- 6 hours ago
The evolution of the horse spans approximately 50 million years, tracking a gradual transformation from small, forest-dwelling browsers into the large, single-toed plains grazers of today.
马的演化史是一部跨越5000多万年、从森林走向开阔草原的生命适应史。它的演化并非简单的线性升级，而是一条枝繁叶茂的“演化树”。马的演化本质上是为了适应环境变迁和提高奔跑速度，其核心变化集中在三个方面 :--
• 体型变大：从最初狐狸或小狗般大小，逐渐演变成如今的高大体型。
• 脚趾演化（单蹄化）：前足从最初的4趾、后足3趾（如始祖马），演变为中趾逐渐粗壮并最终独占承重，演化出坚硬的单蹄，以适应在开阔草原上的高速奔跑。
• 牙齿演化（高冠齿）：为适应从摄食柔软的森林树叶（低冠齿）转变为啃食粗硬的草原草本植物（高冠齿），牙齿变得更高、更耐磨。
马的演化史是一部跨越5000多万年、从森林走向开阔草原的生命适应史。它的演化并非简单的线性升级，而是一条枝繁叶茂的“演化树”。马的演化本质上是为了适应环境变迁和提高奔跑速度，其核心变化集中在三个方面 :--
• 体型变大：从最初狐狸或小狗般大小，逐渐演变成如今的高大体型。
• 脚趾演化（单蹄化）：前足从最初的4趾、后足3趾（如始祖马），演变为中趾逐渐粗壮并最终独占承重，演化出坚硬的单蹄，以适应在开阔草原上的高速奔跑。
• 牙齿演化（高冠齿）：为适应从摄食柔软的森林树叶（低冠齿）转变为啃食粗硬的草原草本植物（高冠齿），牙齿变得更高、更耐磨。
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TVTranscript
00:08Pegasus, Bucephalus, Champion, Trigger, Seabiscuit, Red Rum.
00:17I'm talking about the stuff of myth and legend.
00:30And just look at her. She's absolutely gorgeous, aren't you?
00:39Equus Ferus Caballus, the horse to you and I.
00:45A statuesque pinnacle of natural art.
00:53This is a creature supremely shaped to move.
01:17Thanks to 700 mighty muscles.
01:22And a heart the size of a football.
01:29The horse is one of the fastest and most powerful animals on the planet.
01:41They don't call it horse power for nothing.
01:47So how did the horse become one of nature's greatest athletes?
01:58To answer that, we must travel back in time.
02:10To meet the key movers and shakers.
02:13Before hooves thundered.
02:21Or hearts raced.
02:26Back to a time when almost nothing at all moved.
02:57The story of the horse.
03:00And in fact, the story of movement.
03:03The story of movement.
03:03Can be traced incredibly.
03:06Right to our own doorstep.
03:11This is a quintessential English landscape.
03:15A rural Idle of rolling hills and ancient woodlands.
03:23But I've got to tell you that if I was standing here just over half a billion years ago, the
03:28view would have been very different.
03:30In fact, I wouldn't have been standing.
03:31I'd have been submerged deep beneath the waves on the ocean floor.
03:35And over millions of years, these rocks have been pushed up and laid bare.
03:41And they tell us of the history of that time.
03:44A history written in sand and silt.
03:46A history with some fascinating clues.
03:54Hiding in plain sight are some of the most precious fossils on the planet.
04:03But millions of years of weathering have warped these rocks, making them very hard to spot.
04:12Now I did tell you they were tricky to see, but there is one right in front of me here.
04:18Just follow my fingers.
04:20It starts up here.
04:22Then it arches down.
04:24You can see the ridges in the rock, particularly visible here.
04:29And then it comes up towards my shoulder.
04:31And this bit follows right up past my ear.
04:35These would have been made by fronds.
04:37And they would have been attached around a centre point, which could have been somewhere here.
04:42This is a fossil of Brigatia.
04:45And I know it doesn't look like much.
04:47It might look like an old cabbage that's been pressed in the rock to you.
04:50But it wasn't an old cabbage.
04:52It wasn't a plant at all.
04:53And this is a very, very important fossil.
