All language subtitles for When Whales Walked EN

♪

MAN: I was taken out
to this site

in the middle of the desert.

I had no idea what awaited me.

And then I saw them,
and I just started crying.

NARRATOR: These trackways
in the Arabian Desert

are footprints in time.

They were made
seven million years ago

by prehistoric elephants.

They take us back
to a bygone world

and its vanished creatures.

How did elephants
from so long ago

give rise to the magnificent
animals we know today?

How did any of the animals
in this African landscape

become what they are?

For generations,
it was a mystery.

Now scientists
are revealing the answers...

WOMAN: You can see
the exceptional preservation

of soft tissues.

NARRATOR: ...piecing together
an epic story.

Fossils are the key.

MAN: Fossils are
the messengers of the past.

I believe that.

MAN: Imagine I'm taking you
on a safari,

but a safari back in time.

You'll be confronted
with these magical creatures,

a slice of Africa
that is now gone.

NARRATOR: This film
unlocks the evolution

of four of the world's
most spectacular creatures--

crocodiles,

birds,

whales...

[whale singing]

[roars]

and elephants.

Like every animal alive today,
they have a deep time history,

a lineage full
of twists and turns,

shaped by strange ancestors
from long ago--

bizarre ancient crocs...

MAN: This thing
was built like a greyhound.

NARRATOR:
...feathered dinosaurs...

WOMAN: Dinosaurs
never went extinct.

In fact, birds are dinosaurs.

NARRATOR: ...a whale ancestor
that lived on land.

MAN: It more looks like a dog
with a long snout.

NARRATOR: With new tools
at their fingertips,

researchers are filling in
the gaps in the story of life,

charting the rise and fall
of ancient animals,

revealing why some died out
while others survived.

MAN: How did these
ancient worlds flourish,

and why did they disappear?

So, this is to me, really
sort of the ultimate story.

NARRATOR: It's not just
a story about the past.

It tells us about
the world today, its creatures,

and what they may be facing
in the future.

WOMAN: There used to be dozens
of species of elephants,

and now there are just three.

And if we're not careful,
we will lose them as well,

and that will be the end
of the lineage of elephants.

NARRATOR: It's a story millions
of years in the making,

of lost creatures rediscovered

and the surprising lessons
of deep time.

♪

♪

♪

Madagascar,

250 miles
off the coast of Africa.

This island is
a perfect laboratory

for the study
of evolutionary change.

Isolated here
for millions of years,

species have transformed
in unique ways.

Scientists have long studied

the evolution of the island's
chameleons, bats, and lemurs.

Now the search is on
for the ancient history

of one of Earth's
strangest animals--

the crocodile.

♪

In flooded underground caves,

researchers are looking
for the remains

of an extinct croc species.

It may have disappeared
just 2,000 years ago,

a recent twist
in the story of crocs.

EVON HEKKALA: Some people
see crocodiles as this animal

that's unchanging through time.

And, actually, we know now
that that's not true,

but they look like it.

I'm Dr. Evon Hekkala,
and I use DNA

to look at how crocodiles
have changed in the recent past

and how they are related
to each other in deeper time.

Most of the living species
of crocodile

are really, really
hard to tell apart,

unless you're somebody
who spends all your time

thinking about crocodiles,
like me.

NARRATOR: Cold-blooded,

ferocious,

but strangely beautiful,

the 14 living crocodile species
are all very similar.

They all have
the same reptilian body plan...

low to the ground

and armored from head to toe
in thick scales.

♪

They seem like living fossils,

some hangover from the age
of dinosaurs.

But are they?

Is this really
an animal frozen in time?

Perhaps the mysterious species
in the cave

will provide some answers about
recent crocodile evolution.

HEKKALA: So, there's
this crocodile that existed

on the island of Madagascar
until relatively recently,

and it disappears about the same
time that humans got here,

and that crocodile was called

the horned crocodile
of Madagascar.

And so, one of the big questions
is, what was that crocodile?

Who were its relatives?

And what happened to it?

It's one of
the biggest mysteries.

♪

NARRATOR: Today there is only
one species on Madagascar...

the famous Nile crocodile...

one of the fiercest
of Africa's predators.

♪

[wildebeest bellowing]

♪

Scientists think it squeezed out
the smaller horned croc,

but there's a lot
they don't know.

There may be answers
in the flooded caves.

A dive team sets out

to search for the bones
of the horned croc.

The caves are a time capsule,

where the remains
of ancient animals

have been preserved
for thousands of years.

HEKKALA: I knew from speaking
with some other people

that there were supposedly
crocodile skulls in this cave

of this species that no one
has seen for at least 200 years,

but more likely 1,000 years.

NARRATOR: Evon waits,
hoping the skulls are there.

HEKKALA: And I'm sitting there
and I'm thinking,

just the anticipation
is like, "Any minute,

I'm going to get
to see this thing."

It must be so exciting
when they bring things in.

You have no idea
what they're going to bring.

WOMAN: Yeah, yeah,
it's like Christmas every time.

NARRATOR: Deep in the caves,

divers have to squeeze
through tight spaces.

If they brush the bottom,

they can stir up clouds of silt
and lose their way.

♪

A half hour in, they see it--

a skull.

♪

♪

♪

WOMAN: What do you think?

HEKKALA: It looks
like a crocodile!

WOMAN: Does it?

HEKKALA: So excited.

WOMAN: A skull?
HEKKALA: Yeah.

WOMAN: Look at that,
it looks perfect.

HEKKALA: Oh,
it's beautiful. Wow!

WOMAN: Oh, my God!
It is a crocodile.

HEKKALA: You know,
half the collections

are just pieces, so...

WOMAN: That is so gorgeous.

You got it?

HEKKALA: Yeah, I've got it.

This is a skull of the extinct
horned crocodile of Madagascar,

and when researchers
first started coming

to Madagascar from Europe,
they saw these crocodile skulls,

and they weren't sure
exactly what they were.

They didn't look exactly
like Nile crocodiles.

They realized
it was a separate species.

This individual is
the first individual I've seen

that came out of a cave,
a water-filled cave,

so that is pretty exciting.

NARRATOR: If Evon's lucky,

she'll be able
to extract its DNA

and learn
where the horned croc fits

into the story
of crocodile evolution.

The results will take time,
but one thing is clear--

apart from its small
but distinctive horns,

this animal was very similar
to the crocs alive today--

armored, low to the ground,

with short legs
and large, powerful jaws.

To us, this body plan
is what defines a crocodile,

but millions of years
in the past,

there was more than one way
to be a croc.

HEKKALA: One of the cool things
that's happening these days

is that we're finding out
that the ancient crocodilians

were incredibly diverse,

and there are
all different forms of them.

NARRATOR: Scientists
are now discovering

the earliest ancient crocs.

They were nothing like
the animals alive today.

To meet the very first crocs,

we must trace one branch
of the vast tree of life

far back in deep time,
230 million years

into the geologic period
called the Triassic.

It's hard to imagine
such a vast expanse of time.

HANS SUES: We throw around
numbers as scientists,

but at the same time, do we
really understand what it means

that 100 million years
have passed?

I'm Hans Sues.
I'm a paleontologist

at the Smithsonian Institution
in Washington, D.C.,

and I study fossils.

If you look, for instance,
at your historical time,

you can think back
to your grandparents

and that time frame that people
are still comfortable with.

But you go further back,
go, say, back thousands of years

when much of North America
was covered by ice,

a very different world.

But go further back yet.

Go back to 100 million years,

and this world would have
been entirely unrecognizable,

would have been
like going to another planet

and seeing life forms
that were, for the most part,

utterly alien to our experience,

and this is really difficult
to grasp.

NARRATOR: There is little
about the planet of the Triassic

we would recognize.

The continents we know today
had not yet formed.

They were all contained
in one huge land mass

surrounded by water--Pangaea.

Most of Pangaea was dry,

with blazing hot summers
and cold winters.

From Triassic period rocks,

scientists know much
of the interior was desert.

Fossilized plant remains tell
them that closer to the sea,

there were open,
fern-filled woodlands.

It was here,
along with the dinosaurs,

that the first crocs evolved.

In the beginning,

they were even more successful
than the dinosaurs,

and to our eyes,
they look totally bizarre.

ANJAN BHULLAR: Well,
the Triassic was, in many ways,

actually the age of crocodiles,

and in any Triassic landscape,

you would have seen
this vast diversity

of crocodile relatives
with many body forms.

My name is Bhart-Anjan Bhullar.
I go by Anjan.

I'm a paleontologist,

and I would say that I am
a historian of life.

NARRATOR: Anjan Bhullar
has been unearthing the bones

of the very first
crocodile relatives.

Two of them were found together

near some sandstone cliffs
in southern Utah.

