Nova (1974–…): Season 46, Episode 22 - The Violence Paradox - full transcript

It is an epic story...

spanning all of human history.

This man was shot
at a distance twice with arrows.

Torture was legal,

it was administered
in front of a judge.

An age-old battle
between our inner angels...

We can see how the human mind
is fundamentally built.

...and our demons.

We're at war with ourselves.

But one with a surprising twist.

Contrary to what we might think
from the news every day,



rates of violence are actually
declining over time.

The decline of violence

might be the most significant
development in human history.

Has violence really declined?

A lot of people just don't
believe this.

You will not replace us!

It is extraordinarily
controversial.

It's an interesting hypothesis
to test.

The stakes couldn't be higher.

This is about
our very existence.

Now science is tackling
violence.

We're saying, like, "Here are
things that we could do."

From the streets of Baltimore...

We can see shootings



go down.

To war-torn regions of Iraq.

We're not just testing things
in a lab environment,

but we're really testing these
in the field.

We've done something right.

Let's figure out what it is
and keep doing it.

Are we on the path
to a more peaceful world?

It takes just one war
to destroy the whole trend.

"The Violence Paradox."

Right now, on "NOVA."

Major funding for "NOVA"
is provided by the following:

The shooting started.

Shots fired. More shots fired.

This was the horrific picture

just moments after
the white van...

Multiple fatalities is
what we're hearing

from officials at this moment.

Kim Jong Un has detonated
what is widely believed

to have been a hydrogen bomb.

The world has devolved
into a place

where nobody can feel safe.

Wars is everywhere.

It's every corner of the world.

At least 40 people were
killed...

Every day, when you're
on the news,

there's more and more violence.

There has been tear gas,

they have been pepper sprayed.

I'm afraid for my children

in the world that
they'll grow up in.

They let loose a hail
of bullets.

It keeps getting worse.

And this time, gunfire aimed

at elementary school children.

This is the 22nd school shooting
this year...

There's gun violence,
police brutality...

I can't breathe.

People coming
and attacking our country.

The first of the two
explosions...

That could happen to my city.

That could happen to me.

The world is through
and through a violent place.

That's just a part of existence.

Is this who we are...

a species doomed to kill
and be killed...

a never-ending cycle
of violence?

The reality is that

we may be living in
one of the most peaceful eras

in human existence.

Peaceful?

Could this possibly be true?

Violence has been in decline.

But that just doesn't count
as news.

You just never see
a journalist saying,

"I'm reporting live
from a country that's at peace,"

or "a school that hasn't been
shot up."

Psychologist Steven Pinker was
reading an obscure text

when he came across a chart
that piqued his interest.

It plotted a steep decline
in rates of homicide in England.

Once I stumbled upon this graph,

I mentioned it in a blog post,

and then I received
correspondence from scholars

in a variety of fields,

telling me that I could've made
an even stronger case.

Intrigued, he looked further.

I saw dataset after dataset,

all of which showed declines
in violence,

in different parts of the world,

with different kinds
of violence,

and I realized there was a story
that needed to be told.

A story that spans the entirety
of human history,

drawing on disciplines from
archaeology to neuroscience,

and has the potential to turn
conventional wisdom on its head.

To me, it's absolutely huge.

If we think that life is better
by going back into the past,

we're making
a very serious mistake.

The greatest thing
that's happened to humanity

is that we've lowered our rates
of violent death by 90%.

This is the big story.

But could it be too good
to be true?

The demographics of the past
are not at all clear cut.

And so as a result,
we're making comparisons

that we're drawing
literally out of thin air.

There's so many people
who would hear Steven Pinker

and think,
"What world is he living in?

This-this isn't my life at all."

It depends on who you are
and where you live.

North Korea's nuclear test...

Steve's overarching claim flies
in the face

of common sense.

That can't be true!

The Cossacks are always coming,
there's always danger.

We may or may not agree
with his conclusions...

but it is important

to understand the trends
of violence

so we can prevent,
if possible, violence today.

It's a controversial argument,

but if physical violence
really has declined,

it presents us
with a huge opportunity.

To point out that
things were worse in the past

is not to say, "We should relax,
our problems are all solved."

Quite the contrary;
it's by understanding

how our predecessors were able
to drive down rates of violence

that we can be emboldened to try
to drive them down even further.

Has violence declined?

And if so, can we uncover clues
in our past

to make us safer today?

To find out,
we have to go back, way back,

to some of the earliest records
of human prehistory...

In one of the
most desolate places on earth.

Nataruk is a bleak part
of the landscape.

There's no vegetation,

and it's got a dark gravel
covering the surface.

Marta Mirazón Lahr started
excavating this site

seven years ago.

We arrived,
and already you could see

on the floor
all these fragments of bones.

The first thing we saw was
in this area

that we could see coming out
of the ground

the broken lower legs,
the shin bones, of somebody.

We started clearing
and excavating,

and the bones of another one
appeared,

so we would clean that one.

And the bones of another one
appeared.

We found the remains
of 27 people.

They're not graves
that have been dug or prepared.

They are in positions
that suggest

that they just lied
where they died.

What we have here is actually
an ancient crime scene.

A crime that took place
10,000 years ago,

when this desert looked
very different.

10,000 years ago,
you had a very large lake

that had formed a beach.

You would have had palm trees
and gazelles and hippopotamus.

It would have been
a really rich landscape.

So what we had was a population

of fisher-foragers,
hunter-gatherers.

And whenever there is something
that one group has

and another one doesn't, the
potential for conflict exists.

A conflict recounted in bones,

now buried in a remote storeroom
in northern Kenya.

You read them like a book.

And the skeletons are telling us
a bit about their life

but most about their death.

When we found this skull,

all we could see was
the back of the head.

But when we started excavating,

we could see the whole skeleton
lying face-down.

And when you turn it around,

you can see
this bone has been crushed in.

He received a blow
with a blunt instrument

and another one on the side
of the head.

And he wasn't alone.

Many of the skeletons bore signs
of violence.

There are injuries to the head
that suggest

there's a cut in the face
of the skull.

Injuries to the spine that
suggest projectiles, arrows.

And this one was bound
at the time of death.

Inside the ribs we found
the bones of a baby.

Something terrible clearly
happened here, but what?

One of the most striking
discoveries at Nataruk

comes from what was probably
the most difficult skeleton

to excavate.

However,

we discovered
the tip of an arrow

still embedded in the head.

We have direct evidence
that people were attacked.

But there's more.

The arrow tip was made
of obsidian,

a material that is rare

and of which we find no sources
locally.

And so it tells me that

the attackers actually came
from somewhere else.

It wasn't just
a chance encounter

between two groups fishing
that ended up in a fight.

Because if you go out fishing,

you are not carrying
this range of weapons.

The bones of Nataruk are
the oldest known evidence

of a planned raid...
a form of early warfare.

And I think that as a behavior,

as-as a characteristic
of human societies,

it probably goes back in time
much, much deeper.

The question is how deep?

The archaeological record
on every continent

shows massive evidence
of human-to-human destruction.

You know?

There's just no other way
of putting it, right?

The paleolithic record is
a horror show.

From Otzi,

the 5,000-year-old iceman found
with an arrow in his back...

It looks like a hit job.

To Kennewick Man,
8,500 years old...

a blow to the chest
shattering six ribs;

to Sima de los Huesos...
Spanish for "Pit of the Bones"...

where a 430,000-year-old
Neanderthal was found

with severe blunt-force trauma.

Head bashed in, indubitably.

There's even evidence
of cannibalism

on almost every continent.

You see violence time
and time again

in archaeological site
after archaeological site.

Of course, a handful of cases

may not be a fair sample
of the distant past.

How violent were we?

You can't answer that question
by particular incidents,

because there's violence
in-in all societies.

You really do have to count.

And that's exactly what a group
of Spanish scientists did...

scouring the records
of over 600 human populations

between 50,000 years ago
and today.

Surveying the evidence...
a bashed-in skull here,

an embedded arrow head there...

they found that the proportion
of prehistoric people

who suffered a violent death

was up to three times greater
than today.

I was stunned
at the high rates of violence.

