Understanding the psychology of perpetrators of violence is an important step toward prevention. And the answers are not always in obvious places.

Reading Time: 10 minutes
Inspired by reader Chuck Johnson’s comment on “Between massacres: a uniquely American horror show in seven acts

This time it happened in Uvalde, Texas. A gunman burst into an elementary school, brandishing a weapon designed for combat, and tore our most precious human treasures to pieces. Some of the 19 corpses of nine, ten, and eleven-year-olds that he left strewn across the schoolroom floor were beyond recognition, requiring DNA tests to match parents with the horrific sights, forever searing themselves into memory, that were once their children.

He also killed two teachers. One teacher’s husband of 24 years fell to a fatal heart attack after attending his murdered wife’s memorial.

Deepening our stupefaction, Uvalde police waited over an hour for backup, gifting the gunman his ghastly free rein. Police also handcuffed, pepper-sprayed, and threatened to tase terrified parents who were begging them to rush in. The GOP deflected any focus on sensible gun legislation, praised the heroics of Uvalde cops, and accused the Democrats of politicizing the shooting. Democrats screamed their calls for gun regulation into the void. The religious did something similar with their prayers.

As a parent of two children in grade school, I sobbed in empathy with the parents. Somehow, living a mere hour away made our imagined reversed positions more plausible. And as a father, my protective instincts made me want a visible, corporeal enemy to fight, if only to dispel my feelings of helplessness. I was not alone. An entire nation suffered the kind of moral injury it only experiences when its most sacred social contracts are once again torn to shreds, discarded, and left to dissolve in the senselessly spilled blood of innocents. 

How do we begin the process of sense-making? As a psychologist who has spent his entire career specializing in PTSD, I can tell you that sense-making will never fully blunt the impact of trauma. But it may offer insight toward prevention. 

Among mass shooters, there is a prototype: young, male, outcast. Not every shooter fits this description. But many do, and thus far our attempts at understanding why this is true have only skimmed the surface. By diving deep into our past, evolutionary psychology can explain why this demographic matters, particularly in the United States.

The reasons concern male competition for mates. To those unfamiliar with evolutionary psychology, the connection may not be evident. If we are to gain understanding on which to build prevention, it’s worth the time to connect the dots.

The different reproductive strategies of men and women

Men and women engage in different reproductive strategies. Perhaps the easiest way to explain these differences is as quantity versus quality. Across every culture on Earth, men tend to prefer more sexual partners than women. Men prefer “quantity” because men’s reproductive success is directly related to the number of copulations (a reality not shared by women). One study found that men are four times as likely as women to fantasize about having sex with over a thousand partners over the course of their lives.

Women tend to be far choosier because their reproductive resources are far more limited—constrained by the time between adolescence and menopause, pregnancy, and 500 total ova across the lifespan (whereas men produce sperm by the millions well into their geriatric years). For this reason, women across the globe prefer “quality,” which usually equates to men with greater resources to support the prodigious human task of childrearing.

The worldwide sex ratio is roughly 50-50. But the operational sex ratio (OSR), or the number of reproductively available males to females, tends to skew much higher on the male end. Women’s shorter fertility window, greater choosiness, and the fact that, when possible, powerful men will horde women through polygyny, all create effectual women shortages. To use the idioms of economics, low supply creates high demand, which intensifies competition.

Most male mammals, countless monkey species, and all of the great apes compete violently for access to mates. Male baboons will draw blood with dagger-like canines to win “harems,” male gorillas will fight for sexual supremacy, and male chimpanzees will conduct raids on the rival troop, systematically kill the males, and absorb remaining females into their own.

Human males follow this pattern as well. In our ancestral past, the motives behind violent competitions were transparent. Hunter-gatherer tribes conducted raids on their rivals, killed their male competitors, and captured their women, thereby increasing male evolutionary fitness. The Book of Numbers recounts this startling behavior among the Judaic tribes of the biblical era. Here Moses, ostensibly at the command of God, orders his men: 

Now kill all the boys. And kill every woman who has slept with a man, but save every girl who has never slept with a man (31:17-18)

In the modern era, ISIS and Boko Haram have gone to war with the stated intention of killing their male rivals and capturing their women as the spoils of war, demonstrating that this dark instinct has not disappeared. It’s worth adding that wartime rape has been staggeringly common across human history, curbed only when sternly punished—the Russian Army, for example, raped an estimated two million German women during WWII.

Obviously not all male mating opportunities are won by violence. In modern times, mutual choice is by far the worldwide norm. Even so, our brains evolved at a time in which fighting for female mates was far more common. And in peacetime, women bring their mating imperatives to the game—that ever-stable preference for men with more resources. And this is where the demographic above matters. Higher-ranking, older, established men usually have greater access to such resources. 

