"Maori War Council 1866-7" by G.F. von Tempsky. A higher proportion of Maori men have a gene associated with risk-taking behaviour, which may be a genetic relic of Polynesian expansion.

Credit: Hawkes Bay Gallery and Museum

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SYDNEY, 9 August 2006 - A gene associated with risk-taking and aggressive behaviour is common among New Zealand's Maoris and, when combined with certain socio-economic factors, may explain why Maoris have higher rates of incarceration.

Speaking at the International Congress of Human Genetics in Brisbane, genetic epidemieologist Rod Lea of the Institute of Envirionmental Science and Research in Wellington said the finding "is controversial because it has implications suggesting links with criminality among Maori people."

But he denied the gene predisposed Maoris to criminal behaviour. "This gene has been linked to different anti-social behaviours and risk taking behaviour, but the link that is usually quite weak, and only present in association with non-genetic factors, like sociological upbringing lifestyle factors," he later told National Radio in New Zealand.

Dubbed the 'warrior' gene by U.S. researchers, the monoamine oxidase (MAO) gene was discovered in 2002 and has been strongly linked with aggressive behaviour. Lea told National Radio on Wednesday that his research shows 60 per cent of Maori men have the gene, compared to only 30 per cent of men of European descent.

"At this stage, we have found there are differences in the genetic frequencies, but haven't linked it to criminality," he added. "There is never going to be single gene or any other factor to explain why some people become criminals and why other people do not."

Lea's team is seeking to understand why the gene is so common among the Maoris. One theory is that the great Polynesian voyages of expansion across the Pacific - which would have been risky ventures in their time - may that it may account for the gene's prevalence.

Maoris - along with many Polynesian peoples - have been genetically linked to aboriginal tribes of Taiwan. Further genomic data is being collected from these groups to better understand the history of the gene in Asia.

Maoris currently have one of the highest rates of smoking in the world, Lea said. One of the aims of the study is to understand if there are genetic factors to explain this.

"It could be a pre-disposition for addiction," he added. "I think it is important in understanding the evolutionary history of tobacco dependence. And then develop more specific gene -ased treatment for Maori, that might not be the same that the Europeans have."

"This is incredible," Maori Party co-leader Tariana Turia told The Press newspaper on Wednesday. "I realise that violence is an issue to us, but there are very common factors as well with violence which are not really related to race."

She said that Maoris having a genetic pre-disposition towards alcoholism is one thing, but it was a big leap to include violent tendencies in that.

"With Maori, it's easier to find the genes than it is in the broader Caucasian population, so it's a great case study," Lea told The Sydney Morning Herald. He told the newspaper that once his team establishes what role each gene might play, they will explore trends in other populations.