Why are the Spanish question marks upside down?

Questions in Spanish are preceded by an upside-down question mark and ended with a regular one.
Words are inflected differently when they are in a question. The final syllable tends to go “up” after a question and “down” after a statement. This happens even more extremely in Spanish, to the point that to read a sentence aloud correctly, you need some advance warning that it will be a sentence. The upside-down question mark is that warning. They do the same thing with .