Have you ever found yourself in a museum's gallery of human origins, staring at a glass case full of rocks labeled "stone tools," muttering under your breath, "How do they know it's not just any old ...

Add Yahoo as a preferred source to see more of our stories on Google. Stone tools are deliberately made by the hands of hominins, like these worked on by the author. John K. Murray Have you ever found ...

John K. Murray does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond ...