Genes Load the Gun, But Who Pulls the Trigger?

Maks Remiszewski

Height, color of our eyes, tone of our skin, and aggression?! Do we get all that through our genes? Or is aggression formed by the environment and the way we experience life? These questions have fascinated many scientists and storytellers ever since genetics entered the public discourse. It also sparked the interest of Hollywood writers who voice their views on the topic through films such as Joker or The Dark Knight.

…from mice to humans…

Source: Johns Hopkins University at http://www.jhu.edu/news_info/news/home95/nov95/mice.html 

Research suggests that aggression might origin from both genetics and life experiences. Two important scientific studies, Cases et al. in 1995 and Caspi et al. in 2002, explored what role genes play in creating violent behavior.

Cases et al. experimented with genetically modified mice to investigate the role of a gene that produces an enzyme called monoamine oxidase A (MAOA). This enzyme helps to break down neurotransmitters like serotonin and norepinephrine, which are some of the chemicals that influence mood and behavior. In this pioneering study, a team of researchers created what they called "knockout mice" by eliminating the gene responsible for MAOA production. The results were surprising because male mice lacking the MAOA enzyme displayed extreme aggression. Their brains were full of serotonin and norepinephrine, which led to changes in their behaviour. According to the researchers, it was the imbalance of neurotransmitters caused by genetic mutations that could contribute to violent inclinations.

Building on the animal research discussed about, in 2002 another team of researchers, Caspi et al., asked themselves a question if the findings from experiments on mice can be applied to humans. They conducted a twenty-six-year-long study in New Zealand, in which they observed more than one thousand children in one area from birth to maturity. The team focused on differences between the levels of MAOA and their impact on children’s and then adults’ behavior.

Results of the study showed that not everyone with low or absent MAOA enzyme became aggressive, and that environment and life experience was a crucial element in the puzzle. Boys who had a difficult childhood and low levels of MAOA were more likely to develop unfriendly, antisocial, or even aggressive behavior. At the same time, boys with the same difficult experiences but with high MAOA expression did not show so much anger and frustration.

Ultimately, the findings show that aggression is not solely genetic, but it is also influenced by environmental factors. If a person with a genetic predisposition for low expression of the anger-regulating enzyme, grows up in a supportive environment and has positive patterns in life, they may never show violent behavior.

…from humans to stories…

As already mentioned, the idea of roots and causes of aggression is not just a topic for researchers, but it has also become relevant for directors and writers.

The Joker, a prominent character in Joker and The Dark Knight, is a tragic person who tells different stories about how he got his scars. In both films it is suggested that his violent nature may be caused by his childhood trauma. He is a person with mental health issues who suffers bullying and is abandoned by family and society. His aggression, frustration and lack of social skills shows what Caspi et al. discovered, that difficult childhood together with a certain genetic expression can lead to extreme behaviors.

What is there for us?

Both science and cinema tell us that aggression is not only in the genes, and that one’s biological predisposition must be combined with specific developmental circumstances in order to for one’s violent tendencies to emerge, just like the Joker became aggressive because of both his own experiences and (maybe) some genetical predispositions.

But it is easy to blame the genes. What if we – as a society – create a more welcoming environment not to allow them to come to play? Or would the world be a better place if we had a possibility to influence aggression by genes modification? Alternatively, maybe we should perform mass genetic tests to predict criminal or aggressive behavior?

These are questions I leave for each and every one of the readers to think about on their own.