Endless Forms Most Beautiful Wonders of Life


Endless Forms Most Beautiful

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In 2009, a new species of spider was identified.

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A spider with superpowers.

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It was named exactly 150 years

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after the publication of Darwin's On The Origin Of Species,

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in which he explained why life on Earth is so diverse and so complex.

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Darwin's theory of evolution by natural selection

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was built on the work of naturalists who were discovering

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thousands of new species across the world.

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That process of finding species new to science and naming them

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continues to this day.

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And it's recognised in the name of this newly discovered arachnid.

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Darwin's bark spider.

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The spider occupies a unique niche.

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It can hunt where no other spider can.

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That spider creates the largest webs found anywhere on Earth.

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In order to do that, it has to produce the strongest silk

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of any spider. They can span over 25 metres across lakes and rivers.

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And actually, no-one knows how they get their webs

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across such a large distance.

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But Darwin's bark spider

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is one of thousands of unique species of animals and plants

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that you find in Madagascar.

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The rainforests here are one of the most bio-diverse places

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on the planet.

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And each year, more discoveries are made

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as researchers try to understand why this tiny corner of the universe

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is so prolific.

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All of these living things were found within a five-minute walk

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of this field station. And the diversity is remarkable.

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There's a chameleon there. These are orchids.

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This big green leaf is a traveller's palm.

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There are four species of mushroom on that branch alone.

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Across Madagascar, there are over 14,000 species of plants,

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there are hundreds of species of mammals, birds and reptiles

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and over 90% of them are unique to this island.

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How could it be that so many diverse living things,

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so beautifully adapted to their environment, could've emerged

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from a universe that's governed by a simple set of natural laws?

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The fact that we know the answer to that question

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is one of the greatest achievements in science.

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In this film, I want to explore how these endless forms, most beautiful,

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have emerged from a lifeless cosmos.

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Africa. A whole continent full of creatures utterly different

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from those in Madagascar.

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But the diversity of life doesn't stop at what you see.

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Because within each individual lies another world of complexity.

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This, believe it or not, is the top predator in Africa.

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Or she will be when she's older.

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She's only about eight weeks old now.

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Her body is built from a host of different molecules

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and by far the most diverse group are known as proteins.

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We can see the proteins here.

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Those claws, so vital for a lion's survival,

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are made of a protein called keratin.

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Her eyes, also absolutely vital for her survival,

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have a protein called opsin which is bound to a pigment

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to make structures called rhodopsins which allow her to see in colour

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and also to allow her to see very well at night when she's hunting.

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There are also proteins in her muscles...

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..myosin and actin, which are the things that allow her to run away.

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The proteins in a lion come in countless different forms.

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But they all share something in common.

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A backbone of carbon.

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An atom that's able to form long, complex molecules.

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Of all the 92 elements, there really is only one

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which has that appetite for bonding its four electrons -

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to share them with other molecules.

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Carbon will share those electrons with nitrogen, oxygen, hydrogen,

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and critically, with other carbons,

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to build up these immensely complex chains,

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the amino acids and the proteins

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which are the building blocks of life.

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So to understand our planet's endless diversity,

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we must begin by considering this life-giving element.

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I've got a few scratches now because of you! Because of your proteins!

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After all, to build a lion, you must first build carbon.

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And that's a story that stretches back to a time

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long before there were even stars in the universe.

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13.5 billion years ago,

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just a few hundred million years after the Big Bang,

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the universe was a carbon-free zone.

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An infinite, sterile gloom of hydrogen and helium clouds.

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Until, one day,

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those vast clouds began to collapse under the force of gravity.

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Long before the solar system, Earth or life existed...

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..the first stars were born.

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The birth of the first stars

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did much more than illuminate the universe,

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because that set in train a sequence of events

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which is necessary for the existence of life in the universe.

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And we can still see that process playing out in the universe today.

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This is the brand-new South African Large Telescope.

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TECHNICIAN: Number three amps, gear right, gear box.

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Its mirror is 11 metres wide,

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making it the largest optical telescope

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in the southern hemisphere.

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And it recently helped to pin down what's happening in an object

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some 650 million light years from Earth.

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This beautiful, almost lifelike system is known simply as the Bird.

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It's the spectacular result

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of what we used to think was two galaxies colliding.

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It's events happening in the head of the Bird

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that are most interesting from a perspective of life in the universe.

