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Key points
- Behavior has a basis in biology.
- The expression of our behaviors is a complex interaction between genetics and experience.
- Performance under stress is related to dopamine regulation, which is linked to a certain genotype.
- The relative amount of worrying or warrior-ing we express is related to what we practice, train, and do.
Humans exist on a continuum no matter the measure. Functional capacity across domains is a product of what we have in our genes and what we do in our jeans. How much of what is in our DNA defines our behavior and how much of our behavior is because of what we experience?
Research focused on family units suggests that the likelihood of participating in exercise has a component of heritability. Environmental factors (like nutrition) play a huge role. The interaction among the environment (what happens to you and what you choose to do), heredity (what your genes may predispose you to), and how you perform athletically is complex and difficult to unravel.
There’s really no true dominance of either nature or nurture because genetics, environment, and exercise all affect one another. This is immensely useful for our functional capacity but makes it difficult when trying to define relative contributions. Also, genetic influences can be very specific and may be revealed only in certain specific situations. For example, if someone has an inherent capacity to respond to strength-training exercise, it may be only for a specific type of exercise.
Gene expression for a given trait involves mutations in the gene pairs. Changes in one allele may lead to the expression of a certain phenotype. It is important to realize that this means the gene may, but not necessarily will, be expressed.
Dopamine, warriors, and worriers
Things are even more difficult to unravel when we enter the psychological domain of cognition and function under stress. This brings us to dopamine, warriors, and worriers. Aggression levels are modulated by dopamine in the prefrontal cortex. In this context, this means behaviors that start, continue, and finish competitive, aggressive acts. Fighting is the main example here.
In many animals, competitive aggression is tightly related to dopamine metabolism and the expression of receptors. A key regulator of dopamine metabolism is the enzyme catechol-O-methyltransferase (COMT) and different expression of allele status produces differential function in dopamine modulation.
A study of the warrior/worrier model and its genetic expression
The outcome of this is diminished or enhanced emotional and cognitive capacity under conditions of stress (as in aggressive scenarios). Hand-to-hand fighting is an incredibly stressful activity. The “warrior/worrier” model and genetic expression that underlies it has been examined in mixed martial arts fighters by Jaime Tartar and colleagues at Nova Southeastern University in Florida. Their paper, “The Warrior COMT Val/Met Genotype Occurs in Greater Frequencies in Mixed Martial Arts Fighters Relative to Controls” was recently published in the Journal of Sports Science and Medicine.
Tartar and her colleagues Dominick Cabrera, Sarah Knafo, Julius Thomas, Jose Antonio, and Corey Peacock wanted to know if genetic differences in dopamine levels were associated with combat sport athletic activity. They measured a number of stress response biomarkers (like cortisol) and did genotyping in 21 professional MMA fighters (who competed in Ultimate Fighting Championship, One Championship, or Bellator), 21 athletic controls, and 41 non-athletes.
The main result is very clear: MMA fighters have a significantly increased probability to carry the allele type associated with the “warrior” mindset. The suggestion is that those with the “Warrior” genotype would “have an advantage in combat sports where they would need to perform aggressively under high-stress conditions."
Interestingly, there was almost a stepwise difference in the other groups with non-athletes showing the lowest likelihood and athletes in between. Unfortunately, this work was conducted solely in male athletes due to an insufficient number of female fighters that could be recruited to participate. Tatar did tell me that hopefully, future work will test similar ideas in women and that a related study in female soccer players has been completed.
Regardless, the study by Tartar and colleagues is an important first step towards an improved understanding of human psychological function under extreme stress. Future work expanding populations and looking at epigenetic alterations is anticipated.
A limitation of genotyping
An important limitation of this kind of approach is that genotyping doesn’t necessarily mean functional expression or performance benefit. That is, as the authors acknowledge, it remains to be seen if there is a relationship between genotype and win/loss record of professional MMA fighters. This is something that this group plans on doing and would also help address the larger issue of “nature/nurture” interactions.
Successful MMA fighters may possess a well-endowed genetic potential at birth, but to realize that potential requires years and years of training. Most traits are a complex mixture of many different genes and interactions with the environment. Height is a good example, as there is no single gene coding for it. Instead, diet and genetics play strong roles together.
This leads to a significant issue: the relative interaction between genetics and environmental conditions in determining the expression of the phenotype. Humans can adapt to a range of conditions, but many factors beyond genetics have an important effect. There is variation, then, in the responses and adaptations that a person might have, and the genetic influences may not be the dominant factor. That means that the genetic effects will only be revealed, expressed, or maximized in certain specific situations.
Of course, we all exist on a continuum, not a dichotomy. You really aren't exclusively a warrior or a worrier. You're instead perhaps a warrior who worries a bit or a worrier who can warrior when needed. The bottom line is that regardless of the predisposition to be a warrior or a worrier that you carry in your genes, what you do in your jeans can make all the difference.
© E. Paul Zehr (2021)
