All language subtitles for BBC.Evolution.2of5.The.Ostrich.1080p.x265.AAC.MVGroup.org

They're not the prettiest...

..or the brightest...

..and it's fair to say...

..they're a bit odd.

But ostriches produce something truly
astonishing...

..the biggest eggs on the planet.

Can I ask you to stop for a moment

and think about something truly
remarkable?

Something so commonplace, so everyday,
that we

take it for granted.

Life creates new life,

and it's happening right here in front
of me.

If I bend down...

Oh, yes! I can hear it!
RATTLING

I can hear it tapping.

It's as if it's yearning to get out of
the egg.

Oh!

And you know, around 40 days ago, the
chick that's just about to break

out of here into the big wide world
was just a tiny collection of cells.

And look at this, it's started!

I can see inside, I can see its little
eyes, its beak.

It's blinking at me.

Oh!
CHIRPING

It's quite emotional, if I'm honest
with you!

CHIRPING CONTINUES

So, how did this marvel of nature come
to be?

Well, to answer that question we have
to travel back...

..way back...

..before birds...

..before dinosaurs...

..before there were even eggs...

..following an unbroken chain of life
that stretches back

over four billion years.

This is the extraordinary story of how
evolution gave

rise to the ostrich, and its enormous
egg.

THUNDERCLAP

These are some of the world's first
living things.

They can't see, they can't hear...

..but right from the very beginning,

life on Earth was really good at one
thing...

..reproducing.

But back then, they did it in a way
that seems quite alien to us.

They split themselves in half to
create an identical copy.

A clone.

As soon as life appeared on Earth, it
began reproducing

and once it started, it did so at a
remarkable rate,

churning out copy after copy after
copy for billions of years.

The problem is, though, that when
you're just copying yourself,

it means that life's scope is quite
limited.

You see, for billions of years we had
nothing with eyes,

nothing with legs, nothing with a
brain, just single-celled

microbes, and it looked like life was
just going to stay like that.

Imagine a world filled with nothing
but microbes.

No plants, no insects, no birds of any
kind.

And definitely no people.

You see, it's not that I've got
anything against microbes,

but let's face it, life would be dull.

But for almost two billion years,

that's exactly how life was.

There was some mixing of DNA

and different species of microbe
evolved.

But the chances of life getting any
bigger than a pinhead looked slim.

Until...

..somewhere in this sea of simple
cells...

..a revolutionary emerges.

Now, it may seem similar to all the
microbes that came before it,

but it is in fact on a new branch of
the tree of life.

You, me and the ostrich - we are all
here today

because this microbe does something
scandalous.

It takes a shine to another microbe.

Their cell membranes fuse,

allowing all their DNA to mix.

This is the first sex...

..and it would change the course of
life on Earth forever.

It certainly wasn't romantic and it
wasn't earth shattering,

but the first sex was a very big deal.

And to understand why, we need to
understand what sex is,

and I know what you're thinking, don't
worry. No naff diagrams.

Fundamentally,

sexual reproduction is about two
living things coming together

to share their genes, to create new
life, a new life which is unique.

And that's why the first sex was so
pivotal, because after

billions of years of just copying,
here was a chance for mixing.

The first sex set life on a new path.

The offspring of this pair won't be
clones of their parents.

Instead, they'll inherit a random mix
of genes from both.

Sex creates variety

and it sends evolution into overdrive.

Let's fast forward through the next
one and a half billion years...

..during which time there is a sexual
revolution.

Some cells join forces...

..leading to big, complex bodies...

..the first animals.

By the Cambrian period,

the oceans are filled with a huge
diversity of animal life...

..from simple sponges to species

with eyes, legs and shells.

But all share one thing in common...

..they're a randy bunch.

We have a good understanding of how
rich and varied life was in the

Cambrian seas, down to the enormous
abundance of fossils that we've

recovered from that period, and you
know how much I love a fossil.

Look at this Trilobite. What a beauty!

You can see it's got its segmented
body here,

its rounded, smooth head, compound
eyes.

And I can tell you that we've
identified no less

than around 20,000 different species
of Trilobite.

I've got another fossil here. Look at
this.

This is an Eocrinoid,

an animal that's related to the sea
urchins, and we think that the

bottom part of it here was rooted into
the seabed and these tendrils

here would have been wafting in the
water flow, getting its food.