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Because the head is formed by another galaxy,

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a third galaxy, an island of billions and billions of stars,

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colliding with two galaxies that form the wings and the body

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at a speed of around 250 miles a second.

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The turbulence, the disturbance,

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that that creates is causing many new stars to be formed.

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These stars begin their lives by burning hydrogen,

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to produce ever more helium.

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But as they age, as the hydrogen runs out, they turn to this helium.

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The temperature at their core rises

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increasing the chances of three helium nuclei

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fusing together to form a new element - carbon.

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That process has been going on

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for almost the entire history of the universe,

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back 13 billion years, and it's the formation of stars

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that is the vital first step in the formation of life,

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because stars produce the heavy elements in the universe

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including carbon.

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From the universe's earliest times,

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carbon has been created inside ageing stars.

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And over time, this carbon has built up,

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drifting through the cosmos as dust...

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..until some of it was caught up

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in the formation of a planet called Earth.

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And it's here that we can see this ancient carbon

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brought vividly to life.

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Today, the universe is old enough

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that countless stars have lived and died.

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So, there's been plenty of time to synthesise

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the primordial hydrogen and helium into the heavy elements.

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The question now is, how does that carbon get into the web of life?

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Well, today, it enters via one ingredient

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and I'm going to measure it using this balloon.

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The ingredient is carbon dioxide,

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which plays a key role in photosynthesis.

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Each night the carbon dioxide concentration increases,

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filling the air around the leaves at the top of the trees.

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This balloon has a carbon dioxide monitor in it

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which is going to measure the change in the levels of CO2

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at the top of the forest canopy as night turns to day.

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As the sun rises, the trees begin to photosynthesise.

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At 6pm last night, just after sunset,

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the concentration was around 350 parts per million.

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Around 10pm, around four hours after sunset,

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the concentration had risen to about 400 parts per million.

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Now, at about midday, the concentration's back down

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to about 345 parts per million.

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So that's a variation over a period of about 18 hours of 10%

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in the concentration of carbon dioxide,

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just in that piece of atmosphere at the top of the forest canopy.

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What you are seeing there is photosynthesis in action.

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Every day, across the planet,

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photosynthesis uses sunlight to turn carbon dioxide and water

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into simple sugars.

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The overwhelming majority of the carbon

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is locked up inside long chains of sugar molecules

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called cellulose and lignin.

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Lignin is the stuff that gives wood its strength.

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So, in this form, remember, that is most of it,

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it is very difficult indeed for animals to access.

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For the energy and nutrients locked away in these long carbon chains

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to move through the food web, they must be broken down.

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The best place to see that process in action is out on the open plain.

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It's one vast larder for all manner of organisms.

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By far the most effective harvester of carbon

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is actually one of the smallest creatures on the savanna.

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Termites are social insects, working together to form

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a characteristic sight, seen all over the bush.

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That's a termite mound. Actually, it's the tip of the iceberg.

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The termite city extends way beyond that underground.

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And its function is fascinating.

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It's essentially an air-conditioning system.

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What it does is maintain specific conditions inside the mound -

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the conditions of the rainforest.

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When the termites first colonised the savanna 30 million years ago,

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they brought the rainforest with them

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to support a form of life that was already wonderfully adapted

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to living off dead wood.

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This is what these termite mounds are all about.

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Can you see those structures, those white honeycomb-like structures?

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Those are called fungal combs.

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They're wood pulp and possibly bits of dead grass

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that the termites bring in and build into that structure.

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And the reason the conditions have to be the same as the rainforest

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is because they grow a particular genus of fungus called termitomyces

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around those honeycombs.

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The job of that fungus is to break down the lignin

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and cellulose inside the wood

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and convert it into a form that the termites can eat,

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which you can see there, the little white nodules,

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just present on the honeycomb structure.

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The termites lack the enzymes to break down the wood efficiently,

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so they have become farmers, tending to one giant social stomach.

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There's a very intense relationship between the termites and the fungus.

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You don't find that fungus anywhere else in the world

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as far as we know, other than inside termite mounds.

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It's thought that up to 90% of the carbon locked up in lignin

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in this part of Africa is released back into the food chain again,

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solely by those termites

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and that fungus.

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So the termites deal with most of the lignin,

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but that still leaves a vast store of carbon in the form of cellulose.

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Across Africa, herds of mammals graze on grasses and leaves,

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turning the cellulose into meat.

