The Personality Genes

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Still, as critics emphasize and Hamer himself acknowledges, genes alone do not control the chemistry of the brain. Ultimately, it is the environment that determines how these genes will express themselves. In another setting, for example, it is easy to imagine that Hamer might have become a high school dropout rather than a scientist. For while he grew up in an affluent household in Montclair, N.J., he was hardly a model child. "Today," he chuckles, "I probably would have been diagnosed with attention-deficit disorder and put on Ritalin." In his senior year in high school, though, Hamer discovered organic chemistry and went from being an unruly adolescent to a first-rate student. What people are born with, Hamer says, are temperamental traits. What they can acquire through experience is the ability to control these traits by exercising that intangible part of personality called character.

Over the coming decade, Hamer predicts, scientists will identify thousands of genes that directly and indirectly influence behavior. A peek inside the locked freezer in the hallway outside his own lab reveals a rapidly expanding stash of plastic tubes that contain DNA samples from more than 1,760 volunteers. Among them: gay men and their heterosexual brothers, a random assortment of novelty seekers and novelty avoiders, shy children and now a growing collection of cigarette smokers.

Indeed, while Hamer has maintained a professional distance from his studies, it is impossible to believe he is not also driven by a desire for self-discovery. Soon, in fact, his lab will publish a paper about a gene that makes it harder or easier for people to stop smoking. Judging by the pack of cigarettes poking out of his shirt pocket, Hamer would seem to have drawn the wrong end of that genetic stick. He has tried to stop smoking and failed, he confesses, dozens of times. "If I quit," he says, "it will be an exercise of character."And not, it goes without saying, of his genes.