04:57Because it's a fossil of one of the earliest animals that ever lived on Earth.
05:07Over half a billion years ago, this slab of rock was home to some of the very first animals.
05:25Theirs is a peaceful life.
05:35But this strange community does have a problem.
05:43When animals with large, complex bodies first evolved, they couldn't move.
05:51We call them sessile.
05:57Rooted to the ground, they must rely on the ocean to bring them what they need.
06:05And they're powerless if it doesn't.
06:12Animal life could have remained stuck in this way forever, if it wasn't for an evolutionary maverick.
06:24This is a cast of a fossil that's about 565 million years old,
06:30which means it formed around the same time as Brigatia.
06:33Now, when the scientists first looked at it, they were initially confused.
06:36It's quite difficult to see.
06:37Look, it starts up here and it runs down here.
06:41It's almost as if someone has been running their fingertip over some soft mud.
06:47And then it terminates down here.
06:49But if you look here, you can see there are a few little half-moon shapes.
06:55Now, the reason those scientists were initially confused
06:57is they were probably looking for a fossil of an animal.
07:00But this is not that.
07:02What it is, is a fossil of something an animal left behind.
07:10Now, we think the story goes something like this.
07:15In amongst the creatures stuck to the seabed is a tiny animal,
07:20little more than a gelatinous blob.
07:25Like other animals here, it eats specks of food that drift on the ocean currents.
07:32But today, the current has shifted
07:37and is now carrying the meagre morsels just out of reach.
07:45Deprived of food, the only option for this stationary population
07:50is to sit and wait for their luck and the currents to change.
07:57But this animal is a pioneer.
08:06You see, this little blob can do something that the other animals can't.
08:25abandon the safety of its home
08:28and move.
08:30move.
08:39With every heave,
08:42it leaves a mark.
08:47Some of the earliest animal tracks on the planet.
09:02one small step for this tiny blob,
09:06one giant leap for animal kind.
09:18Now, we'll never know exactly when the first step was taken.
09:22We can presume that there were some missteps,
09:25evolutionary stumbles, if you like.
09:28But that leap between being sessile and motile was a profound one.
09:36Today,
09:41whether they're finding food,
09:45mates,
09:47or shelter,
09:50our planet is an extravaganza
09:54of motion.
09:57an estimated 97% of animals moving in weird and wonderful ways.
10:06And none of this would be possible
10:09without one key ingredient.
10:19muscle.
10:25To understand just how powerful muscle can be,
10:29we need a demonstration from an expert.
10:33I give you
10:35the leech.
10:39I know,
10:40not everyone's favourite animal,
10:42but it won't surprise you to know
10:44that I'm rather a fan of the leech.
10:48What are they?
10:49Well, they're a type of worm
10:51and there are about 700 species in the world.
10:55Many like this one are parasitic.
10:58This is a medicinal leech
10:59and it's been used by medical practitioners
11:02to suck the blood from humans
11:04for three and a half thousand years.
11:07But I digress.
11:08What about its movement?
11:11Well, let's take a look at their body.
11:14First thing you'll notice, no legs.
11:16Its body is made up almost entirely of muscles.
11:26Muscles are built from tiny cells called myocytes.
11:33We sometimes call them muscle fibres.
11:38Within the leech, there are thousands.
11:41While an animal like the horse contains millions and millions of them.
11:48They work thanks to their superpower.
11:53Their ability to contract.
11:58Now this leech's muscle cells are arranged in opposing sets.
12:03There are circular muscles that run around its body
12:06and longitudinal muscles which run from one end to the other.
12:10So how exactly does it move?
12:12Well, I'll try and demonstrate that here.
12:14Come on.
12:20It stretches forward using those circular muscles
12:25and then contracts its longitudinal muscles
12:29and pulls itself forward.
12:32So that it can slowly inch across the palm of my hand
12:37and down my fingers.
12:40Something that I find quite therapeutic.
12:46You may consider it perverse, but I'm rather enjoying this.
12:58Today, it's easy to take muscles for granted.
13:02But half a billion years ago,
13:06it was primitive muscle cells
13:08that turned contraction into action.
