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I'm on a fantastic journey to look for the origins of life.
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I shall be travelling not only around the world, but back in time,
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to try and build a picture
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of what life was like in that very early period.
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It will be a journey full of wonders.
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Parts of it were unknown until only a few years ago.
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In 50 years of programme-making, I've been lucky enough to explore
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the living world in all its splendour and complexity.
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The blue whale! The biggest creature that exists on the planet!
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Now, I'm off to explore the origins of all this.
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To look for the very first living creatures that appeared on the planet.
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In recent years, scientists have unearthed dramatic evidence of what those first creatures were like.
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We can also find clues in living animals.
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And this enchanting little creature
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is what we were looking for.
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Using the latest technology, it's possible to bring those first animals to life
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for the first time in half a billion years.
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From the moment they appeared
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to the time that they took their pioneering steps on land,
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we can deduce how animals acquired bodies that move,
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eyes that saw and mouths that ate.
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And we can understand how those first organisms
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laid the foundations for modern animals as we know them today.
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Hello, old boy. How are you?
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'Including you and me.'
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My 40,000 mile journey begins very close to home, in Britain.
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This is the Charnwood Forest in Leicestershire in the middle of England.
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As a schoolboy, I grew up near here.
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And in these rocks, a discovery was made
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that transformed our understanding
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of that mystery of mysteries, the origin of life.
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The history of life can be thought of as a many-branched tree,
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with all the species alive today
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related to common ancestors down near the base.
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The five kingdoms of life, the main branches, were established early on.
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Bacteria.
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Protists - amoeba-like creatures.
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Fungi.
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Plants.
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And animals. That for me is the most fascinating question of all.
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How and when did they first appear?
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The answers are only now beginning to emerge -
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and some of the first clues came from here in Charnwood Forest.
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I was a passionate fossil collector.
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But I never came to look for them in this part of Charnwood,
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because the rocks here are among the most ancient in the world.
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Around 600 million years old, in fact.
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And every geologist knew or at least was convinced that rocks of
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such extreme age couldn't possibly contain fossils of any kind.
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And then a boy from my very own school, just a few years after I left it,
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made an astounding discovery.
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Against all the predictions of scientific know-alls,
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he found a fossil in these ancient Leicestershire rocks.
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And this is it.
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It's called and is known around the world as Charnia,
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after the forest in which it was discovered.
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But what is it?
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Is it animal or plant?
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The fact is it comes from such a remote period
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that the distinction between those two forms of life was not yet clear.
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But one thing is certain.
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It clearly was alive.
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Charnia was a marine organism, part of an ancient community
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of living things that lived in darkness at the bottom of an ocean.
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That much we do know.
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But what was this strange creature?
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When did it first appear?
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And how is it related to modern animals?
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The answers to these questions are only now beginning to emerge.
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There were further finds in Charnwood forest, like this disk,
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which was probably the holdfast
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which secured the frond of Charnia to the sea floor.
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And then people began to look in rocks of this great age
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all around the world.
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And lo and behold they discovered a whole range of fossils
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that enable us now to put together in extraordinary detail
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the first chapters in the history of life.
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That all happened a very long time ago.
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Imagine travelling back through time.
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Humans have been around for two million years.
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The dinosaurs were wiped out 65 million years ago.
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Charnia is more than eight times older than the oldest dinosaur.
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It lived about 560 million years ago.
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But compared with the age of life itself, that's nothing.
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Before Charnia and other complex organisms existed,
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the only living things were microscopic single cells.
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They first appeared about three and a half billion years ago
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when the Earth was a very different place.
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The early continents were still forming.
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The days were a mere six hours long, because at that time
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the Earth was spinning much faster on its axis than it does today.
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The land was dominated by volcanoes -
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hostile and lifeless.
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But deep in the oceans, life had begun.
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The latest theory is that chemicals spewing from underwater volcanic vents
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solidified and created towers like these,
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and this produced the conditions needed for the first cells to form.
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Some of these began to harness the energy of sunlight, just as plants do today, and formed colonies.
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These rocky stromatolites in western Australia
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have been constructed by very similar photosynthesising bacteria.
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Others managed to survive by extracting nourishment directly
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from the environment, like the fungi and animals that would later evolve.
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This state of affairs continued for a vast period of time.
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For some three billion years, simple microscopic organisms
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were the most advanced form of life on the planet.
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That's way over half the entire history of life on Earth.
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And then suddenly, within the space of a few million years, a mere
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blink of the eye in evolutionary terms, advanced organisms appeared.
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Why is a mystery,
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but we may find some clues to it on the coastline down here.
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On the Eastern coast of Canada, there is evidence of an event that
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may well have been the spark that started the evolution of animals.
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These rocks have been dated by radioactivity
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to just before the moment that life became very complex.
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So if we can understand the circumstances under which these rocks were formed,
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we may get a clue as to why it was that life suddenly became more complex.
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Fragments of red stone are embedded in the darker rock.
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They look out of place.
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And, in fact, they are.
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Geologists call them drop stones.
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They were transported here by glaciers.
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As the ice moved off the land,
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it floated out over the sea in a great shelf,
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carrying with it stones that it had gathered on the continents.
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And when the ice eventually melted,
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the stones fell into the sediments on the sea floor.
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This wasn't the only place covered by ice.
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Drop stones of the same age have been found in deposits all over the world.
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The evidence points to a global spread of glaciation.
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Just before complex life appeared, the world was in the grip
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of the biggest ice age in its entire history.
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It's been called Snowball Earth.
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The Earth was plunged into a deep freeze
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so severe it probably extended
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from pole to pole.
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The surface of the seas were frozen over.
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On the continents, ice caps and glaciers developed.
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In places, the ice was probably a kilometre or so thick.
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We still don't know enough about the details, but it's likely that
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those conditions lasted for millions of years.
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Stromatolites and similar bacterial colonies that dominated the Earth
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were crushed under the advancing glaciers.
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Life was nearly annihilated before it had truly begun.
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It's difficult to imagine how life managed to survive in those circumstances.
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But survive it did.
