The Violence Paradox

PBS Airdate: November 20, 2019

NARRATOR: It is an epic story, spanning all of human history,…

MARTA MIRAZÓN LAHR (University of Cambridge): This man was shot at a distance, twice, with arrows.

LYNN HUNT (University of California, Los Angeles): Torture was legal. It was administered in front of a judge.

NARRATOR: …an age-old battle between our inner angels…

KAREN WYNN (Yale University): We can see how the human mind is fundamentally built.

NARRATOR: …and our demons,…

CAROLYN ROBERTS (Yale University): We’re at war with ourselves.

NARRATOR: …but one with a surprising twist.

JOSHUA W. BUCKHOLTZ (Harvard University): Contrary to what we might think from the news every day, rates of violence are actually declining over time.

STEVEN PINKER (Harvard University): The decline of violence might be the most significant development in human history.

NARRATOR: Has violence really declined?

IAN MORRIS (Stanford University): A lot of people just don’t believe this.

PHILIP DWYER (University of Newcastle): It is extraordinarily controversial.

TIFFINY TUNG (Vanderbilt University): It’s an interesting hypothesis to test.

NARRATOR: The stakes couldn’t be higher.

MOHAMED SALIOU CAMARA (Howard University): This is about our very existence.

NARRATOR: Now science is tackling violence.

VINCENT BROWN (Harvard University): We’re saying, like, “Here are things that we could do.”

NARRATOR: From the streets of Baltimore...

RASHAD SINGLETARY (Safe Streets, Balitmore): We can see shootings go down.

NARRATOR: …to war-torn regions of Iraq,...

SALMA MOUSA (Stanford University): We’re not just testing things in a lab environment, but we’re really testing these in the field.

STEVEN PINKER: We’ve done something right. Let’s figure out what it is and keep doing it.

NARRATOR: …are we on the path to a more peaceful world?

STEIN TØNNESSON (Peace Research Institute Oslo): It takes just one war to destroy the whole trend.

NARRATOR: The Violence Paradox, right now, on NOVA.

ABC NEWS CLIP, BOSTON MARATHON BOMBING: We’re going to need more ambulances here.

NIGHTLINE PARKLAND CLIP #1: The shooting started...

NIGHTLINE PARKLAND CLIP #2: Shots fired. More shots fired.

CNN NEWSCLIP: This was the horrific picture just moments after a white van...

FOX NEWS WSVN: Multiple fatalities is what we’re hearing from officials at this moment.

NBC NEWS: Kim Jong Un has detonated what is widely believed to have been a hydrogen bomb.

CHRISTINA MINICUCCI: The world has devolved into a place where nobody can feel safe.

GERALDO PAGAN: War is everywhere. It’s every corner of the world.

FOX CHEMICAL ATTACK IN SYRIA: At least 40 people were killed, hundreds wounded...

JOSEPH SOLOMON: Every day, when you’re on the news, there’s more and more violence.

CBSN CHARLOTTESVILLE, VIRGINIA, NEWS CLIP: There has been teargas, there has been pepper spray.

LINDA HARVEY: I’m afraid for my children and the world that they’ll grow up in.

ABC 2 IN FOCUS BALTIMORE, NEWS CLIP: They let loose a hail of bullets.

LINDA HARVEY: It keeps getting worse.

ABC NEWS, NEWTOWN: And this time, gunfire aimed at elementary school children.

ABC NIGHTLINE: This is the 22nd school shooting this year, where someone was killed or injured.

VICTOR RIVERA, JR.: There’s gun violence, police brutality, people coming and attacking our country.

ABCNEWS MARATHON: The first of the two explosions...

GLORIMAR DE LOS SANTOS: That could happen to my city. That could happen to me.

MARQUIS VICTOR: The world is through and through a violent place. That’s just a part of existence.

NARRATOR: Is this who we are, a species doomed to kill and be killed, a never-ending cycle of violence?

STEVEN PINKER: The reality is that we may be living in one of the most peaceful eras in human existence.

NARRATOR: Peaceful? Could this possibly be true?

STEVEN PINKER: 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.”

NARRATOR: 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.

STEVEN PINKER: 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.

NARRATOR: Intrigued, he looked further.

STEVEN PINKER: 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.

NARRATOR: A story that spans the entirety of human history, drawing on disciplines from archeology to neuroscience, and has the potential to turn conventional wisdom on its head.

RICHARD WRANGHAM (Harvard University): 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.

IAN MORRIS: The greatest thing that’s happened to humanity is that we’ve lowered our rates of violent death by 90 percent. This is the big story.

NARRATOR: But could it be too good to be true?

RUBEN MENDOZA (California State University, Monterey Bay): 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.

CAROLYN ROBERTS: 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.

PHILIP DWYER: It depends on who you are and where you live.

NEWS CLIP: North Korea’s nuclear test…

Among the 27…

JOSHUA BUCKHOLTZ: 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.”

MOHAMED SALIOU CAMARA: 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.

NARRATOR: It’s a controversial argument, but if physical violence really has declined, it presents us with a huge opportunity.

STEVEN PINKER: 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.

NARRATOR: 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.

MARTA MIRAZÓN LAHR: Nataruk is a bleak part of the landscape. There’s no vegetation, and it’s got a dark gravel covering the surface.

NARRATOR: Marta Mirazón Lahr started excavating this site seven years ago.

MARTA MIRAZÓN LAHR: 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 shinbones 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.

NARRATOR: A crime that took place 10,000 years ago, when this desert looked very different.

MARTA MIRAZÓN LAHR: Ten-thousand 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.

NARRATOR: A conflict recounted in bones, now buried in a remote storeroom in Northern Kenya.

MARTA MIRAZÓN LAHR: 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.

NARRATOR: And he wasn’t alone; many of the skeletons bore signs of violence.

