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00:01The Earth, an epic story four and a half billion years in the making, with drama and surprise at every turn.
00:13It's the story of a tiny planet, unique in the universe, because here alone, life began.
00:21Right from the get-go, the natural world has displayed a spectacular and thrilling diversity of color, form and extraordinary behavior.
00:35It's also the story of our own journey into being.
00:42Our planet is one of oceans.
00:45It's 70% water, a blue sphere.
00:54And it was from this challenging environment that the earliest animals evolved.
01:00Even today, we are wowed by the staggering variety of our living sea.
01:16Spoiler alert.
01:19The ocean may not be where the first spark of life occurred.
01:24It's a controversy that has raged for centuries.
01:28But there's evidence to suggest that life's journey, the origin of all living things, including us, began here.
01:36Smoldering, bubbling, volcanic mud pulse.
01:46The clue comes from the fluid in the cells of all living things.
01:54Modern cells can pump out sodium to get the levels right.
01:59But the earliest cells couldn't.
02:01They must have been in a low-sodium environment, which is not the sea.
02:18So it's likely that life began here.
02:22Steam gushing from volcanic heat underground throws up mineral-rich mud, deposited as the steam condenses.
02:36Periods of drying and exposure to UV from the sun might both have played a role in enabling cells to form.
02:43This primordial laboratory finally stirred up the right ingredients under the right conditions to first spark life.
02:54A breakthrough that occurred somewhere between 4.3 and 3.8 billion years ago.
03:03Today, mud pots are hostile places for life. Strongly acidic.
03:13But back in the day, there was less oxygen in the air, which prevented the formation of sulfuric acid.
03:19It's likely that life got its jumpstart on small volcanic landmasses.
03:22It's likely that life got its jumpstart on small volcanic landmasses.
03:23And it's likely that life got its jumpstart on small volcanic landmasses.
03:24But, it's likely that life was a very similar type of soil.
03:26It's likely that life got its jumpstart on small volcanic landmasses.
03:30which prevented the formation of sulphuric acid.
03:43It's likely that life got its jumpstart on small volcanic landmasses,
03:52where rain fell and gathered in pools that were heated by geothermal activity.
04:00It was here that everything came together for us and the rest of life on Earth.
04:22Some prefer the theory of life beginning in deep-sea thermal vents.
04:30On sea or land, it's fairly certain that water and warmth were involved.
04:38But it was in the sea that the first great experiments occurred,
04:43transforming those first single cells into the spectacular diversity that is life.
04:49However, Project Life was a slow burner.
05:04The Earth was a turbulent place.
05:06Back then, the moon was closer to us.
05:11Its gravitational pull causing huge tides.
05:15And all the while, the planet was tormented by hurricanes and volcanic activity.
05:20And all the while, the planet was tormented by hurricanes and volcanic activity.
05:32But gently buffered beneath the waves, life had a chance to slowly develop.
05:50It wasn't quick, not much changed for about a billion years, but then it's thought that the first photosynthesis might have taken place.
06:08Cyanobacteria, some of the earliest life forms started photosynthesizing, and a by-product of photosynthesis is oxygen.
06:29So these early life forms released oxygen from water.
06:38Laying the foundations for the atmosphere that supports us now.
06:59Another billion years later still, complex cells, the eukaryotes, evolved.
07:13The first cells were the nucleus.
07:19A whopping 3,500 million years ago, bacteria branched out.
07:24This is the last time that all life shared a common ancestor.
07:34Fast forward another billion years.
07:40And the first multicellular life forms appear.
07:43And finally, 600 million years ago, 4 billion years after that first spark, the earliest, simple animals were swimming in the oceans.
08:08It's hard to believe that these laid the foundations for all life.
08:25But even our own family tree shares these humble beginnings.
08:41Life is a story with a slow start.
08:44But from here on in, there has been an unending arms race.
08:49With life fighting for resources.
08:51Species using innovations in evolution to outdo their peers.
08:58Competing and conquering that has led to the spectacular diversity we enjoy today.
09:07To catch a glimpse of what those early life forms looked like, we can still marvel at the micro-aliens, single-celled organisms that still drift with the plankton.
09:28Five hundred and fifty million years ago, animals were becoming more complex and recognizable.
09:41Arguably, the first of the modern groups of animals to branch off and evolve were sponges.
09:51Simple creatures without nervous, circulatory or digestive systems.
09:58Other creatures were picking up the pace.
10:09Cone jellies.
10:13To begin with, all life had to synthesize food from light and minerals.
10:18But now, there were tiny organisms.
