- 2 days ago
Category
📺
TVTranscript
00:00Our world is a remarkable place, the only known living planet.
00:30We share the earth with millions of different kinds of plants and animals.
00:38Where did they all come from?
00:47For a few days each year, this remote beach on the edge of the Pacific Ocean can shed some
00:53light on the answer.
00:58One reveals an epic struggle, one that's been going on since the time of the dinosaurs.
01:08It's a battle fought by all living things.
01:15Only the individuals that are best suited to the world in which they live have a chance
01:19of surviving.
01:20It's what we know as survival of the fittest.
01:23And at no point in these babies lives is this more critical than when they leave the nest.
01:42Hungry predators are waiting.
01:52Although they may look the same, each baby is different from the next.
02:06The tiniest variation in size and shape can determine who lives and who dies.
02:19Some are weak, others strong.
02:39Everything that boosts the baby's chances of surviving, such as a sturdier shell or longer
02:44flippers, will be passed on to its young in its genes.
02:49And over time, these inherited changes can lead to the evolution of a new species.
02:58These babies are the genetic veterans of a battle for survival that's been going on since
03:03the first turtles evolved.
03:04Here, only a few make it to the water's edge.
03:22This is natural selection, the way life evolves, and it's been shaping new kinds of creatures
03:29throughout the whole of life's great journey.
03:48And the only living thing on the planet today is the survivor of an unbroken chain of events
03:54spanning nearly four billion years.
03:59And where did it all begin?
04:03In the sea.
04:06Home to the most extraordinary variety of creatures.
04:11And I'm going to meet them.
04:13Two whales.
04:20Flying fish.
04:24The bizarre.
04:27And the brainy.
04:30You are beautiful.
04:33And the downright scary.
04:38OK, fellas, you'll get your chance in a bit.
04:41It's time to start my journey and explore the living seas.
05:00The sea is life's laboratory, where many solutions to the challenges of living were first developed
05:13and tested.
05:17It might be hard to believe, but every living thing today can trace its ancestry back to the
05:23sea.
05:25And that includes us humans.
05:30But this journey is also a personal story, as many of our own features first evolved down
05:36here.
05:38Even today, our own heads and bodies hint at our aquatic origins.
05:53This is you or me, just 24 days after conception.
06:02Every one of us was bathed in a warm, salty sea of amniotic fluid inside our mother's womb.
06:10Here, on the embryo's head, are gill slits, called pharyngeal pouches.
06:17Fish embryos have them too.
06:19In fish, they do turn into gills.
06:22But in humans, they become parts of the face, ear and jaw.
06:27This long tail is another echo of our evolutionary past.
06:44We humans are a tiny shoot on one branch of a giant family tree.
06:50The tree of life.
06:51We're just one of tens of millions of living tips, each representing different species.
06:58And the way they all connect reveals how each and every life form is related.
07:04But why did this dazzling diversity start in the sea, and not on the land?
07:12Let's travel back to life's very beginning, 3.8 billion years ago.
07:34Back then, planet Earth was an unpleasant place.
07:42The atmosphere was thin, there was no oxygen, and no protective ozone layer to shield the Earth from the sun.
07:50Unfiltered ultraviolet rays were beating down on the young planet in a strength that would be lethal to us.
08:04Over time, massive volcanic eruptions and meteor impacts destabilised the land.
08:13Compared to this mayhem, the forming seas were a relative safe haven.
08:35So it must have been somewhere underwater that life first evolved.
08:39Exactly how life began remains a mystery, but there are some clues in this chemical soup.
08:49The seas were awash with organic molecules, the building blocks of all life.
08:55These were formed naturally in the primordial soup of the forming oceans.
09:09These were formed naturally in the primordial soup.
09:11These were formed naturally in the primordial soup.
09:15Somewhere in this cauldron, the recipe for our own DNA appeared.
09:23With this, the first sparks of life were ignited.
09:31Meet the ancestors.
09:33Simple cells like these were the first living things, the predecessors of all future life on Earth.
09:43Over time, these cells diversified and spread around the world.
