Miocene Epoch

7-5 million years ago



Sahelanthropus tchadensis may represent an ancestral hominid from the period immediately after the separation from the chimp lineage.

DATE: 5-7 million years old
SITE: Chad, Central Africa
SPECIMENS: one cranium, probably male; jaw fragments
Sahelanthropus was discovered in Central Africa from strata dated 5.2-7.4 million years old. Hominid evolution has commonly been presented as an “East Side Story”—a process which occurred in East Africa, in more open habitats of the Rift Valley. While most of the fossil excavations have occurred in East Africa, this find indicates that hominids/hominid ancestors were more widespread and that fossils should be sought in other areas of Africa (Coppens, 1994).
Its primitive features include a small, ape-sized braincase (320-380 cc), small incisors, a small sagittal crest, a massive brow ridge, shape of basioccipital bone, and the orientation of its petrous bone. Its advanced features include an enamel thickness intermediate between chimps and Australopithecus, a face which protrudes less than chimps or Australopithecus, small apically worn canines, its basicranium length and orientation, the position of the formamen magnum, and its large supraorbital torus . The basicranium is similar to that of Ardipithecus (Brunet, 2002, Wong, 2003). Although the occipital region of Sahelanthropus was damaged, the structure of the foramen magnum suggests that it was bipedal (Cela-Conde, 2003).