BHULLAR: Well, these are
two of the most extraordinary

skeletons from the crocodile
line that have ever been found.

This large animal here
is something called a Poposaur.

It is the only complete skeleton

of one of these animals
that's ever been found.

All of the subtle features
on it, I mean, it's just,

it's the find of a lifetime.

These animals show us
what crocodiles were like

at the beginning
of their evolution,

and they're
very, very different.

The extraordinary thing
about this animal

is that it was really trying
to be a dinosaur

before dinosaurs were dominant,

in that it was actually
walking around on two legs.

You see how large
and how heavily built

the legs of this animal are

compared
to these tiny little arms.

And so, this animal couldn't
rest any of its weight

on its arms.

NARRATOR:
Poposaurus was a fierce,

fast-moving land predator,

acting for all the world
like a dinosaur.

And it wasn't the only
strange Triassic croc

to be found in Utah.

BHULLAR: In fact, the Poposaur,
this large skeleton,

was the first thing we found,

and we dug out
this big skeleton.

Then right underneath it
was a tiny foot.

And underneath that foot
was this animal here,

which is the only
complete specimen

of what we call
a sphenosuchian-grade

stem crocodile
that's ever been found.

NARRATOR: They called
the sphenosuchian "Little Foot."

It was even stranger
than Poposaurus.

BHULLAR: And so, the Poposaur is
something like a mountain lion,

whereas the sphenosuchian,
you look at this animal,

and it's got
a slender little body,

it's got extraordinarily
long legs,

extraordinarily long arms,

and these arms
were taking its weight,

unlike those of the Poposaur.

And so this thing was built
almost like a greyhound

with a heavy head
and a long tail.

It was an animal that was
utterly built for speed.

♪

NARRATOR: It's hard
to imagine an animal

less like the lumbering,
heavy-set modern crocodiles.

How did Anjan even know
they were related?

BHULLAR:
There are many features,

subtle features of the skeleton

that tell us it's actually
from the crocodile line.

NARRATOR: One tell-tale clue

is the structure
of the feet and ankles.

Another is in the skull.

BHULLAR: Among
the crocodile relatives,

there are
a few iconic features.

One of those
is the heavy reinforcement

of the skull bones,
especially the jaws.

These animals had strong skulls
and a very powerful bite.

NARRATOR: By comparing
details like these,

scientists can figure out

if fossils are related
to each other

and arrange them
on a family tree.

BHULLAR: As our ways of thinking
about evolution have improved,

we've realized that instead of

a sort of general
overall similarity,

we should really be focusing
on unique shared characters.

NARRATOR: If two fossils
share unique characteristics,

the odds are that they once
shared a common ancestor, too.

BHULLAR: This spread
on the table in front of me

encompasses more than
220 million years of evolution.

And in fact,
if I look at this group,

I can actually start to see
that a couple of these animals

share that reinforced
skull form.

NARRATOR: That tells Anjan
they belong

in the crocodile line,

whereas other fossils,
superficially similar, don't.

BHULLAR: These fossils actually

have a much
more lightly built skull,

almost a bird-like
lightly built skull,

so these two don't pertain
to the ancestry of crocodiles.

NARRATOR: By focusing on details
like ankles and skulls,

scientists can build
a family tree of crocs

and reveal the twists and turns
of their deep time history.

The strange creatures
of the Triassic were part

of the first great flowering
of the crocodile family tree,

but 200 million years ago,

much of that tree
was cut back...

[rumbling]

...when a mass extinction

wiped out the vast majority
of the animals of land and sea.

As the supercontinent Pangaea
began to break up,

volcanoes pumped vast amounts
of carbon dioxide into the air,

acidifying the oceans.

The planet warmed,
and habitats were transformed.

Most of the Triassic
crocodile relatives,

including Poposaurus
and Little Foot, died out.

SUES: Extinctions are
of great interest

to evolutionary biologists

because they basically
reset the evolutionary game.

We know that organisms,
over time,

try to adapt to particular
ecological circumstances,

however, every once in a while
during the history of life,

there have been catastrophic
events of such magnitude

that thousands or millions
of species were wiped out

in what basically
in deep time is a single moment.

NARRATOR: There have been
five major extinctions

in Earth's history.

Through the lens of deep time,

we can see they caused
profound destruction

and changed the history
of life on Earth.

The mass extinction
that ended the Triassic period

ushered in a new chapter
in the story of crocs.

In the Jurassic and Cretaceous
periods, crocs flourished again,

but in new
and even stranger ways.

A record of those wondrous
creatures is preserved

in one of the most spectacular
landscapes on Earth--Patagonia.

♪

DIEGO POL: After the Triassic-
Jurassic extinction event,

many groups diversified
in the Jurassic.

Dinosaurs were certainly
the most conspicuous

because they were big
and they were very abundant,

but other groups
began to diversify

in a very, very impressive way,
and crocs were one of them.

I'm Diego Pol.
I'm a paleontologist.

I work here in Patagonia
in the eastern coast,

in the southern tip
of South America,

and I study crocs.

I really love to drive,
you know, in places like this

because it's really like
you are driving through time.

NARRATOR: For the duration

of the Jurassic
and Cretaceous periods,

almost 150 million years,

crocs vied with dinosaurs
for dominance.

They stopped being
only the land animals

they were in the Triassic

and experimented with
radically new ways of being.

POL: So, the Triassic is over.

We're moving into the Jurassic,

and dinosaurs were evolving
and diversifying,

but also crocs were diversifying
at the same time.

You start seeing animals
like Dakosaurus,

is the swimming marine croc
that adapted their forelimbs

into paddle-like flippers.

And then you have
freshwater gigantic crocs

like Sarcosuchus
that's about 12 meters long.

It was eating dinosaurs.

And then you have herbivorous
crocs like Notosuchians.

Look at this animal.

It, it really
looks nothing like a croc.

It has a short snout, very high,

the eye sockets
are pointing to the sides,

and the, the crazy, crazy thing

is that it moved the lower jaw
back and forth.

And this was a way

of the upper teeth
and the lower teeth

to slide against,
against each other,

and in that way, this animal was
processing the plant matter.

NARRATOR:
So, here was an ancient croc

that chewed like a goat.

Diego has spent
much of the last 20 years

excavating ancient crocs

from the barren outcrops
of Patagonia.

But back when
those creatures lived,

the world was
a very different place.

The continents were forming,
and it was hot.

POL: It was much warmer planet.

There were no ice caps
on the poles.

There was, uh, a time

when conifers
dominated the ecosystem.

NARRATOR: In the warming
greenhouse world

of the Jurassic and Cretaceous,
crocs prospered.

This was their golden age.

POL: They became so diverse

that in some places you go, and
you basically only find crocs.

So, we can see a really,
really crazy diversity

in the Cretaceous.

And then about
66 million years ago,

it all went away.

NARRATOR: What happened
to the many Cretaceous crocs?

It seems most of them perished
the same way as the dinosaurs.

SUES: It was long realized that
around 66 million years ago,

there was a major extinction
of animals and plants

on land and in the oceans.

On land, the most famous
casualty were the dinosaurs.

[crash]

NARRATOR: Scientists agree
that an asteroid strike

brought on
the global devastation,

but many now argue
it was not the only cause

of the mass extinction.

From the fossil record, they can
see that climate changes

were already pushing
many species to extinction

before the asteroid impact.

SUES: So basically,
this impact is sort of thought,

if not the sole cause
of the extinction,

certainly the coup de grâce
for a great many lineages.

[growls]

NARRATOR:
Ancient crocs were reduced

to a fraction
of what they once had been.

POL: So, out of
this wonderful diversity,

only a few species
made it through.

And the ones that actually
made it through

were very particular
in many ways.

They were certainly adapted

to living
in the freshwater environment.

They were adapted to, uh,
feeding in water.

They were predators.

They were not herbivores.
They were not land crocodiles.

They were not marine crocodiles.

So only a tiny fraction of
that diversity made it through.

NARRATOR: The crocodiles
that made it through

were the shoreline predators

that lived half in water
and half on land.

Their low, tank-like body plan

may have been one secret
of their survival.

It allows them to lie
semi-submerged in the shallows

and ambush their prey
with ferocious speed.

[splash]

The success
of that lethal design

is why crocodiles today
all seem so similar.

HEKKALA: So, crocodiles
have this form

that's very, very successful.

They have sort of an armored
body plan that allows them

to be a successful predator
in aquatic environments.

Aquatic environments
can be more stable

than other kinds
of environments,

like terrestrial environments,
and so it makes sense

that they've retained
this body plan from deep time,

from the ancestral crocodilians

that were around the globe
millions of years ago.

It works really well.
Why change it?

NARRATOR: Of course,
that classic body plan

is no guarantee of survival.