MARTA MIRAZÓN LAHR: There are injuries to the head that suggest there’s a cut in the face or 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.

NARRATOR: Something terrible clearly happened here, but what?

MARTA MIRAZÓN LAHR: 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.

NARRATOR: The bones of Nataruk are the oldest known evidence of a planned raid, a form of early warfare.

MARTA MIRAZÓN LAHR: And I think that as a behavior, as a characteristic of human societies, it probably goes back in time much, much deeper.

NARRATOR: The question is how deep?

CARLOS D. BUSTAMANTE (Stanford University): The archeological record on every continent shows massive evidence of human-to-human destruction. There’s just no other way of putting it, right? The Paleolithic record is a horror show.

NARRATOR: From Otzi, the 5,000-year-old Iceman found with an arrow in his back,…

CARLOS D. BUSTAMANTE: It looks like a hit job.

NARRATOR: …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.

CARLOS BUSTAMANTE: Head bashed in, indubitably. There’s even evidence of cannibalism on almost every continent. You see violence time and time again, in archeological site after archeological site.

NARRATOR: Of course, a handful of cases may not be a fair sample of the distant past. How violent were we?

STEVEN PINKER: You can’t answer that question by particular incidents, because there’s violence in, in all societies. You really do have to count.

NARRATOR: 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 arrowhead there. They found that the proportion of prehistoric people who suffered a violent death was up to three times greater than today.

STEVEN PINKER: I was stunned at the high rates of violence. There’s nothing close in any modern society.

NARRATOR: What has changed? And more importantly, why?

To figure that out, you first need to understand some pretty basic things about us.

STEVEN PINKER: People often ask, “Are humans violent by nature or peaceful by nature?” The reality is we’re both.

NARRATOR: Pinker views our history as an epic struggle between our inner demons, that push us toward violence, and our angels that pull us away.

STEVEN PINKER: The brain is a complex place. It houses many circuits, some of which incline us towards violence and some of which inhibit us from violence.

DAVID J. ANDERSON (California Institute of Technology): That tension between acting on an aggressive impulse and restraining ourself is fundamental in our brains, because we are clearly aggressive animals.

NARRATOR: From body-slamming seals to fighting fruit flies, violence, usually committed by males, is something we share with most animals on the planet.

DAVID ANDERSON: Aggression is one of the most common social behaviors across the animal kingdom. Almost every sexually reproducing species shows aggression, including us.

NARRATOR: What in our brains drives aggression? That’s what scientists at Caltech 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.

DAVID ANDERSON: There are groups of neurons that, if you activate these neurons in a mouse, you can trigger aggression.

NARRATOR: 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.

TOMOMI KARIGO (California Institute of Technology): 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.

DAVID ANDERSON: There’s some component of, like, a volume control knob here, where, as we stimulate them more intensely, we get more intense aggression.

NARRATOR: Look what happens when you turn the power down.

TOMOMI KARIGO: Now, light is off and the animal retreat to the corner of the cage.

DAVID ANDERSON: 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.

NARRATOR: This experiment in mouse mind control has allowed them to pinpoint aggression in the brain.

DAVID ANDERSON: 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.

NARRATOR: The same may be true with us. Turns out, whether it is mice or humans, we share some of the same basic wiring.

DAVID ANDERSON: 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.

NARRATOR: So, the wiring for aggression runs deep. But that’s only half the story.

STEVEN PINKER: 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.

KAREN WYNN: So, I think we’re ready for Ethan. Would you like to bring him into our testing room?

NARRATOR: 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.

KAREN WYNN: 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?

ASSISTANT: Up goes the curtain!

NARRATOR: To figure that out, she puts on a two-act puppet show for babies.

KAREN WYNN: 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.

NARRATOR: In Act Two, this nice puppy takes center stage.

KAREN WYNN: 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.

ASSISTANT: Hi.

NARRATOR: Next the babies are given a choice.

ASSISTANT: Which one do you like?

NARRATOR: Do they prefer the kitty who was nice to the nice puppy, or mean to the nice puppy?

KAREN WYNN: If you give them the choice, babies very robustly choose the nice one.

ASSISTANT: Awesome job.

KAREN WYNN: 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.”

ASSISTANT: Do you want to just show dad where to sit?

NARRATOR: 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.

ASSISTANT: Up goes the curtain!

KAREN WYNN: This time, this mean puppy comes along and slams the box lid shut. He’s not nice at all.

NARRATOR: 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.

ASSISTANT #2: Do you see these?

NARRATOR: Will the babies still prefer the nice kitty?

ASSISTANT #2: Do you see this one? Which one do you like?

NARRATOR: No. Now they consistently pick the mean one.

ASSISTANT #3: Which one do you like?

NARRATOR: Turns out that even at this age, babies have the capacity to make simple moral judgments.

ASSISTANT #4: Okay. Oh, good job.

KAREN WYNN: 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 return.” So, that tells us that well before their first birthday, babies are already developing notions of just deserts. That is morality.

NARRATOR: So, both angels and demons are baked into our biology.

AZAR GAT (Tel Aviv University): 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.

NARRATOR: If violence has declined since prehistoric times, what did our ancestors do that tipped the balance toward our better angels?

STEVEN PINKER: One of the first violence reduction techniques was the state. Government can tamp down the cycles of violence.

MOHAMED SALIOU CAMARA: 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.

NARRATOR: Until about 5,000 years ago, humans lived in small nomadic bands. But as agriculture took hold, populations grew, and the first governments emerged.

IAN MORRIS: As societies get bigger and bigger, more and more problems have to be solved and the almost inevitable result of this is people start to form governments.

NARRATOR: 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.

STEVEN PINKER: 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.

RICHARD WRANGHAM: Much of the decline of violence is due to the existence of the state. Without government, the potential for chaos is huge.

