BBC.Wonders.of.Life.1of5.What.Is.Life
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00:00This creature is a wonder of life.
00:23A voracious predator, this male has lived underwater for nearly five months, feeding,
00:30growing, preparing for this moment.
00:38He's about to undertake one of the most remarkable transformations in the natural world.
00:46From aquatic predator to master of the air.
01:15The brief adult life of a dragonfly is amongst the most energetic in nature.
01:29Dragonflies are the most remarkable animals.
01:33You can see their incredible agility in flight, just watching them skim across the surface
01:39of this pond.
01:41They can pull two and a half G in a turn, and they can fly at 15 miles an hour, which
01:46is fast for something that big.
01:52They've been around on earth since before the time of the dinosaurs, and in that time
01:57they've been fine-tuned by natural selection to do what they do, which is to catch their
02:03prey on the wing.
02:19So dragonflies are beautiful pieces of engineering.
02:24They're intricate, complex machines, but is that all they are?
02:32Because once their brief lives are over, their vitality will be gone.
02:42And this raises deep questions.
02:49What is it that makes something alive?
02:56And how did life begin in the first place?
03:02So what is the difference between the living and the dead?
03:06What is life?
03:31I've come to one of the most isolated regions of the Philippines to visit the remote hilltop
03:47town of Cigarda.
03:51It's a two-day drive from the capital Manila over some of the country's roughest roads
03:56that wind their way 1,500 meters up into the hills.
04:18This is a place where the traditional belief is that mountain spirits give us life, and
04:24that our souls return to the mountain when we die, and where the people who live here
04:33still imagine that the spirits of the dead walk among the living.
04:51Tonight is November the 1st, and here in Cigarda, in fact, across the Philippines,
04:56that means that it's the Day of the Dead.
04:59That's the day when people come to this graveyard on a hillside and, well, celebrate the lives
05:05of their relatives.
05:17The people light fires to honour and warm the departed, inviting their souls to commune
05:23with them.
05:43No matter how unscientific it sounds, this idea that there's some kind of soul or spirit
05:49or animating force that makes us what we are and that persists after our death is common.
05:57Virtually every culture, every religion has that deeply held belief.
06:03And there's a reason for that, because it feels right.
06:06I mean, just think about it.
06:08It's hard to accept that when you die, you will just stop existing, and that you are
06:14your life.
06:16The essence of you is just really something that emerges from an inanimate bag of stuff.
06:38You can see that these people feel not only that they're coming to celebrate the lives
07:06of their relatives, but they're coming in some sense to communicate with them.
07:10Their relatives, even though their physical bodies have died, are still in some sense
07:14here.
07:15And when you think about it, that's not so easy to dismiss.
07:20I mean, if we are to state that science can explain everything about us, then it's incumbent
07:27on science to answer the question, what is it that animates living things?
07:33What is the difference between a piece of rock that's carved into a gravestone and me?
07:50For millennia, some form of spirituality has been evoked to explain what it means to be
07:56alive and how life began.
08:05It's only recently that science has begun to answer these deepest of questions.
08:32In February 1943, the physicist Erwin Schrödinger gave a series of lectures in Dublin.
08:38Now, Schrödinger is almost certainly most famous for being one of the founders of quantum
08:43theory.
08:44But in these lectures, which he wrote up in this little book, he asked a very different
08:48question, what is life?
08:51And right up front on page one, he says precisely what it isn't.
08:56It isn't something mystical, says Schrödinger.
09:00There isn't some magical spark that animates life.
09:04Life is a process.
09:06It's the interaction between matter and energy described by the laws of physics and chemistry,
09:11the same laws that describe the falling of the rain or the shining of the stars.
09:24So the question is, how is it that this magnificent complexity that we call life could have assembled
09:32itself on the surface of the planet which itself formed from nothing more than a collapsing
09:38cloud of gas and dust?
09:47To Schrödinger, the answer had to lie in the way living things process one of the universe's
09:53most elusive properties, energy.
10:19Energy is a concept that's central to physics, but because it's a word that we use every
10:23day, its meaning has got a bit woolly.
