Australopithecus and the Emergence of Earliest Homo

The age of origin of the Homo lineage is thought to have fallen in the time period between 2.5 and 3.0 Ma.  The relevant fossil record in Africa is, however, notoriously poor, thwarting attempts to discern the pattern of earliest Homo evolution and delineate its proximate causes. Recent fossil discoveries in the Afar rift of Ethiopia push the Homo lineage back to 2.8 Ma. Although separated in time from Australopithecus afarensis, a potential ancestor, by only two-hundred thousand years, these fossils show derived dental and gnathic traits and occur in a strikingly more open paleoenvironmental setting than the ones usually occupied by early australopiths.  Coupled with new discoveries of very early flaked stone tools at West Turkana, Kenya, contemporary with small-brained australopiths at 3.3 Ma, the Ledi fossil hominins open the possibility of a new evaluation of factors involved in the origin and early evolution of Homo.