Don't be fooled!

Mixed martial arts is an exercise in suffering. The goal is near total control of body and mind in the face of chaos, stress, and violence. Only people of a particular psychological bent are going to be able to manage it, or even want to. Could it be that people with certain neurological conditions have an advantage in reaching the right heights of emotional control--bypassing the body’s natural flight response and doubling down on the fight response? Growing research of a common parasite named Toxoplasma suggests increased aggressiveness and risk-taking among infected humans. Could this parasite have something to do with a fighter’s gameness in the cage: the essential x-factor, the eye of the tiger? Some scientists think it might.

Toxoplasmosis is the term for the infection of a protozoan called Toxoplasma gondii. Between 30 to 50% of the global human population have “Toxo,” and it is one of the CDC’s top five Neglected Parasitic Infections. Toxo can live in many different hosts but can only reproduce in the intestines of cats. Humans become infected through contact with cat feces or by eating undercooked meat. Only those with severely weakened immune systems are at risk of Toxo being fatal, and most live with it their entire lives unnoticed.

What makes the parasite so fascinating, though, is its uncanny ability to affect behavior.

“Take a Toxo-infected rodent and they’re no longer afraid of the smell of cats,” says Robert Sapolsky, a biological science professor at Stanford and a leading Toxo researcher. “In fact, they become attracted to it. The most damn amazing thing you can ever see: Toxo knows how to make cat urine smell attractive to rats. And rats go and check it out and that rat is now much more likely to wind up in the cat’s stomach. Toxo’s circle of life completed.

“But then we looked at how much winds up in different areas in the brain, and it turned out Toxo preferentially knows how to home in on the part of the brain that is all about fear and anxiety, a brain region called the amygdala … the amygdala is all about pathways of predator aversion, and Toxo knows how to get in there.”

Just when you though Toxo couldn’t get any more bizarre, scientists in the UK recently mapped out the Toxo genome and found that the parasite somehow carries the mammalian gene Tyrosine Hydroxylase--the critical enzyme for making dopamine, a neurotransmitter that helps control the brain’s pleasure center. And growing evidence suggests Toxo infection in humans is linked to more extroverted, aggressive, and risk-taking behavior.

“Many parasites have the ability to manipulate human behavior, but in terms of the behavior profile--one cluster of traits related to neuropsychological and behavioral dis-inhibition--there’s nothing else like [Toxo],” Sapolsky says. “Maybe you take a Toxo-infected human and they start having a proclivity towards doing dumbass things that we should be innately averse to, like having your body hurdle through space at high G-forces. Maybe this is the same neurobiology. This is not to say that Toxo has evolved the need to get humans into cat stomachs. It’s just sheer convergence. It’s the same nuts-and-bolts neurobiology in us and in a rodent, and does the same thing.

“On a certain level, this is a protozoan parasite that knows more about the neurobiology of anxiety and fear than 25,000 neuroscientists standing on each other’s shoulders, and this is not a rare pattern. Look at the rabies virus; rabies knows more about aggression than we do. It knows how to make you rabid. It knows how to make you want to bite someone.”

Another Stanford neuroscientist, Patrick House, was the first person to suggest that Toxo infection might have an effect on athletic performance, calling Toxo’s behavioral tampering in men a form of “inadvertent, cultural doping.”

“We know that infection increases testosterone in male brains, making them more likely to get into car accidents, more attractive to females, and more prone to being jealous, dogmatic, and dismissive of authority,” House says. “Something like a James Dean effect. Generally, males with Toxo are more aggressive and less inhibited.”

Watching the World Cup, House noticed that the countries with the highest infection rates seemed to win more. The top FIFA teams listed by infection rate are Brazil (67%), Argentina (57%), France (45%), Spain (44%), and Germany (43%). Just add Italy and that list includes every World Cup champion of the last 40 years.

UFC announcer Joe Rogan once theorized on his podcast that the same type of risk-taking behavioral modifications could be prevalent in MMA fighters. He joked that Brazil may be experiencing a long-term cultural impact as a result of its high Toxo infection rate and is now home to wild, aggressive men--and a higher percentage of great MMA fighters--as a consequence. Needless to say, he took some heat from some of his Brazilian fans:

Ever since I heard Joe talk about it, I’ve been asking everyone I know who is good at fighting if they had an outdoor cat growing up. Virtually all of them have said yes. Joe is not just picking on Brazil; he's drawing (admittedly still hypothetical) connections: A tiny parasite adept at tampering with our brain chemistry may be having a profound effect on our personalities and sparking the revolution that's made MMA the fatest-growing sport in the world.

Check out these related stories:

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The Fight of the Mind