10:25I mean, it's easy to say what it is in a sense.
10:28I mean, obviously, this river has got energy because over the decades and centuries, it's
10:32cut this valley through solid rock.
10:37But while this description sounds simple, in reality, things are a little more complicated.
10:43For me, the best definition is that it's the length of the space-time fall vector in the
10:48time direction, but that's not very enlightening, I'll grant you that.
10:56Over the years, the nature of energy has proved notoriously difficult to pin down, not least
11:03because it has the seemingly magical property that it never runs out.
11:07It only ever changes from one form to another.
11:12So we take the water in that waterfall.
11:17At the top of the waterfall, it's got something called gravitational potential energy, which
11:22is the energy it possesses due to its height above the Earth's surface.
11:26See, if I scoop some water out of the river into this beaker, then I'd have to do work
11:33to carry it up to the top of the waterfall.
11:36I'd have to expend energy to get it up there, so it would have that energy as gravitational
11:41potential.
11:42I can even do the sums for you.
11:45Half a litre of water has a mass of half a kilogram.
11:47Multiply by the height, so that's about 5 metres, and the acceleration due to gravity
11:51is about 10 metres per second squared, so that's half times 5 times 10 is 25 joules.
11:58So I'd have to put in 25 joules to carry this water to the top of the waterfall.
12:04Then, if I emptied it over the top of the waterfall, then all that gravitational potential
12:10energy will be transformed into other types of energy.
12:15It's sound, which is pressure waves in the air.
12:18There's the energy of the waves in the river.
12:21And there's heat, so it'll be a bit hotter down there because the water's cascading
12:26into the pool at the foot of the waterfall.
12:28But a key thing is, energy is conserved.
12:31It's not created or destroyed.
12:34So because energy is conserved, if I were to add up all the energy in the water waves,
12:39all the energy in the sound waves, all the heat energy at the bottom of the pool,
12:44then I would find that it would be precisely equal to the gravitational potential energy
12:50at the top of the falls.
12:56What's true for the waterfall is true for everything in the universe.
13:01It's a fundamental law of nature known as the first law of thermodynamics.
13:07And the fact that energy is neither created nor destroyed has a profound implication.
13:15It means energy is eternal.
13:23The energy that's here now has always been here.
13:26The energy that's here now has always been here.
13:29And the story of the evolution of the universe is just the story of the transformation
13:34of the energy from one form to another.
13:37From the origin of the first galaxies to the ignition of the first stars
13:41and the formation of the first planets.
13:45Every single jewel of energy in the universe today
13:49was present at the Big Bang 13.7 billion years ago.
13:57Potential energy held in primordial clouds of gas and dust
14:01was transformed into kinetic energy
14:04as they collapsed to form stars and planetary systems
14:08just like our own sun and moon.
14:11In the sun, heat from the collapse initiated fusion reactions at its core.
14:21Hydrogen became helium.
14:24Nuclear binding energy was released,
14:27heating the atmosphere,
14:29and releasing the gas into the atmosphere.
14:32Hydrogen became helium.
14:35Nuclear binding energy was released,
14:38heating the surface of the sun,
14:41producing the light that began to bathe the young Earth.
14:51And at some point in that story, around four billion years ago,
14:56that transformation of energy led to the origin of the universe.
15:02The origin of life on Earth.
15:23Around 350 kilometres south of Sagada, this is Lake Taal.
15:32Despite its sleepy, languid appearance,
15:35this landscape has been violently transformed by energy.
16:02When I think of a volcano,
16:04I usually think of a pointy, fiery mountain
16:07with a little crater in the top.
16:09It's probably a bit like that one.
16:11But actually, this entire lake is the flooded crater of a giant volcano.
16:16It began erupting only about 140,000 years ago,
16:20and in that time, it's blown 120 billion cubic metres of ash and rock
16:27into the atmosphere.
16:29This crater is 30 kilometres across and in places 150 metres deep.
16:34I mean, that's a cube of rock,
16:37five kilometres by five kilometres by five kilometres,
16:42just blown away.
16:50It's a big volcano.
