David Sinclair is very good at persuading people. The catch, says a longtime colleague and scientific rival, is that he is sometimes overly optimistic about his results. “David is brilliant, but sometimes he is too passionate and impatient for a scientist,” says another colleague. “So far, he is fortunate that his claims have turned out to be mostly true.”Sinclair’s basic claim is simple, if seemingly improbable: he has found an elixir of youth. In his Australian drawl, the 38-year-old Harvard University professor of pathology explains how he discovered that resveratrol, a chemical found in red wine, extends life span in mice by up to 24 percent and in other animals, including flies and worms, by as much as 59 percent. Sinclair hopes that resveratrol will bump up the life span of people, too. “The system at work in the mice and other organisms is evolutionarily very old, so I suspect that what works in mice will work in humans,” he says.