NARRATOR: 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.

STEVEN PINKER: 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.

NARRATOR: Even so, for those living under the world’s first governments, life was still pretty brutal.

STEVEN PINKER: 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.

IAN MORRIS: 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.

NARRATOR: 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.

STEVEN PINKER: 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 the jawbone of an ass. And then the Israelites are commanded by God to commit total genocide.

NARRATOR: It would appear that our ancestors were obsessed with violence.

NARRATOR: And judging from our taste in entertainment today,...

ANGELINA JOLIE (As Voice of Tigress, Kung Fu Panda): Our battle will be legendary!

NARRATOR: …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.

DAVID CHESTER (University of Kentucky): We’re going to have you do the competitive reaction time task, okay?

M.R.I. TEST SUBJECT: Yeah.

DAVID CHESTER: Here we go.

NARRATOR: 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.

DAVID CHESTER: Remember that one and two are pretty quiet, and three and four get pretty loud.

M.R.I. TEST SUBJECT: Okay.

NARRATOR: The subject thinks they are playing against a real opponent, but actually, it’s a computer, and it’s not going to play nice.

DAVID CHESTER: She just saw that her opponent picked a four, so now she’s been thoroughly provoked.

NARRATOR: The volunteer seeks revenge.

DAVID CHESTER: She just picked a four. Seems as though she’s a little upset.

NARRATOR: 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.”

STEVEN PINKER: 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.

NARRATOR: 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.

FABIAN DRIXLER (Yale University): 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.

STEVEN PINKER: The decline of violence is by no means a Western phenomenon, although, until recently, a lot of the studies focused on the West, because that’s where the data were.

NARRATOR: And some of the strongest data was assembled by Manuel Eisner, a historical criminologist with a singular obsession: murder.

MANUEL EISNER (University of Cambridge): Over the years, I’ve developed a little bit of a obsessive interest in trying to find all the publications in different languages that have been written on homicide.

(Reading)“Robert of Chinehem hit Emmis, daughter of Alice de Crotchall, on the head with a stick so that she died. And he fled…”

“Evildoers came to Thomas of Englefield’s house and killed him.”

“He shouts, ‘Are you not ashamed of what you’ve done this morning to my wife?’ And then he kills him.

NARRATOR: It all started when he read an article that claimed that since the Middle Ages, homicide rates in England declined 40-fold.

MANUEL EISNER: I thought: “This can’t be true.” And so, I started looking at more evidence, more data.

NARRATOR: Trouble was, the data didn’t exist in any one place.

STEVEN PINKER: 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.

MANUEL EISNER: I would be looking at court records, prison documents, account books, confessions or pardon books.

NARRATOR: 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.

MANUEL EISNER: 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.

STEVEN PINKER: 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.

NARRATOR: 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.

STEVEN PINKER: 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.

NARRATOR: One answer might be what some social theorists call the “civilizing process.”

MANUEL EISNER: The civilizing process is the idea that as societies become more interdependent, we are penalized for behaving in a violent way against another person.

NARRATOR: 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.

ANDREW REITER (Mount Holyoke College): If businesses want to trade, they want to make money, and people profit off that, they live better lives and the economy’s going well, there’s an incentive for states to prevent violence from happening.

NARRATOR: The theory is this new economic order went hand in hand with a new set of social norms.

MANUEL EISNER: 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.

NARRATOR: According to some researchers, self-control was something that was sorely lacking when one considers daily life.

STEVEN PINKER: The medievals were, in a word, gross. They would copulate 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.

MARY FLANNERY (University of Oxford): 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.

NARRATOR: And judging from these passages from popular etiquette books, things must have been pretty different.

JUDITH MARTIN (Columnist, Miss Manners): (Reading) “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.

NARRATOR: But how in the world could something as mundane as manners contribute to a decline in violence?

STEVEN PINKER: 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 10.

NARRATOR: As it turns out, the connection between self-control and violence is long known to neuroscientists.

ADRIAN RAINE (University of Pennsylvania): We’ve known for a long, long time that violent offenders have poorer levels of self-control than people who are nonviolent.

NARRATOR: And that has to do with the prefrontal cortex, the area of the brain thought to be involved in planning and controlling our impulses.

ADRIAN RAINE: We’ve brain-scanned 41 murderers. And we showed that the prefrontal cortex is functioning more poorly in these murderers.

NARRATOR: 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?

ASSISTANT: In today’s session, you will be completing a series of survey questions, as well as…

NARRATOR: That’s what Raine’s team is trying to find out, here at the University of Pennsylvania.

ASSISTANT: During the stimulation itself you will be completing two cognitive tasks on the computer.

ADRIAN RAINE: They get electrodes put on the prefrontal cortex. And they’ll get 20 minutes of stimulation.

ASSISTANT: You may feel tingling, itching, a kind of prickling sensation.

NARRATOR: That tingling is stimulating or “upregulating” a specific part of the brain.

ADRIAN RAINE: 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 percent.

NARRATOR: Is it possible, then, that acquiring habits of self-control, like manners, could have had the same effect?

ADRIAN RAINE: By giving somebody training in exercising self-control, that activity may flex the prefrontal cortex and enhance that part of the brain.

ROY HAMILTON (University of Pennsylvania): 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.

NARRATOR: 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.

TIFFINY TUNG: 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.

PHILIP DWYER: The colonial project is one in which indigenous peoples are either physically and violently repressed or, in some instances, eliminated entirely.

CAROLYN ROBERTS: 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-warzones, where you have mortality levels that are between 10 and 25 percent on every voyage. And it lasts for nearly 400 years.

NARRATOR: 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.

STEVEN PINKER: There are a number of practices that were routine through human history, that we universally recognize today are barbaric.

NARRATOR: 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.

