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Julia Shaw Ph.D.
Julia Shaw Ph.D.

Why Are We Not Outraged That Prisons Are Filled With Men?

We urgently need to do something about the number of men society imprisons.

There’s something pernicious about incarceration that has only recently become apparent to me, and I worry that I never noticed it before: Why are our prisons filled almost entirely with men? And why does no one talk about this?

Prison has always been an almost entirely male structure. It’s hard. It’s cold. It’s unempathetic. It’s punitive. Practically every descriptor we use for prison prides itself in its masculinity.

Julia Shaw
My testosterone made me do it.
Source: Julia Shaw

We have so little faith in men that we go to great lengths to keep them away from society. We physically and socially remove them from any semblance of a normal life, in the name of our safety and their punishment. We feel that they cannot learn if we don’t socially beat their tendencies out of them, often while failing to engage with them in a psychologically sensible way that might actually help their reintegration.

This also means that the adverse consequences of prison disproportionately affect men. The lack of security and funding, and the related issues of riots and overcrowding. Voter disenfranchisement and the problems that come with having a criminal record. Our dehumanizing attitudes and behaviors towards people we label, in a blanket manner, offenders.

What leads us to blindly accept that our prisons are full of men? I think it's because we accept as dogma that men are naturally more criminal—particularly more violent—than women, thus they deserve to be incarcerated at higher rates. It's about time we question this assumption.

Over 90 Percent of Prisoners Are Male

As a reasonable person, you are probably thinking that there are more men in prison because more men commit crimes. And you are correct. You may also intuit or know that most violent crime is committed by men, and such crime is more likely to result in incarceration than other kinds of crime. Also correct. But many of us accept these as truisms rather than discussion points.

Let me put this into perspective: According to the World Prison Brief, 2.1 million people were incarcerated in the U.S. in 2018. In the UK, it was 83,000, and in Canada, it was 41,000.

How many of these were women? In the U.S. it was 9.8 percent, in the UK 4.6 percent, and in Canada 5.6 percent. Sure, female percentages are on the rise—in these three comparable countries, percentages have gone up over the past few decades. But the disproportionate number is still astronomical—in each of these countries, over 90 percent of inmates in 2018 were male. Similar patterns can be seen in much of the world.

Taking it a step further, it’s not just the perpetrators who are male. Victims of violent crime around the world are also disproportionately male. According to the United Nations Office on Drugs and Crime Global Study on Homicide in 2013, an astonishing 95 percent of homicide perpetrators and 79 percent of homicide victims were male.

The Testosterone Myth

We should not just be asking ourselves why men are more violent, but why women are less violent. For one, it’s probably not because of testosterone.

Testosterone has been a scientific scapegoat since it was discovered by a mad scientist. If you have no idea what I’m talking about, let me enlighten you with an excerpt from my new book, Evil: The Science Behind Humanity’s Dark Side:

I want to share with you the curious origin of the notion that testosterone and aggression are linked at all. It all started in 1849, with a German doctor, six cockerels, and a four-and-a-half-page research paper.[i]

Here’s what happened. On 2 August 1848, Arnold Berthold thought it was a good idea to cut off the testes of six male chickens to see what happened. For two cockerels (cock A in the image), he detached one of the testes and left it loosely bobbing about next to the still-attached one. He then removed both testes from the four other cocks. For two of these cocks, who we shall call Christian and Frederick, Berthold did something absolutely crazy. He surgically inserted Christian’s testis into Frederick’s intestines (cock C). Similarly, Christian got Frederick’s testis inserted into him. Ah, medicine in the 1800s!

According to his original paper,[ii] Berthold found that the two cockerels who had had their testes removed entirely (cock B) were ‘not aggressive’ and ‘fought with other cockerels rarely and then in a half-hearted manner’. The four other cockerels exhibited normal behavior—‘they crowed lustily’ and ‘often engaged in battle with each other and with other cockerels.’ He also found that the testes placed within the intestines of Christian and Frederick had attached themselves to the intestinal tissue.

Julia Shaw
Testosterone cocks
Source: Julia Shaw

The doctor speculated that this must mean that something in the testes was absorbed by the blood and transferred to other parts of the body, causing aggression. Later this substance became known as testosterone. This innocuous paper would go on to become the foundation of modern endocrinology (the study of the system that controls hormones). It would also go on to revolutionize how we think about aggression in males, and the role of hormones in human violence.

Seems pretty simple. Add testosterone, get more aggression. Remove testosterone, get less aggression. However, this notion has been repeatedly challenged, most recently by a review of the research in 2017 by Justin Carré and colleagues.[iii] They found that ‘the relationship between testosterone and aggressive behavior is much more complex than previously thought.’

After reviewing studies in humans and animals, in and out of the lab, they concluded that ‘despite evidence linking testosterone to human aggression and/or dominance behaviors, these relationships are either weak or inconsistent.’ So, the apparent truism that males are more violent and aggressive because of their testosterone levels may actually be overblown.

Indeed, research shows that testosterone is associated with risk-taking and competitiveness, which are indirectly related to aggression. But on a more fundamental level, we cannot blame this widely spread and important hormone for violence—to do so would be to assume that men have no capacity for self-control. It also seems to ignore that women, too, have testosterone.

Luckily we are all born with a prefrontal cortex that allows us to inhibit our basal instincts. Instead, I think it’s not their hormones that make men more violent, it’s their socialization.

Toxic Masculinity

Unfortunately, men are explicitly and implicitly taught by society that they don’t need to inhibit themselves when it comes to aggression. From when they are little, many boys are taught the harmful narrative that aggression and violence are just part of being a man. Pride, in particular, is deemed a masculine achievement, and violence as a means of defending it is often glamorized.

Whenever people say that "boys will be boys," that sexist comments are just locker-room talk, or that men are just naturally more violent than women, we need to stop them. They are hurting not just women but also men.

It is irresponsible to socialize our boys thinking that they don’t need to control themselves, that they can hurt each other without consequence, that it’s uncool to act in a respectful and calm manner towards others. Most girls are told this from the moment we are born: Be cautious, be empathetic, be kind. My intent is not to paint women as angels and men as demons, but to encourage all of us to take more responsibility. We must be careful not to facilitate violence by misguidedly thinking it is simply part of the masculine experience.

The fact that we feel we have to put so many men in cages to keep us safe is the symptom of a diseased society. We are failing our men, and we urgently need to do something about it. Only when we teach and reinforce empathy, understanding, and self-control as desirable male traits can we begin to stop having to put men in prison.


[i] Berthold, A. A. ‘Transplantation der Hoden [Transplantation of the testes]’. Archiv für Anatomie, Physiologie und Wissenschaftliche Medicin, 16 (1849), pp. 42–6.

[ii] Berthold, A. A., & Quiring, D. P. ‘The transplantation of testes’. Bulletin of the History of Medicine, 16 (1944), p. 399.

[iii] Carré, J. M., Ruddick, E. L., Moreau, B. J., & Bird, B. M. ‘Testosterone and human aggression’. In: The Wiley Handbook of Violence and Aggression, Peter Sturmey (ed.), Hoboken, NJ: Wiley-Blackwell, 2017.

About the Author
Julia Shaw Ph.D.

Julia Shaw, Ph.D., is a professor at University College London. She is best known for her work in the areas of false memory and criminal psychology.