0:00:23 > 0:00:28In 2009, a new species of spider was identified.
0:00:32 > 0:00:35A spider with superpowers.
0:00:44 > 0:00:46It was named exactly 150 years
0:00:46 > 0:00:49after the publication of Darwin's On The Origin Of Species,
0:00:49 > 0:00:56in which he explained why life on Earth is so diverse and so complex.
0:01:02 > 0:01:05Darwin's theory of evolution by natural selection
0:01:05 > 0:01:09was built on the work of naturalists who were discovering
0:01:09 > 0:01:13thousands of new species across the world.
0:01:17 > 0:01:20That process of finding species new to science and naming them
0:01:20 > 0:01:22continues to this day.
0:01:22 > 0:01:25And it's recognised in the name of this newly discovered arachnid.
0:01:28 > 0:01:30Darwin's bark spider.
0:01:35 > 0:01:38The spider occupies a unique niche.
0:01:38 > 0:01:41It can hunt where no other spider can.
0:01:44 > 0:01:47That spider creates the largest webs found anywhere on Earth.
0:01:47 > 0:01:51In order to do that, it has to produce the strongest silk
0:01:51 > 0:01:56of any spider. They can span over 25 metres across lakes and rivers.
0:01:56 > 0:01:59And actually, no-one knows how they get their webs
0:01:59 > 0:02:01across such a large distance.
0:02:09 > 0:02:10But Darwin's bark spider
0:02:10 > 0:02:14is one of thousands of unique species of animals and plants
0:02:14 > 0:02:16that you find in Madagascar.
0:02:20 > 0:02:23The rainforests here are one of the most bio-diverse places
0:02:23 > 0:02:25on the planet.
0:02:31 > 0:02:33And each year, more discoveries are made
0:02:33 > 0:02:38as researchers try to understand why this tiny corner of the universe
0:02:38 > 0:02:41is so prolific.
0:02:41 > 0:02:44All of these living things were found within a five-minute walk
0:02:44 > 0:02:49of this field station. And the diversity is remarkable.
0:02:49 > 0:02:53There's a chameleon there. These are orchids.
0:02:53 > 0:02:55This big green leaf is a traveller's palm.
0:02:55 > 0:02:59There are four species of mushroom on that branch alone.
0:03:06 > 0:03:11Across Madagascar, there are over 14,000 species of plants,
0:03:11 > 0:03:15there are hundreds of species of mammals, birds and reptiles
0:03:15 > 0:03:19and over 90% of them are unique to this island.
0:03:31 > 0:03:35How could it be that so many diverse living things,
0:03:35 > 0:03:38so beautifully adapted to their environment, could've emerged
0:03:38 > 0:03:43from a universe that's governed by a simple set of natural laws?
0:03:49 > 0:03:51The fact that we know the answer to that question
0:03:51 > 0:03:55is one of the greatest achievements in science.
0:03:55 > 0:04:00In this film, I want to explore how these endless forms, most beautiful,
0:04:00 > 0:04:03have emerged from a lifeless cosmos.
0:04:51 > 0:04:56Africa. A whole continent full of creatures utterly different
0:04:56 > 0:04:58from those in Madagascar.
0:05:03 > 0:05:08But the diversity of life doesn't stop at what you see.
0:05:08 > 0:05:14Because within each individual lies another world of complexity.
0:05:41 > 0:05:45This, believe it or not, is the top predator in Africa.
0:05:45 > 0:05:47Or she will be when she's older.
0:05:47 > 0:05:50She's only about eight weeks old now.
0:05:52 > 0:05:55Her body is built from a host of different molecules
0:05:55 > 0:06:00and by far the most diverse group are known as proteins.
0:06:01 > 0:06:03We can see the proteins here.
0:06:03 > 0:06:08Those claws, so vital for a lion's survival,
0:06:08 > 0:06:10are made of a protein called keratin.
0:06:10 > 0:06:13Her eyes, also absolutely vital for her survival,
0:06:13 > 0:06:17have a protein called opsin which is bound to a pigment
0:06:17 > 0:06:21to make structures called rhodopsins which allow her to see in colour
0:06:21 > 0:06:25and also to allow her to see very well at night when she's hunting.
0:06:28 > 0:06:31There are also proteins in her muscles...
0:06:32 > 0:06:37..myosin and actin, which are the things that allow her to run away.
0:06:46 > 0:06:50The proteins in a lion come in countless different forms.
0:06:53 > 0:06:56But they all share something in common.
0:06:56 > 0:06:59A backbone of carbon.
0:07:01 > 0:07:05An atom that's able to form long, complex molecules.
0:07:09 > 0:07:13Of all the 92 elements, there really is only one
0:07:13 > 0:07:19which has that appetite for bonding its four electrons -
0:07:19 > 0:07:21to share them with other molecules.
0:07:21 > 0:07:27Carbon will share those electrons with nitrogen, oxygen, hydrogen,
0:07:27 > 0:07:29and critically, with other carbons,
0:07:29 > 0:07:32to build up these immensely complex chains,
0:07:32 > 0:07:34the amino acids and the proteins
0:07:34 > 0:07:37which are the building blocks of life.
0:07:39 > 0:07:41So to understand our planet's endless diversity,
0:07:41 > 0:07:46we must begin by considering this life-giving element.
0:07:47 > 0:07:51I've got a few scratches now because of you! Because of your proteins!
0:07:54 > 0:07:59After all, to build a lion, you must first build carbon.
0:07:59 > 0:08:02And that's a story that stretches back to a time
0:08:02 > 0:08:05long before there were even stars in the universe.
0:08:13 > 0:08:1513.5 billion years ago,
0:08:15 > 0:08:18just a few hundred million years after the Big Bang,
0:08:18 > 0:08:22the universe was a carbon-free zone.
0:08:24 > 0:08:29An infinite, sterile gloom of hydrogen and helium clouds.