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Many are a type of mammal known as a ruminant...

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..the largest of which is one of the easiest animals to spot on safari.

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There's a giraffe there as well.

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Giraffes live off a diet similar to termites. They eat cellulose.

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Primarily the tops of the acacia trees

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that you see scattering the African savanna.

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And they face that same problem,

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they've got to break those difficult carbon bonds down

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and they've come up with a very similar solution

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which is to cultivate bacteria and fungi.

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But they do it inside their stomachs and ruminants like giraffes

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have had to build a very complex system in order to do that.

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They've got four stomachs,

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one of them contains their culture of bacteria and fungi,

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and they allow them to digest that difficult cellulose.

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Even with all this hardware,

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ruminants must feed for over two thirds of the day.

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But there are other creatures here that have found a short cut,

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after all, if plant fibres are hard to digest,

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why not let someone else do the work and simply steal a meal?

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It's coming for us.

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Oh, my God...

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ENGINE STARTS

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Look what we've just found.

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We were out looking for giraffe this morning,

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and we found about ten of them over there,

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but in looking for the giraffe, we've just found a leopard.

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This is one of the top predators out here.

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He's got very little to fear apart from other leopards and maybe lions.

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He's having a good look, he certainly doesn't care about us.

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He's around two years old and at the moment,

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he doesn't have his own territory, he's too young for that.

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So he's lying low.

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He'll have to make about two kills a week, to stay in good condition.

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So, maybe he'll catch an impala every three to four days,

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and he's obviously doing that.

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Because, look at him!

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-He's looking for protein.

-He likes your boom. >

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And I'm a little bit worried, cos I'm protein!

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-Oh, wow.

-He's after your boom, George. >

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He's coming really close to us

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because he's after the sound man's boom pole.

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Which is...oh!

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-That's incredible.

-RUMBLING MICROPHONE DISTORTION

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I just...

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-HE LAUGHS

-He's taken it...

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From its origin in the death of stars...

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..its capture by plants...

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..through insects, mammals and on.

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The carbon cycle is the real circle of life.

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Out there tonight, the relentless recycling of carbon

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through the food chain will continue.

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As night falls, you can almost sense it - the change in the sounds

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and the atmosphere.

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Some will die, so that others can live,

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as carbon leaps from branch to branch

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across the great tree of life.

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And guiding it along its way is just one very special form of chemistry.

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Every living thing is just a temporary home

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for carbon atoms that existed long before there was life on Earth

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and will exist long after Africa and Earth are gone.

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But, the pattern of life,

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the information needed to build a zebra, or a tree,

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or a human being or a lion persists.

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It's passed on from generation to generation, in a molecule.

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A helical molecule with a backbone of carbon called DNA.

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MUSIC: "Atmosphere" by Joy Division

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There was a time when Earth appeared empty.

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# Walk

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# In silence

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# Don't walk away

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# In silence... #

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Yet despite appearances, 3.8 billion years ago

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life was already under way, in the form of tiny living specks

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that probably all shared the same biochemistry.

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We know that every living thing on the planet today -

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so every piece of food you eat, every animal you've seen,

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everyone you've ever known or will know,

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in fact every living thing that WILL ever exist on this planet -

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was descended from that one speck.

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# Walk

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# In silence... #

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We call it the last universal common ancestor, or LUCA.

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So, just as the universe had its origin at the Big Bang,

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all life on this planet had its origin in that one moment.

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Less than a billion years after its formation,

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there was already life on Earth.

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It's possible that some of it used biochemistry

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utterly different from the life we see today.

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If so, it has long been extinct.

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It's also possible that the first life may not have been cellular -

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just living chemistry in the porous rocks of some ancient ocean.

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We're not sure, but what's certain is that one day,

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a population of organisms showed up with biochemistry that we WOULD recognise.

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This was LUCA.

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The first expression of a form of life that would in time

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throw up a group of humans who left their mark in this part of Africa.

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Now, we don't know what LUCA looked like,

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we don't know precisely where it lived or how it lived.

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But we do know this.

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If you start to trace my ancestral line back to my parents,

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to their parents, to their parents, to their parents,

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all the way back through geological timescales

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over hundreds of thousands of millions and billions of years,

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there will be an unbroken line from me all the way back to LUCA.

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We know that, because every living thing on the planet today

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shares the same biochemistry.