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Microbiologist Dr Hazel Barton
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believes that modern glaciers can tell us how it did so.
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She has come to the Columbia Icefield in the Rocky Mountains
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in search of organisms that are still able to endure such extremes today.
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The thing about being here
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is it looks like everything's been wiped clean,
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the glacier's come through and it's destroyed all life,
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there's nothing living.
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But to a microbiologist this looks a bit like a rainforest.
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From here you can see discolouration on the surface of the ice,
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but that's not dirt -
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that is photosynthetic bacteria that are surviving there
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and that creates an ecosystem where you have plants
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and you have predators come in and feed on those organisms.
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So even though it looks dead, it's actually wildly alive with life.
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The kind of life you can see here is pretty ancient.
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They've had to adapt to a lot of global catastrophes.
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They had to adapt to Snowball Earth.
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Microorganisms that live in these harsh environments we call extremophiles.
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They have an amazing amount of adaptability that's hardwired in their genomes.
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You can freeze them, you can bury them a mile down in ice
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and its not much of a hindrance because of their adaptable nature.
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We owe our existence to ice-dwelling extremophiles.
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Snowball Earth almost extinguished life,
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but tiny organisms like these hung on for millions of years.
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I think what you had is
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organisms that could withstand extreme environments
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conditioning themselves to this changing ecosystem.
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You had a skin of microbes on the surface of the planet,
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and you had these organisms living between where the, the glaciers contacted the rock,
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and that was enough life trickling over so that
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when those conditions retreated, and it became more favourable,
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then it was like, pff, and everything took off again.
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Finally, Snowball Earth began to warm.
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There is evidence that around this time,
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there was a global surge in volcanic activity.
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Eruptions punched through the ice, spewing carbon dioxide into the air.
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As it spread through the atmosphere, it produced a greenhouse effect,
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trapping heat so that the earth warmed and the ice melted.
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We still have a lot to discover about what happened next,
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but it seems likely that it was the melting of Snowball Earth
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that led to the next great development of life.
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As the glaciers retreated,
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so nutrient-rich meltwater flooded into the oceans.
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For the surviving cells, this flood of ground-up rock was a bonanza.
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For the microbes that could photosynthesise,
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the pulverised rock was a potent fertiliser.
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And their growth would have a direct influence on early animal cells.
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Cyanobacteria and other oxygen-producing microbes
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began to bloom across the globe.
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These flourished in colonies of plant-like microbes
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that pumped out enormous volumes of oxygen.
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And it was this increase in oxygen
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that was the key to the rise of the animal kingdom.
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Now, simple microscopic life
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had the fuel it needed to develop into something bigger.
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After billions of years of single-celled life,
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something amazing happened in the deep sea.
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Up to this moment, living cells that had been produced by division
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simply drifted away from one another.
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But now, with the aid of increased oxygen,
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some cells were sticking together.
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Some of these clumps ultimately evolved into animals.
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To find out how oxygen drove this process,
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I have come to Australia's Barrier Reef,
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to look at one of the most primitive of animals alive today -
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one that can truly be called a living fossil.
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It is one of the simplest multi-celled organisms that we know,
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but its basic body structure has nonetheless enabled it
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to survive virtually unchanged for around 600 million years.
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It's a sponge.
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Sponges are just collections of simple cells
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that have clumped together and got stuck together.
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They don't have a digestive system or a nervous system
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or a blood circulatory system,
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and they get their food and their oxygen
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by just pumping seawater through channels in the body.
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But they can give us an indication of how it was that cells
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first clumped together to form bodies of any real size.
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At the microscopic level, sponge cells are bound together
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by a tangle of hairy, stringy protein molecules called collagen.
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This collagen glue is found only animals, and nowhere else.
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Collagen is sometimes called the sticky tape of the animal world.
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It's the commonest protein in our body.
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It forms the framework of our skins.
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Plastic surgeons use it to pump up our lips.
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You need oxygen to manufacture collagen
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and with the rising amount of oxygen in the atmosphere
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at the end of Snowball Earth, cells were able to manufacture it.
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At the Research Station on Heron Island on the Great Barrier Reef,
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scientists are working to understand
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how it was that multi-celled organisms
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began to colonise the earth.
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To find the answer, marine biologist Professor Bernard Degnan
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is studying sponges.
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The things that connect sponges to the rest of the animal kingdom
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we can find at the level of the cell and the gene.
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When we look at its genes, it's clearly an animal.
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We look for the things that bind all animals together,
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so what does a human share not only with a chimpanzee
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and for that matter a tiger but what it shares with a sponge.
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If we can find any common threads,
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we're getting really to the heart of the matter of multicellularity
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in the animal kingdom, so that's the key.
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A classic experiment gives us some insight.
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First, a sponge is cut into small pieces.
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Then it is pushed through a sieve on the end of a syringe.
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This breaks the animal down into its individual cells.
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This may seem a brutal thing to do to a living organism,
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but to a sponge this is of no consequence.
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In response, it does something quite astonishing.
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The cells begin to move...
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and then they form clumps.
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Soon the clumps form bigger clumps,
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until three weeks later, a miniature sponge has formed.
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Sponges have this amazing capacity to regenerate themselves.
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And what we can do is actually rebuild a sponge
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from the cell level up.
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From this experiment, we can maybe infer a few things
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that happened 600 million years ago with the very first animals.
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We can infer that there were cells coming together,
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they could adhere to each other, they used extracellular proteins
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like collagen to glue themselves together.
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They had the ability to communicate with each other
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and a certain amount of flexibility that allowed them to interact
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to give rise to something that's bigger and greater,
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a large macroscopic multicellular animal.
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The advantages of being multi-celled were many.
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Colonies of cells could collect more food,
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control their internal environment
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and act efficiently by working as a team.
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It was just the beginning.
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In Canada, there is an extraordinary place
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that reveals what happened next.
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Here you can see how just a few million years after the melting of Snowball Earth,
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the earliest multi-celled organisms became much more sophisticated...
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and much bigger.
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This is Mistaken Point in Newfoundland.
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It got that name because in years gone by sailors coming up the eastern coast of North America
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but lost in the fogs that are so frequent here
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would head north for the open ocean
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but be wrecked on these savage rocks.
