Charles Darwin suggested that our ancestors stood upright in order to use tools. But evidence suggests that tools appeared only 2.6 million years ago, whereas bipedalism is much older, emerging around 4.2 million years ago, perhaps even 6 million years ago. Here's a list of advantages of bipedalism: - hands can use tools - hands can be used for signalling - hands can carry surplus food back to the tribe - hands can be used to throw stones and other weapons