[00:03.20]Since its early origins, there has been a spectacular explosion of life on the planet
[00:17.28]Some creatures have come and gone
[00:26.35]Others have stayed the distance
[00:34.23]All species that have ever lived on the planet are related to each other,
[00:38.43]including us humans - just one result of the journey of life.
[01:01.52]The oceans are teaming with life in all its forms
[01:14.43]This is a journey to discover...
[01:16.27]...how this spectacular diversity came to be
[01:23.21]We'll meet the beautiful...
[01:27.08]...the bizarre... and the extreme...
[01:37.89]...and we'll come face to face with the some of the most feared predators on the planet.
[01:46.33]As we meet these creatures, we'll learn something...
[01:49.17]...of our own aquatic origins...
[01:51.47]...as we journey through the incredible Seas of Life
[02:12.06]There is an enormous variety of life on the planet,
[02:15.73]but how did it come about?
[02:19.73]For a few days each year,
[02:21.37]this remote Pacific beach shed's some light on the answer
[02:27.27]Dawn reveals an epic dramatic struggle...
[02:29.74]...one that's been going on since the time of the dinosaurs.
[02:41.22]It's a battle, fought by all living things,
[02:44.46]only the individuals best suited to the world in which they live stand a chance.
[02:49.33]Its what we know as 'survival of the fittest'
[02:58.17]And at no point in these baby turtles lives is this more critical than
[03:02.64]when they leave the nest
[03:08.81]Hungry predators are waiting.
[03:24.16]Its an instinctive dash from nest to sea
[03:35.47]Some youngsters lag behind.
[03:40.55]The tiniest physical difference determines who lives and who dies...
[03:48.75]Some are weak... others strong
[04:19.28]Chance plays its part too.
[04:24.36]Only a lucky few will make it to the waters edge
[04:33.07]Any trait that increases the odds of a youngster surviving
[04:36.94]will be passed on in its genes
[04:39.94]Its natural selection, and its been going on for billons of years,
[04:44.64]shaping life all over the world.
[05:01.26]You might not think we have much in common with the fish,
[05:04.33]but we actually share the same basic blue print.
[05:07.63]A blue print... formed in the sea
[05:20.18]The seas are life's laboratory where many solutions to the challenges of living...
[05:25.22]were first developed and tested
[05:34.49]Its left its mark on every living thing, including us.
[05:47.01]At one time in our lives we actually had gill slits... and even a tail!
[05:54.58]This is a human being at just 24 days after conception.
[06:00.75]Bathed in a warm, salty sea of amniotic fluid, it's a time of extraordinary growth.
[06:09.36]Here on the head are gill slits or more precisely, 'pharyngeal pouches'...
[06:17.54]Fish embryos have them too, in fish they do turn into gills,
[06:22.31]but in humans they become parts of the face, ear and jaw.
[06:29.35]This tail too suggests that we share ancestors with other animals...
[06:34.25]it's an echo of our own evolutionary past...
[06:41.36]We humans are a tiny shoot on just one branch of a giant family tree
[06:47.20]- the tree of life.
[06:49.07]We're only one of tens of millions of living tips
[06:52.37]each one representing different species.
[06:59.28]And they way they all connect, reveals how every life form is related.
[07:05.45]To trace our roots,
[07:07.09]we'll have to journey back to when the very first life forms appeared,
[07:11.02]three point eight billion years ago!
[07:30.31]So how did life begin?
[07:33.58]Back then, planet Earth was a pretty unpleasant place.
[07:40.42]The atmosphere was thin, there was no oxygen
[07:43.69]and that meant no protective ozone layer to shield earth from the sun.
[07:49.29]Unfiltered ultra-violet rays would beat down on the young planet,
[07:52.93]with a strength that would be lethal to us today.
[08:05.24]And that's not all, massive volcanic eruptions and meteor impacts shook the land.
[08:21.46]Compared to this mayhem, the forming seas were a safe haven,
[08:25.60]and it was somewhere underwater that life must have first evolved.
[08:38.48]The seas were awash with organic molecules...
[08:41.95]...building blocks of all life formed naturally
[08:45.42]in the primordial soup of the early oceans.