0:08:31 > 0:08:33Until, one day,
0:08:33 > 0:08:36those vast clouds began to collapse under the force of gravity.
0:08:42 > 0:08:46Long before the solar system, Earth or life existed...
0:08:47 > 0:08:49..the first stars were born.
0:09:08 > 0:09:10The birth of the first stars
0:09:10 > 0:09:13did much more than illuminate the universe,
0:09:13 > 0:09:16because that set in train a sequence of events
0:09:16 > 0:09:20which is necessary for the existence of life in the universe.
0:09:28 > 0:09:31And we can still see that process playing out in the universe today.
0:09:37 > 0:09:41This is the brand-new South African Large Telescope.
0:09:41 > 0:09:44TECHNICIAN: Number three amps, gear right, gear box.
0:09:47 > 0:09:50Its mirror is 11 metres wide,
0:09:50 > 0:09:52making it the largest optical telescope
0:09:52 > 0:09:54in the southern hemisphere.
0:09:56 > 0:10:00And it recently helped to pin down what's happening in an object
0:10:00 > 0:10:02some 650 million light years from Earth.
0:10:09 > 0:10:16This beautiful, almost lifelike system is known simply as the Bird.
0:10:17 > 0:10:19It's the spectacular result
0:10:19 > 0:10:22of what we used to think was two galaxies colliding.
0:10:26 > 0:10:29It's events happening in the head of the Bird
0:10:29 > 0:10:32that are most interesting from a perspective of life in the universe.
0:10:32 > 0:10:36Because the head is formed by another galaxy,
0:10:36 > 0:10:40a third galaxy, an island of billions and billions of stars,
0:10:40 > 0:10:44colliding with two galaxies that form the wings and the body
0:10:44 > 0:10:48at a speed of around 250 miles a second.
0:10:48 > 0:10:51The turbulence, the disturbance,
0:10:51 > 0:10:55that that creates is causing many new stars to be formed.
0:11:01 > 0:11:05These stars begin their lives by burning hydrogen,
0:11:05 > 0:11:07to produce ever more helium.
0:11:09 > 0:11:14But as they age, as the hydrogen runs out, they turn to this helium.
0:11:16 > 0:11:19The temperature at their core rises
0:11:19 > 0:11:22increasing the chances of three helium nuclei
0:11:22 > 0:11:26fusing together to form a new element - carbon.
0:11:29 > 0:11:31That process has been going on
0:11:31 > 0:11:35for almost the entire history of the universe,
0:11:35 > 0:11:39back 13 billion years, and it's the formation of stars
0:11:39 > 0:11:43that is the vital first step in the formation of life,
0:11:43 > 0:11:47because stars produce the heavy elements in the universe
0:11:47 > 0:11:49including carbon.
0:11:56 > 0:11:59From the universe's earliest times,
0:11:59 > 0:12:03carbon has been created inside ageing stars.
0:12:08 > 0:12:11And over time, this carbon has built up,
0:12:11 > 0:12:14drifting through the cosmos as dust...
0:12:16 > 0:12:18..until some of it was caught up
0:12:18 > 0:12:21in the formation of a planet called Earth.
0:12:27 > 0:12:30And it's here that we can see this ancient carbon
0:12:30 > 0:12:32brought vividly to life.
0:12:47 > 0:12:50Today, the universe is old enough
0:12:50 > 0:12:52that countless stars have lived and died.
0:12:52 > 0:12:55So, there's been plenty of time to synthesise
0:12:55 > 0:12:59the primordial hydrogen and helium into the heavy elements.
0:13:01 > 0:13:07The question now is, how does that carbon get into the web of life?
0:13:07 > 0:13:11Well, today, it enters via one ingredient
0:13:11 > 0:13:15and I'm going to measure it using this balloon.
0:13:22 > 0:13:24The ingredient is carbon dioxide,
0:13:24 > 0:13:27which plays a key role in photosynthesis.
0:13:30 > 0:13:34Each night the carbon dioxide concentration increases,
0:13:34 > 0:13:38filling the air around the leaves at the top of the trees.
0:13:41 > 0:13:45This balloon has a carbon dioxide monitor in it
0:13:45 > 0:13:48which is going to measure the change in the levels of CO2
0:13:48 > 0:13:52at the top of the forest canopy as night turns to day.
0:13:59 > 0:14:04As the sun rises, the trees begin to photosynthesise.
0:14:06 > 0:14:09At 6pm last night, just after sunset,
0:14:09 > 0:14:13the concentration was around 350 parts per million.
0:14:14 > 0:14:17Around 10pm, around four hours after sunset,
0:14:17 > 0:14:22the concentration had risen to about 400 parts per million.
0:14:23 > 0:14:27Now, at about midday, the concentration's back down
0:14:27 > 0:14:31to about 345 parts per million.
0:14:31 > 0:14:36So that's a variation over a period of about 18 hours of 10%
0:14:36 > 0:14:40in the concentration of carbon dioxide,
0:14:40 > 0:14:43just in that piece of atmosphere at the top of the forest canopy.
0:14:43 > 0:14:47What you are seeing there is photosynthesis in action.
0:14:52 > 0:14:55Every day, across the planet,
0:14:55 > 0:15:00photosynthesis uses sunlight to turn carbon dioxide and water
0:15:00 > 0:15:02into simple sugars.
0:15:06 > 0:15:08The overwhelming majority of the carbon
0:15:08 > 0:15:12is locked up inside long chains of sugar molecules
0:15:12 > 0:15:15called cellulose and lignin.
0:15:19 > 0:15:24Lignin is the stuff that gives wood its strength.
0:15:24 > 0:15:27So, in this form, remember, that is most of it,
0:15:27 > 0:15:30it is very difficult indeed for animals to access.
0:15:35 > 0:15:39For the energy and nutrients locked away in these long carbon chains
0:15:39 > 0:15:43to move through the food web, they must be broken down.
0:15:48 > 0:15:53The best place to see that process in action is out on the open plain.
