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00:17They're not the prettiest, or the brightest, and it's fair to say they're
00:29a bit odd.
00:33But ostriches produce something truly astonishing, the biggest eggs on the planet.
00:55Can I ask you to stop for a moment and think about something truly remarkable, something
01:01so commonplace, so everyday, that we take it for granted?
01:05Life creates new life, and it's happening right here in front of me.
01:13If I bend down...
01:17Oh, yes!
01:19Yes!
01:20I can hear it.
01:21I can hear it tapping.
01:24It's as if it's yearning to get out of the egg.
01:31And you know, around 40 days ago, the chick that's just about to break out of here, into
01:37the big wide world, was just a tiny collection of cells.
01:47Look at this.
01:49It's started.
01:51I can see inside.
01:53I can see his little eye, his beak is blinking at me.
02:00It's quite emotional, if I'm honest with you.
02:07So how did this marvel of nature come to be?
02:13Well, to answer that question, we have to travel back.
02:19Way back.
02:24Before birds.
02:28Before dinosaurs.
02:32Before there were even eggs.
02:37Following an unbroken chain of life that stretches back over four billion years.
02:49This is the extraordinary story of how evolution gave rise to the ostrich and its enormous egg.
03:43The
03:44These are some of the world's first living things.
03:51They can't see, they can't hear.
03:57But right from the very beginning,
04:00life on Earth was really good at one thing.
04:07Reproducing.
04:12But back then, they did it in a way that seems quite alien to us.
04:20They split themselves in half to create an identical copy.
04:29A clone.
04:36As soon as life appeared on Earth, it began reproducing.
04:40Once it started, it did so at a remarkable rate,
04:43churning out copy after copy after copy for billions of years.
04:49The problem is, though, that when you're just copying yourself,
04:53it means that life's scope is quite limited.
04:56You see, for billions of years, we had nothing with eyes,
05:01nothing with legs, nothing with a brain,
05:03just single-celled microbes.
05:06And it looked like life was just going to stay like that.
05:13Imagine a world filled with nothing but microbes.
05:19No plants, no insects, no birds of any kind.
05:26And definitely no people.
05:36You see, it's not that I've got anything against microbes.
05:41But let's face it, life would be dull.
05:50But for almost two billion years, that's exactly how life was.
06:00There was some mixing of DNA,
06:03and different species of microbe evolved.
06:07But the chances of life getting any bigger than a pinhead looked slim.
06:16Until...
06:18Somewhere in this sea of simple cells...
06:27A revolutionary emerges.
06:33Now, it may seem similar to all the microbes that came before it,
06:38but it is, in fact, on a new branch of the tree of life.
06:46You, me, and the ostrich.
06:49We are all here today because this microbe does something scandalous.
07:01It takes a shine to another microbe.
07:09Their cell membranes fuse,
07:12allowing all their DNA to mix.
07:20This is the first sex.
07:24And it would change the course of life on Earth forever.
07:40It certainly wasn't romantic, and it wasn't earth-shattering.
07:44But the first sex was a very big deal.
07:48And to understand why, we need to understand what sex is.
07:51And I know what you're thinking, don't worry, no naff diagrams.
07:55Fundamentally, sexual reproduction is about two living things
08:00coming together to share their genes to create new life.
08:05A new life which is unique.
08:07And that's why the first sex was so pivotal,
08:11because after billions of years of just copying,
08:14here was a chance for mixing.
08:17The first sex set life on a new path.
08:28The offspring of this pair won't be clones of their parents.
08:33Instead, they'll inherit a random mix of genes from both.
08:39Sex creates variety.
08:43And it sends evolution into overdrive.
08:54Let's fast forward to the next one and a half billion years.
09:00During which time, there is a sexual revolution.
09:06Some cells join forces, leading to big, complex bodies.
09:16The first animals.
09:30By the Cambrian period, the oceans are filled with a huge diversity of animal life.
09:38From simple sponges.
09:42To species with eyes, legs and shells.
09:50But all share one thing in common.
09:59They're a randy bunch.
10:06We have a good understanding of how rich and varied life was in the Cambrian seas,
10:12down to the enormous abundance of fossils that we've recovered from that period.
10:16And you know how much I love a fossil.
