0:00:02 > 0:00:07This programme contains some scenes which some viewers may find upsetting
0:00:07 > 0:00:11The natural world is beautiful but complex.
0:00:17 > 0:00:19The skies dance with colour.
0:00:19 > 0:00:22Yay! Yes!
0:00:22 > 0:00:24Shapes form...
0:00:25 > 0:00:27..and disappear.
0:00:30 > 0:00:34But this seemingly infinite complexity
0:00:34 > 0:00:37is just a shadow of something deeper -
0:00:37 > 0:00:39the underlying laws of nature.
0:00:46 > 0:00:48The world is beautiful to look at
0:00:48 > 0:00:51but it's even more beautiful to understand.
0:01:22 > 0:01:25Watch out for the brambles.
0:01:30 > 0:01:34It's a fact, and one of the great mysteries about our universe,
0:01:34 > 0:01:38that everything is made out of a few simple building blocks
0:01:38 > 0:01:40that interact with each other
0:01:40 > 0:01:42according to a few simple laws of nature.
0:01:42 > 0:01:44And that applies to everything,
0:01:44 > 0:01:49to stars and planets and galaxies and rocks and oceans,
0:01:49 > 0:01:51but also to living things.
0:01:51 > 0:01:55And that raises an intriguing possibility.
0:01:55 > 0:02:00By looking carefully at nature, by doing science,
0:02:00 > 0:02:05we might be able to understand what life is,
0:02:05 > 0:02:08and, just perhaps, how it began.
0:02:10 > 0:02:15The origin of life is one of the great unsolved scientific mysteries.
0:02:15 > 0:02:18Let's go by the tree. There might be some over there.
0:02:20 > 0:02:23Its origins seem to be lost in the mists of time.
0:02:25 > 0:02:27I've got a really pretty one here.
0:02:27 > 0:02:29But in common with many scientific mysteries,
0:02:29 > 0:02:34there may be answers if you ask simple questions.
0:02:34 > 0:02:37Why do moths like flying into the light so much?
0:02:37 > 0:02:39Do they do it...
0:02:39 > 0:02:43so they can spread out their wings and get warm?
0:02:45 > 0:02:48What's the deepest question you can ask about a moth?
0:02:48 > 0:02:52I think it's "how did it come to exist in the first place?"
0:02:54 > 0:02:57We can't go back to the origin of life on Earth -
0:02:57 > 0:02:59we don't have a time machine,
0:02:59 > 0:03:05but we do have the moth and every living thing on the planet today.
0:03:05 > 0:03:07And these are like little history books.
0:03:07 > 0:03:11Their story, four billion years of life on Earth,
0:03:11 > 0:03:14is written into every cell in its body.
0:03:14 > 0:03:20So in order to discover the spark of life, the origin of the flame,
0:03:20 > 0:03:23we just have to learn to read the book.
0:03:28 > 0:03:29It's gone.
0:03:32 > 0:03:37Living things are far too complex to understand in one go...
0:03:41 > 0:03:45..so we have to break the problem down into simple questions.
0:03:52 > 0:03:55What are the ingredients of life?
0:03:59 > 0:04:02How does complex life form from such simple ingredients?
0:04:07 > 0:04:09And what was the driving force,
0:04:09 > 0:04:11the energy source that ignited the flame,
0:04:11 > 0:04:13four billion years ago?
0:04:23 > 0:04:28For the first 500 million years of Earth's history, there was no life,
0:04:28 > 0:04:32just the volcanic violence of a restless, young planet
0:04:32 > 0:04:36and the bombardment of countless meteorites from space.
0:04:36 > 0:04:38But somewhere, somehow,
0:04:38 > 0:04:42the ingredients of the planet were transformed.
0:04:42 > 0:04:44Inanimate became animate
0:04:44 > 0:04:49and, once ignited, that spark has never been extinguished.
0:04:49 > 0:04:53We are searching for our ancestor from a time when there was no life.
0:04:56 > 0:04:59If we are to understand how life emerged
0:04:59 > 0:05:02from the ingredients present on the young Earth,
0:05:02 > 0:05:06we must first explore what those ingredients are -
0:05:06 > 0:05:08what the Earth is made from.
0:05:22 > 0:05:24There are very few places on our planet
0:05:24 > 0:05:27where the pure ingredients of the Earth can be seen.
0:05:29 > 0:05:33But here, beside a lake of sulphuric acid,
0:05:33 > 0:05:36one of the basic building blocks of the planet boils to the surface.
0:05:42 > 0:05:46This volcano delivers a valuable, pure substance -
0:05:46 > 0:05:47sulphur.
0:05:49 > 0:05:51Emerging at over 200 degrees Celsius...
0:05:55 > 0:05:59..it's an alien-looking cauldron of chemistry.
0:06:06 > 0:06:11Bagio and his father Budi go to work on the volcano every day.
0:06:12 > 0:06:15They labour to protect the precious, pure sulphur.
0:06:44 > 0:06:47This crater is a working sulphur mine.