16:52Taal Lake is testament to the immense power
16:55locked within the Earth at the time of its formation.
17:14Since the late 19th century,
17:17since the lake was created,
17:19a series of further eruptions formed the island in the centre.
17:24And at its heart is a place
17:26where you can glimpse the turmoil of the inner Earth,
17:30where energy from the core still bubbles up to the surface...
17:39..producing conditions similar to those that may have provided
17:44the very first spark of life.
17:59And the water in this lake is different from drinking water
18:03in a very interesting way.
18:05See, if I test this bottle of water with this,
18:10which is called universal indicator paper,
18:13then you see immediately that it goes green
18:17and that means that it's completely neutral.
18:20It's called pH 7 in the jargon.
18:22Then look what happens when I test the water from the lake.
18:29Now the indicator paper stays orange.
18:31In fact, it might have gone a bit more orange.
18:33So that means that this is acid.
18:35It's a bit more acidic.
18:37At the most basic level,
18:39the energy trapped inside the Earth is melting rocks.
18:42And when you melt rock like this, you produce gases.
18:45A lot of carbon dioxide.
18:47In the case of this volcano, a lot of sulphur dioxide.
18:50Now, sulphur dioxide dissolves in water
18:53and you get H2SO4, sulphuric acid.
18:57And that's what we're going to look at today.
19:00Now, sulphur dioxide dissolves in water
19:03and you get H2SO4, sulphuric acid.
19:11Now, what do I mean when I say that the water is acidic?
19:17Well, water is H2O, hydrogen and oxygen, bonded together.
19:22But actually, when it's liquid,
19:24it's a bit more complicated than that.
19:26It's actually a sea of ions.
19:28So H plus ions, that's just single protons,
19:31and OH minus ions, that's oxygen and hydrogen,
19:34bonded together, all floating around.
19:37Now, when something's neutral, when the pH is 7,
19:40then that means that the concentrations of those ions
19:43are perfectly balanced.
19:46When you make water acidic,
19:48then you change the concentration of those ions.
19:51And to be specific, you increase the concentration
19:54of the H plus ions, of the protons.
19:57So this process of acidification
20:00has stored the energy of the volcano
20:03as chemical potential energy.
20:09The volcano transforms heat from the inner earth
20:13into chemical energy
20:15and stores it as a reservoir of protons in the lake.
20:22And this is the same way energy is stored
20:25in a simple battery or fuel cell.
20:32These bottles contain a weak acid
20:35and are connected by a semi-permeable membrane.
20:38Passing an electric current through them
20:41has a similar effect to the volcano's energy
20:44bubbling up into the lake.
20:47It causes protons to build up in one of the bottles.
20:52You can think of it, I suppose, like a waterfall
20:55where the protons are up here waiting to flow down.
20:58And all you have to do to release that energy
21:01and do something useful with it
21:04is complete the circuit,
21:07which I can do by just connecting a motor to it.
21:14There you go. Look at that.
21:17That's the protons cascading down the waterfall
21:20and driving the motor around.
21:28It actually works.
21:31Remarkable, actually.
21:35Now, the fuel cell produces and exploits
21:38its proton gradient artificially.
21:41But there are places on Earth
21:44where that gradient occurs completely naturally.
21:47Here, for example.
21:50So we've got the proton reservoir over there,
21:53the acidic volcanic lake.
21:56If you look that way, there's another lake.
21:59And the reaction of the water with the rocks on the shore
22:02make that lake slightly alkaline,
22:05which is to say that there's a deficit of protons down there.
22:08So here's the waterfall.
22:11The reservoir of protons up there, the deficit down there.
22:14And then you'd have a naturally occurring geological fuel cell.
22:17And it's thought that the first life on our planet
22:20may have exploited the energy
22:23released in those natural proton waterfalls.
22:44What do you think?
22:47It's good, isn't it?
22:55These are pictures from deep below the surface
22:58of the Atlantic Ocean,
23:01somewhere between Bermuda and the Canaries.
23:04And it's a place where you can see
23:07what's going on in the water.
23:10And it's a place where you can see
23:13what's going on in the water.
