"New Zealand's indigenous Maori population reacted angrily on Wednesday to a researcher's findings that Maori have a high representation of a gene linked to aggression, as the nation faces a domestic violence crisis."

According to a Yahoo news story, genetic epidemiologist Rod Lea recently presented research in Australia that Maori men were twice as likely to carry monoamine oxidase than European men, describing it as "the warrior gene." This gene has apparently been tied to aggression and risk-taking behaviors such as smoking and gambling.

"I believe this gene has an influence on behavior of humans in general, but I also believe that the influence is rather small," Lea told New Zealand's National Radio on Wednesday.

"We have to be clear that behavioral traits such as susceptibility to addiction, aggressive behavior, risk taking, all those sort of things, are extremely complex and they are due to numerous factors including non-genetic environmental factors like upbringing and other lifestyle factors," he said.

The Maori people are concerned that this will only serve to confirm stereotypes regarding their tribe: that they are violent, aggressive, with high crime and domestic violence rates. However, there is a persistent problem with domestic violence; the New Zealand government found that Maori children under 5 years old are twice as likely to be admitted to the hospital for an "intentional injury" than other groups.

Now this news piece did a not-so-great reporting job on the science. I think what they meant to say was that Maori men were more likely to carry the gene that encodes monoamine oxidase (MAOs; although there are two types MAO-A and MAO-B), which are both located on the X chromosome. MAO-A and MAO-B are attached to the outer membrane of the mitochondria and function to oxidize amine neurotransmitters such as dopamine and serotonin.

MAOs are extremely important for proper brain function as they inactivate neurotransmitters. When MAOs are in over abundance, there is too much inactivation of neurotransmitters. Neurological disorders like depression, criminal behavior, phobias, ADD, and addiction can arise. In fact, a major treatment for depression is MAO inhibitors, and these drugs are also given to Parkinson's patients to enhance the effectiveness of dopamine replacement through L-Dopa. MAOs also increase with age, and apoptotic cells (dying cells) often have increased MAOs as well.

But back to the Maori, what seems to be suggested is that they have an increased incidence of MAO genes resulting in more MAO produced as compared to other populations. As the researcher himself notes, the gene may exert some influence but behavior is complex---it results from environment as well. Perhaps the Maori are overlooking a really useful bit of information here: MAOs can be inhibited. If it is shown to be true that MAOs can increase aggressiveness, depression, etc, high-risk individuals could be treated with MAO blockers.