0:06:50 > 0:06:51Sulphur's valuable
0:06:51 > 0:06:54because it gets used in the manufacture of many products,
0:06:54 > 0:06:57from sugar to medicine.
0:06:57 > 0:07:00But keeping the sulphur pure is not easy,
0:07:00 > 0:07:04because it readily catches fire and transforms into sulphur dioxide,
0:07:04 > 0:07:07a noxious gas.
0:07:09 > 0:07:12Bagio and Budi are here to fight the fires.
0:07:34 > 0:07:37It's rare to find the elements in their pure form,
0:07:37 > 0:07:40because they tend to react with other elements.
0:07:41 > 0:07:46In the heat of the volcano, sulphur reacts with oxygen in the air.
0:07:46 > 0:07:47It burns.
0:08:02 > 0:08:04Sulphur burns blue.
0:08:06 > 0:08:08Working in the dark,
0:08:08 > 0:08:11the firefighters can see the flames clearly.
0:08:16 > 0:08:19And it's their job to prevent them from spreading.
0:09:05 > 0:09:09Sulphur is an element that is essential to life.
0:09:09 > 0:09:11All living things need it.
0:09:18 > 0:09:23But here, in such large quantities, ignited by an active volcano,
0:09:23 > 0:09:25it becomes toxic.
0:09:32 > 0:09:35On contact with water in the eyes and mouth,
0:09:35 > 0:09:40the gaseous sulphur dioxide from the flames turns into sulphuric acid.
0:10:38 > 0:10:43Sulphur is one of the 92 naturally occurring chemical elements.
0:10:46 > 0:10:50There's no difference between the sulphur in the wings of a moth...
0:10:52 > 0:10:55..and the sulphur that pours out of a volcano...
0:11:01 > 0:11:03..or the sulphur in you and me.
0:11:05 > 0:11:08We are made of the same stuff as our planet
0:11:08 > 0:11:10and there's no mystery in that.
0:11:10 > 0:11:15It has to be so, because life emerged from the planet.
0:11:23 > 0:11:27Hydrogen atoms, carbon atoms, oxygen and sulphur atoms.
0:11:27 > 0:11:33These basic building blocks react and combine to make everything.
0:11:34 > 0:11:37A woodland is a complex place.
0:11:37 > 0:11:41There are oak trees and grass and mosses and ferns
0:11:41 > 0:11:43and countless animals and plants
0:11:43 > 0:11:46all living together in a tangled ecosystem.
0:11:46 > 0:11:50But there's a simpler level of description.
0:11:50 > 0:11:53Everything is made of atoms.
0:11:53 > 0:11:56So an oak tree is really just carbon, nitrogen,
0:11:56 > 0:12:00oxygen and hydrogen, and a few other bits mixed together.
0:12:00 > 0:12:03So, when you look at it like that,
0:12:03 > 0:12:05it's not really that complicated at all.
0:12:14 > 0:12:16The atoms that make up this woodland
0:12:16 > 0:12:19have been on an extraordinary journey to get here.
0:12:21 > 0:12:23Think of a carbon atom in this acorn.
0:12:23 > 0:12:27It was assembled in the heart of a star billions of years ago
0:12:27 > 0:12:30out of protons that were built just after the Big Bang.
0:12:30 > 0:12:34It got thrown out into the universe in a supernova explosion,
0:12:34 > 0:12:38collapsed as part of a dust cloud to form the Sun and then the Earth,
0:12:38 > 0:12:40four and half billion years ago.
0:12:40 > 0:12:43It will have spent a lot of time in rocks.
0:12:43 > 0:12:47It was probably part of some of the first living things on Earth.
0:12:47 > 0:12:51It would have got breathed out as carbon dioxide by someone
0:12:51 > 0:12:53that walked through this wood 400 years ago.
0:12:53 > 0:12:56It will have got into some ancient oak tree
0:12:56 > 0:12:59through the action of photosynthesis,
0:12:59 > 0:13:02constructed into this acorn, fallen down to the ground
0:13:02 > 0:13:07and there it is. It's got a history that goes back billions of years.
0:13:07 > 0:13:11In fact, a history, in terms of the building blocks of carbon,
0:13:11 > 0:13:14the protons, that goes back right to the origin of the universe.
0:13:14 > 0:13:16And in billions of years' time,
0:13:16 > 0:13:19when the Sun dies and the Earth is vaporised,
0:13:19 > 0:13:22it will be thrown back out into space
0:13:22 > 0:13:25and probably condensed into a new world,
0:13:25 > 0:13:27billions of years in the future.
0:13:27 > 0:13:30So life is just a temporary home
0:13:30 > 0:13:34for the immortal elements that build up the universe.
0:13:41 > 0:13:43The atoms are building blocks.
0:13:43 > 0:13:46They combine to make molecules,
0:13:46 > 0:13:49some of which are terrifically intricate and complex.
0:13:52 > 0:13:55The DNA molecules in the cells in your body
0:13:55 > 0:13:58are made up of billions of atoms linked together,
0:13:58 > 0:14:01carrying the genetic code to make you.