So, there was a great diversity of
life in those Cambrian seas,

but also a diversity of shape and
size,

and that made sex altogether more
challenging

because organisms like this couldn't
reproduce in the same way that their

ancient single-celled ancestors did,
by simply fusing together.

I mean, imagine a couple of trilobites
like this trying

to get it on. It's not going to work,
is it,

with the hard exoskeleton, all of
their legs, their internal organs?

Nature needed to come up with a
different way.

And nature's solution is an extremely
effective one.

Back in the Cambrian, many animals
have adopted it.

These tiny specks are eggs...

..and these even tinier ones are
sperm.

And they do exactly what those ancient
microbes did.

They fuse together and combine their
DNA

to create a new, unique life.

The Cambrian seas are quite literally
fertile oceans...

..but for many creatures here,

there's something unfamiliar about the
way they go about reproducing.

A lot of people don't like snails. I'm
not one of them.

There's something therapeutic about
having them slime

up and down your fingers.

These are a highly successful group of
animals.

There are more than 40,000 species in
the world,

and one of the keys to their success
is their reproductive capacity.

Like many snails, it produces sperm
and eggs.

It's a hermaphrodite.

Let's think about the repercussions of
that.

When this snail goes looking for a
potential partner, any other that it

finds of the same species and about
the same size, is a potential mate.

And once they've copulated, they can
both produce a batch of eggs,

doubling the capacity to produce a lot
more snails.

Now, this is such an efficient and
successful strategy that many

scientists believe that the earliest
animals were all hermaphrodite.

As soon as they could produce sperm
and eggs, they produced both,

which begs the question, why aren't we
all hermaphrodites today?

It's hard to know for certain, but
there's a theory

that during the Cambrian, something
upset the status quo...

..and it may have happened in a
creature like this.

It's so bizarre, it's hard to believe
it really existed.

But fossil evidence shows that it
really did look like this.

It's a Vetulicolian.

It's not a fish, it's not a
crustacean.

In fact, it's unlike anything that
lives today...

..and it's radically different from
its single-celled ancestors.

But it has inherited a key trait - a
one-track mind.

Now, if we assume Vetulicolians are
hermaphrodites,

that means that any member of the same
species is a potential mate.

But when this pair come together to
release their eggs and sperm...

..there's a problem.

You see, one of them was born
partially sterile.

It can't produce sperm.

For many animals, this would be the
end of their family line...

..but not for a hermaphrodite.

Because if it can still produce
eggs...

..it can still reproduce.

Its genes get passed down to the next
generation...

..and some of them are born partially
sterile too.

So, think about it.

In biological terms, that snail, if it
could only produce eggs,

we'd call it a female.

If it could only produce sperm, we
would call it a male.

So, there is the possibility that the
division of the sexes,

the origin of males and females, came
down to a chance mutation,

that we were mistakes.

Today, only 5% of animal species are
hermaphrodites.

The rest have separate sexes,

and it's thought that males

and females evolved multiple times, in
many different species,

allowing females to specialise in
producing fewer,

higher quality eggs,

whilst males make faster, more
numerous sperm.

Nature is of course flexible.

Clownfish males can turn into
females...

..seahorse dads get pregnant.

It really doesn't matter who does
what.

it's being a specialist that counts.

For animal life, this specialisation
is a turning point.

As we jump forward 150 million years,

it adds fuel to evolution's fire.

Fishes emerge and fill every marine
habitat.

And eventually, some even brave a new
frontier...

..the freshwater streams.

This ancestor of the ostrich is
looking for a safe place

to lay her eggs.

With streamlined bodies and powerful
tails...

..her shoal swim upstream with ease.

But...

..they're being followed.

If I were to time travel back to the
Devonian,

you would not find me wading in a
river like this.

No matter how sweaty the swamps were,
I wouldn't be tempted

to take to the waters because I might
lose my toes, or even my legs.

The rivers were filled full of
predatory fish,

armed with sharp teeth for tearing
through flesh.

Some of them the size of minnows,
others the size of crocodiles.

If you were a fish living in here,

you'd have enough trouble protecting
yourself, let alone your eggs.

Left unguarded in these ancient
waters,

nutritious eggs don't stand a chance.

These fish need to find a safer
breeding ground...

..or there'll be no next generation.

But they have something on their side
that other fish don't.

This is a 3D scan of a fossil of one
of those fishes.