13:14Allowing pioneering animals
13:16to take a leap into the unknown.
13:25And the importance of this simply can't be underestimated.
13:30Because from this point on,
13:32movement will become one of the most powerful driving forces
13:37in animal evolution.
13:40To reach the next step in the story of the horse,
13:44we must hit fast forward.
13:49For the next 40 million years,
13:52evolution gallops on.
14:04Muscles stretch and shape animal life.
14:09And more and more time is spent...
14:15..on the go.
14:34They say, necessity is the mother of invention.
14:39And that was certainly the case
14:41for animals experimenting with early locomotion.
14:48Down here, every trip across the sea floor demands energy.
14:54And lots of it.
15:00And to get from A to B,
15:02it's thought that ancestors of the horse
15:05had evolved to use muscle in a totally new way.
15:10Incredibly, evidence of this can still be seen today.
15:16Inside this little plastic tub here,
15:20I have a beautiful animal.
15:25It's called a sea squirt, or a tunicate.
15:28And it's a chordate, which means we're actually related to this.
15:32I know it's difficult to believe, but it's true.
15:35And the benefit of looking at this particular species
15:38is that it's transparent.
15:40I can see inside it.
15:42And I can see a tube running around its body.
15:46And that tube is filled full of oxygen, minerals and sugar.
15:53It's its blood.
15:55And that tube is contracting.
16:00Waves of muscle contraction are pushing that blood around the body.
16:07Fundamentally, this is a simple heart.
16:12It's thought that systems like this
16:15allowed this ancestor of the horse
16:17to enjoy an active lifestyle.
16:30Just like the rest of its kind,
16:33nutrient-rich blood is being pumped through its body,
16:37making its muscles fizz with energy.
16:44Now, most of these creatures wouldn't win any races,
16:49spending their energy just wriggling along the seabed.
16:53But the ancestor of the horse
16:55seems to have had an extra boost.
17:01Meaning...
17:06It can swim harder.
17:09Better.
17:10Faster.
17:12Stronger.
17:17Stronger.
17:19Stronger.
17:35Stronger.
17:39Stronger.
17:40This remarkable athletic ability is thanks to an innovative use of muscle that unlocked
17:46the full potential of the heart.
17:58At this point evolution all starts to go a bit Frankenstein.
18:02You see for any muscle to contract it requires a stimulus, an order, and that typically comes
18:08in the form of a tiny electric zap.
18:13And it's thought that some muscle cells inside some of the earliest hearts took charge, specialised,
18:19and started to send out a series of rhythmic zaps.
18:25And all of the surrounding muscle cells complied by contracting, generating a single powerful
18:31pulse.
18:35Now, these mutant zapping cells are called pacemakers and almost all animals have them.
18:41We have a single primary pacemaker called the sinoatrial node.
18:46And as soon as those ancient pacemakers began to pulse, they instigated a revolution.
18:57In the ancestor of the horse, those specialised pacemaker cells have now clustered together
19:05in a localised region, giving its heart a more powerful beat.
19:19And over many generations, the beat gets stronger.
19:29The muscle walls around the pacemaker thicken, chambers form and valves, directing blood flow around the body, becoming an iconic
19:53life-sustaining organ.
19:57It's an ingenious use of muscle, one that transformed animal locomotion.
20:07When hearts went from being a simple pump to a more complex muscular mechanism, it led to a step
20:14change in the evolution of movement.
20:16It allowed animals to become bigger, stronger, faster.
20:21It allowed them to get off of that seabed into the world above.
20:24And from that point on, life would become a slithering, crawling, walking, running, jumping and climbing adventure.
20:38Today, across the globe, beating hearts are pumping oxygen through all sorts of bodies.
20:48Around two and a half billion heartbeats will supply your muscles with the energy they need from your first breath
20:58till your last.
21:04It's a rhythm that connects us all to the first beats over half a billion years ago.
21:18Time to take a leap forward as the descendants of those early swimmers get bigger, stronger and faster.
21:29They shapeshift through countless iterations until 140 million years later, they have become fish.
21:50This is an ocean full of powerful bodies.
21:56But here, it's not how many muscles you've got that counts.
