51x01 - When Whales Could Walk

[bunniefuu]

♪ ♪

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.

But what I'm studying
is way beyond this time.

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



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



♪ ♪

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



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.

♪ ♪


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-d*ck."

♪ ♪

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 k*lling 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.

These are all from
Egypt, from Wadi Hitan.

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


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
k*ller 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 k*ller
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
k*ller 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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