There's nothing close
in any modern society.

What has changed,
and more importantly, why?

To figure that out,
you first need to understand

some pretty basic things
about us.

People often ask,
"Are humans violent by nature

or peaceful by nature?"

The reality is we're both.

Pinker views our history
as an epic struggle

between our inner demons
that push us toward violence...

and our angels
that pull us away.

The brain is a complex place.

It houses many circuits,

some of which incline us
toward violence

and some of which inhibit us
from violence.

That tension between acting
on an aggressive impulse

and restraining ourself

is fundamental in our brains,

because we are clearly
aggressive animals.

From body-slamming seals...

...to fighting fruit flies,

violence,
usually committed by males,

is something we share
with most animals on the planet.

Aggression is one of
the most common social behaviors

across the animal kingdom.

Almost every
sexually reproducing species

shows aggression.

Including us.

What in our brains drives
aggression?

That's what scientists
at Cal Tech

are trying to figure out.

These mice have been
genetically manipulated

so that certain neurons
in the brain

can be activated
by this blue laser.

There are groups of neurons

that if you activate
these neurons in a mouse,

you can trigger aggression.

In the lab, Tomomi Karigo
hooks up a mouse to the laser.

Now, at the push of a button,

she can remotely control
the mouse's behavior.

By stimulating
a certain brain region,

we can change the
emotional state of the mouse.

Just flipping the switch.

This animal is now
in an aggressive state,

attacking the other mouse.

There's some component of, like,
a volume-control knob here,

where as we stimulate them
more intensely,

we get more intense aggression.

Look what happens
when you turn the power down.

Now the light is off,

and the animal retreats
to the corner of the cage.

Not only are we able
to turn on aggression at will,

we can also stop a fight dead
in its tracks

by inactivating these neurons.

This experiment
in mouse mind control

has allowed them to pinpoint
aggression in the brain.

We've learned there are clusters
of cells deep in the brain

in a region called
the hypothalamus

that play a key role in
organizing aggressive behavior.

The same may be true with us.

Turns out
whether it is mice or humans,

we share some of
the same basic wiring.

The parts of the brain
that are in the mouse

that control these behaviors
are present in humans.

They are some of the most
evolutionarily ancient

parts of the brain.

So the wiring for aggression
runs deep.

But that's only half the story.

We have circuits in our brain

that incline us toward rage,
toward revenge, toward sadism.

On the other hand, there are
other circuits in the brain

that give us a sense of empathy,

an ability to feel
the pain of others.

Even babies have
a rudimentary sense of fairness.

So I think we're ready
for Ethan.

Would you like to bring him
into our testing room?

Karen Wynn is a developmental
psychologist at Yale

who has created
an ingenious experiment

to find out whether babies are
born with a sense of morality.

We're going to just
have you sit here...

I was interested
in the fundamental structures

of the human mind.

What do we bring with us
when we come into the world,

how do we understand the world?

Up goes the curtain!

To figure that out,

she puts on a two-act
puppet show for babies.

So this duck is looking inside
this box,

sees a nice toy inside of it,

and is trying to open the box
to get the toy,

but is not being successful
opening it.

And this green shirted puppy
very nicely helps the duck

so it can get its toy.

That's our nice puppet.

In act two, this nice puppy
takes center stage.

And now, our nice puppy is
playing with this ball,

and he very nicely rolls it over
to the blue-shirted puppet.

And the blue shirted puppet
rolls it nicely back to him.

That was a nice interaction.

Now this time he's going
to invite the other kitty

to play with him.

"Will you roll it back to me?"

"No."

He steals the ball.

What a jerk.

Hi!

Next, the babies are given
a choice.

Which one do you like?

Do they prefer the kitty
who was nice to the nice puppy,

or mean to the nice puppy?

If you give them the choice,

babies very robustly choose
the nice one.

Awesome job!

Even a three-month-old can look

at an interaction
between two strangers

and decide,
"Oh, that's a good interaction,

that's a nice human being."

Or, "That was a bad interaction,

that's a jerk,
I don't like that jerk."

Do you want to just show Dad
where to sit?

But that's just the half of it.

Watch what happens
when Wynn flips the script,

and babies see a mean version
of the same play.

Up goes the curtain.

This time this mean puppy
comes along

and slams the box lid shut.

He's not nice at all.

This time, the mean puppy is
the star of act two.

Just like his nice counterpart,

he gets treated nicely
by the blue kitty

and then meanly
by the orange kitty.

Do you see these?

Will the babies still prefer
the nice kitty?

Do you see this one?
Which one do you like?

No.

Now they consistently pick
the mean one.

Which one do you like?

Turns out that even at this age,

babies have the capacity
to make simple moral judgments.

Oh, good job.

It's like, "You're not deserving

"of having a friend play
a nice game with you.

"You treated someone else badly,

you should be treated badly
in your turn."

So that tells us that well
before their first birthday,

babies are already developing
notions of just desserts.

That is morality.

So both angels and demons
are baked into our biology.

We have both of these behavioral
strategies in our nature,

instilled in us through
the process of evolution,

and we switch between them

according to what we judge
as more effective.

If violence has declined
since prehistoric times,

what did our ancestors do

that tipped the balance
toward our better angels?

One of the first violence
reduction techniques

was the state.

Government can tamp down
the cycles of violence.

The human species has come
a long way

for thousands of years
to get where we are today.

Because of government,
we stay in line.

Until about 5,000 years ago,

humans lived
in small, nomadic bands.

But as agriculture took hold,
populations grew,

and the first governments
emerged.

As societies get bigger
and bigger,

more and more problems have
to be solved,

and the sort of almost
inevitable result of this

is people start
to form governments.

Governments that would need
more complex systems of rules...

and leaders to solve
those problems.

While those early kings and
pharaohs waged plenty of wars,

they had a strong incentive
to reduce violence

among their minions.

It's not that

the early kings and emperors
had a benevolent interest

in the welfare
of their citizens.

But just as a farmer has
an incentive

to prevent his cattle
from killing each other,

these early rulers wanted
to prevent violence

that deprived them of slaves
and soldiers and taxpayers.

Much of the decline of violence

is due to the existence
of the state.

Without government,
the potential for chaos is huge.

In fact, when researchers pooled
together the work

of anthropologists,
ethnographers, and statisticians

comparing those living
in a state society

to those who do not,
the numbers are striking.

Whenever there are data
that actually count the bodies,

you see that rates of violence
in non-state societies

are higher than in societies
with the rule of law.

Even so, for those living under
the world's first governments,

life was still pretty brutal.

In general,
rates of violence go down,

but when people are pacified
by a kingdom or an emperor,

it's not that
they're free of violence,

because the violence of people
killing each other is replaced

by the violence
of the state killing people.

Through pretty much
the whole of history,

one of the things you do if
you're the ruler of a society

is advertise just how violent
you're going to be

if somebody crosses you.

From the Maya, who sacrificed
to appease the gods...

...to the Romans,
who killed for spectacle.

...to Han Dynasty China,
where torture was legal.

And if you think early religions
were a paradigm of peace,

think again.

The Bible,
the so-called good book,

is one long cavalcade
of violence,

beginning with
Cain slaying Abel;

Noah's flood;

you have Samson killing
thousands

with a jawbone of an ass.

And then the Israelites
are commanded by God

to commit total genocide.

It would appear

that our ancestors were obsessed
with violence.

Sir, enemy fighters coming in!

And judging from our taste
in entertainment today...

Our battle will be legendary!

So are we.

Even the mild-mannered among us

can have a taste for violence,

especially when it comes
to revenge,

a pleasure we can witness
in the brain.

We're going to have you do

the competitive reaction time
task, okay?

Yeah.

Here we go.

Here at the University
of Kentucky,

David Chester scans the brain
of a volunteer

as they play a simple game:

who can press a button faster

when a red square appears
on the screen.

The winner gets to blast
their opponent

with an annoying sound
at a volume of their choice.

Remember that one and two are
pretty quiet,

and three and four get
pretty loud.

Okay.

The subject thinks

they are playing against
a real opponent,

but actually it's a computer.

And it's not going to play nice.

She just saw that
her opponent picked a four.