And when you first look at it,

it looks pretty much like a modern,
conventional fish - it's long,

fairly streamlined, it's got a bit of
a blunt head there,

would have had a tail at the back for
propelling it through

the water, and all of the fins are
pretty much in the right places.

Looks a little bit like a salmon, but
on closer inspection,

in fact it's very different.

Let's zoom in on this fin here.

You can see that it's much longer and
the bones that

lead from it back to the core of the
skeleton are much more robust.

It could be that it was using these
fins to propel

itself along the bottom of the river.

They're much stronger than those
delicate ray fins that we

see on modern fishes. These are fins
that you could stand on.

The strong fins that help these fish
move along the riverbed also

allow them to do something
revolutionary...

..leave the river...

..and walk on land.

And beyond the main river lies a
network of streams

the predators can't reach.

We can't be certain why those
lobe-finned fish climbed

out of the water. I mean, they could
have been

looking for food, they could have been
avoiding being food themselves,

but there is the possibility

that they were looking for somewhere
safe to lay their eggs, to spawn.

But one thing's for sure, once they
waddled out of the water

and climbed onto land, there was no
going back.

Fish with the strongest fins are more
likely to reach

the predator-free waters.

They have more offspring, which
inherit their strong fins.

Over countless generations, the bones
get longer, stronger...

..and better for walking on land...

..until eventually, after millions of
years,

a fish's fin has become a limb.

There's absolutely no doubt that this
was a pivotal moment.

I mean, think about it.

Life on Earth had evolved in water,
and up until this point,

almost all life was still living in
water.

OK, around 100 million years earlier,

plants have made the difficult
transition onto land,

insects had managed it, too, but now
here was a new group -

animals walking on land on four legs
and four feet for the first time.

The amphibians.

Now, I'm about to show you something
which is remarkable,

astonishing even, and I think very
beautiful.

Take a look at this.

This is a drawing of the bones in the
foot

of one of those ancient amphibians.

It lived over 300 million years ago.

But look at it.

Does it look familiar? It should do.

That's because these ancient
amphibians were our ancestors,

and not only our ancestors, but the
ancestors of all the animals

with backbones that have ever lived or
are living on land today.

If those ancient microbes hadn't
discovered sex, bigger,

more complex animals may never have
evolved.

We wouldn't have males and females...

..with precious eggs,

that need protecting.

And the ancestors of every land animal
with a backbone,

including the ostrich, and us...

..may never have left the water...

..and evolved to live on land.

Now, we jump forward tens of millions
of years...

..and the amphibians are the planet's
dominant land animals.

But no reign lasts forever.

This is Casineria.

She can live happily in water and on
land...

..but like many animals here,
Casineria is in trouble.

Drought has set in.

Swamps that once stretched as far as
the eye can see are now

little more than muddy puddles.

To understand why this was a
problem...

..we only have to look at amphibians
today.

Clearly out of practice, but I did
manage to catch one.

This frog is rather attractive, I have
to say.

Look at those eyes, like little golden
jewels.

It looks slimy, but it's not.

It's shiny, and it's shiny because
it's wet,

and when it's wet, frogs like this can
breathe through their skin.

But it does need to be wet.

So, there's an inherent vulnerability
there.

They do need to return to water. They
can't dry out.

And it's not just the adults.

Their eggs need water too.

Amphibians can't reproduce without
water.

In periods of drought, amphibians
suffer.

But Casineria has managed to cling on.

Her survival is partly down to luck,
but also,

the unique mix of genes she inherited.

Now, had I been a bit sharper

and been able to catch another one of
these frogs,

then probably, to you and I, they
would look identical, like clones.

But of course they're not, because
frogs reproduce sexually.

They mix their genetic material to
produce unique individuals

and this doesn't only make life more
interesting.

Critically, it makes life more
resilient.

Think about it.

At this point in time,

this lovely stream is probably the
perfect place for this frog to be.

But what about if conditions change?

What about if it got drier or wetter
or the vegetation changed,

or something much more subtle like the
mineral content of the water?

Well, because every frog is different,

some will fare better than others.

They'll live longer and have more
offspring, and those

offspring will inherit the genes that
helped their parents survive.

Essentially, that's what we call
survival of the fittest.

Casineria's unique mix of genes
determines everything from her

size to her skin colour.

And it also determines her eggs.

As luck would have it,

they're better at retaining moisture
than most amphibian eggs...

..and in these dry conditions, that
difference means everything.