The horned croc of Madagascar
died out just centuries ago,

likely pushed out
by the giant Nile croc.

Results from Evon's work

suggest the species
are more closely related

than anybody realized.

♪

It's a great example
of how DNA analysis

has become a vital tool
for paleontologists.

♪

HEKKALA:
One of the exciting things

about the new tool kit
we have today,

the ability to use DNA
to look at evolutionary history,

is we can use it
as sort of a metric

for change over time
and lineages.

So, with living species,
we can take their DNA

and we can calculate back
how long it takes

to accumulate the number
of changes we see in the genome.

And we can say
this corresponds to a split

three million years ago
or six million years ago

or 20 million years ago.

NARRATOR: DNA has shown that
both crocodiles and alligators

are descended
from a common ancestor

that lived 80 million years ago.

HEKKALA: The ancestral lineage

that the true crocodiles
came from

diverged from the group that
includes all the alligators

about 60 to 80 million
years ago.

And then, even more recently,

this thing
that we've always thought

as the sort of primordial
crocodile, the Nile crocodile,

we recently have found,
using molecular clock dating,

that the Nile crocodile
is just a baby.

It just arose probably

within the last four
to six million years.

It's a young'un on the landscape

of, uh, crocodilians
in the modern world.

NARRATOR: So, despite their
prehistoric appearance,

it turns out that over
their 230-million-year history,

crocodiles have been
in constant evolution.

They have proved themselves
to be one

of the most resilient lineages
on the face of the planet.

HEKKALA: For me, these
crocodiles sort of represent

an organism that, through
the history of life on Earth,

it's found a way to persist.

NARRATOR: The story
of the crocodile lineage

is of deep time transformations

that produced a wild diversity
of croc species,

followed by a steep decline.

Today there are just
a handful of crocs,

and the strange animals that
gave rise to them are all gone.

The surviving crocs
are all very similar,

all shoreline predators
of the tropics.

But while the crocodile lineage
has bottlenecked,

another lineage is experiencing
a wild explosion of diversity.

[squawking]

♪

♪

[cawing]

[honks]

[quacking]

[honking]

Birds have colonized
every environment on Earth.

And they come
in an astonishing variety

of shapes, colors, and sizes.

[whistling]

JULIA CLARKE: There are
more species of birds

than any other group of
vertebrates that lives on land.

♪

They can cross
the Himalayas on wing.

They can dive into a part
of the ocean

where sunlight does not reach.

They can migrate
between continents.

So, they are truly remarkable.

I'm Julia Clarke,

and I'm a professor
of vertebrate paleontology

at the University of Texas
at Austin.

[ducks quacking]

Well, I think
the captivation of birds

is that they have
this intelligence

that we don't really understand.

It's sort of like this foreign
or alien intelligence

that is in our everyday spaces,

which is the premise of, like,
a lot of sci-fi movies,

if you think about it,
you know, they're among us.

And, if you look closely,

I think there's a lot
to be fascinated with,

even in everyday birds.

NARRATOR: Birds have colonized

not only the natural
environments of the planet,

but also the urban spaces
created by humans.

CLARKE: There are more than
10,000 species of birds,

but even more striking
than that,

there are more
than half that number

is just within one lineage,
songbirds,

so that means that the birds
that are in your backyard

are part of what is truly
an extraordinary evolution.

NARRATOR: So, what's the story
behind the spread of birds

across the planet?

How did they come to be
everywhere and so diverse?

CLARKE: Things that can
seem so commonplace,

crows or pigeons in a park,

are the leavings
of an amazing history

that stretches back hundreds
of millions of years.

NARRATOR: Our understanding
of that evolutionary history

began with one
extraordinary fossil

discovered in the 1860s
in Germany--Archaeopteryx.

CLARKE: This fossil,
to many people,

might just look like roadkill

or something
that hit your window.

But in fact, to me, these bones,
they come to life.

And the wings are moving,

covered in feathers, but
with mobile claws at their tips.

Most striking is a long,
bony tail with feathers.

NARRATOR: 150 million years old,
archaeopteryx was a bird.

It had feathers,
and it could fly.

But with its claws, tail,
and toothed beak,

there was something
almost dinosaur-like about it.

It led proponents
of the new theory of evolution

to make a sensational claim:

Birds must have evolved
from dinosaurs.

CLARKE: When I look at this,
I see an icon of evolution.

It was one of the first key
and totally unavoidable

pieces of evidence
consistent with evolution.

NARRATOR: But the theory that
birds evolved from dinosaurs

met intense opposition.

How could something
so huge and heavy

evolve into something
so small and light?

One of the biggest objections

was that no dinosaur had ever
been found with a wishbone,

in birds, the crucial brace
for the chest

that makes flight possible.

The search was on.

If scientists could find
a dinosaur with a wishbone,

they would clinch the case.

But for a century, they failed.

♪

Then, in the 1960s,

paleontologist John Ostrom
hit pay dirt...

a dinosaur fossil
with a wishbone.

He called it Deinonychus,
terrible claw.

JACQUES GAUTHIER: Here we have
Deinonychus antirrhopus,

the fossil that changed
everything that we know

about the origin of birds

and fundamentally altered

our understanding

of how flight evolved.

NARRATOR: Deinonychus
was a ferocious predator

with wing-like arms
and all the bones and muscles

necessary for flight,

but it couldn't fly.

GAUTHIER: Here's an animal
with forelimbs

much too short
and much too heavy in the body

to be able to fly,

yet it has
all the bells and whistles

that we associate
with the flight stroke.

[squawking]

NARRATOR: Not only that--
it had feathers, too.

But all this had nothing
to do with flight.

Its feathers were for warmth,

and its clawed wings
were for killing.

[squawks]

GAUTHIER: The arms
up against the body

and shoot it down and forward,

grab your prey,
drag it up and back.

Down and forward, up and back,
down and forward, up and back.

That's the flight stroke.

So, all the details, the basic
architecture, at least,

of the flight stroke
is evolved in an animal

that is not using it to fly.

NARRATOR: Amazingly,
these tools built for killing

would eventually power flight.

[squawks]

GAUTHIER: So, you have feathers

and you have the flight stroke
colliding in one animal,

so the skies
were no longer a barrier

to the evolution of dinosaurs.

And that's why we think
that birds are living dinosaurs.

NARRATOR: Deinonychus
was powerful evidence

that dinosaurs
gave rise to birds.

But the many stages of that
evolution were still unknown.

To complete the story,
scientists needed more fossils.

Another long wait began.

♪

Then, in the 1990s,

farmers in a remote province
of northeastern China

blew the story
of bird evolution wide-open.

[clucking]

They had been turning up rocks

with the outlines
of birds in them

for as long
as they could remember.

They had no idea these were
the bird/dinosaur fossils

scientists had been waiting for.

By the late 1990s,

fossil fever had broken out
in Liaoning Province.

[man speaking Chinese]

[rooster crows]

NARRATOR: A single fossil
could bring a year's income.

As farmers
scoured the landscape,

the fossils
started to pour in,

hundreds of ancient birds
from the time of the dinosaurs.

JINGMAI O'CONNOR: Bird fossils
are extremely rare,

typically, in the fossil record.

And up until the eighties,

all we really
had was Archaeopteryx.

So, without anything in between

this bird that looks very much
like a dinosaur

and birds that look very much
like living birds,

without any fossils
to fill in this gap,

we had no idea
how the modern bird evolved.

But the fossils
from Western Liaoning

started to show us
the transitional forms.

They showed us
the earliest birds with beaks,

the earliest birds with
short tails, like living birds.

My name is Jingmai O'Connor,

and I am a vertebrate
paleontologist.

You know, I have a very strong
personality, a bit unusual,

well, at least for a scientist.

To be honest, my bird obsession
grew with my studies.

I've developed
this deep fascination and love

for these, this incredible group
of animals.

NARRATOR: Jingmai's obsession
with birds was cemented

by the fossils of Liaoning.

They are priceless.

Bird fossils are extremely rare

because bird bones
are so delicate.

But here in northeastern China,
130 million years ago,

a unique combination
of circumstances

created the perfect conditions
for their preservation.

O'CONNOR: If you were able
to come back here

131 to 120 million years ago
and looked out,

you would have seen lakes
as far as the eye could see,

with active volcanoes
going off around them

and a forested environment

growing by the shores
of these lakes,

and this forest
would have been teeming

with small feathered dinosaurs.

[rumbling]

NARRATOR: As those small
feathered dinosaurs died

and fell or were washed
into lakes,

they were quickly buried
in layers of volcanic ash.

♪

The result?

An extraordinary record
of Cretaceous bird/dinosaurs

perfectly preserved in stone.

O'CONNOR: The amazing thing
about these fossils

is the exceptional preservation
of soft tissues

which reveal
these extinct animals

in a level of detail
that we paleontologists

never previously
thought possible.

