Who invented the wedge?

The wedge, one of the six classical simple machines, has been used from the very beginning of humankind's tool-making era, approximately 2.6 million years ago. As such, no single attributed inventor has been identified.

An early form of the wedge was the hand-axe, found to be crafted in the early Paleolithic age by chipping away at a rock to form a sharp edge. The mechanical advantage of a wedge is equal to the ratio of the length of its slope to the width; a longer and skinnier wedge requires less force, so it's more effective for splitting an object than a shorter and wider wedge.