All language subtitles for NOVA.S47E02.Dog.Tales.1080p.AMZN.WEB-DL.DDP.2.0.H.264-GNOME_track3_[eng]

This planet is home
to over a billion dogs.

So in the U.S.A., there's more
than 75 million dogs alone.

They're everywhere now.

They are really special animals.

Pickles!

They're more than
just great pets...

That's my girl.

Mm, love you, too.

Dogs have helped make
humans better hunters.

Better farmers.

They protect people from danger.

And might even save
them from themselves.

You can hug your dog.

The dogs change so many of them.

It's amazing.

What makes dogs so special?

Discoveries in genetics
and behavioral science

are now starting to
unlock their secrets.

The last decade in dog science

has been the most
exciting there's ever been.

This is just the
most amazing time

to be a dog scientist.

Where did they come from?

How did they evolve
from wild beast

to lapdog?

Fox behavior looks like dog.

It's impossible not love them.

How can dogs look so different,

yet still be dogs?

What lies behind a dog's
affection for humans?

Are dogs living with us
because we feed them,

or are they living with
us because they love us?

And could the answer

finally explain our species'
enduring friendship?

I feel that we've cracked
the puzzle of domestication.

"Dog Tales."

Right now, on "NOVA."

Humanity's best friend:

the dog.

They come in all
shapes and sizes.

But whatever the breed,

a pooch can make you
feel like a million bucks.

Hug.

Good girl.

They bring me so much

happiness and companionship.

I would dive in
front of traffic for her.

I would do anything for her.

Dogs and humans.

We're the best duo in
all of evolutionary history.

It's humanity's oldest friend.

The roots of our relationship

have long been a mystery.

But now, scientists are making
extraordinary breakthroughs.

Y'all let me know when
she's ready, and I'll start.

They're coming to the conclusion

that the bond
between our species

runs even deeper
than we thought.

And might explain how
these once-wild animals

became humanity's
perfect partner.

It's easy to love dogs.

That's my girl.

Mm, love you, too.

But how do they
feel about humans?

It certainly looks like love,

but could they just
be in it for the food?

Seems like an impossible
question to answer.

We can't ask them, but
could we read their minds?

Here in Atlanta, a unique
experiment is underway.

Kaylin is visiting
Emory University.

Good girl, all righty.

Good morning!

Hey!

Hey, Kaylin.

Good to see you.

She's part of a special project

run by Gregory Berns.

I know.

Okay, yeah, so are we
going to do some work today?

He's attempting to resolve
the biggest question about dogs.

The party line would say

that dogs, in some
way, are scam artists.

That in fact the only
reason that they live with us

is because we feed them and
because we provide shelter.

She is ready.

So the core of this
project is the questions

are dogs living with us
because we feed them

or are they living with
us because they love us?

And to me, that's all the
difference in the world.

To understand just
what a dog is thinking,

Gregory has trained them to lie
in a brain-imaging MRI machine.

Good girl, okay.

You know, the traditional ways

to understand what
dogs are thinking

is to look at their behavior.

But the problem with that

is that dogs will often
do things we don't expect.

Brain imaging gets
around these problems

by going directly to the
brain, and, in essence,

bypassing behavior and
go directly to the organ

that causes
everything to happen.

The dogs in the study

are trained to relate
toys to different outcomes.

When they see a pink car,
the dogs learn to expect praise.

When it sees a blue knight,

it learns to expect
some sausage.

By comparing those
two conditions...

the anticipation,
in particular...

to food versus human,

we can go in and look at
the reward system of the brain

and see which
one is higher or not,

or they equal, perhaps?

The level of pleasure
the dog experiences

is determined by the amount of
the neurotransmitter dopamine

the brain releases,

revealed on the scan
by increased blood flow

to specific regions.

Good girl... stay.

So, Laurie,

if you want to fade out of
view, and then we'll do the toys.

Gregory has conducted
this experiment

on numerous dogs.

And the scans are a revelation.

So, these colored areas
represent what dogs' brains do

when they're anticipating food.

It actually isn't showing
very much happening,

which means that on
average, the dogs probably

didn't care as much about
the food as we thought.

But, when expecting praise...

The dopamine levels
are regularly higher.