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But today Mistaken Point has a completely different reputation.
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Today it is recognized as one of
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the most important fossil-bearing sites in all the world.
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For here you can see fossils
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of the very first animals that evolved on this planet.
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The fossils in these rocks are both wonderful and bizarre.
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When the sun is low in the sky,
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the slanting light shows up their structure in great detail.
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Organisms were no longer
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just clumps of undifferentiated cells, like sponges.
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They were organized into defined shapes.
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And among them are some that look exactly like Charnia
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that had been first recognised in Charnwood Forest.
301
00:25:15,800 --> 00:25:19,520
Here, there are not only hundreds of examples of Charnia,
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00:25:19,520 --> 00:25:22,800
but a whole community of other strange creatures.
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00:25:22,800 --> 00:25:27,880
Everywhere you look there are complex markings and indentations
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of one kind or another -
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00:25:29,400 --> 00:25:33,600
it's almost as though children have been playing in wet sand.
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It's like walking through a carpet of ancient creatures.
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It's difficult to imagine that 565 million years ago
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00:25:42,800 --> 00:25:45,760
this was the bottom of the ocean
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and these were some of the first animals to live on this planet.
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Here at Mistaken Point,
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exceptional conditions have preserved these delicate life forms.
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00:26:16,720 --> 00:26:19,720
Each one of these layers of rock
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00:26:19,720 --> 00:26:24,080
was once mud lying at the bottom of an ocean.
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An ocean so deep it was very cold,
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and very poor in oxygen,
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so any organism that died here took a very long time to decay.
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But those that did have been preserved
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with an astonishing degree of perfection.
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What makes this place so different?
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There was a volcano rising from the sea floor close by,
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and it spewed out millions of tons of ash.
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The ash sank to the bottom,
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blanketing everything like a sub-marine Pompeii.
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00:27:17,040 --> 00:27:22,560
Over millions of years, the ash itself was buried by muddy sediments
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00:27:22,560 --> 00:27:25,320
and then all was turned into rock.
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00:27:25,320 --> 00:27:28,520
And then, over hundreds of millions of years,
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00:27:28,520 --> 00:27:32,000
mountain-building forces thrust the whole sea-floor upwards
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00:27:32,000 --> 00:27:35,200
to its present position on the coast of Canada.
329
00:27:38,120 --> 00:27:42,960
Dr Guy Narbonne is a world expert on the fossils of Mistaken Point.
330
00:27:45,160 --> 00:27:48,520
What you can see on this surface
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00:27:48,520 --> 00:27:52,800
is the grey is the muddy sea bottom
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00:27:52,800 --> 00:27:55,960
and this is where the creatures all lived.
333
00:27:55,960 --> 00:28:01,880
And they were knocked down and covered by a bed of volcanic ash.
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00:28:01,880 --> 00:28:06,320
And you can see it here and all of this pink and white
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00:28:06,320 --> 00:28:09,240
speckled stuff is volcanic ash.
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00:28:09,240 --> 00:28:12,880
The volcanic ash cast every part of them,
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00:28:12,880 --> 00:28:16,640
like putting plaster around your arm if you break it,
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00:28:16,640 --> 00:28:20,960
and that led to a perfect preservation
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00:28:20,960 --> 00:28:23,480
of every detail of the outside.
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00:28:25,520 --> 00:28:29,080
Radioactivity in this light-coloured ash layer
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00:28:29,080 --> 00:28:33,120
allows Guy Narbonne to date precisely the eruptions,
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00:28:33,120 --> 00:28:35,760
and therefore the fossils.
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00:28:35,760 --> 00:28:40,360
Some are as old as 579 million years.
344
00:28:40,360 --> 00:28:44,720
Here we can see one of the best of the fossils on the surface.
345
00:28:44,720 --> 00:28:50,680
It consists of disks, and they all have these pustules
346
00:28:50,680 --> 00:28:55,080
on them and that's why we rather affectionately call them pizza disks.
347
00:28:55,080 --> 00:28:58,880
And they were very simple in form,
348
00:28:58,880 --> 00:29:03,800
but the first truly large creatures in Earth evolution.
349
00:29:06,160 --> 00:29:10,240
The pizza discs are only one of the species found here.
350
00:29:13,320 --> 00:29:18,640
Most are fern-like fronds, like this enormous species of Charnia.
351
00:29:21,360 --> 00:29:23,760
This is a two-metre-long frond.
352
00:29:23,760 --> 00:29:26,800
- Astounding!
- And this is not the biggest.
353
00:29:26,800 --> 00:29:29,480
We have about 200 specimens of this here.
354
00:29:31,680 --> 00:29:35,760
The frond of Charnia found in Charnwood was isolated.
355
00:29:37,360 --> 00:29:43,760
But here at Mistaken Point, a whole community of organisms has been preserved together...
356
00:29:43,760 --> 00:29:48,160
and that could give us new information.
357
00:29:48,160 --> 00:29:52,800
You're calling this an animal but is it justified to call it an animal?
358
00:29:52,800 --> 00:29:54,680
- Well...
- It's rather plant-like.
359
00:29:54,680 --> 00:29:57,960
Well, "What is it?" is a big question.
360
00:29:57,960 --> 00:30:00,560
We know for a fact it can't be a plant
361
00:30:00,560 --> 00:30:03,640
because we're in water thousands of metres deep,
362
00:30:03,640 --> 00:30:06,720
there wouldn't have been enough light to read a newspaper.
363
00:30:06,720 --> 00:30:11,000
We're several orders of magnitude too little light for photosynthesis.
364
00:30:11,000 --> 00:30:14,440
OK, so it's not photosynthesising because it's too deep
365
00:30:14,440 --> 00:30:17,360
and therefore it's not a plant. What's it living on?
366
00:30:17,360 --> 00:30:23,880
What we believe they're living on is dissolved carbon and other nutrients in the deep oceans.
367
00:30:23,880 --> 00:30:29,480
So it's absorbing these nutrients through its entire body.