22:02It's how you use them.
22:07Now, there are many forces shaping evolution.
22:13The need to find food, the need to find mates.
22:18But there are even greater forces at play.
22:22Those forces which shape the entire universe.
22:24I'm talking about the laws of physics.
22:28And when it comes to locomotion, harnessing these would be key.
22:33And fish have achieved that with a remarkable innovation.
22:37Something that's startling in its simplicity, but significant in its importance.
22:48Something that today has helped make fish the success story of our oceans.
22:57Attached to their streamlined bodies, structures of flesh, cartilage and bone have evolved.
23:06Tools which their muscles can control.
23:10Expanding the mechanics of movement available to them.
23:18They can be gliders, thrusters, rudders.
23:24I'm talking about fins.
23:34And 380 million years ago, the ancestor of the horse was a fish with fins like this.
23:45You can see the fin here.
23:48But look at the base.
23:50It's made up of a series of robust, strong bones which anchor it to the body.
23:56And they would have been covered with powerful muscles.
23:59And it's this stalk, or lobe, which gives this group of fishes their name.
24:04We call them the lobe-finned fishes.
24:07Now, I've got to be honest with you.
24:09In the open ocean, this setup probably didn't confer them with much of a competitive advantage.
24:15But under certain circumstances, they proved to be a real bonus.
24:29This is Onycodus.
24:33An ancient predator as big as a crocodile.
24:39With muscular, lobed fins.
24:46Now, its size and weight should be an advantage.
24:50Making Onycodus a formidable foe.
24:55But when it swims...
24:59The water around it is churned up.
25:03Giving the game away.
25:10So how does this ocean giant catch its dinner?
25:20The answer lies in those lobed fins.
25:24Inside there is a tool that's just begging to be used.
25:27A tool with enormous potential.
25:29I'm talking about a lever.
25:37You see, the relatively small distance travelled by my hand and arm here
25:42is magnified out there at the tip of the oar, which is moving far further.
25:56When it comes to generating movement, muscles are fantastic.
26:01But they do have their limitations.
26:05The lever is life's great multiplier.
26:16Look, small amount of force applied by my arms in the boat
26:21is transferred to the tip of those oars
26:24and it allows me to propel the boat forward.
26:29Not exactly with Olympic prowess, I have to confess,
26:32but with a degree of efficiency.
26:41And it's thought this same principle helped this hulking fish
26:45to move with incredible delicacy.
26:50By doing something very unfishlike.
26:58Using four of its lobed fins, along with the physics of levers,
27:05Onycodus turns minimum effort into maximum movement
27:09and propels itself stealthily across the sea floor.
27:29Swapping swimming for walking,
27:32it saves its energy for one final powerful thrust.
27:47Thanks to its four lobed fins,
27:51Onycodus is a master of the ambush.
28:00So, with skills like these,
28:02you'd expect there to be plenty of lobed-finned fish in the sea.
28:07But today, they have almost entirely vanished from our waters.
28:19My goodness.
28:22That was a bit of a workout.
28:25Now look, levers are very useful in water,
28:28but they could become even more useful somewhere else.
28:36When fish like Onycodus begin to use their lobed fins to walk,
28:41rather than swim,
28:42they set off a chain reaction.
28:52Over millions of years,
28:56the thick bridge of bones inside those four fins lengthen.
29:03And the muscles surrounding them shift and alter,
29:09creating strong, tough appendages.
29:14No longer fins at all.
29:19But four levered limbs.
29:23This was the birth of the tetrapods.
29:30And today, there are more than 30,000 species,
29:36inhabiting every continent.
29:45A diverse supergroup,
29:48all descendants of those fish with four lobed fins,
29:52are now putting them to use in very different ways.
29:58Including the horse.
30:07For many tetrapods today, moving on land is second nature.
30:12But for their ancestors crawling out of the sea,
30:17it was a very different story.
30:22Moving from one ecosystem to another,
30:25which is completely different,
30:27requires a painfully slow process of adaptation.
30:32But the creatures that were making that transition
30:35looked a little bit like this.
30:42Oh, yes.
30:46Look at that.
30:48That's special.
