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Warrior Gene

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Warrior Gene

We refer to the monoamine oxidase A gene when discussing the MAOA gene. It codes for the production of the enzyme MAOs (monoamine oxidases), involved in breaking down neurotransmitters in the synapses between neurones. The gene is found on the X chromosome.

Serotonin is one of the primary neurotransmitters broken down by MAOA, although dopamine and norepinephrine are also affected. Serotonin is primarily a mood stabiliser.

Many refer to the MAOA gene as the ‘Warrior Gene’ due to its ties with aggression. This is not to say that these ties are factual and proven, and we will assess the studies to determine the validity of their findings.

So, what is the warrior gene theory? Let's dive in.

How does the MAOA gene affect a person’s mood?

Neurotransmitters are fundamental in regulating moods and subsequently behaviours. As MAOs are enzymes that break down these neurotransmitters, any issues with the MAOA gene and its ability to produce these enzymes would affect a person’s mood.

If neurotransmitters are left in the synaptic cleft, it can cause many issues. The neurotransmitter effects are ultimately prolonged, resulting in continued activation of the neurons involved.

For example, acetylcholine is involved in the contraction of muscles. The muscle will continue to contract if acetylcholine is left in the synaptic cleft and is not removed (through reuptake or diffusing).

How does the MAOA gene affect aggression?

As MAOA is involved in the production of enzymes that break down neurotransmitters, issues with this gene can result in mood disorders, as seen in the case of Brunner et al. (1993):

  • In this study, 28 males in a Dutch family were investigated, as they were showing signs of abnormal behaviour and ‘borderline mental retardation, according to the study.

  • These behaviours consisted of impulsive aggression, arson, and attempted rape.

  • Researchers analysed their urine over 24-hours and found a deficiency in the enzyme activity associated with MAOA.

  • In 5 affected males, further investigation revealed a point mutation in the MAOA structural gene (specifically the eighth axon). This changed how this gene coded for the enzyme production, which caused issues with the breakdown of neurotransmitters.

  • This finding suggests that the MAOA gene mutation is linked to abnormal, aggressive behaviours.

MAOA can have various effects on aggression depending on what specific gene is dysfunctional and how it is dysfunctional. For instance, one variant of the gene, MAOA-L, is linked to low levels of MAOA. Another variant, MAOA-H, is associated with high levels. So, people with the MAOA-L variant may display high levels of aggression, whereas the MAOA-H variant may display low levels of aggression.

This is because it affects MAOA, which affects neurotransmitters and mood modulations and behaviours.

How, then, did the MAOA gene earn the nickname, the warrior gene? What is the warrior gene theory?

MAOA, the warrior gene

The MAOA ‘Warrior Gene’ has earned a lot of backlash over the years due to the unethical term and unfair generalisation it imposes on the people it originates from. The term originated in a study on rhesus monkeys, where a variation in the MAOA gene resulted in aggressive behaviours (Newman et al., 2005).

When a specific gene is associated with or labelled as the reason behind a particular abnormality, it brings severe consequences. Anyone with this gene or issues with the gene will automatically be associated with the label. Any stereotypes will be unfairly placed on them.

The MAOA Warrior Gene was reestablished in a New Zealand study by Dr Rod Lea in 2006, which stated a ‘warrior gene’ existed in the Mãori men, explaining their aggressive behaviours and lifestyles (Lea & Chambers, 2007).

Warrior Gene definition Maori StudySmarterMãori, Pixabay

Due to its location on the X chromosome, the MAO gene means that males only inherit a single copy. A particular variant of the gene, known as MAO-30bp-rpt (a 30bp repeat polymorphism, although you do not need to know this for the exam!) is associated with gene function and psychiatric disorders such as depression, anxiety, aggression, and addiction. Lea stated that negative behaviours are associated with warrior gene traits, particularly:

  • Aggressive behaviours.

  • Drinking.

  • Smoking.

  • Risk-taking behaviours.

These behaviours were able to be attributed to a genetic explanation. When genotyping 46 unrelated Mãori men, researchers found the following:

  • 56% of the Mãori men had this MAO-30bp-rpt allele, almost double that of Caucasian men analysed in a different study.

  • Further identification of different polymorphisms of the MAOA gene revealed:

    • 70% of Mãori men compared to 40% of non-Mãori men had haplotype (group of alleles on one chromosome inherited from a single parent) differences in the gene.

Lea reportedly stated to the media (Wellington: The Dominion Post, 2006):

Obviously, this means they are going to be more aggressive and violent and more likely to get involved in risk-taking behaviour like gambling.

This statement is incredibly powerful. It is ethically questionable and raises many questions, namely, is it fair to describe all men with this gene as aggressive and violent?

