Making a Murderer: Evolution at Its Finest?

Some months ago, a blog prompt caught my interest. Jim Fallon’s TED Talk considers a little contemplated notion: what if there were a gene connecting serial killers to their crimes? As it turns out, there just might be.

The MAOA gene is responsible for producing monoamine oxidase A, an enzyme which degrades neurotransmitters in the brain such as norepinephrine, epinephrine, and dopamine. These are crucial to regulating our moods and their subsequent actions. MAOA genes come in five “flavors,” or differing levels of activity; however, for my purpose, it’ll be simplified into either “high” or “low” rates of enzymatic activity, denoted by the suffix “-H” and “-L.”

A handful of research studies have shown a correlation between the presence of MAOA-L and rash, aggressive behavior–probably due to lower concentrations of MAOA resulting in a surplus of the aforementioned neurotransmitters since there’s less enzyme to decay them.

For example, a study conducted by Brown University linked MAOA-L to higher rates of aggressive behavior in response to an irritating stimulus. The study involved 78 college age males who completed a task, received payment, and had a certain amount of money subtracted from their account by an unseen opponent. The participants could then choose to punish their opponent by making them eat hot sauce. Students possessing MAOA-L were more likely to exact their revenge than those coded for MAOA-H, especially when large amounts of money were taken. Researchers posit this demonstrates a linkage between our genetic and evolutionary history, citing “altruistic punishment”–the evolutionary psychology theory stating some of us evolved to punish deviant members of our social groups for the benefit of the larger sum.

Evolution appears once more in a study summarizing the occurrence of MAOA-L genes in different ethnic populations. Interestingly, MAOA-L appears to be more common in populations with a history of warfare. For instance, 56% of Maori men possess the gene. The Maori are a people who in the past fought amongst one another in competition for the Polynesian islands’ limited natural resources. Consequentially, it makes sense a high percentage of successful lineages would bear the genes which made their ancestors victorious in war. Due to this, the MAOA gene is often dubbed the “warrior gene.” Still, it’s important to regard the other numbers recounted. The MAOA-L gene is common to 34% of European men, 56% of Chinese men, 58% of African American men, and 61% of Taiwanese men.

I’d be interested in knowing the percentages of African men to determine whether or not the frequency in African Americans is because of pressures in the U.S., if the trait is older, or if it’s a combination of the two. Additionally, I’d love to research the history of these ethnicities to determine whether high percentages coincide with historical events or not since another source claims the gene to be prevalent in 1/3 of the “Western world” and 2/3 in less developed regions. Although genotypic changes probably take multiple generations to stabilize, I doubt it’s a linear trend.

Now, does all of this mean the mere possession of the MAOA gene outright determines a person will become a murdering machine? Well, for one, despite the gene being relatively common in the population 30-50% of us don’t commit violent crime. This brings us back to Jim Fallon’s TED Talk and his claim of environment having a great influence on the individual a la epigenetics. Alondra Oubre’s article agrees, saying child abuse during the ages of 1-5 years of age especially increase the risk of a MAOA-L gene carrier developing antisocial characteristics which could lead to violent crime. Moreover, a Finnish study recounted by Dr. Emily Deans for Psychology Today brings up it may not be the MAOA-L gene alone causing individuals to be violent. Instead, it’s proposed a combination of high risk genes plus environmental influences  lead to violence. The study examined prison inmates who had committed over ten “seriously violent crimes,” finding a 13.45 odds ratio between low activity MAOA genes and the CDH13 gene, a gene responsible for producing an adhesive protein in the brain. It’s also linked to alcoholism, strengthening the connection between alcoholism and violent behavior.

I’d be curious to know whether or not these factors were more common back when the warrior gene presented a definite advantage to our survival and if practically everyone with dormant violent tendencies would demonstrate them.

All in all, I found this an incredibly cool topic to research. It reawakened my love for our evolutionary history as a species from a biological, anthropological, and psychological perspective and the interaction between all these aspects is something I’d love to explore more.

 

Sources:

Baum, D. (2009, January 19). Punishment by Hot Sauce “Warrior Gene” Predicts Aggressive Behavior After Provocation. Retrieved May 5, 2016, from https://news.brown.edu/articles/2009/01/hotsauce

Deans, E., Dr. (2014, October 30). A Gene for Violence? Retrieved May 5, 2016, from https://www.psychologytoday.com/blog/evolutionary-psychiatry/201410/gene-violence 

Jim Fallon: Exploring the mind of a killer [Video file]. (2009, February). Retrieved May 5, 2016, from http://www.ted.com/talks/jim_fallon_exploring_the_mind_of_a_killer

Oubre, A. (2014, July 31). The Extreme Warrior gene: A reality check. Retrieved May 5, 2016, from https://scientiasalon.wordpress.com/2014/07/31/the-extreme-warrior-gene-a-reality-check/