Conversely, younger men often enter the arena of competition with fewer resources to offer women, which behavioral ecologists call “embodied capital”. They must compete with higher-ranking, wealthier men which, again, women prefer given the high costs of childrearing. In fact, research finds that when sex ratios skew male, women expect men to spend more money on them in their courting efforts. Facing these demands, and the evolutionary peril of mating failure, violent risk-taking among young males has been an evolutionarily practical strategy—not desirable, but effective, impelling young men to gain scarce or monopolized resources, challenge the existing male dominance hierarchy, or even raid the rival tribe. Young men among our ancestors who couldn’t take risks were more likely to become evolutionary dead ends. Today, risk-taking and criminal behaviors are strongly associated with being young and male across the globe. Moreover, among men, reproductive peak coincides with peak inclination for violence, a phenomenon known as young male syndrome.

ON THE OTHER HAND | Curated contrary opinions

David Buller, Sex, Jealousy & Violence: A Skeptical Look at Evolutionary Psychology (Skeptic)

And so, when mating opportunities look bleak for males, the ancient drive to compete rises to the surface. In societies in which polygyny is allowed, a shortage of women is created, and we see more civil wars as young males make war against the established male dominance hierarchy. Economics also matters. Large income inequalities can incentivize women to partner with wealthy men, or remain single if only low-earners are available. Perhaps it’s no surprise that high income inequality is also associated with higher rates of violent crime as men engage in risk to achieve higher rank status. 

Among men, reproductive peak coincides with peak inclination for violence, a phenomenon known as young male syndrome.

But could mass shootings really be about mating?

In 2015, a 26-year-old male fatally shot eight students and a professor at Umpqua College in Roseburg, Oregon. He left behind a manifesto complaining that “I am going to die friendless, girlfriendless, and a virgin.” In 2014 a 22-year-old male went on a killing spree in Isla Vista, California, stabbing and shooting to death seven victims. He referred to himself as an “incel” (involuntarily celibate) and uploaded a video in which he stated, “I’m 22 years old and still a virgin, never even kissed a girl…It has been very torturous.” In 2021, a 22-year-old male shot five people to death in Plymouth, UK, and injured two others before fatally shooting himself. He referred to himself online as a “fat, ugly virgin.” In 2020, a 20-year-old male shot up a shopping center in Glendale, Arizona, injuring three. Reporting that he had been bullied his whole life, he self-described as incel, and specifically targeted couples because he wanted them to “feel his pain.” Tellingly, he sent a video of the shooting to a woman he wished to impress.

The list of incel shooters goes on, and the link between incel culture and male mate competition is gaining clarity. One study examining over 320 million US Twitter posts found that tweets referring to incel subculture were most likely to emanate from regions with male-biased sex ratios and high income inequality.

Let’s not make the mistake of thinking, concretely, that all mass shooters are literally looking to gain mates through violence. Many commit suicide in the process or know very well that they’ll get killed by police. What we have instead are evolutionary potentialities baked into the psychology of young men, activated by a confluence of social and cultural pressures. In the United States, those pressures create ruinous hair triggers. 

What we have are evolutionary potentialities baked into the psychology of young men, activated by a confluence of social and cultural pressures.

While detailed arguments for gun control can be found elsewhere, it is worth mentioning that in the US, frustrated young males have easy access to military-grade weapons. Ease of access is a no-brainer—it gives our impulses lethality. This is why a primary task of clinicians working with patients at high risk of homicide or suicide is to reduce access to lethal means. Though this practicality is perpetually deflected by conservative opponents of gun control, would those same patriots argue that a suicidal veteran should have access to firearms? As concerns weaponry, America gives young men’s ancient, volatile evolutionary impulses the firepower it never possessed until the modern age, with the potential for high casualties. Needless to say, those same gun-control opponents would immediately prefer an AR over a six-shot revolver in a combat situation because they understand the basic calculus of firepower. 

The role of social rank

Another potential trigger in the US is its enormous rank disparities. As one indicator, the income differences between CEOs and frontline employees is as high as 340:1. Moreover, we laud the rich, famous, beautiful, and powerful in the US, and media floods us with their likenesses, which may create the impression of unattainable rank status. By exalting the ethos of homecoming kings and queens, the football stars and cheerleaders, and showing relative indifference to unpopular kids, mainstream high school culture unwittingly does something similar.

In short, competition is the American way. And while this is among its greatest assets, when left unchecked there are dreadful side effects, including the tyranny of bullies and the macabre vengeance of school shooters.  

