As their brains evolved to become larger, early humans developed an innovative tool – the stone hand ax. The hand-ax was created about 1.6 million years ago to butcher large animals. Hundreds have been found in an excavation site in Kenya. Once the basic design was established, people in Africa continued to use the hand ax for over one million years. The fact that the tool changed so little in over one million years leads paleoanthropologist, John Shea to believe the tool was effectively designed for its purpose.