The most remarkable thing about Joshua Kendall’s new biography of cartoonist Garry Trudeau is that it exists at all. The Doonesbury creator is notoriously reclusive. He has been called “the J.D. Salinger of comics.” In 1975, Time magazine told the then-27-year-old Trudeau that they wanted to do a cover feature on him. He agreed to an interview but threw up the night before and called it off. He has kept his silence, with a handful of exceptions, ever since.Reticence comes naturally to WASPs. Trudeau is an “American aristocrat, descended from three generations of Yale-educated doctors,” Kendall writes. His earliest North American ancestor, Etienne Trudeau — whom he shares with Canadian prime ministers Pierre and Justin Trudeau, making them his distant cousins — arrived in Canada from France in 1659. His great-grandfather, Edward Livingston Trudeau, established America’s first tuberculosis sanitorium in the Adirondacks in 1884. His father carried the family tradition of medicine as the town doctor in the upstate New York village of Saranac Lake.Garretson Beekman Trudeau, born 1948, attended St. Paul’s, the preppiest of prep schools, and then Yale University. He came to Yale at a pivotal time. Between 1966, when he arrived as a freshman, and 1973, when he left with a Master of Fine Arts in graphic design, Yale went from a finishing school for blue bloods to a campus for meritocrats, strivers, and political radicals.