30:50One of nature's jewels.
30:53Absolutely beautiful.
30:55This is a marbled newt.
30:59You can see how it got its name
31:00with that marbling running down its back there.
31:05It's an amphibia.
31:07It spends its spring in ponds,
31:09going through its breeding cycle,
31:11and then at the end of summer,
31:12it emerges onto land where it spends the rest of the year.
31:15But of course,
31:17it's gone through millions of years of evolution,
31:20which allow it to exploit the best of both worlds,
31:23the wet and the dry.
31:26But what about its movement?
31:28Well, in the ponds,
31:29it's a fairly good swimmer, to be fair.
31:31What about on loud?
31:33Let's give it a go.
31:44They're tentative.
31:45They're slow.
31:47They're laborious.
31:48They're calculated.
31:49Their little bodies bending from side to side
31:51as they rather lethargically move through the environment.
31:57I've never seen a newt galloping or frolicking.
32:00I'm never going to.
32:01But this does tell us something very important.
32:07Movement on land is hard.
32:10Very hard.
32:18This newt can get away with having four left feet,
32:23because in a pinch,
32:25it can retreat to a habitat it finds easier to negotiate.
32:37But 350 million years ago,
32:41if the ancestors of the horse were to pursue a life solely on solid ground,
32:47they would need to be far more coordinated.
32:49And the answer to their coordination conundrum came once again with an evolutionary innovation from the ever-adaptable muscle.
33:01Inside almost every muscle in my body, I have something called a stretch sensor.
33:09And stretch sensors are highly specialized muscle fibers that are constantly monitoring how and when those muscles are moving.
33:19The key thing is that they are all linked together in a complex web,
33:24so each individual muscle knows exactly when every other muscle is moving.
33:32Now, despite the fact that this is an incredibly complicated system,
33:36I bet that you've never even thought about it.
33:39And that's because you don't have to, despite the fact that it's crucial for every single move that we make.
33:55Tiny stretch sensors allow the muscles to communicate with the central nervous system,
34:01giving us and most living tetrapods the ability to coordinate movement with astonishing precision,
34:09often faster than you can think.
34:19Look at that.
34:27Just look at the legs there.
34:29Every part of them is moving independently in isolation at the same time.
34:36And then the weight, that's got to be balanced between all four feet.
34:42And running down those legs, just going to speed it up.
34:45Look at that.
34:47Our ripples of muscles.
34:50That's the glutes, that's the quads, that's the hamstrings, all working in unison.
34:59Without these little gizmos, these stretch sensors hiding in muscles and the complex network that joins them all together,
35:07animals with bodies like this simply would not have been able to evolve.
35:15It was down to this innovation that animal bodies could become radically more coordinated.
35:21And those tiny little bones, once hidden in those fish's fins, could really come into their own.
35:29Those fully terrestrial animals could put one foot in front of the other with extreme precision.
35:39And this was a game changer.
35:47Time for us to motor on.
35:53Time for us to force.
35:53Over the next 300 million years, the tetrapods scattered across the earth.
36:04While life faced some cosmic curve balls, it was never fully derailed.
36:13and evolution carried on
36:18and tumbling us
36:24into a new world
36:30where the way you move
36:33can be a matter of life
36:36and death.
36:43This is Phanacodus.
36:53Life looks pretty serene
36:56but Phanacodus
36:58must constantly be on guard
37:02because this world is full of expert movers
37:07whose bodies
37:11have evolved for the chase.
37:17When the hunt is on
37:19surging adrenaline, thumping hearts
37:23and straining muscles
37:24will only take you so far.
37:30Faced with a situation it can't muscle its way out of,
37:36the secret to Phanacodus' survival
37:39lies in its feet.
37:47Come on Siddy, Nance, come on.
37:56Do you know sometimes people say
37:59why poodles?
38:00Why poodles, they say?
38:02And I facetiously reply
38:03are there other breeds of dog?
38:05I mean, look at them.
38:06Boundless energy, incredibly loyal
38:09and they can also help us
38:11with an important part of our story.
38:14You see, hidden beneath this curly fur here
38:17is a crucial step change in evolution.
