All language subtitles for NOVA.S51E01.When.Whales.Could.Walk.1080p.WEB.h264-BAE_track3_[eng]

♪ ♪

NARRATOR:
In the sands
of the Egyptian Desert,

experts are uncovering clues
to a lost past.

Look at this!
Right here.

NARRATOR:
From a time
long before the pharaohs,

when this place
was underwater

and whales...

Had legs?

HESHAM SALLAM:
Here's the hind limb

of this beast.

It's just like T. rex hand,

do nothing.

♪ ♪

NARRATOR:
Whales are the world's
biggest mammals.

But how did they end up
in the ocean?

This is so awesome.

They're doing everything
mammals do,

but in the water.

♪ ♪

NARRATOR:
Now new discoveries
are revealing clues

about their evolutionary past.

Wow!
Look at this!

SALLAM:
Oh, my word!

PHILIP GINGERICH:
When I first saw it,
I had no idea what it was.

NARRATOR:
From prehistoric predators

to the largest animal
that has ever lived.

How did the whale's journey
begin?

It's one of the greatest stories
of evolution.

"When Whales Could Walk."

Right now, on "NOVA."

♪ ♪

♪ ♪

NARRATOR:
Wadi Hitan,
in Egypt's Sahara Desert.

Hidden beneath these rocks
are secrets

from a time long before humans.

♪ ♪

SALLAM:
Many people think of Egypt like

ancient Egyptian civilization.

Like pharaohs, Sphinx, and
Romans, even.

Prehistoric life.

NARRATOR:
Paleontologist Hesham Sallam

is on a mission to uncover
his country's prehistoric past.

SALLAM:
The place that we are
heading toward

is one of the most important

place in Egypt,
if not in the world,

in term of paleontology.

NARRATOR:
Hesham is searching
for clues

to an extraordinary
evolutionary mystery.

♪ ♪

Here, it's the middle
of nowhere,

it seems like empty place,

but there is tons of evidence
that you can see.

Fossils are everywhere,

telling you
what life looked like

40 million years ago.

NARRATOR:
Across more than
75 square miles,

fossils litter the desert.

There are so many,

Hesham has to remove his shoes
to avoid crushing them.

Just look at this, for example.

There's a really nice shell.

Really wonderful,
well-preserved.

It's look like living one,

but it was living

40 million years ago.

♪ ♪

NARRATOR:
But this desert also hides
much larger fossils.

SALLAM:
This is typically
what you see in Wadi Hitan:

the bone sticking out
from the cliff,

calling you to come and see it.

And indeed,
this is a really huge animal.

The vertebra would be that big.

And not only the vertebrae,

but also, you can find ribs
all over the place.

Given the size of the vertebrae,

it might be getting
up to 20 meter long.

NARRATOR:
The size and shape of an animal
around 60 feet long

encased in this rock

has led scientists
to a remarkable conclusion.

SALLAM:
I think we have
a complete skeleton

of the prehistoric whale
that lived here in Egypt,

long, long, long time ago.

♪ ♪

NARRATOR:
Since the first whale fossils
were discovered here in 1902,

experts have found
around 1,000 individuals.

This is the biggest ancient
whale graveyard known on Earth.

That's why paleontologists
named it Wadi Hitan--

the Valley of the Whales.

But what are these sea creatures
doing here

in a desert over 100 miles
from the coast?

♪ ♪

Shorouq Al-Ashqar is
one of Egypt's

first female vertebrate
paleontologists.

AL-ASHQAR:
These are shark teeth.

Also, look at these shells.

These animals live
at the bottom of the sea.

NARRATOR:
Nearby, Shorouq
finds another clue.

AL-ASHQAR:
Look at this structure.

Many scientists do believe
that these

are mangrove roots,
as they found

a lot of mangrove seeds
all over the area.

But other scientists

believe that these might be
crustacean burrows.

Crabs, snails

lived there and burrowed
in the soft sand.

NARRATOR:
Whether these are
fossilized mangrove roots

or burrows dug by
prehistoric crustaceans,

it's clear

this area was once underwater.

♪ ♪

Today's excavation site
was at the bottom of the sea

40 million years ago.

Back then,
the Mediterranean was part

of a much larger ocean,
the Tethys.

It stretched
from Europe to India,

and was full of marine life.

♪ ♪

But when sea levels dropped,

they left behind
a seabed rich in fossils.

