The "Serial Killer Gene" On Riverdale, Explained

The serial killer drama on Riverdale is hard enough to keep up with, but on Wednesday's episode, “The Dark Secret of Harvest House,” another shocker was added to the plot. Betty Cooper's (played by Lili Reinhart) sister, Polly Cooper (played by Tiera Skovbye), explains that Betty was told at a young age that she possesses something called "the serial killer gene" or monoamine oxidase A (MAOA).

"They tested the rest of us for it, and none of us have it — not even dad," Polly says. "It's just you, Betty. You have a predisposition to violence." This revelation leaves Betty perplexed, and she has trouble discerning if it's true or if her sister is just being manipulative. But, wild Riverdale plot aside, the MAOA gene is real, and some people believe it's the basis of violent behaviour. Although, it's way more complex and controversial than that.

For starters, MAOA is a gene that's responsible for breaking down molecules, specifically the neurotransmitters serotonin, epinephrine, norepinephrine, and dopamine, according to the National Institute of Health's Genetic Home Reference. You've probably heard of these neurotransmitters before, because they're in charge of regulating mood, emotion, sleep, and appetite.

When someone has a rare MAOA gene mutation, it can cause MAOA deficiency or low-activity MAOA. Without MAOA, these important neurotransmitters can build up in the brain, and make it harder for someone to control impulses. This can lead to aggressive behaviour or violent outbursts, which is one reason why MAOA is nicknamed the "warrior gene."

According to Rose McDermott, PhD, who has studied the MAOA gene, most scholars find this term pejorative and disrespectful, so they choose not to use it. "In the case of MAOA, it increases the likelihood that a person who possesses this variant will engage in physical aggression in response to provocation, when they have experienced a lot of traumatic early childhood events," she says. "But by no means is this deterministic." Interestingly, Alice Cooper (played by Mädchen Amick), Betty's mom, also tells Betty that she suffered an accident when she was a child. Given what we know about Betty's upbringing, perhaps she also dealt with trauma, too.

As the Cooper women suggest, MAOA deficiency is an inherited condition, and it tends to be more common in men. (Since the condition is considered "X-linked," and it's recessive, it's harder for women with two X chromosomes to end up with it.) Of course, genetics only tell half of the story. People might be surprised to learn that the expression of this gene is hugely affected by environmental factors, Dr. McDermott explains. "People with [low-activity] MAOA who have had a lot, or more intense, traumatic early childhood events, are much more likely to show increased rates of physical aggression later in life," she says. But even so, social behaviour manifests in very complex ways, so it's unfair to make assumptions about people simply because they have this MAOA gene.

As for the belief that people with low-activity MAOA are serial killers? Dr. McDermott isn't aware of research that suggests that's the case. "While it may be possible to find serial killers with MAOA, you cannot know that this predisposes them without also thinking about all the people with MAOA who are not serial killers," she says.

To bring this back to the bizarre world of Riverdale, there's not a ton of truth to Polly's statement that her sister carries a "serial killer gene." So, maybe this is just one part of Edgar's evil plan after all.