368
00:30:29,480 --> 00:30:34,880
Very thin. Probably not much thicker than your thumbnail.
369
00:30:34,880 --> 00:30:37,160
Very primitive.
370
00:30:39,400 --> 00:30:43,880
These organisms were very simple animals.
371
00:30:43,880 --> 00:30:49,440
Beyond the reach of light, they had to survive by absorbing chemical sustenance.
372
00:30:49,440 --> 00:30:54,320
But most animals we know today are able to move about.
373
00:30:54,320 --> 00:30:58,520
Even sponges and corals have swimming larvae.
374
00:30:58,520 --> 00:31:01,400
But there's no evidence of that here.
375
00:31:03,160 --> 00:31:06,840
The creatures were all immobile.
376
00:31:06,840 --> 00:31:08,680
Nothing could move.
377
00:31:08,680 --> 00:31:10,880
Nothing had a mouth,
378
00:31:10,880 --> 00:31:13,400
nothing had muscles.
379
00:31:14,920 --> 00:31:17,440
Probably none of them had colour,
380
00:31:17,440 --> 00:31:21,520
probably an eerie whiteish colour to everything.
381
00:31:23,560 --> 00:31:29,040
These are the oldest large multi-cellular creatures on Earth,
382
00:31:29,040 --> 00:31:32,680
the oldest things that might be called proto-animals.
383
00:31:34,200 --> 00:31:38,280
This is not like anything that exists on earth today.
384
00:31:38,280 --> 00:31:41,600
Even though they're not directly related to us,
385
00:31:41,600 --> 00:31:47,320
like some distant relative, they provide us with a view of our own beginnings.
386
00:31:50,920 --> 00:31:55,480
One of the most peculiar things about these wonderful proto-animals
387
00:31:55,480 --> 00:31:58,440
is the way they constructed their bodies.
388
00:32:00,360 --> 00:32:05,280
Unlike modern creatures, they had a very simple pattern of branching.
389
00:32:10,120 --> 00:32:14,280
Despite their size, these are still very simple animals.
390
00:32:14,280 --> 00:32:18,360
They can be put together with just six to eight genetic commands,
391
00:32:18,360 --> 00:32:25,520
as against some 25,000 such commands that were needed to construct a mammal like me.
392
00:32:25,520 --> 00:32:28,040
You can see this if you look at them in detail.
393
00:32:28,040 --> 00:32:31,840
You see that they are made up of a series of very small modules
394
00:32:31,840 --> 00:32:35,640
which are attached to one another in a number of different ways.
395
00:32:37,320 --> 00:32:43,760
Their modular or fractal way of building their bodies is one of Guy Narbonne's main areas of research.
396
00:32:46,080 --> 00:32:50,000
His study is centred on one particular species.
397
00:32:51,560 --> 00:32:53,080
This is Fractofusus.
398
00:32:53,080 --> 00:32:56,040
It's the most common fossil in the Mistaken Point assemblage.
399
00:32:56,040 --> 00:32:58,600
We have literally thousands of specimens.
400
00:32:58,600 --> 00:33:01,640
And it would have lain on the sea bottom like you see there.
401
00:33:01,640 --> 00:33:05,520
A spindle-shaped mass, very thin.
402
00:33:05,520 --> 00:33:08,640
It consists of these elements.
403
00:33:08,640 --> 00:33:10,720
And there are 20 of them on either side.
404
00:33:10,720 --> 00:33:13,440
And if you look at an individual element,
405
00:33:13,440 --> 00:33:15,760
it's remarkably finely-branched.
406
00:33:15,760 --> 00:33:18,640
It's a style we called fractal or self-similar.
407
00:33:20,160 --> 00:33:24,280
These fractal organisms grew by repetitive branching,
408
00:33:24,280 --> 00:33:27,840
with each branch exactly the same as its predecessor
409
00:33:27,840 --> 00:33:30,200
from the microscopic level upwards.
410
00:33:32,760 --> 00:33:37,440
It was a simple, yet extremely, effective way of building a body.
411
00:33:44,720 --> 00:33:50,320
Such finely-divided branches gave the organism a huge surface area,
412
00:33:50,320 --> 00:33:55,480
and this allowed them to absorb nutrients directly without mouths and without guts.
413
00:33:58,120 --> 00:34:02,160
This simple fractal body plan proved very successful.
414
00:34:03,680 --> 00:34:09,080
So animals using it grew large for the first time in the history of life on Earth.
415
00:34:13,160 --> 00:34:19,720
Fractal design was perfect for getting these earliest creatures off and running
416
00:34:19,720 --> 00:34:21,800
and its easy to see why.
417
00:34:21,800 --> 00:34:26,160
It takes a minimum of genetic programming in order to make one.
418
00:34:26,160 --> 00:34:29,320
You could probably do it with six or eight codes in your PC
419
00:34:29,320 --> 00:34:32,720
to make something that was fractally branching.
420
00:34:32,720 --> 00:34:37,520
And then combining them to make up larger elements is literally child's play,
421
00:34:37,520 --> 00:34:43,560
like a toddler might take Lego blocks and put them all together in order to make up a larger structure.
422
00:34:47,640 --> 00:34:54,920
The fossils of Mistaken Point provide a detailed record of fractal animals.
423
00:34:54,920 --> 00:35:00,040
But the absence of anything like them in more recent rocks is very significant.
424
00:35:02,560 --> 00:35:07,720
Just a few million years after they first evolved, they vanished.
425
00:35:09,240 --> 00:35:11,600
They have no living descendents.
426
00:35:11,600 --> 00:35:14,280
They were an evolutionary dead end.
427
00:35:15,800 --> 00:35:17,480
And the reason?
428
00:35:17,480 --> 00:35:21,280
The very simplicity of their fractal way of growing.
429
00:35:22,800 --> 00:35:30,120
They utterly dominate about the first 20 million years of the evolution of complex multi-cellular proto-animals.
430
00:35:30,120 --> 00:35:34,320
However, this fast start was also their demise.
431
00:35:34,320 --> 00:35:38,120
Because they were incapable of evolving things like
432
00:35:38,120 --> 00:35:43,120
guts and brains and muscles and teeth that later animals did.