Today, this desert is
the resting place of some

of the earliest whales
ever found.

They may hold the key to how
today's ocean giants evolved.

♪ ♪

6,000 miles away,
in the Dominican Republic,

living whales gather
in these tropical waters

early in the year.

♪ ♪

It's humpback whale
breeding season.

Comparative anatomist
Joy Reidenberg

has come to study them.

REIDENBERG:
Oh, there's a blow.

Wow-- oh, and
just the other side!

Did you see that?

There's this tiny little fin--
that's the baby!

We've got a mother and her calf
right here together,

swimming side by side.

NARRATOR:
Humpbacks are one
of around 90 different species

of whale living today

that include toothed whales,

like orcas, dolphins,
and porpoises,

and baleen whales,
like these humpbacks.

Whales can swim
thousands of miles,

dive thousands of feet,

and stay underwater
for over an hour.

♪ ♪

REIDENBERG:
I love whales, I really do.

Such magnificent,
huge creatures.

And so well-adapted
for being in the water.

♪ ♪

NARRATOR:
And yet, they're mammals.

They breathe air using lungs.

Just like us.

♪ ♪

REIDENBERG:
We've got a mother and calf
over here.

The mother is nursing its baby.

But these animals not
only breathe air and give milk,

but they're doing everything
mammals do, but in the water.

They have to mate in the water.

They have to carry
their pregnancy in the water.

They have
to find food in the water.

And then they give birth
in the water.

All of this

because these animals
have evolved

to be an aquatic mammal.

♪ ♪

NARRATOR:
How did air-breathing mammals
end up in the ocean?

♪ ♪

For centuries, many people
confused whales with fish,

including the characters
in the novel "Moby-Dick."

♪ ♪

Even though, in the 1750s,

the Swedish naturalist
Carl Linnaeus

had already classified whales
as mammals,

recognizing that,
among other traits,

they have lungs
and produce milk.

But where whales came from
caused even

Charles Darwin
to scratch his beard.

Inspired by a bear seen feeding
while it swam,

he imagined how whales
could evolve from land mammals.

But faced with ridicule,

he removed this idea
from his later writings.

♪ ♪

Perhaps Darwin's hunch had legs.

Could it be that whales
hadn't evolved in the water,

but were actually descended
from mammals

that once walked on land?

It almost seems like evolution
had taken a backwards step.

♪ ♪

It's a question
that fascinates Hesham Sallam.

He believes clues can be found

in the huge fossils that
lie scattered in this desert.

This is one of the most complete
skeleton

that we find in Wadi Hitan.

In the middle of nowhere,

you find a lot of really huge
vertebrae lined up.

The skull would be over there
in that rock,

and the ribs on both side.

This is really spectacularly
huge animal

that lived here in Wadi Hitan
40 million years ago,

the Basilosaurus.

♪ ♪

NARRATOR:
Basilosaurus fossils
have been discovered

in many parts of the world,

including around 600
here at Wadi Hitan.

This one has been laid out
in the place it was found.

When the first Basilosaurus
was studied in 1834,

experts were baffled.

SALLAM:
When the early scientists
found this,

they thought it's belonged

to a kind of
gigantic marine reptile.

And the, this is why they give
it name "Basilosaurus,"

which means "king lizard."

♪ ♪

NARRATOR:
But the skull contains a clue

to Basilosaurus's true identity.

This is the skull upside down,
and you can see

all the teeth
are sticking up.

And this, actually,

they have incisors, canine,

premolars, and molar.

Really, like our teeth,

which is actually
a really good indication for,

this is not a marine reptile,
this is actually mammal.

So Basilosaurus,
the king lizard,

it's actually ancient whale.

♪ ♪

NARRATOR:
40 million years ago,

Basilosaurus was the apex
predator of its day.

It could grow up
to 60 feet long,

the length of a bowling alley,

and weigh more than seven tons.

Powerful jaws filled
with sharp teeth made it

a killing machine.

Scientists estimate its bite
had a force of nearly two tons,

enough to crush the bones
of other whales.

Basilosaurus was
a prehistoric king of beasts.

But its discovery didn't
initially shed much light

on whale evolution.

Or how these mammals
ended up in the ocean.

It's a mystery that has
intrigued Philip Gingerich

for almost 50 years.

A pioneer in the field
of whale evolution,

he was one of the first
paleontologists

to excavate at Wadi Hitan.