10:19Look at this trilobite.
10:21What a beauty.
10:22You can see it's got its segmented body here,
10:25its rounded smooth head, compound eyes.
10:29And I can tell you that we've identified no less than around 20,000 different species of trilobite.
10:38We've got another fossil here.
10:40Look at this.
10:41This is an eocrinoid.
10:44An animal that's related to the sea urchins.
10:47And we think that the bottom part of it here was rooted into the seabed.
10:51And these tendrils here would have been wafting in the water flow, getting its food.
10:56So there was a great diversity of life in those Cambrian seas, but also a diversity of shape and size.
11:04And that made sex altogether more challenging.
11:08Because organisms like this couldn't reproduce in the same way that their ancient single-celled ancestors did,
11:16by simply fusing together.
11:17Imagine a couple of trilobites like this trying to get it on.
11:21It's not going to work, is it?
11:22With the hard exoskeleton, all of their legs, their internal organs.
11:28Nature needed to come up with a different way.
11:34And nature's solution is an extremely effective one.
11:42Back in the Cambrian, many animals have adopted it.
11:52These tiny specks are eggs.
12:01And these even tinier ones are sperm.
12:07And they do exactly what those ancient microbes did.
12:12They fuse together and combine their DNA to create a new, unique life.
12:32The Cambrian seas are quite literally fertile oceans.
12:38But for many creatures here, there's something unfamiliar about the way they go about reproducing.
12:53A lot of people don't like snails. I'm not one of them.
12:57There's something therapeutic about having them slime up and down your fingers.
13:04These are a highly successful group of animals.
13:07There are more than 40,000 species in the world.
13:11And one of the keys to their success is their reproductive capacity.
13:15Like many snails, it produces sperm and eggs.
13:19It's a hermaphrodite.
13:24Let's think about the repercussions of that.
13:27When this snail goes looking for a potential partner,
13:31any other that it finds of the same species and about the same size is a potential mate.
13:40And once they've copulated, they can both produce a batch of eggs, doubling the capacity to produce a lot more
13:49snails.
13:50Now, this is such an efficient and successful strategy that many scientists believe that the earliest animals were all hermaphrodite.
14:00As soon as they could produce sperm and eggs, they produced both.
14:05Which begs the question, why aren't we all hermaphrodites today?
14:13It's hard to know for certain.
14:16But there's a theory that during the Cambrian, something upset the status quo.
14:26And it may have happened in a creature like this.
14:37It's so bizarre.
14:39It's hard to believe it really existed.
14:45But fossil evidence shows that it really did look like this.
14:59It's a vertulacoleum.
15:03It's not a fish. It's not a crustacean.
15:07In fact, it's unlike anything that lives today.
15:12And it's radically different from its single-celled ancestors.
15:19But it has inherited a key trait.
15:23A one-track mind.
15:30Now, if we assume vertulacoleans are hermaphrodites,
15:35that means that any member of the same species is a potential mate.
15:46But when this pair come together to release their eggs and sperm,
15:52there's a problem.
15:57You see, one of them was born partially sterile.
16:01It can't produce sperm.
16:04It can't produce sperm.
16:06For many animals, this would be the end of their family line.
16:13But not for a hermaphrodite.
16:20Because if it can still produce eggs, it can still reproduce.
16:31Its genes get passed down to the next generation.
16:36And some of them are born partially sterile, too.
16:44So, think about it.
16:45In biological terms, that snail, if it could only produce eggs,
16:50we call it a female.
16:51If it could only produce sperm, we would call it a male.
16:55So, there is the possibility that the division of the sexes,
16:59the origin of males and females,
17:02came down to a chance mutation.
17:05That we were mistakes.
17:13Today, only 5% of animal species are hermaphrodites.
17:20The rest have separate sexes.
17:25And it's thought that males and females evolved multiple times
17:31in many different species.
17:33Allowing females to specialise in producing fewer,
17:38higher quality eggs.
17:41Whilst males make faster, more numerous sperm.
17:48Nature is, of course, flexible.
17:52Clownfish males can turn into females.
17:56Seahorse dads get pregnant.
18:03It really doesn't matter who does what.
18:07It's being a specialist that counts.
18:19For animal life, this specialisation is a turning point.