STEVEN PINKER: You had gruesome punishments, sadistic forms of capital punishment like breaking on the wheel.

LYNN HUNT: 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.

NARRATOR: Back then, torture wasn’t some random act performed by a sadistic psychopath, but a routine part of the law.

LYNN HUNT: It’s hard for us to imagine this, but torture was legal. It was administered in front of a judge, usually.

NARRATOR: But by the mid-1700s, this gruesome jurisprudence was quickly losing favor in Western Europe.

LYNN HUNT: 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.

NARRATOR: To Lynn Hunt, a historian at U.C.L.A., the answer has to do with a notion often taken for granted today.

LYNN HUNT: 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?

NARRATOR: 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.

LYNN HUNT: Literacy and the expansion of print had a very, very, very big impact.

IAN MORRIS: 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.”

NARRATOR: It wasn’t just that people could read, it was what they could read about.

LYNN HUNT: Newspapers got people to recognize that there was somebody else in another city who is having the same experiences as they are.

NARRATOR: It is difficult for us, living in a hyper-connected world, to appreciate how big an impact this could have.

LYNN HUNT: Print newspapers are incredibly important in creating this broader sense of community.

NARRATOR: And it wasn’t just newspapers, the newly literate masses developed a huge appetite for the novel.

LYNN HUNT: 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.

CAROLYN ROBERTS: 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.

NARRATOR: Action such as the abolitionist movement, which was bolstered by slave narratives and popularized by a single novel.

CAROLYN ROBERTS: A book like Uncle Tom’s Cabinis bringing people into a world that amplifies the humanity of the enslaved and, by extension, that they are deserving of freedom.

NARRATOR: The theory is that reading novels made people more empathetic. But can fiction really do all that?

JAMIL ZAKI (Stanford University): 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.”

NARRATOR: 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.

JAMIL ZAKI: 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.

NARRATOR: And things didn’t stop with the novel. A parallel revolution in science would seed even more radical questions.

IAN MORRIS: The scientific revolution drives people to ask these underlying questions about, “Why do things in the way that we do?”

CAROLYN ROBERTS: There was a new sense of rationality, where we want to understand knowledge, based on what we see and what we can actually document.

NARRATOR: Observation, hypothesis, experiment, the modern scientific method didn’t just explain the stars.

IAN MORRIS: 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.

STEVEN PINKER: 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.

LYNN HUNT: 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.

NARRATOR: Equality, even though it was narrowly defined to start with, 18th century European thinkers stoked the embers on a revolutionary ideal.

MOHAMED SALIOU CAMARA: 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 it. The cat is out of the bag.

NARRATOR: Still, some ideas resulting from the scientific revolution were far from perfect.

PHILIP DWYER: And it’s the same period in which pseudo-scientific racism, as we come to know it in the second-half of the 19th century, really begins.

NARRATOR: Perhaps reason and empathy helped fuel abolitionist movements, but at the same time, science was co-opted to justify racism.

CAROLYN ROBERTS: 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.

NARRATOR: And that balance of good and bad, according to Pinker, was shifting in favor of our angels.

STEVEN PINKER: 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.

NARRATOR: 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.

TIM HITCHCOCK (University of Sussex): The Old Bailey proceedings are, in my estimation, the most detailed account of everyday life ever produced in print.

NARRATOR: Tim Hitchcock spent 15 years digitizing 239 years of court proceedings.

TIM HITCHCOCK: 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.

NARRATOR: But this giant anthology presents a giant problem.

TIM HITCHCOCK: At 197,000 trials, nobody’s ever read all of them.

SIMON DEDEO (Carnegie Mellon University): It’s huge, right? It’s, it’s unreadable.

NARRATOR: 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.

SIMON DEDEO: 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 centuries, then I have to do a very different kind of science.

NARRATOR: And to do that he would need a really big data set. Hitchcock’s 127-million words would do just the trick.

SIMON DEDEO: Somebody whispers in our ear, “Hey, there’s this stuff sitting out there in Britain.” That, for us, is a goldmine.

TIM HITCHCOCK: 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.

NARRATOR: But how?

SIMON DEDEO: 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.

NARRATOR: Here’s where Tim had an idea: How about we use Roget’s Thesaurus?

TIM HITCHCOCK: Roget, in the 19th century, sat down, went through the dictionary and assigned every word to a particular meaning.

SIMON DEDEO: 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.

TIM HITCHCOCK: 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.

NARRATOR: For example, in the earliest accounts, the number of violent words often had nothing to do with the crime charged.

TIM HITCHCOCK: (Reading) “1770. John Jones and Isaac Ely of St. Sepulchres were indicted for assaulting James Low 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.

NARRATOR: But in later cases, that changes. Violent words strongly correlate with being on trial for a violent crime.

TIM HITCHCOCK: In 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.

NARRATOR: The records of the Old Bailey are hard evidence of a cultural shift away from interpersonal violence.

TIM HITCHCOCK: 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.

NARRATOR: A decline in homicides, 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?

AGUSTÍN FUENTES (University of Notre Dame): 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.

STEVEN PINKER: 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.

NARRATOR: 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?

STEVEN PINKER: 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.

NARRATOR: 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.

STEVEN PINKER: When you plot how many people get killed as a proportion of the world’s population, you can appreciate some of these trends.

NARRATOR: 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 10 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.

JOSHUA S. GOLDSTEIN (American University): The big national armies are not fighting each other, that’s not some data construction, that’s a fact.

NARRATOR: 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.

JOSHUA GOLDSTEIN: 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.

ERICA CHENOWETH (Harvard University): There are not too many periods in world history where we’ve observed such a steep decline in violence.

NARRATOR: So, how did we get from here to here? Is it possible that something inside us has changed?