38:21Now I don't need to tell you about my foot and leg.
38:24You've got your own.
38:25Starts off at the toe,
38:26goes across the foot to the ankle
38:28then you've got the shin, the knee, the thigh.
38:32We put our feet down onto the ground.
38:34We plant them flat on the ground like that.
38:38We're what we call planter grade animals.
38:40It's quite an efficient way of walking.
38:43Nancy, on the other hand, is altogether different.
38:46Let's take a look at her back leg here.
38:48You see, her toes stretch from here to here.
38:52The rest of her foot bones all the way up to here
38:55which looks like a backward pointing knee.
38:58This is in fact her ankle.
39:00Her knee is all the way up here.
39:03So Nancy is effectively standing up on her toe bones.
39:10She's a digital grade animal.
39:13And that's altogether different.
39:15It means that you move in a very different way, doesn't it?
39:18Should we show them?
39:19Come on, let's go.
39:21Come on.
39:30Right, Sid, Nancy.
39:33Let's see them in action.
39:44Look at them go.
39:45You see, this change in anatomy allows the leg to become longer,
39:50the stride to become longer,
39:52and more efficient use of all of that elastic energy
39:55stored in the muscles and tendons above their ankle.
40:00Look at that, bouncing about.
40:05Alacrity, agility, critically speed.
40:10That is a happy poodle.
40:14And you know, this adaptation has occurred a number of times
40:17in terrestrial animals.
40:19But having said that,
40:20if you really want to be a creature,
40:22living life in the fast lane,
40:25evolution can offer you one more gear.
40:29Sidney Nance, come on.
40:31Come on.
40:33When it comes to speed and efficiency,
40:37Plantagrade, that's us,
40:39will get you from A to B.
40:42Digitagrade, like my dogs,
40:44ups the revs.
40:47But 56 million years ago,
40:51Phernacidus was on the verge of something new.
40:55Not just bouncing on the balls of its feet,
40:59but pushing off from the very tips of its toes.
41:08Lengthening its stride even further.
41:12So future generations take the concept
41:15and run with it.
41:22As bones elongate and muscles bulk up,
41:27they spend more and more time on tiptoe.
41:35And in the process,
41:37find the most efficiency in trading many toes
41:42for one large, powerful shock absorber.
41:52Look at this.
41:54This is clearly a cast of a fossil of a hoof.
41:59A hoof at the end of a very long leg.
42:03A leg that's clearly all about movement.
42:07A leg, though, that is surprisingly different than ours.
42:11You see, essentially, its foot all the way from here to here.
42:15This is the equivalent of our ankle.
42:18The bone here would be like those in the sole of our foot.
42:20And down here, it's balancing on a single tiptoe.
42:25The hoof itself would have been made of keratin,
42:29just like our fingernail.
42:31And also what's interesting is at the other end,
42:33the front legs weren't attached to the skeleton.
42:36They were embedded in a heavy mass of powerful muscle.
42:40And this gave it the capacity for a greater stride.
42:44And you see this groove here.
42:47Running down here would have been a tendon,
42:49perhaps half a metre long,
42:51a giant elastic band.
42:54But it is a leg with compromises.
42:57I mean, you can't pick anything up with a hoof.
43:00You can't manipulate anything.
43:01It's lost all dexterity at the expense of speed.
43:08This three-million-year-old hoof
43:12tells us of the arrival of a new group of animals.
43:18Animals we call Equus.
43:34These single-hoofed mammals first evolved on the plains of North America,
43:41before spreading across the globe.
43:46Among them was one remarkable species.
43:54Equus ferrus.
43:59Known to you and I as the horse.
44:10Its body shaped generation after generation
44:14by the evolutionary drive to move.
44:25700 mussels,
44:27passed down over half a billion years
44:30from a pioneer who changed the world.
44:33A huge heart with an ancient beat
44:37that began deep beneath the waves.
44:40Long, levered limbs
44:43that once helped a fish to walk.
44:47And four large hooves.
44:50The legacy of ancestors who had to run for their lives.
44:57But there's one final twist in the story of the horse.
45:03Because Equus ferrus was about to encounter
45:07a new force of evolution.
