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00:16Across our natural world, life has taken on countless forms.
00:28Wondrous, strange and endlessly diverse.
00:37It's easy to imagine that all of this is, like, somehow preordained.
00:44That it's been made a world of balance and purpose. But the truth, the truth is much wilder.
00:53This is a world of survivors.
00:58From Earth's earliest moments, evolution has quietly, relentlessly shaped the story of life.
01:09I can hear it.
01:10And in this series...
01:13It's quite emotional, if I'm honest with you.
01:16We'll trace the astonishing evolutionary journeys of five iconic modern animals.
01:23Look at this. Truly spectacular.
01:27We'll meet their oddball ancestors from the distant past and discover how generation by generation...
01:35Absolutely amazing.
01:38They changed to become the creatures we know today.
01:45From the smallest beginnings come the most extraordinary stories.
01:50Stories of survival, of bizarre transformations shaping life in the strangest of ways.
01:57And behind it all, the unstoppable force of evolution.
02:02Beautiful love, of bizarre褕
02:02definition of its creation.
02:10I don't know.
02:59Look at that.
03:02They used to say that animals couldn't experience joy.
03:05Come on.
03:07That looks like muddy, wet joy to me.
03:20The African savannah elephant has to be one of evolution's most enchantingly strange creatures.
03:30I mean, look at the trunk.
03:33When they're adult, that measures nearly two metres in length, and it contains perhaps
03:3990,000 miniature mussels.
03:43And then the tusks.
03:45Those are teeth that never stop growing.
03:49The ears.
03:51Look at the ears on this one.
03:52The size of a tablecloth.
03:55Flapping away.
03:59But their one most obvious defining feature, of course, is their size.
04:05Look at that.
04:09They can regularly reach five, six, seven tons.
04:14The very biggest, ten tons.
04:17They are colossal.
04:21So here's a question for you.
04:23How did evolution come up with something as complex, as beautiful, and as enormous as this?
04:31How did the elephant come to be?
04:38Well, to understand the elephant, the largest land animal alive today, you have to understand
04:48evolution itself.
04:50There was no blueprint, no grand design.
04:57Evolution is a process shaped by powerful, invisible drivers.
05:05Like hunger, conflict, and even catastrophe.
05:17So where does our story begin?
05:22The answer lies in what these giants are made of.
05:29They may be the world's largest land mammals.
05:34They may be beautiful.
05:35But brutally, biologically speaking, this is just a giant mass of cells.
05:42Now, in the case of the elephant, that's a lot of cells.
05:44It's a quadrillion.
05:45That's a one with 15 zeros after it.
05:57Cells are the fundamental building blocks.
06:01Not just of elephants, but of all life today.
06:04Be it animal, plant, fungi, or bacteria.
06:15So where did those cells come from?
06:20Well, each one of this animal's cells has come from other cells, which have either divided
06:27or reproduced.
06:33In fact, we can trace this chain of cells back over unimaginable periods of time, through
06:41many long-lost extinct species until, remarkably, it converges at a single point.
06:49A single-celled organism that's connected to every living thing, every branch on the tree
06:57of life.
06:58A common ancestor that lived billions of years ago.
07:06Now, when it comes to evolution, you need to take the long view.
07:14I mean, the really long view.
07:18The elephant's improbable journey begins before mammals.
07:24Before dinosaurs stomped about.
07:27Before anything even had legs to stomp.
07:31It's a story that starts with a simple truth.
07:38If you want to evolve, you have to survive first.
07:50Violent.
07:52Loud.
07:54Frankly, overdramatic.
07:56The young earth is no paradise.
08:01But beneath the waves, life has already taken hold.
08:11Trillions of tiny primitive cells battle the elements.
08:19Almost all will perish.
08:27But one cell is different.
08:32Within this tiny speck lies the future of all living things.
08:41It's a speck with a name.
08:44Meet Luca.
08:47The ultimate survivor.
08:49The great, great, great times a billion grandparent.
08:53Of you.
08:55The elephant.
08:57And every other living thing on earth.
09:19Luca stands for last universal common ancestor.
09:25So let's just think about this for a moment.
09:28Because it was this single-celled organism, floating around in a world entirely alien to our own,
09:36which gave rise to every living thing on our planet.
09:40That's me.
09:42That's you.
09:42That's all the animals.
09:44All the plants.
09:45All the fungi.