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We all have DNA. It's made of the same bases, A, C, T and G.

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They code for the same amino acids.

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Those amino acids build the same proteins, which do very

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similar jobs, whether you're a plant, a bacterium, or a bipedal hominid, like me.

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So all life uses the same fundamental biology...

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..those four bases, A, C, T and G,

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which code for just 20 amino acids,

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which in turn build each and every one of life's proteins.

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Be you bacteria, plant, bug or beast,

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your design comes from your DNA.

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So it's this molecule that must hold the key to understanding why life today is so diverse.

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We now know that the answer to the question,

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"Why is life on Earth so varied?" is actually the answer to

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the question, "Why is the DNA molecule itself so varied?"

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What are the natural processes that cause the structure of DNA to change?

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Well, part of the answer actually doesn't lie on Earth at all.

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It lies up there amongst the stars.

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And I can show you what I mean, using this,

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which is a cloud chamber, a piece of apparatus that has a unique place

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in the history of physics.

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I'm going to cool it down using dry ice, frozen carbon dioxide,

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just below -70 degrees Celsius.

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I'll put the top on.

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-HIGH-PITCHED SQUEAKING

-Hear that?

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That's the metal at the bottom of the tank cooling down very rapidly to -70.

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The cloud chamber works by having a super-saturated

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vapour of alcohol inside the chamber.

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Plenty on there...

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Now, I want to get that alcohol, I want to boil it off,

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to get the vapour into the chamber.

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So I'm going to put a hot water bottle on top.

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This is the first genuine particle physics detector.

0:30:540:30:58

It's the piece of apparatus that first saw antimatter.

0:30:580:31:02

And it really does consist only of a fish tank, some alcohol,

0:31:020:31:08

a bit of paper, and a hot water bottle.

0:31:080:31:10

There, look at that. Do you see that?

0:31:320:31:34

Cloud vapour trail.

0:31:340:31:37

That's a cosmic ray.

0:31:390:31:41

That was initiated by a particle, probably a proton,

0:31:410:31:46

that hit the Earth's atmosphere.

0:31:460:31:48

It almost certainly originated outside our solar system

0:31:520:31:56

and was accelerated by the magnetic fields of our galaxy.

0:31:560:31:59

It may even have begun its life BEYOND our galaxy.

0:31:590:32:04

Now, imagine if one of those hits the DNA of a living thing.

0:32:180:32:24

What that will do is cause a mutation.

0:32:240:32:27

That mutation may be detrimental, or,

0:32:270:32:31

very, very occasionally it might be beneficial.

0:32:310:32:34

And I think it's quite wonderful to imagine that maybe

0:32:380:32:44

one of the key mutations that was selected for over the millennia

0:32:440:32:48

that led to some trait in ME

0:32:480:32:51

was caused by some particle that began its life perhaps

0:32:510:32:55

in a massive supernova explosion, perhaps outside our galaxy

0:32:550:33:00

and went and hit the DNA of something

0:33:000:33:03

and caused some kind of beneficial mutation.

0:33:030:33:07

We don't know, but you can dream, can't you?

0:33:070:33:09

Mutations are an inevitable part of living on a planet like Earth.

0:33:170:33:21

They're the first hint at how DNA and the genes

0:33:240:33:28

that code for every living thing

0:33:280:33:30

change from generation to generation.

0:33:300:33:34

Mutations are the spring

0:33:500:33:52

from which innovation in the living world flows.

0:33:520:33:56

But cosmic rays are not the only way in which DNA can be altered.

0:33:590:34:05

There's natural background radiation from the rocks,

0:34:050:34:08

there's the action of chemicals and free radicals.

0:34:080:34:11

There can be errors when the code is copied.

0:34:110:34:15

And then all those changes can be shuffled by sex, and indeed

0:34:150:34:19

whole pieces of the code can be transferred from species to species.

0:34:190:34:24

So, bit by bit, in tiny steps from generation to generation,

0:34:240:34:29

the code is constantly randomly changing.

0:34:290:34:33

Now, whilst there's no doubt that random mutation does alter DNA,

0:34:360:34:41

evolution is anything but random. It can't be,

0:34:410:34:46

because the chances of something with DNA as complex as this

0:34:460:34:50

appearing by luck alone are vanishingly small.

0:34:500:34:53

Imagine you just changed one position in the code at random,

0:34:540:34:58

a random mutation.

