Velina Kozareva ’16, THURJ Staff

Looking at the world today, it’s easy to assume that violence is on the rise. From the apparent spate of shootings in places like Aurora Springs and Newtown to our own recent Boston Marathon incident, human aggression seems to be steadily increasing. However, according to Harvard professor and New York Times bestselling author Steven Pinker, the opposite is in fact true. In his 2011 book The Better Angels of our Nature: Why Violence has Declined, Pinker weaves together evidence from studies in psychology, neurobiology, and historical statistics to show that the 21st century may actually be “the most peaceable era of our species’ existence.”

In the first part of the book, Pinker aims to demonstrate that the rates of virtually all forms of human violence – war, homicides, domestic and child abuse, even animal abuse – have decreased over the millennia. Surprising as this may be at first glance, it becomes rather plausible when we perform a sanity check and really reflect on our knowledge of cultures past. Consider for instance, clues derived from prehistoric remains, such as those of the North American Kennewick Man, whose skeleton contained a stone projectile firmly embedded in his hip. Clearly he did not live a peaceful life. We can glean even more insights into humans’ violent history from ancient accounts of fratricide in the Hebrew bible, torture in the Middle Ages, and fatal duels in the 18th and 19th centuries. As far forward as the 20th century, we observe an acceptance for certain kinds of domestic abuse (in ads that feature husbands casually beating their wives) that would not be permitted under today’s standards.


Pinker then provides concrete statistics to back this anecdotal evidence, mostly in terms of numbers of relative deaths per population, and highlights six distinct transitions in human history which illustrate the decline of aggressive acts of all forms. The first of these is the Pacification Process, our species’ transition from a largely lawless pre-agricultural state of anarchy, to more civilized societies regulated by governments. This change significantly reduced the percentage of deaths due to war party raids and cannibalism. After humans established governments, they underwent what Pinker calls the Civilizing Process, during which homicide rates within established states plummeted. This trend arose in the feudal era as people began exercising more self-control, in addition to seeing the value of having more neighbors alive rather than dead. After all, keeping neighbors around meant that one could barter or cooperate with them if need be, and also that one wouldn’t be punished by the law-enforcing government for committing acts of aggression.

Later, around the time of the Enlightenment, previously sanctioned forms of violence, namely torture, slavery, sacrifices, witch killings, and duels started to go out of fashion too, in a process known as the Humanitarian Revolution. In fact, most of these, including slavery and human sacrifices, were almost completely abolished within a few centuries. Accompanying this change, and likely causal, was an increased reliance on reason and an emphasis on empathy for fellow humans.

Examining the death tolls of large-scale violence – wars and massacres – also leads us to debunk the theory that “the 20th century was the bloodiest in history.” In reality, of the ten most costly slaughters in human history (in terms of relative death toll), only one, World War II, occurred during the 1900s. Based on additional evidence that the frequency of wars between Great Powers has steadily decreased, it seems we are in the midst of a “Long Peace.”  This is further reflected by the fact that nations across the globe have significantly reduced their lengths of military conscription and their relative proportions of military personnel.

Somewhat in conjunction with the development of the Long Peace is the more recent New Peace, a drop in levels of terrorist and genocide violence since the conclusion of the Cold War. This is perhaps the most controversial point that Pinker makes in Better Angels, and even he admits that this trend is not as decisive (or as likely to last) as the others he describes. After all, major terrorist acts do still occur – and sometimes alarmingly close to home. It is important to remember however, that the current prevalence of democracy and anti-war sentiments which allow for the relative peace we all enjoy are a significant improvement over the conditions of just a few decades ago.

Finally, the last transition Pinker details – the Rights Revolutions – is perhaps the one most immediately relevant to our daily lives. All of us, in some way, have felt the effects of the civil rights, women’s rights, or gay rights movements. Looking back at cultural norms, we can easily appreciate society’s changing perspective on domestic violence, corporal punishment, and even cruelty towards animals. Thus, it is not hard to believe that because of this, related forms of violence, including sexual assault and hate crimes, have declined since the early 1900s.

While a clear and fairly convincing demonstration that all types of aggression among humans have decreased, these trends now beg the question: why have humans changed so much with regards to violence? Is this a result of purely social and environmental mechanisms, or are we actually evolving into a more docile species? Before we can answer this, we should first understand more about how violence arises, from both a biological and psychological perspective.