[09:03.13]Somewhere in this cauldron, the recipe for our own DNA appeared.
[09:13.48]And the first sparks of life were ignited.
[09:21.39]Meet the ancestors! Simple cells like these were the first living things.
[09:26.99]The predecessors of all future life on earth
[09:32.56]Over time, these cells diversified and spread around the world.
[09:37.30]And one group in particular would have a devastating impact on the planet.
[09:48.21]Here, off Western Australia,
[09:50.62]colonize of these ancient microbes still exist today.
[09:55.25]They form strange pillars made of lime, called stromatilites.
[10:01.49]This could be a scene from three billion years ago.
[10:16.47]They might look harmless now, but back then the microbes almost
[10:20.51]...snuffed out all life - forever.
[10:27.32]By generating huge amounts of a new, and toxic waste gas,
[10:30.96]they triggered a global pollution crisis.
[10:38.60]This new gas was oxygen.
[10:41.10]And it destroyed primitive cells, poisoning them by the billion.
[10:49.27]Extinction swept the planet
[11:00.65]But a few cells survived and thrived on oxygen.
[11:05.29]And they inherited the earth.
[11:07.43]From now on, oxygen would power all life from the tiniest cell,
[11:11.86]to the biggest creature of all time...
[11:16.70]This is the greatest oxygen breather of them all,
[11:19.94]the largest animal that has ever existed, the blue whale!
[11:31.42]Blue whales can be as long as a 737 passenger jet
[11:35.19]and weigh more than 30 bull elephants!
[11:38.99]Their massive lungs are 400 times bigger than our own.
[11:42.83]That means they can dive for 30 minutes on a single breath
[11:46.30]and when they return to the surface for air,
[11:48.40]blow a... spout of water 12 meters high.
[12:01.35]Every year tourists encounter migrating blue whales
[12:04.72]as they gather together off the coast of California...
[12:07.05]...to hunt tiny little shrimp-like creatures called krill
[12:13.39]There can be up to two thousand of these giants at a time.
[12:16.93]It's the greatest gathering of blue whales anywhere in the world.
[12:40.15]Blue whales have huge appetites,
[12:42.72]they can take in 50 tons of water in a single gulp and eat 40 million krill a day.
[13:08.45]How did evolution ever take such a gigantic leap?
[13:12.28]Could a blue whale really have evolved from a single cell?
[13:17.79]With teamwork and co-operation, yes!
[13:27.30]The first step was for single cells to join together to create a more complex living thing.
[13:37.48]For even a whale is really just a vast group of co-operating cells.
[13:49.19]Co-operating cells - sounds a simple solution,
[13:52.89]but the journey of life took almost three billion years to get this far.
[14:07.34]Among the first creatures to benefit from cells pulling together were the jellyfish.
[14:21.19]Jellyfish fossils have been found in rocks formed 670 million years ago.
[14:34.13]These ancient animals were the first to have muscle fibers and a simple nervous system.
[14:42.44]But a jelly fish doesn't know its front from its back.
[14:45.48]It reaches out in all directions, which can leave you going nowhere fast.
[14:54.09]Luckily, evolution had a new strategy up its sleeve
[14:57.32]which would allow life to move forwards.
[15:13.24]Incredibly, this is one of the most important creatures in the whole
[15:16.94]of the journey of life-the first type of animal to grow a head, the flatworm!
[15:27.19]And this worms head start is the foundation of our basic body plan.
[15:32.39]We share the very same head sprouting genes.
[15:48.24]Flatworms also evolved the first eyes.
[15:53.38]Just a cluster of cells they can't do much more than distinguish light from dark.
[15:59.55]But at least the worm has some idea what's coming when its traveling head first.
[16:07.43]All this new sensory information needed processing...
[16:10.33]it might be small and very simple but this is, nevertheless, the world's first brain!
[16:22.01]So it's thanks to the flatworms that are brains are in our heads
[16:25.61]- and not in our backsides!
[16:33.38]If the evolution of the first brain was a milestone event,
[16:36.62]then so too was the evolution of the first anus!
[16:42.43]The flatworm has an extendable stomach, with just one opening
[16:46.46]and the snag with that is it can't eat and excrete at the same time.
