David Letterman has been changed by fatherhood, says Jason Gay in Rolling Stone. “It looked for a long time like it was not going to happen,” he says. But in 2003, when he was 56, the late-night talk show host and his girlfriend, Regina Lasko, had a son, Harry. Now the funnyman finds that no matter how mightily he tries to resist, he’s becoming earnest. “That happens to everyone who has children. You see things and you say to yourself, ‘What effect will these things have on my 4½-year-old son?’” So though he feels “ill-equipped” to discuss serious issues, he finds himself talking on his show about the environment, the economy, and the war in Iraq. “I’m not as smart as I oughta be for this job,” he laments, earnestly. Letterman admits he is also not as young as he might be for the job of keeping up with his son. “A year ago, my son was out walking around and found a tree and said, ‘That would be perfect for a treehouse.’ I had a treehouse when I was 12 or 13, so I thought, ‘My God, I’ll build one,’ ” Letterman says. “I’ve always heard from friends, ‘You’re too old to be a father,’ and I say, ‘I don’t feel too old, I can do this and that.’ Well, I’m here to tell you that at my age, you’re too old to build a treehouse. The thing is still under construction. It’s coming up on a year.”