So now she's been
thoroughly provoked.

The volunteer seeks revenge.

She just picked a four.

Seems as though
she's a little upset.

Now, Chester can peer
inside the brain

at the very moment
of retaliation.

The scanner reveals
increased activity

in the ventral striatum,

part of the brain's
so-called pleasure center.

The circuits in the brain
that light up

are the same as the ones
that light up

when we crave chocolate
or gamble

or see an attractive person.

So the old saying "Revenge
is sweet" is literally true.

On this level,

it seems our impulses
haven't changed much.

But have we always acted
on them?

What do the numbers say?

As humanity moves
toward the Middle Ages,

the investigation turns from
archeology to written records.

Most human societies
historically

have not been in the business

of creating vast amounts
of writing.

The societies of the West are
rather unusual

in the amount of documents
that they created

and then successfully preserved.

The decline of violence is

by no means
a Western phenomenon,

although until recently,

a lot of the studies focused
on the West,

'cause that's
where the data were.

And some of the strongest data
was assembled by Manuel Eisner,

a historical criminologist
with a singular obsession:

murder.

Over the years,
I developed a little bit

of a obsessive interest

in trying to find
all the publications

in different languages

that had been written
on homicide.

"Robert of Chinehem hit Emmis,
daughter of Alice of Crotchall,

on the head with a stick
so that she died,

and he fled at once..."

"Evildoers came to
Thomas of Inglefield's house

and killed him."

"...this morning to my wife?"

And then he kills him.

It all started
when he read an article

that claimed that
since the Middle Ages,

homicide rates in England
declined 40-fold.

I thought, "This can't be true."

And so I started looking
at more evidence, more data.

Trouble was, the data didn't
exist in any one place.

Eisner had to go deep
into archives,

sometimes into the basements
of old town halls and churches,

brush off the mouse droppings,

and tally the causes of death.

I would be looking at court
records, prison documents,

account books, confessions,
or pardon books.

Each source added a data point.

Over the course of a decade,

Eisner was able to plot
homicide rates

for England, Italy, Scandinavia,

the Netherlands and Belgium,
Germany and Switzerland.

In the process, an astonishing
picture began to emerge.

All these dots
that I'd collected lined up

over 800 years
along one single line.

That was kind of, like,
just an amazing moment.

For every 100 years,

the homicide rate in Europe
was cut in half.

When Manuel Eisner showed that
this decline had happened

in pretty much
every European country

for which
we had continuous data,

I realized
this is a real phenomenon.

It is not just
the history of one country,

but it seems to be
a general historical process.

Eisner's work provided
hard evidence

of a decline in violence:

over eight centuries,
homicide rates fell

from one in a thousand
to one in a million.

The big question is: why?

When you realize that
rates of violence can change,

that something that our
ancestors did in the past

worked, it emboldens you
to try to figure out what it is.

One answer might be
what some social theorists call

"the civilizing process."

The civilizing process is
the idea that

as societies become
more interdependent,

we are penalized for behaving
in a violent way

against another person.

In Renaissance Europe,
commerce was booming...

ships brought goods
from around the world.

Violence among the masses was
becoming bad for business

and bad for the king.

If businesses want to trade,

they want to make money, and
people profit off that,

they live better lives
when the economy's going well.

There's an incentive for states

to prevent violence
from happening.

The theory is
this new economic order

went hand in hand
with a new set of social norms.

What changes is that as a man

your importance in society is
no longer ruled

by how good you are in fighting,

but it's governed
by how self-controlled you are.

According to some researchers,
self-control was something

that was sorely lacking
when one considers daily life.

The medievals were,
in a word, gross.

They would copulate
in-in full view.

At the dinner table,
they would gnaw on a bone

and put it back
in the serving dish,

drink from the plate,
smack their lips.

If you were out in public,

you might very well have to
relieve yourself in public view,

in a street,
in a bunch of holes on a bench.

And judging from these passages
from popular etiquette books,

things must have been
pretty... different.

"Don't foul the staircases.

"Don't relieve yourself
in front of ladies.

"Don't touch your private parts

"under your clothes
with your bare hands.

"If you come across something
disgusting in the sheets,

don't turn to your companion
and say,

'I should like to know
how much this stinks.'"

Well, these are laughable rules
to us now,

because we accept the idea
that you don't go around

urinating in front
of other people,

because how you treat people
matters.

But how in the world

could something as mundane
as manners

contribute to a decline
in violence?

Manners are a sign
of self-control,

of not acting on every impulse.

If someone insults you,
if someone steps on your toe,

you don't immediately
pull out a knife

and challenge them to a fight.

You hold your horses;
you count to ten.

As it turns out,

the connection between
self-control and violence

is long known
to neuroscientists.

We've known
for a long, long time

that violent offenders

have poorer levels
of self-control

than people who are nonviolent.

And that has to do
with the prefrontal cortex...

the area of the brain
thought to be involved

in planning and controlling
our impulses.

We've brain-scanned
41 murderers.

And we showed that
the prefrontal cortex

is functioning more poorly
in these murderers.

The red and yellow show
a normal level of activity.

The scans from the murderers

show dramatically
decreased activity.

Is there anything
that can be done

to strengthen
this part of the brain?

In today's session,
you will be completing

a series of survey questions...

That's what Raine's team
is trying to find out

here at the University
of Pennsylvania.

During the stimulation itself,

you will be completing two
cognitive tasks on the computer.

Yeah.

They get electrodes put
on the prefrontal cortex.

And they'll get 20 minutes
of stimulation.

You may feel tingling, itching,

kind of prickling sensation.

That tingling is stimulating
or upregulating

a specific part of the brain.

And then they are given
scenarios

of, "If you were provoked,
would you pick up a bottle,

would you hit somebody
on the head?"

We're looking to see

whether upregulating
the prefrontal cortex

reduces a person's intention to
commit a violent, criminal act.

We showed that by upregulating
the prefrontal cortex,

we're able to reduce criminal
intent by about 30% or 40%.

Is it possible, then,

that acquiring habits of
self-control like manners

could have had the same effect?

By giving somebody training
in exercising self-control,

that activity may flex
the prefrontal cortex

and enhance
that part of the brain.

It stands to reason that

if you practice
a set of behaviors,

that engages areas
of your brain,

which leads to a sort of
virtuous cycle, right?

It improves the behavior,
and then the behavior,

if you continue to engage in it,

allows you to further
strengthen the circuit.

The theory is self-control
laid the groundwork

for a cultural shift
away from violence.

And yet we all know "civilized"
is a relative term.

By some measures

Europeans may have become
less violent toward each other,

but at the same time
they were embarking

on one of the bloodiest chapters
in human history:

the colonial conquests.

In Europe during
these colonial regimes,

there's less violence
in the core of the empire,

but if you think about the lives

of the,
of the indigenous peoples,

life was treacherous,
life was awful.

The colonial projects is one

in which indigenous peoples
are either

physically and
violently repressed

or, in some instances,
eliminated entirely.

During that same period of time
that violence is going down,

you have something like
the transatlantic slave trade,

the largest forced
oceanic migration

ever to occur in human history.

These slave ships

that are plying the Atlantic
with human cargo,

these are mini war zones,
where you have mortality levels

that are between ten and
25 percent on every voyage.

And it lasts
for nearly 400 years.

Once they arrived,

many slaves were literally
worked to death.

In fact, much of the expansion
of the European

and later the U.S. economy

was built on
the violent exploitation

of the over 12 million people

forced into the
transatlantic slave trade.

And slavery wasn't the only form
of state-sanctioned violence.

There are a number of practices

that were routine
through human history

that we universally recognize
today are barbaric.

From infanticide as a routine
form of birth control,

to burning at the stake,

witch hunts,

and human sacrifice,

across the globe, heinous
practices were still rampant.

And Europe was no exception.

You had gruesome punishments,

sadistic forms
of capital punishment

like breaking on the wheel.

Breaking on the wheel is
incredibly unpleasant.

You were strung up
on a huge, wheel-like device

with your various limbs attached
to the wheel.

And the executioner would break
each one of your bones.

And then you would be left
to die of internal bleeding,

and people would watch.