So this is where I keep
the fossils I'm working on.

So here is the skull of
Basilosaurus.

Uh, it's upside down.

And this is a model of it,
a cast of it.

Collected in 2005.

Here we are,
I'm still working on them.

(chuckling):
Takes time.

NARRATOR:
When Philip started his career,
he studied land mammals.

At the time, paleontologists
had very little idea

about the origins of whales.

I grew up in the Midwest and
I wasn't near the ocean, and...

I didn't know anything
about whales.

I knew so little
that I wasn't interested.

♪ ♪

NARRATOR:
In 1978, Philip went to Pakistan

to search
for prehistoric horses.

Instead, his team unearthed
the remains

of a mysterious creature.

The first thing we found
was this skull.

Back of a skull--
it's not complete.

The front, the part
with the eyes

and the teeth and everything,
has broken off.

When I first saw it,
I had no idea what it was.

I was probably disappointed,
because

I was looking for horses,
and it clearly wasn't a horse.

But what it was,
I couldn't figure out.

NARRATOR:
The team named the strange
animal Pakicetus.

It's about 50 million years old.

When Philip took a closer look,
he spotted something

unexpected
in the creature's ear.

So when you look
at this covering bone,

covering the ear,

it's very dense, it's thickened,

it has a sloping surface
on this side.

And in modern mammals,
those are only found in whales.

And why?
To enable them to hear in water.

♪ ♪

NARRATOR:
This ear bone,
unique to whales and dolphins,

helps them locate the direction
of sounds underwater.

It's proof
of Pakicetus's pedigree.

GINGERICH:
This bone was the key
to understanding

that Pakicetus is a whale.

That made it the oldest
fossil whale anybody ever found.

NARRATOR:
It was groundbreaking.

And as they discover
more Pakicetus fossils,

they realized something else.

This whale could walk.

Pakicetus is an animal
a little bigger than a wolf.

Probably built approximately
like a wolf.

It has teeth
like a carnivorous mammal.

NARRATOR:
But unlike a wolf, that has
claws on the ends of its toes,

Pakicetus had tiny hooves.

♪ ♪

Pakicetus was a carnivore
that hunted on land.

But its anatomy suggests it had
adapted to living in water.

Its long snout,
full of sharp teeth,

also allowed it to probe
shallow riverbeds for prey.

Its eyes were squeezed
onto the top of its head,

so it could keep watch
while swimming.

♪ ♪

And some scientists think
markings on its foot bones

are evidence it had webbing
between its toes,

allowing it to hunt underwater.

Why was Pakicetus spending
so much time in the water?

I think it was because
the water was full of fish.

And judging from its teeth,
it's pretty clear that they were

taking advantage of that,
going in the water,

feeding on the fish, and
didn't have much competition.

And of course,
it didn't take long until

they moved into the water
more permanently.

NARRATOR:
Pakicetus marks the beginning
of an eventful journey

from land animals
to today's gigantic whales.

For Philip, it was the start
of a lifelong passion.

It changed the course
of my entire career because

I got interested in this
as an example of evolution.

And it's especially
interesting because

it seems like it's backwards--

it's back to the sea,
not out of the sea.

♪ ♪

NARRATOR:
The oceans are thought
to be where life started.

Around 400 million years ago,

some fish left the water
to live on land.

Over time,
their descendants evolved

into amphibians, dinosaurs,
and mammals.

Then, about 50 million years
ago,

something incredible happened.

Some mammals found their way
back into the water.

They spread
to all the world's oceans,

evolving into the whales
we know today,

from huge blue and sperm whales

to orcas and porpoises.

♪ ♪

How did this transformation
happen?

To find out, scientists
examine anatomical clues

in modern whales,
as well as ancient fossils.

By doing a dissection,

they hope to reveal more secrets
of their ancestry.

REIDENBERG:
Okay, let's unwrap.

NARRATOR:
Comparative anatomist
Joy Reidenberg is investigating

a young beaked whale
that was found dead

on the coast of the U.S.A.

Joining her is evolutionary
biologist Michael McGowen.

It's always really sad
when you have a stranded whale.

Yeah.
But for us,
this is a gold mine.

We have an opportunity here
to learn something

about an animal
that's quite rare.

These particular species are
rarely sighted at the surface,

because they just come up,

take a quick breath,
and go back down.

