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A new systematic review published in Evolutionary Psychological Science suggests that the life stage of a mass murderer plays a significant role in shaping their motivations, stressors, and target selection. While younger perpetrators are often driven by chronic social rejection and status deprivation, older offenders are more likely to be reacting to acute life disruptions. By applying evolutionary theory, the authors propose that these acts of violence may reflect exaggerated responses to perceived threats to social status and control.
Mass murder is a rare but profoundly traumatic phenomenon. Although psychological and criminological research has documented many of the immediate precursors to these acts, the underlying question of why certain individuals respond to stress in violent ways remains open. The researchers behind this study aimed to address that question by integrating evolutionary perspectives, particularly Life History Theory and models of male competition, into existing frameworks.
This theoretical approach suggests that behaviors related to status, aggression, and reproductive strategy have been shaped by ancestral pressures and continue to influence modern behavior. While the authors emphasize that evolutionary theory does not justify or excuse violence, it may help explain why certain recurring patterns emerge in different types of offenders.
“I’ve been studying mass violence for the past five years, driven by its devastating impact not just on direct victims, but on entire communities and social systems,” explained study author Keith Minihane, a PhD researcher in applied psychology, at University College Cork.
“Despite the attention mass murder receives, there’s still limited understanding of how offenders differ by life stage, and almost no work that systematically examines these differences through an evolutionary lens. This project emerged from that gap. We wanted to know: why do these crimes cluster in late adolescence and middle age, and what might that tell us about the underlying psychological processes at work?”
To identify recurring psychological stressors among mass murderers, the researchers conducted a systematic review of peer-reviewed empirical studies. They searched four major academic databases, along with a manual search, identifying a total of 634 papers. After screening for relevance and applying strict inclusion criteria, 20 studies were included in the final synthesis. These studies all directly examined the motivations, stressors, and behavioral patterns of individuals who had committed mass murder, familicide, or school shootings, excluding ideologically motivated or politically driven cases.
One of the most striking findings was a bimodal age distribution among mass murderers. Offenders tended to cluster in either late adolescence or middle age, with each group displaying distinct behavioral patterns, motivations, and stress responses.
Younger offenders, including school shooters and public mass murderers, were often characterized by a history of social rejection. This included experiences of bullying, exclusion, and romantic failure. In many cases, violence was preceded by a long buildup of grievance, during which the offender internalized a sense of humiliation or insignificance. These individuals often left behind manifestos, videos, or social media posts expressing a desire for revenge or recognition. Some appeared to view mass violence as a way to assert dominance or gain notoriety, particularly after being denied social status during a key developmental period.
In contrast, older offenders were more likely to commit acts of familicide, often killing their partners and children before taking their own lives. These acts were frequently preceded by acute life crises, such as financial collapse, divorce, or job loss. In many cases, the offenders framed their violence as a protective or “compassionate” act—attempting to “rescue” their families from a perceived future of hardship. While the reasoning may appear twisted, the researchers suggest that these actions may reflect a distortion of evolved caregiving mechanisms under extreme stress.
What was particularly surprising was the consistency of these findings, Minihane said. “Younger offenders were often driven by chronic rejection, humiliation, or identity struggles, while older offenders were more likely facing acute crises like divorce, job loss, or financial collapse. These themes emerged repeatedly. Different life stages, different stressors, but both converged on violence as a perceived solution to social failure.”
Across both age groups, revenge was a consistently reported motivation. Whether directed at peers, romantic partners, employers, or family members, many mass murderers appeared to view their actions as a form of retaliation. This was especially true among younger offenders, who often blamed classmates or society for their perceived failures. The researchers point to evolutionary models of status competition and risk-taking to explain why some young men may be especially prone to respond violently to rejection or humiliation.
While younger offenders often survived their attacks, older perpetrators were significantly more likely to die by suicide. Suicide rates were especially high among those who committed familicide. These older offenders appeared to view violence as a final response to what they saw as irreversible status loss or existential failure. Rather than seeking fame or recognition, they often acted in private and left behind notes expressing despair, guilt, or hopelessness.
The review also noted clear sex differences. Mass murder is overwhelmingly committed by men. Women who do commit mass killings often act in domestic settings and tend to target family members using less direct means, such as poisoning or arson. Female perpetrators were also more likely to report motives tied to perceived altruism rather than revenge or dominance. These differences suggest that gendered patterns in violence may reflect underlying psychological and social distinctions shaped by both evolutionary and cultural factors.
“Mass murder is seldom a sudden or random act; it is well planned, sometimes for years,” Minihane told PsyPost. “It’s rarely the result of a mental health crisis in the way people often assume. In fact, people with mental health difficulties are far more likely to be victims of violence than perpetrators. Stigmatizing them only distracts from the real social and psychological dynamics we need to address, these dynamics include social stress, rejection, and perceived status loss. These pressures tap into deep-rooted psychological systems evolved to monitor threats to social standing and identity. That’s important, because it helps us move beyond reactive explanations and toward proactive ways of identifying and interrupting pathways to violence.”
The review also highlights key limitations in the current research landscape. Definitions of mass murder vary across studies, with some setting the threshold at three victims and others at four. This inconsistency can affect who gets included in analyses and may obscure meaningful comparisons across subtypes.
The researchers also acknowledge that the focus on peer-reviewed, English-language studies introduces potential selection bias. While the review includes international cases, much of the available research is based in Western contexts. A broader global dataset would allow for more culturally nuanced comparisons. The authors call for the development of a standardized international mass murder database to enable such analysis.
The authors also emphasize that evolutionary theory is not a replacement for existing models of violence but a complementary tool to help understand consistent patterns.
“Evolutionary psychology is only one lens,” Minihane said. “Other perspectives such as feminist theory (mass murder is overwhelmingly carried out by males), and sociological and criminological approaches, are vital. Our goal isn’t to replace those theories, but to augment them with a broader framework that highlights how age and life-history pressures shape responses to stress. Methodological considerations include our strict inclusion criteria, and, although worldwide studies were included, the literature still mainly focuses on western based offenders.
“This paper is part of a larger effort to build a comprehensive, interdisciplinary framework for exploring extreme violence. One path we’re pursuing now focuses on ‘legacy tokens,’ manifestos, suicide notes, or online posts that reveal how offenders want to be remembered. As we recently saw with the case of Robin Westman, the publication of legacy tokens remains a crucial dimension of mass violence today. Our initial research into this topic revealed significant differences between how those in late adolescence and their early 20s conceptualize their violence as compared with middle aged offenders. This research was published earlier this year in the Journal of Criminal and Police Psychology and offers an initial step in outlining how offenders narrativize their violence.”
“The key point, and I really want to stress this, is that evolutionary psychology does not excuse violence, nor does it offer a singular, explanatory framework,” Minihane added. “Instead, it helps explain why certain patterns emerge when evolved minds encounter modern stressors. By better understanding the distinct trajectories of younger and older offenders, we can improve focused risk assessment, identify warning signs earlier, and ultimately work toward prevention.”
The study, “The Bimodal Age Distribution of Mass Murder: a Systematic Review Using Evolutionary and Life History Perspectives,” was authored by Keith Minihane, Maria Dempsey, and Robert King.