09:48But one group would have a devastating impact on the planet.
09:51Here, off Western Australia, these ancient microbes still exist today.
10:04Called stromatolites, they secrete strange pillars made of lime.
10:08It's like a scene from three billion years ago.
10:27They might look harmless now, but back then these microbes almost snuffed out all life forever.
10:33By generating huge amounts of a new toxic gas, they triggered a global pollution crisis.
10:48That new gas's name was oxygen.
10:52And it utterly destroyed primitive cells, poisoning them by the billion.
11:00Extinction swept the planet.
11:01Extinction swept the planet.
11:10But a few cells survived and thrived on oxygen.
11:14They inherited the Earth.
11:16From now on, oxygen would power all new life.
11:20From the tiniest cell to the biggest creature of all time.
11:23And that is the greatest oxygen breather of them all.
11:33The largest animal that's ever existed.
11:35The blue whale.
11:36They can be as long as a 737 passenger jet and weigh as much as 30 bull elephants.
11:50Their massive lungs are 400 times bigger than my own.
11:53And when they return to the surface for air, they blow a waterspout 12 meters high.
12:07Every year, migrating blue whales gather here off the coast of California to feed on tiny little shrimp bite creatures called krill.
12:23Blue whales have huge appetites.
12:40They can take in 50 tons of water in one gulp and eat 40 million krill a day.
12:44Here in Californian waters, there are more than 2,000 of these giants.
12:57This is the greatest gathering of blue whales anywhere in the world.
13:01But how could evolution take such a gigantic leap?
13:08Could a blue whale really evolve from a single cell?
13:12With teamwork and cooperation, yes.
13:14Yes.
13:28Cooperating cells.
13:30Sounds a simple solution, but the journey of life took almost 3 billion years to get there.
13:35Among the first sea creatures to benefit from cells pulling together were jellyfish.
14:05These ancient animals were the first to have muscle fibers and a simple nervous system, which allowed the first coordinated movement.
14:20But unlike us, the jelly doesn't know its front from its back.
14:24It just reaches out in all directions.
14:35With the jellyfish, there was no front end, no brain and no great sense of direction.
14:41The alternative strategy was to grow a head.
14:44And with that, life could now move forward.
14:47Would you believe this is one of the most important creatures in the whole journey of life?
15:07The first ever to grow a head.
15:10The flatworm.
15:17And amazingly, it's the foundation of our basic body plan.
15:26We share the very same head sprouting genes.
15:37Flatworms also evolved the very first eyes.
15:42Just a cluster of cells.
15:43They can't do much more than tell light from dark.
15:48But at least the worm has some idea what's coming when it's travelling head first.
15:53And this new information needed processing.
15:58It might be small and very simple, but this is nevertheless the first brain.
16:03So it's thanks to the flatworm that our brains are in our heads and not in our backsides.
16:16If the evolution of the first brain was a milestone event, then so too was the evolution of the first anus.
16:27Imagine having to get rid of all your digestive food through your mouth.
16:31It's not very pleasant, but that's exactly what flatworms and jellyfish have to do.
16:34The flatworm has an extendable stomach with just one opening, and the snag with that is it can't eat and excrete at the same time.
16:51And while some worms stayed flat, others became round.
16:56They developed an internal tube, the through gut.
17:00In through the mouth, along the digestive tract, and out through the anus.
17:06This meant worms could feed non-stop, and the through gut was such an efficient system, that since then, everyone has had one.
17:18But bizarrely, some animals today have evolved an entirely different use for their guts.
17:37This is a sea cucumber. It doesn't look like much, but when it's attacked by a predator, it does something rather extraordinary.
17:48Just holding it can set it off.
17:55Oh, here we go.
17:59God, that is foul.
18:03The sea cucumber throws up not only its stomach contents, but its entire intestines.
18:09A predator would rather leave it alone, and just eat its entrails.
18:14Fortunately, the sea cucumber can still eat by absorbing nutrients through its skin.
18:22And that's not all.
18:24Incredibly, this guy will grow an entirely new set of guts in just a few weeks.