ROBERT CIERI (University of Utah): We know that violence has been decreasing in human history, and we have a lot of explanations as to 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.

NARRATOR: 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.

ROBERT CIERI: 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.

ABIGAIL MARSH (Georgetown University): 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.

NARRATOR: The foxes’ behavior changed, and so did their physical appearance.

ROBERT CIERI: The skulls became shorter, and also, proportionately wider.

NARRATOR: 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?”

ABIGAIL MARSH: The self-domestication hypothesis is, I think, one of the most exciting hypotheses running out there, today.

RICHARD WRANGHAM: It would mean that there was natural selection against aggressiveness, and that, over the last several hundred-thousand years, our species has become less violent. And, conceivably, that is still continuing today.

NARRATOR: 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?

ROBERT CIERI: 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.

NARRATOR: These skull measurements are tightly linked to levels of a hormone known to facilitate violence, testosterone.

ROBERT CIERI: In general, people with higher testosterone have different face shapes than people that have lower testosterone.

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

ROBERT CIERI: 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.

NARRATOR: And it’s more than the shape of the face.

ROBERT CIERI: Testosterone’s a very complicated hormone, but we do know that it seems to be correlated with levels of aggression and violence.

ABIGAIL MARSH: 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.

NARRATOR: This link may partly explain why it is men who are responsible for most of the world’s violence.

RICHARD WRANGHAM: Ninety-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.

NARRATOR: In fact, the situation may have already changed, and the evidence might be staring us in the face.

ROBERT CIERI: 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. We’re showing that testosterone levels have gone down over the last 200,000 years.

RICHARD WRANGHAM: The anatomical evidence is very clear. Our males became much less aggressive.

ROBERT CIERI: 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.

NARRATOR: And the recent rise of nonviolent movements seems to bear this out.

Consider Mahatma Gandhi, who showed the world the power of nonviolent resistance.

ERICA CHENOWETH: 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.

NARRATOR: 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.

ERICA CHENOWETH: The Philippines People Power movement, the Polish Solidarity movement, the Serbian Anti- Milošević movement, The Rose Revolution in Georgia, the Orange Revolution in the Ukraine, the Tunisian Jasmine Revolution,…

NARRATOR: But the most impressive thing is not the sheer number, it’s their results.

ERICA CHENOWETH: 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.

NARRATOR: 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.

STEVEN PINKER: The idea of universal human rights is a huge change in worldview. It meant that you couldn’t enslave other people, meant you couldn’t wage wars that devastated people by the millions.

NARRATOR: The rights revolution that sputtered forward in the 19th century was finally gaining momentum.

LYNN HUNT: 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.

NARRATOR: 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.

TIFFINY TUNG: 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.

VINCENT BROWN: 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.

AGUSTÍN FUENTES: 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.

STEVEN PINKER: 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 and genocides.

NARRATOR: Nonetheless, even if progress is being made, a trend is not necessarily a prediction.

STEIN TØNNESSON: With the enormous military capacities that states have today, it takes just one war to destroy the whole trend.

NARRATOR: And just as German nationalism spawned Hitler, many see today’s new wave of nationalism as a looming threat.

ANDREW REITER: In many countries, we’ve seen maybe a little bit of a backsliding towards more authoritarianism.

STEIN TØNNESSON: Voters who are motivated by nationalism may elect leaders that could destroy it all.

NARRATOR: 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 Doliński 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.

TOMASZ GRZYB (SWPS University): 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’s working.”

DARIUSZ DOLIŃSKI (SWPS University): (Translated) What we have here are pairs of letters.

NARRATOR: Grzyb is masquerading as a participant, the so-called “learner.”

DARIUSZ DOLIŃSKI: (Translated) Your job is to memorize these associations. If you hear “D-A,” you would answer “D-E.”

If you make a mistake, you will be punished.

NARRATOR: The other participant is the “teacher.”

DARIUSZ DOLIŃSKI: (Translated) I will ask you, in your role as teacher, to sit down, and I will return in a minute.

NARRATOR: Grzyb pretends to memorize sets of letters, but his responses are scripted.

DARIUSZ DOLIŃSKI: (Translated) Your role is the teacher in this experiment. If you read “B-A,” then you should expect the answer “B-O.”

But if this gentleman makes a mistake, then you, we use this device. It is an electrical generator that allows us to easily send penalties.

These first buttons emit a very weak shock, then medium strong ones, very strong ones. These ones are extremely intense.

NARRATOR: The teacher is told that the student is hooked up to the machine, and they must administer a shock, if he answers incorrectly.

TEACHER #1: (Translated) And the gentleman is behind that wall?

DARIUSZ DOLIŃSKI: (Translated) He’s behind that wall. Do you hear us?

TOMASZ GRZYB: (Translated) I hear you well.

DARIUSZ DOLIŃSKI: (Translated) Excellent. Then we will begin. We’ll read the first pair of letters.

TEACHER: (Translated) B-A.

TOMASZ GRZYB: (Translated) B-O.

TEACHER: (Translated) O-F.

TOMASZ GRZYB: (Translated) O-F is… A-N.

TEACHER: (Translated) L-A.

TOMASZ GRZYB: (Translated) D-A.

DARIUSZ DOLIŃSKI: (Translated) That’s a mistake. Please press the first button.

TEACHER: For long?

DARIUSZ DOLIŃSKI: (Translated) No, just a short shock.

(Translated) And now, the eighth set.

TEACHER: (Translated) G-A.

TOMASZ GRZYB: (Translated) D-E.

DARIUSZ DOLIŃSKI: (Translated) Mistake. Please press the second button.

NARRATOR: Grzyb is only acting. He is not really wired to the machine.

DARIUSZ DOLIŃSKI: (Translated) Please continue.

NARRATOR: 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 10th switch on the panel, which, if real, would be an extremely painful shock.