Violence and aggression are not unique to humans – anyone who has ever seen cats fighting in the street or Discovery Channel’s Shark Week knows as much. It must therefore be evolutionarily conserved across species, though we might wonder – why? Violence often results in injuries, loss of resources, and occasionally death for the participants. If we consider it in terms of cost-benefit analysis however, we can rationalize aggression between individuals. In environments with limited food sources for instance, the benefits of violence against others in the population – fewer   competitors for food and an increased chance for survival – can far outweigh the costs – the effort expended and the risk of injury. The same principle applies to protective aggression, where an individual’s life may be on the line. It seems then that natural selection would create populations of organisms with at least some propensity for violence (Archer, 2009).

In addition to pinpointing these evolutionary reasons for aggression, scientists have worked extensively to determine the genetic and neurobiological mechanisms underlying violent acts. Aggression is not controlled by a single neural circuit, and examining the different systems can provide insight on the types of situations that induce human aggression. One of the more extensively studied systems is called the rage circuit, comprised of a section of tissue called the periaqueductal gray (PAG), the hypothalamus, and the amygdala. As implied by its name, the rage circuit can cause people to lash out in anger. Related to this is the fear circuit, which is triggered during threatening situations and underlies protective violence.  In addition to these reactive forms of aggression (found in both humans and animals), humans sometimes display controlled-instrumental violence, which is more calculated and involves higher-order neural systems (Nelson and Trainor, 2007).

Suppressing the compulsion for both types of aggression is the orbitofrontal cortex, which is involved in inhibiting emotions and impulses of all kinds. Many have heard of the classic case of 19th century railroad worker Phineas Gage, who survived having a tamping iron pushed through his skull, but suffered damage to his frontal lobe. For the rest of his life, he was reported to be easily irritated, impulsive, and lacking self-control. Since his time, there has been additional empirical evidence in support of this role of the orbitofrontal cortex, though unfortunately, scientists have not determined the exact mechanism of impulse control.

Even less is known about the genes which are most closely associated with patterns of violence, though again, some rare cases have provided researchers with valuable insights. Take for instance, the 1970s case of the Dutch lineage where brazen aggression seemed to run consistently in the men of the family. For decades, fathers, brothers and sons had been committing violent crimes, and when the last generation of women wished to know if this was a genetically-determined condition, a team led by geneticist Han Brunner discovered some interesting results. They found a single point mutation in the gene for monoamine oxidase A (MAOA), which resulted in the translation of a truncated protein, leading to complete loss of function in MAOA activity. Since MAOA is crucial for metabolizing noradrenaline, dopamine, and other transmitters associated with the neural pathways of aggression, it was no surprise that this deficiency would have a significant impact on levels of violence in the family.

Other mutations influencing the activity of MAOA – not quite as severe as the one in the Dutch family – exist in various populations and may account for some of the variation in aggression seen among individuals. However, the roots of aggression are definitely not so clear-cut when it comes to other genes; even now this remains an open field of research for geneticists and neurobiologists.

We can tie this information into Pinker’s own psychological analysis of violence, where he provides a more detailed taxonomy of categories of violence, which he names “inner demons.” Beginning with predation – perhaps the simplest and most practical kind of violence – he also enumerates dominance, revenge, sadism, and ideology. Predation is simple in that it does not involve any anger or desire for destruction – it is violence as “a means to an end,” whether that end is nourishment or elimination of a threatening individual.

angel01Dominance on the other hand, is a much more complex motivation, influenced at least partly by levels of testosterone. This reality is what fuels the exaggerated claim that only men participate in dominance contests. In fact, the drive for dominance exists among both men and women, and can be individual or social, depending on one’s level of loyalty to social groups.

While dominance is a proactive attempt to establish your supremacy, revenge is retroactive, stemming from a desire to punish someone who has hurt you. This clearly comes with an end-goal – to deter that individual from hurting you again. However, because of people’s tendency to see themselves in a better light than their opponents, a phenomenon known as the Moralization Gap, revenge can cause large conflicts to escalate from misunderstandings.

