Or indeed is it something people made up that has no real correlation to reality, but just happens to be useful anyway. For that matter, do we really perceive the distinction, or merely convince ourselves we do? Its an old metaphysical issue that by definition can never be proven one way or another.
Physically we can say that our current observations indicate we can't have one without the other and linguistically the two terms define each other. This suggests relativism rather then dualism. What looks like chaos from one point of view can often look orderly in another and exactly what it really might be is anyone's guess.