One decade after “Saturday Night Live” began in 1975, it added the first black woman to its primary cast. Danitra Vance, a gifted downtown actress and Second City veteran, lasted just one season.

“Saturday Night Live” later cast Ellen Cleghorne (1991-95) and Maya Rudolph, a biracial star who left in 2007. And that’s it. In this context, it’s no wonder that the cast member Kenan Thompson set off a debate this month when he explained the show’s dearth of black women this way: “It’s just a tough part of the business,” he told TV Guide. “Like in auditions, they just never find ones that are ready.”

Let me state the obvious: That “Saturday Night Live,” once home of the Not Ready for Prime Time players, has hired only three black women for its main cast— in addition to Yvonne Hudson, a featured player in 1980 — in four decades says more about the show than about the talent pool. That doesn’t mean that the show’s executive producer, Lorne Michaels, discriminates so much as he doesn’t put a premium on this kind of diversity.

Jay Pharoah, who plays President Obama on the show, does, however. He has argued that “SNL” should hire Darmirra Brunson, a comic on Tyler Perry’s sitcom “Love Thy Neighbor.” He praised her talent, but unlike Mr. Thompson, he doesn’t merely talk about being ready. Why hire her? “Because she’s black, first of all,” Mr. Pharaoh said pointedly.