09:45All the bacteria.
09:47Everything.
09:48So Luca isn't just a clever acronym, something out of a biology class.
09:53Luca defines the point where the story of life as we know it truly began.
10:05There are no fossils of Luca.
10:10But because all living things have DNA and use the same genetic code, we know there must be a shared
10:18origin.
10:22Look at that.
10:24But why did Luca and its descendants survive?
10:28Oh.
10:29When trillions of others vanished?
10:32That's actually starting to burn my hand.
10:36Clues can be found in the earth's most extreme places.
10:41I want to set my hand out of there.
10:44That's how hot it is.
10:49With alkaline water up to 86 degrees centigrade,
10:57these are the sort of hostile conditions Luca may have endured.
11:03But nevertheless, look, life is tolerating it all around here.
11:13I know what you're thinking.
11:15This doesn't look like much.
11:17And certainly, compared to us, this is pretty simple stuff.
11:22But I've got to tell you, it's not.
11:24The cells in here are amongst the most complex things in the known universe.
11:29Each one of these cells is generating energy, distributing that energy, dealing with waste.
11:36It's sensitive to its environment.
11:38It's reproducing.
11:40Every one of these cells is more complex than any machine ever made by any human.
11:48Just like these cells, Luca was complex, robust, resilient.
11:55Which may have helped it cling on against the odds.
12:00Now, we know that Luca wasn't the first cell.
12:05And that it lived amongst other cells.
12:07But what made it special is that it didn't just live.
12:11It thrived.
12:13It survived.
12:13That little bubble of chemicals formed in chaos billions of years ago.
12:26Luca was the little cell that could.
12:35Plucky, yes.
12:37Lucky, almost certainly.
12:42But it also has life's greatest survival trick.
13:00Luca can copy itself.
13:04Well enough to keep its genetic line going.
13:08But not so perfectly that every copy is identical.
13:16With every new generation, tiny errors, mutations, creep into its DNA.
13:25And yet, these so-called mistakes fuel evolution.
13:33The story of our modern living world has begun.
13:42Now, it's time to hit fast-forward.
13:48I mean, you can't cover four billion years of evolution without skipping some chapters.
13:56Generation after generation, little mistakes lead to entirely new life forms.
14:03Some cells begin to capture the sunlight, the ancestors of plants.
14:11Others would adapt to feed on decay.
14:16Fungi.
14:22Many stay small and simple.
14:25The hidden world of microbes.
14:32But the cells that will give rise to the elephant take a very different path.
14:41Three and a half billion years after Luca.
14:47When the Earth is in a deep freeze.
15:04This is a period of intense global cooling.
15:09Ice grips the planet.
15:12And food webs are collapsing.
15:17But somewhere, in the cold and dark, one hungry cell is about to change everything.
15:36The need to feed is one of the great driving forces of evolution.
15:41Any creature that can find its food more efficiently is more likely to survive
15:46and pass its genes into the next generation.
15:49As was the case over 600 million years ago
15:54when a single cell was on the verge of a breakthrough.
15:58A breakthrough that would lead to the incredible diversity
16:02of almost all animal life to come.
16:12Meet the ancient ancestor of the elephant.
16:17Indeed, of all animal kind.
16:29Erkoanazoan now has mitochondria for energy
16:34a nucleus for control
16:40and a tail-like flagellum to move.
16:46But one thing hasn't changed.
16:50This cell is still tiny.
16:56Just a hundredth of a millimetre across.
17:04It's a small cell with a big problem.
17:09Food is brutally scarce.
17:16And that cell's ancient hunger may have set life on a new course.
17:24And you can see how, thanks to a remarkable creature alive today.
17:34You might be wondering, what have a mass of insects like this
17:39got to do with an ancient single-celled organism?
17:43Wow.
17:44The twist is that in the quest for food,
17:47they both came up with a similar solution.
17:52And it's down to numbers.
17:57You see, single ants are not very good when it comes to overwhelming prey.
18:05They're simply too small.
18:07They don't have the strength.
18:08So what they've done is turn into a mass-killing machine.
18:16Each one of the individuals has become a cog in that machine.
18:20And this means that they're far more efficient when it comes to handling whatever they're going to eat.
18:28Ow.
18:29Sorry.
18:33These ants act as one giant organism.
18:40Overwhelming their meals with sheer force of numbers.
18:47And when they swarm, almost anything is on the menu.