Back then,
torture wasn't some random act

performed
by a sadistic psychopath...

but a routine part of the law.

It's hard for us
to imagine this,

but torture was legal,

it was administered
in front of a judge, usually.

But by the mid 1700s,

this gruesome jurisprudence was
quickly losing favor

in western Europe.

How do you get
from most people thinking

it's perfectly fine to do
unspeakable things to people

to a situation in which people
say, "This is disgusting.

"It's barbaric, it's horrendous.

We can't do this."

And this change happens
in a very short period of time.

To Lynn Hunt,
a historian at UCLA,

the answer has to do
with a notion often taken

for granted today.

Without question,

the single most radical idea
of the 18th century

is the idea of equality.

They live in an incredibly
hierarchical society,

in which everyone is supposed to
be deferential to their betters,

in which there are incredibly
rigid social divisions.

How do they think past that?

The idea of equality...

while at first reserved
for a small group of people...

had to come from somewhere.

And Hunt thinks it started
with the written word.

Literacy and
the expansion of print

had a very, very,
very big impact.

The first
mass-literacy societies,

where half or more of the people
in the society can read,

these come about in Europe
in the 17th and 18th centuries,

and it's driven almost entirely

by people wanting to read
the Bible.

But as people develop
this skill,

they realized,
"Well, of course I can use it

for a lot more than
just reading the Bible."

It wasn't just
that people could read,

it was what
they could read about.

Newspapers got people
to recognize

that there was somebody else
in another city

who is having the
same experiences as they are.

It is difficult for us living
in a hyperconnected world

to appreciate how big an impact
this could have.

Print newspapers
are incredibly important

in creating this broader sense
of community.

And it wasn't just newspapers...

the newly literate masses
developed a huge appetite

for the novel.

It allowed the reader

to really get inside
the mind of the characters.

You don't see
just what they're doing.

You see what they're feeling and
thinking as they're doing it.

They're writing in a way
to allow the reader

to enter into the life-worlds
of other people

and get empathy that would
drive them to political action.

Action such as
the abolitionist movement,

which was bolstered
by slave narratives

and popularized
by a single novel.

A book like "Uncle Tom's Cabin"
is bringing people

into a world that amplifies
the humanity of the enslaved

and, by extension, that
they are deserving of freedom.

The theory is
that reading novels

made people more empathetic.

But can fiction really do
all that?

There's psychological evidence
from laboratory studies,

that reading fiction
can build our care

even for different groups
of people,

groups who we might not care
that much about otherwise.

So, for example, one of
the most famous is what's known

as the "reading the mind
in the eyes" test.

"The mind in the eyes"...

a scientific experiment designed
to test empathy.

Participants are shown a series
of photographs of just eyes

and asked to guess the emotion.

Readers of literary fiction
score consistently higher.

You think of reading a novel
as a very personal thing

that's just, oh,
you're just, you know,

sitting on your couch indulging
in something.

But no, you're doing something
a lot more profound.

You're kind of going
to the empathy gym.

And things didn't stop
with the novel.

A parallel revolution in science

would seed
even more radical questions.

The scientific revolution
drives people

to ask these underlying
questions like, well,

"Why do things
in the way that we do?"

There was a new sense
of rationality,

where we want to understand
knowledge based on what we see

and what we can
actually document.

Observation, hypothesis,
experiment.

The modern scientific method
didn't just explain the stars.

It's like scientific reasoning
spills over

from the natural world...
the kind of thing that,

you know, Galileo and Newton
are interested in...

toward the social world.

Rather than accepting things

because that's the way
they always have been

or because that's
what God decreed

or because you can't criticize
the king,

people started to rethink
social arrangements

from the ground up.

It made some people think
about slavery.

It made some people think
about women.

It made some people think
about religious minorities.

But mainly it made everybody
think about equality.

Equality...

even though it was narrowly
defined to start with,

18th-century European thinkers
stoked the embers

on a revolutionary ideal.

Once you unleash
the light of freedom...

You know, we say in Africa that,
"When the sun rises,

"if you don't want to see it,
the only thing you can do

"is to close your eyes.

But the rest of the world
will see."

The cat is out of the bag.

Still, some ideas resulting
from the scientific revolution

were far from perfect.

And it's the same period in
which pseudoscientific racism

as we come to know it in the
second half of the 19th century

really begins.

Perhaps reason and empathy

helped fuel
abolitionist movements.

But at the same time, science
was co-opted to justify racism.

This is one of those scenarios

where we have to hold two
very difficult things together.

Things are not always
all good or all bad,

but they are a complicated
mixture of both.

And that balance
of good and bad,

according to Pinker, was
shifting in favor of our angels.

The rise of science doesn't mean
racism was eliminated.

But it's not a coincidence

that the first systematic
arguments against slavery,

against cruel punishment,
against imperialism

were made around that time.

Ideas matter.

But did those ideas change
people's attitudes

toward physical violence?

Where's the evidence?

Turns out, some clues were
hidden in plain sight...

in the records
of the Old Bailey,

the central criminal court
of London.

The Old Bailey proceedings are,
in my estimation,

the most detailed account
of everyday life

ever produced in print.

Tim Hitchcock spent 15 years
digitizing 239 years

of court proceedings.

They cover the period
from 1674 to 1913,

and they encompass 197,745
different trials.

It is the largest body
of recorded speech

anywhere in the world.

But this giant anthology
presents a giant problem.

At 197,000 trials,
nobody's ever read all of them.

It's huge, right?

It's, it's unreadable.

Enter Simon DeDeo,

a data scientist at
Carnegie Mellon University.

He has a hunch that computers
can see patterns in history

that no human can.

I'm interested
in how people see the world.

And if I want to see it
really big scale,

over the course
of a couple of centuries,

then I have to do a very
different kind of science.

And to do that,

he would need
a really big data set.

Hitchcock's 127 million words
would do just the trick.

Somebody whispers in our ear,

"Hey, there's this stuff sitting
out there in Britain."

That, for us, is a gold mine.

We met at a pub
for a couple of pints of beer.

And where we ended up was
with the realization

that there were techniques
that would allow us

to pull out human behavior

from this 127 million words
of transcribed data.

But how?

A computer can't read,
it can't understand,

you can't have a conversation
with it.

So what we have to do is
transform all of those trials

into something that a computer
scientist can manipulate.

Here's where Tim had an idea...

"How about we use
'Roget's Thesaurus?'"

Roget, in the 19th century,
sat down

and went through the dictionary,

and assigned every word
to a particular meaning.

He groups them
into collections of words

that all kind of mean
the same thing.

Words like "cut" and "thrust,"
"lunge," "kick," "punch."

All of those words mean,
of course, different things.

It's one thing to punch
somebody,

it's another thing to kick
somebody.

What Roget's classification
allows us to do is say,

"Look, forget the details.

These are all examples of
category 716, attack."

And that enables the computer
to summarize a trial.

What quickly emerged from
the analysis of the proceedings

was that the words spoken
in court

reflect powerfully
attitudes towards violence.

The way in which
the state defined crime

and chose to prosecute crime
was changing decade by decade.

For example,
in the earliest accounts,

the number of violent words

often had nothing to do
with the crime charged.

"1770.

"John Jones and Isaac Ely
of Saint Sepulchre were indicted

"for assaulting James Lowe
upon the king's highway.

"One of them immediately stabbed
him with a knife on the breast

"and at the same time, they
catched hold of his hat and wig,

value 15 shillings."

Despite the violence
of this assault,

the eventual indictment was
for theft.

But in later cases,
that changes.

Violent words strongly correlate

with being on trial
for a violent crime.

1909, William Musson was caught

trying to steal goods and money

from the Commercial Gas Company.

But in the process he also tried

to choke, suffocate, and
strangle one of the guards.

In this instance,
the robbery itself

didn't figure in the trial
to any extent.

And instead what they focused on

was the violence
of that assault.

The records of the Old Bailey
are hard evidence

of a cultural shift away
from interpersonal violence.

People became much less tolerant
of violence.

The idea that
a pub fight is normal,

the idea that carrying a knife
or sword was normal.