0:14:07 > 0:14:10Exactly how this complexity emerged is still debated,
0:14:10 > 0:14:13but everyone agrees on one thing.
0:14:16 > 0:14:20There was a very special theatre from which biology emerged.
0:14:28 > 0:14:30A vital ingredient for life.
0:14:33 > 0:14:36And these children know where to find it.
0:14:59 > 0:15:03The elements hydrogen and oxygen combine to make water,
0:15:03 > 0:15:05H2O.
0:15:09 > 0:15:11Hidden deep in this forest...
0:15:14 > 0:15:16..is a rare and magical sight...
0:15:20 > 0:15:24..that only exists because of a unique property of water.
0:15:28 > 0:15:31A property that makes it essential to life on Earth.
0:15:37 > 0:15:42Biologist Tom Iliffe has brought a specialist team here to find it.
0:15:42 > 0:15:45This limestone is fantastic here.
0:15:45 > 0:15:48The way it's pockmarked and dissolved away
0:15:48 > 0:15:51indicates that there is a lot of water moving underneath.
0:15:57 > 0:16:00- We'll kill ourselves if we go down that way.- Yeah, it's slippery.
0:16:00 > 0:16:03- I'll slide on my ass. - We'll go that way, yeah.
0:16:03 > 0:16:05Only a handful of divers have the skill
0:16:05 > 0:16:07to explore this network of caves.
0:16:09 > 0:16:12So, you're going to need those two and this one, yeah?
0:16:34 > 0:16:40These caves are one of the last true undiscovered, unexplored,
0:16:40 > 0:16:42unknown frontiers on the planet Earth.
0:16:47 > 0:16:52Very few people, very few scientists go out and do anything
0:16:52 > 0:16:55any more dangerous than what we're doing in cave diving.
0:17:06 > 0:17:12This underground cave system exists because water, the liquid we drink,
0:17:12 > 0:17:14can eat through solid rock.
0:17:21 > 0:17:25It makes easy work of the soft limestone
0:17:25 > 0:17:28and makes things exceptionally fragile.
0:17:38 > 0:17:42Worst thing is, your tanks may wedge in
0:17:42 > 0:17:44and literally stick you in a spot...
0:17:46 > 0:17:50..where you can't move forward or backward.
0:18:15 > 0:18:18A little bit distracting when you're trying to do something underwater
0:18:18 > 0:18:22to have the cave collapsing in on you.
0:18:23 > 0:18:26Hey there! Welcome back. Glad to see you!
0:18:26 > 0:18:29Oh, man. That tight spot in there!
0:18:29 > 0:18:30I could barely fit through!
0:18:30 > 0:18:33Even worse is rocks that get dislodged.
0:18:33 > 0:18:35When they fall down, it brings down a huge amount of...
0:18:35 > 0:18:39- I say we leave it 24 hours at least, so it clears up.- OK, OK.
0:18:39 > 0:18:40Then come back, give it another go.
0:18:40 > 0:18:43You will lose your own visibility within seconds.
0:18:43 > 0:18:46So there's not much time to stop and hover and think.
0:19:06 > 0:19:10The reason why we go through these narrow slots,
0:19:10 > 0:19:13why we push our bodies to the limits,
0:19:13 > 0:19:16is to find something majestic,
0:19:16 > 0:19:19something beautiful on the other side.
0:19:19 > 0:19:22But unless you go there, unless you look, you're never going to know.
0:19:30 > 0:19:35Deeper into the cave system, suddenly, the water changes.
0:19:48 > 0:19:54Underneath the forest, miles from the coast, they've found the ocean.
0:19:56 > 0:19:58It's able to flow underground,
0:19:58 > 0:20:01working through the pores and fissures in the limestone
0:20:01 > 0:20:05to end up here, where the denser, salty sea water sinks
0:20:05 > 0:20:08below the less dense freshwater,
0:20:08 > 0:20:14creating a boundary, a beautiful phenomenon known as a halocline.
0:20:20 > 0:20:22Now we're in sea water.
0:20:22 > 0:20:26We've reached the ocean, the underground ocean in planet Earth.
0:20:28 > 0:20:35We can see the movement of water, freshwater going toward the ocean,
0:20:35 > 0:20:37saltwater being sucked inland.
0:20:46 > 0:20:50Water dissolves more substances than any other liquid.
0:20:52 > 0:20:55It does this because it's a polar molecule.
0:20:55 > 0:20:59It has positive and negatively charged regions
0:20:59 > 0:21:03and these can disrupt the forces that bind other molecules together.
0:21:09 > 0:21:12Bacteria that line the cave walls
0:21:12 > 0:21:15feed on the nutrients dissolved in the water.
0:21:16 > 0:21:20You can see these stringy bacteria hanging down
0:21:20 > 0:21:23and they kind of wave in the breeze as you fly by.
0:21:28 > 0:21:32The bacteria in turn, are food for other life.
