Several evenings a week, after a day’s work at Google headquarters in Mountain View, California, Sergey Brin drives up the road to a local pool. There, he changes into swim trunks, steps out on a 3-meter springboard, looks at the water below, and dives. Brin is competent at all four types of springboard diving—forward, back, reverse, and inward. Recently, he’s been working on his twists, which have been something of a struggle. But overall, he’s not bad; in 2006 he competed in the master’s division world championships. (He’s quick to point out he placed sixth out of six in his event.) The diving is the sort of challenge that Brin, who has also dabbled in yoga, gymnastics, and acrobatics, is drawn to: equal parts physical and mental exertion. “The dive itself is brief but intense,” he says. “You push off really hard and then have to twist right away. It does get your heart rate going.”
There’s another benefit as well: With every dive, Brin gains a little bit of leverage—leverage against a risk, looming somewhere out there, that someday he may develop the neurodegenerative disorder Parkinson’s disease. Buried deep within each cell in Brin’s body—in a gene called LRRK2, which sits on the 12th chromosome—is a genetic mutation that has been associated with higher rates of Parkinson’s. Not everyone with Parkinson’s has an LRRK2 mutation; nor will everyone with the mutation get the disease. But it does increase the chance that Parkinson’s will emerge sometime in the carrier’s life to between 30 and 75 percent. (By comparison, the risk for an average American is about 1 percent.) Brin himself splits the difference and figures his DNA gives him about 50-50 odds.