REIDENBERG:
What's really cool,
I think, is, beaked whales

are really adapted to stay
at depth,

and that's their norm.
Yes.

NARRATOR:
Cutting into the animal's
abdomen,

they reveal something curious:

an important clue
about the origins of whales.

That's the stomach.
Uh-huh.

Now, look at,
look how weird this is.

These animals are carnivores--
you expect them to be like a cat

or a dog, and have one
stomach chamber,

but in fact, they don't.

They have multiple
stomach chambers,

kind of like hoofed animals,
like cattle or deer or sheep.

So you got
one, two, three, four,

five, six, seven, eight...

Wow.

I think there's eight
or nine chambers,

which is crazy,
when you think about it!

It's crazy--
it's nuts.

NARRATOR:
All whales and dolphins have
this unexpected feature

of multiple stomach chambers.

It's a trait they inherited

from their ancient relatives
that walked on land.

MCGOWEN:
Just like cows have
multiple stomachs

to digest their plant matter,

whales have multiple stomachs

to digest what they're eating,
which is completely different--

fishes and squid--

but it's still

coming from the same structure
as a terrestrial mammal.

It's just a throwback
to their terrestrial ancestry

of having
a multi-chambered stomach

because their ancestor did.

♪ ♪

NARRATOR:
This anatomy is more
evidence

that whales are related
to hoofed mammals.

And this terrestrial heritage
can even be revealed

in their genes.

♪ ♪

In his lab, Michael uses modern
whales' DNA to map their past.

It's opening up a vast new world
of information

about the origins of whales.

So if you think about
different marine mammals,

such as a manatee or a seal
or sea lion, they all swim

and live in the ocean
and have similar adaptations

to whales and dolphins.

But we can look at the DNA
to see whether whales

and dolphins are closely
related to those other groups

or whether they're related
to another species entirely.

NARRATOR:
Scientists wanted to identify

the whale's closest living
relative.

So they compared

whale DNA
with a range of other animals.

They came up with
a really surprising finding.

And the finding was that
the whale's closest relative,

using DNA, was...

...the hippo.

♪ ♪

NARRATOR:
Whales and hippos both
descended

from a common hoofed ancestor

that lived about five million
years before Pakicetus.

The family resemblance
is striking.

Some of the earliest whales,
like Pakicetus,

may have lived like hippos.

Also, hippos
give birth underwater.

They nurse underwater.

Their skin is also very thick.

So it's interesting to think
that maybe the common ancestor

of whales and dolphins
had these particular features.

NARRATOR:
But life in the ocean
is very different

from life on the riverbank.

Over time, whales' ancestors
adapted to this new environment.

(hippos croaking)

Scientists compared
the DNA of hippos

and whales to find out how.

(hippos croaking)

When we look at the genome
of whales,

we see that whales still have
a lot of the genes

from when they used
to live on land.

So they still have
genes involved in smelling,

sweat glands,
color vision, producing saliva.

But these genes are inactivated,
and they gradually degrade.

But I think this is incredibly
powerful evidence that shows

that whales come
from land ancestors,

that they still have these genes
in their genomes,

even though they're inactivated.

NARRATOR:
Over millions of years,

whales lost many traits
beneficial on land

that had no use in water.

But what happened to that most
vital land animal feature,

legs?

♪ ♪

In Egypt, Hesham Sallam's
mission is to find fossils

that can tell us more about
how whales became fully aquatic.

He's leaving
Wadi Hitan to search

a nearby unexplored area
with older rock deposits.

SALLAM:
Here we are.

(brake engages, engine stops)

Ready to find fossils?

AL-ASHQAR:
Sure.

NARRATOR:
Joining him are
fellow paleontologists

Shorouq Al-Ashqar
and Abdullah Gohar.

From geological maps, they know
this part of the ancient seabed

is about two million years older
than the deposits

where the giant Basilosaurus
was found.

They're searching
for intermediate fossils

that might shed light on how
four-legged land mammals

evolved into their fully aquatic
descendants.

SALLAM:
I'm hoping to find maybe

a full skeleton of, uh,

some ancient whales

that we didn't know much about.

If we're lucky to find
that,

this prehistoric animal here

might have sturdy legs

that can actually lift
the body out of the water.

So this is what I'm trying
to do,

is find more primitive whales,

and this is going
to happen in, in maybe,

in a few hours,
few weeks, few months.

It depends how luck we have.