0:21:33 > 0:21:36Even in these dark, isolated environments,
0:21:36 > 0:21:38with no direct sunlight to power it,
0:21:38 > 0:21:41a complex ecosystem can be supported.
0:21:42 > 0:21:45It's why, as far as we know,
0:21:45 > 0:21:48where there's water on Earth, there's life.
0:22:15 > 0:22:19Our blue planet is an interconnected matrix of rivers and oceans...
0:22:26 > 0:22:30..transporting the dissolved ingredients of the Earth
0:22:30 > 0:22:32that are integral to life.
0:22:39 > 0:22:43The salts and nutrients that are carried around our planet...
0:22:47 > 0:22:50..are also transported through our bodies in water.
0:22:58 > 0:23:00It's an intimate connection
0:23:00 > 0:23:04that every living thing shares with our blue planet.
0:23:04 > 0:23:07Water delivers the ingredients of life.
0:23:18 > 0:23:20Water is a simple molecule,
0:23:20 > 0:23:24a couple of hydrogen atoms and an oxygen atom stuck together,
0:23:24 > 0:23:28but its simplicity hides a wealth of complex chemistry.
0:23:31 > 0:23:34The chemistry that makes life possible.
0:23:36 > 0:23:39Hydrogen is the simplest chemical element.
0:23:39 > 0:23:42Its atoms consist of a single proton -
0:23:42 > 0:23:44it's called the atomic nucleus -
0:23:44 > 0:23:47surrounded by a single electron.
0:23:47 > 0:23:52Oxygen is a nucleus of eight protons and eight neutrons,
0:23:52 > 0:23:55surrounded by eight electrons.
0:23:55 > 0:24:00Now, the nucleus is extremely small compared to an atom.
0:24:00 > 0:24:03If a nucleus were about that big, let's say,
0:24:03 > 0:24:08then the cloud of electrons would stretch out way beyond that castle.
0:24:08 > 0:24:12Atoms are almost completely empty space.
0:24:19 > 0:24:24Now, the way that the elements combine is determined entirely
0:24:24 > 0:24:27by the way that the electrons arrange themselves
0:24:27 > 0:24:29around the nucleus.
0:24:29 > 0:24:34And that's just down to the basic fundamental laws of nature
0:24:34 > 0:24:37that describe the way our universe is constructed.
0:24:37 > 0:24:38It's very simple.
0:24:38 > 0:24:45So, an oxygen nucleus has room around it for ten electrons,
0:24:45 > 0:24:47but it only has eight.
0:24:47 > 0:24:51That means that two hydrogen atoms can come floating in
0:24:51 > 0:24:55and share their single electron with the oxygen,
0:24:55 > 0:24:57and that fills up the oxygen's outer slots
0:24:57 > 0:25:01and fills up the hydrogen slots as well.
0:25:01 > 0:25:04Oxygen. Hydrogen. H2O.
0:25:04 > 0:25:07Everything is happy and you get a molecule of water,
0:25:07 > 0:25:09which has radically different properties
0:25:09 > 0:25:11to the elements on their own.
0:25:11 > 0:25:14Oxygen's just a colourless, odourless gas.
0:25:14 > 0:25:17Hydrogen is a colourless, odourless gas.
0:25:17 > 0:25:22Stick them together to share those electrons, and you get that stuff.
0:25:22 > 0:25:26One of the most complex substances in the known universe.
0:25:26 > 0:25:30The theatre that allows life to exist.
0:25:39 > 0:25:42Water is the universal solvent.
0:25:48 > 0:25:51It carries the ingredients of life.
0:25:57 > 0:26:00Ingredients that are so important that living things
0:26:00 > 0:26:04will go to extraordinary lengths to get hold of them.
0:26:12 > 0:26:14It's the end of the Alpine winter.
0:26:16 > 0:26:19This female ibex has one thing in mind.
0:26:22 > 0:26:24Kids.
0:26:27 > 0:26:30She's leading her family down from the snow line
0:26:30 > 0:26:33in search of a life-giving ingredient.
0:26:36 > 0:26:39And it's a search that's not without its risks.
0:26:48 > 0:26:52Rada Bionda is a conservationist who studies the ibex.
0:27:15 > 0:27:19At first glance, the ibex have everything they need.
0:27:19 > 0:27:21They have food and water.
0:27:23 > 0:27:26But the mother knows instinctively not enough.
0:27:26 > 0:27:29She's craving something else.
0:27:29 > 0:27:32And she'll take risks to get it.
0:27:59 > 0:28:01The rock that was used to build this dam
0:28:01 > 0:28:06contains essential minerals that have been dissolved in water.
0:28:08 > 0:28:13Minerals rich in the calcium that these animals need to stay strong.
0:28:16 > 0:28:19And they'll scale a dam to get them.
0:28:35 > 0:28:39Without these salts and minerals, their bones won't grow.
0:28:39 > 0:28:42Their nervous systems and muscles can't function.
0:28:45 > 0:28:47Movement and co-ordination can falter.