[16:51.04]But as some worms stayed flat, other worms got rounder:
[16:54.64]They developed an internal tube - the 'through-gut'!
[17:03.38]In through the mouth... along the digestive tract... and out through the anus!
[17:10.29]This production line meant worms could feed non-stop.
[17:13.93]The 'through-gut' was such an efficient system
[17:17.16]that since then every living creature has had one, including us.
[17:29.51]At this stage in the planets history all animals were soft bodied,
[17:33.71]but this left them vulnerable to predators
[17:41.45]Then around 570 million years ago, there was a major breakthrough,
[17:46.46]when life chanced upon a winning formula - the softies turned hard!
[17:55.33]The first 'shells' were probably developed by accident.
[17:59.17]The early snails began to store mineral waste from their diet on their back.
[18:03.57]And this hardened into a shell.
[18:14.22]Today there are half a million snail species, each with a different kind of shell.
[18:32.34]As these shells became thicker or more spiny, they became predator proof.
[18:43.55]This scallop can clam up if it sees danger coming...
[18:48.02]...but its simple eyes haven't detected this slow moving...
[18:51.46]...scallop eating starfish!
[19:01.27]Once it feels the danger though, the scallop pulls a fast one.
[19:17.22]It's a great escape, but with a heavy shell the scallop soon runs out of steam.
[19:27.73]Half a billion years ago,
[19:29.39]some snails escaped the danger of the sea bed altogether.
[19:33.90]But how did they do that, weighed down by their heavy shells?
[19:39.44]The solution - a buoyancy aid!
[19:45.34]Snails filled their shells with gas... which marked the rise of super-snails.
[20:00.32]Later the nautiloids cousins rolled up their shells and became the ammonites.
[20:12.30]Ammonites thrived for over 300 million years
[20:20.11]This ammonite graveyard in southern England was created by a single shoal.
[20:30.45]Its part of a huge fossil bed that stretches for several miles inland
[20:34.63]and shows how prolific these creatures were.
[20:47.07]With their gas filled shelled, these primitive cephalopods ruled the open seas.
[20:54.48]But a rigid shell wasn't the only possible form of protection
[21:01.95]Evolving down another branch on the tree of life was a flexible,
[21:05.56]lightweight suit of armor: As worn by the very first bugs.
[21:11.70]This is the most famous of them all - the Trilobite.
[21:16.70]Its flexible armor allowed body segments to be specialized for different tasks.
[21:24.24]With the first jointed limbs animals could move faster than ever before.
[21:30.72]The Trilobite's real trump card was its eyes.
[21:34.15]The first to see detail well. This was an evolutionary bombshell.
[21:42.39]For the first time predators and prey could see each other coming.
[21:46.46]Eyes became a hunting tool and first line of defense.
[21:50.97]With them arose the super bugs.
[21:55.41]Eyes triggered a deadly arms race, as hunter and hunted struggled to outdo each other.
[22:14.33]And this rush to stay ahead, sparked an explosion of new life
[22:25.57]This competition has resulted in the some extreme bugs.
[22:32.88]These eyes are the most sophisticated of any creature on the planet.
[22:37.18]And they belong to the mantis shrimp.
[22:47.12]Whereas our vision uses just three color pigments
[22:50.13]- red, blue and yellow - mantis shrimps use at least eight.
[23:01.47]Mantis shrimps need this high tech gear, not just to hunt their prey
[23:05.61]but more importantly to avoid each other in this colorful coral world.
[23:17.25]For the mantis shrimp is armed with earth's most earth-shattering weapon...
[23:24.33]...a thickened claw, turned club!
[23:29.30]It's a smash and grab attack.
[23:41.28]Armored animals were and still are very successful,
[23:44.92]but our ancestor was built very differently.
[23:54.33]Something a bit like this - a sea squirt... nothing more than a bag of jelly.
[24:14.35]The incredible thing is 80% of squirt genes are inside us too
[24:19.48]- including those that form the human heart!
[24:22.95]But where's our backbone.
[24:32.30]The key to that inheritance is found inside the sea squirts tiny young.
[24:41.14]This little squirts have...
