Feeling aggressive? It could be your 'warrior gene' in action

PUBLISHED : Sunday, 10 July, 2011, 12:00am
UPDATED : Sunday, 10 July, 2011, 12:00am


Do you have the 'warrior gene'?

I believe that I am a peaceful man, longing for harmony: I never shout at lazy students (yes, they do exist at Asia's No1 university, HKUST); and I never used to beat my two boys when they were small and very naughty. As a scientist, however, I like creative solutions and am ready to take big risks.

The Swiss DNA test company Igenea has a new test for the 'MAOA gene'. I was tempted to try - a swab from my mouth would be sufficient. So why not?

The background: monoamine oxidase A (MAOA) is an enzyme in our body that breaks down important neurotransmitters in the brain. Neurotransmitters like dopamine, norepinephrine and serotonin help transfer the nerve impulses. The enzyme is encoded in our DNA by the MAOA gene.

Humans have various forms of the gene, resulting in different levels of enzymatic activity. People with the low-activity form (MAOA-L) produce less of the enzyme, while the high-activity form (MAOA-H) produces more of the enzyme.

Less MAOA means your neurotransmitters are less broken down. You have a higher concentration in the blood. You should be more aggressive.

Rose McDermott, a professor at Brown University, had a theory that individuals with MAOA-L display higher levels of aggression- they're not aggressive in general, just in response to provocation. She ran an experiment in which subjects were asked to cause physical pain to an opponent they believed had taken money from them. How to punish them? By administering varying amounts of hot, spicy sauce.

Only about a third of people in Western populations have the low-activity form of MAOA. By comparison, low-activity MAOA has been reported to be much more common- approaching two-thirds of the population- in some peoples with a history of warfare. This has sparked controversy, with MAOA dubbed the 'warrior gene'.

Seventy-eight male students from the University of California-Santa Barbara took part in the experiment over networked computers. Each subject first performed a vocabulary task in which they earned money. Then they were told that a 'bad' anonymous partner, linked over the network, took some of their earnings. They could choose to punish the 'bad' takers by forcing them to eat unpleasantly hot sauce- but they had to pay to do so. Don't worry: in reality, no one actually ingested hot sauce.

All 78 were tested for their genes. The results clearly demonstrated that low-activity MAOA subjects displayed higher levels of aggression. MAOA significantly predicted aggression in a high-provocation situation (when a lot of money was taken). So MAOA influences aggressive behaviour, with potentially important implications for interpersonal aggression, violence, political decision-making - and crime.

This stirred a heated debate. Should murderers be excused if they have the 'warrior gene'? (My answer: we are not simply the product of our genes. Culture and education form the personality.)

The 'warrior gene' is located on an X chromosome. Males get it from their mothers. As men have only one X chromosome (in the pair XY) it can display its full activity. Women, however, have XX, and one X can compensate for the activity of the other. (My mother is an extremely peaceful person- women in general seem to be more peaceful.)

So, what did Igenea have to say about my DNA? Tell you a secret: I have five copies of the gene - a very good warrior! But is that good or bad? I am a pacifist and hate the military, but love to take risks. So now I want to know more. There is another gene mutation: 'avoidance of errors'. This might be even more important than being aggressive...

Reinhard Renneberg is a professor of bioanalytical chemistry at the University of Science and Technology