0:34:580:35:00

There are four letters, A, T, C and G,

0:35:000:35:02

so there are four possible combinations.

0:35:020:35:05

If there are two places in the code,

0:35:050:35:07

there are four combinations for each one. So that makes 16.

0:35:070:35:12

If there are three, then there are 64 possibilities.

0:35:120:35:15

By the time you get to a code with 150 letters in it,

0:35:150:35:19

then there are more possible combinations in the code

0:35:190:35:23

than there are atoms in the observable universe.

0:35:230:35:26

Now, a hippo has a code

0:35:290:35:32

with around three billion different letters.

0:35:320:35:36

So the number of combinations of those letters, the chances of

0:35:360:35:41

producing that code at random, are absolutely, infinitesimally small.

0:35:410:35:47

It's impossible.

0:35:470:35:48

So there must be a non-random element to evolution...

0:35:530:35:57

..a natural process, which greatly restricts this

0:35:580:36:02

universe of possibilities, and shapes the outcome.

0:36:020:36:05

We call it natural selection.

0:36:060:36:09

And to see it in action, let's return to where we began

0:36:100:36:14

on the island of Madagascar.

0:36:140:36:16

Around 65 million years ago, a group of seafarers were nearing

0:36:460:36:49

the end of a long journey across the Indian Ocean.

0:36:490:36:53

These were accidental travellers, a group of creatures from Africa,

0:36:540:36:58

trapped on a natural raft and carried by the ocean currents.

0:36:580:37:03

The land they found was virgin green territory.

0:37:110:37:14

Plants, insects, reptiles and birds had established themselves,

0:37:160:37:21

but there were none of their own kind.

0:37:210:37:23

They were caught up in a saga that tells of the great

0:37:260:37:29

shifting of Earth's continental plates.

0:37:290:37:32

It's impossible to understand the diversity of life on Earth today

0:37:380:37:42

without understanding the shifting geography of our planet.

0:37:420:37:46

Here's a map of Earth's southern hemisphere as it was

0:37:460:37:50

150 million years ago, and you see

0:37:500:37:52

it's dominated by a single landmass called Gondwana.

0:37:520:37:56

And then, 90 million years ago,

0:37:560:37:59

Gondwana had begun to break up, to separate,

0:37:590:38:03

into something that looks quite recognisably like Africa,

0:38:030:38:07

and these two islands, Madagascar and India.

0:38:070:38:11

Now, subsequently India has drifted northwards

0:38:110:38:14

and bumped into Eurasia, raising the Himalayas.

0:38:140:38:17

But, crucially, Madagascar has remained isolated.

0:38:170:38:22

It's been an island surrounded by ocean for almost 90 million years.

0:38:220:38:27

So, when those seafarers arrived on their raft of trees and twigs and leaves,

0:38:350:38:41

they had a blank canvas - two, three,

0:38:410:38:45

maybe even a single pregnant individual

0:38:450:38:48

had a whole island to roam across.

0:38:480:38:52

And over 65 million years, they have blossomed into hundreds and

0:38:520:38:56

thousands of individuals, and become Madagascar's most iconic animals.

0:38:560:39:01

Finding the descendants of those ancient mariners is not easy.

0:39:430:39:47

But local guide Joseph has been tracking them for years.

0:39:480:39:51

And he's going to help me find them.

0:39:510:39:53

There at the top of the tree is an indri,

0:40:130:40:15

which is the largest lemur in Madagascar.

0:40:150:40:18

He's just sat there watching us quietly at the moment.

0:40:210:40:25

This lemur here is a very special lemur.

0:40:300:40:32

He has a name, he's called David.

0:40:320:40:35

After Sir David Attenborough.

0:40:370:40:40

LEMUR SCREECHES

0:40:480:40:51

LEMUR SCREECHES

0:40:570:40:59

Now, we can only do this because

0:41:090:41:11

Joseph has spent a lot of time with these lemurs.

0:41:110:41:15

So they trust him. And therefore, it seems, they trust me.

0:41:160:41:22

Its enormous hands!

0:41:350:41:38

The reason, it's thought, that we find lemurs here in Madagascar and Madagascar alone

0:41:400:41:46

is because there are no simians, there are no chimpanzees,

0:41:460:41:51

none of my ancestral family,

0:41:510:41:55

dating back tens of millions of years, to out-compete them.

