Genetics can have a great influence in determining whether someone grows up to become a serial killer. Various studies have identified specific genetic factors that can lead to the genesis of a serial killer; however, it is still unknown which genetic pathways beget the development of these factors. A few genes have been noted as being abnormal in serial killers; these genes include 5HTT, COMT and MAOA. Out of these 3 genes of interest, the MAOA gene has been shown to have the strongest link to psychopathic behavior, which puts someone at risk of becoming a serial killer. The MAOA gene is responsible for making an enzyme called monoamine oxidase A (Gunter, Vaughn, & Philibert, 2010). Monoamine oxidase A helps break down the neurotransmitters serotonin, epinephrine, and dopamine. These neurotransmitters help regulate mood, emotion, sleep, appetite, and they also help regulate the body’s response to stress (Chester et al., 2015).
The MAOA gene is colloquially referred to as the “warrior gene” because a certain mutation of this gene is present in many serial killers (Hunter, 2010). This gene is also located on the X chromosome, which explains why typically men are serial killers and aggressive since they only have one X chromosome. A mutated form of the MAOA gene, referred to as MAOA-L, is associated with an increased risk of violent and aggressive behavior. MAOA-L causes the body to produce less monoamine oxidase A. This deficiency of monoamine oxidase A causes serotonin and other neurotransmitters to build up in the brain (Chester et al., 2015). This surplus of neurotransmitters is believed to cause excessive impulsive behaviors and make the inhibition of strong emotional impulses more difficult. The brain becomes insensitive and tolerant to the neurotransmitters that are supposed to calm it down.
People with MAOA-L are also more likely to have a smaller hippocampus, amygdala, anterior thalamic nuclei, and limbic cortex. These brain structures are involved in emotion, behavior, and long-term memory (Hunter, 2010). Because these structures are smaller, people with MAOA-L have a more difficult time regulating their emotion and feeling empathy, which are both hallmarks of psychopathy.
The MAOA-L variant is extremely common; it occurs in about 40% of the population. However, not all people with this version of the MAOA gene become psychopathic serial killers. The expression of the mutant gene in a violent way depends on the environment one is raised in. If someone with the MAOA-L gene is raised in an environment where they are exposed to violence or trauma, their chances of committing a violent offense increases by more than 400 percent (Hunter, 2010). One study found that children with MAOA-L who were also abused or maltreated grew up to be more antisocial and violent compared to those who had the normal version of the gene (Caspi et al., 2002). With this being said, the combination of the MAOA-L gene and a rough upbringing is a dangerous one.
While possessing the MAOA-L can put you at an increased risk of becoming a psychopath, it does not mean you are destined to become a serial killer. One noteworthy example of this is Jim Fallon, a neuroscientist who discovered he had the “serial killer gene.” Fallon looked at the brains of famous serial killers and explains his findings in the TED Talk below. Basically, you can have a genetic disposition to become a serial killer, but this is not fate. Both nature and nurture factor into whether someone turns to a life of serial killing.
Works Cited:
Caspi, A., McCray, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., … Poulton, R. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851–854. https://doi.org/10.1126/science.1072290
Chester, D. S., DeWall, C. N., Derefinko, K. J., Estus, S., Peters, J. R., Lynam, D. R., & Jiang, Y. (2015). Monoamine oxidase A (MAOA) genotype predicts greater aggression through impulsive reactivity to negative affect. Behavioural Brain Research, 283, 97–101. https://doi.org/10.1016/j.bbr.2015.01.034
Gunter, T. D., Vaughn, M. G., & Philibert, R. A. (2010). Behavioral genetics in antisocial spectrum disorders and psychopathy: A review of the recent literature. Behavioral Sciences & the Law, 28(2), 148–173. https://doi.org/10.1002/bsl.923
Hunter, P. (2010), The psycho gene. EMBO reports, 11, 667-669. doi:10.1038/embor.2010.122
The Neurobiology of Becoming a Serial Killer 
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