0:29:03 > 0:29:07There's a strong bond between mother and kid,
0:29:07 > 0:29:10and the kid will follow her wherever she goes.
0:30:33 > 0:30:36The ibex eventually make it to the prize.
0:30:49 > 0:30:53Salt from the Earth dissolved in water
0:30:53 > 0:30:56continues on its journey into their bodies...
0:31:06 > 0:31:09..where it's used in the nerves and muscles
0:31:09 > 0:31:12that control dextrous, pincer-like hooves.
0:31:19 > 0:31:23Vital ingredients carried around by a simple molecule
0:31:23 > 0:31:26with remarkable properties.
0:31:35 > 0:31:38If water is the theatre of life,
0:31:38 > 0:31:41then the actors are the atoms and molecules
0:31:41 > 0:31:45that form the structures of living things themselves.
0:31:49 > 0:31:52There are only about 15 or so
0:31:52 > 0:31:55that are vitally important for living things.
0:31:55 > 0:31:59There are the obvious ones like carbon, nitrogen, oxygen,
0:31:59 > 0:32:03but also some strange ones, like rubidium,
0:32:03 > 0:32:05or an element called molybdenum.
0:32:09 > 0:32:13The reactions between the elements are the same
0:32:13 > 0:32:15in living and nonliving things,
0:32:15 > 0:32:20but life fine-tunes and controls the basic chemistry of the Earth
0:32:20 > 0:32:22to do extraordinary things.
0:32:56 > 0:33:01Moiswa and her family are preparing for a once-in-a-lifetime ceremony...
0:33:03 > 0:33:06..centred around the chemistry of one element.
0:33:09 > 0:33:10Iron.
0:33:13 > 0:33:16It lies at the heart of Maasai culture,
0:33:16 > 0:33:18in their land and in their blood.
0:33:28 > 0:33:32Tomorrow, Moiswa's son Ndika will become an elder.
0:33:50 > 0:33:52The family are almost ready for their guests
0:33:52 > 0:33:56but there's something they must first collect from the land.
0:34:16 > 0:34:18They are looking for red ochre,
0:34:18 > 0:34:23a traditional pigment that has been in use for over 100,000 years.
0:34:37 > 0:34:40The rock's red colour comes from iron,
0:34:40 > 0:34:43which makes up a third of our planet's mass,
0:34:43 > 0:34:46most of it locked away in the Earth's molten core.
0:34:58 > 0:35:01The iron here is not in its pure form.
0:35:01 > 0:35:05It's combined with oxygen to form iron oxide,
0:35:05 > 0:35:10a red compound that, tomorrow, will provide the colour of celebration.
0:36:01 > 0:36:05This is the ceremony that will mark Ndika's transition into elderhood.
0:36:08 > 0:36:09A bull will be slaughtered...
0:36:12 > 0:36:14..and he'll drink its blood.
0:36:30 > 0:36:35Just like the red ochre from the Earth, the blood is rich in iron.
0:37:03 > 0:37:08Today, for Ndika, blood symbolises power and strength.
0:37:08 > 0:37:12Surrounded by his people, decorated in ochre,
0:37:12 > 0:37:13iron oxide.
0:37:29 > 0:37:32It's a proud moment for Ndika and his family.
0:37:34 > 0:37:38Wherever there is iron and oxygen, they can react,
0:37:38 > 0:37:41whether it's in the veins of the Earth or the arteries of life.
0:37:56 > 0:38:00Whether it's in you and me or the rocks of the Earth,
0:38:00 > 0:38:03the fundamental chemistry is the same.
0:38:09 > 0:38:13But the way life uses chemistry is exquisite.
0:38:19 > 0:38:23Just think about the reaction between iron and oxygen in blood...
0:38:27 > 0:38:29..and rust.
0:38:30 > 0:38:34Iron is an atom that really would like to, if it could,
0:38:34 > 0:38:37get rid of a few electrons.
0:38:37 > 0:38:41Oxygen, on the other hand, is an atom that would like, if it can,
0:38:41 > 0:38:43to receive some electrons.
0:38:43 > 0:38:46So if you put them together,
0:38:46 > 0:38:49and they stick together, that's what we call rust.
0:38:53 > 0:38:57And the process that makes our blood red is similar.
0:38:57 > 0:39:00We're almost rusting, but not quite.
0:39:00 > 0:39:04One of the jobs of your blood is to take oxygen from your lungs
0:39:04 > 0:39:07and transport it around your body to where it's needed.
0:39:07 > 0:39:10So that means you need some structure
0:39:10 > 0:39:15that can bind oxygen to it, but quite gently,
0:39:15 > 0:39:18so that it can be carried to where it's needed
0:39:18 > 0:39:20and then released, easily.
0:39:20 > 0:39:24Well, iron likes to stick to oxygen,
0:39:24 > 0:39:27so in your blood you have iron atoms
0:39:27 > 0:39:30but they are surrounded by nitrogen atoms, four of them,
0:39:30 > 0:39:34and that's surrounded by a big ring of carbon and oxygen atoms.