18:28All right, weeper.
18:31But throwing up each time you're threatened is a bit extreme.
18:35Other soft-bodied creatures would need a more practical form of protection to survive.
18:39Around 570 million years ago, there was a major breakthrough, when life chanced upon a winning formula.
18:55The softies turned hard.
18:57The first shells probably developed by accident.
19:09Early snails began to store mineral waste from their diet on their backs.
19:14This hardened into shells.
19:16And as these shells became thicker, or more spiny, they also became predator-proof.
19:30This scallop can clam up if it sees danger coming.
19:44But its simple eyes haven't detected this slow-moving, scallop-eating starfish.
19:49Once it feels the danger, though, the scallop has a surprising reaction.
19:56It's a great escape.
20:17But with its heavy shell, the scallop soon runs out of steam.
20:20Their armour has always weighed snails down.
20:28But half a billion years ago, some escaped the dangers of the seabed altogether.
20:33So how did they do it?
20:35The solution? A buoyancy aid.
20:43Snails filled their shells with gas.
20:46It was the rise of the super snails, the nautiloids.
21:01Later, their cousins rolled up their shells and became the ammonites.
21:05Ammonites were so successful that they would become the most numerous fossil for over 300 million years.
21:21They ranged from tiny little critters like this one...
21:25...to monsters...
21:28...like this.
21:29This shell would have contained a giant two-metre-long slug with tentacles.
21:39These ridges worked as stabilisers, keeping it on an even keel as it bobbed along looking for food.
21:45It was the age of the ammonites.
21:56This fossil graveyard near Lime Regis was formed by just one shoal.
22:01It's part of a huge fossil bed that stretches for several miles inland.
22:04It gives you an idea of just how prolific these creatures were.
22:16But a built-in float wasn't the only answer to a bulky shell.
22:19Because evolving down another branch on the tree of life was a flexible, lightweight suit of armour.
22:28As worn by the very first bugs.
22:31And so the arthropods evolved.
22:35Animals with an external, jointed skeleton.
22:38Their hard bodies fossilised well.
22:40And this is the most famous of them.
22:43The trilobites.
22:47This is just one of the thousands of species of trilobites that existed over hundreds of millions of years.
22:52It's flexible armour allowed body segments to be specialised for different tasks.
23:13And with jointed limbs, they could move fast.
23:16But the trilobite's real trump card was its eyes.
23:22The first to see in detail.
23:25This was an evolutionary bombshell.
23:31For the first time predators and prey could see each other coming.
23:35Eyes became both a hunting tool and the first line of defence.
23:40With them arose superbugs.
23:42The eye generated a deadly race, as each was driven to outdo the other.
24:04The rush to stay ahead sparked an explosion of new life.
24:12This competition has led to some extreme bugs and some extreme eyes.
24:24These are the most sophisticated of any creature on the planet.
24:29And they belong to the mantis shrimp.
24:31Where as our vision just uses three colour pigments, red, blue and yellow, mantis shrimps use at least eight.
24:51Mantis shrimps need such high-tech equipment to hunt their prey.
24:54And more importantly, to avoid each other in this colourful coral world.
25:06For the mantis shrimp is armed with nature's most earth-shattering weapon.
25:10A claw-turned-club.
25:15It's a smash-and-grab attack.
25:20I'd be rather pleased to think we'd evolved from such an impressive creature.
25:22But no such luck.
25:23By comparison, our ancestors are a bit embarrassing.
25:25Nobody knows.
25:26But wherever I'm a-going, I'll go.
25:27Search on the road.
25:28Unlike the superbugs, with their hard exoskeletons.
25:29Or even the super snails, with their hard shells.
25:31I'd be rather pleased to think we'd evolved from such an impressive creature.
25:36But no such luck.
25:37By comparison, our ancestors are a bit embarrassing.
25:41Nobody knows.
25:43But wherever I'm a-going, I'll go.
25:47Search on the road.
25:52Unlike the superbugs, with their hard exoskeletons.
25:55Or even the super snails, with their hard shells.
25:58I'm hard on the inside.
