Film Theory: The Cars in The Cars Movie AREN'T CARS!

Consider the world of Cars - a world populated by living, breathing, thinking cars, surrounded by evidence of a human society; but with out any actual humans. There are certain theories that posit these Cars are AI and are all that are left after humans left our world behind. But certain things just don't seem to fit. So if they aren't AI then what are they? Prepare to have your mind blown.
Many of you have asked me to weigh in on the Pixar timeline theory, consider this my first step.