433
00:35:45,920 --> 00:35:49,240
If animals were to acquire these things,
434
00:35:49,240 --> 00:35:53,640
they would have to build their bodies in a completely different way.
435
00:35:53,640 --> 00:35:58,440
And eventually, animals appeared that did exactly that.
436
00:36:00,600 --> 00:36:05,120
To see them, I'm travelling south from Newfoundland across the equator
437
00:36:05,120 --> 00:36:06,880
to South Australia.
438
00:36:12,720 --> 00:36:15,320
The Ediacara Hills.
439
00:36:17,560 --> 00:36:25,560
Here lie animals whose body plans are fundamentally the same as those of almost all animals alive today...
440
00:36:25,560 --> 00:36:27,240
including us.
441
00:36:29,800 --> 00:36:35,920
The creatures that are preserved here lived just after fractal animals began to die out.
442
00:36:41,720 --> 00:36:48,840
And about 550 million years ago, their differently-organised bodies gave them something quite new...
443
00:36:52,320 --> 00:36:53,840
..mobility.
444
00:36:56,200 --> 00:37:01,320
But how and why did animals first begin to move?
445
00:37:01,320 --> 00:37:06,040
Scientists are beginning to find answers to those fascinating questions.
446
00:37:06,040 --> 00:37:11,040
And much of the detail comes from these extraordinary fossils behind me.
447
00:37:15,280 --> 00:37:20,600
A team of scientists, led by palaeontologist Dr Jim Gehling
448
00:37:20,600 --> 00:37:23,280
is uncovering the evidence in great detail.
449
00:37:25,520 --> 00:37:27,880
When you have these beds covered in red clay
450
00:37:27,880 --> 00:37:31,880
you have a good chance of the beds having well-preserved fossils.
451
00:37:31,880 --> 00:37:34,800
This is the original sea floor.
452
00:37:36,880 --> 00:37:42,160
And this sea-floor was very different from that in the deep waters of Mistaken Point.
453
00:37:42,160 --> 00:37:44,360
This was once a shallow reef.
454
00:37:44,360 --> 00:37:47,120
It is 550 million years old.
455
00:37:48,960 --> 00:37:53,360
The surface of the ocean floor was covered with organic ooze.
456
00:37:53,360 --> 00:37:56,520
It may have even been green or orange. We don't know the colour.
457
00:37:56,520 --> 00:38:03,560
But there was a lot of organic material made up by bacteria and all sorts of microorganisms.
458
00:38:03,560 --> 00:38:10,480
But sitting in and amongst that garden of slime, we would have seen these strange creatures.
459
00:38:13,560 --> 00:38:16,960
Jim Gehling's team is working to decipher the fossils.
460
00:38:16,960 --> 00:38:21,400
But it is not easy because these creatures still lacked any hard parts to their bodies.
461
00:38:25,480 --> 00:38:29,480
If I was working on dinosaurs, I'd go to a spot,
462
00:38:29,480 --> 00:38:34,760
find the bones and carefully dig them up, take them back into the lab, reconstruct the dinosaur.
463
00:38:34,760 --> 00:38:40,640
But I'm not dealing with bones. I'm dealing with soft-bodied creatures.
464
00:38:40,640 --> 00:38:46,280
All you've got are imprints of squishy things living flat on the seafloor.
465
00:38:47,800 --> 00:38:52,160
Despite the challenges, Jim has discovered compelling evidence here
466
00:38:52,160 --> 00:38:55,320
that these animals had begun to move.
467
00:38:58,200 --> 00:39:02,280
On this fossil bed, we find something very interesting.
468
00:39:02,280 --> 00:39:06,560
It's a series of faint, but very definite circles.
469
00:39:06,560 --> 00:39:11,160
They are almost identical in size and they overlap quite often.
470
00:39:11,160 --> 00:39:15,200
And then when you go to the end of the series of discs,
471
00:39:15,200 --> 00:39:21,560
you find a hollow with the imprint of a very distinct fossil,
472
00:39:21,560 --> 00:39:23,120
that of Dickinsonia.
473
00:39:25,080 --> 00:39:28,600
Dickinsonia was a cushion-like creature
474
00:39:28,600 --> 00:39:31,120
that lay flat on the seafloor.
475
00:39:31,120 --> 00:39:36,000
It ranged from the size of a penny to that of a bath mat.
476
00:39:39,360 --> 00:39:43,360
These imprints represent something very important.
477
00:39:43,360 --> 00:39:45,080
They are the first evidence
478
00:39:45,080 --> 00:39:48,600
of a kind of mobility of animals on the seafloor.
479
00:39:50,600 --> 00:39:56,600
The first animal movements were undoubtedly slow, but perhaps even too slow to notice.
480
00:39:56,600 --> 00:40:00,880
To see them in action, you have to speed them up.
481
00:40:04,520 --> 00:40:08,200
Dickinsonia crept from one feeding place to the next,
482
00:40:08,200 --> 00:40:13,160
absorbing the organic matter beneath it and then moving on once again.
483
00:40:13,160 --> 00:40:19,880
Perhaps it moved with the help of hundreds of tiny tubular feet, as starfish do today.
484
00:40:24,280 --> 00:40:32,280
The excavations at Ediacara reveal that Dickinsonia wasn't the only mobile creature around.
485
00:40:32,280 --> 00:40:37,560
Animals everywhere were on the move, actively seeking food.
486
00:40:37,560 --> 00:40:45,320
This shape here is a resting place of a slug-like animal called Kimberella.
487
00:40:45,320 --> 00:40:50,560
And these here, marks, are showing how it fed.
488
00:40:50,560 --> 00:40:52,160
It had a proboscis, a snout,
489
00:40:52,160 --> 00:40:59,440
and it fed by sifting through the mud, making these scratch marks.
490
00:40:59,440 --> 00:41:03,360
But it tells us more than how this animal fed.