26:02I have an internal skeleton based around my backbone.
26:08My backbone gives my body a strengthening rod.
26:11Without it, I'd be like a sack of spuds.
26:14It was another crucial milestone on life's journey.
26:17Marking the rise of a whole new group.
26:19Our lot.
26:20The vertebrates.
26:21And in all those millions of years that the trilobites and ammonites were cruising the seas,
26:27little vertebrates were busy evolving away.
26:37And this is it.
26:39The ancestor of all the backboned animals, including we humans.
26:43A sea squirt.
26:44Nothing more than a bag of jelly.
26:56The incredible thing is, 80% of its genes are inside us too.
27:02Including those that form the human heart.
27:04But where's the backbone?
27:05The key to that inheritance is found inside its tiny young.
27:15It's these little squirts that have a tail with a flexible rod inside.
27:21The earliest hint of a backbone.
27:24With this flimsy backbone, the first true vertebrates emerged.
27:41Amongst which were the jawless fish.
27:44These jawless hagfish are deep sea creatures that live way beyond our reach.
27:50Here, more than a mile below the ocean surface, they're scavenging on the carcass of a dead whale.
28:02They might look more like worms than fish, but 500 million years ago, jawless wonders like these ruled the seas.
28:10Today, they sometimes rise up to the shallows, and in Sweden's cold, dark fjords, they come face to face with fishermen.
28:34And if they're caught by a predator, just watch what they can do.
28:51Their primitive backbones are so flexible, they can literally tie themselves in knots.
28:59And a slip knot can sometimes be a lye saver.
29:03Being made of flexible cartilage rather than bone, that spine's a whole lot bendier than mine.
29:10There we go. A nice little granny knot there.
29:13And if tying a knot isn't enough to escape a predator's grasp, then the hagfish has another trick up its sleeve.
29:26Oh, look at that!
29:30That is incredible!
29:32It's a really unique defensive mechanism.
29:36The hagfish secretes mucus from glands either side of its body, and this mucus starts to swell when it contacts water.
29:43It also contains these high tensile fibres that forms a shield of slime.
29:48One hagfish can jellify a whole bucket of seawater.
29:58But despite these extraordinary adaptations, jawless fish had soon had their day.
30:04About 400 million years ago, they were sidelined by the results of a new and deadly development.
30:11Somewhere out there, a brand new kind of fish was evolving.
30:18Its front two gill arches gradually grew and encircled the mouth, becoming the first biting jaws.
30:32Such early-jawed fish became the sharks.
30:35And the sharks.
31:05Once primitive fish had developed jaws, an extraordinary range of teeth evolved to fit them.
31:23Sharks teeth are adapted to the diet of their owner.
31:27The sand tiger has narrow pointed teeth for seizing slippery fish and squid.
31:33Other teeth, like the seal sharks, are multi-pointed for feeding on the ocean floor, picking up grabs and shellfish.
31:41The snaggletooth's varied diet needs a tooth like a hunting knife.
31:47While the tiger sharks are more like chainsaws, used to tackle turtle shell and fish bone.
31:56And these belong to the biggest meat-eating shark alive today.
31:59The great white. They slice through the meat of sea mammals.
32:04The biggest teeth of all belonged to the megalodon.
32:07A bus-sized meat-eating monster that was 12 times bigger than a great white shark.
32:12Its jaw was colossal.
32:15Over two metres wide, with hundreds of teeth.
32:18It could have swallowed me whole.
32:19Good job, it's extinct.
32:20Just imagine a jaw this size at the business end of a hungry shark.
32:30Its no wonder megalodon could eat more than a ton of meat in one go.
32:33Some of its relatives are the sharks we all recognize.
32:44But others evolved along a different track.
32:47Some even lost their teeth.
32:48These are stingrays.
32:53And here off the coast of the Cayman Islands, they gather in huge numbers to feed.
33:00Pretty enthusiastically as well.
33:05Ow! Easy now, boys.
33:07Rays are sharks' cousins, but their body plan has flattened out to make the most of life on the seabed.
