Geographically speaking, East Africa’s Great Rift Valley is home to a number of hominins including the Australopithecus. These fossils date back to 8 mya, closing a 4 million year gap, which we previously knew little about. A number of scientist hypothesized on the reasons for a shift to bipedalism. Charles Darwin proposed that the shift to bipedalism was motivated primarily by the desire to hunt. Early humans freed their hands so they would be able to carry weapons and tools. Peter Rodman and Henry Mchenry proposed the idea that walking was a more efficient way to get around in some areas. They built this hypothesis based on the knowledge that some forested areas grew patchy towards the end of the Miocene era. Owen Lovejoy proposed