491
00:41:03,360 --> 00:41:07,680
It also tells us how it moved because if you look back this way,
492
00:41:07,680 --> 00:41:09,480
this is where is started feeding
493
00:41:09,480 --> 00:41:13,800
and then it moved along here with more feeding marks and grooves,
494
00:41:13,800 --> 00:41:16,720
and then it settled down here
495
00:41:16,720 --> 00:41:19,240
into the mud where its final resting place was.
496
00:41:19,240 --> 00:41:23,200
So this shows that the animal not only fed like that,
497
00:41:23,200 --> 00:41:25,440
it actually moved like that.
498
00:41:27,200 --> 00:41:32,400
Kimberella was a very early ancestor of today's molluscs.
499
00:41:32,400 --> 00:41:34,960
It probably had a single muscular foot,
500
00:41:34,960 --> 00:41:37,440
just as snails and slugs have today
501
00:41:37,440 --> 00:41:41,280
with which it pulled itself along the sea bottom.
502
00:41:41,280 --> 00:41:45,000
Our speeded-up view of the Ediacaran seafloor
503
00:41:45,000 --> 00:41:48,880
gives an idea of what a busy place the oceans had now become.
504
00:42:01,040 --> 00:42:05,560
Whether that movement is by creeping or crawling over the seafloor,
505
00:42:05,560 --> 00:42:07,840
it doesn't matter because that animal
506
00:42:07,840 --> 00:42:12,600
has advantages over an animal that is fixed to the seafloor.
507
00:42:12,600 --> 00:42:14,720
It can move away from danger.
508
00:42:14,720 --> 00:42:18,240
It can move towards richer sources of food.
509
00:42:18,240 --> 00:42:23,760
It can move away from places which are over-colonised by its neighbours.
510
00:42:23,760 --> 00:42:28,120
That gives it an enormous advantage in the history of life.
511
00:42:38,000 --> 00:42:45,000
This new mobility was only made possible by a major change in the layout of animals' bodies.
512
00:42:46,520 --> 00:42:51,640
When we get to Ediacara, we still have some of those beautiful fractal-like forms
513
00:42:51,640 --> 00:42:59,520
that you see at Mistaken Point but in the Ediacara Hills we see something very different
514
00:42:59,520 --> 00:43:01,480
and that is, for the first time,
515
00:43:01,480 --> 00:43:08,360
you see a blueprint for all animals from then on, including ourselves.
516
00:43:09,880 --> 00:43:15,680
'The modern animal body plan is called bilateral symmetry.'
517
00:43:15,680 --> 00:43:17,840
What we see here is Spriggina.
518
00:43:21,680 --> 00:43:23,520
Let's make a cast of the fossil.
519
00:43:25,120 --> 00:43:30,280
Spriggina represents the first ever animal
520
00:43:30,280 --> 00:43:33,800
which had clear bilateral symmetry.
521
00:43:33,800 --> 00:43:38,280
It had a body with a head at one end, a tail at the other.
522
00:43:38,280 --> 00:43:42,480
And almost identical halves, if you split it down the middle.
523
00:43:45,400 --> 00:43:48,760
We see these together with other creatures
524
00:43:48,760 --> 00:43:52,360
which have this kind of body form.
525
00:43:52,360 --> 00:43:56,560
Spriggina is just one of countless kinds of fossils
526
00:43:56,560 --> 00:44:00,160
in the Ediacara Hills that had developed in this way.
527
00:44:01,680 --> 00:44:07,080
It had a head and a tail, and so it moved in a particular direction.
528
00:44:10,800 --> 00:44:16,200
It's quite likely that they had sensory organs concentrated in the head.
529
00:44:16,200 --> 00:44:20,480
Now why does my nose occur near my mouth?
530
00:44:20,480 --> 00:44:24,600
It's a very good reason. I want to smell the food before I ingest it.
531
00:44:24,600 --> 00:44:27,520
Why are my eyes above my mouth?
532
00:44:27,520 --> 00:44:29,280
So I can see what I'm eating.
533
00:44:29,280 --> 00:44:36,520
This head demonstrates that sensory capacity had evolved.
534
00:44:36,520 --> 00:44:41,560
It was able to sense where food was likely to be on the seafloor.
535
00:44:41,560 --> 00:44:47,280
And, therefore, clearly had a mechanism for actually moving towards that food.
536
00:44:49,360 --> 00:44:54,640
Bilateral animals like Spriggina had another advantage.
537
00:44:54,640 --> 00:44:58,680
Between the head and the tail, there are numerous segments.
538
00:45:00,800 --> 00:45:06,760
So these animals could increase in size by simply adding more segments.
539
00:45:06,760 --> 00:45:11,760
What is more, each segment could do a particular job.
540
00:45:11,760 --> 00:45:13,040
Once you start to move,
541
00:45:13,040 --> 00:45:16,040
you develop a front end and that becomes your head.
542
00:45:16,040 --> 00:45:19,160
And you also, by definition, have a back end.
543
00:45:19,160 --> 00:45:23,120
And in between, segments on which you can add appendages.
544
00:45:23,120 --> 00:45:26,680
On that basic pattern, you can add further features.
545
00:45:26,680 --> 00:45:30,960
On the front end, that's where you need sense organs, eyes, feelers.
546
00:45:30,960 --> 00:45:34,200
On the appendages, you can modify them to be hooks and claws
547
00:45:34,200 --> 00:45:36,120
that would help you to catch things.
548
00:45:36,120 --> 00:45:42,400
And at the back end, there will be a pore from which you excrete the waste products.
549
00:45:42,400 --> 00:45:48,440
And that is the basic body plan of almost all the animals that are alive on Earth today.
550
00:45:50,760 --> 00:45:57,360
It had taken 3,000 million years for multi-celled organisms to appear for the first time.
551
00:45:57,360 --> 00:46:03,240
But now, less than 100 million years later, an evolutionary blink of an eye,
552
00:46:03,240 --> 00:46:09,840
animals had appeared that had the same basic body plan as most that live today.
553
00:46:09,840 --> 00:46:13,040
They had heads and tails and segmented bodies.
554
00:46:13,040 --> 00:46:16,000
And they were able to move to find food.
555
00:46:17,520 --> 00:46:21,640
How was it that animals had suddenly become so complex?