[24:42.77]...a tail with a thin flexible rod inside, its the earliest hint of a backbone.
[24:53.45]And from this flimsy start, the first true vertebrates emerged,
[24:57.82]including jawless fish.
[25:01.96]These jawless hagfish, are deep sea dwellers that usually live way beyond our reach.
[25:13.14]Here, more than a mile below the surface,
[25:15.74]they're scavenging on the carcass of a dead whale.
[25:23.61]They might look more worms than a fish but 500 million years ago,
[25:28.12]jawless wonders like these ruled the seas.
[25:46.17]Today, they sometimes rise to the shallows and in Sweden's cold dark fjords
[25:51.41]they may come face-to-face with fishermen.
[26:06.29]And if they think they're in trouble, just watch what they can do.
[26:16.17]It's a unique defensive mechanism.
[26:18.57]The hagfish secretes mucus from glands along both sides of its body
[26:22.84]and it swells on contact with sea water.
[26:25.78]The mucus also contains these hi-tensile fibers that create a shield of slime.
[26:36.39]One hagfish could jellify a whole... bucket full of sea water and
[26:40.29]...that's not its only trick.
[26:42.59]Its primitive backbone is so flexible it can literally tie itself in knots.
[26:47.90]And a slipknot can sometimes be a life saver!
[26:55.47]But about 400 million years ago hagfish were sidelined by an new and deadly trend.
[27:05.58]Somewhere out there a new kind of fish was evolving.
[27:09.49]Its front two gill arches gradually grew and encircled the mouth -
[27:14.12]- becoming the very first biting jaws.
[27:18.16]As possessed by the very first sharks.
[27:30.21]And this was one development the sharks have taken full advantage of.
[27:39.72]Sharks teeth are adapted to the diet of their owner.
[27:44.76]Sharks like the sand tiger,
[27:46.46]have narrow biting teeth for seizing slippery fish and squid
[27:52.63]Other teeth, like those of seal sharks,
[27:55.30]are multi pointed for feeding on the ocean floor,
[27:57.97]picking up crabs and shell fish.
[28:01.47]The snaggle tooth's varied diet requires generalized cutting teeth.
[28:09.31]While the tiger shark's are more like a chain saw
[28:12.72]used to tackle turtle shell and fish bone.
[28:18.59]These belong to the biggest meat eating shark alive today, the great white.
[28:23.29]They slice through the flesh of sea mammals.
[29:17.05]The great white, is one of the biggest success stories in the seas of life.
[29:25.16]But other sharks evolved along a very different track, they even lost their teeth.
[29:39.14]These are the sting rays, and here in the Caribbean off the Caiman Islands,
[29:43.47]they gather in large numbers to be fed by divers.
[30:11.40]Rays are the sharks cousins.
[30:13.44]But their body plan has flattened out to make the most of a life on the sea bed.
[30:21.25]Most are bottom feeders, hunting crabs and fish hidden in the sand.
[30:28.12]Their mouth is underneath their head, so they can't see exactly what they are eating.
[30:32.49]But they can rely on an armory of other senses...
[30:35.19]...which rays and sharks have developed to a whole new level.
[30:39.50]To demonstrate, how finely tuned these senses are we can run a little experiment.
[30:51.34]In the open ocean, sound is usually the first cue
[30:54.51]that alerts a predator to a potential meal.
[30:57.35]It travels four times faster in water than in air.
[31:08.16]Sharks like this Caribbean reef shark...
[31:10.53]...can hear the commotion from at least a kilometer away.
[31:15.13]They have excellent hearing, but instead of having ear flaps like us,
[31:20.34]a tiny duct carries sound waves to the inner ear.
[31:29.61]Next comes the sense of smell.
[31:33.48]Blood and fish oil from this bait box can be detected from 400 meters away.
[31:40.86]Just one drop of blood in 25 million drops sea water is enough to turn a shark's head.
[31:47.53]Then to pinpoint exactly where the smell is coming from,
[31:50.30]it zig zags to pick up the trail.
[32:02.21]100 meters away is still too far away to see the target.
[32:05.68]But a shark can feel it by the pressure waves created in the water.
[32:09.95]These are picked by the lateral line.