0:15:55 > 0:15:59It's one vast larder for all manner of organisms.
0:16:05 > 0:16:08By far the most effective harvester of carbon
0:16:08 > 0:16:13is actually one of the smallest creatures on the savanna.
0:16:18 > 0:16:21Termites are social insects, working together to form
0:16:21 > 0:16:25a characteristic sight, seen all over the bush.
0:16:25 > 0:16:29That's a termite mound. Actually, it's the tip of the iceberg.
0:16:29 > 0:16:34The termite city extends way beyond that underground.
0:16:34 > 0:16:37And its function is fascinating.
0:16:37 > 0:16:40It's essentially an air-conditioning system.
0:16:40 > 0:16:45What it does is maintain specific conditions inside the mound -
0:16:45 > 0:16:47the conditions of the rainforest.
0:16:49 > 0:16:54When the termites first colonised the savanna 30 million years ago,
0:16:54 > 0:16:57they brought the rainforest with them
0:16:57 > 0:17:01to support a form of life that was already wonderfully adapted
0:17:01 > 0:17:03to living off dead wood.
0:17:03 > 0:17:06This is what these termite mounds are all about.
0:17:06 > 0:17:11Can you see those structures, those white honeycomb-like structures?
0:17:11 > 0:17:14Those are called fungal combs.
0:17:14 > 0:17:17They're wood pulp and possibly bits of dead grass
0:17:17 > 0:17:21that the termites bring in and build into that structure.
0:17:21 > 0:17:24And the reason the conditions have to be the same as the rainforest
0:17:24 > 0:17:31is because they grow a particular genus of fungus called termitomyces
0:17:31 > 0:17:34around those honeycombs.
0:17:38 > 0:17:42The job of that fungus is to break down the lignin
0:17:42 > 0:17:43and cellulose inside the wood
0:17:43 > 0:17:46and convert it into a form that the termites can eat,
0:17:46 > 0:17:50which you can see there, the little white nodules,
0:17:50 > 0:17:54just present on the honeycomb structure.
0:17:57 > 0:18:02The termites lack the enzymes to break down the wood efficiently,
0:18:02 > 0:18:07so they have become farmers, tending to one giant social stomach.
0:18:09 > 0:18:14There's a very intense relationship between the termites and the fungus.
0:18:14 > 0:18:18You don't find that fungus anywhere else in the world
0:18:18 > 0:18:22as far as we know, other than inside termite mounds.
0:18:24 > 0:18:31It's thought that up to 90% of the carbon locked up in lignin
0:18:31 > 0:18:35in this part of Africa is released back into the food chain again,
0:18:35 > 0:18:38solely by those termites
0:18:38 > 0:18:39and that fungus.
0:19:01 > 0:19:04So the termites deal with most of the lignin,
0:19:04 > 0:19:09but that still leaves a vast store of carbon in the form of cellulose.
0:19:10 > 0:19:15Across Africa, herds of mammals graze on grasses and leaves,
0:19:15 > 0:19:18turning the cellulose into meat.
0:19:22 > 0:19:24Many are a type of mammal known as a ruminant...
0:19:25 > 0:19:30..the largest of which is one of the easiest animals to spot on safari.
0:19:30 > 0:19:32There's a giraffe there as well.
0:20:01 > 0:20:07Giraffes live off a diet similar to termites. They eat cellulose.
0:20:07 > 0:20:10Primarily the tops of the acacia trees
0:20:10 > 0:20:13that you see scattering the African savanna.
0:20:13 > 0:20:15And they face that same problem,
0:20:15 > 0:20:19they've got to break those difficult carbon bonds down
0:20:19 > 0:20:21and they've come up with a very similar solution
0:20:21 > 0:20:25which is to cultivate bacteria and fungi.
0:20:25 > 0:20:30But they do it inside their stomachs and ruminants like giraffes
0:20:30 > 0:20:34have had to build a very complex system in order to do that.
0:20:34 > 0:20:36They've got four stomachs,
0:20:36 > 0:20:39one of them contains their culture of bacteria and fungi,
0:20:39 > 0:20:44and they allow them to digest that difficult cellulose.
0:20:48 > 0:20:50Even with all this hardware,
0:20:50 > 0:20:54ruminants must feed for over two thirds of the day.
0:20:57 > 0:21:02But there are other creatures here that have found a short cut,
0:21:02 > 0:21:06after all, if plant fibres are hard to digest,
0:21:06 > 0:21:10why not let someone else do the work and simply steal a meal?
0:21:17 > 0:21:20It's coming for us.
0:21:20 > 0:21:21Oh, my God...
0:21:29 > 0:21:31ENGINE STARTS
0:21:34 > 0:21:37Look what we've just found.
0:21:37 > 0:21:39We were out looking for giraffe this morning,
0:21:39 > 0:21:42and we found about ten of them over there,
0:21:42 > 0:21:45but in looking for the giraffe, we've just found a leopard.
0:21:47 > 0:21:50This is one of the top predators out here.
0:21:50 > 0:21:54He's got very little to fear apart from other leopards and maybe lions.
0:21:54 > 0:21:58He's having a good look, he certainly doesn't care about us.
0:22:03 > 0:22:05He's around two years old and at the moment,
0:22:05 > 0:22:10he doesn't have his own territory, he's too young for that.
0:22:10 > 0:22:12So he's lying low.
0:22:17 > 0:22:22He'll have to make about two kills a week, to stay in good condition.
0:22:22 > 0:22:27So, maybe he'll catch an impala every three to four days,
0:22:27 > 0:22:29and he's obviously doing that.
0:22:32 > 0:22:34Because, look at him!
0:22:37 > 0:22:40- He's looking for protein. - He likes your boom. >
0:22:40 > 0:22:43And I'm a little bit worried, cos I'm protein!