♪ ♪

NARRATOR:
And it's not long before
fossils start to appear.

Wow!
Look at this!

SALLAM:
Hey, what have you found?

We have a monster here.

Oh, my word.
A giant...

This is incredible.

Yeah.
Look at this beast.

Yes.

This is a shark tooth.

This is really huge shark.

NARRATOR:
But there's still no sign
of a whale.

And then...

SALLAM:
Hey!

NARRATOR:
They've found something.

Look at this.

Right here.

A small vertebra.

GOHAR: Oh.
AL-ASHQAR: Wow.

SALLAM:
Right there,
another one here.

GOHAR:
Amazing.
SALLAM: Another one there.

So it seems like a...

Um, a complete skeleton here.
Yeah.

Look at this line up.

Could be the vertebral column
going that way.

But this is definitely not
Basilosaurus.

The size of the vertebra
is quite small.

♪ ♪

NARRATOR:
With his expert eye,

Hesham can recognize the shape
of the bones immediately.

I think this is a, a skeleton,

and I do believe might be
the skull over there.

Really exciting.

♪ ♪

NARRATOR:
Could it provide clues

to how whales lost their legs?

So this is definitely older
than Basilosaurus,

because the Basilosaurus

come later, in the
younger deposits.

So this might be a kind of
amphibious lifestyle whale,

but with really sturdy
hind limb.

If we are lucky enough,

we might find the pelvis
somewhere

and the hind limbs right here.

♪ ♪

NARRATOR:
Before they can find out more,

they hit a problem.

(wind roaring)

If it's actually
getting too windy,

we just have to
leave the site and come

when the nature calm down.

I think we should stop.

NARRATOR:
They mark the spot
so they can return to it later.

Until then, this whale's place
in the family tree

will remain unknown.

♪ ♪

Meanwhile, in their lab
at Mansoura University,

Hesham and Abdullah
are investigating

another new piece of the puzzle.

♪ ♪

This is one of the
most important discovery.

Here we have
nearly complete skull,

a lower jaw,

some of the vertebrae,

and some of the broken ribs.

NARRATOR:
This is a previously unknown
species of ancient whale.

Abdullah has named it
Phiomicetus anubis,

after Anubis,

the ancient Egyptian god
of death.

GOHAR:
We have a clear indication

of very powerful predator

that hunt everything around him.

So we clearly can consider him

the god of death
for all living animal

that lived by him
43 million years ago.

NARRATOR:
It's one of the oldest
whale fossils

ever unearthed in Africa.

But could it walk on land,
like its ancestor Pakicetus?

The team hasn't found leg bones,

so they must look
for other evidence.

Abdullah has found a clue

in a bony projection
on one of the vertebrae.

This is a thoracic vertebra
from the rib cage region,

and you can see, this
sticking-out bone here

is called neural spine.

It's very short
in human, here,

but this is very clear evidence
of walking lifestyle,

because the longer
this sticking-out bone,

the more ability
to hold massive muscles

that support the walking
on four legs.

So, land mammals have this

very long neural spine
here.

This is a cow.

SALLAM:
But if you look at
the modern dolphin,

you can see clearly
this sticking neural spine

is much, much shorter

comparing to the walking
terrestrial animal.

So this is fully aquatic,

this is fully terrestrial,

and anubis in between.

NARRATOR:
The team believes that if anubis
had strong back muscles,

it probably used them
for walking.

♪ ♪

Anubis, the god of death,

was a formidable
marine predator.

It measured around ten feet long

and weighed over half a ton.

It spent extended periods
in the sea,

where it hunted fish
and turtles.

But from the bones
the team has found,

they think it was able
to come back to land,

perhaps to breed.

And it didn't wriggle
out of the water like a seal.

Anubis was probably
a walking whale.

Where can I put it?

(man speaking off mic)
Thank you.

NARRATOR:
To find out more about

anubis's place
in the whale family tree,

Hesham and Abdullah
take the skull

to a nearby hospital
for a CT scan.

♪ ♪

Shall we get outside now?

MOHAMMED:
Yes, yes, yes,
outside.

♪ ♪

Can you go inside?

NARRATOR:
Hesham wants to take
a closer look

at the position
of anubis's nostrils...

Okay,

can you zoom out,
please?

NARRATOR:
...and spots something striking.

So here in anubis,

the tip of the snout
is broken off,

and it could be
up to here,

but the nasal opening
would be right here,

one-third the way back
in the snout.