Now we actually do
see quite a bit of activity.

What that speaks to
is the fact that praise

is very interesting to the dogs.

Did they get one?

That was a good job!

The brain scans
show unambiguously

that most dogs love
praise just as much as food.

And some dogs love
praise even more.

Good girl.

Who's a good girl?

You are.

These results show
that a social bond

is as strong as the food that
we're providing to the dogs,

and that it's intrinsically
rewarding in and of itself.

And, to me, that's about
as close as you can say

that a dog loves you.

They are really special animals.

Our relationship from a
species-to-species level

just seems to be so
amazing and enmeshed.

So some may ask,

"How did humans
ever come to find

"an animal that seems
perfectly fit for us?

How did they ever
come to exist?"

The answer to
this canine mystery

lies in the distant past,

with an animal not
known for friendliness.

The wolf.

Folklore is filled with tales
of these frightening predators.

Even today, a wolf's eerie
howl can freeze blood.

Yet genetic research
has revealed that all dogs

originally evolved
from the gray wolf...

An animal that has roamed

the breadth of the
Northern Hemisphere

for at least 300,000 years.

The gray wolf may
look like a modern dog,

but it's a very
different creature...

an apex predator...

And ruthless carnivore

with a bone-splintering bite.

So how did that...

Give rise to this?

At the Royal Belgian
Institute of Natural Sciences,

paleontologist Mietje Germonpré

oversees a collection
of Ice Age wolf bones.

So, I have here a skull
of a typical wild wolf.

So, it's a big skull,
it's from a big animal.

And what is very special is
this long, elongated snout.

Now, I will show you a
skull of a modern dog.

So, you see immediately

that the snout is much
shorter and wider.

The relative proportions of
the skulls of wolves and dogs

are markedly different.

But in 2008,

Mietje made an
intriguing discovery.

She was studying a
30,000-year-old wolf skull

called the Goyet skull,

named after the cave it
had been excavated from

in the 19th century.

At that time, the
discoverers thought

it was the skull of a wolf.

But I was not very
happy with that

because it looked
different to me.

Mietje's careful measurements

backed up her hunch.

This was no ordinary wolf.

This skull is clearly smaller

than the skull of wild wolves.

The snout is wider and shorter.

More comparable to the
skull of the modern dogs.

The shape of the wolf skull

seemed to be halfway between
a wolf and a modern dog:

a proto-dog.

The Goyet skull was not unique.

Hunting through other
European collections,

Mietje uncovered more
dog-like wolf skulls,

also around 30,000 years old.

Could these strange-shaped
European wolves

be the ancestors of modern dogs?

Bones alone cannot
answer that question.

Scientists would need a
much more precise tool.

Oxford University is home to
the PalaeoBarn DNA laboratory.

Greger Larson is
the lead researcher.

We are trying

to establish a pattern
through time and space

of the different
genetic signatures

that dog populations and
wolf populations have had

across the world over the
last 20,000 to 30,000 years.

Thanks to recent advances
in sampling technology,

forensic DNA examinations

can now be conducted
on prehistoric bone...

Allowing them to compare

Mietje's 30,000-year-old
specimens

to modern dog DNA.

If dog domestication took
place 30,000 years ago,

and there was an unbroken
line between those dogs

and the dogs that
we currently have

sleeping on our sofas,

then you would expect

that the genetics of those
dogs 30,000 years ago

would match the
modern populations.

But the limited genetic
information that we have

from the canids that would
be dogs from 30,000 years ago

doesn't match
modern dogs at all.

Mietje's 30,000-year-old
European proto-dogs

appear to have
left no descendants.

But Greger's team
also tested samples

from nearly 100 other
prehistoric canids.

And in this data,
they have found

the earliest known
ancestors of modern dogs.

Between 12,000 and
15,000 or 16,000 years ago,

we do find specimens
that are starting to possess

genetic signatures
that match those

that we find in
modern populations.

But it isn't as simple as
a single ancestral line.

They found several
spread across Eurasia.

So it looks like, within dogs,

we have three geographically
partitioned populations

that are differentiated
genetically and geographically.

The three ancestral
dog populations

and Mietje's extinct proto-dogs

do, however, share
one thing in common,

something that may give a clue

to how dogs appeared
in the first place:

They were all found at sites

associated with
another creature...

humans.