23:16And it's a place known as the Lost City.
23:19You can see why.
23:22Look at these huge towers of rock,
23:25some of them 50, 60 metres high,
23:28reaching up from the floor of the Atlantic
23:31and into the ocean.
23:34It's what's known as a hydrothermal vent system.
23:37So these things are formed by hot water
23:40And the reason they have begun in such structures
23:43is because these are a very unique kind of hydrothermal vent
23:46called an alkaline vent.
23:49And about 4 billion years ago, when life on Earth began,
23:52seawater would have been mildly acidic.
23:55So here is that proton gradient,
23:58that source of energy for life.
24:01You've got a reservoir of protons in the acidic seawater
24:04and a deficit of protons around the vents.
24:10And the vents don't just provide an energy source.
24:13They're also rich in the raw materials life needs.
24:21Hydrogen gas, carbon dioxide
24:24and minerals containing iron, nickel and sulphur.
24:30But there's more than that.
24:33These vents are porous.
24:36There are little chambers inside them
24:40that can act to concentrate the organic molecules.
24:48You've got everything inside these vents.
24:51You've got concentrated building blocks of life
24:54trapped inside the rock.
25:00And you've got that proton gradient.
25:03You've got that waterfall that provides the energy for life.
25:06So this could be where your distant ancestors come from.
25:11Places like these could be the places
25:14where life on Earth began.
25:22The first living things might have started out
25:25as part of the rock that created them.
25:28Simple organisms
25:31that exploited energy
25:34from the naturally occurring proton gradients in the vents.
25:43And we think this
25:46because living things still get their energy
25:49using proton gradients today.
25:58Deep within ourselves
26:01the chemistry, the first life exploited in the vents
26:04is wrapped up in structures called mitochondria.
26:09Microscopic batteries
26:12that power the processes of life.
26:20This
26:23is the first life
26:26This is a picture
26:29of the mitochondria from a little brown bat.
26:33This is the picture of mitochondria from a plant.
26:36It's actually a member of the mustard family.
26:40This is a picture of mitochondria in bread mould.
26:44And this is mitochondria
26:47inside a malaria parasite.
26:51So the fascinating thing is that
26:54all these animals and plants
26:57and in fact virtually every living thing on the planet
27:00uses proton gradients to produce energy
27:03to live.
27:06Why? Well, the answer is probably
27:09because all these radically different forms of life
27:12share a common ancestor.
27:15And that common ancestor was something
27:18that lived in those ancient undersea vents
27:214 billion years ago where naturally occurring
27:24proton gradients provided the energy
27:27for the first life.
27:30So if you're looking for a universal spark of life
27:33then this is it.
27:36The spark of life is proton gradients.
27:40In those
27:434 billion years
27:46that spark has grown
27:49into a flame.
27:52And a few simple organisms
27:55clustered around a hydrothermal vent
27:58have evolved to produce
28:01all the magnificent diversity
28:04that covers the earth today.
28:07Music
28:30Today life on earth
28:33is so diverse. It covers so much
28:36of the planet that you can find places
28:39like this lake. It's effectively its own
28:42sealed ecosystem. It's salt water, it's connected
28:45to the sea but it's only connected through small
28:48channels through the rock. So that means
28:51that the marine life in here is effectively isolated.
28:54Music
29:06This is the golden jellyfish
29:09a unique subspecies only
29:12found in this one lake on this one island
29:15in the tiny Micronesian Republic
29:18of Palau.
29:21They used to live like most jellyfish
29:24cruising the open ocean catching
29:27tiny creatures, zooplankton
29:30in their long tentacles.
29:33But today their tentacles have all
29:36but disappeared because the golden jellyfish
29:39have evolved to do something that very few
29:42other animals can do.
29:45Music
29:58It really is incredible
30:01There are I want to say millions
30:04of jellyfish as far as you can see all the way down
30:07till the light vanishes there are jellyfish
30:10and you can see them congregating
30:13in the sun. If you go over there to where the lake's
30:16in shade there are just none. And then in this pool of light
30:19beneath the sun there are millions
30:22of them. Beautifully elegant things just
30:25floating around. I'm not being
30:28hyperbolic but it's quite remarkable.