18:30As we jump forward 150 million years,
18:34it adds fuel to evolution's fire.
18:40Fishes emerge.
18:41You fill every marine habitat.
18:55And eventually, some even brave a new frontier.
19:10The freshwater streams.
19:17This ancestor of the ostrich is looking for a safe place to lay her eggs.
19:29With streamlined bodies and powerful tails,
19:34her shoals swim upstream with ease.
19:39But...
19:41they're being followed.
19:55If I were to time travel back to the Devonian,
19:58you would not find me wading in a river like this.
20:02No matter how sweaty the swamps were,
20:04I wouldn't be tempted to take to the waters.
20:07Because I might lose my toes or even my legs.
20:10The rivers were filled full of predatory fish,
20:14armed with sharp teeth for tearing through flesh.
20:18Some of them the size of minnows.
20:20Others, the size of crocodiles.
20:23If you were a fish living in here,
20:25you'd have enough trouble protecting yourself,
20:28let alone your eggs.
20:35Left unguarded in these ancient waters,
20:39nutritious eggs don't stand a chance.
20:51These fish need to find a safer breeding ground.
20:56Or they'll be no next generation.
21:02But they have something on their side that other fish don't.
21:12This is a 3D scan of a fossil of one of those fishes.
21:17And when you first look at it,
21:18it looks pretty much like a modern, conventional fish.
21:22It's long, fairly streamlined.
21:24It's got a bit of a blunt head there.
21:26Would have had a tail at the back for propelling it through the water.
21:29And all of the fins are pretty much in the right places.
21:33Looks a little bit like a salmon.
21:35But on closer inspection, in fact, it's very different.
21:39Let's zoom in on this fin here.
21:43You can see that it's much longer.
21:46And the bones that lead from it back to the core of the skeleton
21:50are much more robust.
21:53It could be that it was using these fins
21:56to propel itself along the bottom of the river.
22:00They're much stronger than those delicate ray fins
22:03that we see on modern fishes.
22:05These are fins that you could stand on.
22:17The strong fins that help these fish move along the riverbed
22:22also allow them to do something revolutionary.
22:39Leave the river.
22:43And walk on land.
22:54And beyond the main river lies a network of streams
22:58the predators can't reach.
23:02We can't be certain why those lobed finned fish climbed out of the water.
23:08I mean, they could have been looking for food.
23:10They could have been avoiding being food themselves.
23:13But there is the possibility that they were looking for somewhere safe
23:18to lay their eggs to spawn.
23:20But one thing's for sure.
23:22Once they waddled out of the water and climbed onto land
23:26there was no going back.
23:35Fish with the strongest fins are more likely to reach the predator-free waters.
23:45They have more offspring which inherit their strong fins.
23:53Over countless generations, the bones get longer.
24:00Stronger.
24:02And better for walking on land.
24:10Until eventually, after millions of years,
24:16a fish's fin has become a limb.
24:27There's absolutely no doubt that this was a pivotal moment.
24:33I mean, think about it.
24:35Life on Earth had evolved in water.
24:38And up until this point, almost all life was still living in water.
24:43OK, around 100 million years earlier,
24:46plants had made the difficult transition onto land.
24:49Insects had managed it too.
24:51But now, here was a new group.
24:55Animals walking on land on four legs and four feet for the first time.
25:01The amphibians.
25:04Now, I'm about to show you something which is remarkable, astonishing even.
25:09And I think very beautiful.
25:12Take a look at this.
25:15This is a drawing of the bones in the foot of one of those ancient amphibians.
25:21It lived over 300 million years ago.
25:25But look at it.
25:27Does it look familiar?
25:30It should do.
25:31That's because these ancient amphibians were our ancestors.
25:38And not only our ancestors, but the ancestors of all the animals with backbones that have ever lived or are
25:47living on land today.
25:59If those ancient microbes hadn't discovered sex, bigger, more complex animals may never have evolved.
26:12We wouldn't have males and females with precious eggs that need protecting.
26:25And the ancestors of every land animal with a backbone, including the ostrich and us,
26:37may never have left the water and evolved to live on land.
26:49Now we jump forward tens of millions of years.
27:02And the amphibians are the planet's dominant land animals.
27:16But no rain lasts forever.