0:39:34 > 0:39:36That whole thing is called haem.
0:39:36 > 0:39:38And then four of those are stuck together,
0:39:38 > 0:39:40and that thing is called haemoglobin.
0:39:40 > 0:39:45Its job is to carry oxygen around and when the oxygen attaches,
0:39:45 > 0:39:48your blood turns a much brighter red.
0:39:48 > 0:39:52And then the haemoglobin can carry that oxygen around,
0:39:52 > 0:39:56but because of that structure, it's so delicately tuned
0:39:56 > 0:39:59that when the oxygen gets to where it's needed,
0:39:59 > 0:40:02in your brain, for example, it can be taken off.
0:40:02 > 0:40:05Your blood gets less red and goes back to your lungs
0:40:05 > 0:40:07to get some more oxygen.
0:40:07 > 0:40:13So, biology is really about using the natural chemical reactions
0:40:13 > 0:40:17of the elements, but tempering them and fine-tuning them
0:40:17 > 0:40:20with intricate and complex structures
0:40:20 > 0:40:22in order to do something useful,
0:40:22 > 0:40:25which, in your case, is to live.
0:40:38 > 0:40:40We are of the Earth...
0:40:42 > 0:40:47..constructed from a ready supply of chemical elements
0:40:47 > 0:40:49forged in the stars.
0:40:51 > 0:40:55Elements that react on our oxygen-rich planet
0:40:55 > 0:40:59and play their roles in the theatre of life.
0:40:59 > 0:41:01Water.
0:41:01 > 0:41:05But there's one more vital thing life needs -
0:41:05 > 0:41:06energy.
0:41:11 > 0:41:14The final clue we need to search for the origin of life...
0:41:17 > 0:41:22..can be found in the details of how living things control energy.
0:41:38 > 0:41:43Every year, between March and June, an animal rises from the deep.
0:41:51 > 0:41:54It harnesses the chemistry inside its cells
0:41:54 > 0:41:57to produce an almost supernatural display.
0:42:01 > 0:42:05For the locals, this alchemy makes the creature a delicacy.
0:42:08 > 0:42:13But for fishermen like Mr Urakami, it makes them highly profitable.
0:42:31 > 0:42:33Mr Urakami is banking on this
0:42:33 > 0:42:36being the most lucrative catch of the year.
0:42:37 > 0:42:39And it's not fish he's after.
0:43:16 > 0:43:20Away from the fishing boats, these people are having a bit more luck.
0:43:23 > 0:43:27Glowing lights signal the arrival of the firefly squid.
0:43:35 > 0:43:39Tiny organs called photophores emit a deep blue light.
0:43:39 > 0:43:44In the depths, this light may be used to attract prey
0:43:44 > 0:43:47but the greatest light show is saved for the shallows
0:43:47 > 0:43:49where they come up to spawn.
0:44:06 > 0:44:08It's a one-way trip.
0:44:09 > 0:44:12After they've spent their last remaining energy,
0:44:12 > 0:44:16their glow fades as they give themselves up to the tide.
0:44:19 > 0:44:22Out at sea, the squid are also rising.
0:45:08 > 0:45:11The squid are exploiting something fundamental -
0:45:11 > 0:45:15chemical reactions can release energy.
0:45:15 > 0:45:19Here the energy is released thanks to the reactive nature of oxygen.
0:45:26 > 0:45:28It wants to combine with other elements
0:45:28 > 0:45:31in a reaction known as oxidation.
0:45:31 > 0:45:35In the squid, biological molecules called luciferins,
0:45:35 > 0:45:40built out of simple elements like carbon, sulphur and nitrogen,
0:45:40 > 0:45:42react with oxygen to form oxyluciferin...
0:45:45 > 0:45:48..and that process releases energy as a blue light.
0:45:50 > 0:45:52An exquisite display.
0:46:02 > 0:46:05For Mr Urakami, this is the spectacle he lives for.
0:46:16 > 0:46:19It's a rare and beautiful sight in nature...
0:46:22 > 0:46:26..but the chemistry of oxidation is fundamental to all animals.
0:46:31 > 0:46:33There's a reason we breathe oxygen.
0:46:33 > 0:46:37It fuels the chemical reactions that power us.
0:46:41 > 0:46:44They release the energy to build and maintain
0:46:44 > 0:46:46the complex structure of our bodies.
0:46:50 > 0:46:54But it's the precise way life controls this flow of energy
0:46:54 > 0:46:58that's the difference between a volcano and a squid...
0:47:01 > 0:47:04..between raw chemistry and life...
0:47:06 > 0:47:08..between a moth and a flame.
0:47:08 > 0:47:11That one looks like an old man, that one there.
0:47:11 > 0:47:13That's nice!
0:47:13 > 0:47:16Moths and flames always seem to go together.
0:47:16 > 0:47:20In fact, in a basic chemical sense they are very similar,
0:47:20 > 0:47:23and candle wax is essentially food.