30:54This lake is home to over twenty
30:58million jellyfish
31:03whose success comes down to a remarkable
31:06adaptation.
31:09Their bodies play host to thousands of other
31:12organisms. Photosynthetic algae
31:15that harvest energy directly from sunlight.
31:18The jellyfish engulf the algae
31:21as juveniles and by adulthood
31:24algal cells make up around ten percent
31:27of their biomass.
31:31Grouped into clusters of up to two hundred
31:34individuals they live inside the jellyfish's
31:37own cells.
31:40The golden jellyfish uses algae
31:43to get most of its energy from photosynthesis.
31:46The ones at the surface are gently
31:49turning.
32:10And the ones at the bottom are
32:13Wow, they're gently turning.
32:16The reason they do that is to give all their algae
32:19an equal dose of sunlight.
32:24So they're quite democratic creatures,
32:26just making sure they get as much food as they can.
32:30They just come up to you,
32:31gelling and going around, photosynthesizing.
32:35They tell me they don't sting,
32:45but I'm sure I've got a tingling finger.
32:52And it's not just their anatomy
32:53that's adapted to harvest solar energy.
32:57Every morning, as the sun rises,
33:00the jellyfish begin to swim towards the east.
33:06And as the sun tracks across the sky,
33:10they move back again towards the west,
33:13where they spend their night.
33:19So the jellyfish have this beautiful,
33:23intimate and complex relationship
33:27with the position of the sun in the sky.
33:29As sunlight is captured by their algae,
33:36it's converted into chemical energy.
33:41Energy they use to combine simple molecules,
33:44water and carbon dioxide,
33:47to produce a far more complex one,
33:51glucose.
33:53Once absorbed by the jellyfish,
33:56glucose and other molecules
33:58not only power their daily voyage across the lake,
34:01they provide the basic building blocks
34:04the jellyfish use to grow
34:05the elegant and complex structures of their bodies.
34:19So the jellyfish, through their symbiotic algae,
34:23absorb the light, the energy from the sun,
34:26and they use it to live, to power their processes of life.
34:30And that's true, directly or indirectly,
34:32for every form of life on the surface of our planet.
34:37But things are a little bit more interesting than that,
34:40because energy is neither created nor destroyed.
34:44So life doesn't eat it somehow,
34:47it doesn't use it up,
34:48it doesn't remove it from the universe.
34:51So what does it do?
34:57To understand how energy sustains life,
35:00you have to understand exactly what happens to it
35:03as the cosmos evolves.
35:14In the first instance after the Big Bang,
35:17there was nothing in the universe but energy.
35:26As it changed from one form to another,
35:29galaxies, stars and planets were born.
35:38But while the total amount of energy in the universe
35:40stays constant,
35:42with every single transformation,
35:45something does change.
35:48The energy itself becomes less and less useful.
35:53It becomes ever more disordered.
35:57And you can see this process in action
35:59as energy from the sun hits the surface of the Earth.
36:07So you think about this sand on the beach,
36:09it's been under the glare of the sun all day,
36:11it's been absorbing its light, which has been heating it up,
36:15and now that the sun is dipping below the horizon,
36:17then the sand is still hot to the touch,
36:20because it's re-radiating all the energy that it has absorbed.
36:24It's re-radiating all the energy that it absorbed as heat
36:27back into the universe.
36:29And the key word there is all, all the energy.
36:33See, if it didn't do that,
36:35then it would just gradually heat up day after day after day,
36:38and eventually, I suppose, the whole beach would melt.
36:41So what's changed?
36:43Well, it's the quality of the energy, if you like.
36:47I mean, think about it,
36:49if as much energy is coming back off this sand now
36:51as it absorbed from the sun,
36:53it should be giving me a suntan.
36:55I should need sun cream if I sit looking at this beach all night,
36:58and obviously I don't.
37:00The difference is that this energy is of a lower quality.
37:05It can do less.
37:07It's heat, which is a very low quality of energy indeed.