Archaeological evidence
shows that 40,000 years ago,

modern humans began
moving into Northern Eurasia,

replacing the Neanderthals
who came before them,

and apparently
initiating a transformation

in the wolves they encountered.

Really, something
is, was going on there.

Once modern humans
arrived in Europe,

we see that the wolf
remains start to change.

The evidence
suggests dog-like wolves

may have appeared several
times over the thousands of years

since people arrived,

always in places where
wolves and humans

shared hunting grounds.

The formation of
a close relationship

between people and wolves

led to dogs, because
that's what dogs are.

They are an emergent property
of a very close relationship

between wolf populations
and human populations.

But how did it happen?

How does a wild animal
become a domesticated pet?

The answer may be found
not with lifeless bones,

but with the help of one of
the wolf's distant living relatives,

the fox.

Almost 2,000 miles east
of Moscow lies the location

of a unique experiment
in domestication.

On this isolated farm,

Russian scientists have
been breeding foxes

for more than 60 years.

Their aim has been
to better understand

the effect of human
contact on wild animals.

Today, the foxes
are being inspected

by scientists
Anastasiya Kharlamova

and Daria Shepeleva.

The experiment starts

with a population of
untamed silver foxes.

Each one is subjected
to a simple test

of human toleration.

To understand the reaction
of animals toward human,

we need to open
the door and try to,

try to put our hand
inside the cage.

Ooh.

They are testing the strength

of each fox's adrenal
fight-or-flight response.

He afraid,

but he demonstrates
the aggressive reaction.

The level of reaction depends

on the size of the individual
animal's adrenal gland.

Within a population,

there is always a
range of responses.

This fox is calm, without
any aggressive sounds.

I can touch it, and
the fox doesn't bite me.

But this one demonstrate
more fear reaction

without aggressive reaction.

She demonstrate some
interest in moving toward me.

How each fox responds
determines its future.

Once a year, the foxes are bred.

Around five to 20%
of the most extreme

of both tolerant
and intolerant foxes

are chosen to seed
new populations.

After just ten generations
of this selective breeding,

the results are
obvious and dramatic.

This shed contains
foxes bred for intolerance.

All of them are
extremely aggressive.

This one will try to bite me.

The experimenters
have discovered

that they can create animals
that are dangerously antisocial.

But they have also discovered

that if you breed
foxes for tolerance,

something quite
remarkable happens.

There is population
selected for tame behavior.

And the result is, the
behavior looks like dog.

Zolotoi!

Zolotoi!

Their adrenal reaction
is markedly subdued.

They are now as relaxed
in human company

as a household pet.

All of them love people.

Love all people.

They even wag their tails.

It's impossible not love them.

The experiment suggests

that by selecting
for human toleration,

in just a few generations,

a wild animal can
be made to behave

just like a domestic animal.

But that's not all.

We select our foxes
only for behavior,

but it's interesting
that after the selection,

we have a lot of
morphological changes.

Such as...

For example, a lot of
white in her fur color.

This fox has a white nose,
white belly, white legs,

and white necks.

Some foxes even
develop curly tails.

Curly tails and white patches

are both often seen in
other domesticated animals.

What's great about
that experiment is

that what it demonstrates is

that by a continued
very strong selection

for a behavioral trait,

that you can then get
an increase in frequency

of a wide range of other traits

that were not being
selected for at all.

What that suggests is
that there's a lot of linkages

between the overall
shape and size

and way in which the animal

is put together from an
anatomical perspective

and the way that it behaves.

Some believe this combination

of behavioral and
physical changes

is part of a
domestication syndrome,

probably caused
by a genetic mutation

that reduces the effect of
special neural crest cells.

During development,
these multipurpose cells

control the ultimate
size of the adrenal gland,

determining how friendly
the animal will tend to be.

But the same cells also affect
the size of the face and legs,

rigidity of the ears and tail,

and the extent of
color in the coat.

Select for friendliness,

and every other quality
can be affected, as well.

The experimental methodology
has been challenged recently,

but it's now widely accepted
that selection for behavior

can rapidly domesticate
a wild animal.