556
00:46:24,040 --> 00:46:29,600
The Ediacara Hills may hold the evidence for an answer to that question.
557
00:46:34,480 --> 00:46:38,080
Living organisms don't live forever.
558
00:46:38,080 --> 00:46:46,120
If a species is to survive it has to reproduce and the first simple animals did that very simply,
559
00:46:46,120 --> 00:46:48,480
by straightforwardly dividing.
560
00:46:48,480 --> 00:46:56,240
But if a species is to survive it also has to have the ability to change with a changing environment.
561
00:46:56,240 --> 00:47:01,920
And to do that involves reproducing in a rather different way.
562
00:47:01,920 --> 00:47:09,040
Evidence of how that happened can also be seen is these very ancient Australian rocks.
563
00:47:20,640 --> 00:47:25,640
In 2007, palaeontologist Dr Mary Droser
564
00:47:25,640 --> 00:47:30,040
discovered in these 550-million-year-old deposits
565
00:47:30,040 --> 00:47:34,360
evidence that animals had started to reproduce sexually.
566
00:47:36,960 --> 00:47:41,320
The animal concerned is called Funisia.
567
00:47:44,320 --> 00:47:48,880
If Droser's theory is right, this wormlike creature produced offspring
568
00:47:48,880 --> 00:47:53,440
by exchanging genetic material with other individuals.
569
00:47:53,440 --> 00:47:56,560
This gene-swapping, or sex,
570
00:47:56,560 --> 00:48:02,680
shuffles the genetic pack, greatly accelerating variation and therefore evolution.
571
00:48:07,280 --> 00:48:10,800
Sexual reproduction is absolutely one of the most fundamental steps
572
00:48:10,800 --> 00:48:12,120
in the history of life.
573
00:48:12,120 --> 00:48:14,600
It is why we have the diversity that we have.
574
00:48:14,600 --> 00:48:16,240
It's the birds and the bees.
575
00:48:16,240 --> 00:48:20,680
As far as we know, this is the first evidence of animals' sexual reproduction,
576
00:48:20,680 --> 00:48:24,320
and we're not catching the animal in the act of it,
577
00:48:24,320 --> 00:48:29,520
we're looking at the product of what we conclude was sexual reproduction.
578
00:48:29,520 --> 00:48:33,240
This fossil is key to Mary Droser's argument.
579
00:48:33,240 --> 00:48:37,240
The small circles show where the animals were anchored to the ground.
580
00:48:38,760 --> 00:48:43,440
You can see that these attachment structures are basically all the same size.
581
00:48:43,440 --> 00:48:46,720
They're all about a couple of millimetres in diameter.
582
00:48:46,720 --> 00:48:51,160
And you could go to another bed, and all the Funisia are half a centimetre in diameter.
583
00:48:51,160 --> 00:48:54,360
So the same size are all occurring together.
584
00:48:54,360 --> 00:48:59,960
This uniformity of size in a particular place is, Mary Droser believes,
585
00:48:59,960 --> 00:49:04,560
strong evidence that a new way of reproducing had arrived.
586
00:49:04,560 --> 00:49:06,760
We link this to sexual reproduction
587
00:49:06,760 --> 00:49:11,120
because if you look in modern environments, when you have this kind of size groupings,
588
00:49:11,120 --> 00:49:16,880
that is 99.9% of the time a product of sexual reproduction.
589
00:49:18,240 --> 00:49:25,000
To understand why, I'm travelling 2,000 miles northeast of Ediacara to the Great Barrier Reef.
590
00:49:29,120 --> 00:49:35,880
Here, there are modern creatures that reproduce in the way that Funisia is thought to have done.
591
00:49:35,880 --> 00:49:38,120
They're corals.
592
00:49:46,960 --> 00:49:51,600
Corals, like Funisia, are anchored to the seabed.
593
00:49:51,600 --> 00:49:56,200
They feed by filtering food from the water.
594
00:49:58,760 --> 00:50:04,400
And the way they breed creates one of nature's greatest annual spectacles.
595
00:50:06,800 --> 00:50:11,720
Once a year, there's an important event among the corals.
596
00:50:11,720 --> 00:50:13,800
We're not sure how it's coordinated.
597
00:50:13,800 --> 00:50:16,360
It probably has something to do with the moon.
598
00:50:16,360 --> 00:50:22,240
But it gives us a hint as to how sexual reproduction might have first appeared.
599
00:50:30,080 --> 00:50:33,280
At exactly the same time,
600
00:50:33,280 --> 00:50:38,920
the corals release countless millions of sperm and eggs all at once.
601
00:50:48,760 --> 00:50:52,760
The event is precisely timed to maximise the chances
602
00:50:52,760 --> 00:50:54,520
of fertilisation.
603
00:50:56,040 --> 00:50:59,840
Millions of offspring are simultaneously conceived.
604
00:51:05,480 --> 00:51:09,680
So, as the coral grows, the individuals that make up
605
00:51:09,680 --> 00:51:15,160
the colonies are all of exactly the same age and size,
606
00:51:15,160 --> 00:51:17,360
just like Funisia.
607
00:51:22,040 --> 00:51:26,520
It's unlikely that Funisia was the first animal to reproduce sexually.
608
00:51:26,520 --> 00:51:33,640
But its discovery suggests that many other animals are also reproducing by mixing their genes.
609
00:51:33,640 --> 00:51:39,440
And that might explain how complex animals evolved so quickly.
610
00:51:44,120 --> 00:51:48,600
The arrival of sexual reproduction speeded evolution.
611
00:51:48,600 --> 00:51:53,520
Here was a mechanism that produced greater genetic variation more quickly.
612
00:51:53,520 --> 00:51:59,560
So, over many generations, species were able to adapt to their changing environments.
613
00:52:01,080 --> 00:52:07,600
550 million years ago, animal life was on the verge of a major advance.
614
00:52:09,160 --> 00:52:15,720
In an environment where animals were becoming more mobile, they would have to adapt fast.
615
00:52:15,720 --> 00:52:19,320
Movement requires a lot of energy.
