The femur of Sahelanthropus tchadensis, generally regarded as the oldest known hominin, has finally been scientifically examined. The results suggest it walked on four legs, so may not actually be a close human relative at all
Source:
https://www.newscientist.com/article/mg24833093-600-our-supposed-earliest-human-relative-may-have-walked-on-four-legs/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home