by Suruthi Bala
Because it was then and there that we’ll find a Dutch woman who believed that there was something very wrong with five men in her family. A quick snapshot of what she was dealing with: one man was a serial arsonist, another had tried to run his boss over with his car, another had attempted to rape his own sister at knifepoint. Only one of the five had completed primary school and all of them had an IQ score lower than 85.
The Dutch woman sought out a clinical geneticist at the University Hospital in Nijmegen—Professor Han Brunner—and begged him to help her. She explained to Brunner that she felt the men in her family had some sort of hereditary issue that caused low intelligence and a propensity for extreme violence. And she hadn’t been the first in her family to spot this pattern. Decades before, the woman’s grand uncle had made a family tree and found even more men in the family that displayed these same traits, going as far back as the 1800s. This grand uncle was sure that there had to be some sort of genetic component that was causing his family’s male violence problem; it couldn’t be coincidence.
As it turned out, this woman and her grand uncle were right. In 1993 Han Brunner worked out what was going on: all of the violent men had a defunct variant of a gene called MAOA. It was an enormous discovery, as it was the first time that a specific gene had been linked to a human behavior like aggression.
So what was going on? Well, get ready, because we’re about to take you on a magic school bus journey of science, junk science, and everything in between.
Genes are sections of DNA that provide instructions to make specific enzymes. MAOA is a gene that encodes the enzyme monoamine oxidase A. This enzyme breaks down the neurotransmitters (the brain’s signaling molecules) serotonin, noradrenaline, and dopamine. If these neurotransmitters aren’t degraded and removed when we’re done with them, their buildup in the brain can lead to abnormal behavior and possibly aggression.
Naturally, the gene MAOA comes in several different forms, depending on the various levels of activity of the enzyme it regulates, monoamine oxidase A. Brunner’s study found the males in that Dutch family had a variant of the MAOA gene that was completely inactive, so they had higher levels of noradrenaline, dopamine, and serotonin floating around their brains. Brunner theorized that the buildup of these molecules in the men’s brains may have resulted “in over-excitation of the nerves in stressful situations,” leading to their observably aggressive and hypersexual behavior. Brunner named this extremely rare condition Brunner’s syndrome, and it’s so rare, in fact, that this defunct, totally inactive variant of the MAOA gene has not been found outside of the men in that one Dutch family.
Another, and much more common, variant of the MAOA gene is MAOA-L (L for low activity), and this version leads to less monoamine oxidase A being produced. It’s important to note that it’s not a situation where none of the enzyme is being produced (like with Brunner’s boys), just less than usual. And so those excess neurotransmitters like dopamine hang around in the brain for too long, but they are eventually removed, just at a slower rate.
And it is this variant—MAOA-L—that we are going to focus on now, because it is this version that went on to be dubbed the “warrior gene.” (Why didn’t the variant that the incredibly violent Dutch men had become known as the warrior gene, you ask? Well, again, because that variant so far has only been found in that one family. So to say it’s rare would be a massive understatement.)
After Brunner’s work suggested a link between the totally inactive MAOA gene and aggression, studies started rolling in on MAOA-L, and the hypothesis was that if a gene that produced none of this enzyme had been linked to such a strong tendency for aggression, then surely people with the less active variant must have at least a considerable propensity toward aggression.
No doubt some of these studies formed the basis of Bradley Waldroup’s defense. It led to jurors convicting him of voluntary manslaughter rather than first-degree murder. When asked why they had voted the way they had, one juror told NPR, “A bad gene is a bad gene.”
MAOA: No Way
So what does the science behind the controversial warrior gene actually look like? Well, a 2006 study—“Elevated Monoamine Oxidase A Levels in the Brain: An Explanation for the Monoamine Imbalance of Major Depression”—found that males with the MAOA-L variant had differences in their brain structure and function that could predispose them to aggression, specifically to snap while under pressure.
Research in this study focused on the brain structure in people with no history of criminality, violence, or childhood abuse. Brain scans revealed that those in the group with the MAOA-L variant were more likely to have smaller limbic systems than their non-MAOA-L study buddies. (The limbic system is a part of the brain that supports a variety of functions, including emotion, behavior, and long-term memory.) Researchers also found that there were some differences in brain activity; when the people with the MAOA-L variant were shown scary or threatening images, their amygdalas (the brain’s emotional center that we’ll meet in more detail later in this chapter) appeared to overreact. In particular, the males with the warrior gene were less able to inhibit their responses (i.e., they would physically respond).
OK, so this study was able to show brain differences in most people with the MAOA-L variant, but how do those differences actually manifest themselves? As super-hyper-aggression like the Brunner boys’? Well, not exactly.
For a start, roughly 40 percent of the general population has the MAOA-L variant! We think we can safely say that 40 percent of us aren’t walking around bashing people’s heads in, unable to control ourselves. (Or shooting our wives and their friends…)
In fact, in this study, it was found that 38 percent of the group had the warrior gene, yet none of those people had a history of criminality or violence. Remember, researchers specifically chose a group that was squeaky clean.
