There’s a moment in an episode of Paul Feig and Judd Apatow’s sublime “Freaks and Geeks” when Sam Weir, chief among the geeks, has to justify dumping the prettiest girl in school. “She thought ‘The Jerk’ was stupid,” he sighs — and that’s all the convincing any reasonable viewer needs. To improve upon Proverbs 31:10, “Who can find a funny girl? For she is worth her weight in red rubber clown noses.” True, but a genuinely wild and crazy guy, one who can swing a masterpiece of spit-polished insanity like “The Jerk” in the first place, is probably every bit as rare.

Steve Martin’s memoir “Born Standing Up” (Scribner, 225 pages, $25) shows us why. For starters, Mr. Martin confesses to being anything but wild and crazy. He says that he can’t help feeling “slightly embarrassed at disproportionate attention.” Such a claim should stink of false modesty, but one has only to read about his curiously cookie-cutter childhood in Waco, Texas, and Inglewood, Calif., to buy it. His father was by turns distant and domineering, even violent; his mother was loving, but too submissive to her husband. Yet this upbringing was nothing out of the ordinary, particularly for its time. Maybe that’s why Mr. Martin wanted so desperately to be, in “the word of the day, ‘nonconformist.'”

“I began my show business career,” he writes, “at age fifteen, in August 1960. I stood behind a counter eight hours a day, shuffling Svengali decks, manipulating Wizard decks and Mental Photography cards, and performing the Cups and Balls trick on a rectangle of padded green felt.” This was at a magic shop in Disneyland, where Mr. Martin’s hard work was “made possible by lax child labor laws.” While earning pocket money he siphoned off all the tricks, stage patter, and material that he could — including a vulgar novelty postcard captioned “Happy Feet” and a coworker whose constant, exasperated refrain was, “Excuse me for livin’!”

One suspects, reading this book, that Mr. Martin’s mentality was very professional from a young age. He didn’t daydream about being a performer so much as work obsessively toward it. He notes of his later successes, “Enjoyment while performing was rare — enjoyment would have been an indulgent loss of focus that comedy cannot afford.” In a way, that admission is extremely sad — why couldn’t he enjoy it as much as his audiences did? — but it’s also fantastically impressive. The cliché is that one spoils a joke by explaining it, but Mr. Martin, speaking to us in earnest with an arrow through his head and a banjo in his arms, raises comedy to the level of a soft science. We aren’t surprised to learn that he studied philosophy and took a course in Advanced Symbolic Logic at UCLA, even less so to learn that his interest in logic came by way of Lewis Carroll.

What is most striking, and most poignant, about this memoir is that Mr. Martin cheerfully predicts his own obsolescence. He says of Lenny Bruce and Tom Lehrer: “These albums broke ground and led me to a Darwinian discovery: Comedy could evolve.” It has done so, without pity or remorse, albeit with tons of laughs. Much of Mr. Martin’s repertoire will seem dated to today’s audiences, weaned on Chris Rock, David Cross, and Dave Chappelle. His recent forays into film (“Bringing Down the House” and “The Pink Panther” leap to mind) have been downright tragic.

They may be part of a planned obsolescence, at least as far as comedy is concerned. Mr. Martin tested his stand-up act to destruction, nearly to self-destruction, and he knows it. “Though the audiences continued to grow,” he writes, “I experienced a concomitant depression caused by exhaustion, isolation, and creative ennui.” Today, his family films may pay the bills, but the endeavors he seems to take most seriously — for instance, his fiction, like “Shopgirl” (2000) and “The Pleasure of My Company” (2003), and his art collection — are serious ones. Even this sad-clown memoir, more often introspective than funny, all but says, “The old Steve Martin doesn’t live here anymore. In fact, he never did.” After decades of making us laugh, he wants to persuade us that he was just kidding, that he’s been a solemn and thoughtful guy all along.

All the same, Mr. Martin is a comic genius, and there’s really no getting around that. It’s why his bits have mutated and infected innumerable other stand-up acts and comedy movies. Would Zach Galifianakis play a piano and tell jokes if Steve Martin hadn’t first plucked a banjo and told jokes? Would “Tommy Boy,” especially its famous “dead” deer scene, have been possible without “Planes, Trains and Automobiles”? In “Zoolander,” when Christine Taylor confides in Ben Stiller that she “used to be bulimic” and he asks, breathlessly, “You can read minds?,” it’s vintage Martin, right out of “The Jerk.” Really. Look it up. Bernadette Peters tells Mr. Martin’s character, Navin Johnson, that she’s a cosmetologist, and he muses, “It must be tough to handle weightlessness.” That one, like the best of Mr. Martin’s stuff, will never get old.

Mr. Beck has contributed to the Wall Street Journal, the Weekly Standard, and other publications.