27:23This is Cassinaria.
27:26She can live happily in water and on land.
27:32But like many animals here, Cassinaria is in trouble.
27:43Drought has set in.
27:51Swamps that once stretched as far as the eye can see, are now little more than muddy puddles.
28:06To understand why this was a problem, we only have to look at amphibians today.
28:17Clearly out of practice, but I did manage to catch one.
28:20This frog is rather attractive, I have to say.
28:23Look at those eyes, like little golden jewels.
28:26It looks slimy, but it's not.
28:29It's shiny.
28:30And it's shiny because it's wet.
28:33And when it's wet, frogs like this can breathe through their skin.
28:37But it does need to be wet.
28:39So there's an inherent vulnerability there.
28:42They do need to return to water.
28:44They can't dry out.
28:46And it's not just the adults.
28:49Their eggs need water too.
28:52Amphibians can't reproduce without water.
29:00In periods of drought,
29:04amphibians suffer.
29:10But Cassinaria has managed to cling on.
29:18Her survival is partly down to luck,
29:22but also the unique mix of genes she inherited.
29:33Now, had I been a bit sharper
29:35and been able to catch another one of these frogs?
29:38Then probably, to you and I, they would look identical.
29:41Like clones.
29:42But of course they're not.
29:44Because frogs reproduce sexually.
29:47They mix their genetic material to produce unique individuals.
29:52And this doesn't only make life more interesting.
29:55Critically, it makes life more resilient.
29:59Think about it.
30:00At this point in time, this lovely stream is probably the perfect place for this frog to be.
30:05But what about if conditions change?
30:07What about if it got drier?
30:09Or wetter?
30:10Or the vegetation changed?
30:12Or something much more subtle, like the mineral content of the water?
30:17Well, because every frog is different, some will fare better than others.
30:23They'll live longer and have more offspring.
30:27And those offspring will inherit the genes that helped their parents survive.
30:34Essentially, that's what we call survival of the fittest.
30:47Cassinaria's unique mix of genes determines everything, from her size to her skin colour.
30:54And it also determines her eggs.
31:05As luck would have it, they're better at retaining moisture than most amphibian eggs.
31:15And in these dry conditions, that difference means everything.
31:28The slightest variation in the surface structure or composition of the egg is all it takes for one egg to
31:38survive when others don't.
31:43And as generations pass, the egg begins to change.
31:58The surface gets tougher and thicker.
32:02Special membranes form to prevent moisture loss.
32:07The egg gets larger, stronger, and takes on an iconic shape.
32:16Until eventually, after millions of years, something extraordinary has emerged.
32:29An egg that can survive on dry land.
32:41From dying swamps, entirely new groups of animals emerge.
32:47Among them, the reptiles.
32:53Look at this rock monitor.
32:56What a beauty.
32:58Sadly, we don't have time to watch me falling in love with a lizard.
33:02So, let's look at the similarities between this animal and those ancient amphibians.
33:08Well, firstly, it's got the same streamlined nose and long tail there.
33:15Then, look at her limbs.
33:17All four of those legs and feet.
33:19Strong with those sturdy bones that have been passed down generations from the lobed-finned fishes.
33:26But there are differences too.
33:28The skin is a striking one.
33:29I mean, that is not shiny, moist, and breathable.
33:34It's scaly and hard.
33:36It's about keeping moisture in.
33:38And then, critically, this reptile doesn't need to return to water to breed.
33:46You see, the amphibians might have been first to walk the earth,
33:49but they were always limited by that need for water.
33:53It was the reptiles which really conquered the land.
34:05Reptile eggs are far more sophisticated than the jelly blobs of the amphibians.
34:13Known as amniotic eggs, they have a tough outer shell, a nutrient-rich yolk, and perhaps most extraordinary of all,
34:25a special sack of fluid in which the embryo floats in its own private pool.
34:34The amniotic egg is like a pond on dry land.
34:45But when it came to sex, these new high-tech reptile eggs presented some challenges.
34:52You see, an egg like this, and this is a crocodile's egg, is no good on its own.
34:57It's got to be fertilised.
34:58But there is absolutely no chance of a sperm breaking through this shell.
35:05So, what's the solution?
