand
whose curved bones

are perfectly adapted
for gripping branches.

These adaptations are encoded
in information

passed down in their DNA.

LAUGHS GENTLY

He's got a hat on.

He has actually just put a hat on.

This is the orang-utan's
genetic code.

It was published in 2011,

and there are over three billion
letters in it.

If flip through it...

..look at that.

Now, it's composed of only
four letters, A, C, T and G,

which are known as bases.

They're chemical compounds.
They're molecules.

And the way it works
is beautifully simple.

They're grouped into threes,
called codons,

and some of them just tell
the code reader, if you like,

how to start, or where
to start and when...

and when it's going to stop.

LAUGHS

He's fast.

So you'd have a start and a stop.

In between, each group of three
codes for a particular amino acid.

Now, amino acids are the
building blocks of proteins,

which are the building blocks
of all living things.

So you would just read along,

you'd find, start, stop, and then

you'd go along in threes,
build amino acid, build amino acid,

build amino acid, build amino acid,

stitch those together
into a protein,

and if you keep doing that,

eventually you'll come out
with one of those.

It's not that simple of course.
But the basics are there.

This code, written in there,
are the instructions to make him.

To faithfully reproduce
those instructions

for generation after generation,

the orang-utans and,
and indeed all life on Earth,

rely on a remarkable property
of DNA.

Its incredible stability
and resistance to change.

Every time a cell divides,
its DNA must be copied.

And the genetic code is highly
resistant to copying errors.

The little enzymes, the chemical
machines that do the copying,

on average make only one
mistake in a billion letters.

I mean, that's like copying out
the Bible about 280 times

and making just one mistake.

That fidelity means adaptations
are faithfully transmitted

from parent to offspring.

And so while we think of evolution
as a process of constant change,

in fact the vast majority
of the code is preserved.

So even though we're separated
from the orang-utans

by nearly 14 million years
of evolution,

what's really striking
is just how similar we are.

And those similarities are far
more than skin deep.

Orang-utans are surely
one of the most human of animals.

And they share many behavioural
traits that you would

define as being uniquely human.

They nurture their young for
eight years before they let them

go on their own into the forest.

In that time the infants learn
which fruits are safe to eat

and which are poisonous.

Which branches will
hold their weight and which won't.

And they can do all that
because they have a memory,

they can remember things
that happened to them in their life,

they can learn from them,

and they can pass them on
from generation to generation.

And that deep connection extends
far beyond our closest relatives.

Because our DNA
contains the fingerprint

of almost four billion years
of evolution.

BIRDS SING

If I draw a tree of life
for the primates,

then we share a common ancestor
with the chimps, Bonobos.

About four to six million years ago.

And if you compare our
genetic sequences you find

that our genes are 99% the same.

You go back to the split
with gorillas,

about six to eight million
years ago and again,

if you compare our genes you
find that they are 98.4% the same.

Back in time again, common ancestor
with our friends over there,

the orang-utans,
then our genes are 97.4% the same.

And you could carry on
all the way back in time.

You could look for our common
ancestor with a chicken,

and you'd find that our codes
are about 60% the same.

And in fact, if you look
for any animal, like him,

a little fly, or a bacteria,
something that seems superficially

completely unrelated to us,
then you'll still find sequences

in the genetic code which are
identical to sequences in my cells.

So this tells us
that all life on Earth is related,

it's all connected
through our genetic code.

DNA is the blueprint for life.

But its extraordinary fidelity
means it also contains a story.

And what a story it is.

The entire history of evolution
from the present day

all the way back to
the very first spark of life.

And it tells us that we're
connected, not only to every plant

and animal alive today, but to every
single thing that has ever lived.

The question, what is life,

is surely one of the grandest
of questions.

And we've learnt that life
isn't really a thing at all.

It's a collection of chemical
processes that can harness

a flow of energy to create
local islands of order,

like me and this forest,

by borrowing order
from the wider universe

and then transmitting it
from generation to generation

through the elegant
chemistry of DNA.

And the origins of that chemistry

can be traced back
four billion years,

most likely to vents
in the primordial ocean.

And, most wonderfully of all,
the echoes of that history,

stretching back for a third
of the age of the universe,

can be seen in every cell
of every living thing on Earth.

And that leads to what I think is
the most exciting idea of all,

because far from being some chance
event ignited by a mystical spark,

the emergence of life
on Earth might have been

an inevitable consequence
of the laws of physics.

And if that's true,

then a living cosmos might be
the only way our cosmos can be.