Rubio tries to avoid giving the appearance that he's a young earther, and that he accepts dogma over science - but he doesn't succeed. We DO know the age of the earth, and for him to pretend otherwise is truly ignorant. The scary thing is that he's on a scientific committee.
As the author pointed out, the age of the earth is something that kids are expected to know before they graduate from school. Yet politicians are proud to promote their own ignorance, and many voters unfortunately seem to like that.