But in the journey
from wolf to dog,

who made that selection?

Most scientists now believe
it was the wolves themselves.

Wolves are
extraordinarily adaptable.

Different packs specialize

in hunting different
types of prey.

It's thought that when
humans first arrived,

some packs may have
adopted a novel survival strategy.

It's not crazy to think
that there may have been

a population of wolves
that found themselves

attracted to people and
started following people

in the same way that
other wolf populations

have started following caribou.

Rather than hunting,

these wolves would
thrive by scavenging

close to human encampments.

But only the boldest
would hang around for long.

These adventurous
wolves would breed,

and over generations,

evolve into an increasingly
human-tolerant subspecies:

the domestic dog.

Survival of the fittest

turned out to be
survival of the friendliest.

Over the last 15,000
years, dogs have taken on

all shapes and sizes.

At this show in North Carolina,
there are dogs of every sort.

Wow.

Veterinarian Debbye Turner
is fascinated by this variety.

Hey, look at that!

That's the occupational hazard.

Domesticated dogs
have been around

for thousands of years.

And they all come
from their wolf ancestor.

And when you think about that,

that's just absolutely
incredible...

that a big old,
um, Irish wolfhound

comes from the same ancestor

that a little tiny
Maltese comes from.

So what did the first dog,

the ancestor of
all these animals,

look like?

To find out, geneticists
have been decoding

the dog family tree.

Their results show that
some lineages split away

more than 5,000 years ago,

creating descendants who today

may reflect the appearance
of the original dog.

The Japanese Akita is
one of these ancient breeds.

These dogs separated
from the genetic line

very early on.

They are called
a Spitz-type dog,

which means they have retained
many of the characteristics,

the physical characteristics,
of their wolf ancestors.

So they have a
wedge-shaped head.

They've got these
pointy pricked ears,

they have a double coat,

and the curled tail
over their backs.

Sharing the same
curly-tailed trait

is the venerable
African Basenji.

Basenji is the granddad
of ancient dogs.

However, they're
not that trainable.

They will not do obedience
tricks like other breeds.

Come back here.

And here's an example!

There's something else
very wolf-like about a Basenji.

Its yodel.

These breeds reveal
much about how dogs

may have appeared and acted

after they first transitioned
from pack hunters

to scavengers.

And provide clues as
to why they may have

first appealed to humans.

You won't see
Basenjis doing tricks.

But because of their
closeness to their wolf ancestors,

they, um, are considered

very adept hunters.

As dogs were evolving

from wolves into truly
domesticated dogs,

their traits began to change.

They were smaller, their
snout length changed,

the strength of the muscles
that support the jaw change,

even the strength
and size of their teeth.

So they lost the ability
to take down big prey.

But they didn't lose everything.

Dogs are still the
standard bearers

when it comes to detecting
things with their nose.

A dog's nose contains 50 times
the number of olfactory sensors

as a human nose,

giving them a sense of smell
100,000 times more acute.

Combined with sharp
sight and hearing,

superb stamina, and
a docile temperament,

for humans, they were a
ready-built hunting companion.

The reason why the relationship

between dogs and
humans in a hunting situation

is so perfect

is because they
complement one another.

The dogs are the chasers,

the humans are the finishers.

15,000 years ago,

the first working
partnerships were formed.

Over the following millennia,

humans would breed dogs

to take advantage of
their wolf-like abilities.

But those selections cannot
explain the extreme variety

of body shapes we see today.

Instead, the genetic studies
indicate that a sudden explosion

of diversity in shape and size

can be traced to
a breeding craze

that began in Europe just
a few hundred years ago.

The very first kennel club was
established in 1873 in England.

And it's from there that
we get the vast majority

of the varieties and the
breeds that we see today.

Kennel clubs were breeding
organizations originally meant

to preserve local
dog characteristics.

But members began to select
and share dogs with extreme traits

to an extent never
attempted before.

Geneticists have discovered

that as a result of
this intensive breeding,

the look of Western dogs
has become controlled

by just a handful of
extremely potent genes.

In a human, over 100
genes will determine

a few inches' difference
in a person's height.

But in a dog, just seven
super-selected genes

now control the size difference

between the smallest
and the largest.

