Yeah, well if we want to split hairs Evolution is theory. Granted a pretty good one, but still. Another thing is you're assuming Catholics are biblical literalist (hint: we aren't). Think of some things in the bible (part of the book of genesis for instance) as more of fables or stories intended to teach us lessons.
Catholics don't believe in what is literally the Bible says. I they have the church, priests etc to interpret it. Catholics used to not read the Bible, there were literally wars fought over different groups about whether the common man should be allowed to read the Bible.