33:15They are absolutely incredible looking creatures, and the way they move is really, really beautiful.
33:21These rays eat fish, and they know I've got a juicy morsel in my hand.
33:27You have to be a little bit careful when you're feeding them.
33:40Because that mouth has a nasty suck on it.
33:43They don't have much in the way of teeth.
33:46But they've got this bony plate that acts as a grinder.
33:50And it can grind your fingers as well, as I've found out.
33:57These rays usually hunt crabs and fish that they can detect hidden in the sand.
34:11They get very, very friendly when you don't feed them.
34:15Woo! Okay, easy petal.
34:16Stingrays have an array of fine-tuned senses.
34:28It's something all the shark family have taken to a whole new level.
34:33And to show you how good they've become, I'm going to run a little experiment.
34:38This should do the trick.
34:47In the open ocean, surprisingly sound is usually the first cue that alerts a predator to a potential meal.
34:55It travels four times faster in water than in air.
35:00Sharks like this Caribbean reef shark can hear a commotion from at least a mile away.
35:08They have excellent hearing, but instead of having ear flaps on the outside like we do,
35:16a tiny duct carries sound waves into their inner ear.
35:23Next comes the sense of smell.
35:26Blood and fish oil can be detected from 400 metres away.
35:30So this box of fish bits should generate some interest.
35:36Just a single drop of blood in 25 million drops of water is enough to turn a shark's head.
35:43But to pinpoint exactly where the smell is coming from, it has to zig-zag to pick up the trail.
35:49At 100 metres, now the shark knows where I am, thanks to a sense humans don't have at all.
35:56It can't see me, but it can feel me through the pressure waves that I'm creating in the water.
36:07These waves are picked up by the lateral line.
36:11Detectors that run down its body from head to tail.
36:14It's a kind of extrasensory perception all fish have.
36:27And it's only now at around 10 metres that the sharks can actually see me.
36:32And I see them.
36:34In daylight, their vision is about as good as mine.
36:37And now they're checking me out with those big eyes.
36:40The structure of the eye suggests sharks may be far sighted.
36:47They see better at distance than close up.
36:52But once they get this close, another sense kicks in.
36:56They can detect electricity.
37:01Tiny receptors on the snout can register as little as half a billionth of a volt.
37:06That's the electric field around a live fish's body.
37:10Or in this case, in our metal feeding pole.
37:13I'll leave this bit to the professionals.
37:17Whoa! Easy, Jackman.
37:22In the final seconds of attack, the shark goes in blind to protect its eyes.
37:28Closing them just before it bites.
37:31In clear blue water like this, thankfully the sharks can actually see what I am.
37:43Otherwise they may have to use their other senses.
37:46Namely, touch and taste.
37:48And it's all done with the mouth.
37:50And it's this combination of sensory systems that makes the shark such an effective high-tech predator.
38:06You might think that such sophisticated animals would out-compete everything else in the sea.
38:11But the journey of life has never been straightforward.
38:21Several times over the millennia, meteors have shattered the world order and sparked mass extinctions.
38:27But from these extinctions, new opportunities and new creatures arose.
38:46Even the long-established ammonites didn't make it.
38:48But in the shelter of the deep, their relatives survived.
38:52And they could now branch out in a whole new direction.
38:58The super snails rose up and ultimately became the latest in the Kephropod dynasty.
39:04Cuttlefish, octopus and squid.
39:08And squid.
39:15Today, just once a year, millions of opalescent squid gather to breed.
39:19The super snails of the breed.
39:50At just a year old, it's the last act in their short lives.
39:54Once the eggs are laid, most will die.
40:00Grow fast, spawn and die young.
40:03A winning formula in the seas of life.
40:13Keflopod means headfoot.
40:15Not a bad description, really.
40:19This whopper is the giant Pacific octopus.
40:25All head and feet.
40:30It's a gentle giant with an alien physiology.
40:34Blue blood, three hearts and nine brains.
40:37That's one big central brain plus eight mini brains, one in each arm.
40:49If cephalopods were really to compete in the seas, brain power would be their big advantage.