In nearly all breeds,

just one gene is
responsible for short legs.

And mutations
in just three genes

express the majority
of coat types,

from smooth...

To long-haired...

To whatever this is.

So, most dogs today
look the way they do

because of intensive
human breeding for novelty.

But people still value dogs

not just because
of how they look,

but because of what
humans can do with them.

For thousands of years,

the dog's natural
instincts were exploited

to help humans hunt,
herd, and protect.

But in the last century,
their roles have multiplied.

Dogs are amazing.

We can train them to
do a variety of tasks.

So from very simple
ones that amuse us

to very useful things.

You're not going to have a
cat at airports sniffing out drugs

or a horse telling you that
you're about to have a seizure,

but dogs are able
to do this in a way

that just vastly supersedes
any other animal,

and I think that's what
makes them special.

So what is the source of a
dog's amazing ability to learn?

Animal behaviorist Clive Wynne

is obsessed with understanding
what's going on in a dog's head.

Most psychologists
study the minds of people.

I became fascinated in the
minds of everything except people.

And so I became very
interested with dogs,

and very, very quickly,

I became totally, totally
grabbed by this amazing animal.

They're absolutely
fascinating...

their minds, their
intellects, their cognition.

Zaph...

Go.

Good girl.

For many years,
scientists have believed

that dogs are great learners

because they possess an
almost unique intelligence.

One key proof was their
skill at the pointing test.

Okay, Zaph...

Oh, what a clever doggie.

What a clever
doggie... well done.

Most pet dogs most of the
time will follow a human point.

It seems quite undramatic
to us because we're used to it,

but actually, it turns out

that not very many
animals will do this.

Okay, you ready?

Even our closest primate
cousin, the chimpanzee,

will struggle with this
test of intelligence.

But are their exceptional smarts

really what makes
dogs so special?

Maybe the answer lies in
the minds of their ancestors.

In the woods outside
Vienna, Austria,

Friederike Range is
taking her wolf for a walk.

Here at the Wolf Science Center,

they're carrying out cutting-edge
research on wolf cognition.

Sit!

You're ready to go.

The center's 15 wolves have
been brought up by humans.

I know Aragorn 11
years and three months.

So I hand-raised him
and his other pack-mates.

Alongside its wolves, the
center raises a group of dogs,

giving both sets of animals

an identical amount
of human contact.

We bring up the wolves
and the dogs in the same way.

So they have the
same experience,

and this is really crucial if
you want to compare them,

and compare their
behavioral cognition.

Friederike's team conduct
identical intelligence tests

on their dogs and wolves.

We just get it there.

Yup, and now it's working.

So what we are doing here

is testing cooperative
abilities in our dogs and wolves.

For this, we have this table.

The food on the table
can only be reached

if both ends of the rope
are pulled at the same time.

So the animal must understand
that it has to cooperate

with a human partner.

This dog shows how it's done.

Waiting for the human, he
executes the task to perfection.

That was nice!

But what about a wolf?

He's actually waiting!

Perfect!

For years, it was thought
wolves were incapable

of making the
cognitive leap necessary

to work with humans.

But these experiments
are proving the opposite.

And this result is not unique.

The team's work is showing

wolves can be highly
intelligent in multiple ways.

I don't think that a dog
is smarter than a wolf.

I think most of our studies show

that actually, the
wolves are much smarter.

Wolves have even been shown
to match dogs at the pointing test.

So, despite appearances,
hanging out with humans

did not improve the
dog's raw intelligence.

This ability

is not something
that developed in dogs

during the process
of domestication.

It was already
latent in the wolves

from which all of our
dogs are descended.

Good boy, scoot forward!

If dogs are no more
intelligent than wolves...

then why is a dog
more trainable?

Some think it may all
be a matter of attitude.

For Clive,

the mindset of his pet
dog Zaphos holds a clue.

I could tell straightaway
that Zaphos wasn't smart.

She's not a
super-intelligent dog.

But there was something
remarkable about her.

And that was so
obvious once I saw it...

this ability, this
capacity, this desire

to form strong emotional bonds.

That she's always
trying to make friends.

That she's extremely loving.

And I began to wonder,
could this be the crux ability

that has made
dogs so successful?

