From Peter Millington:

Re: Clues to language origins seen in ape gestures (April 30): Along the same subject, I noticed years ago that cats and dogs when they want something from a human seem to raise their vocals at the end of their “statement” (for lack of a better word) in the same way humans do with a question. Even a complaint comes out as a whine, again which humans also do when complaining. Has any research been done along these lines? Do other animals do the same thing or is the whole thing a form of mimicry? If it is mimicry then it seems to be pretty clever and right on the button.