Now, it is worth mentioning that the scientists behind this study did state that the presence of the MAOA-L gene alone is not enough to predict violence, and that another trigger is needed. And of course, a typical trigger is having had an abusive childhood. So maybe one could argue that since the study had also chosen people who had no history of child abuse, that’s why none of the subjects with the MAOA-L variant showed criminal tendencies or aggression.
Still with us? This brings us nicely to another study. A 2002 study looked at a sample of males who had all been maltreated as children to understand why some had gone on to develop antisocial behavior, while some hadn’t. The researchers found that men with MAOA-L who had been maltreated were more likely to exhibit antisocial behavior than men with a similar background who had the normal MAOA gene. So the belief was that if a person has the MAOA-L variant and suffers an abusive childhood, they are at an increased risk of being aggressive and developing antisocial behavior.
Studies like this provided another string in the bow for Bradley Waldroup’s defense. Waldroup had a very abusive childhood, and at his trial, his defense attorney certainly drew a connection for jurors between the abuse, Waldroup’s warrior gene, and how Waldroup had exploded. In that 2010 NPR interview, one of the jurors summed up the defense’s argument in one chilling statement: “Some people without this [the MAOA-L variant] would react totally different than he would. A diagnosis is a diagnosis.”
Our jaws hit the floor when we read this. An abusive childhood in a killer’s past is not something anomalous—as we’ll see in our next chapter—and it rarely features as a significant mitigating factor at murder trials like this. Certainly not to the extent of reducing someone’s conviction from first-degree murder to manslaughter. It’s clear from the post-trial interviews that the “warrior gene plus abuse” argument was what had swayed these jurors. But as we’ll see, the science is very much not there.
In 2014, along came the biggest-ever study of its kind—“MAOA Genotype, Childhood Maltreatment, and Their Interaction in the Etiology of Adult Antisocial Behaviors”—and it found that while childhood maltreatment was a significant risk
factor for adult antisocial behavior, the MAOA-L variant had no effect!
Honestly, we could go on and on about this controversial gene and various studies, but our main point is just how common this variant is in the general population. We cannot stress this enough. And in fact, Professor Brunner himself pretty quickly distanced his work from suggestions that he had found a “gene for aggression.”
At the Ciba Foundation Symposium conference in 1995, Brunner made it clear: “The notion of an aggression gene does not make sense, and it would be wrong to suggest that any one gene or collection of genes can account for something as complex as aggressive human behavior.” He emphasized that his research has only demonstrated how a very specific genetic defect can result in a fairly specific behavioral abnormality in one particular family, not society at large.
And if you still have any lingering doubts, consider this: drugs that actually block monoamine oxidase A (the enzyme at the heart of this whole warrior gene business) have actually been used extensively to treat people with depression, and with no apparent increase in violent tendencies in those patients.
So is the warrior gene a likely predictor of violence? It doesn’t appear so. At most, what some of these studies show is that people with the MAOA-L variant are more likely to be more reactive when threatened, but that’s all. If nothing else, remember that a whopping 40 percent of people on average carry the variant, but only a tiny fraction of these carriers end up committing violent crimes. Most people with the warrior gene seem to make it through each day without totally fucking losing it and murdering another person. So to call these alleles “a gene for violence” is not just a massive exaggeration, it’s just plain wrong. Genetics is a probabilistic science, and to say that one variant of a gene is responsible for the hugely complex human behavior of aggression and violence is a bit of a nonstarter.
The best we can say is that perhaps in some combination with other genetic and environmental factors, the warrior gene might impact one’s ability to control any violent urges. But these factors most certainly do not predetermine a life of crime. And they absolutely do not remove criminal responsibility. The key takeaway is that no singular gene can determine criminality, violence, or murder-y desires. And as many scientists pointed out in the wake of Bradley Waldroup’s trial, the notion that sentencing decisions should be made on the basis of such uncertainty is deeply, deeply troubling.
Waldroup, in our opinion, knew full well what he was doing. As we said, the MAOA-L variant is at most linked to increasing the likelihood of someone snapping, but Waldroup carried out a sustained attack that left one woman dead, one woman brutalized, and four children traumatized.
In 2010, a judge in Italy reduced the sentence of a man in jail for murder after it was found that he had the MAOA-L gene. Again, the scientific community was horrified, but if these sort of defense arguments continue to work, undoubtedly they will become increasingly common in our courtrooms—all the more reason to be careful before attributing complex behaviors to a single gene.
So now that we’ve shown you that the warrior gene doesn’t really stand up to close scrutiny in terms of making a killer tick, let’s go beyond aggression. Because to be honest, there are many other traits that make a “good” if not “better” killer: being unempathetic, manipulative, callous, charming, ruthless—sound familiar?
It’s time to take a look at the personality disorder we all most readily associate with criminality and murder—psychopathy.
Maybe They’re Born with It, Maybe It’s Antisocial Personality Disorder
The whole contentious issue of the role genetics play in providing a predisposition for criminality takes a rather different turn when we consider psychopathy.
Over the last 20 years, in large part due to the work of Dr. Robert Hare, there has been a total shift in clinical circles from the idea that psychopaths are created by severe childhood trauma and abuse to the idea that psychopathy is mainly genetic. It is now generally agreed that psychopathy is a congenital state (i.e., you’re born with it).