0:22:45 > 0:22:47- Oh, wow. - He's after your boom, George. >
0:22:49 > 0:22:51He's coming really close to us
0:22:51 > 0:22:54because he's after the sound man's boom pole.
0:22:54 > 0:22:56Which is...oh!
0:22:56 > 0:22:59- That's incredible. - RUMBLING MICROPHONE DISTORTION
0:22:59 > 0:23:01I just...
0:23:01 > 0:23:03- HE LAUGHS - He's taken it...
0:23:19 > 0:23:23From its origin in the death of stars...
0:23:29 > 0:23:32..its capture by plants...
0:23:37 > 0:23:40..through insects, mammals and on.
0:23:48 > 0:23:52The carbon cycle is the real circle of life.
0:23:58 > 0:24:02Out there tonight, the relentless recycling of carbon
0:24:02 > 0:24:04through the food chain will continue.
0:24:06 > 0:24:10As night falls, you can almost sense it - the change in the sounds
0:24:10 > 0:24:12and the atmosphere.
0:24:15 > 0:24:19Some will die, so that others can live,
0:24:19 > 0:24:22as carbon leaps from branch to branch
0:24:22 > 0:24:24across the great tree of life.
0:24:26 > 0:24:32And guiding it along its way is just one very special form of chemistry.
0:24:32 > 0:24:35Every living thing is just a temporary home
0:24:35 > 0:24:39for carbon atoms that existed long before there was life on Earth
0:24:39 > 0:24:43and will exist long after Africa and Earth are gone.
0:24:49 > 0:24:51But, the pattern of life,
0:24:51 > 0:24:56the information needed to build a zebra, or a tree,
0:24:56 > 0:25:00or a human being or a lion persists.
0:25:00 > 0:25:04It's passed on from generation to generation, in a molecule.
0:25:04 > 0:25:09A helical molecule with a backbone of carbon called DNA.
0:25:29 > 0:25:31MUSIC: "Atmosphere" by Joy Division
0:25:35 > 0:25:39There was a time when Earth appeared empty.
0:25:39 > 0:25:43# Walk
0:25:43 > 0:25:46# In silence
0:25:46 > 0:25:51# Don't walk away
0:25:51 > 0:25:52# In silence... #
0:25:52 > 0:25:56Yet despite appearances, 3.8 billion years ago
0:25:56 > 0:26:01life was already under way, in the form of tiny living specks
0:26:01 > 0:26:04that probably all shared the same biochemistry.
0:26:05 > 0:26:08We know that every living thing on the planet today -
0:26:08 > 0:26:12so every piece of food you eat, every animal you've seen,
0:26:12 > 0:26:15everyone you've ever known or will know,
0:26:15 > 0:26:19in fact every living thing that WILL ever exist on this planet -
0:26:19 > 0:26:22was descended from that one speck.
0:26:23 > 0:26:27# Walk
0:26:27 > 0:26:31# In silence... #
0:26:31 > 0:26:35We call it the last universal common ancestor, or LUCA.
0:26:35 > 0:26:39So, just as the universe had its origin at the Big Bang,
0:26:39 > 0:26:44all life on this planet had its origin in that one moment.
0:26:49 > 0:26:52Less than a billion years after its formation,
0:26:52 > 0:26:54there was already life on Earth.
0:27:00 > 0:27:03It's possible that some of it used biochemistry
0:27:03 > 0:27:07utterly different from the life we see today.
0:27:07 > 0:27:10If so, it has long been extinct.
0:27:13 > 0:27:17It's also possible that the first life may not have been cellular -
0:27:17 > 0:27:22just living chemistry in the porous rocks of some ancient ocean.
0:27:22 > 0:27:27We're not sure, but what's certain is that one day,
0:27:27 > 0:27:32a population of organisms showed up with biochemistry that we WOULD recognise.
0:27:34 > 0:27:37This was LUCA.
0:27:37 > 0:27:41The first expression of a form of life that would in time
0:27:41 > 0:27:46throw up a group of humans who left their mark in this part of Africa.
0:27:50 > 0:27:53Now, we don't know what LUCA looked like,
0:27:53 > 0:27:57we don't know precisely where it lived or how it lived.
0:27:57 > 0:27:59But we do know this.
0:27:59 > 0:28:04If you start to trace my ancestral line back to my parents,
0:28:04 > 0:28:08to their parents, to their parents, to their parents,
0:28:08 > 0:28:11all the way back through geological timescales
0:28:11 > 0:28:15over hundreds of thousands of millions and billions of years,
0:28:15 > 0:28:21there will be an unbroken line from me all the way back to LUCA.
0:28:25 > 0:28:29We know that, because every living thing on the planet today
0:28:29 > 0:28:32shares the same biochemistry.
0:28:32 > 0:28:38We all have DNA. It's made of the same bases, A, C, T and G.
0:28:38 > 0:28:40They code for the same amino acids.
0:28:40 > 0:28:44Those amino acids build the same proteins, which do very
0:28:44 > 0:28:50similar jobs, whether you're a plant, a bacterium, or a bipedal hominid, like me.
0:28:55 > 0:28:59So all life uses the same fundamental biology...
0:29:01 > 0:29:04..those four bases, A, C, T and G,
0:29:04 > 0:29:07which code for just 20 amino acids,
0:29:07 > 0:29:12which in turn build each and every one of life's proteins.
0:29:16 > 0:29:20Be you bacteria, plant, bug or beast,
0:29:20 > 0:29:23your design comes from your DNA.
0:29:25 > 0:29:32So it's this molecule that must hold the key to understanding why life today is so diverse.
0:29:35 > 0:29:37We now know that the answer to the question,
0:29:37 > 0:29:41"Why is life on Earth so varied?" is actually the answer to
0:29:41 > 0:29:45the question, "Why is the DNA molecule itself so varied?"
0:29:45 > 0:29:51What are the natural processes that cause the structure of DNA to change?
0:29:51 > 0:29:55Well, part of the answer actually doesn't lie on Earth at all.