0:41:550:41:58

So what's thought to have happened is that around 65 million years ago

0:41:580:42:04

one of the lemur's ancestors

0:42:040:42:09

managed to sail across the Mozambique Channel, and landed here.

0:42:090:42:14

There were none of those competitors here,

0:42:140:42:17

and so the lemurs have flourished ever since.

0:42:170:42:19

There are now over 90 species of lemur, or subspecies,

0:42:210:42:25

in Madagascar,

0:42:250:42:27

and no species of my lineage, the simians.

0:42:270:42:31

LEMUR SCREECHES

0:42:380:42:40

Over a vast sweep of time, the lemurs have diversified

0:42:450:42:50

to fill all manner of different habitats.

0:42:500:42:53

From the arid, spiny forests of the south...

0:42:550:42:58

..to the rocky canyons in the north,

0:42:590:43:02

there is something about this island

0:43:020:43:05

that is allowing the lemur's DNA to change in the most amazing ways.

0:43:050:43:10

We're on the hunt for an aye-aye,

0:43:290:43:32

the most closely related of all the surviving lemurs

0:43:320:43:35

to their common ancestor.

0:43:350:43:36

Oh, yes...

0:43:520:43:54

Oh, yeah.

0:43:560:43:58

Just shone the light up, and we saw these absolutely...

0:44:040:44:07

Two bright red eyes, shining out.

0:44:070:44:11

She's very high up at the moment.

0:44:110:44:14

Don't want to lose sight of her in this forest,

0:44:170:44:20

which is very dark and dense.

0:44:200:44:22

The team have located a female aye-aye, and her son.

0:44:250:44:28

They want to attach radio collars to track their movements,

0:44:300:44:33

and better understand how far they range through these forests.

0:44:330:44:37

But first, they must sedate them with a dart.

0:44:390:44:45

He's waiting for it to come down low enough to get that clean shot -

0:44:450:44:48

I mean, how you get a clean shot in this I have no idea.

0:44:480:44:54

After two hours of traipsing through the treacherous forest,

0:44:590:45:03

the aye-ayes remain at large.

0:45:030:45:06

INDISTINCT CHATTER

0:45:170:45:20

Well, here is the aye-aye that was tranquillised last night.

0:45:310:45:35

They finally got her about half an hour after we left.

0:45:350:45:38

I think it was probably because we were disturbing her.

0:45:380:45:40

Apparently as soon as we'd gone, she came down the tree

0:45:400:45:43

and she was tranquillised.

0:45:430:45:45

And as you can see she's pretty well sedated now,

0:45:450:45:48

which is fortunate for me

0:45:480:45:50

because she has certain adaptations that I wouldn't like to be deployed.

0:45:500:45:56

You can see there her teeth.

0:45:560:45:58

Her teeth are very unusual for a primate -

0:45:580:46:02

in fact, unique, because they carry on growing,

0:46:020:46:06

so she's much more like a rodent in that respect.

0:46:060:46:08

And that's so she can gnaw into wood.

0:46:080:46:11

You see, aye-ayes have filled a unique niche on Madagascar.

0:46:110:46:15

It's a niche that's filled by woodpeckers in many other areas of the world.

0:46:150:46:19

What she does is she feeds on grubs and bugs inside trees,

0:46:190:46:23

and to do that, she has several unique adaptations of which her teeth are one.

0:46:230:46:28

The most startling is this central finger here. It's bizarre.

0:46:290:46:35

It's got a ball and socket joint, for a start,

0:46:350:46:39

so it has complete 360-degree movement.

0:46:390:46:42

It feels to me almost as if it's broken, but it isn't,

0:46:420:46:45

it's just, you can move it around in any direction.

0:46:450:46:48

And she uses that finger initially to tap on the trunk of the tree,

0:46:480:46:53

and then, listening to the echo from that tapping, with these huge ears

0:46:530:46:58

she can detect where the grubs are.

0:46:580:47:01

And then, she gnaws through the wood with those rodent-like teeth,

0:47:010:47:05

and then uses this finger again to reach inside the hole

0:47:050:47:09

and get the bugs out.

0:47:090:47:11

So the question is, why?

0:47:110:47:14

How could an animal be so precisely adapted to a particular lifestyle?

0:47:140:47:22

She's waking up now!

0:47:220:47:24

And the answer is natural selection.