Lea suggested this was due to the nature of the Mãori men’s past--they had to engage in many risk-taking behaviours, such as migration and fighting for survival, which has then led to aggressive behaviours in the present, modern-day, and a genetic bottleneck. The study suggests that this is a process of natural selection, and due to the population growth that occurred afterwards, it continued to be present in Mãori men.

According to Lea, it was dubbed the Warrior Gene due to the culture of the Mãori men, as they placed significant value on their ‘warrior’ traditions and is a staple part of their culture today, despite the negative connotations of the ‘warrior gene’.

Evaluation of the genetic research on the MAOA (warrior) gene

Considering the implications of the ‘Warrior Gene’, it’s important to assess the research into the studies.

Strengths

  • Brunner et al. (1993): As mentioned above, the presence of a mutation in the MAOA gene and the subsequent violent and aggressive behaviours suggests that the MAOA gene has genetic implications leading to aggressive behaviours if defective. This suggests the gene is associated with the control of behaviours overall.

  • Caspi et al. (2002) assessed a large sample of male children from birth to adulthood.

    • The study wanted to determine the cause of some maltreated children developing antisocial behaviour, whilst other abused children did not.

    • They found the MAOA gene (a functional polymorphism in it, specifically) was important in moderating the effect of maltreatment.

    • If children had a genotype that expressed high levels of MAOA, they were less likely to develop antisocial behaviours.

    • This suggests that the MAOA gene is involved in the development of children and how they process their maltreatment. Some victims with a highly functional MAOA gene were less likely to victimise others.

    • This suggests genotypes can moderate children’s sensitivity to maltreatment and the development of aggressive behaviours.

  • Associations between the gene and behaviour moderation: As mentioned in the studies above, the MAOA gene is fundamentally linked to mood due to the need to produce enzymes that deal with neurotransmitters. If the gene is affected, it stands to reason that mood and behaviours will be affected, too.

Warrior Gene Aggression StudySmarterWarrior, Flaticon

Weaknesses

  • Aggression occurs when provoked in a lab–McDermott et al. (2009): In this study, subjects were paid to punish people they believed had taken money from them.

    • They gave them different amounts of hot sauce, varying in spiciness.

    • People with low activity MAOA genes only behaved aggressively in the lab when provoked.

    • Provocation is manipulated ‘upwards’ when aggression occurs with greater intensity. This was especially the case in low activity MAOA subjects.

    • It suggests that the MAOA gene is not explicitly tied to aggression, even in low provocation conditions, but instead, it predicts aggressive behaviours in high provocation situations.

    • This finding suggests that the environment is equally as crucial as the gene, and the MAOA gene is not a direct predictor of aggression or a gene that predetermines higher levels of aggression. It is just associated with aggression if the subject is provoked, and the interactionist approach may be a more suitable studying approach.

  • Reductionist: The suggestion that a gene is responsible for violent or aggressive behaviours reduces a human’s to a single approach. It ignores the environmental factors that may significantly influence a person’s choices and behaviours. It simplifies human nature.

  • Deterministic: If a gene controls human behaviour outright, with no room for a person’s free will or choices to decide what they want to do, it can create many issues for society. If a person is more inclined to be violent purely because they have a gene for it, is it fair to treat them similarly to everyone else? Should they be prosecuted for violent behaviour when they are helpless but follow their biological urges?

  • Merriman and Cameron (2007): In their review of the 2006 study, whilst they agree that there is an association between the genetic variant of MAOA and antisocial behaviours in Caucasians, the study has no direct evidence to suggest there is an association for Mãori men. Overall, they criticise the warrior gene study, suggesting the conclusions were based on ‘science with insufficient investigative rigour’ in applying new literature and understanding older, relevant literature.

  • Ethically questionable: The term warrior gene is ethically questionable, as it reduces a person’s nature to their genetic predispositions, ignoring other aspects of their character and their overall free will and ability to make moral choices, and has several connotations that are not fair to place on a whole race of people. It also has racial overtones.


Warrior Gene - Key takeaways

  • We refer to the monoamine oxidase A gene when talking about the MAOA gene. It codes for the production of the enzyme MAOs (monoamine oxidases), involved in breaking down neurotransmitters in the synapses between neurones.
  • Many refer to the MAOA gene as the ‘Warrior Gene’ due to its ties with aggression.
  • As MAOA is involved in producing enzymes that break down neurotransmitters, issues with this gene can result in mood disorders.
  • The Warrior Gene gained notoriety from a New Zealand study by Dr Rod Lea in 2006, which stated a ‘warrior gene’ existed in the Mãori men.
  • Overall, evidence suggests dysfunctions with the gene can lead to aggressive behaviours, as seen in the Dutch family. However, stating that aggressive behaviours are due to the gene is reductionist and deterministic. The ‘Warrior Gene’ is an unethical term that unfairly portrays the Mãori men.

