Sahelanthropus
Sahelanthropus tchadensis (“the Sahel man from Chad”) (7–5.6 MYA). Few fossil specimens are known: a partial cranium, 5 pieces of jaw, and several teeth. No other body parts have been found.
Sahelanthropus probably walked upright. The braincase, at 320–380 cm2, appears like extant chimpanzees; almost 4 times smaller than modern humans.
Sahelanthropus‘s huge brow ridges and face resemble the face of Homo, as does the small canine teeth. But Sahelanthropus‘ tooth enamel was very thick: suited for chewing vegetation, nuts, and tubers. This combination has not been found in fossil apes, nor seen in later hominids.
Sahelanthropus may represent a common ancestor of humans and chimps, or an ancestor to neither. Some cranial characteristics resemble those of Miocene apes. Other features are more like later hominids. Sahelanthropus‘ fossils are separated from both these groups by geography and time, so Sahelanthropus as its own genus is justified.
Precious few ancestors of chimps or gorillas have been found. The upshot: the inclusion of Sahelanthropus in the hominid family tree is problematic, and its place uncertain.
