| There are no fossil remains of Stone
Age hang gliders or trading records from pre-Columbian stock exchanges, but
risk-taking behavior is as old as the sabertooth. Yet what compels modern
adventurers to do such foolhardy things as jumping off dizzying cliffs or
speculating in Internet stocks? Amateur analysts once psychobabbled about a
death risk -- an old Freudian cliché that said risk takers were really driven by
subconscious feelings of guilt. Nowadays scientists say the real roots of such
behavior are as likely to be found in the convoluted chemistry of the genes as
in the id or the superego. Long before genes were discovered, Darwin suspected that behavior was at least partly inherited. But only recently have scientists working in the burgeoning field of behavioral genetics begun to link specific stretches of DNA with personality traits. Studying the DNA of subjects who were identified as curious and excitable -- two of the common characteristics of those who look for novelty and thrills -- Israeli scientists found that these people had longer versions of a gene known as D4DR than did subjects who were typed as laid-hack and reflective. It quickly became known as the novelty-or thrill-seeking gene. Shortly thereafter, an American team found a second gene, on a different chromosome, that appears to regulate anxiety. Scientists have yet to figure out how such genes might work, other than to control the flow of certain chemicals in the bratty. The thrill-seeking gene, for example, seems to facilitate absorption by nerve cells of dopamine, one of the brain's chemical messengers and a key modulator of pleasure and emotion. Similarly, the anxiety gene appears to work by affecting levels of serotonin, a mood chemical linked with feelings of satisfaction. But can such genes actually determine behavior? More important, if we happen to possess them in our chromosomes, will we inevitably grow into high rollers or high divers? Not at all, says molecular biologist Dean Hamer, a pioneer in the new field of molecular psychology. Unlike the genes that control physical traits -- the color of our eyes, say, or the shape of our nose -- such DNA merely {{U}}predisposes{{/U}} us to certain behaviors. "Genes are not switches that say 'sky' or 'outgoing' or 'happy' or 'sad', "he and co-author Peter Copeland write in their book Living with Our Genes. "Genes are simply chemicals that direct the combination of more chemicals." But some chemicals, like dopamine, can have far-flung effects. Because dopamine creates sensations of pleasure, he says, those who inherit the thrill seeking gene might want to stimulate dopamine production by pushing the danger button, whether with edgy sports for long days or e-trading. |