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Genetic link to speed, aggression?
published: Sunday | July 20, 2008

Eureka? Have we found it? Why does this little bit of rock sitting in the small Caribbean Sea have the two fastest men in the world? And an unrivalled athletic profile over the years, size for size?

Speed is in our genes, researchers at the University of Glasgow and the University of the West Indies (UWI) are concluding. The Glasgow research team has been studying the muscle physiology and genetics of athletes from around the world, including some 200 Jamaican athletes present and past.

At the base of sprint speed are the fast-twitch muscle fibres stocked with the speed protein Actinen A. And early data indicate that 70 per cent of Jamaican athletes have the gene for Actinen A. Only 30 per cent of Australian athletes studied had the gene.

A scientific paper published a couple of years ago by then UWI professor, Errol Morrison, who knows a thing or two about how the human body works as a medical biochemist and a world expert on diabetes, caught the eyes of the Glasgow researchers. Morrison's paper speculated about the underlying reasons for the exceptionally high performance internationally of Jamaican sprint athletes. Morrison now heads the University of Technology, which is contributing 21.5 per cent of the Jamaican team for the 2008 Olympics and runs a sophisticated, world-class scientific sports-training and sports-education programme.

Muscle fibres

Going back to classes in neuro-muscular physiology in the dim and distant past, muscle performance is a fantastic orchestration of nerve signals, ion flow, and sliding fibres. A muscle is basically a complicated bundle of interlocking protein fibres which can slide over each other, creating a contraction when a nervous impulse tells them to do so.

Muscle fibres may be either slow twitch or fast twitch. Slow-twitch fibres contract slowly, but keep going for a long time. They are good for endu-rance activities like long-distance running or cycling. Fast-twitch fibres contract more rapidly but get fatigued more quickly. They are great for short bursts of speed, not endurance.

Slow-twitch muscle fibres rely on a rich supply of oxygenated blood as they use oxygen to produce energy for muscle contraction. Fast-twitch muscle fibres do not use oxygen to make energy, so they don't need such a rich blood supply.

Muscles are made up of a mixture of both slow-twitch and fast-twitch fibres. The thing is the balance of both. What the tests are showing is that Jamaican sprinters have an above-average presence of the gene that produces a key protein, Actinen A, for fast-twitch fibres.

Now let me join Professor Errol Morrison in a bit of speculation for which it would be nice if it turned out to be as fruitful: Not only are Jamaicans disproportionately fast on the track, we seem to be also disproportionately aggressive and violent. Now, in the world of lower animals, aggressive predatory animals are among the fastest, with the cheetah at the top among land mammals at 70 miles per hour, and the killer whale in the water at 48 mph.

Genetic link

So, is there some kind of genetic link between speed and aggression? And how strong is the genetic basis of aggression versus nurture?

I go back to social psychologist Elliot Aronson's classic book, The Social Animal, now in its 10th edition [2008], for a look at human aggression, cause, consequence, and control. Aronson asks, "Is aggressiveness instinctive?" And answers, "Psychologists, physiologists, ethologists, and philosophers are in disagreement over whether aggressiveness is an innate, instinctive phenomenon or whether such behaviour has to be learned." The heart of the disagreement, though, as the chapter on human aggression seems to conclude, is not so much whether there is an instinctive component to aggression, but how much is due to nature and how much to nurture.

In animal studies, several summarised by Aronson, there seems to be a tendency to innate aggression unleashed by some external stimulus.

A brain centre for aggressive response, the amygdala, has been identified in primates, including humans. But when that centre is electrically stimulated in monkeys, the response is dependent on the social environment: When among less dominant monkeys, the stimulated monkey will attack; but among more dominant monkeys, it will flee.

So, "the same physiological stimulation can produce widely different responses, depending upon learning". Aronson concluded from reviewing the data that "although aggressiveness may have an instinctive component in man, the important point is that it is modifiable by situational factors". So, the questions arise: How can it be modified? How much can it be modified? In our circumstances, these are certainly not merely academic questions of social psychology.

The major instigator

While aggression can be triggered by "any unpleasant or aversive situation", Aronson identifies frustration as "the major instigator", including frustration over "relative deprivation".

A significant study has shown that if a person is frustrated or angered, the mere presence of an object [like a gun] associated with aggression will increase his aggression. Other studies are showing that children model adult aggressors and sometimes outdo them. And "there is fairly clear evidence that watching violent behaviour on TV will increase the aggressive behaviour of children".

To the extent that we want to improve sports performance with nurture interventions on the blessing of nature in fast-twitch muscle fibres, we should want to reduce aggression with nurture interventions on any curse of nature in a genetic predisposition for overabundant aggression. Elliot Aronson closes with a section, "Towards the Reduction of Violence", which proposes a mix of reasoning beginning in early childhood, punishment for deviance, rewarding positive alternative behaviour, providing non-aggressive models, and cultivating respect and empathy towards, others, since those to be hurt by aggression must first be dehumanised.

Science has turned a spotlight on sports in Jamaica. Some would argue that there is a more urgent necessity to apply our best technical capacity - and more financial resources - to the reduction of aggression and the violence it is spawning.

Martin Henry is a communications consultant who may be reached at Feedback may also be sent to

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