0:47:23 > 0:47:27It's a collection of long chain carbon molecules.
0:47:27 > 0:47:29And the candle, that food,
0:47:29 > 0:47:32reacts with oxygen to produce carbon dioxide, water
0:47:32 > 0:47:36and release energy, which is the flame.
0:47:36 > 0:47:39And inside the moth, exactly the same thing is happening.
0:47:39 > 0:47:44Food is reacting with oxygen to produce carbon dioxide and water
0:47:44 > 0:47:47and release energy. The energy that powers life.
0:47:47 > 0:47:50That's called respiration.
0:47:51 > 0:47:53It sounds quite simple.
0:47:53 > 0:47:57We burn our food to release the energy we need to live.
0:47:59 > 0:48:02What do moths eat in the winter?
0:48:04 > 0:48:07It's not that simple.
0:48:07 > 0:48:12But simple questions lead to the deepest answers.
0:48:12 > 0:48:15In this case, to the origin of life.
0:48:17 > 0:48:20The moth doesn't use the energy released from food directly.
0:48:20 > 0:48:23It does something way more complicated.
0:48:23 > 0:48:25It uses that energy to pump protons,
0:48:25 > 0:48:30the building blocks of atomic nuclei, across membranes.
0:48:30 > 0:48:32Billions of them. And so do you.
0:48:32 > 0:48:35And so does every living thing on the planet.
0:48:35 > 0:48:37In the time it's taken me to say the sentence,
0:48:37 > 0:48:40you have pumped more protons across membranes
0:48:40 > 0:48:43than there are stars in the observable universe.
0:48:43 > 0:48:47And then all those protons are allowed to cascade back
0:48:47 > 0:48:48down proton waterfalls,
0:48:48 > 0:48:52and little nanomachines with little water wheels stick in
0:48:52 > 0:48:56to that waterfall, and spin around and produce molecules called ATP,
0:48:56 > 0:48:58which are the universal batteries of life,
0:48:58 > 0:49:02which are then, finally, used to power your biology.
0:49:02 > 0:49:07It is incredibly complicated, and to be honest, a bit weird.
0:49:14 > 0:49:17This complicated and weird chemistry
0:49:17 > 0:49:21powers practically every living thing on Earth...
0:49:22 > 0:49:24..but it had to start somewhere...
0:49:25 > 0:49:28..and it may have begun before there was life.
0:49:37 > 0:49:42There is a place where this strange chemistry exists today,
0:49:42 > 0:49:44but not in a living thing.
0:49:47 > 0:49:49This may be the clue
0:49:49 > 0:49:52to how you get from the Earth
0:49:52 > 0:49:54to you and me.
0:50:00 > 0:50:03This fjord in Iceland is one of the few places on Earth
0:50:03 > 0:50:06where you can see how life could have emerged
0:50:06 > 0:50:08from a restless, young planet.
0:50:11 > 0:50:13My next-door neighbour was this old lady
0:50:13 > 0:50:17telling me stories about the things she saw from the sea.
0:50:20 > 0:50:24I have been diving there many times, so I knew this place.
0:50:26 > 0:50:28I didn't believe this old lady.
0:50:33 > 0:50:36Curiosity drove diver Erlendur Bogason
0:50:36 > 0:50:38to an extraordinary discovery.
0:50:42 > 0:50:45So I called my friend Artni, the fisherman,
0:50:45 > 0:50:48and asked him to take me to this place.
0:50:55 > 0:50:59Biologists knew of places where the chemistry of life
0:50:59 > 0:51:01emerges from the Earth,
0:51:01 > 0:51:05but they're all thousands of metres below the surface of the ocean.
0:51:06 > 0:51:11These two men stumbled on a place where you can literally touch it.
0:51:26 > 0:51:30I was, like, stressed because you're going alone
0:51:30 > 0:51:34somewhere to dive, and you don't know what you're going to find.
0:51:42 > 0:51:48And when I did see this huge white thing, it looked like a giant.
0:52:03 > 0:52:05It was unbelievable sight.
0:52:05 > 0:52:08Wow. It's beautiful. Something incredible.
0:52:15 > 0:52:19Erlendur had discovered a hydrothermal vent,
0:52:19 > 0:52:23but unlike those in the deep ocean, you can swim right up to this one.
0:52:24 > 0:52:27The vent is an outpouring of fresh water
0:52:27 > 0:52:30that's been heated by Iceland's geothermal energy.
0:52:32 > 0:52:36I took my glove off to put my arm into the hot water.
0:52:36 > 0:52:38It was like burning hot.
0:52:43 > 0:52:46By studying vents like these,
0:52:46 > 0:52:49scientists discovered that the chemistry of life exists
0:52:49 > 0:52:52in a nonliving thing,
0:52:52 > 0:52:53in the Earth.
0:53:01 > 0:53:05I called this scientist and told him about this.
0:53:05 > 0:53:10We went back for him to take water samples.
