Many people think of violence and aggression as natural, biological aspects of being a man. But science paints a different picture about the origins of male aggression.
The mass shooting in Orlando was one of the most lethal mass shootings in American history, killing 49 people and injuring an additional 53. In the weeks that followed, our social media feeds were filled with #prayforpulse posts, calls for gun control, and analyses of our current institutionalized culture of homophobia. Some fixated on the fact that the shooter was Muslim and others spoke to the fact that the target was the queer community. What people talked less about was that the shooter – like 98% of all mass shooters – was a man.
When the headlines began filtering into my Facebook feed, I tried to scroll past, distance myself from the hurt and grief of yet another American tragedy. But as I tried to go on with my day, I felt my heartbeat and breath caught in a stranglehold. I was overwhelmed at the litany of seemingly endless violence perpetrated by American men. Surely, if all the shooters had been Asian American or undocumented, the airwaves would have been filled with conversations about the ‘violent culture’ harbored within those communities. But when the shooters are men we shrug our shoulders at the expected. We believe that violence in men is natural, inevitable, biological.
These beliefs are rooted in the evolutionary origin stories that we tell ourselves. Men were the hunters and protectors of our species evolved to be more aggressive than women, who were the nurturing caretakers. Sex differences materialize through hormones, diffusing through our bodies and gendering everything they come in contact with. In this narrative, testosterone not only augments external physical characteristics, but also affects the organization of the brain and thus our gender expression. Testosterone = masculinity and estrogen = femininity.
Or at least this is the narrative that has permeated the cultural mainstream. But what does science have to say about this nature vs. nurture debate?
The “Bioessence of Masculinity”
Studies trying to link aggression and testosterone have been as numerous as they have been inconclusive. When people are separated into high- and low- aggression groups, there are no consistent differences in testosterone . Tracking changes in boys undergoing puberty – during which testosterone levels increase 20 – 100 times – do not show corresponding increases in aggression . And men who have hypogonadism, or lower sex hormone activity, do not report significant increases in aggression after testosterone replacement therapy . The evidence correlating testosterone with aggression simply isn’t there. So why do we keep acting like it is?
“The research on aggression doesn’t link to testosterone, much less reliably, and people just ignore that,” says Dr. Sari Van Anders, a neuroscientist at University of Michigan. Van Anders, who is also the founder of feminist science blog Gap Junction Science, points out that many people characterize testosterone as “the bioessence of masculinity.” While testosterone is responsible for the development of male-typical physical features such as penis formation, facial hair growth, and voice deepening, it should not be conflated with social and cultural manifestations of masculinity. Further, because masculinity itself is not fixed, it is simply not possible for testosterone to account for the ways masculinity changes over time and place.
Van Anders argues that even characterizing testosterone as a strictly ‘male hormone’ is problematic. Testosterone is present in men, women, and gender nonbinary folks, and has the same effects within the body regardless of sex assigned at birth or gender. For example, women also experience facial hair growth as a result of testosterone (hence lip waxes!). “Saying that testosterone is a male hormone is like saying height is a male metric. Just because men are taller on average doesn’t mean that inches are male.” Because of these gender biases, very little work has been done on testosterone and aggression in women, maintaining a vicious cycle of ignorance around the contributions of hormones to gender differences.
So what causes aggression?
When researchers try to pinpoint the biological basis of aggression, a much messier picture emerges. Several brain areas and neurotransmitter systems appear to be implicated including the limbic systems, higher cortical structures, and serotonin systems. Part of the challenge of identifying a single biological origin may be that our notions of what constitutes as aggression are also gendered. “If you think of aggression as a social construct that is also socially situated, that means it’s not just one thing. And that means the way it plays out is going to differ over time and place.” Indeed, while boys tend to express aggression through physical confrontation, girls prefer indirect types of aggression such as verbal or social aggression.
Although we tend to default to biological explanations, social norms are often just as effective at explaining sex differences. The moment we are assigned sex at birth, sometimes even as early as in the womb, boys and girls undergo radically different gender socialization processes. Boys are encouraged to rough house and may be taunted if they don’t display aggressive behavior. Even in instances where aggression is not actively encouraged, it is not met with the same level of scorn as if it had been expressed in girls (see: Lochtegate). As the saying goes, “boys will be boys.”
While this gender socialization process looks very different depending on the cultural context, in the United States it can often take the form of toxic masculinity. Toxic masculinity is a narrow understanding of manhood defined by violence, aggression, and sex status. Men are shamed for any displays of emotion that are not anger and denied intimacy and social support networks that are deemed feminine. Under this constant threat of emasculation, violence is seen as a legitimate means to reclaim one’s manhood. Although I had found Mateen’s actions unfathomable, they made perfect sense within the lethal logic of toxic masculinity.
“People think of social constructions as malleable and biology as fixed, which is weird because you can change your testosterone. You can change your serotonin. There are all sorts of things that are easily changed about our bodies. Much more easily than poverty or racism. But still the idea that masculinity is inherent and biological normalizes it and puts it out of bounds.”
Admitting male violence is the product of our patriarchal culture rather than the action of a magic gender molecule both means that it is in our power to change it and that we have the responsibility to do so. Preventing the next mass shooting means not just fighting for tougher gun regulation, but also creating and modeling new healthier masculinities. It means critically confronting the ways that toxic masculinity is perpetuated in our media and our interpersonal relationships. It means having tough conversations with our friends and loved ones, and fostering empathy in our boys and young men . And it means that we must take on this work, not just as a radical deconstruction of gender norms or as a valiant act of feminism, but because to not do so would be to continue to poison the minds of our boys and young men – and put more lives at risk.
 Albert D, Walsh M, Jonik R. Aggression in Humans: What Is Its Biological Foundation? Neuroscience and Biobehavioral Reviews. 1993; 17:405-425.
 Sussman E, Inoff-Germain G, Loriaux D, Cutler G, Chrousos, G. Hormones, emotional dispositions, and aggressive attributes in young adolescents. Child. Dev. 1987; 58:1114-1123
 Bahrke M, Yesalis C, Wright J. Psychological and behavioral effects of endogenous testosterone levels and anabolic-androgenic steroids among males. A review. Sports med. 1990; 10:303-337.
 Check out The Good Men Project for resources for men and this Romper article for feminist parenting tips