By the early 20th century,

people were expected
to settle their disputes

in ways that didn't involve
breaking a nose

or taking out a couple of teeth.

A decline in homicide...

a retreat from
heinous practices...

and a cultural shift
in attitudes.

But these data are only
for Europe.

What about the rest
of the world?

Can we actually draw
some universal

based on the European history?

I would say yes and no.

No, because Europe is a small
backwater for all of humanity,

but yes, because
in the last 500 years,

European philosophical,
economic, and political systems

have spread around the world
and had massive impact.

I focus on the West because
that's where the data are best.

But if this is
a general historical process,

it has to be shown worldwide,

and in many cases it has been,

such as data on rates of death
in warfare.

That comes
from all over the world.

But surely the data from
the 19th and 20th centuries

would paint a grim picture
of the world.

From the Napoleonic Wars...

...and the Taiping Rebellion...

to the massive
colonial conquests...

...and two world wars

capped by the dropping
of the atomic bomb...

...how in the world could
we be getting less violent?

World War II undoubtedly was
the most destructive event

in human history.

But more people were alive
in the 1940s

than were alive
in earlier periods in history.

So we also have to take
into account

just how many people there were.

In absolute numbers,

World War II may have killed
the most people.

But compare the death toll

to the number of people living
at the time: 2.3 billion.

Looking at it this way,

there were far deadlier events
before World War II.

When you plot how many people
get killed

as a proportion
of the world's population,

you can appreciate
some of these trends.

By this metric, World War II
falls to number eight.

The deadliest?

The 13th century
Mongol conquests

launched by Genghis Khan,

which reportedly killed
roughly 40 million people...

almost ten percent of the
world's population at the time.

Of course,
that's just an estimate.

But there's one other number
worth considering...

zero.

That's the number of wars waged
directly between

the major powers
since the Korean War.

The big national armies
are not fighting each other.

That's not some data
construction, that's a fact.

Of course major powers have
invaded smaller countries...

and had a hand in
numerous civil wars.

But overall,
deaths from every form of war

have been on the wane.

War's like a cancer
that used to be spreading

and now it's in remission.

It's getting
smaller and smaller,

the tumors are shrinking.

There are not too many periods
in world history

where we've observed such
a steep decline in violence.

So how did we get from here...

...to here?

Is it possible that something
inside us has changed?

We know that violence

has been decreasing
in human history,

and we have a lot
of explanations

of why that might be,

whether they be social forces,

or the way we think, the way
we structure our society.

But here we can offer a
biological explanation as well.

A biological explanation

that pins some of humanity's
push toward peace on evolution.

But to understand it,
you have to look

at a groundbreaking experiment
in 1950s Russia.

They took a population
of wild foxes,

and they just bred them
solely for tameness.

The ones that acted
the friendliest,

they bred those together.

By breeding the most docile
foxes in each generation

to each other,
over the generations,

they ended up with something
that looked remarkably

like a domesticated dog.

The foxes' behavior changed,

and so did their
physical appearance.

The skulls became shorter,

and also proportionately wider.

The new shape of the skull
appears to go along

with decreased aggression.

Over several generations,
the foxes became domesticated.

Is it possible that
over a much longer timeframe

something like this
has happened to humans too?

A kind of self-domestication?

The self-domestication
hypothesis is,

I think,
one of the most exciting

hypotheses running out there
today.

It would mean there
was natural selection

against aggressiveness.

That over the last several
hundred thousand years,

our species has become
less violent and, conceivably,

that is still continuing today.

To test this hypothesis,

Robert Cieri gathered up
human skulls

from across 200,000 years.

Like the foxes, has the shape
of our skulls changed?

This particular specimen
is about 90,000 years old.

And I'm measuring

the width...

and the length of the face.

And then I'm also
going to measure

the projection
of the brow ridge.

These skull measurements

are tightly linked
to levels of a hormone

known to facilitate violence:

testosterone.

In general,
people with higher testosterone

have different face shapes

than people that have
lower testosterone.

To some, this harkens back
to 19th century pseudoscience.

Phrenology was
a pseudoscientific practice

where they would look at
the shape of someone's skull

and infer things
about their personality.

But this isn't phrenology.

The trends we're showing line up

with a lot of other forms of
evidence.

And it's more than
the shape of the face.

Testosterone's a very
complicated hormone.

But we do know that it seems
to be correlated

with levels of aggression
and violence.

It's not like, you know, you
give somebody more testosterone,

and they turn into
the Incredible Hulk

and start tearing things apart.

But men who have been exposed
to higher levels of testosterone

during prenatal development
or during pubertal development

are more likely to engage
in aggression

throughout the lifespan.

This link may partly explain
why it is men

who are responsible for most
of the world's violence.

90-something percent
of every kind of violence

you can think of
is due to males.

If we got... somehow got rid of
human males,

then the entire situation
would change.

In fact, the situation
may have already changed...

and the evidence might be
staring us in the face.

We found that the shape
of the skulls changed.

The upper face became shorter,
relative to its width.

And the brow ridge projection
went down over time.

So, we're showing
that testosterone levels

have gone down over the last

200,000 years.

The anatomical evidence
is very clear.

Males became
much less aggressive.

Violence was an important
social tool in human history.

You can get things done
by being violent.

But we're moving into a world
where that tool

is less and less effective,

and violence doesn't pay off
as much.

And the recent rise
of nonviolent movements

seems to bear this out.

Consider Mahatma Gandhi,

who showed the world the power
of nonviolent resistance.

The Salt March of 1930,

where he drew in hundreds
of thousands of Indians

by marching 200-plus miles
to the sea,

had a profound effect
on people's understanding

of what nonviolent action
could achieve.

And Erica Chenoweth's research
suggests Gandhi

was by no means alone.

The Salt March is now just one

of over 300 cases
of nonviolent resistance

that occurred since 1900.

The Philippines People Power
movement,

the Polish Solidarity movement,

the Serbian Anti-Milosevic
movement,

The Rose Revolution in Georgia,

the Orange Revolution
in Ukraine,

the Tunisian Jasmine Revolution.

But the most impressive thing
is not the sheer number,

it's their results.

Nonviolent action has been
wildly more effective.

In fact, the success rates
of nonviolent mass movements

are about twice as large
as the success rates

for violent campaigns.

And this increase in nonviolent
resistance has been paralleled

with an expansion
of human rights.

The adoption

of the Universal Declaration
of Human Rights in 1948,

though just words on paper,
set a new goal for the world.

The idea of universal
human rights is a huge change

in worldview.

It meant that you couldn't
enslave other people,

it meant that you couldn't
wage wars that devastated people

by the millions.

The rights revolution
that sputtered forward

in the 19th century
was finally gaining momentum.

This is the thing about rights:

the minute you declare their
existence,

you get people saying,
"Well, if that, why not this?"

You instantly have
this kind of pressure

for the recognition
of more rights,

which we still are living with
today.

And where there's reliable data,
this expansion in rights

often maps onto downturns
in many quantifiable measures

of physical violence:

genocide, homicide, rape,

assault, child abuse,

domestic violence,

even spanking.

They all point downward.

But before we pat ourselves
on the back,

it's worth considering
that these numbers

only tally physical violence.

Steven Pinker's focus
on deadly violence is telling us

part of the picture.

It's an important question
to ask,

but it's not comprehensive,
right, in the kinds of violence

that affect people's daily
lives.

Lethality isn't the only way
to measure violence.

Mass incarceration
is a form of violence.

There's a kind of
psychological violence, right,

the destruction
of other people's wills,

that is happening
on a mass scale

that doesn't get counted
in those statistics.

The definition of violence
has to be expanded.

What does it mean to live longer
if you're suffering horribly,

mentally, socially, cognitively?

And so, how we think about
ups and downs in violence

has to take this
broader perspective.

We're at the point in which

discussions of violence
are evolving.

And that is real progress

from when discussions
of violence were centered on

world wars,

genocides.

Nonetheless,
even if progress is being made,

a trend is not necessarily
a prediction.

With the enormous
military capacities

that states have today,

it takes just one war
to destroy the whole trend.