18:53Crickets, caterpillars, or if they're wounded, even chickens, goats and pigs.
19:00And by the feel of it, even a pack'em.
19:03And there's the parallel with those ancient single-celled organisms.
19:09Because they were about to adopt a similar technique which would change the world forever.
19:18Oh my goodness.
19:20My world's been changed forever, I think, to be quite honest with you.
19:23There were some of them in places that you won't be filming them.
19:28Get off.
19:32Over 600 million years ago,
19:37Ercoanozoan is about to do something revolutionary.
19:45It's surface is coated with sticky molecules.
19:52And when the time comes to divide,
19:56instead of floating off to live independent lives,
20:02the two remain stuck together.
20:08They continue to divide.
20:12More and more cells stick together.
20:18Until...
20:19Until...
20:20A vast alliance forms.
20:30Dubbed the Death Star.
20:34It's a hundred times larger than a single cell.
20:42And it has something of the dark side to it.
20:55When all the flagella wiggle,
20:57they create stronger water currents.
21:04Growing in bacteria so the Death Star can feed.
21:12From cells sticking together, came a new way of living.
21:16A multi-cellular organism is formed.
21:29A multi-cellular organism is formed.
21:34To become a neutral cell.
21:37Not just in size, but in complexity.
21:41As individual cells begin to specialise, until something truly revolutionary emerges, the
21:57first bodies on Earth.
22:11The oceans have now warmed, and they're full of life forms, and lurking among them is the
22:20ancestor of the elephant.
22:33No trunk, no tusks.
22:37Just a worm, three millimetres long, dragging itself across the sea floor.
22:47Evolution gave it a body, but one so small and simple, you'd barely notice it.
23:01Building something bigger and more complex would require one vital ingredient, oxygen.
23:11Inside every cell in our body, a slow controlled burn is happening, not with flames of course,
23:17that would be concerning.
23:18But just like this fire, we need oxygen to release energy.
23:25Without it, we would simply sputter out and die.
23:31But for ancient animals, oxygen was largely out of reach.
23:42I've got some earthworms here, charming creatures, creatures of childhood, but not terribly sophisticated,
23:50particularly when it comes to breathing.
23:52You see, just like those early animals, they breathe through their skin.
23:57It's permeable, and as long as it's moist, they can extract oxygen from the air.
24:03But imagine you're living half a billion years ago.
24:08You're much smaller than this, and living at the bottom of an ocean where the oxygen supply
24:13is pitifully low.
24:14Life was small, life was slow, life was stuck.
24:25But this ancient worm has stumbled upon a new way to boost its oxygen supply.
24:36Tiny pores along its body, used to filter food, are now quietly adapting to a new role.
24:44They're able to draw in a fraction more oxygen.
24:50The beginning of a transformation that will allow creatures to grow bigger and stronger.
25:00And beating the competition is what it's all about.
25:10Generation by generation, tiny wrinkles inside the pores deepen.
25:17Folding, twisting, meaning more surface area.
25:23More oxygen.
25:25More oxygen.
25:26Until a whole new body part evolves.
25:39In tracing the evolution of the elephant, or for that matter, any other large land animal,
25:44the appearance of gills is hardly an obvious landmark moment.
25:49After all, elephants aren't famed for their deep-sea diving capabilities.
25:54But the emergence of gills was more than a minor upgrade.
25:59It was an evolutionary quantum leap.
26:07This is the fossil of Unanozoon.
26:10It lived in the Cambrian around 500 million years ago.
26:14What is it?
26:15Well, it wasn't a worm.
26:17It wasn't yet a fish.
26:19But what makes it interesting is this.
26:22You can see these feathery structures running down here in rows.
26:28Some scientists believe that this is the first evidence that we've discovered of gills.
26:37Intricate folds like these can radically increase the surface area that's in contact with water.
26:44Giving the animal the potential to access much more oxygen.
26:50And of course, more oxygen means more energy.
26:54That can mean bigger bodies, faster movement.
26:59This innovation set the stage, not just for fish or for elephants, but also for you and I.
27:09We tend to think of gills as a fish thing.
27:12But once, they were pretty much everyone's thing.
27:18Every animal, every amphibian, reptile, bird, every mammal alive today descended from ancestors with gills.
27:31So, if gills were such a good idea, why did so many of us ditch them?