35:07Well, the solution is to get the sperm to the egg before the shell goes on, before the egg is
35:14laid.
35:14You see, the reptiles didn't only have to reinvent the egg, they had to reinvent sex.
35:26The solution is found on almost every male reptile today.
35:34It begins to grow around the tenth day of life.
35:39A tiny bud, like an extra limb.
35:46It's a penis.
35:55Reptiles were amongst the first animals to get penises.
35:59But they certainly weren't the last.
36:07The blue whale has the largest, averaging 2.5 metres.
36:15The gorilla has one of the smallest, compared to its body size.
36:22Duck penises are shaped like corkscrews.
36:27And cats are covered in barbs.
36:33Penises are as diverse as their owners.
36:40Now, despite what some people say, penises are limited in size, even for blue whales.
36:47So, therefore, for the males to deliver the sperm where they need to, they need to get close to the
36:52females.
36:52They need to mate, bonking, shagging, making love.
36:59The terminology that we use in scientific parlance is copulation.
37:03And the reptiles weren't the first to get at it.
37:06Some ancient fish had been doing it for years.
37:09But when it came to life on land, sex, as we know it, had been invented.
37:21With their sophisticated eggs...
37:26..and a new way to fertilise them...
37:28..the reptiles went forth and multiplied.
37:44Their fossilised remains have been found in abundance.
37:57But world domination wasn't the only consequence of their reproductive success.
38:08The egg, the penis, copulation...
38:12..all of these adaptations helped with the mechanics of sex.
38:15But what was to happen next was altogether different.
38:19You see, copulation didn't only change the way that animals looked...
38:23..it changed the way they behaved.
38:26And the consequences of that were extraordinary.
38:37Around 100 million years after the first reptiles emerged...
38:47..some of them have evolved into the most legendary creatures to have ever walked the Earth.
38:59This is Coelophysis, one of the first dinosaurs.
39:05Just like his ancient ancestors, he has strong legs for walking on land.
39:14..but like all early dinosaurs, he walks on two instead of four.
39:21Bigger strides allow him to cover more distance.
39:26Which is handy, because this young male is looking for a mate.
39:35There are plenty of females around.
39:38The tricky part is getting their attention.
39:48So, how do you impress a female?
39:51Probably not the best person to answer that.
39:53Been struggling all of my life, but...
39:55..I reckon this guy's in with a chance.
39:58What a magnificent animal.
40:01So handsome, honestly.
40:04This is a Nyala, Southern African antelope.
40:08And this is a mature male.
40:10And he is very, very impressive.
40:13Certainly from that female's point of view.
40:18OK, he doesn't have a sports car.
40:20Doesn't need it.
40:21It's got those beautiful, curled, yellow-tipped horns.
40:26Doesn't live in a mansion.
40:27Doesn't need that either.
40:29It's got those broad, powerful flanks.
40:33And what's more, it's not just those characteristics.
40:36It's the fact that he's lived long enough to be able to grow them.
40:41I mean, imagine if this guy had been born short-sighted or with a limp.
40:45He would never have survived.
40:49His good looks are visible signs that he's fit and healthy.
40:55And ultimately, that's what the females are looking for.
41:01Getting pregnant, developing your youngster, giving birth,
41:05then looking after it.
41:06Those females can't afford to bank on a weedy male.
41:12They want the genes from the real deal.
41:15Like this guy.
41:23When it comes to reproduction,
41:25it tends to be the biggest, hairiest males that succeed.
41:32Their genes get passed down.
41:34Making future generations even bigger and hairier than the last.
41:41Which is how you end up with exaggerated physical traits like this.
41:47But let's be very clear here.
41:50These physical characteristics are not necessarily directly related to survival.
41:57What they're about is finding a mate, attracting that mate,
42:02and then successfully reproducing.
42:04Evolution is not always about survival of the fittest.
42:09It's critically about getting your genes into the next generation.
42:14And that was as profoundly important to the dinosaurs as it is to these niala.
42:26For Coelophysis, just like the niala, good looks are a sign that the male is in good condition.
42:35And just look at that attractive fuzz.
42:43But what's a male to do if no one seems to notice him?
42:51Scientists suspect that some dinosaurs did what many animals still do today.
43:02They show off.
43:05It starts with head bobbing.
