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