NARRATOR: Fossilized along with
the birds were plants and seeds,

allowing scientists
to reconstruct

the forested environment
of the time.

Together, the wealth of Liaoning
fossils reveal a world

where creatures
representing every stage

of dinosaur-to-bird evolution
lived side by side.

They show how nature
experimented

with every aspect of what
would finally make a bird--

beaks, wings, feathers,
and flight.

Here was a sort
of evolutionary laboratory

in which many
different combinations

of dinosaur and bird
characteristics were tried out.

There was Caudipteryx,
a small feathered dinosaur

that had wings but couldn't fly.

O'CONNOR: You can see,
with its very robust hind limbs

and its very small forelimbs,

this was definitely
not a flying dinosaur.

NARRATOR: Living alongside it
were creatures that flew

but still had many
dinosaur characteristics--

teeth, long tails,
and claws on their wings.

O'CONNOR: Here we have a
primitive bird named Jeholornis.

It has lost
almost all its teeth.

It has a shoulder girdle

that looks almost like that
of living birds,

but then it has this tail

that is actually longer
than that of Archaeopteryx.

♪

NARRATOR: And there were
creatures like Confuciusornis,

almost identical
to modern birds.

O'CONNOR: If you were
in northeastern China

during the early Cretaceous,

you would see flocks of
Confuciusornis flying overhead.

NARRATOR: The feathered
dinosaurs of Liaoning

are a reminder that evolution

does not move
in a straight line.

SUES: There's
a common perception

that evolution proceeds
in a very linear fashion.

So, you have a little dinosaur

that somehow decides, quote,
unquote, to become a bird.

But actually,
the many bird features

were gradually acquired.

There were a lot of dead ends
in this evolutionary process.

[squawking]

NARRATOR: Just like Deinonychus,
the Liaoning fossils show

that wings and feathers
evolved separately

and for reasons that have
nothing to do with flight.

[squawks]

It was only
after millions of years

that these things came together

to make the creature
we call a bird.

O'CONNOR: In fact,
what we've learned

from this huge diversity
of fossils

is that these features that
we associate with modern birds

actually evolved multiple times.

And I'm not only
talking about flight,

I'm talking about beaks,

I'm talking about
the abbreviated tail.

NARRATOR: The Liaoning fossils
opened a window

on the profusion
of feathered dinosaurs

that populated the whole world
many millions of years ago.

What happened to them all?

Most died out
in the same extinction event

that killed the big terrestrial
dinosaurs and most crocs.

[crash]

But like the crocs,
a few birds squeaked through.

Those few survivors gave rise
to all the birds on Earth today.

[honking]

But how did that amazing story
of survival play out?

Remarkably, scientists
are solving that mystery

not from bones, but from DNA.

ERICH JARVIS:
So, what happened is

that this mass extinction
occurs,

maybe as a result

of a big, giant meteorite,

then climate change
and so forth.

A few groups of birds survive,

only five percent
of the species survive.

My name is Erich Jarvis.

I'm a professor
at the Rockefeller University

in New York.

I study how the brain
produces learned behaviors,

specifically like language.

[chirping]

JARVIS: See, that's a call.

NARRATOR: Erich is
especially interested

in how bird songs evolved.

But songs don't fossilize.

So, along with other scientists,

Erich hoped the answer
might come from genetics.

JARVIS:
And we all wanted to know,

is the bird family tree
correct?

Because there are many papers
that were coming out,

changing the tree
from one year to another,

and it keeps screwing up
our experiments, basically.

NARRATOR: It was
an international consortium

of scientists working to
pin down the avian tree of life.

And in the process, they would
answer the big question--

how did the birds
that survived the asteroid

go on to take over the planet?

Erich and his colleagues
compared the genomes

of different bird species

to calculate
their degrees of similarity.

They could then figure out

when they last shared
common ancestors.

JARVIS: Fossils
is anatomical structures

with shapes, of course,

and that anatomical structure
you can measure,

you can quantify
the volume, the size,

the shape, and so forth

and use that information
to infer relatedness,

whereas the genome is
pieces of DNA, the genetic code,

that you can also use
to infer relatedness.

The genome has millions,
hundreds of millions

of pieces of information
in the sequence.

Which one is more accurate?

Most people trust the DNA
to be more accurate.

NARRATOR: DNA sleuthing
can't replace the work

of paleontologists with fossils,

but it made for a big break

in the case
of recent bird evolution.

It showed that
just a handful of birds

survived the mass extinction
to give rise

to the amazing diversity
of birds today.

JARVIS: First thing
we figured out

is that those ones
that survived,

with the deepest branches
in the tree that we generated,

were the ones
that were shorebirds,

that can survive in water,
that can survive in land,

that can survive
in different habitats.

NARRATOR: Along with shorebirds
like ducks and geese,

the ancestors of ostriches
and emus also survived.

JARVIS: Then those few four
or five lineages that survive,

in a 15-million-year window,

gave rise to every species that
we are looking at now today.

NARRATOR: How exactly did
that small group of survivors

give rise to modern birds?

Scientists are still
working that out.

CLARKE: I think that why
birds are so species-rich

is a big question,

and it's not one that's
going to be easily answered.

There's so many innovations
that have been proposed

to explain this incredible
number of species we have today.

And some of them are,
of course, flight.

And some of them are
rapid growth to adult-size,

so baby birds grow
to full-size superfast.

Other strategies are things
like bright colors

or complex color patterns,

complex modes of communication
that can be deployed

in attracting a mate
or defending a territory.

These kinds of behaviors
are thought to be linked

to rapid speciation rates.

So, these are all
big, open questions,

and there is, as yet,
no simple answer.

NARRATOR: Whatever the reason

for the amazing diversity
of birds,

scientists are finally
in a position

to see the whole vast
avian tree of life.

Arising with the dinosaurs,
the bird lineage experimented

for millions of years
with feathers, beaks, and wings.

It barely survived
a major extinction event

before finally flowering

in the 10,000 species
alive today.

[honking]

But while the bird lineage
exploded

and birds colonized
every habitat on Earth,

another lineage concentrated
on colonizing just the seas.

♪

No animal embodies
the beauty and awe of the seas

more than whales.

[whale singing]

What science now knows

about these leviathans
of the deep is amazing.

[singing]

Bowhead whales can live
for up to 200 years,

longer than
any other mammal on Earth.

Sperm whales can dive to depths
of over 3,000 feet

and stay underwater

for an hour and a half
without breathing.

Blue whales
are the biggest creatures

to ever have lived on Earth,

bigger than even
the largest dinosaurs.

♪

Up to 100 feet long
and 200 tons in weight,

they have a heart
the size of a small car.

And these giants of the deep
sing to each other,

communicating over vast
distances in a language of song

that researchers
still don't fully understand.

It's just one
of the many mysteries

still surrounding whales.

JACKIE HILDERING: What I've
learned more than anything else

as a scientist
is how little we know.

There's this presumption
that we know so much.

We don't.

I'm Jackie Hildering.

[camera shutter clicks]

I'm a whale researcher
and educator.

♪

[whale blows]

[laughs]

Mom and calf,
Obsidian and Ripple.

Yes, yes.

[clicking]

It's mind-blowing to see
the number of humpbacks here,

considering what a rarity it was
to used to see them.

[whale blows]

And I'm trying to figure out
who they all are.

And this is... [click]

Claw.

It's a female. She's had a baby.

NARRATOR:
Jackie has been working

with the humpback whale
population

off northern Vancouver Island
for almost 20 years.

She knows each of them
individually

by the distinctive marks
on their tail flukes.

HILDERING:
What I can't express properly

is what it feels like
to know who they are.

That the one that just went by
I've known since he was a calf

and was here
with his mother in 2007.

NARRATOR: With others,
Jackie is working to understand

humpback family groups
and their epic migrations.

Every year, they swim
up to 6,000 miles,

mating in the warm waters
of the equator,

feeding in the cold food-rich
waters nearer the poles.

How did these gargantuan animals

and their remarkable behavior
evolve?

For so long, it was a mystery.

MARK UHEN: We've known
that whales are mammals

since the 18th
and 19th centuries

because they're warm blooded
and they suckle their young,

but we didn't know
where they came from.

I'm Mark Uhen, and I work
at George Mason University,

and I study the evolution of
whales and other marine mammals.

[click]

[click]

[click]

Darwin talked
about the origin of whales

in his classic book
"The Origin of Species,"

where he said someone he knew

had observed a bear
swimming around,

skimming insects
off the surface of the water,

and he suggested that perhaps
something like a bear

could have evolved into a whale,

the kind of whale
that filter-feeds

by doing something similar

and getting better
and better at it over time.