The slightest variation in the surface
structure or composition

of the egg is all it takes for one egg
to survive

when others don't.

And as generations pass, the egg
begins to change.

The surface gets tougher and thicker.

Special membranes form to prevent
moisture loss.

The egg gets larger, stronger, and
takes on an iconic shape...

..until eventually, after millions of
years,

something extraordinary has emerged...

..an egg that can survive on dry land.

From dying swamps, entirely new groups
of animals emerge.

Among them, the reptiles.

Look at this rock monitor, what a
beauty!

Sadly, you don't have time to watch me

falling in love with a lizard, so
let's look at the similarities

between this animal and those ancient
amphibians.

Well, firstly, it's got the same
streamlined nose

and long tail there.

Then look at her limbs, all four of
those legs and feet,

strong with those sturdy bones that
have been

passed down generations from the
lobed-fin fishes.

But there are differences too.

The skin is a striking one.

I mean, that is not shiny, moist and
breathable.

It's scaly and hard. It's about
keeping moisture in.

And then critically,

this reptile doesn't need to return to
water to breed.

You see, the amphibians might have
been first to walk the Earth,

but they were always limited by that
need for water.

It was the reptiles which really
conquered the land.

Reptile eggs are far more
sophisticated than the jelly

blobs of the amphibians.

Known as amniotic eggs, they have a
tough outer shell,

a nutrient rich yolk, and perhaps most
extraordinary of all,

a special sac of fluid in which the
embryo

floats in its own private pool.

The amniotic egg is like a pond on dry
land.

But when it came to sex,

these new high-tech reptile eggs
presented some challenges.

You see, an egg like this,

and this is a crocodile's egg, is no
good on its own.

It's got to be fertilised.

But there is absolutely no chance

of a sperm breaking through this
shell, so what's the solution?

Well, the solution is to get the sperm
to the

egg before the shell goes on, before
the egg is laid.

You see, the reptiles didn't only have
to reinvent the egg,

they had to reinvent sex.

The solution is found on almost every
male reptile today.

It begins to grow around the tenth day
of life.

A tiny bud, like an extra limb.

It's a penis.

Reptiles were amongst the first
animals to get penises...

..but they certainly weren't the last.

The blue whale has the largest,
averaging 2.5 metres.

The gorilla has one of the smallest,
compared to its body size.

Duck penises are shaped like
corkscrews...

..and cats' are covered in barbs.

Penises are as diverse as their
owners.

Now, despite what some people say,
penises are limited in size,

even for blue whales.

So, therefore for the males to deliver
the sperm where

they need to, they need to get close
to the females.

They need to mate...

Bonking, shagging, making love...

The terminology that we use in
scientific parlance is

copulation and the reptiles weren't
the first to get at it.

Some ancient fish had been doing it
for years,

but when it came to life on land, sex
as we know it had been invented.

With their sophisticated eggs...

..and a new way to fertilise them...

..the reptiles went forth and
multiplied.

Their fossilised remains have been
found in abundance.

But world domination wasn't the only

consequence of their reproductive
success.

The egg, the penis, copulation...

All of these adaptations helped with
the mechanics of sex,

but what was to happen next was
altogether different.

You see, copulation didn't only change
the way that animals looked.

It changed the way they behaved,

and the consequences of that were
extraordinary.

Around 100 million years after the
first reptiles emerged...

..some of them have evolved into the
most legendary creatures to

have ever walked the Earth.

This is Coelophysis,

one of the first dinosaurs.

Just like his ancient ancestors, he
has strong legs for walking on land.

But like all early dinosaurs, he walks
on two instead of four.

Bigger strides allow him to cover more
distance, which is handy,

because this young male is looking for
a mate.

There are plenty of females around.

The tricky part is getting their
attention.

So how do you impress a female?

I'm probably not the best person to
answer that,

I've been struggling all of my life,

but I reckon this guy's in with a
chance.

What a magnificent animal, so
handsome, honestly!

This is a Nyala, a Southern African
antelope,

and this is a mature male, and he's
very, very impressive,

certainly from that female's point of
view.

OK, he doesn't have a sports car.

Doesn't need it, he's got these
beautiful curled,

yellow-tipped horns.

Doesn't live in a mansion.

Doesn't need that either.

He's got those broad, powerful flanks.

And what's more, it's not just those
characteristics.

It's the fact that he's lived long
enough to be able to grow them.