And just as German nationalism
spawned Hitler,

many see today's new wave of
nationalism as a looming threat.

In many countries,
we've seen maybe a little bit

of a backsliding towards
more authoritarianism.

Voters who are motivated
by nationalism,

may elect leaders
that could destroy it all.

And blindly following
those leaders,

wherever they may lead us,
is still a very real danger.

At SWPS University in Poland,

Tomasz Grzyb
and Dariusz Dolinski,

are revisiting a famous
experiment

first conducted in the 1960s

by the American psychologist
Stanley Milgram.

In the aftermath
of the Holocaust,

Milgram wanted to understand
how seemingly good people

could follow terrible orders.

Just as Milgram did,

the experiment starts
by setting up a fake study.

There are two participants
and there is a guy

who presents himself
as a professor of psychology

and he says that, "Well, you are
a participant in an experiment

which is devoted to find out
how memory is working."

Grzyb is masquerading
as a participant...

the so-called "learner."

The other participant

is the "teacher."

Grzyb pretends to memorize
sets of letters.

But his responses are scripted.

The teacher is told

that the student
is hooked up to the machine,

and they must administer a shock
if he answers incorrectly.

Grzyb is only acting...

he is not really wired
to the machine.

Because the experiment is highly
stressful for the real subject,

the so-called teacher,
it's controversial.

So it will be stopped
at 150 volts,

the tenth switch on the panel

which, if real, would be
an extremely painful shock.

Will anyone go so high?

With an authority figure
ordering them...

...most people go all the way
to the highest shock level.

We had about 220 participants

and about 90% of them

were able to go up
to the tenth switch.

Many people think
they wouldn't follow orders

to commit violence,

but the work
of Grzyb and Dolinski

suggests this capacity
is in most of us.

It's not a question
of our personality.

It's a question of situation.

There's a high probability
that each one of us

would behave in the same way.

Somehow by our
internal construction,

by our attitude to the world,

we are ready to do bad things
to other people.

Hate no longer hides
behind hoods.

Which lands us in the present.

It's clear that the story
of human violence is not simple.

Peace is not
a forgone conclusion.

...reminiscent of images
from a dark American past.

We can go backward again.

Just as we move very quickly
toward a peaceful world,

we can move very quickly
back toward a world

where most of us think
violence is the answer.

The president's
extraordinary tweet

raised the real possibility
the U.S. and Russia

could soon be shooting
at each other.

Peace is being treated
as something that

automatically comes to pass,

and we really can't take it
for granted.

In the U.S., violent clashes
broke out on Saturday

in the city of Portland, Oregon.

Our nasty impulses
haven't gone away.

To point out that things
were worse in the past

is not to say

that things are perfect
in the present.

We still don't know just how
many gunmen are out there

and when they will be found.

Quite the contrary,

it's precisely by understanding
how our predecessors

were able to drive down
rates of violence

that we can be emboldened to try
to drive them down even further.

And to do that
requires stepping back

and trying to understand
why the world feels so violent

in the first place.

We are in a super-saturated
24/7 information society.

When it bleeds it leads.

And there is a sense,
probably accelerated by

both conventional media
but also social media,

that things are spinning
out of control.

Reynolds streamed what happened
next live on Facebook.

He was reaching for his wallet.

And the officer just shot him
in his arm.

People are experiencing violence
happening

in other places
all over the world

right now in their own lives,

in a way they just couldn't
before.

That is a sea change
in our consciousness.

All this information
feeds a particular bias

long known to neuroscientists
and psychologists.

We call it
the availability heuristic.

We judge risk and danger

according to how quickly
examples pop into mind.

The van raced along at close to
50 miles an hour...

So if there's a terrorist attack
in the news,

we think that terrorism
is skyrocketing upward.

But if you look at

the actual risk
of being a victim

of a terrorist incident in, say,
Western Europe or North America,

it's less than being hit
by lightning.

North Korea's nuclear test...

A diet of news stories
will fool us into thinking

that violence is much more
prevalent than it really is.

I have that same reaction...

there has to be danger,

and to let your guard down
for a moment is to be a sap,

is to make yourself vulnerable.

And it's only my, you know,
scientific training

that allows me to say,

"You know what, crazy brain,
look at the data."

But aggregate data
can only tell you so much.

For example,
taking the U.S. as a whole,

homicide rates
have declined dramatically,

to about five deaths
per 100,000 people per year.

But when you drill down,
you find that some cities

have rates up to
ten times higher.

We tend to think
of this phenomena

as affecting all people equally.

But the reality when it comes
to, say, homicide or terrorism,

is that it's hyper concentrated

in time, space
among certain communities.

Why are some places
more violent than others?

What can the past tell us
about violence today?

History suggests
that some of the factors

driving violence down

are a strong government,
education,

and equality.

But those conditions are not
evenly distributed today.

Income inequality has a very
strong statistical relationship

with overall levels of homicide.

In fact, income inequality is
one of the strongest predictors

for violence.

Here in Baltimore, the situation
is particularly dire,

fueled in part
by a legacy of racism

and an extreme lack
of economic mobility.

I don't think that people
are getting up every morning

and saying, "Who am I going
to go shoot today?"

I think people are getting up
saying,

"How am I going to eat today?"

And if someone prevents them
from doing what they think

they have to do in order to feed
themselves and their families,

there's a ripe opportunity
for violence.

Baltimore City has seen
250 murders so far this year...

Once violence starts,
it spreads.

You can see the gun
in his left hand.

The gunman is still
on the loose here...

When you kill
this person's brother,

then they want to retaliate
and they want to make somebody

feel the pain that they felt,

so they become shooters
and killers.

It's like a...
it's like a demon.

It spreads from souls to souls.

Without the resources to fix
the underlying problems,

this neighborhood is turning
to an innovative intervention

to reduce violence.

With respect to violence,
we're stuck in the past.

Our thinking now is medieval.

We're blaming people,

not understanding
what's going on actually,

not applying approaches
that have been shown to work.

For epidemiologist Gary Slutkin,

those approaches
are based on data.

After returning
from over a decade

fighting infectious diseases
in Africa,

he recognized
a distinct pattern.

I'm looking at
a graph of violence,

it looks exactly like
the graph of cholera.

I'm looking at the map
of the clustering of violence,

it looks exactly like
the mapping of AIDS.

So I'm saying,
"Oh my God, you know,

this is exactly like
every infectious disease."

And just like a disease,
under certain conditions,

violent acts are contagious.

One case of violence
causes more cases of violence,

just as one case of flu
causes more cases of flu.

So could the same methods used
to fight infectious diseases

also stop shootings?

The shootings that we have had,

most of them,
these two are inside here...

That's an idea being tested
at Baltimore's Safe Streets,

one of a growing number
of programs

adopting Slutkin's approach.

There's just a lot of shootings
going on in the neighborhood,

so we was really trying
get to the bottom of that.

The starting point
in any epidemic

is to detect
where the next event might occur

and interrupt the exposure.

So what're we going to do
today for canvassing?

I mean it's been a lot of things
going on in the neighborhood

so I'm going
to just take a tour.

To do that, Slutkin created

a new type
of public health worker:

a "violence interrupter."

A violence interrupter
is basically a health worker

who can know what is going on

and find where an event
might be likely to happen,

and then prevent
its progression.

So you're cutting off
the epidemic spread itself.

The first step in fighting
any epidemic

is to identify
the initial outbreaks...

the so called "hot spots."

The red dots are
the firearm homicides

and the yellow dots
are the non-fatal shootings.

So if we map out

all of the violence in the area
then we can sort of see, like,

"Oh, there's was a cluster
up here on the right

where the staff should be
focusing on.

"Maybe down here on the left
there's another little area

that we tend to see
more violence happening."

And then we base our program
decisions on that data.

Once the hot spots
are pinpointed,

the violence interrupters
are deployed.

Lately, there's been
a lot of activity

in the community,
so we're just coming through,

try to make sure
everything's at peace.

This team works in Park Heights,

one of the most dangerous
neighborhoods in the city.

Most of the violence
is, is spontaneous.

So we just try to do our walks

so we can be there
to try to catch it.