Now, Darwin was not correct
about that,

but at least he could
conceptualize of a way

that whales had evolved.

But basically, we didn't know
where whales came from

until extremely recently.

NARRATOR: The fascination
with whale evolution

began in the 19th century.

Stories of sea monsters filled
the popular imagination.

When the first fossil whale
was unearthed,

its discoverers thought they'd
found a gigantic sea serpent.

It was called Basilosaurus.

UHEN: It was discovered
in North America

along the Gulf Coast
in the 1830s,

and it was actually
the first fossil whale

ever to be scientifically
named and studied.

The gentleman who named it,
a man named Harlan,

had read about
large sea serpents

being discovered elsewhere
in the world,

and so he thought
that this was something similar,

and thus he named this animal
Basilosaurus,

which means king lizard.

NARRATOR: Up to 50 feet long
with ferocious teeth,

Basilosaurus was
a formidable marine predator.

Finally, in 1841,
it was identified as a whale

and dated
to about 35 million years ago.

For almost a century
after its discovery,

Basilosaurus remained
the oldest known whale.

It was assumed to be the
ancestor of all living whales.

UHEN: So, after the
discovery of Basilosaurus,

there were other whales found

that were just a little bit
earlier and more primitive,

but not by very much,

maybe five million years
older than Basilosaurus.

And it didn't push the origin
back in time,

and we really didn't
discover a whole lot more

about the origin of whales.

NARRATOR: One of those other
early whales was Dorudon,

a little bit smaller
than Basilosaurus.

It would turn out to play
a bigger role in whale evolution

than its discoverers imagined.

But where did
those early whales come from?

They must have evolved
from something, but what?

The deep origins of
the whale lineage were a mystery

until 1975,
when a paleontologist went

on a fossil hunting expedition
to Pakistan.

He wasn't looking
for early whales at all.

PHILIP GINGERICH:
I was interested

in how archaic mammals
changed into modern mammals.

Things like the first horses,
that's what I was interested in.

My name is Philip Gingerich.

I'm a professor emeritus
of paleontology

at the University of Michigan.

I took several students with me
and colleagues from Paris,

and we looked first
in Punjab Province,

then south in Sindh.

We still hadn't found anything
very interesting.

And we went to the Northwest
Frontier Province.

And there, high on a hill,

we found a little jaw
of a land mammal.

NARRATOR: Later they found
a piece of skull,

and its strange ear bones
finally unlocked the secrets

of early whale evolution.

GINGERICH: This is what was
left, the back of a skull,

and if you look
at the underside,

it has the covering
of the ear on the right side,

and that covering is missing
on the left side.

NARRATOR: Those ear bones
turned out to be the key.

Philip thought he was looking
at the skull of something

like a primitive deer,

but it unmistakably had
the ear bones of a whale.

GINGERICH: Whales have
a special structure of the ear

to be able to hear in water.

It turns out that they
effectively see in water

by using sound,
and so to do this,

the ears have become modified.

[whale singing]

UHEN: The ear bones of whales
are very dense,

and that density helps them
to hear sound in the water.

Mammal ears originally evolved
in terrestrial animals,

and so their structure
is optimal for hearing in air.

And in water, sound behaves
really differently.

So, for example, if you go
into a pool or under a lake,

you can hear sound,
but it's a little muffled,

but the one thing you can't do
is you can't figure out

where the sound
is coming from around you.

And that's because
the way mammals do this

is they use
the difference in time

between when a sound hits
your right ear and your left ear

to figure out what direction
the sound is coming from,

so if the sound
is off to my right,

it hits my right ear first,
then my left ear,

and so my brain says,
"The sound is over to my right."

But in water, the tissue
of your face and skull

is about the same density
as water,

so the sound, rather than going
around my skull to my left ear,

goes right through it,
so it gets to my left ear

at almost the same time
as my right ear.

And I can't tell where the sound
is coming from.

So, the added density
to whale ears,

that's reestablishing
their ability

to hear directionally
underwater.

NARRATOR: Philip's fossil
had that same distinctive ear,

and it was 49 million years old.

That could only mean one thing--

here at last was one
of the very first whales.

Philip named it Pakicetus.

GINGERICH: Once we knew
it was a whale,

we knew it was the oldest whale
anyone had ever found.

NARRATOR: Pakicetus pushed
the origins of whales

back 15 million years

to the time
when the Indian subcontinent

was slowly crashing into Asia.

Where Pakicetus was found
was once an ocean shoreline.

Its ears made it clear
Pakicetus spent time underwater,

but other fragments of skeleton

also clearly showed
it walked on four legs.

How did this strange beast

give rise to the giants
we know today?

♪

At the Museum of Natural History
in Paris,

one of the birthplaces
of paleontology,

they have been assembling the
skeletons of prehistoric animals

for over 200 years.

They now have one of the few
complete reconstructions

of the extraordinary whale
ancestor, Pakicetus.

CHRISTIAN DE MUIZON: You see
it's a quadrupedal animal

with the higher forelimbs
and hind limbs.

It means that this animal was,

uh, definitely
partly terrestrial.

I am Christian de Muizon.

I'm a paleontologist working

at the Natural History Museum
in Paris.

And obviously
it's quite a strange animal,

very small,
doesn't whale-looking at all.

It more looks like a dog
with a long snout.

NARRATOR: Pakicetus is one
of the strangest surprises

of evolution, a whale ancestor

that looks like a small wolf
with webbed feet for swimming.

GINGERICH:
The key thing about it

is it has elongated
finger and toe bones,

so, clearly,
it's already semiaquatic.

[sniffing]

NARRATOR: Pakicetus was
a creature of the shoreline,

hunting for fish
and perhaps other small animals

in the shallows.

UHEN: And we think that
it was using its longer snout

to probe for aquatic prey
in the water,

and so it was feeding
in the water

while almost certainly
going out on land

to breed and have their young.

NARRATOR: Once they adapted
to life in the shallows,

it took ten million years

for the descendants of Pakicetus
to become fully aquatic.

Why did it take so long?

Because to live underwater,
they had to change.

It is one
of the most remarkable stories

of total physical transformation
in the annals of evolution.

[whale singing]

UHEN: After Pakicetus,

whales take
about 10 to 12 million years

to evolve
into fully aquatic forms.

And during that time, their
hind limbs tend to get smaller

and their skulls
tend to get longer,

and the naris, which is the hole
in the skull where the nose is,

moves up the skull.

In addition, their forelimbs
tend to turn into flippers,

and they get more vertebrae
in their back,

which makes their bodies longer.

NARRATOR: When Basilosaurus
arrived on the scene

35 million years ago,

along with its
evolutionary cousin, Dorudon,

there'd be no mistaking
that these were whales

that lived their whole lives
in water.

But there was still
one great transformation

to take place in whales--

baleen feeding.

CARLOS PEREDO: So, near the base
of the whale family tree,

there's this major split

into the two groups
that we have today.

We have toothed whales,
and then we have baleen whales

that actually
lose their teeth entirely,

and they grow
what are called baleen plates

that are made of keratin,

so they're actually more like
hair or fingernails.

And these whales use it
to filter their food,

so they'll take
big gulps of water,

and they'll actually
filter their prey,

little tiny microscopic
organisms out of that water

using the baleen plates.

♪

NARRATOR: The split into toothed
whales, like orcas and dolphins,

and baleen whales,
like blue whales and humpbacks,

happened about
30 million years ago.

It turns out it occurred
in the descendants

not of Basilosaurus
but of Dorudon.

UHEN: Basilosaurus
is sort of a sideline.

We don't think it gave rise
to anything alive today.

NARRATOR: The toothed whales
remained,

like their ancient ancestors,

predators living mostly
in coastal waters.

There they could feed on fish

or, like some of the orcas,
seals and baby sea lions.

♪

The baleen feeders underwent
a much greater transformation.

With a radically new way
of filter-feeding,

they moved into the deep oceans
and became huge.

Why?

For a long time,

the massive size of
some baleen whales was a puzzle.

[blowing]

But it turns out
that in the ocean,

great size is an advantage.

UHEN: If you look at the energy
budget of these animals,

they use fewer calories per unit
body mass when you get bigger,

and so they're more efficient
when they're huge.

They're also more efficient
when they move,

when they swim
at large body size,

so there's advantages
to being large in the ocean.

[blowing]

NARRATOR: The huge size
of baleen whales is also linked

to one of the last great
planetary transformations.

PEREDO: Argentina
and South America

become completely separate
from Antarctica,

and that changes the currents
in the ocean system,

and it seems to really have
a profound impact

on what whales are doing.

NARRATOR: The cold current
that began to circle Antarctica

led to a vast upsurge
in the krill population

that baleen whales feed on.

With large amounts of food

and the efficient baleen
filter-feeding system,

there was simply nothing
to stop baleen whales

from becoming huge.