0:53:12 > 0:53:16To create a spark of life, all you need is a battery,
0:53:16 > 0:53:22with a flow of charged particles - in this case, protons.
0:53:30 > 0:53:32And to power the battery,
0:53:32 > 0:53:37you need nothing more than water from the vent and some sea water.
0:53:37 > 0:53:38Thank you.
0:53:41 > 0:53:46To show it works, you just need to connect it all to a voltmeter.
0:53:51 > 0:53:55And that is the spark of life.
0:54:00 > 0:54:02Why would I say that?
0:54:02 > 0:54:07Well, this water, taken from the vents, is alkaline
0:54:07 > 0:54:11and this sea water is relatively more acidic.
0:54:11 > 0:54:15That means that there is an excess of protons
0:54:15 > 0:54:19on this side of the battery than this side.
0:54:19 > 0:54:23And there's that waterfall, that cascade of protons,
0:54:23 > 0:54:27the same thing that's happening in the cells in your body,
0:54:27 > 0:54:29in the cells in the body of the seagulls
0:54:29 > 0:54:33and in fact the cells in the body of every living thing on the planet.
0:54:33 > 0:54:37Waterfalls of protons powering life.
0:54:37 > 0:54:40And that's the clue. That's the smoking gun.
0:54:40 > 0:54:44The theory is that the chemistry of life,
0:54:44 > 0:54:48the beginnings of the assembly of complex molecules,
0:54:48 > 0:54:51all the way up to the first living things to DNA
0:54:51 > 0:54:54and everything we think of as life today
0:54:54 > 0:54:58was built, was constructed, in conditions like this.
0:55:01 > 0:55:06The waterfall, the cascade of protons is the driver of complexity,
0:55:06 > 0:55:08the spark of life.
0:55:11 > 0:55:15It's the exquisite control of the proton waterfalls
0:55:15 > 0:55:18that separates life from chemistry...
0:55:20 > 0:55:22..the moth from a flame.
0:55:26 > 0:55:28So just spare a thought for what your body is doing now.
0:55:28 > 0:55:32I mean, that sandwich you just ate before watching this programme,
0:55:32 > 0:55:35you're burning that in oxygen, it's the oxygen that you breathe in.
0:55:35 > 0:55:39But you're not using the energy that gets released directly.
0:55:39 > 0:55:42You're using it to pump protons around.
0:55:42 > 0:55:46You pump them across little membranes, creating a voltage.
0:55:46 > 0:55:50About 30 million volts per metre in the cells in your body.
0:55:50 > 0:55:54That's the voltage of a lightning bolt.
0:55:54 > 0:55:56That's the spark of life
0:55:56 > 0:56:01and that's the clue that tells you that the origin of you,
0:56:01 > 0:56:06the most distant ancestor of you, wasn't a living thing at all,
0:56:06 > 0:56:07it was a geological thing.
0:56:07 > 0:56:12It was most likely to be a vent like the one we're floating over now,
0:56:12 > 0:56:15in some ocean, four billion years ago,
0:56:15 > 0:56:19the very earliest life of our planet.
0:56:22 > 0:56:25From a sandwich to a bolt of lightning,
0:56:25 > 0:56:28you are a remarkable machine.
0:56:36 > 0:56:39For me, this theory of the origin of life
0:56:39 > 0:56:42is the perfect example of the power of science.
0:56:45 > 0:56:49It's a grand, sweeping idea that comes from exploring in detail
0:56:49 > 0:56:53the way that living things control their energy.
0:56:56 > 0:56:58Look, it's slightly vibrating its wings.
0:57:00 > 0:57:02From asking questions like,
0:57:02 > 0:57:05what's the difference between a moth and a flame?
0:57:07 > 0:57:08He's going for a walk.
0:57:10 > 0:57:13But the answer is a wonderful story.
0:57:17 > 0:57:20At this instant, in the cells in your body,
0:57:20 > 0:57:22you're recreating the conditions that were present
0:57:22 > 0:57:25in the oceans of the primordial Earth.
0:57:25 > 0:57:28You are just chemistry.
0:57:28 > 0:57:30But what chemistry!
0:57:30 > 0:57:32The Earth is your ancestor.
0:57:33 > 0:57:37A restless planet is your creator.
0:57:46 > 0:57:48MUSIC: Fire by Etta James
0:57:48 > 0:57:50# Fire
0:57:50 > 0:57:52# Fire
0:57:52 > 0:57:54# Fire
0:57:54 > 0:57:56# I'm on fire
0:57:56 > 0:57:58# You make my body shiver, boy
0:57:58 > 0:57:59# You make my head go bad
0:57:59 > 0:58:01# You make my liver quiver, babe
0:58:01 > 0:58:03# You make my eyes get red
0:58:03 > 0:58:06# My knees get weak when I see you
0:58:06 > 0:58:08# Your love is much too strong
0:58:08 > 0:58:10# And when you take me in your arms
0:58:10 > 0:58:12# You know tomorrow is my home
0:58:12 > 0:58:15# Like I'm burning, yeah... #