[32:12.36]A form of sensory perception all fish have.
[32:23.27]Its only now from 10 meters or less that sight comes into play.
[32:28.17]In daylight, the shark's vision is as good as ours.
[32:31.31]But by night, its much more sensitive.
[32:37.68]The structure of their eye, suggests that sharks might be far sighted.
[32:41.79]They see better at distance than close up.
[32:46.36]But once they get this close, another sense kicks in. They can detect electricity.
[32:51.76]Tiny pores on the snout can register as little as half a billionth of a vault.
[33:03.91]That's the electrical field around a live fish.
[33:06.61]...Or in our test here, a metal feeding pole.
[33:17.02]In the final seconds of attack the shark goes in blind so as to protect its eyes,
[33:21.73]closing them just before it bites.
[33:25.70]That's when the last two sense, touch and taste finally come into play.
[33:34.04]Its this combination of sensory systems
[33:36.67]that makes the shark such an effective, high tech predator.
[33:47.18]You might think such sophisticated animals might dominate the seas forever.
[33:51.72]But the journey of life is never an easy ride.
[33:57.33]Several times over the millennia, meteors shattered the world order,
[34:01.26]and sparked mass extinctions.
[34:13.21]Many primitive animals were lost.
[34:15.45]Even the hardly ammonites.
[34:17.08]But in the shelter of the deep... many of their relatives survived,
[34:20.95]ready to branch out in a whole new way.
[34:28.26]The super snails rose up and colonized the shallow seas.
[34:32.53]Eventually evolving into the latest member of cephalopod dynasty:
[34:36.77]Cuttlefish, octopus and squid.
[34:46.21]Today, just once a year, millions of...
[34:48.68]...opalescent squid gather together to breed off the coast of California
[35:20.28]At just a year old,
[35:21.75]it's the last act in their short lives... once the eggs are laid, most will die.
[35:31.35]Grow fast, spawn and die young - a winning formula in the seas of life.
[35:55.41]'Cephalopod' means 'head-foot' - not a bad description really!
[36:03.25]This whopper is the Giant Pacific octopus. 5 meters long, and all head and feet.
[36:13.46]It's a gentle giant, with an alien physiology - blue blood,
[36:18.13]three hearts and an incredible nine brains!
[36:22.14]That's one big central brain plus eight mini-brains, one in each tentacle!
[36:40.62]If Cephalopods were really to compete in the seas,
[36:43.46]brainpower would be their big advantage.
[36:54.17]These are Caribbean reef squid.
[37:02.21]When a barracuda's on the scene,
[37:04.11]their best chance is to think themselves out of a tight spot.
[37:11.55]They cleverly alter their appearance to match their immediate surroundings
[37:14.79]- both in texture and color.
[37:16.56]An instant transformation, directly controlled by the brain.
[37:24.07]To the predator, it seems they've simply disappeared.
[37:52.30]The squid also communicate to tell each other when the danger's passed...
[37:57.13]they have an entire language based on skin tones.
[38:07.34]For modern cephalopods, brainpower had overcome the need for a protective shell.
[38:12.72]They're simply smarter than the average fish.
[38:16.19]So why didn't our seas become dominated by the cephalopods?
[38:20.36]But just when it looked like brain had triumphed over braun.
[38:24.16]Fish chanced upon a masterstroke.
[38:26.86]A skeleton made of a new material, bone!
[38:34.47]With it, new bony fish diversified like never before!
[39:06.34]The bony skeleton was a landmark development - one that provided structural support,
[39:11.94]greater protection, more effective gills and improved agility.
[39:22.42]Then for even more subtle maneuvers, fish evolved two sets of paired fins,
[39:28.39]joined to both sides of their body by bones.
[39:31.93]It was a winning combination and its legacy would stick.
[39:41.37]It's why we humans have a pair of arms and a pair of legs!
[39:53.35]Other bony fish, have turned to a more sedentary life.
[40:05.63]The frogfish has come up with a novel use for one of its bones.
[40:09.10]This is no wiggly worm.
[40:11.03]It's a fleshy lure, operated by a modified fin bone.
[40:22.21]But all these damsel fish see is a tempting morsel.