45:16Another species on an evolutionary journey of its own.
45:21A bipedal tetrapod with opposable thumbs
45:26and an over-inflated sense of self-worth.
45:48Four thousand years ago, Homo sapiens, that's us,
45:52inhabited much of the planet.
45:55We had city-states and agriculture.
45:59Empires were beginning to grow.
46:03And at this time in Europe and Asia,
46:07we begin to see evidence of a growing relationship
46:11between horses and humans.
46:18Now, no-one is exactly sure how the first horse was tamed.
46:22Maybe someone caught one of those wild horses,
46:25took it into captivity, gave it shelter, food,
46:28cared for it, loved it and trained it.
46:31But what we do know is that in pretty short time,
46:34we took these strong, efficient, powerful animals
46:39and turned them into our perfect companions.
46:43And you know, we didn't just tame them.
46:46Over generation after generation, we bred them,
46:49choosing those characteristics
46:51which favoured the way we wanted horses to be.
46:55So in the end, we took the wild horse
46:58and we turned it into the work horse.
47:14We chose the strongest.
47:17We chose the most powerful.
47:20But we also chose the friendliest,
47:24the most amenable.
47:29And for better or for worse,
47:31over the generations, the horse was altered.
47:39The ancestors of the modern horse were a pretty wild bunch.
47:44Diverse not only in terms of their physical appearance
47:47but also their genetic make-up.
47:50About 4,000 years ago, we see two gene variants appear.
47:56Now, one of those appears to make them less aggressive,
48:00more manageable.
48:03And the other, which appears to give them a stronger back,
48:07making them easier to ride.
48:09Now, what's interesting is that within the space
48:12of just a few hundred years,
48:14we'd spread those gene variants throughout the population.
48:19The wild horse was effectively gone.
48:22We had one global species selected by humans.
48:28You.
48:30Yes.
48:31I know.
48:32It wasn't my fault.
48:34I wasn't around then.
48:48Today, the horse goes by a new name.
48:54Equus Ferus Caballus.
48:57The domestic horse.
49:01Our relationship is a special one.
49:05Together, we've travelled to every corner of the globe.
49:11Step by step.
49:13And side by side.
49:21We often think of evolution as a battle between species.
49:24A game of winners and losers.
49:27A game of survival of the fittest.
49:29But very occasionally, species come together
49:32and the result is greater than the sum of their parts.
49:36Now, there's no doubt we played a hugely instrumental role
49:40in the evolution of the horse.
49:41But then the horse has had an impact on us too.
49:45Because without this remarkable animal
49:48as our greatest partner,
49:50we simply wouldn't be the species we are today.
49:58The horse's evolutionary journey is just one thread
50:03in an extraordinary tapestry.
50:07That weaves together every animal.
50:11In fact, every living thing on our planet.
50:17It's taken four billion years to get here.
50:22But boy, has life come a very, very long way.
50:30From the cell that began it all.
50:34To sex.
50:37To competition.
50:39To predation.
50:41To predation and protection.
50:49From the oceans to the land.
50:52And for some,
50:54back again.
50:59For others,
51:01onwards to the skies.
51:04There was a bum that changed the world.
51:08There were jaws, limbs, hearts and minds.
51:14Minds which have evolved to sense,
51:17to move, to love, to contemplate.
51:24And in our case,
51:26to begin to understand our own origins.
51:36A journey of knowledge
51:38that we're still on today.
51:44There's an outdated view,
51:46a mistaken idea
51:48that we humans
51:49are the be-all and end-all of evolution.
51:53That everything we've explored,
51:55everything we've shown you in this series
51:56was just about making us
51:59the perfect organism,
52:01the paragon of life on Earth.
52:04But it's simply not true.
52:07We're not perfect,
52:08and we weren't made.
52:10We've been shaped by exactly the same forces
52:13that have shaped every organism
52:15that's ever lived on this planet.
52:18And through a startling twist of fate,
52:21we are now having a profound effect
52:24effect on evolution ourselves.
52:26A dramatic, rapid and scary one
52:30because of what we're doing to our environment
52:32and because we're driving a massive extinction event.