0:47:240:47:28

See, what must have happened is way back,

0:47:280:47:31

when the ancestors of the lemurs - the Lemuriformes -

0:47:310:47:34

arrived in Madagascar,

0:47:340:47:36

there must have been a mutation that

0:47:360:47:39

lengthened the middle finger ever so slightly of one of those lemurs.

0:47:390:47:43

And that must have given it an advantage.

0:47:430:47:46

That must have allowed it perhaps

0:47:460:47:48

to reach into little holes and search for grubs.

0:47:480:47:50

There's some reason why that lengthened middle finger

0:47:500:47:53

meant that that gene was more likely to be passed to the next generation

0:47:530:47:58

and then down to the next generation.

0:47:580:48:00

So that landscape of possibilities is narrowed,

0:48:000:48:04

it's narrowed because that gene persists.

0:48:040:48:07

And it's persisted now for at least 40 million years,

0:48:070:48:11

because this species has been on one branch of the tree of life now

0:48:110:48:16

for over 40 million years.

0:48:160:48:19

And so, over those years that middle finger

0:48:190:48:22

has got more and more specialised.

0:48:220:48:24

Natural selection has allowed the aye-aye's wonderfully mutated finger

0:48:250:48:30

to spread through the population.

0:48:300:48:32

And this same law applies to all life.

0:48:350:48:38

If you have a mutation that helps you in the struggle to survive,

0:48:400:48:43

you are more likely to leave more offspring.

0:48:430:48:47

And in the next generation, that mutation is more likely to survive.

0:48:470:48:52

So this animal is a beautiful example, probably one

0:48:560:49:00

of the best in the world, of how the sieve of natural selection produces

0:49:000:49:06

animals that are perfectly adapted to live in their environment.

0:49:060:49:11

Now, there are many reasons to study the aye-aye. But here's a good one.

0:49:340:49:39

In the 1970s, it was thought the aye-aye was extinct.

0:49:390:49:42

Now, we know there are several thousand in the forests of Madagascar -

0:49:420:49:46

5,000, 6,000, 7,000, certainly less than 10,000 -

0:49:460:49:50

but over the last 50 years, 50% of this forest has vanished.

0:49:500:49:54

This is an animal that's been around as a species for over 40 million years.

0:50:090:50:14

So it's important to know how these animals are doing,

0:50:140:50:18

and how they're surviving in this diminishing habitat.

0:50:180:50:22

Whilst natural selection explains why the aye-aye evolved,

0:50:380:50:42

it alone can't explain how a small group of individuals, over 60 million years ago,

0:50:420:50:49

gave rise to over 90 different species of lemur today.

0:50:490:50:53

But there is another form of life that can offer us a clue.

0:50:570:51:00

Up here in the high forest canopy, we're in a very different

0:51:030:51:07

environment to the one down there on the forest floor.

0:51:070:51:11

It's a more arid environment, it's almost like a desert.

0:51:110:51:15

It's exposed to the sun, water is harder to come by.

0:51:150:51:18

And so, this is a sea of different niches,

0:51:180:51:23

that are able to be occupied and exploited by animals

0:51:230:51:26

that are different to the ones you'll find down there on the floor.

0:51:260:51:30

So, in a very real sense, this is an island, an island to be colonised.

0:51:300:51:35

And sure enough, there are settlers to be found, even here.

0:51:370:51:41

You see that thing that looks like a muddy ball there, on the branch?

0:51:420:51:46

Well, that's an ants' nest,

0:51:460:51:49

it's home to a species of Crematogaster ants

0:51:490:51:51

that are unique not only to Madagascar,

0:51:510:51:55

but to the forest canopy.

0:51:550:51:57

You see, what makes those ants unique is that they can

0:51:570:52:00

build their own nests.

0:52:000:52:02

There are very few species of ants that can do that.

0:52:020:52:05

So that is an island, that is a niche,

0:52:050:52:09

and it's allowed that species of ant to develop

0:52:090:52:12

because they're isolated from the rest of the ecosystem.

0:52:120:52:16

And astonishingly, within this niche,

0:52:160:52:20

another form of life new to science has been discovered...

0:52:200:52:23

..a beetle that manages to survive here unharmed by the ants.

0:52:250:52:30

How it does it is a mystery.

0:52:310:52:35

But what IS known is that this particular species has only

0:52:350:52:39

ever been found inside these nests.