Will anyone go so high?

DARIUSZ DOLIŃSKI: (Translated) The experiment requires that you continue.

Please press the third button.

TOMASZ GRZYB: Ah, aah!

DARIUSZ DOLIŃSKI: (Translated) Mistake. Press the fourth button.

TOMASZ GRZYB: (Yells) Aah!

DARIUSZ DOLIŃSKI: (Translated) Please press the fifth.

TOMASZ GRZYB: Ah!

DARIUSZ DOLIŃSKI: (Translated) Please press the sixth button.

TOMASZ GRZYB: (Yells) Aah!

DARIUSZ DOLIŃSKI: (Translated) Mistake.

TOMASZ GRZYB: Ah!

DARIUSZ DOLIŃSKI: (Translated) Mistake.

TOMASZ GRZYB: Ah!

DARIUSZ DOLIŃSKI: (Translated) You have no choice.

TOMASZ GRZYB: Ah!

DARIUSZ DOLIŃSKI: (Translated) Please press the 10th button.

NARRATOR: With an authority figure ordering them, most people go all the way to the highest shock level.

TOMASZ GRZYB: We had about 220 participants, and about 90 percent of them were able to go up to the 10th switch.

NARRATOR: Many people think they wouldn’t follow orders to commit violence, but the work of Grzyb and Doliński suggests this capacity is in most of us.

TOMASZ GRZYB: 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.

ABC NEWS, NIGHTLINE: Hate no longer hides behind hoods.

NARRATOR: Which lands us in the present. It’s clear that the story of human violence is not simple. Peace is not a forgone conclusion.

ABC NEWS, NIGHTLINE: ...reminiscent of images from a dark American past.

IAN MORRIS: 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.

CBS EVENING NEWS NEWSCLIP: The president’s extraordinary tweet raised the real possibility the U.S. and Russia could soon be shooting at each other.

ERICA CHENOWETH: Peace is being treated as something that automatically comes to pass, and we really can’t take it for granted.

EURONEWS NEWSCLIP: In the U.S., violent clashes broke out on Saturday in the city of Portland, Oregon.

STEVEN PINKER: 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.

NEWSCLIP: We still don’t know just how many gunmen are out there and when they will be found.

STEVEN PINKER: 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.

NARRATOR: And to do that requires stepping back and trying to understand why the world feels so violent in the first place.

ROBERT MUGGAH (Igarapé Institute): We are a super-saturated 24/7 information society, and “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.

CNN NEWS CLIP: REPORTER: Reynolds streamed what happened next live on Facebook.

FACEBOOK CLIP: He was reaching for his wallet and the officer just shot him in his arm.

VINCENT BROWN: 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.

NARRATOR: All this information feeds a particular bias long known to neuroscientists and psychologists.

STEVEN PINKER: We call it the “availability” heuristic. We judge risk and danger according to how quickly examples pop into mind.

CNN NEWS CLIP: The van raced along at close to 50 miles an hour.

STEVEN PINKER: So, if there’s a terrorist attack in the news, we think that terrorism is skyrocketing upward.

ROBERT MUGGAH: 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.

NEWS VOICE: North Korea’s nuclear tests…

STEVEN PINKER: A diet of news stories will fool us into thinking that violence is much more prevalent than it really is.

NEWS VOICE: …ever closer to a deliverable nuclear target.

JOSHUA BUCKHOLTZ: 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.”

NARRATOR: 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 10 times higher.

ROBERT MUGGAH: 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 and among certain communities.

NARRATOR: 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.

ROBERT MUGGAH: Income inequality has a very strong statistical relationship with overall levels of homicide.

NARRATOR: 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.

DEDRA D. LAYNE (Safe Streets Baltimore): 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.

NEWS CLIP: Baltimore City has seen 250 murders so far this year.

STANLEY “PORKY” DENNIS (Safe Streets Baltimore): Once violence starts, it spreads.

NEWS CLIP: You can see the gun in his left hand.

NEWS CLIP: The gunman is still on the loose here in Baltimore...

PORKY DENNIS: 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.

NARRATOR: Without the resources to fix the underlying problems, this neighborhood is turning to an innovative intervention to reduce violence.

GARY SLUTKIN (Cure Violence Global): 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.

NARRATOR: 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.

GARY SLUTKIN: 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 going, like, saying, “Oh, my god, you know, this is exactly like every infectious disease.”

NARRATOR: And just like a disease, under certain conditions violent acts are contagious.

GARY SLUTKIN: One case of violence causes more cases of violence, just as one case of flu causes more cases of flu.

NARRATOR: So, could the same methods used to fight infectious diseases also stop shootings?

RASHAD SINGLETARY (Safe Streets Baltimore): The shootings that we have had, most of them, these two are inside here.

NARRATOR: That’s an idea being tested at Baltimore’s “Safe Streets,” one of a growing number of programs adopting Slutkin’s approach.

PORKY DENNIS: There’s just a lot of shootings going on in the neighborhood, so we’re just really trying to get to the bottom of that.

GARY SLUTKIN: The starting point in any epidemic is to detect where the next event might occur and interrupt the exposure.

RASHAD SINGLETARY: So, what’re we going to do today, for canvassing?

PORKY DENNIS: I mean, it’s been a lot of things going on in the neighborhood, so I’m going to just take a tour.

NARRATOR: To do that Slutkin created a new type of public health worker: a “violence interrupter.”

GARY SLUTKIN: 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.

NARRATOR: The first step in fighting any epidemic is to identify the initial outbreaks, the so called “hot spots.”

STEPHANIE IRWIN (Safe Streets Baltimore): 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 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.

NARRATOR: Once the hot spots are pinpointed, the violence interrupters are deployed.