10:23There was something larger animals could eat.
10:27Comb jellies got their name from the row of hairs, or cilia, that waft, propelling them through the water.
10:34They were among the first predators on the planet, wafting their way to engulf tiny zooplankton, which are digested by enzymes and absorbed.
10:44Though most are tiny, some sea combs can be more than a metre long and are the largest creatures to use cilia to swim.
10:57A similar level of complexity developed in another group of recognizable animals that evolved soon after, the sea anemones.
11:22From the shallow coast to 10,000 metres below the surface, sea anemones make a living by anchoring themselves to the seabed.
11:31A mouth at the top of the body is surrounded by a flower-like array of wafting petals.
11:46Tentacles armed for attack.
11:59Each is covered in nematocysts, microscopic stinging cells that work like mini harpoons, injecting paralyzing toxins into their prey.
12:10When they were starting out, prey was tiny and delicate.
12:19When they were starting out, prey was tiny and delicate.
12:29But sea anemones were armed and ready as bigger prey evolved.
12:44It was clearly a working design as the colourful creatures are still abundant 550 million years later.
12:51There were other related predators evolving that would become defining features of the ocean that we cherish today.
13:10Like sea anemones, corals are tiny predatory polyps, but these ones live in colonies.
13:35Like sea anemones, they have tiny stinging tentacles that can ensnare prey.
13:52But they also team up with photosynthesizing plankton that live inside them, enjoying the protection of the larger body.
14:03And in return, producing food from sunlight to feed the coral.
14:07Each polyp secretes a calcium carbonate shell.
14:12As the colony grows, new polyps settle over old ones, laying down their shells that gradually amass, building enormous reefs.
14:28The tiny ancient animals built structures that other species would be able to inhabit and exploit.
14:40It was not long before other major animal groups emerged.
14:59Thanks to their hard shells, echinoderms are well represented in the fossil record.
15:12Sea urchins were more mobile than their early contemporaries, using tubular feet to meander slowly across the seabed.
15:26They are mostly grazers, nibbling on algae, though will chow down on slow moving creatures given the chance.
15:39These are the armoured tanks of the ancient seas.
15:46Their bodies have a five-segment shell, which is covered with moveable spines, earning them the name urchin, or sea hedgehog.
15:54The five-fold symmetry of their shells can be seen more clearly in close cousins, much-loved, yet surprisingly predatory sea creatures that were among the first to roam.
16:21Starfish.
16:27Appearing around 450 million years ago, starfish are tiny terrors.
16:36With reinforced skin to protect their bodies, they prowl on hundreds of tiny tube feet.
16:44The little limbs are a hydraulic, powered by the pressure of the liquid within.
16:52Each of the legs has sensors and an eye spot to help guide it to food.
16:57Not quite a lion hunt on the Serengeti.
17:07The predatory ways of the starfish play out in slow motion as they creep in and smother their prey.
17:13The starfish can invert its stomach out through its mouth to secrete enzymes and digest the prey.
17:29There were other echinoderms back then that are still around today.
17:47Weird and wonderful forms like brittle stars.
17:52And sea cucumbers.
17:56But up to this point, there were no creatures with legs.
18:03The pioneers of Pedis were arthropods, meaning jointed legs.
18:20Unlike soft-bodied beasts that had gone before, these new warriors secreted bio-armour.
18:29Exoskeletons that not only protected their bodies, but were jointed and could move with them.
18:36The innovation would give rise to the most abundant species today.
18:45Insects, myriopods, arachnids and crustaceans.
18:55No one is too sure quite what the first arthropods looked like, but they quickly diversified.
19:01Trilobites were a widespread and successful group, but one that was doomed to fail.
19:12They have gone, though they looked and lived somewhat like horseshoe crabs that endure today.
19:21Later groups would innovate in new ways.
19:26By taking their first steps into a world above the waves.
19:29But in the oceans, another group was to rise to fame.
19:40The crustaceans.
19:44More than 500 million years ago, there were already shrimp-like creatures.
19:49And they were soon to radiate and grow.
19:51A glimpse of those early ancestors can be found in the freshwater ponds of Europe and the Middle East.
20:03Treeops, or tadpole shrimps, are often considered living fossils, unchanged since the Triassic period, the dawn of the dinosaurs, some 240 million years ago.
20:16The tiny creatures are tough.
20:20Their eggs can weather droughts and temperature extremes, ideal for the volatile world in which they evolved.
20:27These early shrimps were fast-tracked to success.
20:40Crustaceans were really upping the game in terms of being dynamic, complex, active and mobile animals.