37:11So what the sand's done is take highly ordered,
37:14high-quality energy from the sun
37:16and convert it to an equal amount
37:19of low-quality, disordered energy.
37:23MUSIC
37:29This descent into disorder is happening across the entire universe.
37:46As time passes,
37:48every single joule of energy is converted into heat.
37:54The universe gradually cools towards absolute zero
37:59until with no ordered energy left,
38:02the cosmos grinds to a halt
38:05and every structure in it decays away.
38:18Yet whilst the universe is dying,
38:21everywhere you look, life goes on.
38:26It's a deep paradox that Schrödinger was well aware of
38:30when he wrote his book in 1943.
38:35How can it be, writes Schrödinger,
38:38that the living organism avoids decay?
38:41In other words, how can it be that life seems to continue to build
38:46increasingly complex structures
38:48when the rest of the universe is falling to bits, is decaying away?
38:53Now, that's a paradox because the universe is falling to bits.
38:59It is tending towards disorder.
39:02That is enshrined in a law of physics
39:05called the second law of thermodynamics.
39:08And I think most physicists believe
39:11that it's the one law of physics that will never be broken.
39:19BUZZING
39:32The key to understanding how life obeys the laws of thermodynamics
39:37is to look at both the energy it takes in
39:40and the energy it gives out.
39:44This is a thermal camera,
39:46so hot things show up as red and cold things show up as blue.
39:51So what you're seeing here is that the chicken is hotter than its surroundings.
39:57Now, heat is a highly disordered form of energy,
40:01so the chicken is radiating disorder out into the wider universe.
40:13But by converting chemical energy into heat,
40:16life transforms energy from an ordered to a disordered form
40:21in exactly the same way as every other process in the universe.
40:33In fact, every single human being
40:36generates 6,000 times more heat per kilogram than the sun.
40:44And it's by converting so much energy from one form to another
40:49that life is able to hang on to a tiny amount of order for itself,
40:55just enough to resist the inevitable decay of the universe.
41:02So it's no accident that living things are hot,
41:05they export heat to their surroundings,
41:08because it's an essential part of being alive.
41:11Living things borrow order from the wider universe,
41:15and then they export it again as disorder.
41:18But it's not precisely in balance.
41:20They have to export more disorder than the amount of order they import.
41:25That is the content of the second law of thermodynamics.
41:28And living things have to obey the second law
41:31because they're physical structures.
41:34They obey the laws of physics.
41:42Just by being alive,
41:44we too are part of the process of energy transformation
41:48that drives the evolution of the universe.
41:54We take sunlight that has its origins at the very start of time
42:00and transform it into heat that will last for eternity.
42:06So far from being a paradox,
42:09living things can be explained by the laws of physics,
42:13the very same laws that describe the falling of the rain
42:17and the shining of the stars.
42:36The dragonfly draws its energy from proton gradients,
42:41the fundamental chemistry that powers life.
42:49But the real miracles are the structures they build with that energy.
42:56Borrowing order to generate cells,
43:00arranging those cells into tissues,
43:04and those tissues into the intricate architecture of their bodies.
43:12So we've developed a quite complex system of structures
43:16that are built on the basis of the laws of physics.
43:21So we've developed a quite detailed understanding
43:25of the underlying machinery that powers these dragonflies
43:29and indeed all life on Earth.
43:31And whilst we don't have all the answers,
43:34it is certainly safe to say that there's no mysticism required.
43:38You don't need some kind of magical flame
43:41to animate these little machines.
43:43They operate according to the laws of physics
43:46and I think they're no less magical for that.
43:50Yet the dragonfly will only maintain this delicate balancing act for so long,
43:57because all living things share the same fate.
44:06Each individual will die.
44:11But life itself endures.
44:15This is because there's something that separates life
44:18from every other process in the universe.
44:22This is because there's something that separates life
44:25from every other process in the universe.
44:52This is the Malaysian state of Sabah,
44:55on the northern tip of the island of Borneo.
44:59It's one of the most biodiverse places on the planet.
45:05Home to 15,000 plant species,
45:103,000 species of tree,
45:14420 species of bird,
45:17and 222 species of mammals.