0:52:390:52:42

So, that really is its own mini-ecosystem,

0:52:430:52:48

with species living in it that are unique to that island.

0:52:480:52:51

We live on an ever-shifting, dynamic world

0:53:030:53:07

that creates islands in abundance.

0:53:070:53:10

Earth's mountain ranges, river valleys and canyons

0:53:190:53:23

all create islands for life.

0:53:230:53:26

And it's these islands

0:53:310:53:33

that those ancestors of the lemurs found when they arrived in Madagascar.

0:53:330:53:37

Empty niches, where populations became isolated,

0:53:440:53:48

and over great swathes of time

0:53:480:53:52

involved into such wonderfully diverse forms.

0:53:520:53:55

150 years on from the Origin Of Species, the subtlety

0:54:170:54:22

and beauty of Darwin's insight is still revealing itself to us.

0:54:220:54:26

It describes how our beautiful, complex tree of life

0:54:300:54:33

has grown from a once desolate universe.

0:54:330:54:37

The chemistry of carbon

0:54:390:54:41

allows for the existence of a molecule that is able to replicate

0:54:410:54:44

itself, and pass information on from generation to generation.

0:54:440:54:49

There can be random changes in the structure of that molecule -

0:54:490:54:53

mutations - and they are tested by their interaction with

0:54:530:54:57

the environment and with living things.

0:54:570:54:59

The ones that pass that test survive,

0:54:590:55:02

and the ones that fail that test are lost.

0:55:020:55:04

The separation and isolation of living things onto islands -

0:55:090:55:14

which may be physical, like Madagascar,

0:55:140:55:17

or just the single branch of a single tree -

0:55:170:55:20

results in speciation, the explosion of living forms

0:55:200:55:24

highly specialised to occupy niches within niches.

0:55:240:55:29

And this is the explanation for the diversity of life on Earth.

0:55:290:55:34

"There is grandeur in this view of life," as Darwin wrote,

0:55:340:55:38

and understanding how it happened surely only adds to the wonder.

0:55:380:55:43

As precise as Einstein's theories of relativity, and as profound

0:55:510:55:56

as thermodynamics,

0:55:560:55:59

Darwin has given us another universal law.

0:55:590:56:03

Evolution by natural selection.

0:56:060:56:09

And if evolution is the law on this island,

0:56:190:56:23

then it will apply throughout the cosmos.

0:56:230:56:26

Which begs a big question.

0:56:300:56:32

Could there be other "trees of life most beautiful" amongst the stars?

0:56:360:56:41

In 2011, we discovered a rocky planet

0:56:490:56:53

orbiting around a distant star,

0:56:530:56:55

with daytime temperatures not too dissimilar to those found on Earth.

0:56:550:57:00

Now, there must be millions

0:57:000:57:02

if not billions of such planets out there in the universe,

0:57:020:57:06

and it's inconceivable to me that none of them

0:57:060:57:10

will have trees of life as complex or even more complex than our own.

0:57:100:57:15

But that doesn't devalue the existence of OUR tree,

0:57:150:57:20

because our tree is unique.

0:57:200:57:22

It consists of thousands of branches,

0:57:220:57:24

all interdependent on thousands of others,

0:57:240:57:27

and the precise structure depends on chance events, like the passage

0:57:270:57:32

of the lemurs across the ocean 65 million years ago.

0:57:320:57:36

So when you go outside tomorrow,

0:57:440:57:46

just take a look at a little piece of your world.

0:57:460:57:49

A corner of your garden, or a park,

0:57:490:57:52

or even the grass that's growing in a crack in the pavement.

0:57:520:57:57

Because there will be life there, and it will be unique.

0:57:570:58:01

There will be nowhere like that anywhere else in the universe.

0:58:010:58:05

And that makes our tree, from the sturdiest branch to the most

0:58:050:58:09

fragile twig, indescribably valuable.

0:58:090:58:12

MUSIC: "Underneath the Stars" by Kate Rusby

0:58:140:58:18

# Underneath the stars you met me

0:58:180:58:23

# And underneath the stars you left me

0:58:230:58:29

# I wonder if the stars regret me

0:58:290:58:35

# I'm sure they'd like me if they only met me

0:58:350:58:40

# They come and go of their own free will

0:58:400:58:48

# Go gently... #

0:58:480:58:52

Subtitles by Red Bee Media Ltd

0:58:520:58:54

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