20:41Crustaceans were really upping the game in terms of being dynamic, complex, active and mobile animals.
20:58They breed sexually and release millions of eggs into the water that mature in the plankton.
21:19As they grow, they shed their skins until large and heavily armoured.
21:32Ever adaptable, they can be passive filter feeders, grazers, scavengers and predators, occupying most of the available niches of their time.
21:45There was another group emerging beside them, also experimenting with armour, but in a different way.
22:04Mollusks, the shellfish, mussels, clams, slugs and snails.
22:17The first blueprints developed by this group included the slimy foot with mussels pulsing, allowing it to slide along and a unique rasping tongue.
22:33The muscular soft bodies of these creatures were vulnerable to the ever-growing number of predators.
22:49And so they secreted calcium carbonate shells, often preserved in the fossil record and among nature's most beautiful artworks.
23:04The shells can be single structures, carried aloft as a mobile home while their owners browse, typical for the huge variety of snails.
23:13Or might be in two parts and hinged, like in clams and mussels, providing complete protection when danger looms.
23:33Because mollusks evolved early and made hard shells, they are well represented in the fossil record and have made a useful tool for geologists to age rocks and chart the history of life on Earth.
23:58They dominated ancient seas and today remain one of the most diverse groups of animals, with nearly 100,000 species described.
24:19Most are algae munchers or plankton filterers.
24:22But not these.
24:45After sensing a washed up jellyfish, these plough snails stormed the beach.
24:49Using their large feet to ride the waves,
25:14They can probe and suck up.
25:43of the porps.
26:08Shellfish are not the most dynamic animals,
26:11taking their time to get around.
26:13But there's another ancient branch of the mollusk family
26:17to perform a radical gear change.
26:27They started out as shelled crawlers of the sea floor,
26:30but gradually left it behind.
26:34Shelled squid, like ammonites and belemnites,
26:38dominated ancient seas.
26:40They lasted for hundreds of millions of years,
26:44but vanished during the extinction
26:47that finished off the dinosaurs.
26:50However, their cousins survived.
26:54Squid and cuttlefish lost their external shells.
26:58Instead, they have a stiff rod inside to support their bodies.
27:05Today, their size ranges from B to bus.
27:09The cephalopods are the most complex and intelligent of all invertebrates today.
27:25They were the first truly fast and dynamic predators in the ocean,
27:34capable of hunting down any of their contemporaries.
27:38But things were to change with another vital branch of the family tree.
27:50The chordates had arrived.
27:51At first, they didn't look very impressive.
27:52They were still simple creatures, like these sea squirts.
27:53But these are our ancestors.
27:54The first step of the ladder towards the river.
27:56They were still simple creatures, like these sea squirts.
27:58But these are our ancestors.
27:59The first step of the ladder towards the rise of the vertebrates.
28:00The first step of the ladder towards the rise of the vertebrates.
28:29Though simple and sessile, just siphoning water to bring in nutrients to take out waste,
28:35their juveniles are mobile and, crucially, contain a notochord,
28:41the beginnings of a spine and a sign of things to come.
28:52Chordates first appeared during a time known as the Cambrian Explosion,
28:57and it was aptly named, because 541 million years ago,
29:02the world suddenly saw a huge increase in the diversity of life.
29:13No one is certain what triggered this boom in evolution.
29:18The oxygen levels had increased dramatically,
29:21thanks to the first plants that were slowly colonizing the land.
29:25The atmosphere was more complete.
29:31But also, as the range of organisms increased,
29:34so did the competition between them.
29:37And as the predator-prey relationship grew more complex,
29:42an arms race got underway.
29:51A pressure that can promote evolutionary innovation.
29:54And the next big leap.
30:08A spinal cord.
30:09A spinal cord.
30:13This is where our own family tree branched off,
30:16leaving behind all the crustaceans, mollusks and other creatures that had come before.
30:23And it all happened in the ocean.
30:25The first backboned animals were jawless fish, like the bizarre hagfish.
30:36Like all of the complex creatures that had gone before them,
30:40these animals breathed through gills.
30:42But these jawless fish were quickly followed by two other groups that were to go on to dominate the seas.
30:56The world was entering a period of geological time known as the Devonian,
31:15the age of fish.
31:16By 419 million years ago, the jawless fish had given rise to three new families.
31:38Placoderms were a hugely successful but short-lived group of armoured fish that became giant.
31:51But were lost to the fossil record.
31:53The other two groups remain extremely abundant and familiar.
32:13The biggest group of vertebrates, our branch of the animal kingdom,
32:18are the osteichthys, the bony fish.