Comparing to
the modern whale,

the blowhole would be
on the top of the skull.

NARRATOR:
Land mammals' nostrils are
at the tip of the nose.

Modern whales' nostrils
have moved to

the top of their heads
to become blowholes.

But anubis's nostrils are

a third of the way back
on its snout.

It's one step closer
to becoming fully aquatic.

So, how did walking whales

lose their legs
to become modern whales?

Back at Wadi Hitan,

Hesham takes a closer look
at Basilosaurus.

This huge marine predator

evolved about three million
years after anubis.

But could it support itself
on land?

Here is the arm
of this beast.

It's actually wasn't like
a regular arm of a mammal's,

but flippers, to allow it to
swim in the sea.

NARRATOR:
Basilosaurus's front legs
have turned into flippers.

And at the back of the animal

is something
even more intriguing.

This is really something

very cool in
the whale evolution.

This is the hind limb
of this monster,

and this is
a complete pelvis.

Would be underneath

one of these vertebrae, like
that.

And this is the whole legs

of this really huge animal.

This is the right leg--

the thigh bone,

the shinbone,

and the foot.

♪ ♪

NARRATOR:
These casts show
that Basilosaurus's legs

were smaller
than the arms of a human.

Definitely
Basilosaurus cannot walk,

given the size
of these hind limbs

comparing to the whole body,
20 meter long.

Just totally cannot support
walking on land.

Just like T. rex hand,
do nothing.

♪ ♪

NARRATOR:
Unlike its walking whale
ancestors,

Basilosaurus was fully aquatic.

But in modern whales,

are there any remnants
of their walking past?

Back in the lab,

Joy Reidenberg
and Michael McGowen

are looking for more clues
inside the beaked whale.

We're now looking
at the flank area,

and I'm going to show you

something really cool
in this area.

Right in here
is a small bone.

Something that is really
a throwback

to the ancestral condition
of having hind legs.

All that's left is
a little remnant of a pelvis.

NARRATOR:
This tiny pelvic bone

is hidden in the whale's
hind quarters,

where hips would once have been.

The only thing
it doesn't have is

the connection
back to the spine.

So ours is connected
in the back to the spine.

This one is just free-floating.

It's tiny--
it's actually

a lot smaller than
I thought it was gonna be.

This pelvis
is so interesting,

because it's a throwback

to the land animals

that were using a pelvis
for walking.

But whales aren't walking.

They don't have hind legs.

♪ ♪

NARRATOR:
All modern whales
still have a pelvis,

and some have tiny
hidden leg bones, too.

But why would a whale
need a pelvis?

It still has function.

Part of that function

is to anchor the muscles
of the belly for swimming,

so it's still being used
in locomotion,

just not with legs.

So think about,
in the front, you know,

we have
the six-pack muscles?
Yeah.

These help to bend the body

in this downward motion
like that.

So that's part of
the swimming action.

Oh, wow, okay.

They anchor on this bone.

They anchor in
other places, too,

but they also anchor
on this bone.

MCGOWEN:
And that's another remnant
of its mammal past,

is that they move their spine
up and down.

And with fish

and even reptiles,
they move side to side.

You watch a snake move,

you watch a crocodile
walking,

they're swimming like fish,

but on the land, with legs.
Yeah.

When you get to mammals,

the legs come underneath,

the spine and the body
come off the ground,

and now they're free
to gallop.

♪ ♪

And when whales went

back into the water,

they kept the up and down
spinal movement,

so they're still galloping.

In the water!

♪ ♪

♪ ♪

NARRATOR:
Losing their legs

was just one change
whales underwent

as they adapted
to life in the ocean.

♪ ♪

To survive in this
underwater environment,

whales' limbs grew stronger,
making swimming easier.

They grew horizontal flukes
on the ends of their tails,

and front limbs
began to turn into flippers

for stability and steering.

As they moved
to tail-powered swimming,

their bodies
became more streamlined,

hind limbs shrank,

and their spines grew longer.

They had become fully aquatic

and were unable
to return to the land.

♪ ♪

The desert at Wadi Hitan
is dotted with the skeletons

of some of the first
ancient whales.

But around 34 million years ago,

they mysteriously vanish
from the fossil record here.

In an area about 50 miles
from Wadi Hitan,

Shorouq Al-Ashqar investigates

why the whales disappeared
from this region.

