Exploring the biological underpinnings of violence against women through neuroscience, genetics, and brain chemistry
Women and girls intentionally killed worldwide in 2023
Of femicides committed by intimate partners or family members
Lives taken by those who should be trusted
A woman killed by an intimate partner
From the "narco-femicide" of three young women in Argentina, live-streamed to dozens of viewers 2 , to the steady toll of domestic killings across Europe 7 , these crimes represent a devastating global pattern of violence against women.
For decades, the conversation around femicide has rightly centered on sociocultural factors: patriarchal norms, gender inequality, and systemic failures in protecting women. But now, a new frontier of science is emerging that challenges and complicates our understanding. Neuroscience is beginning to ask provocative questions about what drives such extreme violence at its most fundamental biological level. Are some individuals "programmed" for lethal violence by their genetics and brain chemistry? Or does biology merely "license" killing in certain social contexts?
This article explores how the new brain sciences are investigating the biological underpinnings of femicide, moving beyond nature versus nurture to examine their dangerous interplay.
The chapter "Programmed or Licensed to Kill? The New Biology of Femicide" from the book The New Brain Sciences represents one of the first systematic attempts to consider what biological research might contribute to our understanding of male violence against women 1 . This research primarily explores three interconnected areas:
Scientists are investigating specific genes that may influence violent predispositions. The MAOA gene, often dubbed the "warrior gene," has received significant attention for its role in regulating neurotransmitters linked to aggression 3 .
This biological perspective does not suggest simple determinism. Rather, it proposes that certain biological factors may create vulnerabilities that, when combined with specific environmental triggers and learned behaviors, can increase the likelihood of violence.
One of the most illuminating studies bridging biology and environment was not focused exclusively on femicide, but on the development of antisocial and violent behavior more broadly. This research provides crucial insights into the mechanisms that may underlie extreme violence.
The landmark study began by genotyping a large cohort of male children for the MAOA gene, which produces an enzyme critical for breaking down neurotransmitters like serotonin, norepinephrine, and dopamine. Low activity of the MAOA gene leads to higher levels of these neurotransmitters, which has been linked to increased aggression in animal models 3 .
Researchers then engaged in a longitudinal design, tracking these children over more than a decade. They collected comprehensive data through:
The findings were striking. The table below summarizes the core results, showing that neither genetic risk nor environmental risk alone was sufficient to predict violent outcomes:
| MAOA Gene Activity | Childhood Maltreatment | Likelihood of Antisocial/Violent Behavior |
|---|---|---|
| Low Activity | Present | Significantly Elevated |
| Low Activity | Absent | Average |
| High Activity | Present | Slightly Elevated/Average |
| High Activity | Absent | Average |
This study demonstrated a clear gene-environment interaction. The low-activity MAOA variant acted as a genetic susceptibility factor. Men with this genotype who were maltreated as children were far more likely to develop antisocial and violent behavior.
Unraveling the biology of violence requires a sophisticated array of tools. The following table details some of the essential "research reagents" and methodologies scientists use to probe the connections between brain biology and violent behavior.
| Research Tool | Primary Function in Research |
|---|---|
| Genetic Analysis Kits | Used to identify variations in specific candidate genes (e.g., MAOA, COMT) that may be associated with aggressive impulses and poor emotional regulation 3 . |
| Neuroimaging (fMRI, PET) | Allows researchers to visualize brain structure and activity in real-time. fMRI can show impaired prefrontal cortex function during impulse control tasks, while PET scans can map receptor density for neurotransmitters like serotonin 3 . |
| Immunohistochemistry | A laboratory technique that uses antibodies to detect specific proteins in brain tissue. This is crucial for post-mortem studies examining the density of serotonin receptors or other neurochemical markers in the brains of violent offenders. |
| Standardized Behavioral Assessments | Validated psychological questionnaires and diagnostic interviews are essential for consistently measuring traits like impulsivity, aggression, and lack of empathy across different study populations, linking them to biological data. |
| Cell Cultures & Animal Models | Used to study the fundamental mechanisms of gene expression and neural circuitry underlying aggression. While not directly translatable to human femicide, they provide a controlled environment for testing hypotheses about brain function. |
While the biological research is compelling, it is fraught with limitations and ethical perils. Neuroscience can identify correlations, but it struggles with causation and cannot predict individual behavior. The greatest risk is that biological explanations could be misused to absolve perpetrators of responsibility or pathologize what is fundamentally a social and political problem.
A critical insight from the social sciences is that high rates of non-lethal violence against women do not always linearly correspond to rates of femicide 5 . An Australian study found that more than half of male perpetrators of intimate partner femicide did not report any physical or sexual violence in the year prior to the killing 5 .
This suggests that while a history of intimate partner violence is a major risk factor, the escalation to lethality may follow its own complex logic, sometimes bypassing documented patterns of prior abuse altogether.
Furthermore, global data collection on femicide is plagued by inconsistency. As noted in a 2025 analysis, "45% of female homicides globally lack contextual information" needed to classify them as femicides, such as the victim-perpetrator relationship or a history of harassment 8 .
Without this crucial data, building accurate biological models is nearly impossible, as researchers cannot clearly distinguish femicides from other homicides. This underscores that biology does not operate in a vacuum; it is activated and shaped by a social context of gender inequality, harmful norms, and insufficient legal protections.
The question "Programmed or licensed to kill?" may be framing the issue too narrowly. The new brain sciences suggest a more complex reality: biological factors can create vulnerabilities, while social and personal experiences can trigger and shape those vulnerabilities into violent actions. We are neither purely programmed by our biology nor simply licensed by our environment, but exist in a constant and dynamic interaction between the two.
The promise of this research lies not in exculpation, but in improved prevention. Understanding the neurobiological pathways of extreme aggression could lead to better risk assessment tools and more effective interventions for individuals showing early warning signs.
However, this knowledge must be integrated with robust social policies that confront the root causes of gender-based violence. As nations like the United Kingdom have demonstrated, systematic reviews of domestic homicides to identify missed signals and improve inter-agency cooperation are among the most effective strategies 7 .
Ultimately, the new biology of femicide challenges us to hold two truths simultaneously: that the killing of women is a profound social injustice rooted in gender inequality, and that the human brain is a physical organ whose workings can influence behavior.
Navigating these truths with scientific rigor and ethical caution is essential if we are to ever halt the relentless toll of femicide worldwide.