43:09Followed by twirls.
43:13But to really impress her, he has one final trick.
43:27It's irresistible.
43:36His offspring will inherit his attractive fuzz.
43:40And go on to have fuzzy offspring of their own.
43:45Becoming part of an extraordinary evolutionary transformation.
43:51Over time, fuzzy strands get longer.
43:56And wider.
43:57And split into multiple filaments.
44:01Making an even bigger surface area for display.
44:10Until eventually, after tens of millions of years and countless generations, those fuzzy
44:20strands are so exaggerated, they've become something new.
44:40Feathers. When the first fossilised feather was found, scientists were struck by its similarity
44:46to the feathers of modern birds. But this feather is 150 million years old, placing it firmly
44:57in the era of the dinosaurs.
45:03We don't know for certain what drove their evolution. Insulation and camouflage may have played
45:12a role, but we're now in little doubt that some dinosaurs had feathers.
45:24And many scientists believe it was the need to attract a mate that transformed dinosaurs
45:32from scaly reptiles into flamboyant feathered creatures.
45:52This is the tail feather of a ring-necked pheasant. It's beautiful, isn't it? And whilst it still
46:01serves as a tail, as you can see, it's been given over to display. It's elongated. It's
46:07got this beautiful bronze colouring with all of these spots. And when it comes to display feathers,
46:13of course, nothing beats the male peacock. Look at that with that very distinctive eye.
46:20But this is a typical feather. Look at it. It's light. It's flexible. It's durable. It's essentially
46:27repairable. If those barbs are fall apart, it can be fixed here. But it's also symmetrical.
46:34Very much like the feathers that we first saw when they appeared on the dinosaurs.
46:40But tens of millions of years later, something different cropped up in the fossil record.
46:46Something like this. And you can see this is different because it's asymmetrical. The quill or the ratchets,
46:54if you like, here is much closer to this side. Now, there is a theory which says that this was
47:01the result
47:02of a chance mutation, that this was a mistake. But if it was a mistake, it was a very fortunate
47:09one.
47:10Because by shifting the ratchets closer to one side, it means that when this feather is pushed
47:17through the air, it generates lift like an aircraft wing. The dinosaurs that were equipped with these could fly.
47:35Around 25 million years after the first feathers evolved, flying dinosaurs filled the skies.
47:47Today, we have another name for them. Birds.
47:57For almost a hundred million years, they thrived alongside their giant cousins.
48:07And they were there to witness one of our planet's darkest days.
48:29When we say that all of the dinosaurs became extinct, it's not technically true, is it? Because
48:35those that had evolved into birds survived. And the ones that did best were the small ones,
48:41they could hide away. And also those with a very broad diet. But as the earth began to recover,
48:47they had one other key asset. The amniotic egg. You see, with that embryo protected on the inside,
48:56from the hostile world on the outside, they could continue to reproduce, generation after generation,
49:02to the extent that they didn't just survive, they thrived.
49:12The surviving birds were largely ground dwellers.
49:18Amongst them, the paleonates, some of whom would never return to the skies.
49:26Instead, they became big, and heavy, and better adapted for life on the ground.
49:33And to allow their chicks to hatch fully formed and ready to run,
49:39their eggs evolved truly gigantic sizes.
49:45And one of this group...
49:51...produces the largest eggs of all.
50:10Ostriches. Our largest birds. And look at them, standing there on those strong legs,
50:18with those sturdy bones that they inherited from lobed-fin fishes. And I can see those legs are
50:26covered in scales. So are their toes. Signs of their reptilian ancestry.
50:32And their feathers are no longer used for flying. They're for display and brooding their young.
50:38And of course, they don't need to return to water to lay their eggs. These birds lay the largest
50:46amniotic egg on the planet.
50:52They lay them on the dry ground, just as their reptilian ancestors did.
51:01And safely cocooned inside each one,
51:06a new life begins, floating in water, just as it's always done.
51:18A new life begins.
51:24These chicks are the next chapter of an extraordinary evolutionary story.
51:32Four billion years long.
51:35That reveals how the ostrich and its enormous egg came to be.
51:45And although those ancestors are long gone, their legacy lives on.
51:52Not just in the ostrich, but in all of us.