[blowing]

UHEN: It was suggested early on

that the reason that terrestrial
mammals can't be that big

is because of gravity.

Anything much bigger
than the largest mammals

we see in the fossil record

would be crushed
due to the force of gravity,

like their limbs
couldn't hold their bodies up.

But whales are approximately
neutrally buoyant,

and so gravity
doesn't affect them.

And so freed
from that constraint,

the baleen whales keep getting

bigger and bigger
and bigger over time

because the largest ones
are the most efficient.

[whale grunting]

NARRATOR: Along with baleen,
whales have developed

sophisticated fishing behaviors
to trap their prey.

Humpbacks rely
on the help of gulls.

[squawking]

HILDERING: And what's happening
is the diving birds

are forcing the herring
together, that form a huge ball,

that gives the gulls
at the surface

a chance
to propel themselves down

and try to grab a herring,

and then somehow
the humpbacks know

that there's a concentration
of feed there.

And they come with
their huge mouths, gulp it down,

get rid of the salt water
through their baleen,

and swallow.

[camera shutter clicking]

NARRATOR: Jackie's work
has led her to marvel

at the delicate web
of relationships

linking humpbacks to every
aspect of the marine ecosystem.

HILDERING: It's perfection.

It's been going on
longer than we can understand.

Knowing whales keeps me in a
state of humility and mystery...

which I think is how
a human life is well lived.

It makes me feel connected.

It makes me feel appropriately
small in the presence of giants.

[whale singing]

NARRATOR:
Over millions of years,

whales grew huge
as they explored the seas,

but another mammal grew huge
as it explored the earth,

evolving its own remarkable
tools for life on land.

[roars]

♪

[trumpets]

♪

For millennia,
these stately creatures

have patrolled
the African savannas,

transforming the land
as they go.

♪

♪

♪

PAULA KAHUMBU:
We're driving along tracks

that the elephants have made.

Uh, they've been walking
on these trails

probably for hundreds of years.

They create paths that they
then use for generations.

♪

My name is Paula Kahumbu.

I'm an ecologist,
and I run WildlifeDirect.

It's a Kenyan-based
conservation organization

to really change hearts
and minds and the laws

to protect
our incredible wildlife.

♪

Elephants are
such extraordinary animals.

The more we learn about them,
the more we realize

that we actually are only
just scratching the surface.

Every new discoveries emerge

that elephants
can understand things

that we couldn't have
dreamed possible.

And I think we'll never
uncover their secrets.

NARRATOR: The intelligence and
memory of these enigmatic giants

is legendary.

[grumbling]

Their complex elephant mind
has allowed them

to evolve a social life
with many parallels to our own.

KAHUMBU: Elephants are
incredibly social animals.

They live in family groups.

And the family groups
will have everybody

from the grandmothers,
the daughters, the mothers,

the aunts, the cousins,
the nieces, the nephews,

everybody all together,

so huge range
of different-sized elephants

all walking together
and feeding together.

NARRATOR: Scientists have shown
that elephants communicate

through calls, touch, and even
low frequency vibrations,

which can travel
underground for miles.

But there's still a lot that
they don't fully understand.

KAHUMBU: It would be amazing

if we could actually uncover
what it is that they know.

I really think that we are
blundering about right now

because we don't
even have the tools

to measure how they communicate.

NARRATOR: And Paula is certain

that along with their ability
to talk to each other,

they experience many
of the same emotions we feel--

grief, anger, and empathy.

She senses
a mysterious inner life.

KAHUMBU: When you sit
with them for hours,

this, like,
wealth of sensations

just keep coming
and coming and coming,

and it just seems to be endless.

I feel like I can really sense

what is going on
with those elephants.

And the longer
I spend with elephants,

the more I feel
in tune with them.

NARRATOR:
As much as she admires them,

Paula is keenly aware that
elephants today are in trouble.

[roaring]

KAHUMBU: There used to be
dozens of species of elephants,

and now there are just three.

And if we're not careful,
we will lose them as well,

and that will be the end
of the lineage of elephants.

NARRATOR: Could the ancient
lineage of elephants

really be coming to an end?

How did these magnificent
animals go from myriad species

to just three today?

And how did
the ancient histories

of humans and elephants
become so intertwined?

[trumpets]

As with every lineage,

it's a story that begins
in deep time,

a story told by fossils,

most of them found
in the birthplace of elephants--

Africa.

♪

The deep origins of elephants

lie in the Turkana Basin
in Northern Kenya.

In a place called Buluk,
scientists are finding fossils

that point to a magnificent age
of elephants.

They reveal the ancient history

of the mammals with trunks
called proboscideans.

BILL SANDERS: This is from
the right side of the jaw.

Fossils are
the messengers of the past.

I believe that.

I think that we,
as paleontologists,

are trying
to be the interpreters

of the messengers from the past.

They give you
the opportunity to see

the kind of incredible journey
that elephants had to make

to become elephants.

It took 60 million years
to make an elephant.

I'm Bill Sanders.

I'm a paleontologist
at the University of Michigan.

I specialize
on studying the evolution

of proboscideans,
including elephants.

NARRATOR: Today, Buluk is one

of the hottest,
driest places on Earth,

but 17 million years ago,

it was a lush forest
with rivers and wetlands.

SANDERS:
It's a very wet climate.

It's a very equable climate,
very warm climate.

It's a great place
to be a browser.

It's a great place to go out
and look for vegetation,

a great place to go get a salad,
Africa in the early Miocene.

NARRATOR: How can scientists
reconstruct

those vanished environments?

It turns out ancient landscapes

leave traces
just like ancient animals do.

ELLEN MILLER: We often find
fossil wood and fossil seeds,

so that's telling us something
about the environment,

and, uh, the red sediments
around us are ancient soils,

they're actually
ancient floodplain deposits,

so the animals would have been
living out on these floodplains

in these forested areas.

I'm Ellen Miller.

I'm a paleontologist

associated with
the Turkana Basin Institute.

We're trying to reconstruct
the whole environment

that these animals
were living in.

If you go in
and just pick up the bones,

it's like, it's like
taking the chocolate chips

out of the cookies.

So, we work with geologists
and climate scientists

and isotope specialists and all
kinds of people, geochemists.

NARRATOR: The painstaking work
of Ellen and her colleagues

is allowing them to reconstruct

the whole vanished world
of ancient Buluk.

MILLER: So, if you were
to be transported back

to the early Miocene of Buluk,
17 million years ago,

it would have been
a mature meandering river system

and a woodland,

and there would have been
a whole host

of different kinds of elephants.

So, you would have had
the Deinotheres.

They're very, very primitive.

They're about a third or a half
the size of a modern elephant,

and they would have been kind of
snuffling along the riverbanks

because they seemed to really
like a closed canopy forest

and a wet environment.

But at the same time,

you have the Amebelodons,
the shovel-tuskers.

The lower incisors are these
big, long shovel-like tusks,

so they would have used them
to scoop up their dinner.

NARRATOR: As scientists
excavate, they are astonished

by the diversity of strange
beasts they are discovering.

♪

Ancient Buluk was a sort of
Jurassic Park of elephants.

ISAIAH NENGO: Imagine
I'm taking you on a safari,

but a safari back in time.

You'll be confronted
with these magical creatures,

a slice of Africa
that is now gone.

You'd be confronted here
with amazing herds of elephants.

♪

You have a herd of,
of Deinotheres.

You, you have a herd
of these elephant ancestors

called the Gomphotheres.

It would be mind-blowing
to, to, to confront this scene.

I think the Miocene
16 million years ago at Buluk,

that would have been
the center of the empire

of the age of the elephants.

[blows]

My name is Isaiah Nengo,
and I am the Associate Director

for the Turkana Basin Institute.

When you're out there
and you pick up a piece of bone,

you pick up a fragment of
a skull or you pick up a tooth,

and it, it strikes you that

"Man, I'm the first person
to ever look at this thing.

I am the first person
to know that this exists."

There's an immense joy.

There's, uh, there's
no way to describe it.

NARRATOR: The ancient elephants
here bear witness

to a glorious flowering
of the elephant lineage

about 17 million years ago.

But what were their origins,

and how did they come by their
magnificent tusks and trunks?

30 million years ago, there was
a species called Palaeomastodon.

It was probably
the first elephant ancestor

to actually look
like an elephant.

SANDERS: If you saw them
on the landscape,

you would say, "Yeah, that thing
is like an elephant."

They walk around
like a walking card table,

like elephants do today,

probably very carefully
with three legs on the ground

at any one time.

We believe from the shape
of where their nose is

and the anatomy around it,
they must have had a trunk,

which is very cool.