41:05These are Caribbean reef squid, little cuties.
41:20When a barracuda's on the scene, they can think themselves out of a tight spot.
41:29They cleverly change their appearance to match their surroundings.
41:36Both in texture and colour.
41:38An instant transformation that is directly controlled by the brain.
41:42To the predator, it seems that they've simply disappeared.
41:48The squid also communicate to tell each other when the danger has passed.
42:06They have an entire language based on skin tones.
42:20For modern cephalopods, brain power has overcome the need for a protective shell.
42:34They're simply smarter than the average fish.
42:37So why didn't the seas become dominated by clever cephalopods?
42:47That's because just when it looked like brain might triumph over brawn,
42:51fish chanced upon a masterstroke.
42:53And that masterstroke was a skeleton made of a new material, bone.
42:59With it, new bony fish diversified like never before.
43:28The bony skeleton was a landmark development,
43:31providing stronger structural support, greater protection,
43:35more effective gills and improved agility.
43:43Then, for even more subtle manoeuvres,
43:46fish evolved two pairs of matching fins,
43:49joined to both sides of their body by bones.
43:52This really was a winning combination and its legacy would stick.
43:58And that's why we humans have a pair of arms and a pair of legs.
44:05But even bony skeletons have drawbacks.
44:19If you've ever tried racing into the sea, it's virtually impossible to run through.
44:26And that's because water is 800 times denser than air.
44:31And once you're in, it's either sink or swim.
44:34Now, if bony fish were ever to dominate the seas,
44:37they'd have to overcome these same two problems.
44:40How to move fast in a dense liquid,
44:42and how to stay afloat despite heavy bones.
44:46To stop sinking, fish needed the equivalent of buoyancy tanks on a submarine.
45:04Less gas and we sink, more we rise.
45:13But whereas the sub uses compressed air, a fish must carry its gas supply in its bloodstream.
45:25The answer was for fish to come up with an onboard float, the swim bladder, a large gas-filled
45:31sack that inflates and deflates as needed.
45:40Gas diffuses back and forth between the swim bladder and the bloodstream, letting fish float
45:46effortlessly at any depth.
45:50Despite being heavy-boned, the fish is in effect weightless.
45:57Brilliant, but there is one big flaw in this ingenious system.
46:13Diffusion of gas between the swim bladder and the blood takes time, so there's always
46:18a lag period when making buoyancy changes.
46:20For a fast-swimming fish, that's too slow.
46:27So speedsters like the Benito have abandoned swim bladders completely.
46:31But with nothing to stop themselves sinking, they've got to pay the penalty and keep swimming
46:36all the time.
46:50Not all bony fish like life in the fast lane, others have turned to a more sedentary life.
47:02Like this weirdo, for example.
47:08It's a frogfish, and it's come up with a novel use for its bones.
47:12That's no wiggly worm, but a flashy lure, operated by a modified fin bone.
47:29But all these damselfish see is a juicy mouthful.
47:39Not only is the frogfish a master of deception, he's also perfectly camouflaged.
47:46This shrimp is unlikely to see him until he moves, and by then, it's too late.
47:52No matter how quick its reactions, they just can't be quick enough.
47:56As the frogfish jaws move faster than muscle.
48:00How?
48:01Well, that's down to bones again.
48:09It's a trap jaw, preset under full tension.
48:14When triggered, the trap snaps open, increasing the mouth volume ten times, sucking the prey
48:20inside.
48:32But when it comes to bone structure, these small fry are the most extreme of all.
48:39For the first two weeks of their lives, they look like any other baby fish.
48:44Then something begins to go awry.
48:55The face distorts, and one eye starts to shift, moving across to meet the other on the opposite
49:01side of the head.
49:02It's the beginning of a bizarre transformation.
49:13The makeover takes less than a week, and the results are fixed for life.
49:23This flatfish is now perfectly adapted to life on the seabed.
49:27Its body shape and colouring mean it can keep a low profile.
49:32Handy for hiding from predators, or creeping up on prey.
49:38But if you don't have what it takes to hide out on the ocean floor, safety in numbers is
49:43your best bet.
