How did a question get to be a question?

While I was reading questions on Fluther in the middle of the night (I couldn’t sleep), I found myself wondering about the origin of written and spoken questions. We all know that a spoken phrase or a sentence in which certain words emphasized in a certain way is a request for information or clarification – in other words, a question – and that in written form, the use of a question mark at the end serves the same purpose … but how did that come to be? An inquiring (sleepy) mind wants to know.