Sahelanthropus Tchadensis is one of the oldest known species on the human family tree.
This species lived sometime between 7 and 6 million years ago in West-Central Africa (Chad). Walking upright may have helped this species survive in the diverse habitats - including forests and grasslands.
Though we only have cranial material from Sahelanthropus, studies so far indicates this early human had a combination of apelike and humanlike features.
Their apelike features included a small brain (even slightly smaller than a chimpanzee’s!) sloping face, very prominent brow ridges, and elongated skull.
Their humanlike features included small canine teeth, a short middle part of the face, and a spinal cord opening beneath the skull instead of towards the back, like in non-bipedal primates (or apes).
How do we know Sahelanthropus walked upright? Some of the oldest evidence for walking on two legs comes from Sahelanthropus.
The large opening (foramen magnum) in the base of the cranium where the spinal cord connects with the brain is positioned further forward (the underside of the cranium) than in apes or any other primate except humans. This feature indicates that the head of Sahelanthropus was held on an upright body.