0:29:55 > 0:29:58It lies up there amongst the stars.
0:29:58 > 0:30:01And I can show you what I mean, using this,
0:30:01 > 0:30:07which is a cloud chamber, a piece of apparatus that has a unique place
0:30:07 > 0:30:10in the history of physics.
0:30:10 > 0:30:14I'm going to cool it down using dry ice, frozen carbon dioxide,
0:30:14 > 0:30:17just below -70 degrees Celsius.
0:30:23 > 0:30:25I'll put the top on.
0:30:25 > 0:30:27- HIGH-PITCHED SQUEAKING - Hear that?
0:30:28 > 0:30:34That's the metal at the bottom of the tank cooling down very rapidly to -70.
0:30:36 > 0:30:41The cloud chamber works by having a super-saturated
0:30:41 > 0:30:44vapour of alcohol inside the chamber.
0:30:44 > 0:30:46Plenty on there...
0:30:47 > 0:30:50Now, I want to get that alcohol, I want to boil it off,
0:30:50 > 0:30:52to get the vapour into the chamber.
0:30:52 > 0:30:54So I'm going to put a hot water bottle on top.
0:30:54 > 0:30:58This is the first genuine particle physics detector.
0:30:58 > 0:31:02It's the piece of apparatus that first saw antimatter.
0:31:02 > 0:31:08And it really does consist only of a fish tank, some alcohol,
0:31:08 > 0:31:10a bit of paper, and a hot water bottle.
0:31:32 > 0:31:34There, look at that. Do you see that?
0:31:34 > 0:31:37Cloud vapour trail.
0:31:39 > 0:31:41That's a cosmic ray.
0:31:41 > 0:31:46That was initiated by a particle, probably a proton,
0:31:46 > 0:31:48that hit the Earth's atmosphere.
0:31:52 > 0:31:56It almost certainly originated outside our solar system
0:31:56 > 0:31:59and was accelerated by the magnetic fields of our galaxy.
0:31:59 > 0:32:04It may even have begun its life BEYOND our galaxy.
0:32:18 > 0:32:24Now, imagine if one of those hits the DNA of a living thing.
0:32:24 > 0:32:27What that will do is cause a mutation.
0:32:27 > 0:32:31That mutation may be detrimental, or,
0:32:31 > 0:32:34very, very occasionally it might be beneficial.
0:32:38 > 0:32:44And I think it's quite wonderful to imagine that maybe
0:32:44 > 0:32:48one of the key mutations that was selected for over the millennia
0:32:48 > 0:32:51that led to some trait in ME
0:32:51 > 0:32:55was caused by some particle that began its life perhaps
0:32:55 > 0:33:00in a massive supernova explosion, perhaps outside our galaxy
0:33:00 > 0:33:03and went and hit the DNA of something
0:33:03 > 0:33:07and caused some kind of beneficial mutation.
0:33:07 > 0:33:09We don't know, but you can dream, can't you?
0:33:17 > 0:33:21Mutations are an inevitable part of living on a planet like Earth.
0:33:24 > 0:33:28They're the first hint at how DNA and the genes
0:33:28 > 0:33:30that code for every living thing
0:33:30 > 0:33:34change from generation to generation.
0:33:50 > 0:33:52Mutations are the spring
0:33:52 > 0:33:56from which innovation in the living world flows.
0:33:59 > 0:34:05But cosmic rays are not the only way in which DNA can be altered.
0:34:05 > 0:34:08There's natural background radiation from the rocks,
0:34:08 > 0:34:11there's the action of chemicals and free radicals.
0:34:11 > 0:34:15There can be errors when the code is copied.
0:34:15 > 0:34:19And then all those changes can be shuffled by sex, and indeed
0:34:19 > 0:34:24whole pieces of the code can be transferred from species to species.
0:34:24 > 0:34:29So, bit by bit, in tiny steps from generation to generation,
0:34:29 > 0:34:33the code is constantly randomly changing.
0:34:36 > 0:34:41Now, whilst there's no doubt that random mutation does alter DNA,
0:34:41 > 0:34:46evolution is anything but random. It can't be,
0:34:46 > 0:34:50because the chances of something with DNA as complex as this
0:34:50 > 0:34:53appearing by luck alone are vanishingly small.
0:34:54 > 0:34:58Imagine you just changed one position in the code at random,
0:34:58 > 0:35:00a random mutation.
0:35:00 > 0:35:02There are four letters, A, T, C and G,
0:35:02 > 0:35:05so there are four possible combinations.
0:35:05 > 0:35:07If there are two places in the code,
0:35:07 > 0:35:12there are four combinations for each one. So that makes 16.
0:35:12 > 0:35:15If there are three, then there are 64 possibilities.
0:35:15 > 0:35:19By the time you get to a code with 150 letters in it,
0:35:19 > 0:35:23then there are more possible combinations in the code
0:35:23 > 0:35:26than there are atoms in the observable universe.
0:35:29 > 0:35:32Now, a hippo has a code
0:35:32 > 0:35:36with around three billion different letters.
0:35:36 > 0:35:41So the number of combinations of those letters, the chances of
0:35:41 > 0:35:47producing that code at random, are absolutely, infinitesimally small.
0:35:47 > 0:35:48It's impossible.
0:35:53 > 0:35:57So there must be a non-random element to evolution...
0:35:58 > 0:36:02..a natural process, which greatly restricts this
0:36:02 > 0:36:05universe of possibilities, and shapes the outcome.
0:36:06 > 0:36:09We call it natural selection.
0:36:10 > 0:36:14And to see it in action, let's return to where we began
0:36:14 > 0:36:16on the island of Madagascar.
0:36:46 > 0:36:49Around 65 million years ago, a group of seafarers were nearing
0:36:49 > 0:36:53the end of a long journey across the Indian Ocean.
0:36:54 > 0:36:58These were accidental travellers, a group of creatures from Africa,
0:36:58 > 0:37:03trapped on a natural raft and carried by the ocean currents.