These strange objects
provide an answer.

AL-ASHQAR:
This is fossilized wood.

It seems like wood,
but it's rock.

The wood replaced
by silica and minerals,

so it's so heavy,
but it's a good indication

that this area one day
was a forest.

The trees were very tall,
40 to 50 meters long,

colorful birds flying
in the area.

Turtles, snakes-- full of life.

NARRATOR:
The fossilized wood is
around 34 million years old.

It's a sign that this area,
once a thriving ocean,

underwent a dramatic change.

♪ ♪

At that time,
Earth's climate began to cool.

The Antarctic ice sheet formed

and sea levels dropped.

The Tethys Ocean receded,
forming the Mediterranean.

And where whales once swam
in warm, shallow waters,

a forest grew.

The primitive whales
that lived in Wadi Hitan,

all of them are, died out.

Fortunately, some of whales
adapt with the climatic change.

Whales are mammals,

and mammals
are warm-blooded bodies,

so they can adapt
with the cold water

and find new places to live in.

♪ ♪

NARRATOR:
Being warm-blooded,

they were able to generate
their own heat

and grow blubber to insulate
their bodies from the cold,

allowing them to migrate
and thrive all over the world.

But the whale's story
doesn't end there.

♪ ♪

In a warehouse at the

Smithsonian National Museum
of Natural History

is the world's largest
whale bone collection.

It holds remains from
nearly 10,000 whales.

Evolutionary biologist
Ellen Coombs scans their skulls

to investigate
how they changed over time.

Studying the skull
is really important,

because in whales,

it's where a lot of changes
have happened

over their evolutionary history,

because it houses
a lot of sensory organs--

the eyes, the nose, the brain--

and this can tell us
lots of things

about how the animal
has evolved to eat

and live its life.

NARRATOR:
The 3D scans allow Ellen
to look in detail

at the more recent chapters

in the whale's
evolutionary tale.

♪ ♪

When the last of
the ancient whales died out,

the modern whale's
journey began.

And as the family tree
continued to grow,

something surprising happened.

Some kept their teeth,

like orcas, sperm whales,
and dolphins.

And some, like the blue,
humpback, and right whales,

lost their teeth

and developed
a new filter-feeding tool

called baleen.

This is the underside of the
mouth of a humpback whale,

which is
one of the baleen whales.

And what makes it a baleen whale

is what's going on here.

So this is baleen.

This sits where teeth
would normally sit

in something like a
killer whale or a dolphin.

But instead, they have
these amazing plates of baleen,

which are made of keratin,
just like our hair or nails.

And you can see that it has

these kind of hairs
on the end here,

which are used
to filter out prey.

And what they do is,
they suck in

a big mouthful of water
full of fish or krill,

which is what they eat,

and then they use their tongue

to force out that water
and capture all of their prey

in these plates of baleen.

And that is sometimes up to

half a million calories
in one mouthful.

♪ ♪

♪ ♪

NARRATOR:
Why did these whales
take such a different path

from their toothed cousins?

COOMBS:
Here we can see
a blue whale skull.

The main thing
that we see here

is how flat the face is,

how wide the mouth is,

and these are
perfect adaptations

for mass filter feeding
with baleen.

NARRATOR:
Meanwhile, the toothed whale
has evolved

a very different
skull shape.

So, if we take a look

at the skull of this
killer whale from the side,

you can see that

the forehead is concave.

This is because it houses
a load of organs

that are used for echolocation.

(dolphins clicking and chirping)

NARRATOR:
The highly specialized skill
of echolocation

has evolved in some animals,
like bats and whales.

(dolphins clicking and chirping)

Whales "see" by emitting
high-frequency sounds

and then listening for

how they bounce back off objects

to find prey in the depths
of the ocean.

(dolphins clicking and chirping)

(squeaking)

Toothed whales do this

in a very specialized apparatus
in their forehead,

the key ones being
the phonic lips,

which make a high-frequency
clicking sound,

and the melon,
which is a fatty organ,

which helps to focus
these high-frequency sounds

as they leave the animal.

(dolphins chirping)

NARRATOR:
But how this skill evolved
is still a mystery.

♪ ♪

COOMBS:
So we have ancient whales
dying out

that we know they could not
echolocate.

And then we have the appearance

of the early toothed whales
that could echolocate.

So there's a gap in there,

where there'll be
several fossils

that have maybe
very basic echolocation,

and they're the fossils
that we really need to find.