We know this because children start to show the signs of psychopathy from a very young age, and the traits tend to stay pretty stable throughout their lives. We’ll go on to discuss the psychopathic child in more detail in chapter 2, but what is clear from Dr. Hare’s research (like his 1993 study, “Psychopathy, Mental Disorder, and Crime”) is that children with psychopathic traits are “inexplicably different” from other children—displaying aggression, manipulation, and deceitfulness from the very start.
Dr. Hare also states in his book Without Conscience: The Disturbing World of the Psychopaths Among Us that most of the psychopathic people he has worked with over the years did not report coming from abusive homes; in fact, the majority had grown up in relatively “normal” households with caring and supportive parents.
And so, given these findings, researchers went in search of genetic reasons to explain psychopathy. Although it is still not exactly clear how it is passed on, psychopathy is actually now considered to be the personality disorder with the highest genetic component. Studies like the 2014 paper “The Heritability of Psychopathic Personality in 14- to 15-Year-Old Twins” suggest that psychopathy is around 50 percent heritable, while the “Minnesota Twin Study” has shown that psychopathy is 60 percent heritable. There isn’t an exact agreed upon figure, as you can see, but the general consensus is that psychopathic traits have a stronger relationship to one’s DNA than to one’s upbringing.
The key difference here is that no one is claiming—like with the warrior gene—that there is one singular gene for psychopathy. This would be massively wrong. There are likely a variety of genes, working in combination with differing brain structures, that correlate with psychopathic tendencies or behaviors.
We’ll come back to what the brain structure of a psychopath looks like later in this chapter, but for now, let’s talk about what exactly psychopathy is and how it’s diagnosed.
Psychopaths and Where to Find Them
The word psychopath gets bandied about a lot these days, especially by the unqualified (said the true crime podcasters). But are we using the term correctly? It has become so much a part of our lingua franca that a roommate leaving their dirty dishes in the sink overnight could earn themselves the title far too easily. Or, how many times have you dissected the behavior of your friend’s “psycho” ex? We’re all guilty of it, but as usual, most of us don’t know what the hell we’re talking about.
Psychopathy is possibly the most well-known but least understood personality disorder out there, so let’s get into it…
We tend to use psychopathy and antisocial personality disorder (ASPD) interchangeably, but the best way to think about it is as psychopathy being a subset of ASPD. So what is antisocial personality disorder? ASPD is a Cluster B personality disorder, which means that it belongs to the erratic personality disorder family. Cluster B is also home to borderline personality disorder, histrionic personality disorder, and narcissistic personality disorder (more on these in chapters 5 and 6).
ASPD is a diagnosable condition, as it is listed in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), and it is thought to affect about 3 percent of the general population and around 80 percent of incarcerated populations. There are seven criteria, three of which must be met for a diagnosis: violating social norms; deceitfulness; impulsivity; irritability; irresponsibility; manipulative; and lack of remorse.
Psychopathy, on the other hand, is not a mental disorder, and as such it can’t really be diagnosed. Psychopathy can be thought of as a construct, typified by a lack of empathy and callous behavior. And while ASPD is categorical (i.e., you have it or you don’t), psychopathy is generally considered to be on a spectrum.
And what about sociopathy? Another term we tend to mix into this confusing soup of disorders. Well, sociopaths are generally considered to be created through abuse and trauma, unlike the genetic psychopath, and while m
any of us confuse the two terms given some similar behaviors—such as a lack of empathy, dishonesty, and shallow emotions—they are two very different constructs. Not just in terms of how they are formed in a person, but also because the sociopath, unlike the psychopath, is actually highly emotional (when it comes to negative emotions like rage) and likely to be very reckless. The best way to differentiate the two is to think of a cold, calculated, in control psychopath versus a hot-headed, volatile, impulsive sociopath.
Now that we’ve cleared that up, let’s get back to psychopathy, and the specific traits that psychopaths display. Psychopaths are considered the most extreme citizens of the Antisocial Personality kingdom. They are usually charming, narcissistic, superficial, impulsive, callous, unemotional, and—like mean girls in high schools the world over—they have no problem throwing others under the bus to get what they want. Their only goal is the pursuit of pleasure, which, according to Lucy Foulkes in her study “Inverted Social Reward: Associations between Psychopathic Traits and Self Report and Experimental Measures of Social Reward,” can be gained by hurting others, engaging in antisocial behavior, and being coercive and nasty.
That being said, despite what the Bateses and Batemans of Hollywood want you to believe, psychopaths do have feelings. They can feel excited or even happy, although the stakes have to be much higher than they would for a “normal” person. Crucially, guilt, anxiety, empathy, and remorse do not make an appearance. According to Dr. Hare, a forerunner of the psychopathic research space, these “intraspecies predators” are not much fun to be around. Although they may understand the emotions of others, psychopaths don’t tend to feel bad about any harm they cause. A guilt-free life may sound great, especially to the fallen Catholics among us, but having a psychopathic brain is by no means a one-way ticket to easy street.