0:37:11 > 0:37:14The land they found was virgin green territory.
0:37:16 > 0:37:21Plants, insects, reptiles and birds had established themselves,
0:37:21 > 0:37:23but there were none of their own kind.
0:37:26 > 0:37:29They were caught up in a saga that tells of the great
0:37:29 > 0:37:32shifting of Earth's continental plates.
0:37:38 > 0:37:42It's impossible to understand the diversity of life on Earth today
0:37:42 > 0:37:46without understanding the shifting geography of our planet.
0:37:46 > 0:37:50Here's a map of Earth's southern hemisphere as it was
0:37:50 > 0:37:52150 million years ago, and you see
0:37:52 > 0:37:56it's dominated by a single landmass called Gondwana.
0:37:56 > 0:37:59And then, 90 million years ago,
0:37:59 > 0:38:03Gondwana had begun to break up, to separate,
0:38:03 > 0:38:07into something that looks quite recognisably like Africa,
0:38:07 > 0:38:11and these two islands, Madagascar and India.
0:38:11 > 0:38:14Now, subsequently India has drifted northwards
0:38:14 > 0:38:17and bumped into Eurasia, raising the Himalayas.
0:38:17 > 0:38:22But, crucially, Madagascar has remained isolated.
0:38:22 > 0:38:27It's been an island surrounded by ocean for almost 90 million years.
0:38:35 > 0:38:41So, when those seafarers arrived on their raft of trees and twigs and leaves,
0:38:41 > 0:38:45they had a blank canvas - two, three,
0:38:45 > 0:38:48maybe even a single pregnant individual
0:38:48 > 0:38:52had a whole island to roam across.
0:38:52 > 0:38:56And over 65 million years, they have blossomed into hundreds and
0:38:56 > 0:39:01thousands of individuals, and become Madagascar's most iconic animals.
0:39:43 > 0:39:47Finding the descendants of those ancient mariners is not easy.
0:39:48 > 0:39:51But local guide Joseph has been tracking them for years.
0:39:51 > 0:39:53And he's going to help me find them.
0:40:13 > 0:40:15There at the top of the tree is an indri,
0:40:15 > 0:40:18which is the largest lemur in Madagascar.
0:40:21 > 0:40:25He's just sat there watching us quietly at the moment.
0:40:30 > 0:40:32This lemur here is a very special lemur.
0:40:32 > 0:40:35He has a name, he's called David.
0:40:37 > 0:40:40After Sir David Attenborough.
0:40:48 > 0:40:51LEMUR SCREECHES
0:40:57 > 0:40:59LEMUR SCREECHES
0:41:09 > 0:41:11Now, we can only do this because
0:41:11 > 0:41:15Joseph has spent a lot of time with these lemurs.
0:41:16 > 0:41:22So they trust him. And therefore, it seems, they trust me.
0:41:35 > 0:41:38Its enormous hands!
0:41:40 > 0:41:46The reason, it's thought, that we find lemurs here in Madagascar and Madagascar alone
0:41:46 > 0:41:51is because there are no simians, there are no chimpanzees,
0:41:51 > 0:41:55none of my ancestral family,
0:41:55 > 0:41:58dating back tens of millions of years, to out-compete them.
0:41:58 > 0:42:04So what's thought to have happened is that around 65 million years ago
0:42:04 > 0:42:09one of the lemur's ancestors
0:42:09 > 0:42:14managed to sail across the Mozambique Channel, and landed here.
0:42:14 > 0:42:17There were none of those competitors here,
0:42:17 > 0:42:19and so the lemurs have flourished ever since.
0:42:21 > 0:42:25There are now over 90 species of lemur, or subspecies,
0:42:25 > 0:42:27in Madagascar,
0:42:27 > 0:42:31and no species of my lineage, the simians.
0:42:38 > 0:42:40LEMUR SCREECHES
0:42:45 > 0:42:50Over a vast sweep of time, the lemurs have diversified
0:42:50 > 0:42:53to fill all manner of different habitats.
0:42:55 > 0:42:58From the arid, spiny forests of the south...
0:42:59 > 0:43:02..to the rocky canyons in the north,
0:43:02 > 0:43:05there is something about this island
0:43:05 > 0:43:10that is allowing the lemur's DNA to change in the most amazing ways.
0:43:29 > 0:43:32We're on the hunt for an aye-aye,
0:43:32 > 0:43:35the most closely related of all the surviving lemurs
0:43:35 > 0:43:36to their common ancestor.
0:43:52 > 0:43:54Oh, yes...
0:43:56 > 0:43:58Oh, yeah.
0:44:04 > 0:44:07Just shone the light up, and we saw these absolutely...
0:44:07 > 0:44:11Two bright red eyes, shining out.
0:44:11 > 0:44:14She's very high up at the moment.
0:44:17 > 0:44:20Don't want to lose sight of her in this forest,
0:44:20 > 0:44:22which is very dark and dense.
0:44:25 > 0:44:28The team have located a female aye-aye, and her son.
0:44:30 > 0:44:33They want to attach radio collars to track their movements,
0:44:33 > 0:44:37and better understand how far they range through these forests.
0:44:39 > 0:44:45But first, they must sedate them with a dart.
0:44:45 > 0:44:48He's waiting for it to come down low enough to get that clean shot -
0:44:48 > 0:44:54I mean, how you get a clean shot in this I have no idea.
0:44:59 > 0:45:03After two hours of traipsing through the treacherous forest,
0:45:03 > 0:45:06the aye-ayes remain at large.
0:45:17 > 0:45:20INDISTINCT CHATTER
0:45:31 > 0:45:35Well, here is the aye-aye that was tranquillised last night.
0:45:35 > 0:45:38They finally got her about half an hour after we left.
0:45:38 > 0:45:40I think it was probably because we were disturbing her.