(orcas squealing)

NARRATOR:
Scientists think
these early whales survived

to pass on their genes
to their offspring,

and so their abilities
gradually improved.

(orcas clicking and squealing)

Today, some toothed whales
are such efficient predators,

they even hunt
their baleen cousins.

♪ ♪

So these humpbacks have evolved
new survival strategies.

♪ ♪

Back in the Dominican Republic,

Joy Reidenberg and
marine biologist Mithriel MacKay

are on a whale-watching mission.

There's a blow,

around 1:00.

And the third.
Yeah.

And four.

There's four there.

NARRATOR:
Most whales live
in family groups

and have complex social lives.

Mithriel and Joy
want to understand

how certain behaviors

give them
an evolutionary advantage.

MACKAY:
We look at the behaviors

and then we start
asking questions.

Why are they doing
those things?

Because the answer
to the why

gives us the reason they evolved
this way.
Mm-hmm.

♪ ♪

(whirring)

♪ ♪

REIDENBERG:
Oh, that's awesome.

MACKAY:
That's beautiful-- beautiful.

REIDENBERG:
Look at how she's putting

the baby on her, on her...
MACKAY: Yep.

She'll scoop under
and pick it up.

REIDENBERG:
And she's using that,

that flat surface
of the top of her head

to hold the calf there,

almost like it's got
a cradle surface.

So she can give the calf
a rest this way.

Or if she feels like
the calf's in danger,

she could pull this calf
right up out of the water.

And there's the male.

NARRATOR:
This mom is being pursued
by a male.

♪ ♪

She's putting the calf
on her head

to protect it
from his aggressive advances.

Mithriel thinks
this protective behavior

plays a role
in baleen whale survival.

Picture them out,
and killer whales coming up

and seeing this baby
as a good meal.

The moms that are able to
use their flat head

to scoop the baby up out of
the water and get away

are the ones whose babies
are going to have babies.

We're always taught
evolution changes things,

but it doesn't.

What it really does is,
it eliminates

the stuff that doesn't work
as well,

so what's left is what works.

It's reactive,
it's not proactive.
Exactly.

NARRATOR:
And these whales have one other
vital defense mechanism:

their huge size.

How did they get so big?

The ancestors of these whales

were actually smaller
than our current whales.

That made them more nimble.

They could swim
through the water

more agilely, picking out fish.

But when we look at these
large baleen whales,

they are feeding in a
completely different way,

and that is partly what's
allowed them to get so big.

So, having large bodies
means they have large mouths,

and the large mouths allowed
them to get a lot of prey.

And having a large body
also allows them

to carry a lot of fat reserves,

which they are using
for swimming

to the regions
where the prey are.

But having
that absolute big size

is something that really evolves
because they're in water.

You know, that biomass

would be very hard
to support on the land.

They would just be crushed.

♪ ♪

NARRATOR:
The whale's transition

from four-legged land mammal
to the giant of the oceans

is one of the most
extraordinary stories

in the history of evolution.

♪ ♪

GINGERICH:
Has the mystery of whale
evolution been solved?

To some degree.

But when we fill a gap,
we make two more, and so,

we're always going
to want to know more.

NARRATOR:
From the first
wolf-sized creatures

that ventured
into freshwater rivers,

to the walking whales
that were champion swimmers,

to fearsome marine predators,

to the largest animal
that has ever lived.

♪ ♪

Today, scientists
continue to search

for the missing chapters
in the whale's story.

SALLAM:
There is more to find
in Wadi Hitan.

There are so many fossils
still hidden inside the rocks,

and we hoping someday to find

very primitive whale

in very ancient deposits

that can actually
complete the story

in whale evolution.

That will be
a really huge discovery.

♪ ♪

NARRATOR:
The whale's evolutionary
journey is not over.

Today, they must
survive new threats

that are driving some species
close to extinction.

REIDENBERG:
There are a lot of
new challenges

that the whales
are facing today,

whether it's fishing,
ship traffic, noise,

climate change-- anything
could be a factor,

because if it affects
their habitat,

it affects
their evolution.

Exactly.

And the challenge is,

evolution doesn't
happen overnight,

so we don't really know

what the consequences
of that will be.

♪ ♪

NARRATOR:
Whales face
a precarious future.

The hope is that
they will adapt and survive

as they have done
for 50 million years.

♪ ♪

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