49:48Living in a shoal is a great way to minimise the chances of being eaten.
50:02Throughout their evolutionary history, shoals of bony fish have come under fire from all
50:07sides.
50:11They've survived the age of the plesiosaurs.
50:23And a blitz of aerial attacks ever since.
50:37And all that time, they've also been hunted from below.
50:52I can't believe.
51:04Yeah.
51:05Yeah.
51:06Yeah.
51:11Yeah.
51:12Yeah.
51:13Yeah.
51:16Yeah.
51:17Yeah.
51:20This is predation pressure at its most extreme.
51:26Any fish that can avoid this kind of onslaught will have genes worth passing on.
51:41And pushed to the limit, some fish eventually sought refuge out of the water.
51:47With spectacular results.
51:52Oh, look at that! That is fantastic!
51:58Flying fish! That is going to be the most extreme form of escape known to any fish.
52:04Look at them, girls, there's loads of them!
52:14There's another! That's incredible!
52:17Look at the distance!
52:20Look at them go! Woo!
52:22The flying fish have evolved with extraordinarily long peckerel fins.
52:26They don't flap and they're used to glide instead.
52:31Ooh! Mid-air collision!
52:33They seem to be able to steer once they're up and into the air.
52:37Oh, beautiful back turn.
52:38It's the tail that does it, driving them along like an outboard motor.
52:46It's so powerful that once in the air they can glide for up to 100 metres.
52:51For a predator, it's a vanishing act.
52:53Look at that thing fly!
52:54For a predator, it's a vanishing act.
53:00Look at that thing fly!
53:03Flying fish. Who would have thought it?
53:17Perhaps the most extraordinary bony fish of all.
53:19It just goes to show anything can happen in the pressure cooker that is the crowded seas of life.
53:30And it might well have been predation pressure that forced some fish out of the water permanently.
53:34It was the descendants of the bony fish that colonised the land.
53:42And that's when they hit a new jackpot.
53:45After some three and a half billion years of evolution in the oceans,
53:49they evolved air-breathing lungs and walked out of the sea as landlubbers.
53:56Reptiles, amphibians, birds and mammals like us,
53:59all these land animals share a common ancestor, a fish.
54:08But that's not the end of life's long journey through the seas.
54:13Ultimately, some land mammals developed a taste for seafood
54:17and returned to the oceans to hunt.
54:29Over time, their legs gradually became flippers.
54:43And from an ancestor like this, they would become the most charismatic creatures in the seas.
54:50Today, the result of that evolutionary chain of events are the cetaceans.
54:54That's whales and dolphins.
54:59Fantastic.
55:13These are bottlenose dolphins, the most widespread dolphins in all of the seas.
55:18People just love them.
55:21I think we identify more with this animal than any other sea creature.
55:25Yes, we do, don't we?
55:30For their size, dolphins have the second biggest brain on the planet.
55:35Only a human's is bigger.
55:37Sorry, guys, I beat you.
55:39Yes!
55:40And we're just starting to find out how clever they really are.
55:47Using sign language, we are now able to communicate with trained dolphins like these.
55:52Some can understand more than 2,000 different sentences.
55:56I'm sure we identify and admire the dolphins because they're so intelligent.
56:10But perhaps we should identify more with the smaller, colder sea creatures,
56:14as it's directly because of them and the way they evolved that we are the creatures we are.
56:29We've got wind multicellular, we've got eyes, a backbone, an internal skeleton, two pairs of limbs, a jaw, a heart, a digestive system, a sense of smell, touch and taste, a head and a brain.
56:46It's all down to three and a half billion years of evolution in the spectacular seas of life.
57:16Next week on the journey of life, I'm going to discover how life conquered the hostile land in a story which leads from the sea to the desert.
57:46To be continued...
Recommended
49:05
|
Up next
58:34
58:54
4:48
0:57
7:08
1:58:54
49:51
29:15
46:28
45:06
41:07
47:45
1:24:44
46:47
49:00
37:41
1:25:15
39:36
1:54:22
40:14
49:02