I mean, imagine if this guy had been
born short-sighted or with a limp.

He would never have survived.

His good looks are visible signs that
he's fit and healthy,

and ultimately, that's what the
females are looking for.

Getting pregnant, developing your
youngster, giving birth,

then looking after it...

Those females can't afford to bank on
a weedy male.

They want the genes from the real
deal, like this guy.

When it comes to reproduction, it
tends to be the biggest,

hairiest males that succeed.

Their genes get passed down, making
future generations even bigger

and hairier than the last...

..which is how you end up with
exaggerated physical

traits like this.

But let's be very clear here, these
physical

characteristics are not necessarily
directly related to survival.

What they're about is finding a mate,
attracting that mate

and then successfully reproducing.

Evolution is not always about survival
of the fittest.

It's critically about getting your
genes into the next generation,

and that was as profoundly important
to the dinosaurs

as it is to these Nyala.

For Coelophysis, just like the Nyala,

good looks are a sign that the male is
in good condition.

And just look at that attractive fuzz.

But what's a male to do if no-one
seems to notice him?

Scientists suspect that some dinosaurs
did what many

animals still do today.

They show off.

It starts with head bobbing...

..followed by twirls...

..but to really impress her, he has
one final trick.

It's irresistible.

His offspring will inherit his
attractive fuzz,

and go on to have fuzzy offspring of
their own...

..becoming part of an extraordinary
evolutionary transformation.

Over time, fuzzy strands get longer,
and wider, and split into

multiple filaments, making an even
bigger surface area for display.

Until eventually, after tens of
millions of years

and countless generations...

..those fuzzy strands are so
exaggerated...

..they've become something new...

..feathers.

When the first fossilised feather was
found, scientists were

struck by its similarity to the
feathers of modern birds.

But this feather is 150 million years
old,

placing it firmly in the era of the
dinosaurs.

We don't know for certain what drove
their evolution.

Insulation and camouflage may have
played a role.

But we are now in little doubt

that some dinosaurs had feathers.

And many scientists believe it was the
need to attract a mate

that transformed dinosaurs from scaly
reptiles into flamboyant,

feathered creatures.

This is the tail feather of a
ring-necked pheasant.

It's beautiful, isn't it?

And whilst it still serves as a tail,
as you can see,

it's been given over to display.

It's elongated.

It's got this beautiful bronze
colouring with all of these

spots and when it comes to display
feathers, of course,

nothing beats the male peacock.

Look at that with that very
distinctive eye.

But this is a typical feather. Look at
it.

It's light, it's flexible, it's
durable.

It's essentially repairable.

If those barbs are pulled apart, it
can be fixed here.

But it's also symmetrical, very much

like the feathers that we first saw
when they appeared on the dinosaurs.

But tens of millions of years later,

something different cropped up in the
fossil record.

Something like this,

and you can see this is different
because it's asymmetrical.

The quill or the rachis, if you like,
here,

is much closer to this side.

Now, there is a theory which says that
this was

the result of a chance mutation, that
this was a mistake.

But if it was a mistake, it was a very
fortunate one,

because by shifting the rachis closer
to one side,

it means that when this feather is
pushed through the air,

it generates lift like an aircraft
wing.

The dinosaurs that were equipped with
these could fly.

Around 25 million years after the
first feathers evolved,

flying dinosaurs filled the skies.

Today, we have another name for
them...

..birds.

For almost 100 million years,

they thrived alongside their giant
cousins...

..and they were there to witness one
of our planet's darkest days.

EXPLOSION

When we say that all of the dinosaurs
became extinct,

it's not technically true, is it?

Because those that had evolved into
birds survived,

and the ones that did best were the
small ones,

they could hide away, and also those
with a very broad diet.

But as the Earth began to recover,
they had one other key asset,

the amniotic egg.

You see, with that embryo protected on
the inside from the hostile world

on the outside, they could continue to
reproduce, generation after

generation, to the extent that they
didn't just survive, they thrived.

The surviving birds were largely
ground dwellers.

Amongst them, the paleognaths,

some of whom would never

return to the skies.

Instead, they became big and heavy,

and better adapted for life on the
ground.

And to allow their chicks to hatch
fully formed and ready to run...

..their eggs evolved truly gigantic
sizes.

And one of this group...

..produces the largest eggs of all.

Ostriches, our largest birds.