Moreover, while some anti-bullying campaigns have been rigorous, most school officials don’t understand something critical about bullying—that it happens within the context of male mate-competition. The bullied are by definition the lower ranking, and typically less successful at attracting mates. Evolutionary psychology shows us that, given enough pressure, subordinated young men have the potential for violent reactions, inherited by an ancient legacy of male competition, designed to secure rank and the mating opportunities rank affords. 

Given enough pressure, subordinated young men have the potential for violent reactions, inherited by an ancient legacy of male competition, designed to secure rank and the mating opportunities rank affords. 

In recognizing the evolutionary links between rank, access to mates, and propensity for school shootings, could we work to temper school social dominance hierarchies with better precision? Could we even fathom helping disaffected young men achieve success at dating? Or even a healthy sex life?

That teenagers deserve sexual health would seem to clash against the divorced-from-reality stance of America’s religious right, which has vigorously championed abstinence-until-marriage campaigns and even resisted teaching sex-ed to high schoolers. We would have our work cut out for us. 

The Uvalde police response

The Uvalde police response is another matter. As I explain in the book Sex, Power, and Partisanship, our modern-day political psychology was forged by the pressures of our ancestral past. The intensity of intertribal warfare among our ancestors has shaped our fear of outsiders and the tendency to turn inward to the tribe. Like other traits, these fall on the natural curve. With their support for military spending, tough immigration policy, and hawkish foreign policy stances, conservative politics draw those with greater tendencies in this direction, and indeed, as imaging studies show, those with larger fear centers of the brain.

A closer look at a foundational instrument used to measure political conservatism called the Right-Wing Authoritarianism (RWA) scale reveals its militaristic logic. This scale is comprised of three factors:

  1. High deference to authority figures
  2. High conformity to one’s tribemates
  3. Aggression toward outsiders

For their utility in coalitionary violence, these factors are embedded in military social structure. Conformity is necessary to coordinate actions, as is obeying orders—how quickly would an army get slaughtered if its soldiers did their own thing, or weren’t especially obliged to obey commands? And aggression against outsiders is the very purpose of militaries, descended as they are from the coalitions of males that protected the primordial tribe from raids, or conducted them to win scarce resources.  

The concept of RWA was uncovered by scientists in the aftermath of WWII who were struggling to understand what gave the world Adolf Hitler and the Nazi Party. A tendency for unquestioning obeisance and conformity is necessary for combat operations, but it also resulted in the atrocities of Auschwitz and Treblinka, inhibiting German soldiers from disobeying their command structure or stepping out of line from their peers. We have come to understand how RWA forms the psychological gearwheels in the machinery of atrocities, in both their commission and in their allowance. 

RELATED: Why we don’t want cops at Pride celebrations

It may seem logical that law enforcement would self-select for this personality type. It would appear that the Uvalde police response is another example of RWA turning in on itself. The Uvalde police commander appeared to have favored the safety of his own men rather than considering the other lives at stake, as we would expect of a psychology designed for tribal insularity. No one under his command disobeyed the orders to holster. None of these armed men broke ranks to rush the shooter. One video emerged of desperate parents asking police why they weren’t rushing in to save their children. Police responded by physically pushing parents and screaming, “because I’m here dealing with you!” Once again, instead of alliance, parents were met with pepper spray, handcuffs, and even contempt. When the stakes and adrenaline levels were at their highest, parents, it appeared, were not seen as members of Uvalde police’s tribe. 

It would appear that the Uvalde police response is another example of Right-Wing Authoritarianism turning in on itself.

There may be a case for considering high RWA as a liability in police work. The human brain evolved in small bands, topping off at 150-200 individuals, that were perpetually at war with one another.  Military units, business organizations, farming communities, and many other social groups mirror the group sizes of early hominids. When groups exceed those sizes, organization and cohesion tend to break down. In other words, our brains appear to be naturally calibrated to function in small tribes, and we strain, both cognitively and emotionally, against those calibrations. It may be that police who possess greater RWA inclinations may be especially handicapped, having the greatest difficulty seeing past their tribemates in blue to the communities that employ them, and seeing that their commitment to having their tribemates’ backs, to the death if necessary, extends beyond the men and women beside them.

There are many ways in which our evolved psychology strains against the modern worlds that we have created for ourselves. The better we understand them, the less we suffer.


Avatar photo

Hector A. Garcia

Dr. Hector Garcia is a clinical psychologist, researcher, and Assistant Professor in the Department of Psychiatry at the University of Texas Health Science Center at San Antonio. He is also the author...