To demonstrate his theory,
Clive uses a simple test.

It's called the circle test.

It quantifies how
socially engaged

an animal is.

The animal is placed in a room
with a human for two minutes.

An observer totals the amount
of time the animal spends

inside the circle,
near the person.

Paired with their owners,

dogs spend upwards
of 60% of their time

inside the circle.

Even with a stranger,
Zaphos stays close

for over half the time.

Dogs just seem to like people.

But wolves behave differently.

This is not a lab environment,

but the results from this
circle test are still clear.

This young woman was
involved in raising this wolf.

They've known each other

all the wolf's life.

And, uh, nonetheless,
the wolf doesn't spend

so much time inside this
circle as a dog would do.

The wolf spends even
less time with its handler

than a dog would
with a stranger.

The fact that the wolf
doesn't want to spend

as much time inside
the circle with the person

shows us that the
wolf doesn't have

that same intense level of
social connection with people

as a dog can have.

To those who know wolves
well, this is no surprise.

A dog you can usually
always get to do what you want.

The wolves could care less.

They do it as
they want to do it,

and you can work really
hard to convince them,

and sometimes,
you are successful.

But if they don't want to,
there's nothing you can do.

Dogs inherited
their intelligence

from their wolf ancestors.

But they've also
evolved a strong desire

to bond with humans

that makes them
uniquely trainable.

Yes, good girl!

Often, in working dogs,
what makes them good?

It's a partnership. Good girl!

That dog and that
human that it cares about...

they're the unit.

The unit is the person
and the dog together.

But the dog's desire to
bond is not just the key

to incredible feats of learning.

This bond also appears
to be unusually powerful.

So much so, that
here in California,

it's being exploited

to provide a novel pathway
for human rehabilitation.

Meet Max.

Max, good job.

He's part of a groundbreaking
program using dogs

to transform the
behavior of individuals

who are a danger to society.

Ready to go in?

Max will ultimately
be a service dog.

But much of his training
takes place behind bars,

at this prison
facility in California.

He will be in the care
of long-term inmates

convicted of serious crimes,
from armed robbery to murder.

Many are repeat offenders.

Some, like Gerry
Castillo, arrived in prison

with deep-rooted
psychological struggles.

Hi, how are you?

Good, how are you? Good.

I spent a lot of time by myself.

I had issues of, uh...

Say, uh...

Low self-esteem.

You know, low confidence.

I was antisocial.

The prison environment

only seems to make
these problems worse.

It's in a place where
you don't have feelings.

Everything is shut off.

People don't talk about
emotions unless it's anger.

Statistically,

over half of all
prisoners in the U.S.

will re-offend on release.

Some prisons seek
ways to reverse that trend.

And in this facility,
that means dogs.

One wing has been transformed
into a virtual kennel club.

The prisoners here are
each responsible for a dog.

Man and animal
live together 24/7.

I got to get up in the
mornings and feed him,

and train him, and
take him out to potty,

and just care for
him the whole day.

Even if I'm having a bad day.

Just start making a big circle.

Max's time inside
will help transform him

into an elite service dog.

Just make, keep going, circle.

But it's the transformation
in the inmates

that seasoned prison
staff find most remarkable.

Leave your dog on a sit-stay.

It's amazing.

Max!

Come here!

It, it has changed
so many of them.

Good boy.

It's wonderful to see

the caring attitude
that goes to it,

the gentleness that's put
forth through and for the dogs.

You wouldn't expect to
see that on the streets.

I see it here firsthand.

Good, Gerry!

He is my friend.

You know, he makes my day.

We bonded.

He knows me better than me.

I want you guys
to sit down first

and lure them over your legs.

By getting a dog,

it's like I'm back
with a family member.

I can actually interact
with somebody

and share my feelings
with somebody.

You could hug your dog.

Max has lifted my self-esteem,

gave me a purpose

to... to do...

to do things for someone else.

They should be nice and calm.

There is mounting evidence
that even with convicts,

the profound relationship
between dog and man

can change their
whole outlook on life.

Good.

Since this program has started,

I've had six inmates
who have left on parole

and they have not come back.

They have not hurt anybody else.

They are still
maintaining their lives

on the outside.

Now let's do
another nice little jog.