And look at them standing there on
those strong legs,

with those sturdy bones that they
inherited from lobed-fin fishes.

And I can see those legs are covered
in scales,

so are their toes, signs of their
reptilian ancestry.

And their feathers are no longer used
for flying,

they're for display and brooding their
young.

And of course, they don't need to
return to water to lay their eggs.

These birds lay the largest amniotic
egg on the planet.

They lay them on the dry ground,

just as their reptilian ancestors did.

And safely cocooned inside each one,

a new life begins floating in water,

just as it's always done.

These chicks are the next chapter of
an extraordinary evolutionary

story, four billion years long...

..that reveals how the ostrich

and its enormous egg came to be.

And although those ancestors are long
gone,

their legacy lives on, not just in the
ostrich...

..but in all of us.

Just like this chick, all of us
started our lives in water,

floating in that amniotic fluid in the
womb, our very own private pool.

And that's because we share an
evolutionary history with this bird.

We share ancient ancestors in a
wonderful,

unbroken chain of reproduction,
stretching back billions of years.

And of course, we're not just
connected to ostriches.

We're connected to all life on Earth.

Everything that walks, flies,
slithers, slimes and crawls,

we're connected to it.

And that's all down to reproduction.

Over time, sexual reproduction has
shaped us

into different species...

..and sexual reproduction has one
other

absolutely extraordinary impact.

It makes us all unique.

Nothing exactly the same as me, you,

or her has ever lived,

or will ever live ever, in the entire
history

of this wonderful little blue planet
we call home.

Next time...

..how the bat evolved one of the most

insatiable appetites on the planet.

Look at this!

Truly spectacular!

From a prehistoric anus that caused a
mass extinction,

to gaping mouths...that became jaws.

And a surprising new way of finding
food.

This is the incredible story of one of
nature's... Oh!

..most formidable feeders.

Look at that!

But first...

..how do we know birds are living
dinosaurs?

- When most people look at a bird,
they don't see a dinosaur.

- The first clue of the extraordinary
evolutionary relationship

between birds and dinosaurs came in
the mid-19th century.

- The Jurassic species, Archaeopteryx,
is an icon of evolution.

- Archaeopteryx certainly looked a
little like a bird.

- It had feathered wings,

and yet upon those wings were fully
functional three-fingered

hands with claws, which is
reptile-like, and a long tail.

It had a head like that of a bird,

and yet, inside its mouth were rows of
sharp teeth.

- So, Archaeopteryx wasn't just a
bird.

It was also a dinosaur.

Other discoveries followed that left
no room for doubt.

- Birds are a type of theropod
dinosaur.

- We can see the evolutionary origins
of many bird

traits among their ancestors, the
dinosaurs.

Things like a beak, warm bloodedness,
feathers, a wishbone.

- Tyrannosaurus rex itself has a
wishbone.

- But one key question remains.

- What helped birds survive when all
of their dinosaurian

relatives went extinct, for me is one
of the most fascinating

questions in all of evolutionary
biology.

- A question that could have remained
unanswered

if it wasn't for a chance find.

- The first time I saw this fossil, I
was not very enthusiastic.

It's basically just a block of
limestone with a couple

broken bones poking out from it.

But we decided to take a closer look
at it anyway.

- A CT scanner revealed what was
hidden inside.

- When I first saw that skull on the
computer screen, it took

a second of silence, and then I
realised immediately that this

was one of the most important fossil
bird specimens ever discovered.

- Daniel had stumbled across the
oldest fossil of what

we would now recognise as a modern
bird.

And it lived alongside dinosaurs just
before the asteroid impact.

- It is toothless like modern birds.

Its beak looks quite a bit like a
small chicken bill,

and that's interesting.

It suggests to us that this animal was
probably a generalist feeder.

That is to say it wouldn't have been
very picky,

just like living chickens.

- Being flexible was critical to
surviving the asteroid impact.

- One of the best ways to survive was
to simply have the

ability to eat anything.

- And that might have been one of the
important features that

helped birds like this one survive the
mass extinction event.

- These small chicken-like ancestors
and a few other bird species

would make sure that not all the
dinosaurs were lost.

- When I see an ostrich,

I see that the... The story of
dinosaur evolution is not over.

- Today there are over 10,000 species
of birds.

In some ways, we are still living in
the age of dinosaurs.

- Do you want to know how an elephant
is related to a clownfish?

Discover more in a poster from the
Open University on the tree of life.

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