Perhaps the most difficult motivation to understand is sadism. After all, most of us probably believe that we don’t have any true desire to see others in pain, yet sadism really exists on a gradient in all individuals. It underlies the oft-satirized concept of schadenfreude, that somewhat guilt-inducing pleasure we experience when someone we don’t like trips and falls. Fortunately though, sadism is largely suppressed by our empathy and rational inhibitions. It is in the few cases when it’s not that sadism actually leads to violence.

The final root of aggression as detailed by Pinker is ideology, which often leads to calculated execution of large-scale killings in an attempt to create a more ideal world. This motive was the cause of such atrocities as the Crusades and the Holocaust, and is especially dangerous because it easily permeates large groups of people.

Now we return to our original question; with all of these reasons for aggression, why would violence among humans be on the decline? According to Pinker, biological evolution is probably not the reason. Some of the transitions he describes – such as the Rights Revolutions and the New Peace –happened over the course of only a few human generations, far too short a time for evolutionary genetic changes to take place. Based on this observation, he posits that the same changes in environmental factors that caused these short term transitions could also have brought about the more sweeping transitions, simply by operating over a longer period of time.

Also in support of this theory is Harvard Psychology Professor Joshua Buckholtz, who attributes the overall decrease in violence to cultural and social shifts, such as the introduction of third-party norm enforcement through government and law. This helped limit the need for aggression motivated by revenge, while simultaneously deterring violent acts driven by predation and dominance.

Another especially important factor, Buckholtz says, is the “ultrasociality” of humans, a trait unique to our species, as it allows us to cooperate with people completely unrelated to us. High levels of cooperation naturally facilitate the creation and enforcement of social norms which discourage violence. These in turn encourage the use of people’s “better angels” – the aspects of our minds which work to restrain our aggressive impulses.

Pinker counts empathy, self-control, morality and reason as better angels, with reason being the most important. Reason, he says, is more versatile and reinforces the other three better angels, though these forces all interact with each other in some way. For instance, expanding our range of empathy can allow us to improve our sense of morality. The more people we sympathize with, the more likely we are to feel a moral obligation to defend their safety. Of course, it can be difficult to sympathize with everyone else in the world at all times, so reason is necessary for us to see that all people, even the ones not related to us, have a right to safety. Similarly, rational thinking can demonstrate that some forms of violence, such as witch-burnings, which in the past were considered morally correct, are actually not legitimate.

Self-control is also useful in limiting our occasional aggressive urges, but it can wax and wane quickly, depending on the strength of our temptations. In fact, scientific studies have shown that depletion of an individual’s self-control during one activity can make him more prone to violence immediately after. Once again, reason can help where self-control fails, by allowing us to act rationally even when our instincts suggest otherwise.

While these “better angels” are a fundamental and relatively constant part of human psychology – just as the “inner demons” are – the strength of their influence on people’s actions has also grown significantly over the course of human history. Besides social norm enforcement, there are several other historical forces which helped drive this proliferation of the better angels, including the introduction of commerce and cosmopolitanism.

The dawn of original cosmopolitanism came with the invention of the printing press and the subsequent spread of books and literacy. Now though, cosmopolitanism goes hand-in-hand with mass media, which is somewhat of a double-edged sword. On the one hand, mass media increases global awareness and allows us to better understand the effects of all types of violence, thus improving our empathy. Yet media also has a habit of sensationalizing violence in a way that creates an “environment of despair,” as Pinker puts it. Every new story of crime and war can make it seem that limiting human violence is hopeless. Certainly it is not easy, but as Better Angels strives to show us, we have actually improved with regards to reducing violence on a large scale and can continue to do so in the future.

Overall, Pinker’s latest bestseller will appeal to students and teachers in a variety of fields – from evolutionary biologists and psychologists, to economists and statisticians. His witty tone and clear explanations of complex topics combine to make the book both accessible and informative. More importantly, with its wealth of comprehensive evidence for the decline of violence, The Better Angels of Our Nature successfully paints a more hopeful picture of the world and humanity and encourages us to focus not what we have been doing wrong, but on “what we have been doing right.”


Pinker, Steven. The Better Angels of Our Nature: Why Violence Has Declined. New York: Penguin Books, 2011. Print.

Nelson, Randy J. and Brian C. Trainor. “Neural mechanisms of aggression.” Nature Reviews Neuroscience 8 (2007): 536-546.

Archer, John. “The nature of human aggression.” International Journal of Law and Psychiatry. 32 (2009): 202-208.