So, it's at 30 million years
of Palaeomastodons

that we begin to get
that framework for elephants,

the beginning of recognizability
for elephants.

NARRATOR: But where did
Palaeomastodon come from?

Beyond 30 million years ago,

the elephant fossil record
seemed to disappear.

For decades, the earliest
origins of the elephant lineage

were a mystery.

But then, in the 1990s, a French
paleontologist and his team

were excavating in an abandoned
phosphate mine in Morocco.

In layers dating
to 56 million years ago,

he came across fossil remains
of a mysterious animal

about the size of a small dog.

He called it Phosphatherium.

Later he came across fragments
of the jaws and teeth

of an older,
even smaller creature.

This one was no bigger
than a rabbit.

As he puzzled over both fossils,

he noticed something
very strange.

Their teeth seemed to be
miniature replicas

of an elephant's teeth.

The more he looked,
the more certain he became.

They must be
ancestral elephants,

the oldest ever discovered.

It was an astonishing
conclusion.

The oldest elephant ancestor
was the size of a rabbit.

[man speaking French]

NARRATOR: Emmanuel
brought his fossils

back to the Paris Museum
of Natural History.

Today he keeps them in
a filing cabinet in his office.

SANDERS: I give a lot of credit

to my colleague
Emmanuel Gheerbrant

because it's like
a detective story.

It's a real puzzler
to figure out what they are,

and he found these things,

and he started looking
at their teeth,

and he realized they had some
subtle features on their molars,

the arrangement of the cusps
on their molars

that said,
"I am a proboscidean."

NARRATOR: Finally, scientists
could see the very beginnings

of the elephant
evolutionary tree.

NARRATOR: It starts with
the tiny 60-million-year-old

creature with
the miniature elephant teeth.

Emmanuel called it Eritherium.

NARRATOR: So much of the story
of elephant evolution

can be told by teeth.

[grumbling]

NARRATOR: As elephants evolved,
incisors slowly became tusks.

[roars]

They helped those early
elephant relatives

browse in the ancient
African forests.

SANDERS: We see that they
have large front teeth,

and their jaw has grown
forward in their mouth

so that their front teeth
are a bit separated

from their back teeth,

so their front teeth
are specializing.

They're specializing
for grabbing food,

for acquiring food,
for nipping food,

for chopping food.

NARRATOR:
As incisors became tusks,

they took on the functions
they have in elephants today.

SANDERS: They're used
for acquiring food,

for knocking down plants
so you can reach food.

They're used for social display.

Tusks are the defining features
of elephants,

and it's like their behavior is
tied up in having these tusks.

NARRATOR: And as tusks grew,

they propelled the evolution
of the trunks

that would become the hallmark
of all later elephants.

SANDERS: So, I think
once you start to get tusks,

then trunks follow that.

It is important because they
have to have something

to get past the tusks

in order to reach the food
in their environment.

NARRATOR: As trunks grew,
they slowly became

the amazingly sensitive organ
of touch and smell they are

in modern elephants.

SANDERS: Trunks are made up

of something like
72,000 tiny muscle fibers,

so they're highly complex,
and they can move them around

the way that you can move your
hand around playing the piano.

Elephants have tremendous
control over their trunk.

It's not just flopping around
and sucking up water.

They can really be very gentle.

They can pick a penny up
off the ground with their trunk.

Those trunks get a big workout.

NARRATOR: Tusks, trunks,
and great size

were obviously successful
elephant adaptations

to their forest environment,

but they didn't
just help elephants

respond to their environment,

they gave them the capacity
to change it, too.

NENGO: So, I think of all
the species that we know of,

apart from humans,
the only other mammals

that we know have the capacity

to be able to alter the natural
ecosystems they live in

in a short time
in a very big way

would be the elephants.

SANDERS: Proboscideans
are big animals,

and you can imagine any big
animal going through a landscape

is knocking down trees,

moving vegetation
out of the way, creating paths.

NARRATOR: For that, Bill
believes we humans owe them

a debt of gratitude.

He thinks elephants helped
create the perfect conditions

for a certain group of apes
millions of years later

to come down out of the trees

and begin to explore
the savannas.

Those were our ancestors,
the australopithecines.

The famous early human Lucy was
discovered not far from Buluk.

Bill is convinced that she and
our other early human ancestors

flourished in a landscape

that had been unintentionally
prepared for them by elephants.

SANDERS: This idea of
elephants opening things up

and creating the conditions
of success for early hominids

might not be
an exaggeration to say

that we might not be here
without elephants.

NARRATOR: And just
like our ancestors,

elephants did not stay put.

After millions of years
in Africa,

they started to leave.

SANDERS: Proboscideans
leave Africa multiple times.

Different groups
leave at different times.

The first major foray
out of Africa

is around 18 million years.

One suspects that you
follow the vegetation

and you follow
the available land paths,

so if Africa is docking
with Eurasia

as continents
move around a bit,

and you find familiar plants,

you don't really know
you've left Africa,

and you just keep moving.

"Oh, and there's, over--

there's another pasture over
there that seems pretty good.

Oh, well, wait.

Over that hill,
that looks pretty green, too."

They get out
at about 18 million years

in a serious way,
out to Eurasia,

and they make it all the way
to Japan in rapid time,

within a period
of about a million years

after getting out of Africa.

♪

NARRATOR: Until recently,
all we knew

of those ancient elephant
species that left Africa

was from a few fossil bones.

But then, a dramatically
different kind of discovery

brought them to life.

In the deserts of Abu Dhabi,

scientists discovered not bones,
but footprints.

They were made
by ancient elephants,

a vivid record of their
great migration out of Africa.

FAYSAL BIBI: It's phenomenal
because when you're actually

on the landscape,

it seems like the elephants
just passed there yesterday,

but we know, geologically
speaking, that's impossible.

These are very,
very old sediments.

My name's Faysal Bibi.

I'm a paleontologist

at the Natural History Museum
in Berlin.

So, it was,
it was almost an afterthought

to image the tracks
from the air.

And then we went
back to the hotel that night,

and we started
to put the imagery together.

As we realized what we had,
we basically, our jaws dropped.

NARRATOR: What they saw was
the footprints of an entire herd

of ancient elephants
on the move,

a snapshot in time

of elephant behavior
seven million years ago.

Back then, this desert
was a lush savanna.

The muddy ground
after a rainfall

captured their footprints
perfectly,

all made by one of the strangest
of elephant relatives.

♪

BIBI: It's probably ten minutes

in the lives
of these individuals,

this herd that walked
across the landscape,

and those ten minutes are
forever preserved in these rocks

for us to see.

NARRATOR: And in that
ten-minute snapshot,

Faysal can see all the dynamics
of the herd--

the adults and calves,

a single bull male
and a number of females.

BIBI: Yeah, so we have,
it's a minimum

of 13 individuals actually.

You're walking along,
and here was a large individual.

There was probably
the matriarch.

They slow down.
They speed up a little.

There was a smaller guy.

He's on the edge,
so we're clearly not too worried

about any predators
coming along on this landscape.

And then, perhaps, just the day
before or the day after,

we've had the large bull
who also crossed this landscape.

NARRATOR: Not long
after Faysal and his team

made their discovery,

they took Bill Sanders
to see it.

SANDERS: I had no idea
what awaited me.

And then I saw them.

All the footprints
of an entire herd

going on for about 260 meters,

and you can see baby footprints,

juvenile footprints,
female footprints,

and then one great track
of a big bull male

that must have come along later
and crossed that track

and sort of
checking out the herd.

We rarely get that opportunity.

I work on elephants,
I love elephants,

and I'm seeing their behavior
crystalized in time,

all the way back to the
very beginnings of elephants.

And I just started crying.

And my colleagues
all sort of applauded,

and they realized I was not
crying out of sadness.

I was crying
because I was ecstatic.

NARRATOR: Like skilled trackers,

the scientists could read
the ancient footprints

and reconstruct
a remarkably detailed picture

of that day
seven million years ago.

BIBI: We could estimate
the actual size

of these individuals

based on stride lengths
of modern elephants,

where their weights are known,

and their stride lengths
are known.

And their estimated weights

go from a few hundred kilos
for the small one,

up to 5,000 kilos or so
for the largest in the group,

and possibly 6,000 or so
for the solitary individual

that was walking at that site.

NARRATOR: That makes them as big
as any bull elephant today.

From fossils found nearby,

we know that they were
magnificent animals,

four-tusked beasts
called Stegotetrabelodons.

[trumpets]

BIBI: And here you are,
you're on this landscape,

and you can imagine them
having just been here,

like it was yesterday.

NARRATOR: Over generations,

their ancestors
made the journey from Africa,

thousands of miles away.

[grumbling]

BIBI: They're extinct,
they're long gone,

and they haven't just left us
their bones and teeth,

this is an imprint
of their society.