45:29Borneo's rainforests contain trees
45:32that are thought to live for more than 1,000 years.
45:39But the forest itself has existed for tens of millions of years.
45:48The reason it persists
45:51is because each generation of animal and plant
45:54passes the information to recreate itself
45:57onto the next generation.
46:01And that's possible because of a molecule
46:04found in every cell of every living thing.
46:09A molecule called DNA.
46:18BIRDS CHIRP
46:26Now, all I need to isolate my DNA
46:29is some washing-up liquid,
46:32a bit of salt,
46:35and the chemist's best friend, vodka.
46:39Now, to get a sample of DNA,
46:42I can just use myself.
46:45On the edge of my cheek,
46:48I'll dislodge some cheek cells into my saliva.
46:57I missed the test tube.
47:00There we are. It's a physicist doing an experiment.
47:08Then I add a bit of washing-up liquid.
47:12Now, what this will do
47:15is it will break open those cheek cells
47:18and it will also degrade the membrane
47:21that surrounds the cell nucleus that contains the DNA.
47:26Salt will encourage the molecules to clump together.
47:32DNA is insoluble in alcohol.
47:36So you should get a layer of alcohol
47:42with the DNA molecules precipitated out.
47:50Yeah.
47:53There, can you see those strands of white?
47:58And so in that cloudy, almost innocuous-looking solid
48:03are all the instructions needed
48:06to build a human being.
48:13So that is what makes life unique.
48:28Only living things have the ability
48:31to encode and transmit information in this way.
48:37And the consequences of that
48:40affect our understanding of what it is to be alive.
48:45This rainforest is part of the Sepiloc Forest Reserve
48:48and in here somewhere
48:51are some of our closest genetic relatives.
48:55Shh, shh.
48:59There, there, can you see?
49:08Orangutans are highly specialised
49:11for a life living in the rainforest.
49:15They live in the rainforest
49:18and they live in the forest
49:21Orangutans are highly specialised
49:24for a life lived in the forest canopy.
49:27Their arms are twice as long as their legs
49:30and all four limbs are incredibly flexible.
49:34Each one ending in a hand
49:37whose curved bones are perfectly adapted
49:40for gripping branches.
49:45These adaptations are encoded
49:48and information passed down in their DNA.
49:56You've got a hat on.
50:00He has actually just put a hat on.
50:04This is the orangutan's genetic code.
50:07It was published in 2011
50:10and there are over 3 billion letters in it.
50:13and there are over 3 billion letters in it.
50:16If I flip through it...
50:19Look at that.
50:22It's got a lot of letters in it.
50:25It's got a lot of letters in it.
50:28It's got a lot of letters in it.
50:32Look at that.
50:35Now it's composed of only four letters
50:38A, C, T and G
50:41which are known as bases.
50:44They're chemical compounds.
50:47They're molecules and the way it works
50:50is beautifully simple.
50:53They're grouped into threes called codons
50:56and some of them just tell the code reader
50:59when it's going to start and when it's going to stop.
51:02when it's going to start and when it's going to stop.
51:05This is fast.
51:08This is fast.
51:11So you'd have a start and a stop.
51:14In between, each group of three
51:17codes for a particular amino acid.
51:20Now amino acids
51:23are the building blocks of proteins
51:26and they're the building blocks of all living things.
51:29So you would just read along.
51:32You'd find a start-stop
51:35and then you'd go along in threes
51:38building amino acid, building amino acid
51:41building amino acid, building amino acid
51:44stitch those together into a protein
51:47and if you keep doing that, eventually
51:50you'll come out with one of those.
51:53Simple of course, but the basics
51:56are there.
51:59This code written in there
52:02had instructions to make him.
52:13To faithfully reproduce those instructions
52:16generation after generation
52:19the orangutans and indeed all life on earth
52:22rely on a remarkable property of DNA
52:25its incredible stability
52:28and resistance to change.
52:34Every time a cell divides its DNA must be copied
52:37and the genetic code is highly
52:40resistant to copying errors.