0:45:40 > 0:45:43Apparently as soon as we'd gone, she came down the tree
0:45:43 > 0:45:45and she was tranquillised.
0:45:45 > 0:45:48And as you can see she's pretty well sedated now,
0:45:48 > 0:45:50which is fortunate for me
0:45:50 > 0:45:56because she has certain adaptations that I wouldn't like to be deployed.
0:45:56 > 0:45:58You can see there her teeth.
0:45:58 > 0:46:02Her teeth are very unusual for a primate -
0:46:02 > 0:46:06in fact, unique, because they carry on growing,
0:46:06 > 0:46:08so she's much more like a rodent in that respect.
0:46:08 > 0:46:11And that's so she can gnaw into wood.
0:46:11 > 0:46:15You see, aye-ayes have filled a unique niche on Madagascar.
0:46:15 > 0:46:19It's a niche that's filled by woodpeckers in many other areas of the world.
0:46:19 > 0:46:23What she does is she feeds on grubs and bugs inside trees,
0:46:23 > 0:46:28and to do that, she has several unique adaptations of which her teeth are one.
0:46:29 > 0:46:35The most startling is this central finger here. It's bizarre.
0:46:35 > 0:46:39It's got a ball and socket joint, for a start,
0:46:39 > 0:46:42so it has complete 360-degree movement.
0:46:42 > 0:46:45It feels to me almost as if it's broken, but it isn't,
0:46:45 > 0:46:48it's just, you can move it around in any direction.
0:46:48 > 0:46:53And she uses that finger initially to tap on the trunk of the tree,
0:46:53 > 0:46:58and then, listening to the echo from that tapping, with these huge ears
0:46:58 > 0:47:01she can detect where the grubs are.
0:47:01 > 0:47:05And then, she gnaws through the wood with those rodent-like teeth,
0:47:05 > 0:47:09and then uses this finger again to reach inside the hole
0:47:09 > 0:47:11and get the bugs out.
0:47:11 > 0:47:14So the question is, why?
0:47:14 > 0:47:22How could an animal be so precisely adapted to a particular lifestyle?
0:47:22 > 0:47:24She's waking up now!
0:47:24 > 0:47:28And the answer is natural selection.
0:47:28 > 0:47:31See, what must have happened is way back,
0:47:31 > 0:47:34when the ancestors of the lemurs - the Lemuriformes -
0:47:34 > 0:47:36arrived in Madagascar,
0:47:36 > 0:47:39there must have been a mutation that
0:47:39 > 0:47:43lengthened the middle finger ever so slightly of one of those lemurs.
0:47:43 > 0:47:46And that must have given it an advantage.
0:47:46 > 0:47:48That must have allowed it perhaps
0:47:48 > 0:47:50to reach into little holes and search for grubs.
0:47:50 > 0:47:53There's some reason why that lengthened middle finger
0:47:53 > 0:47:58meant that that gene was more likely to be passed to the next generation
0:47:58 > 0:48:00and then down to the next generation.
0:48:00 > 0:48:04So that landscape of possibilities is narrowed,
0:48:04 > 0:48:07it's narrowed because that gene persists.
0:48:07 > 0:48:11And it's persisted now for at least 40 million years,
0:48:11 > 0:48:16because this species has been on one branch of the tree of life now
0:48:16 > 0:48:19for over 40 million years.
0:48:19 > 0:48:22And so, over those years that middle finger
0:48:22 > 0:48:24has got more and more specialised.
0:48:25 > 0:48:30Natural selection has allowed the aye-aye's wonderfully mutated finger
0:48:30 > 0:48:32to spread through the population.
0:48:35 > 0:48:38And this same law applies to all life.
0:48:40 > 0:48:43If you have a mutation that helps you in the struggle to survive,
0:48:43 > 0:48:47you are more likely to leave more offspring.
0:48:47 > 0:48:52And in the next generation, that mutation is more likely to survive.
0:48:56 > 0:49:00So this animal is a beautiful example, probably one
0:49:00 > 0:49:06of the best in the world, of how the sieve of natural selection produces
0:49:06 > 0:49:11animals that are perfectly adapted to live in their environment.
0:49:34 > 0:49:39Now, there are many reasons to study the aye-aye. But here's a good one.
0:49:39 > 0:49:42In the 1970s, it was thought the aye-aye was extinct.
0:49:42 > 0:49:46Now, we know there are several thousand in the forests of Madagascar -
0:49:46 > 0:49:505,000, 6,000, 7,000, certainly less than 10,000 -
0:49:50 > 0:49:54but over the last 50 years, 50% of this forest has vanished.
0:50:09 > 0:50:14This is an animal that's been around as a species for over 40 million years.
0:50:14 > 0:50:18So it's important to know how these animals are doing,
0:50:18 > 0:50:22and how they're surviving in this diminishing habitat.
0:50:38 > 0:50:42Whilst natural selection explains why the aye-aye evolved,
0:50:42 > 0:50:49it alone can't explain how a small group of individuals, over 60 million years ago,
0:50:49 > 0:50:53gave rise to over 90 different species of lemur today.
0:50:57 > 0:51:00But there is another form of life that can offer us a clue.
0:51:03 > 0:51:07Up here in the high forest canopy, we're in a very different
0:51:07 > 0:51:11environment to the one down there on the forest floor.
0:51:11 > 0:51:15It's a more arid environment, it's almost like a desert.
0:51:15 > 0:51:18It's exposed to the sun, water is harder to come by.
0:51:18 > 0:51:23And so, this is a sea of different niches,
0:51:23 > 0:51:26that are able to be occupied and exploited by animals
0:51:26 > 0:51:30that are different to the ones you'll find down there on the floor.
0:51:30 > 0:51:35So, in a very real sense, this is an island, an island to be colonised.
0:51:37 > 0:51:41And sure enough, there are settlers to be found, even here.
0:51:42 > 0:51:46You see that thing that looks like a muddy ball there, on the branch?