27:46Well, inside this fish is a clue to one of evolution's boldest leaps.
27:54Look at this extraordinary animal.
27:59This is Protopterus ethiopicus, and it's no ordinary fish.
28:06I mean, superficially, it looks like an eel.
28:09It's got this long dorsal fin running all the way back down to this very spatulate tail here.
28:16Beautiful marbling.
28:18But look, look at these wiggly limbs that are emerging.
28:22Two at the front here, and two more at the back.
28:31Frankly, what a weird-looking animal.
28:36But I'm dodging the big issue.
28:38What makes it special is that it can live in very stagnant water.
28:44Water which is almost devoid of oxygen.
28:46And it can do that because it's a fish with a secret.
28:50Now, it is very, very slimy.
28:53If I can try and pick it up.
28:55I've got to watch my fingers because it's well-armed with powerful crushing teeth.
29:02Whoop!
29:03Come on.
29:04What a slippery customer.
29:06I just want you to be able to see its mouth.
29:08Because it's through that mouth that it's able to draw in deliberately deep gulps of air
29:14into a blood vessel-lined sack where the oxygen can diffuse directly into its circulatory system.
29:25There.
29:29Protopterus ethiopicus, that's its scientific name.
29:33But that adaptation gives it its common name.
29:36This is not a fish out of water so much as a lung fish on land.
29:50This air-gulping ability first evolved in fish 400 million years ago
29:57as a simple backup plan for low oxygen water.
30:01But lungs would become key to one of evolution's giant leaps.
30:09The leap onto land.
30:14We're jumping through time again.
30:17A mere 300 million years.
30:23As animals ventured into new territories,
30:26limbs evolved.
30:31Gills disappeared.
30:35Bodies transformed.
30:39But we're picking up the elephant story.
30:45At an evolutionary crossroads.
31:02In the age of the dinosaurs, life had gone truly XXL.
31:08The largest animals to ever walk the earth.
31:18But the ancestor of the elephant has stayed stubbornly small.
31:29This tiny fuzzball is an early Afrotherian.
31:38It's got a long way to go before it can tower over the savannah.
31:42But its small size is about to pay off.
31:49A rather large lump of rock is coming.
31:55Time's up for the giant dinosaurs.
32:00Mass extinction events don't go well for large animals.
32:04They need too much food when there's not much about.
32:07They're slow to reproduce.
32:08They simply can't bounce back quick enough.
32:11In order to survive, you need to be resourceful, adaptable.
32:15But above everything else, you need to be small.
32:18A bit like this little chap here.
32:20Where is he?
32:23There he is.
32:24Look at that.
32:26That is a tree hyrax.
32:29It's about four or five months old.
32:31What a little beauty.
32:34This tree hyrax is a hand-reared orphan.
32:39Allowing us to get an insight into what the elephant might have looked like before it bulked up.
32:46Because, believe it or not, the hyrax is one of the elephant's closest living relatives.
32:55Okay, he's coming.
32:57Albeit slowly.
32:58Come on.
33:05What about that?
33:07I'm tempted to use the C word.
33:08I mean, he's undeniably cute.
33:10Look at the size of those eyes.
33:14After the asteroid impact, it would have been mammals of this size that were left roaming the Earth.
33:20All of the big species would have been wiped out completely.
33:25Hey, come on.
33:26Mind your footing.
33:32And you can see that it's retained some of the characteristics that help them survive.
33:37It's nimble, it's cautious, undeniably, and it knows how to stay out of trouble.
33:43But, you know, that extinction event wasn't all about devastation.
33:47It also offered up a landscape of opportunity.
33:51A complete continent ripe for repopulation.
34:00With no giant dinosaurs for competition, Africa was an empty stage for evolution to run riot.
34:12The plants waste no time bouncing back.
34:17But the ancestor of the elephant remains small and furry.
34:23To get big, it needs food, and lots of it.
34:28But the hard part isn't finding dinner.
34:33It's eating it.
34:43Plants must be easy to eat, right?
34:45After all, they can't run away, they can't fight back, and they are everywhere.
34:51Well, not exactly, because obviously plants don't want to be eaten.
34:57So, whilst they can't fight or claw their way out of trouble,
35:00they have come up with a formidable range of defences.
35:04Which means that all of this greenery here is almost impossible to eat.
35:11For the ancestors of elephants, plants posed a serious challenge.
