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Nature or nurture?
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WHY are we mad, creative, thieving, impulsive, obsessive, depressed, loving or murderous? Is it because of our genes or because of our environment?
Ever since mankind contemplated his own existence, the "nature versus nurture" debate has raged.
Now a powerful new tool has entered the fray: the human genetic code.
Researchers poring over the genome, whose rough draft was completed last year in one of science's greatest achievements, are already enthusiastically predicting it will unlock dramatic evidence about the molecular causes of behaviour. This Monday, Scientists published their first attempt to decipher the map of the human gemone.
"Ultimately the human genome sequence will revolutionise psychology and psychiatry," Kings College London researchers say this week in the US journal Science.
"The most important impact will be on understanding the neurobiological basis of individual differences and achieving a better grasp of the etiology of (mental) diseases."
But they downplay fears that the genome will serve to reinforce the bleakest view of determinists.
Genes, they say, are likely to be more important than environment on behaviour, according to studies that have notably looked at the fate of identical twins who were separated and brought up by different families.
But headline-making claims that a given gene can be the cause of crime, homosexuality or sporting brilliance are dangerous nonsense, they say.
For one thing, behaviour is likely to be a cause of complex action between multiple genes rather than just one. And behaviour is still strongly affected by moral codes and social pressures.
"The effect of genes on complex traits like behavioural traits is probabilistic rather than deterministic," co-author Peter McGuffin, of Kings College's Institute of Psychiatry, told news sources.
"You may have a greater propensity for anti-social behaviour because of your genes than someone who doesn't have the genetic makeup. But that doesn't mean you're definitely going to be anti-social. It doesn't rule out free will."
Where the genome will especially score is identifying mental disorders that may have genetic roots, which will be the first stage towards devising a medicine to treat them, McGuffin said.
Another rich area for gene-hunters are the DNA sequences that could make an individual more vulnerable to addiction.
"Between 40 and 60 per cent of an individual's risk for an addiction, whether it is to alcohol, opiates or cocaine, is genetic," say a team led by Eric Nestler of the University of Texas Southwestern Medical Center, writing this week in the British journal Nature.
(SD-Agencies)
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