♪

NARRATOR: The discoveries
in Abu Dhabi show

that by seven million years ago,

the social behavior of
elephants had already evolved.

[elephant trumpets]

KAHUMBU: The fact that,
uh, these ancient elephants

behaved very similarly
to modern elephants

in a way confirms that
it is a very successful strategy

to have these families
working together.

They are incredibly
cooperative as families.

You'll see females looking after
each other's calves.

The young will actually have
a very high death rate

if there aren't aunts around
to look after the babies.

NARRATOR: Their close
family bonds have been a key

to the success of elephants
for generations.

[grunting]

Even though Stegotetrabelodons
disappeared

a few million years ago,

their descendants
and other elephant species

soon populated
much of the globe.

Some, like the mammoths,

adapted to the cold
of Siberia and North America.

Others, like the Gomphotheres,
headed for the warmer climes

of southern Asia
and Central America.

It had taken 60 million years,
but the elephant lineage

had become one of the
most successful on the planet.

Just 50,000 years ago,

elephant species
were on all continents

except Australia, Antarctica,
and South America.

So, what happened to them all?

SANDERS: A long debate
among my colleagues

in my field has been,

what are the agencies
for the extinction

of the elephants that we see,

for example,
mammoths and mastodons?

NARRATOR: One hypothesis
is climate change.

At the end of the last ice age,
10,000 years ago,

the world warmed.

The cold-adapted elephants
of Siberia and North America

just couldn't deal with it.

SANDERS:
In the Northern Hemisphere,

in northern latitudes,
you have all this glaciation,

and these changes are
happening very, very rapidly.

NARRATOR:
But for millions of years,

the mammoths and mastodons
managed to weather

similar climate changes.

What was different
about the warming

at the end of the last ice age?

Bill believes it was
our own ancestors

who tipped the balance.

SANDERS: So, we see
the great sites in Eurasia

where indigenous peoples
like 10,000 years ago

and 50,000 years ago
and 60,000 years ago

were slaughtering these
elephants in great numbers.

There is a tremendous
predation pressure,

and imagine if you've
got predation pressure

hitting you on one side,

and now you've
got this climate change

and what it does
to the landscape,

what it does to the plants
and the available resources.

♪

NARRATOR: By 4,000 years ago,
the world was left

with just the African, Asian,

and forest elephants
we know today,

and now these
are under threat as well.

This time, it has nothing to do
with the end of an ice age,

just us.

♪

In 1800, there were an estimated
25 million elephants.

Today there are
less than a million,

and the number is falling fast,
thanks to habitat loss

and the relentless slaughter
of elephants for ivory.

♪

KAHUMBU: Poaching now
is very mechanized.

It's industrial.

In some places, we're losing
1,000 elephants in a month.

It's being done
with not just weapons,

but with aircraft,
trains and trucks and ships

to move the ivory
out of Africa very quickly.

NARRATOR: The tusks
that helped elephants survive

for millions of years
have become a liability.

It's a new kind
of evolutionary pressure,

human generated,

and in Africa,

it's causing elephants to change
almost overnight.

KAHUMBU: Over the millennia,

elephants have evolved
to have these huge tusks

because the most successful
elephants are the ones

that had the biggest tusks.

But over the last
few hundred years,

us human beings
have been killing elephants

for those tusks.

There are some populations
of elephants

who have very small tusks
because poachers

are selectively removing
elephants with big tusks,

and so the only females
that get to breed

are the ones
which have very small tusks,

and so you increasingly
see tusklessness

in some of these
elephant populations.

It would be such a tragedy
if these magnificent animals

lost the one thing
that makes them, you know,

so unique--their tusks.

NARRATOR: Even as they adapt,
elephants are at risk.

Like so many other creatures,

they now face
a new era of extinction.

SANDERS: If we lose elephants,

we put a big hole in
the fabric of our coexistence

with other animals on Earth.

We've damaged in a way that we
can't fix our ecological web,

our interdependent
ecological web.

And we like
to think of ourselves

as being separate from that,

but we really are
inextricably linked.

NARRATOR: Everywhere the natural
world is being transformed.

♪

Our own lineage has become

the planet's dominant
evolutionary force,

shaping the web of life
that exists all around us.

This one
recently arrived species

is now the worldwide presence
to which all others must adapt.

Our impact is so huge
that our era

has been given its own name--

the Anthropocene,
the age of humans.

It has seen the extinction rate
among natural species

soar to hundreds of times
what it was before our arrival.

As scientists race to chart
the planetary changes,

they can look back
at lessons from deep time.

They're observing many
of the things that happened

in earlier extinctions--

rising CO2 levels leading
to acidification of the oceans

and rapid climate change.

Habitat destruction.

Many believe we are witnessing

our planet's
sixth mass extinction,

but the first one caused
by a single species.

Like others, it will reset
the evolutionary clock.

We just don't know how.

SUES: Today when we live
in a world

where human populations
are gradually changing

the face of the globe

by turning natural environments
into artificial environments,

by pollution and many other ways

of interfering
with natural systems,

we are very much confronted
with the question

of evolution and extinction.

You can't have evolution
without extinction,

but extinction really
complicates our efforts

to get the big picture.

NARRATOR: We now know
that mass extinctions

are an engine of evolution,
clearing out environments,

making room
for new species to evolve.

But in the past, they have
usually taken millions of years.

This one is happening fast,
in a matter of generations.

Viewed through the lens of
deep time, that is a nanosecond,

too fast for many living things
to adapt...

but maybe not too fast
for us to make a difference.

Crocs have lived on Earth
for almost 230 million years.

They've survived
cataclysmic extinction events,

but today,
5 of the 14 crocodile species

are critically endangered.

HEKKALA: Most
of the living crocodilians

were on the verge
of extinction by the 1970s.

We were on the verge
of losing all of them

when we put in place protection.

NARRATOR:
Protections have helped.

In Australia, both fresh and
salt water crocs have rebounded

thanks to strong steps
like restrictions on hunting.

But what about the other
great survivors of deep history?

10,000 species of birds
still cover the globe.

Some have adapted to cities,

where they live beside us
in seeming harmony.

But that's not the whole story.

CLARKE: We are hugely
impacting bird evolution.

This is in habitat loss,
consumption or killing,

poisons, the use of toxins
in our environment.

[chirping]

NARRATOR: With 40 percent
of bird species in decline,

there's reason to worry,
but also reason to hope.

We managed to turn things around
for iconic species

like the bald eagle
and California condor.

And innovative programs
show that more is possible.

In 1974,

only four Mauritius kestrels
were left in the wild.

Today, there are
100 times as many,

thanks to predator control
and captive breeding.

Ocean creatures
need protection, too.

It took 50 million years
for whales to become

the wondrous giants of the deep
we know today.

[gunshot]

But in just two centuries,
industrial whaling

brought many of them
to the brink of extinction.

In the 20th century alone,

almost three million whales
were slaughtered.

HILDERING: It's unthinkable now
that we exploited whales

to the extent of,
in the case of humpbacks,

driving down their population

to 10 percent
of what they were globally.

They were almost
pushed over the edge.

We only stopped whaling
on northern Vancouver Island

in 1967.

Humpbacks we stopped in 1965.

So, we thought of them
so very differently.

We saw them as a, as a resource.

But with humpbacks,
we have a second chance.

NARRATOR: While some whales
are critically endangered,

whaling bans
have made a difference.

Humpbacks have rebounded,

and blue whale populations,
which fell to just 1,500,

seem to be slowly increasing.

HILDERING: One of the many
things that the whales do

is they remind us
how connected we are

and of our capacity for change.

[grumbling]

NARRATOR: Around the planet,

others are heeding
that reminder,

committing themselves to protect
endangered animals and places.

[roaring]

In Kenya, Paula Kahumbu admires

one of the last true giants
left on Earth,

a tusker named Tolstoy.

[grumbling]

KAHUMBU: I feel very humbled
to be able to meet Tolstoy.

He is a giant of giants.

He's not just a big tusker,
he's a super tusker.

There are very, very few
elephants of that size

with tusks of that length
left in the world.

You know, when,
when you're with Tolstoy,

it's, one of the biggest
rushes you get

is that "I'm alive." Right?

You just feel
this sense of life.

It gives you goosebumps
just to know that this elephant

is aware of your presence,
and you're tiny and he's huge.

It's, he's beautiful.

It's just the most incredible
experience.

NARRATOR: To know that Tolstoy
is the product

of an evolutionary journey

that has been going on for eons

only makes him more precious.

And Tolstoy is not alone.

Crocodiles and birds,
whales and elephants

are just four life forms
among millions.

The tree of life is vast,

encompassing everything
that has ever lived.

What will its branches look like
after the age of humans?

The answer is up to us.

♪

♪