DAMIAN “BURT” McNEIL (Safe Streets Baltimore): Lately, there’s been a lot of activity in the community, so we’re just coming through, trying to make sure everything’s at peace.

NARRATOR: This team works in Park Heights, one of the most dangerous neighborhoods in the city.

PORKY DENNIS: Most of the violence is spontaneous. So, we just try to do our walks so we can be there to try to catch it.

BURT MCNEIL: What really makes the program is the guys out here doing the footwork, doing the groundwork, because it’s our credibility that really keep the peace.

PORKY DENNIS: We just try to get in everybody’s heads and everybody’s minds and let them know the shootings and homicides are not normal. It’s not normal for somebody to lay right there with five or 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.

NARRATOR: Steve Diggs, better known as Peppy, knows these streets.

STEVE “PEPPY” DIGGS (Safe Streets Baltimore): 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’d start swimming towards Park Heights.

NARRATOR: And he knows all about the violence.

PEPPY DIGGS: I fell in love with the streets, the whole lifestyle of it: the girls, the money, the respect that you get in your neighborhood, 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 10 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.

WOMAN 1: For what? I didn’t do anything to her.

NARRATOR: Today, Peppy is following up on a violent altercation.

PEPPY DIGGS: I couldn’t understand how it got that far in the first place.

WOMAN 1: Look at my face. She beat me in my face, kicked me in my back.

WOMAN 2: I felt a threat. She’s yelling, belligerent.

PEPPY DIGGS: We’re going to do it one at a time, okay?

WOMAN 2: You went to me, like this.

WOMAN 1: No! Uh-uh!

WOMAN 2: Yes, you did. And then that’s when I blacked out on you.

WOMAN 1: You was pummeling me.

PEPPY DIGGS: All right.

WOMAN 2: Because you were trying to grab stuff. I don’t know what you’re doing.

WOMAN 1: I’m grabbing my phone!

WOMAN 2: See how you’re doing?

PEPPY DIGGS: Right now, you’re not listening to each other.

WOMAN 1: I know, but…

PEPPY DIGGS: You’re not hearing nothing she said, because you’re so ready to talk back. Maybe it’s something else.

WOMAN 1: Absolutely,…

WOMAN 2: I will have to leave.

WOMAN 1: I don’t have a problem.

WOMAN 2: With all this, I want to leave, because I feel out of place.

PEPPY DIGGS: 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.

NARRATOR: Later Peppy is dispatched to diffuse a potentially deadly dispute.

MAN 1: Unfortunately, we live by the gun around here.

NARRATOR: 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.

MAN 1: Let me see your hands, yo.

MAN 2: You ain’t seeing my **** hands.

MAN 1: Let me see your hands, yo.

PEPPY DIGGS: You didn’t come ‘round here for no smoke. You didn’t come ‘round here for no smoke, right? You didn’t come ‘round here for no smoke, right? Right? Listen, there’s no smoke. Tell him what you just told me.

MAN 1: Let me see your hands, yo.

PEPPY DIGGS: You keep your hands out your pockets. You’re making me nervous, yo.

MAN 2: If it wasn’t for this dude here, man, let me tell you something, man, it would go a lot different than this, right?

PEPPY DIGGS: I know that. I know who you is. I know who is. This is done right here.

That’s how you know it’s not going to happen again. Right?

MAN 1: Man, you’d do the same thing, though.

MAN 2: You’re mother******* right I would do the same mother******* thing.

PEPPY DIGGS: All right, okay, now we’ve got common ground. We’ve got common ground.

MAN 2: You would have.

PEPPY DIGGS: Can we agree that you apologize, yo?

MAN 1: Absolutely.

MAN 2: I’m going to accept that, man, but I’m going to tell you this, man, you don’t come back from that death ****. There ain’t no coming back from that.

PEPPY DIGGS: I say you go and shake his hand, go shake his hand. I mean, like, you owe the man that.

MAN 2: I’m going to leave this be.

PEPPY DIGGS: 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.

BURT MCNEIL: A lot of times guys want to put an end to the conflict, especially when them guns get to going. 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 nothing.”

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.

ALBERT “FUSSY” BROWN (Safe Streets Baltimore): All right, okay, so what’s the next part? What you got to do? What you got to do to get yourself right? Stop all this other **** from happening.

SAFE STREETS PARTICIPANT: I want to leave drugs, try to get a job. That’s it. I swear, I want to leave drugs.

FUSSY BROWN: Because, you know what? We got to deal with one thing at a time, you know what I’m saying? We got to deal with the big issue.

SAFE STREETS PARTICIPANT: It ain’t funny, yo.

PEPPY DIGGS: A lot of violence comes 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.

DEDRA LAYNE: 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.

NARRATOR: 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.

ROBERT MUGGAH: Because they come from the public health field, they set a very high bar for evidence.

GARY SLUTKIN: Cure Violence has been evaluated for its work in Chicago and Baltimore, in New York and Honduras and Mexico, in New Orleans, in South Africa, and repeatedly the findings are that shootings and killings go down by between 40 and 70 percent. And it’s sustained.

Behaviors that were formed years ago can be completely changed.

PEPPY DIGGS: 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.

STEVEN PINKER: 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.

NARRATOR: 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.

ROBERT MUGGAH: 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 C.D.C. because of, let’s call them “disagreements” in Congress.

NARRATOR: But the research that is available points towards solutions.

ROBERT MUGGAH: 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.

NARRATOR: Take the example of Australia: following a mass shooting in April 1996, that took 35 lives, reaction was swift.

NEWS CLIP: The Prime Minister, John Howard, tonight detailed sweeping plans to reform Australia’s national gun laws.

ROBERT MUGGAH: Instead of having an agonizing debate that went nowhere about what to do about it, what you had was action.

