The development of fine and gross motor skills proceeds independently. Although they require the same physical foundations–formation of brain synapses, myelination of nerves (main story)–the two skills proceed in fits and starts. If a baby is putting lots of effort into gross motor skills one week, he won’t be working much on fine motor skills. And every new move has to be repeated over and over to strengthen neural circuits that wind from the brain’s thinking areas into the motor cortex and out to nerves that move muscles. But how quickly a child acquires motor skills is hardly a harbinger of achievement. “How early a baby walks has little to do with future athletic ability,” says Laurie Walther Nathanson, author of “The Portable Pediatrician for Parents.”

Yet stories abound of how athletic greatness was foreshadowed by childhood flair. Olympic soccer gold medalist Mia Hamm says she “began kicking a ball at the age of 2.” She lived in Italy and copied older kids in the park. And the story of how Tiger Woods swung his first golf club at 10 months has taken on the status of legend. Whether such precocious moments set Hamm and Woods on the road to stardom is debatable, but there is no question that down the road there is a “too late.” No world-champion skater or golfer took up the sport after 12. And in his 1996 book “Why Michael Couldn’t Hit,” neurologist Harold Klawans of Rush Medical College in Chicago describes how, at 31, basketball megastar Jordan couldn’t retool his visual-motor synapsis enough to whack a curve ball. “The brain has to learn how to recognize the spin and speed and direction of the [pitched] ball,” explains Klawans, “and then to swing the bat at just the right speed and in precisely the proper location.” If the brain’s visual and motor neurons are not trained between the ages of 2 and 11 to do that, by adulthood the neurons are simply not “plastic” enough to be rewired for the job.

If parents want to raise a prodigy, the best they can do is make experiences available to the child. Kids who get to handle paintbrushes and Prince racquets early on figure out that art and tennis are considered cool in the household, for instance. But sometimes it is not the obvious experiences that sculpt excellence: Walter Payton, one of the NFL’s greatest running backs, took ballet as a child. Still, physical skill is only one ingredient in artistic or athletic achievement; the rest is mental. Olympic swimmer Amy van Dyken says, “You can’t teach mental toughness. You can teach concentration, but the child won’t be happy if that’s not what the kid wants to do.”

Ambitious parents might heed the case of Yeou-Cheng Ma. She started the violin at 2 1/2 and, tutored by her father, won youth-competitions galore. Then younger brother Yo-Yo, who took up the cello at 4 1/2, eclipsed her. Yeou-Cheng suffered a breakdown at 15 over the loss of a solo career. Now a pediatrician, she doesn’t hate music–she also runs New York’s Children’s Orchestra. But Ma has little patience with parents who push their children. “The job of a child is to play,” she says. “I traded my childhood for my left hand.”