52:00Just like this chick, all of us started our lives in water,
52:05floating in that amniotic fluid in the womb, our very own private pool.
52:10And that's because we share an evolutionary history with this bird.
52:15We share ancient ancestors in a wonderful, unbroken chain of reproduction stretching back
52:22billions of years.
52:24And of course, we're not just connected to ostriches.
52:27We're connected to all life on Earth.
52:31Everything that walks, flies, slithers, slithers, slimes and crawls.
52:37We're connected to it.
52:39And that's all down to reproduction.
52:42Over time, sexual reproduction has shaped us into different species.
52:47And sexual reproduction has one other absolutely extraordinary impact.
52:53It makes us all unique.
52:57Nothing exactly the same as me, you or her has ever lived or will ever live, ever,
53:07in the entire history of this wonderful little blue planet we call home.
53:32Next time, how the bat evolved one of the most
53:36insatiable appetites on the planet.
53:39Look at this.
53:41Truly spectacular.
53:44From a prehistoric anus that caused a mass extinction
53:49to gaping mouths
53:52that became jaws.
53:55And a surprising new way of finding food.
54:02This is the incredible story of one of nature's most formidable feeders.
54:09Look at that.
54:15But first, how do we know birds are living dinosaurs?
54:22When most people look at a bird, they don't see a dinosaur.
54:29The first clue of the extraordinary evolutionary relationship between birds and dinosaurs
54:35came in the mid-19th century.
54:38The Jurassic species Archaeopteryx is an icon of evolution.
54:45Archaeopteryx certainly looked a little like a bird.
54:49It had feathered wings, and yet upon those wings were fully functional three-fingered hands with claws,
54:56which is reptile-like, and a long tail.
55:00It had a head like that of a bird, and yet inside its mouth were rows of sharp teeth.
55:10So, Archaeopteryx wasn't just a bird.
55:13It was also a dinosaur.
55:19Other discoveries followed that left no room for doubt.
55:25Birds are a type of theropod dinosaur.
55:29We can see the evolutionary origins of many bird traits among their ancestors,
55:36the dinosaurs. Things like a beak, warm-bloodedness, feathers, a wishbone.
55:43Tyrannosaurus rex itself has a wishbone.
55:46But one key question remains.
55:49What helped birds survive when all of their dinosaurian relatives went extinct,
55:54for me, is one of the most fascinating questions in all of evolutionary biology.
56:02A question that could have remained unanswered if it wasn't for a chance find.
56:09The first time I saw this fossil, I was not very enthusiastic.
56:13It's basically just a block of limestone with a couple broken bones poking out from it.
56:20But we decided to take a closer look at it anyway.
56:23A CT scanner revealed what was hidden inside.
56:29When I first saw that skull on the computer screen,
56:33it took a second of silence. And then I realized immediately that this was one of the most important
56:41fossil bird specimens ever discovered.
56:45Daniel had stumbled across the oldest fossil from what we would now recognize as a modern bird.
56:51And it lived alongside dinosaurs, just before the asteroid impact.
56:57It is toothless, like modern birds.
57:00It's beak looks quite a bit like a small chicken bill.
57:04And that's interesting. It suggests to us that this animal was probably a generalist feeder.
57:10That is to say, it wouldn't have been very picky, just like living chickens.
57:16Being flexible was critical to surviving the asteroid impact.
57:21One of the best ways to survive was to simply have the ability to eat anything.
57:26And that might have been one of the important features that helped birds like this one survive the mass extinction
57:33event.
57:35These small chicken-like ancestors and a few other bird species would make sure that not all the dinosaurs were
57:43lost.
57:44When I see an ostrich, I see that the story of dinosaur evolution is not over.
57:52Today, there are over 10,000 species of birds.
57:56In some ways, we are still living in the age of dinosaurs.
58:05Do you want to know how an elephant is related to a clownfish?
58:09Discover more in a poster from the Open University on the Tree of Life.
58:13To get your free copy, scan the QR code on screen or ring 0300 303 3460.
58:20Or visit connect.open.ac.uk slash evolution.
58:25Visit connect.com to other people on the Tree of Life.
58:29Visit connect.com to the PCC PlayStation Cine c suficiente for 鞚挫毄!
58:35For moreante lucf!
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