52:43The little enzymes, the chemical machines that do the copying
52:46on average make only one mistake in a billion letters.
52:50That's like copying out the Bible about 280 times
52:53and making just one mistake.
52:59That fidelity means adaptations
53:02are faithfully transmitted from parent
53:05to offspring
53:08and so while we think of evolution as a process
53:11of constant change, in fact
53:14the vast majority of the code is preserved.
53:18So even though we're separated from the orangutans
53:21by nearly 14 million years of evolution
53:24what's really striking
53:27is just how similar we are
53:30and those similarities are far more than skin deep.
53:36Orangutans are surely one of the most
53:39human of animals
53:42and they share many behavioral traits
53:46that you would define as being uniquely human.
53:51They nurture their young for eight years
53:54before they let them go on their own into the forest.
53:57In that time the infants learn which fruits are safe to eat
54:00and which are poisonous
54:03which branches will hold their weight and which won't.
54:06And they can do all that because they have memory
54:09they can remember things that happened to them in their life
54:12they can learn from them and they can pass them on
54:15from generation to generation.
54:24And that deep connection extends far beyond
54:27our closest relatives
54:30because our DNA contains the fingerprint
54:33of almost four billion years of evolution.
54:43If I draw a tree of life for the primates
54:46then we share a common ancestor
54:49with the chimps and bonobos
54:52about four to six million years ago
54:55and if you compare
54:58our genetic sequences
55:01you find that our genes
55:04are 99% the same.
55:07We go back to the split
55:10with gorillas about six to eight million years ago
55:13and again if you compare
55:16our genes then you find that they are
55:1998.4% the same.
55:22Back in time again
55:25common ancestor with our friends over there the orangutans
55:28then our genes
55:31are 97.4% the same
55:34and you could carry on all the way back in time
55:37you could look for our common ancestor with a chicken
55:40and you'd find that our codes
55:43are about 60% the same
55:46and in fact if you look for any animal
55:49like a little fly or a bacteria
55:52something that seems superficially completely unrelated to us
55:55then you will still find sequences in the genetic code
55:58which are identical to sequences in my cells.
56:01So this tells us that
56:04all life on earth is related
56:07it's all connected through our genetic code.
56:20DNA is the blueprint for life
56:24but its extraordinary fidelity
56:27means it also contains a story
56:30and what a story it is.
56:35The entire history of evolution
56:38from the present day all the way back
56:41to the very first spark of life
56:47and it tells us that we are connected
56:50not only to every plant and animal alive today
56:54but to every single thing
56:57that has ever lived.
57:04The question what is life
57:07is surely one of the grandest of questions
57:10and we've learnt that life isn't really a thing
57:13at all.
57:16It's a collection of chemical processes
57:19that can harness a flow of energy
57:22to create life on earth
57:25and we've learnt that life
57:28isn't really a thing at all
57:31it's a collection of chemical processes
57:34that can harness a flow of energy
57:37to create local islands of order
57:40like me and this forest
57:43by borrowing order from the wider universe
57:46and then transmitting it from generation to generation
57:49through the elegant chemistry of DNA
57:52and the origins of that chemistry
57:55can be traced back 4 billion years
57:58and most wonderfully of all
58:01the echoes of that history
58:04stretching back for a third of the age of the universe
58:07can be seen in every cell
58:10of every living thing on earth
58:13and that leads to what I think is the most exciting idea of all
58:16because far from being some chance event
58:19ignited by a mystical spark
58:22the emergence of life on earth
58:25is a consequence of the laws of physics
58:28and if that's true then a living cosmos
58:31might be the only way our cosmos can be.
58:48Just remember
58:51you're a tiny little person on a planet
58:54in a universe expanding and immense
58:57that life began evolving and dissolving
59:00and resolving in the deep primordial oceans
59:03by the hydrothermal vents
59:06our earth which had its birth almost 5 billion years ago
59:09Stay with us on BBC HD
59:12our series Racing Legends continues next tonight
59:15with Olympic cycling hero Chris Hoy
59:18swapping bicycle for rally car
59:21I'm Sarah Gray
59:24.