What really makes the program
is the guys that's out here

doing the footwork,
doing the groundwork,

because it's our credibility

that really keep the peace.

We just try to get in
everybody's heads

and everybody's mind
and let them know

the shootings and homicides
are not normal.

It's not normal

for somebody to lay right there

with five and six bullet holes
in him,

and he's dying,
and... and that ain't normal

for kids to see.

It ain't normal
for a mother to lose her son

to senseless violence like that.

Steve Diggs,
better known as "Peppy,"

knows these streets.

I'm born and bred Park Heights.

I've been here my entire life.

If you drop me in the ocean,

in the middle of the night,

I'll start swimming
towards Park Heights.

And he knows all about
the violence.

I fell in love with the streets,

the whole lifestyle of it.

The girls, the money,
the respect that you get

in your neighborhood.

You know,
all the way down to the part

where I had to bust somebody
in their head.

Disrespecting me...

could get a person
beat nearly to death.

Has gotten people beat
nearly to death.

I had to sit in jail
for ten months

because I beat a guy
nearly to death.

I was that person for 30 years.

I had to let that person die and
create this person right here.

That's what qualifies
all of us to do this.

You walked the walk,

you talked the talk,

you're qualified to intervene.

She told me that she was going
to the police station

and fill out a report on you.

For what?
I didn't do anything to her.

Today, Peppy is following up
on a violent altercation.

I couldn't understand how
it got that far

in the first place.
Look at my face.

She beat me in my face,

kicked me in my back.

I felt a threat.

She's yelling, belligerent.

We're going to do it
one at a time, okay?

Because you went to me like this.
No! Uh-uh!

Yes, you did, and then that's
when I blacked out on you.

You was pummeling me!
All right.

Because you were trying
to grab stuff.

I don't know what you're doing.
I'm grabbing my phone!

See how you're doing?

Right now you're not
listening to each other.

You're not hearing
nothing she said

because you're so ready
to talk back.

Maybe it's something else,
you understand what I'm saying?

I don't have a problem.

I want to leave
because I feel out of place.

Even though I knew they wasn't
listening to each other,

I think it was very helpful

because they feel like
they're vindicated.

For them to be able
to do that on their own,

they wouldn't have been able
to do it

because it would have just
went on and on and on

until one of them threw a punch.

Women fight way differently
from men.

Guys, they run for their knife
or their gun, which is so sad.

Later, Peppy is dispatched

to diffuse a potentially
deadly dispute.

Unfortunately,

we live by the gun
around here, man.

The man Peppy is talking to
says that two nights ago

he ordered a revenge killing.

But his guys shot at
the wrong person

and now that person
wants to take revenge.

Let me see your hands, yo.

You ain't seeing my.
Let me see your hands, yo.

You didn't come 'round here
for no smoke.

You didn't come 'round here
for no smoke, right?

Let me see your hands, yo.

You didn't come 'round here
for no smoke, right?

Right?

Listen, there's no smoke.

Tell him what
you just told me, yo.

Let me see your hands, yo!

You keep your hands
out your pockets.

You're making me nervous, yo.

If it wasn't for
this dude here, man,

I'mma tell you something, man.

Would go a lot
different than this, right?

- And I know that.
- You know how I know this

ain't going to happen again?
Because I'm right here.

That's how you know it's not
going to happen again, right?

Man, you'd do
the same thing though!

You're right

I would do the same thing.

All right, okay,
now we've got common ground.

We've got common ground.

You would have.

Can we agree
that you apologize, yo?

Absolutely.

I'm gonna accept that, man.

But I'mma tell you this, man.

You don't come back
from that death.

There ain't no coming back
from that.

I say you go and shake his hand.

I say go shake his hand.

I mean, like...

Squash it, yo.

Man, I'mma just
leave this be, man.

Back to you, right.

That's a hell of a mistake
to make.

We are guys right directly
in these neighborhoods.

That can bring
these two guys together

in the midst of their anger,
their hatred,

and their want for revenge,

and bring about
a peaceful resolution.

That's a big part of what
Safe Streets do.

A lot of times guys want to put
an end to the conflict.

Especially when them guns
get to goin'.

The Safe Street guys give them
a way to get out of there.

"All right,
Safe Street's squashed it

"so now I'm not looking
like a punk.

Now I'm not looking like
I'm scared of nothin'."

But it's not just about that.

People out here
really need resources.

Not justifying nothing,
but a lot of people be surprised

what people be going through.

All right, okay,
so what's the next part?

What you gotta do?

What you gotta do to get
yourself right?

Stop all this other
from happening.

I wanna leave drugs.

Try to get a job.

That's it.

I swear straight up, I'm trying.

Because, you know what?

We gotta deal
with one thing at a time,

you know what I'm saying?

We gotta deal
with the big issue.

It ain't funny, yo.

A lot of violence come from
lack of.

That's a lack of education,
that's a lack of food,

that's a lack of basic
necessities like clothes, water.

When we interrupt the violence
and we take a look at

what the
precipitating factors are

that contributed
to the violence,

we see opportunity
to connect folk

to additional services
of support.

And those services could range
anywhere from mental health,

substance abuse, housing,
transportation...

Things that help people
get on their feet

so that they don't have to
rely on the streets

to feed themselves
and their families.

While Safe Streets
connects people

to a host of community services,

they're not designed to take on
the root causes of violence.

Their success is measured
in two key metrics:

shootings and killings.

While surrounding neighborhoods
continued to see

high levels of firearm homicide,

from 2017 to 2018,

the Park Heights post went 382
days without a single killing.

And people are starting
to take notice...

Over 50 sites around the world
have adopted the approach

practiced by Cure Violence.

And the data is clear.

It's working.

Because they come from
the public health field,

they set a very high bar
for evidence.

Cure Violence has been evaluated
for its work in Chicago,

in Baltimore, in New York,
in Honduras, in Mexico,

in New Orleans, in South Africa,

and repeatedly the findings
are that shootings and killings

go down by between 40% and 70%.

And it's sustained.

Behaviors that were formed years
ago can be completely changed.

That right there.

I am a case in point.

Violence can be unlearned.

Sometimes I hardly believe
that...

I found a job,

employment that I love.

That it's actually noticed

that people like me stop

so much more violence
from happening.

Focused programs
on crime reduction

have shown they can work.

Even if you haven't cured

blights like inequality
and poverty and racism,

you can prevent an awful lot
of people from getting killed.

Data can be a useful tool
in tackling violence,

but it is by no means enough.

Knowledge is power
only if you act on it.

Consider mass shootings.

Gun violence is still a big
challenge in the United States.

And yet, funding to do research
on this public health challenge

was taken away by the CDC
because of let's call it

disagreements in Congress.

But the research
that is available

points towards solutions.

It may seem impossible
to talk about

preventing and reducing gun
violence in America today,

but the fact is there are
examples of where

smart interventions
have generated declines

in gun violence.

Take the example of Australia.

Following a mass shooting in
April 1996 that took 35 lives,

reaction was swift.

The prime minister, John Howard,
tonight detailed sweeping plans

to reform Australia's
national gun laws.

Instead of having an agonizing
debate that went nowhere

about what to do about it,

what you had was action.

To achieve a total prohibition
on the ownership

of all automatic and
semiautomatic weapons.

Within months the parliament
in Australia had legislated

that there ought to be a massive
gun collection program

and new constraints and controls
and regulations

around certain types of weapons.

Assault weapons were banned

and over 650,000 were turned
into the government.

Gun-related homicides plummeted.

When Australia passed
a stringent gun-control measure,

rampage killings,
which had afflicted the country,

fell pretty much to zero.

In the 23 years after the ban,

Australia had
only two mass shootings

with a total of ten dead.

The message is that gun
regulations can reduce deaths.

And that would appear to be true
here in the U.S.

In the aftermath of the
Sandy Hook shootings,

Connecticut passed
some of the nation's most

restrictive gun laws.

Since then, the five-year
average of gun-related homicides

has dropped by a third.

And it's not just Connecticut.

States across the United States

that have had tighter,
more restrictive legislation,

especially around
carrying of firearms,

tend to show lower rates
of homicide,

lower rates
of intimate partner violence,

lower rates of suicide.