JOHN HOWARD PRIME MINISTER OF AUSTRALIA, NEWS CLIP: To achieve a total prohibition on the ownership of all automatic and semiautomatic weapons,…

ROBERT MUGGAH: 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.

NARRATOR: Assault weapons were banned and over 650,000 were turned in to the government. Gun-related homicides plummeted.

STEVEN PINKER: When Australia passed a stringent gun-control measure, rampage killings, which had afflicted the country, fell pretty much to zero.

NARRATOR: In the 23 years after the ban, Australia had only two mass shootings, with a total of 10 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.

ROBERT MUGGAH: 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.

NARRATOR: With the help of data, even the most intractable problems can become a little less daunting.

STEVEN PINKER: 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.

NARRATOR: 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.

ABC NEWs World News tonight, NEWS CLIP: The Syrian regime just attacked its own people with chemical weapons again, a war crime.

SALMA MOUSA: 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.

NARRATOR: 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 QARYO HANA (Iraqui Christian Former Refugee): (Translated) When ISIS attacked Nineveh Plains in 2014, all the people had to flee. Sectarianism was quite rampant in Iraq. Killing people was based on their identity cards.

NARRATOR: Rami’s mother thought they would only be gone for a few days.

LOLA MALALHA EYLAS (Iraqui Christian Former Refugee): (Translated) When we fled, we were saying, “Today we will go back, or maybe tomorrow.” But there was no returning. We were stuck. We had to stay. And what did I do? I was praying to the Virgin Mary. “Virgin Mary, we just want to go home. Mother Mary, help us, please. In your name, we are praying to you. We just want... help us go back home.”

NARRATOR: 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.

SALMA MOUSA: 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.

NARRATOR: 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.

MOHAMMED MAHDI HUSSEIN (Muslim Member of Ninevah Plain Soccer League): (Translated) Day after day, it gets better. There are many different security forces and there are patrols in Qaraqosh.

NARRATOR: Nonetheless religious tensions still remain high.

The Islamic State will stay as the Caliphate.

SALMA MOUSA: In the wake of a conflict like this, the social trust just becomes obliterated.

We are coming for you, Jews.

SALMA MOUSA: 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.

RAMI QARYO HANA: (Translated) After ISIS, there may still be people who have the ISIS ideology. With respect to our Muslim brothers in Mosul, they are always in our hearts, because we have lived with them a long time. But after what happened, we are still really terrified.

NARRATOR: ISIS may be gone, but two powerful ingredients for violence, prejudice and sectarian hostility, remain.

SALMA MOUSA: 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.

NARRATOR: 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.

SALMA MOUSA: Soccer is something people do just for fun. We just add some tweaks, in terms how to mix up the team composition, to test the idea of contact.

NARRATOR: 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 kickoff in the Nineveh Plain Soccer League. Rami, a Christian, captains his team.

RAMI QARYO HANA: Me and Rayan, the twin of my brother’s wife, scored 9 out of 10 in the tryout. I don’t mean to boast, but everyone can see we’re good.

NARRATOR: Trying to stop him scoring in the opposition’s goal is Mohammed, a Muslim.

MOHAMMED MAHDI HUSSEIN: I’ve played as a goalie since I was a kid. Right now, I’m goalkeeper for the police team, because I am the best.

NARRATOR: They come from different worlds and neither has any idea that they are taking part in an experiment testing “contact theory.”

JAMIL ZAKI: 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.

NARRATOR: 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.

SALMA MOUSA: 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.

NARRATOR: 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.

SALMA MOUSA: 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.”

RAMI QARYO HANA:You rarely see Muslim players play in a Christian team. This is the first time Christians are playing with our Muslim brothers.

NARRATOR: 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?

RABIE ZAKARIA (Ninevah Plain League Organizer): 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.

NARRATOR: 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?

SALMA MOUSA: 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.

NARRATOR: 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.

RABIE ZAKARIA: So we have, almost more than 200.

NARRATOR: Each voucher is tagged with a specific I.D. number, and the restaurant owners help track if people came alone or with others.

MOHAMMED MAHDI HUSSEIN: (Translated) I went with my team. We are friends from different communities.

NARRATOR: The results showed a marked shift in behavior.

SALMA MOUSA: 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.

NARRATOR: And though the changes were modest, her surveys showed a shift in belief that coexistence is possible.

SALMA MOUSA: 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.

RAMI QARYO HANA: (Translated) We are all Iraqis. There are no differences between sects and races. The most important thing, what unites us is love.

MOHAMMED MAHDI HUSSEIN: (Translated) We go to cafes together. We even visit each other on Muslim and Christian religious holidays and celebrate.

NARRATOR: 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!

SALMA MOUSA: 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 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.”

MOHAMMED MAHDI HUSSEIN: (Translated) Sport brings together all these communities and there is no sectarianism. When you’re playing for a championship, there is no race or sectarianism. You are bringing together all religions.

SALMA MOUSA: 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 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.

NARRATOR: Though small steps like these may give people hope, it’s important to keep such results in perspective.

TIFFINY TUNG: I don’t think there’s anything wrong in recognizing that there’s progress. We just want to be sure that, that patting ourselves on the back for that doesn’t obscure what else still needs to be done.

MOHAMED SALIOU CAMARA: Human beings, we are so complex, but our understanding of ourselves, as a species, that understanding evolves.

NARRATOR: 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.

STEVEN PINKER: 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.

NARRATOR: 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?

ANDREW REITER: 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.

ERICA CHENOWETH: 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.

STEVEN PINKER: Until recently, we lived in a world in which slavery and rape and warfare were the norm, not the exception. What changed, over history, is the better angels of our nature predominate over our inner demons.

RASHAD SINGLETARY: We can see shootings going down.

STEVEN PINKER: We’ve done something right. Let’s figure out what it is and make sure we keep doing it.

CAROLYN ROBERTS: 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.