35:17Not just because of thorns or toxins, but what they're made of.
35:23Even modern mammals struggle to digest them.
35:27Who's poo?
35:35Well, those of you with horses and ponies will probably get this.
35:40This is zebra poo.
35:44Look at that.
35:45We don't have too much time to admire it from the outside,
35:48but let's delve in straight away.
35:50I'll take this piece here.
35:52Look at that.
35:53It looks like grass clippings.
35:57So, this has been nibbled.
36:00It's been munched.
36:01It's gone through the stomach, all the way through the gut of the zebra,
36:05and yet it's barely digested.
36:07And that's because the bulk of the material you can see here
36:11is something called cellulose.
36:13It's the tough stuff that gives plants their strength and rigidity.
36:17But think about it.
36:19If a contemporary, complex, specialised herbivore, like a zebra,
36:24can't properly digest this stuff,
36:26what chance would those early mammals have?
36:41In truth, we are not certain whether the ancestors of the elephant
36:45made the leap to plant eating before or after the extinction event.
36:52The fossil record is patchy.
37:03But we do know the leap happened thanks to an unlikely alliance.
37:16Not with the bugs it was hunting.
37:19With something much smaller.
37:22You see, inside the elephant's ancestor,
37:25an invisible army of single-celled microbes is assembling.
37:32It's not an invasion.
37:34It's the start of a vital partnership.
37:40My goodness.
37:42Who says size is not important?
37:44And this is not a termite mound.
37:46It's a termite monument.
37:48It's got to be five metres tall.
37:51Termites are famous for eating wood and other plant material.
37:55But in truth, that's not the whole story.
37:58They do the chewing.
38:00It's other organisms that do the digesting.
38:13Inside termite mounds, we find one of nature's strangest team-ups.
38:23Now, Chris Packham, a bloke who loves animals, why is he smashing up a termite mound?
38:29Well, I've thought long and hard about this.
38:31Firstly, they're extraordinarily resilient animals.
38:34They'll rebuild this really quickly.
38:36And the second thing is, every night, all over here, animals will be breaking into them.
38:41Just consider me the human aardvark.
38:44Besides, what I'm looking for is just under the surface.
38:49There are plenty of termites here.
38:52I'm looking for something else.
38:55Another life-form lives here.
38:57I think this is it.
38:59Small, silent...
39:01Yes, it is.
39:02...and surprisingly useful.
39:04Look at that.
39:08That is termite fungal comb.
39:12Now, the interesting thing about this fungus is that you can only find it in termite mounds.
39:18Nowhere else in the world.
39:21You see, the termites sort of farm it.
39:24They go out and they collect all that dead plant material, which they can't digest themselves,
39:29and then they come back and give it to the fungus.
39:31The fungus does digest the cellulose, and then turn it into substances which the termites can eat.
39:39What about that?
39:42And of course, it's not just termites.
39:48Almost every plant eater you can name has outsourced digestion to microbes.
39:56The only difference...
40:01Most keep their microbial munchers safely tucked away inside their gut.
40:09Just as our bodies evolved, these sorts of partnerships evolved.
40:13It's difficult to know when, though, because we don't have any fossils of prehistoric animals with bacteria in their guts.
40:20But one thing we know for sure, and that is that over millions of years, many species have become dependent
40:26on these sorts of relationships.
40:28Without them, they would simply die.
40:40Sometimes, evolution's boldest moves aren't physical adaptations.
40:45They're partnerships.
40:47And now, thanks to its microbiome, it's a good time to sample the salad bar.
40:58Generation by generation, the gut balloons into a fermentation factory.
41:07Filled with trillions upon trillions of plant-munching microbes.
41:19Just what you need for a plant-based diet.
41:23Just what you need for a plant-based diet.
41:29And less than 20 million years later, we get this charming creature.
41:37An early proboscidean.
41:51Now standing at a respectable one metre tall.
41:57But evolution has hit a problem of its own making.
42:01This proboscidean has elongated front teeth.
42:08Great for snagging vegetation.
42:16But big teeth can have drawbacks.
42:32This is the skull of an adult hyrax.
42:37It's got these massively oversized incisors there.
42:43What are those teeth for?
42:45Well, for seeing off predators.
42:47Things like snakes and eagles.
42:48For displaying to other hyrax.
42:50And if they cross the line, for seeing them off too.
42:53But we've got to remember that this is a herbivorous animal.