[40:32.29]Not only is the frogfish a master of deception, he's also perfectly camouflaged.
[40:39.73]This shrimp is unlikely to see him until he moves, and by then it's too late
[40:45.57]Because frogfish jaws move faster the muscle.
[40:56.35]How? Well, that's down to bones again.
[41:04.62]It's an elastic 'trap-jaw' that is pre-set at full tension.
[41:09.46]When triggered... the trap snaps open, increasing the mouth volume 10 times,
[41:14.06]and sucking the prey inside.
[41:24.24]Incredible, but when it comes to bone structure,
[41:27.51]these small fry are the most extreme of all.
[41:33.32]For the first two weeks of their lives, they look like any other baby fish.
[41:38.72]Then something begins to go awry...
[41:48.30]The face distorts, and one eye starts to shift,
[41:51.97]moving across to join the other on the opposite side of the head.
[41:56.31]The beginning of an extraordinary transformation.
[42:05.88]The full make over takes less than a week and the results are fixed for life.
[42:11.65]This flatfish are now perfectly adapted for life on the sea bed.
[42:16.43]Its shape and coloring mean it can keep a low profile - handy for hiding from predators
[42:22.03]or creeping up on prey!
[42:32.54]But if you don't have what it takes to make yourself invisible,
[42:35.61]your best bet is safety in numbers.
[42:42.52]Living in a shoal is a great way to minimize ones chances of being eaten.
[42:56.43]Throughout their evolutionary history,
[42:58.43]shoals of bony fish have come under fire from all sides.
[43:05.01]They've survived the age of the dinosaurs!
[43:17.35]And since a blitz of aerial attacks ever since.
[43:31.33]And all that time they've been hunted from below as well.
[44:10.31]This is predation pressure at its most extreme.
[44:13.84]Any fish that can avoid this kind of onslaught will have genes worth passing on.
[44:29.96]And pushed to the limit...
[44:31.36]...some fish eventually sought refuge out of water, with spectacular results.
[44:56.25]The flying fish - with the most extreme means of escape for any fish.
[45:08.40]Its a tactic designed to confuse any predator.
[45:15.44]Flying fish have evolved extraordinarily long pectoral fins.
[45:19.74]They don't flap, and are used to glide instead.
[45:27.58]Its the tail that does all the work,
[45:29.22]powering the fish along like an outboard motor.
[45:32.16]The fish can glide for up to 100 meters at a time.
[45:39.20]Flying fish perhaps the most extraordinary bony fish of all.
[45:44.17]It just goes to show that anything can happen in the pressure cooker...
[45:47.04]...that is the crowded seas of life
[45:54.11]And that's not the end of life's long journey through the seas.
[46:04.25]Descendants of some bony fish, eventually became the whales and dolphins.
[46:18.17]What kind of extraordinary evolutionary journey
[46:21.24]could have lead to these mammals of the sea.
[46:37.05]The first step was to leave the water altogether.
[46:57.11]By default, these fugitives have hit the jackpot.
[47:01.14]After some three and a half billion years of evolution in the oceans,
[47:05.18]it was their descendants that would go ahead and colonize the land.
[47:11.05]They evolved into all amphibians, reptiles, birds and mammals. Including us.
[47:20.63]Ultimately, some land mammals were to develop a taste for sea food.
[47:24.23]They returned to the oceans to hunt.
[47:38.41]Over time, their legs gradually turned into flippers...
[47:41.88]...and they became the most charismatic creatures of the seas.
[47:51.49]This is the bottlenose dolphin, the most wide spread dolphin in the planet.
[48:04.44]People admire, and identify more closely with this animal than any other sea creature.
[48:17.39]To swim with one is an exhilarating experience.
[48:40.94]But although we love dolphins...
[48:42.91]...perhaps we should identify more closely with the small, colder sea creatures.
[48:48.08]Because its directly down to them,
[48:50.09]and the way they evolved that we are the creatures we are.
[48:54.89]We are just a tiny part of the remarkable richness of our planet.
[48:59.03]And like all the other land animals around us,
[49:01.80]we owe our existence to three and a half billion years...
[49:05.57]...of evolution, in the spectacular seas of life.
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