With the help of data, even
the most intractable problems

can become a little less
daunting.

There are some parts
of the world that people

tend to write off as just

hotbeds of war

and where there's nothing
you can do about it.

Take the recent genocides
in Rwanda, Sudan, and Myanmar.

Though in each case the root
causes of violence are complex,

one thing they share
is long-standing

ethnic and religious tensions.

Among the most challenging,
the Middle East,

where the wars in Syria and Iraq
have displaced millions

and brought chilling stories
to the evening news.

The Syrian regime just attacked
its own people

with chemical weapons again.

A war crime.

It is easy to be pessimistic
about the Middle East.

The conflict is very raw.

The distrust is very
deeply ingrained.

So if we can find even
small effects in this setting,

it suggests that elsewhere
we might find bigger effects.

Can science do anything
to reduce

those underlying tensions?

Mass, in a church in the village
of Qaraqosh

in the Nineveh Plains
of northern Iraq.

There are an estimated
400,000 Christians in Iraq.

About 50,000 of them once lived

in this predominantly Christian
enclave.

The community, and the church,

bear the scars
of a bloody uprising.

In 2014, ISIS militants swept
through the Nineveh Plains.

Rami Hana is one of thousands
that fled Qaraqosh

as ISIS approached.

Rami's mother thought they would
only be gone for a few days.

In fact, it was two years
before the city was liberated.

Rami's family returned
to find their home looted

and damaged beyond recognition.

They were one of
the lucky families.

About a third of the homes
had been set on fire.

And occupying jihadists
had tried to erase

any evidence of Christianity
from Qaraqosh...

burning churches,

destroying statues,

toppling towers.

What ISIS did
to the religious minorities

in the Nineveh Plains region

is classified now as a genocide
or as ethnic cleansing

by the State Department,
by the U.N.

These were communities
targeted specifically because

of their religious or ethnic
background.

There were kidnappings,
killings, sex slaves.

The armed forces just fled.

So it really was
a horrific experience.

Little by little, more residents
have been returning to Qaraqosh.

Among them, Mohammed Hussein.

Today he prays at his mosque,

thankful for the omnipresent
security forces.

Nonetheless, religious tensions
still remain high.

In the wake of a conflict
like this,

the social trust just becomes
obliterated.

So you have neighbors

that become suspicious
of other neighbors,

people are perceived as being
collaborators on the basis of

what community they belong to.

ISIS may be gone,

but two powerful ingredients
for violence...

prejudice and sectarian
hostility... remain.

Ethnic cleansing doesn't just
happen overnight.

The first step of that is like

some level of prejudice
toward another group.

It turns into dehumanization
of the other group.

And that just escalates,
where you come to a point

where people actually feel
justified inflicting harm

on a group.

Looking at what happened
in Qaraqosh,

it is difficult to imagine
what could heal these wounds.

One solution may lie
in a rather unexpected place...

Soccer is something people do
just for fun.

We just add some tweaks
in terms of how to mix up

the team composition to test
the idea of contact.

Political scientist Salma Mousa
traveled to Iraq

to test an idea...

could something as simple
as playing a game

reduce prejudice
and increase empathy?

It's kick off in the
Nineveh Plain Soccer League.

Rami, a Christian,
captains his team.

Trying to stop him scoring
in the opposition's goal

is Mohammed, a Muslim.

They come from different worlds
and neither has any idea

that they are taking part
in an experiment,

testing "contact theory."

The contact hypothesis
is the idea that when we have

a lack of empathy for others
who are different from us,

or feel prejudice against them,

it's really because
we don't know them very well.

And if we were to merely
come into contact

with those outsiders,
it would stop feeling as much

like an us and them situation.

The theory suggests

that contact would only work
to increase empathy

under certain conditions:

when the groups are on
equal footing,

sharing a common goal.

The idea behind contact theory

is that contact can reduce
prejudice.

This idea has been around
for a long time,

but what is new is we now have
the scientific methods

and the rigor to try to test
some of these things.

Mousa created
a new soccer league,

and invited teams
around Qaraqosh to join.

Rabie Zakaria
is the league's organizer.

He signed up 37 teams,
with 444 players.

The teams in this area
tend to be homogenous.

So there are Christian teams,
there are Muslim teams,

there are Kurdish teams.

Once they signed up
for the league, we said,

"Well, social inclusion
is part of our mandate,

"and so we need to mix up
some of the teams,

so all the teams are going
to get some added players."

On Rami's team, he plays
alongside three Muslim players.

And Mohammed is one of
three Muslims on his team.

Mousa kept some of the teams
all Christian as a control.

Would being on a mixed team

do anything to change attitudes?

When we asked other people
to join them... players...

it was kind of difficult
at the beginning

because some of the players
felt not welcome in the team.

But we asked them to train,
and it got better.

Gradually, the players started
working together on the field.

But off the field,
Mousa needed a way to test

if her experiment
was making a difference.

To do that, first she had
Rabie arrange a social event.

Would players from both
communities turn up?

The real moment where I thought

there might be something to this

was when I saw that the players
who were on mixed teams

were double as likely

as those on the control teams to
show up for this social event.

But that was an event
arranged by the study.

What about on their own?

To find out, Mousa had Rabie

give the players vouchers
to unfamiliar restaurants.

Normally, people in this region
don't go to restaurants

owned by members
of another faith.

Periodically,

Rabie collects the vouchers
from the restaurants.

So we have,
almost more than 200.

Each voucher is tagged
with a specific I.D. number,

and the restaurant owners
help track if people came alone

or with others.

The results showed
a marked shift in behavior.

Being on a mixed team
makes you more likely to

go to a social event

where people from
the other group are present.

It makes you more likely to go
to different neighborhoods

or different cities even
that are...

that are dominated
by another group.

And though the changes
were modest,

her surveys showed
a shift in belief

that coexistence is possible.

Playing on a team
with diverse teammates

makes you more likely to say

that it's important
to treat each other

as Iraqis first as opposed
to other community identities.

But tensions are high
once again in Qaraqosh...

the final in the Nineveh League
has ended in a draw

and the tie must be decided
on penalty kicks.

Rami steps up to the spot...

and scores.

I was watching on Facebook Live

when we had our
end of league celebration

and we were handing out
the trophies,

and I saw Rami get his

like massive trophy,

and he gave a little speech.

Part of his speech was,

"There are really like no
boundaries when we play soccer,

"and it doesn't matter where
you're from or who you are,

we're here
to do the same thing."

I'd like to think
that soccer can save the world.

I know it's not that simple.

But if we find even some small
effects on people's behaviors,

considering that we're dealing
in a very difficult environment,

I think that's very promising.

And I hope that we can use
some of these insights

to prevent violence on the basis
of someone's identity.

Though small steps like these

may give people hope,

it's important to keep
such results in perspective.

I don't think there's
anything wrong in recognizing

that there's progress.

We just want to be sure

that patting ourselves on the
back for that doesn't obscure

what else still needs
to be done.

Human beings, we are so complex.

But our understanding
of ourselves,

as a species,
that understanding evolves.

Even if we're a long way
from a world free of violence,

it's still possible
to be inspired

by how far our species has come.

As you become aware of the
historical decline of violence,

the world starts to look
different.

You start to appreciate things
that we can take for granted.

How major conflicts in the news

have not escalated to world war.

How new monuments are named

for martyrs and civil rights
leaders, not war heroes.

How the quest for human rights

is crossing
international borders.

Our past has led us
down this path.

The question is:
will we stay on it?

We're in a unique moment today
in which we have a chance

to sort of lock in some of this
progress that humanity has made.

We should never take for granted

that when we're enjoying
a period of peace

it's because it's inevitable.

We have to continually work
for peace.

Until recently,
we lived in a world in which

slavery, and rape, and warfare

were the norm,
not the exception.

What's changed over history is
the better angels of our nature

predominate over
our inner demons.

We can see shootings go down.

We've done something right.

Let's figure out what it is
and make sure we keep doing it.

Humans are a hot mess,

and we have so much more to do.

One of the benefits
of Pinker's work

is to remind ourselves
of all that needs to be done.

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