Frequently Asked Questions about Warrior Gene

The warrior gene refers to monoamine oxidase A or the MAOA gene. It codes for the production of the enzyme MAOs (monoamine oxidases), involved in breaking down neurotransmitters in the synapses between neurones.

It is suggested that if a person has the ‘warrior gene’, they will be more aggressive and have aggressive traits. It would not be accurate to say they have ‘symptoms’. Lea also suggested that addiction problems (alcohol and nicotine) could be ascribed to the warrior gene.

The MAOA gene is the warrior gene, and a variant in the allele of the MAOA gene (specifically, MAOA-30bp-rpt) is supposedly the cause of the warrior gene, according to Lea in the Mãori men. Overall, the MAOA gene is linked to aggressive behaviours and can also be dubbed the warrior gene.

To a certain extent, the MAOA does exist and is linked to aggressive behaviours, especially concerning dysfunction of the gene. So, it is real, although whether it is literally ‘the warrior gene’ is up for debate and is ethically a questionable term.

Final Warrior Gene Quiz

Question

What is the MAOA gene?

Show answer

Answer

We refer to the monoamine oxidase A gene when talking about the MAOA gene.

Show question

Question

What does the MAOA gene do?

Show answer

Answer

The MAOA gene codes for producing the enzyme MAOs (monoamine oxidases), involved in breaking down neurotransmitters in the synapses between neurones.

Show question

Question

Where is the MAOA gene found?

Show answer

Answer

The gene is found on the X chromosome.

Show question

Question

Why would dysfunction of the MAOA gene affect a person’s mood?

Show answer

Answer

The gene codes for enzymes that break down neurotransmitters such as serotonin. If the gene cannot do this properly, these neurotransmitters are left in the synaptic cleft for longer and affect a person’s mood.

Show question

Question

Who re-introduced the Warrior Gene and gave it the ethically questionable connotations?

Show answer

Answer

Dr. Rod Lea.

Show question

Question

What traits are associated with the warrior gene?

Show answer

Answer

Aggressive behaviours, risk-taking, addiction issues, and psychiatric disorders are associated with the warrior gene.

Show question

Question

How many Mãori men had the MAOA gene variant compared to Caucasian men?

Show answer

Answer

56% of the Mãori men had this MAO-30bp-rpt allele, almost double that of Caucasian men analysed in a different study.

Show question

Question

What did Brunner et al. (1993) find in their study?

Show answer

Answer

There was a point mutation in the MAOA structural gene (specifically the eighth axon). This changed how this gene coded for the enzyme production, which caused issues with the breakdown of neurotransmitters.

Show question

Question

What did the men in Brunner et al. (1993) show in their behaviours?

Show answer

Answer

The behaviours of the men in Brunner et al. (1993) consisted of impulsive aggression, arson, and attempted rape.

Show question

Question

What did Lea state the Mãori men were more likely to be like?

Show answer

Answer

‘Obviously, this means they are going to be more aggressive and violent and more likely to get involved in risk-taking behaviour like gambling.’

Show question

Question

What reportedly is the cause of the high occurrence of the MAOA (warrior) gene in the Mãori men?

Show answer

Answer

Lea suggested this was due to the nature of the Mãori men’s past; they had to engage in many risk-taking behaviours, such as migration and fighting for survival, which has led to aggressive behaviours in the present, modern-day, and a genetic bottleneck.

Show question

Question

Give a strength of the genetic research on the MAOA gene.

Show answer

Answer

The MAOA gene is fundamentally linked to mood due to producing enzymes that deal with neurotransmitters. Mood and behaviours will also be affected if the gene is affected. This suggests a genetic component to behaviour and moods, particularly aggression, and validates the genetic research on the MAOA gene.

Show question

Question

What did Caspi et al. (2002) find in their study?

Show answer

Answer

They found that the MAOA gene was important in moderating the effect of maltreatment. If children had a genotype that expressed high levels of MAOA, they were less likely to develop antisocial behaviours after suffering maltreatment.

Show question

Question

Give one weakness of the genetic research on the MAOA gene.

Show answer

Answer

McDermott et al. (2009) found in their study that the MAOA gene is not explicitly tied to aggression, even in low provocation conditions. Instead, it predicts aggressive behaviours in high provocation situations.

Show question

Question

Is the ‘warrior gene’ unethical?

Show answer

Answer

Yes, the ‘warrior gene’ is unethical as it has racial overtones that unfairly describe a race of people as aggressive due to their genetic makeup.

Show question

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