616
00:52:19,320 --> 00:52:22,600
Simply absorbing nutrients through the surface of the body
617
00:52:22,600 --> 00:52:26,120
as Dickinsonia did was much too slow a process.
618
00:52:28,200 --> 00:52:32,360
Mobile animals would need to consume huge quantities of food.
619
00:52:32,360 --> 00:52:37,000
And they would do that by evolving the very first stomachs, mouths and teeth.
620
00:52:39,960 --> 00:52:44,120
You can see how they might have done so in Switzerland...
621
00:52:48,040 --> 00:52:53,360
..where a new kind of technology provides a window into the past.
622
00:53:00,600 --> 00:53:06,400
This stadium-sized building houses one of the world's most powerful microscopes.
623
00:53:11,440 --> 00:53:14,480
It's called the synchrotron.
624
00:53:19,360 --> 00:53:25,080
Professor Philip Donoghue is preparing the tiniest of fossils for the synchrotron.
625
00:53:27,400 --> 00:53:33,080
These miniscule balls were excavated from a quarry in South China.
626
00:53:33,080 --> 00:53:38,680
Each and every one of them is the fossilised embryo of an ancient creature.
627
00:53:42,840 --> 00:53:45,400
If we really want to understand these fossils,
628
00:53:45,400 --> 00:53:48,080
what we need to do is not just to look at the surface
629
00:53:48,080 --> 00:53:50,360
which we can do with an electron microscope.
630
00:53:50,360 --> 00:53:51,520
We need to look inside.
631
00:53:51,520 --> 00:53:56,720
We have to use some form of X-ray tomography, a bit like CAT scanners in hospitals.
632
00:53:56,720 --> 00:54:03,160
But we have to use one that allows us to look at the very tiniest details down to a thousandth of a millimetre.
633
00:54:03,160 --> 00:54:06,280
The synchrotron is the only X-ray type machine that provides
634
00:54:06,280 --> 00:54:11,760
the kinds of resolution that we need to see all the tiny details within the fossilised embryos.
635
00:54:13,280 --> 00:54:15,800
KLAXON SOUNDS
636
00:54:17,200 --> 00:54:21,640
It was astonishing, I mean it was a real eureka moment
637
00:54:21,640 --> 00:54:26,040
that you could get to the very finest levels of fossilisation,
638
00:54:26,040 --> 00:54:30,280
the very finest detail that the fossil record could ever give up using this technology.
639
00:54:38,920 --> 00:54:46,320
Powerful generators fire high-energy electrons around a circular tube at close to the speed of light.
640
00:54:50,200 --> 00:54:58,040
After one million orbits, the electrons emit X-rays so powerful, they can penetrate solid rock
641
00:54:58,040 --> 00:55:00,240
or these tiny fossils.
642
00:55:02,160 --> 00:55:05,160
Donoghue uses data from the synchrotron
643
00:55:05,160 --> 00:55:08,600
to build a three-dimensional picture of the fossils.
644
00:55:10,120 --> 00:55:15,600
We know it's a fossil embryo because it's surrounded by a preserved egg sac.
645
00:55:15,600 --> 00:55:20,200
And using tomography we can see inside to the developing animal.
646
00:55:25,480 --> 00:55:30,520
This fossil is the embryo of a tiny marine worm called Markuelia.
647
00:55:32,040 --> 00:55:36,680
It lived just twenty million years after the animals of Ediacara.
648
00:55:43,440 --> 00:55:48,360
Using his 3D model, Donoghue is able to see inside it
649
00:55:48,360 --> 00:55:51,880
and there he found evidence of something new.
650
00:55:53,760 --> 00:55:58,160
These fossils provide the first clear evidence for a gut within animals.
651
00:55:58,160 --> 00:56:03,360
We can clearly see that there's a mouth right at one end
652
00:56:03,360 --> 00:56:06,280
surrounded by rings of teeth that extend inside the mouth.
653
00:56:06,280 --> 00:56:10,840
And then there's a gut that extends all the way through to an anus at the other end.
654
00:56:12,360 --> 00:56:20,000
Internal digestion enabled Markuelia to extract energy from its food in a very efficient way.
655
00:56:23,280 --> 00:56:29,120
And the fact that it had teeth suggests that it had a new diet -
656
00:56:29,120 --> 00:56:30,960
other animals.
657
00:56:33,400 --> 00:56:38,240
The fact that it's got rings of teeth arranged by its mouth, that it would have averted out
658
00:56:38,240 --> 00:56:43,080
or it would have ejected out of its mouth to grasp prey items, tells us that this thing was a predator.
659
00:56:47,520 --> 00:56:50,840
For the first time, there were hunters in the oceans.
660
00:56:50,840 --> 00:56:55,800
And that had enormous evolutionary implications.
661
00:57:04,400 --> 00:57:11,400
There was about to be an explosion of life that would lay the foundations for modern animals.
662
00:57:16,720 --> 00:57:19,040
In another wave of evolution,
663
00:57:19,040 --> 00:57:23,520
the animal basic body plan became more and more elaborate.
664
00:57:23,520 --> 00:57:27,160
Fearsome predators appeared in the seas,
665
00:57:27,160 --> 00:57:33,720
great monsters on the land and animals became masters of the Earth.
666
00:57:36,280 --> 00:57:42,400
Next time I continue my journey in the Rocky Mountains of Canada,
667
00:57:42,400 --> 00:57:45,160
the deserts of North Africa
668
00:57:45,160 --> 00:57:49,880
and the tropical rainforests of Australia.
669
00:57:49,880 --> 00:57:56,600
I will discover how and why animals evolved skeletons and shells.
670
00:57:56,600 --> 00:57:59,920
How they developed true, picture-forming eyes.
671
00:58:01,040 --> 00:58:04,280
How others went to extraordinary lengths
672
00:58:04,280 --> 00:58:08,120
to protect themselves from attack.
673
00:58:08,120 --> 00:58:14,760
And I shall discover the first animals that moved out of the sea to conquer the land and the air.
674
00:58:36,520 --> 00:58:39,560
Subtitles by Red Bee Media Ltd
675
00:58:39,560 --> 00:58:42,600
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