32:22And this is when they came into being,
32:25the first of the true vertebrates.
32:34As their name suggests, they are defined as having a skeleton
32:39that is more bone than cartilage.
32:51They also have paired fins and gill arches.
32:56They have jaws and are covered in scales.
33:02It's thought bony fish may have evolved in fresh water.
33:12Early species might have resembled modern lungfish.
33:14And like lungfish, they had primitive lungs, adaptations to cope in environments where water levels fluctuated,
33:25so that they were capable of gulping air.
33:28they were able to get rid of them.
33:29Most fish no longer have lungs.
33:41But the primitive ancestral lungs became something just as important.
33:46A swim bladder, a sack into which the fish can vary the pressure of gases to aid its buoyancy.
33:58It means that at any depth, the fish can control its buoyancy without wasting energy.
34:06Located in the upper part of the fish, it also helps to keep the body the right way up.
34:16From the Devonian, the fish have gone through endless changes and spectacular diversification.
34:39Evolution has driven succession of fish design.
34:49New advantages giving some kinds the edge over their ancestors
34:54and enabling them to out-compete and replace them.
34:57Thanks to the endless variation and drive to find and conquer new niches,
35:11there are currently 23,000 species of fish in glorious diversity
35:17which have conquered pretty much every aquatic habitat on Earth.
35:20From rivers and lakes, to tropical reefs and polar ice caps.
35:31They can range from small fry, just a few millimeters long,
35:38to truly giant, like the bizarre ocean sunfish,
35:43the heaviest of all, weighing as much as a rhino.
35:46One of the most derived forms, with no tail, just a little pulsing ribbon,
35:59and huge fins above and below, spanning four meters across.
36:10Amazingly, the giant fish sustained themselves mostly on jellyfish.
36:14Somehow, they are still able to bulk up on this low-calorie diet,
36:22going from microscopic hatchlings to ocean giants in just a few years.
36:33Fish can occupy every trophic level, meaning every stage of the food chain,
36:38from grazing on seaweed and algae, to being dynamic hunters or scavengers of the dead.
36:48While they became some of the most abundant, dominant creatures in the sea,
36:54they were not the only group of fish to rise to fame.
36:56The chondrichthys, the sharks and rays, are defined by a cartilage skeleton.
37:13But how and why remain something of an enigma?
37:16It was always thought that the chondrichthys must have branched off before early fish developed bone skeletons.
37:25But new research and the discovery of a fossil has turned this on its head.
37:32It shows that 400 million years ago, vertebrates, fish with bony skeletons, were well established.
37:46But that one group lost the ability to produce bone using lightweight, flexible cartilage instead.
37:52They established blueprints that were to go unchanged and unchallenged as some of the planet's most successful animals.
38:17Some remain bizarrely primitive in their appearance.
38:20Chimeras branched off about 400 million years ago, becoming widespread and abundant.
38:28The ancient creatures were complex and highly evolved.
38:33At this time, plants were only just appearing on Earth.
38:37Chimeras were leagues ahead.
38:40The odd ocean dwellers are sometimes called ratfish for their tapered tails and goofy faces.
38:47Their faux rodent beady eyes seem to glow green but are adaptations to hunting in the dark.
38:56With jaws fused to their skulls and with permanent tooth plates for grinding food, they are distinct from their cousins.
39:04Gates and rays are the relatives that look like they have been run over.
39:10But as is characteristic for their clan, they use electro-receptors.
39:15Little jelly-filled pores on their heads to sense the movements of prey.
39:19With eyes above to watch out the danger, they are dependent on the sensory organs on the lower part of their face to home in.
39:33Rays' fins are enlarged and flattened, wings to help them glide through the water.
39:44The graceful giants seem benign compared to their dynamic kin.
39:49The most famous masters of the ocean.
40:07The sharks.
40:09The stream-lined, torpedo-shaped fish are also guided by electro-receptors.
40:22Not only to sense prey, but perhaps also detecting currents, temperature changes and even the Earth's magnetic fields.
40:33Allowing ocean wanderers to travel over huge distances.
40:52Sharks have been on Earth longer than trees have.
40:56First emerging 450 million years ago.
40:59There are some species still living today that are unchanged from fossilized animals that swam the oceans 200 million years ago.
41:22Since they first appeared, there have been five mass extinctions.
41:26Each of which devastated life on Earth.
41:29Each of which devastated life on Earth.
41:38Including the one that wiped out the dinosaurs.
41:40And yet, sharks endured.
41:41And yet, sharks endured.
41:42And yet, sharks endured.