52:38Now, evolution does feast on extinction.
52:43It loves the opportunities, the vacancies.
52:46So whatever we do now,
52:49life will go on.
52:51Life will be bright.
52:52Life will be beautiful.
52:54Life will be wonderful.
52:57But in evolutionary terms,
52:59what about us?
53:01Could we become shorter,
53:04slower, more short-sighted?
53:06Might we become smarter,
53:09more stupid?
53:11I don't think it really matters about our anatomy
53:15at this point.
53:17I think what matters is how we think,
53:20imagine,
53:21and create our way out of our situation.
53:26I think that what needs to be driving
53:28human evolution right now
53:33is hope.
53:56But before we go,
54:01how did we bring the story of evolution to life?
54:08The way that one animal over millions of years
54:11can transform into something radically different
54:14was once a mystery lost to time.
54:18If we think about the book,
54:20we have lots of different pages that tell us the story
54:22from start to finish.
54:24However, with evolution and fossils,
54:26some of those pages are missing.
54:29But occasionally, evidence is unearthed
54:32of the process in action.
54:35In 2004,
54:37paleontologists in the Canadian Arctic
54:39discovered a groundbreaking fossil.
54:43So this is a cast of tectalic.
54:45Now, tectalic lived about 375 million years ago.
54:49And it's got the scales very much like
54:51modern-day fish have today.
54:53And what's quite unusual is that it actually has a neck.
54:56And these bones that are around there,
54:58these are sort of collar-bore or shoulder girdle.
55:00It looks like a cross between a fish and an amphibian.
55:03And that's because that's exactly what it is.
55:06Tectalic was really this kind of unique snapshot
55:09in evolutionary time at this key moment
55:12for the water-to-land transition.
55:15So it's a perfect example of a transitional fossil.
55:18Transitional fossils are incredibly rare.
55:21They play the really important role
55:22of filling those gaps between morphologies
55:25that we kind of know are there,
55:26but we don't really know exactly what they might have looked like.
55:30Transitional fossils represent just one out of millions,
55:35possibly billions of individuals
55:37that over generations contribute to evolutionary change.
55:41Coming up with a way to illustrate this
55:44posed a huge challenge
55:46to the visual effects team behind the series.
55:49Evolution does not move in a straight line
55:52because it is purely opportunistic and slightly haphazard.
55:56It's tinkering. It's messing with what's already there
55:58rather than kind of always necessarily inventing something from scratch.
56:03It's all about a great grand experiment
56:05and just seeing what happens.
56:07The team spent thousands of hours
56:10crafting and animating computer-generated models
56:14to bring ancient animals back to life.
56:17But to illustrate the randomness and variation
56:20seen as life evolves,
56:22they needed to experiment.
56:25After consulting scientists
56:27to accurately model the key evolutionary changes,
56:30they used generative AI software
56:33to create hundreds of variations
56:35representing countless generations.
56:38And by hand-selecting and merging the best results
56:43with their original animations,
56:44they were able to condense millions of years of evolution.
56:49Look at that.
56:50There's bones inside.
56:51No way.
56:53Into a matter of seconds.
56:55In reality, this would take millions of years.
57:00This is a fantastic way to illustrate the evolution of form.
57:03This is basically how I imagine it playing out in my head.
57:16This series has been over four billion years in the making.
57:22And as a certain Charles Darwin once wrote,
57:26From so simple a beginning,
57:29endless forms, most beautiful and most wonderful,
57:33have been and are being evolved.
57:37One of the big key life lessons that I've learned
57:40from studying evolution is that change is constant.
57:44And change is the norm.
57:45So things have always changed and will always continue to change.
57:49And life will always continue to adapt.
57:53That's how it's always been and there's no reason to believe
57:56that's not how it's going to continue to be.
58:11Do you want to know how an elephant is related to a clownfish?
58:14Discover more in a poster from the Open University on the Tree of Life.
58:19To get your free copy, scan the QR code on screen
58:22or ring 0300 303 3460
58:26or visit connect.open.ac.uk slash evolution.
59:01and welcome to the map of the map.
59:04There's been a question that finelands has dropped.