42:56How's it going to be nibbling leaves with these in the way?
43:01Well, it's going to struggle.
43:03And I can demonstrate that by adapting my own teeth with some elongated incisors of my own.
43:12And then try and tuck into a hyrax salad.
43:20Frankly, it's just not working.
43:23So look, whilst big teeth can be impressive, and they certainly have their uses.
43:27If you're a herbivore, they can represent somewhat of an evolutionary challenge when it comes to grabbing your grub.
43:36Big front teeth come with trade-offs.
43:40For the hyrax, it means eating food through the side of the mouth.
43:47But with the proboscideans, evolution went down a different path.
43:57One individual was born with a slightly longer nose.
44:09It's the beginning of something special.
44:24There they are. There they are.
44:26To see what a flexible face could be capable of, we need a snout specialist.
44:34It's like being a lion, isn't it? Going out warthog hunting.
44:39Graceful? Not really.
44:41These are animals built for getting the job done.
44:46Warthogs. So ugly that they've crossed that line back into being beautiful.
44:51But we're not here for a beauty pageant. We're here for biology.
44:54So let's concentrate on their noses. A remarkable multi-tool.
45:02Warthog noses aren't just for sniffing snacks.
45:07They're for digging roots and manoeuvring food into place.
45:15It's tough. It's not a delicate nose like ours. It's really robust.
45:21But even the best nose has its limits.
45:27Especially when your food is on the ground and your face isn't.
45:32The thing is, when you see them standing up, they've got quite long legs and short necks.
45:37So how do you get your nose down closer to the ground?
45:41Well, you do it like that, kneeling down.
45:50OK, so technically, these are the creature's wrists.
45:55But either way, it's a brilliant example of evolution solving a problem of its own making.
46:04Certainly an effective solution, but it's not the only way of meeting that challenge of getting your nose closer to
46:11the ground.
46:12There was a creature that lived millions of years ago that met the challenge in a completely different way
46:17and came up with something even more extraordinary.
46:21A tool, if you like, that it could use for eating, drinking, smelling and exploring the world.
46:33It would be the final flourish of an extraordinary evolutionary journey.
46:40A journey that started 4.2 billion years ago with a single cell.
46:48That multiplied.
46:52And grew in complexity.
46:56Gained a body.
46:58Took a deep breath.
47:01And jumped onto land.
47:08Before teaming up with microbes, giving it the guts to go vegan.
47:17And now, after countless generations,
47:23the nose gets longer.
47:29Stretching down to the ground.
47:32Giving better access to food.
47:35So the body continues to grow.
47:40Until we get an animal of mind-boggling complexity and size that you might just recognise.
47:58Meet Paleomastodon.
48:02It's got the trunk.
48:04It's got the tusks.
48:06Big ears.
48:07Still a work in progress.
48:10But it's a body shape we might finally call an elephant.
48:19And evolution didn't stop there.
48:25From creatures with bizarre jaw extensions.
48:34Others with downward-curving tusks.
48:41And of course, those icons of the Ice Age.
48:46The mammoths.
48:53Giant proboscidians once spanned the globe.
49:01Africa.
49:03Asia.
49:06Europe.
49:07And South America.
49:10We have evidence of our relationship with proboscidians from all over the world.
49:16In the form of these carvings and paintings.
49:20These were not just creatures that were living in that landscape.
49:24We evolved alongside them.
49:28Our histories are uniquely intertwined.
49:35Some proboscidians were lost to natural climate change.
49:40But for others, it was the actions of our own ancestors.
49:50Today, just three species of proboscidian remain.
49:54Each emerging within the last 10 million years.
50:00The Asian elephant.
50:05The African forest elephant.
50:10And the biggest of them all.
50:13A grass-eating giant shaped on the open plains.
50:19The African savannah elephant.
50:27Remarkable.
50:29Oh, you're wonderful, aren't you?
50:33Let's take one last look at these incredible creatures.
50:40Made up of a million billion cells.
50:43Powered by the largest lungs of any land animal.
50:47And in there, a gut coiled up, 20 metres long.
50:52Packed full of microbes.
50:54So it can digest all of this plant material.
50:58And then look at the front here.
50:59These tusks.
51:01And between them, this extraordinary modified nose.
51:04Its trunk.
51:06Strong enough to pick up and carry a human.
51:09Delicate enough to pick up a penny.