0:51:46 > 0:51:49Well, that's an ants' nest,
0:51:49 > 0:51:51it's home to a species of Crematogaster ants
0:51:51 > 0:51:55that are unique not only to Madagascar,
0:51:55 > 0:51:57but to the forest canopy.
0:51:57 > 0:52:00You see, what makes those ants unique is that they can
0:52:00 > 0:52:02build their own nests.
0:52:02 > 0:52:05There are very few species of ants that can do that.
0:52:05 > 0:52:09So that is an island, that is a niche,
0:52:09 > 0:52:12and it's allowed that species of ant to develop
0:52:12 > 0:52:16because they're isolated from the rest of the ecosystem.
0:52:16 > 0:52:20And astonishingly, within this niche,
0:52:20 > 0:52:23another form of life new to science has been discovered...
0:52:25 > 0:52:30..a beetle that manages to survive here unharmed by the ants.
0:52:31 > 0:52:35How it does it is a mystery.
0:52:35 > 0:52:39But what IS known is that this particular species has only
0:52:39 > 0:52:42ever been found inside these nests.
0:52:43 > 0:52:48So, that really is its own mini-ecosystem,
0:52:48 > 0:52:51with species living in it that are unique to that island.
0:53:03 > 0:53:07We live on an ever-shifting, dynamic world
0:53:07 > 0:53:10that creates islands in abundance.
0:53:19 > 0:53:23Earth's mountain ranges, river valleys and canyons
0:53:23 > 0:53:26all create islands for life.
0:53:31 > 0:53:33And it's these islands
0:53:33 > 0:53:37that those ancestors of the lemurs found when they arrived in Madagascar.
0:53:44 > 0:53:48Empty niches, where populations became isolated,
0:53:48 > 0:53:52and over great swathes of time
0:53:52 > 0:53:55involved into such wonderfully diverse forms.
0:54:17 > 0:54:22150 years on from the Origin Of Species, the subtlety
0:54:22 > 0:54:26and beauty of Darwin's insight is still revealing itself to us.
0:54:30 > 0:54:33It describes how our beautiful, complex tree of life
0:54:33 > 0:54:37has grown from a once desolate universe.
0:54:39 > 0:54:41The chemistry of carbon
0:54:41 > 0:54:44allows for the existence of a molecule that is able to replicate
0:54:44 > 0:54:49itself, and pass information on from generation to generation.
0:54:49 > 0:54:53There can be random changes in the structure of that molecule -
0:54:53 > 0:54:57mutations - and they are tested by their interaction with
0:54:57 > 0:54:59the environment and with living things.
0:54:59 > 0:55:02The ones that pass that test survive,
0:55:02 > 0:55:04and the ones that fail that test are lost.
0:55:09 > 0:55:14The separation and isolation of living things onto islands -
0:55:14 > 0:55:17which may be physical, like Madagascar,
0:55:17 > 0:55:20or just the single branch of a single tree -
0:55:20 > 0:55:24results in speciation, the explosion of living forms
0:55:24 > 0:55:29highly specialised to occupy niches within niches.
0:55:29 > 0:55:34And this is the explanation for the diversity of life on Earth.
0:55:34 > 0:55:38"There is grandeur in this view of life," as Darwin wrote,
0:55:38 > 0:55:43and understanding how it happened surely only adds to the wonder.
0:55:51 > 0:55:56As precise as Einstein's theories of relativity, and as profound
0:55:56 > 0:55:59as thermodynamics,
0:55:59 > 0:56:03Darwin has given us another universal law.
0:56:06 > 0:56:09Evolution by natural selection.
0:56:19 > 0:56:23And if evolution is the law on this island,
0:56:23 > 0:56:26then it will apply throughout the cosmos.
0:56:30 > 0:56:32Which begs a big question.
0:56:36 > 0:56:41Could there be other "trees of life most beautiful" amongst the stars?
0:56:49 > 0:56:53In 2011, we discovered a rocky planet
0:56:53 > 0:56:55orbiting around a distant star,
0:56:55 > 0:57:00with daytime temperatures not too dissimilar to those found on Earth.
0:57:00 > 0:57:02Now, there must be millions
0:57:02 > 0:57:06if not billions of such planets out there in the universe,
0:57:06 > 0:57:10and it's inconceivable to me that none of them
0:57:10 > 0:57:15will have trees of life as complex or even more complex than our own.
0:57:15 > 0:57:20But that doesn't devalue the existence of OUR tree,
0:57:20 > 0:57:22because our tree is unique.
0:57:22 > 0:57:24It consists of thousands of branches,
0:57:24 > 0:57:27all interdependent on thousands of others,
0:57:27 > 0:57:32and the precise structure depends on chance events, like the passage
0:57:32 > 0:57:36of the lemurs across the ocean 65 million years ago.
0:57:44 > 0:57:46So when you go outside tomorrow,
0:57:46 > 0:57:49just take a look at a little piece of your world.
0:57:49 > 0:57:52A corner of your garden, or a park,
0:57:52 > 0:57:57or even the grass that's growing in a crack in the pavement.
0:57:57 > 0:58:01Because there will be life there, and it will be unique.
0:58:01 > 0:58:05There will be nowhere like that anywhere else in the universe.
0:58:05 > 0:58:09And that makes our tree, from the sturdiest branch to the most
0:58:09 > 0:58:12fragile twig, indescribably valuable.
0:58:14 > 0:58:18MUSIC: "Underneath the Stars" by Kate Rusby
0:58:18 > 0:58:23# Underneath the stars you met me
0:58:23 > 0:58:29# And underneath the stars you left me
0:58:29 > 0:58:35# I wonder if the stars regret me
0:58:35 > 0:58:40# I'm sure they'd like me if they only met me
0:58:40 > 0:58:48# They come and go of their own free will
0:58:48 > 0:58:52# Go gently... #
0:58:52 > 0:58:54Subtitles by Red Bee Media Ltd