41:43And yet, sharks endured.
41:44And yet, sharks endured.
41:45And yet, sharks endured.
42:12Today, they are top predators in the ocean.
42:15More than 400 species roam, from the smallest that could fit in a pencil case to the biggest,
42:28longer than a bus.
42:33The whale shark is the biggest fish on earth, 14 tons of power, and yet feeding on the smallest
42:40creatures in the sea.
42:42Like the equally daunting basking shark, it sustains its colossal bulk by sifting plankton
42:55from the sea.
42:59These giant filter feeders first appeared in the Cretaceous period.
43:03But it was before that, during the Jurassic, the age of the dinosaurs, that sharks really
43:09made leaps in evolution that we'd recognize today.
43:15Unlike most bony fish, sharks retain the tail shape that is asymmetrical, with the upper
43:21lobe much longer than the lower one.
43:28The prey isn't well known.
43:30But the design may help sharks in an energy-efficient horizontal glide.
43:41Their jaws became more flexible, so they could be pushed forwards to stab in and rake their
43:47serrated teeth into their prey.
43:52Their teeth are like steak knives to slice through muscle fiber.
44:04Unlike bony fish, they don't have a swim bladder to help regulate their buoyancy.
44:10They might be aided by their lightweight cartilage skeletons.
44:18To compensate, they have huge livers filled with oil called squalene.
44:27The giant organs can make up 30% of their mass.
44:38A basking shark's liver can weigh a ton.
44:48As they moved into new territories, new traits evolved, some truly spectacular.
45:07As they move into new territories, they can make up 30% of their species.
45:20Though sharks are all immediately recognizable, and have been for millions of years, their form
45:26supports some truly weird variations.
45:28Like that of the youngest member of the family, hammerheads first appeared a mere 20 million
45:44years ago, making them the babies of the family.
45:50Why they have their extraordinary heads isn't clear.
45:54It might be to spread their electroreceptors to help them hunt or navigate.
46:00The recent research suggests that it is to give them binocular vision.
46:08With their eyes on stalks, they can see through 360 degrees.
46:22All sharks and rays are united by rough skin.
46:29It's covered in tooth-like scales called denticles.
46:33It helps to create a foil, reducing drag as the shark glides through the water.
46:43And of course, sharks have their famous dentition.
46:50To make sure they always have a mouthful of sharp teeth, sharks constantly shed old teeth, replaced
46:56by new ones.
47:10A single shark can get through 35,000 teeth in a lifetime.
47:18Sharks have a winning formula.
47:19They have been around longer than most animals, and have nearly half a billion years of experience
47:24under their belt.
47:29So, for more than four million years, the fish have dominated the seas.
47:59Becoming some of the most beautiful and diverse forms of life.
48:13Fish have been long assumed to be cold-blooded creatures, and most are.
48:18But some of the larger species have blurred the boundaries between warm and cold-blooded animals.
48:28Giants like sharks and the powerful and dynamic tuna have massive muscles that generate heat
48:35while they work.
48:37And their huge bodies retain the warmth, making them considerably warmer than their surroundings,
48:47adding to their power and speed.
48:56With the evolution of these impressive beasts, life in the seas was really hotting up.
49:06Even warmer-bodied, even warmer-bodied, was to come.
49:17That's a different story.
49:24There is an interesting lesson to learn about the origins of life in the sea.
49:36It was always assumed that evolution was driven by competition, species out-competing their predecessors.
49:49But the latest research suggests that those elements that combined to create living cells were not competing, but collaborating.
50:02Perhaps we should no longer think about evolution as competing, but sharing innovation.
50:08It might suggest that our own future on the planet is dependent on collaborating with, rather than dominating the other creatures that share this planet.
50:23Rewind back another 300 million years, and there was another innovative step being taken by a group of fish.
50:41Perhaps a small step for fish, but a giant leap for life, and another stride towards our own place on the planet.
50:55It was to be the start of the new chapter of life on Earth.
51:11What kind of bird-like видимings?
51:13It might be the first step for theids of the earth.
51:14Look, have a little underwater there.
51:16But there are other rapid fields there.
51:18And there's a few signs that we find in in the future of the planet's land.
51:20What are you looking for, what are you looking for?
51:21How are you looking for?
51:26Do you want for a chance of a dead diamond?
51:28Have a chance of a dead diamond?
51:31What's going to be the last of the fryer?
51:33Why don't you think?
51:34What are you looking for?
51:35What are you looking for?
51:36A dead diamond?
51:37Having a dead diamond?
51:38How can I see that?
51:40Transcription by CastingWords