51:17The evolutionary journey that created the bizarre and beautiful elephant is just one story.
51:29Because, thanks to Luca, that single-celled, last universal common ancestor.
51:37We are all part of an ancient family.
51:42A family that might be bad at keeping in touch and may be a little dysfunctional.
51:50But is always undeniably miraculous.
52:01Look at this.
52:02I'm literally leading a group of elephants through the forest.
52:07Who would have ever thought it?
52:12Every living thing, everything that's ever walked, swum or flown, is all connected in that one tangled story.
52:23Connected by that thread that runs through a four billion year tapestry of life.
52:35Evolution is messy.
52:37Evolution is unpredictable.
52:39And so grand, we're still really figuring out how it works.
52:43But there is one thing that we do know.
52:45And that is that, given time and the resources,
52:49it comes up with creatures that are as remarkable as this.
52:56And we should cherish all life on Earth.
53:00Not neglect it or destroy it.
53:02Because evolution is wonderful.
53:06Life is beautiful.
53:10You're such a beautiful freak.
53:16I wish there were more just like you.
53:31Next time, how the ostrich got the biggest egg on the planet.
53:36It's quite emotional, if I'm honest with you.
53:40A four billion year love story.
53:44From the first sex...
53:47To conquering the land.
53:52An incredible journey of flirting.
53:56Feathers.
53:58And fornication.
54:01Giving rise.
54:03Look at this.
54:05To one of the most extraordinary birds.
54:17But first, how do we know that all life on Earth has a common ancestor?
54:26For centuries, fossils have provided a window into the past.
54:31Helping scientists reconstruct the tree of life.
54:36In the past, our understanding for how a fossil fits in this larger system of life on Earth was comparative
54:45anatomy.
54:45And it worked for a long time and it was a beautiful tool.
54:48Scientists would look at what animals or other organisms had in common or didn't have in common to try to
54:54recreate their evolutionary relationships.
54:56One thing we have to bear in mind is that when we look at fossils, we're looking at just the
55:00remains, what is left behind, and it's not always complete.
55:03So it's like trying to reconstruct a hand from a fingerprint.
55:05And we made lots of mistakes.
55:11But in the middle of the last century, our discovery changed everything.
55:16The appearance of DNA really was a game changer.
55:20We couldn't study the tree of life with just comparative anatomy.
55:23You need DNA.
55:27We can compare genes to each other, compare those gene sequences to each other, look at the letters that those
55:33genes contain,
55:34and use that information to try to figure out how different organisms are related to each other.
55:42By analysing DNA, scientists have discovered that some creatures that look very different are actually closely related.
55:51Like the Afrotherian mammals.
55:57And it's also allowed us to trace the tree of life back further than ever before.
56:05All the way to its root.
56:10Luca.
56:11Luca.
56:11Luca.
56:12Luca.
56:13The last universal common ancestor to all life on Earth.
56:17It's the last organism that we can point back and say,
56:21this is a relative of not only us, but bacteria and elephants and bananas.
56:25I love thinking of Luca as being not just my great-great-great-great-great-great-whatever grandparent,
56:31but everybody's great-great-great-great-great-whatever grandparent.
56:35In a landmark study, scientists analysed the DNA of 700 different microbial species, searching for patterns that would help them
56:46reconstruct Luca's genetic code.
56:48Our ability to sequence DNA has really unlocked our ability to look deep in time to 4 billion years ago
56:57and come to a better understanding of what our last universal common ancestor may have looked like.
57:04The study revealed that Luca was likely to have had over 2,600 genes, making it surprisingly complex.
57:17So it wasn't necessarily the first form of life, it almost certainly wasn't, but it's the one that got by.
57:23From that one spark, we see the origin of all the life that we see today in its incredible diversity.
57:36Realizing that we all came from Luca, the same seed of the Tree of Life, is really humbling to me.
57:44It's a way of thinking about the world in a much more connected way.
57:49We all came from the same place.
57:53We've not only expanded our understanding of the Tree of Life, but it's changed our understanding of where we fit
58:00into the Tree of Life.
58:05Do you want to know how an elephant is related to a clownfish?
58:09Discover more in a poster from the Open University on the Tree of Life.
58:13To get your free copy, scan the QR code on screen or ring 0300 303 3460
58:20or visit connect.open.ac.uk slash evolution.
58:42www.open.ac.uk
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