A new report challenges the theory that Sahelanthropus tchadensis, a hominid that lived more than 6 million years ago, was our earliest known human ancestor. French paleontologists uncovered a Sahelanthropus in Chad almost two decades ago. Nicknaming it 'Toumai,' they heralded the creature as an early biped — with a skull indicating it had an erect spine. But a new report suggests Toumai is just an ancient primate, more closely ...