This program taught them
that there's more to life

than just themselves.

Giving people who,
by some standards,

have been written
off as unlovable,

and to have them
have the opportunity

to love and be
loved unconditionally

by this amazing creature
that loves to be loved,

that is loyal, that
wants to please you...

I love the idea of
these programs.

A dog's uniquely
strong desire to bond

may be particularly
beneficial to humans.

But dogs seem quite happy
to spread the love beyond us.

What makes dogs special is,

dogs can form very
strong loving connections

to members of any other species.

Never mind other members
of their own species,

any other species.

Dogs appear to
be not just loving,

but almost
indiscriminately affectionate.

New research suggests
that this could be

partly because dogs get flooded

with the "love
hormone" oxytocin.

And the reason for
that may lie partly

with some very special genes.

Hi!

How are you?

Nice to finally meet you!

Come on in to our humble home!

Hi! Welcome!

Okay, you ready to
make some doughnuts?

Let's cook her up,
sister! Cook her up.

Okay, you got it, girl.

16-year-old Callie Truelove
lives with Williams syndrome,

a debilitating genetic condition
affecting one in 10,000 people.

Two-thirds cups of water.

This is gorgeous water.

♪ We're gonna
whisk it, whisk it ♪

It's caused by alterations
in around 30 genes,

generating multiple
developmental problems

and learning challenges.

I'm going to put
them in the oven.

There ain't nothing like
Southern-style cooking.

But through it all, Callie
radiates an incredible warmth

towards the people around her.

She just loves people.

From the time she was able
to go to somebody by herself,

she's always been very friendly.

Yes, let's do it!

They're so gorgeous!

And I love each and
every single human being

on this whole entire world.

If I could just hug all of
them at once, I would,

'cause I love them so much.

Here's what you're gonna do,
you're gonna take a doughnut...

She absolutely does love every
single person that she meets.

I've pastored a
church for 20 years,

and Callie has
reached more people

just with her everyday life

than I possibly
could in a lifetime.

I think you should
have this guy.

Callie's hyper-sociability is
a side effect of her condition,

tied to changes in three genes,

one of which supercharges
oxytocin levels.

Mm-mm!

Mm-hmm.

We got a pet down here.

Surprisingly, people
with Williams syndrome

may not be the only ones
affected by these altered genes.

♪ Oh, Doodle

This is my service
dog, Doodle Dandy.

And he's my heartbeat.

He's my sunshine.

And I can't imagine
my life without him.

Good boy.

He's helped me
through a whole lot

and he's just the best dog
in the whole wide world.

And I ain't ashamed to say it.

New research suggests
that Callie and Doodle Dandy

share more than
just a friendship.

Geneticists working with Clive

have recently discovered
the same rare mutations

that cause Callie's
hyper-sociability

are present in the dog genome.

But they are not
found in wolves,

suggesting these rare
mutations were acquired by dogs

during domestication.

What causes dogs to be
so much more sociable,

so much more socially engaged

and desiring
loving relationships

than are wolves

are due to three of the genes

that are involved in
Williams syndrome.

I feel that we've cracked
the puzzle of domestication.

We've identified in
the genetic material

what it is that makes
dogs so unique,

and makes them so
special and so successful.

More research is still needed,
but these rare mutations

may prove to be
the secret source

of the unshakable bond
between our two species.

I think that's brilliant,

because I knew
when he was little

he had my personality,

but I didn't know we shared
the same gene, almost.

So that, that is so cool.

I promise I'm always going to
be here for you no matter what...

through thick and thin.

Dogs and humans have
been on quite a journey.

A natural instinct to exploit
their new human neighbors

led wolf evolution from vicious
predator to docile companion.

Humans have tinkered with
them through selective breeding,

perfecting useful
instinctual traits

and playing with their looks.

And it seems like
somewhere along the way,

we bred in an extreme motivation
to learn extraordinary skills.

Because we bred in the
most important trait of all.

You can hug your dog...

The discovery that
dogs experience love,

that's why they're so perfect.

Are you the most beautiful dog?

That's the thing that explains

not only how dogs
became so domesticated,

but explains why
they're man's best friend

and why we've been
together for 15,000 years.

Who knows you better
than your best friend?