Earlier this week, GQ magazine published an interview with Senator Marco Rubio, whom many consider a contender for the 2016 Republican presidential nomination, in which Mr. Rubio was asked how old the earth is. After declaring “I’m not a scientist, man,” the senator went into desperate evasive action, ending with the declaration that “it’s one of the great mysteries.”

It’s funny stuff, and conservatives would like us to forget about it as soon as possible. Hey, they say, he was just pandering to likely voters in the 2016 Republican primaries — a claim that for some reason is supposed to comfort us.

But we shouldn’t let go that easily. Reading Mr. Rubio’s interview is like driving through a deeply eroded canyon; all at once, you can clearly see what lies below the superficial landscape. Like striated rock beds that speak of deep time, his inability to acknowledge scientific evidence speaks of the anti-rational mind-set that has taken over his political party.

By the way, that question didn’t come out of the blue. As speaker of the Florida House of Representatives, Mr. Rubio provided powerful aid to creationists trying to water down science education. In one interview, he compared the teaching of evolution to Communist indoctrination tactics — although he graciously added that “I’m not equating the evolution people with Fidel Castro.” Gee, thanks.