Remains of Australopithecus Africanus and Australopithecus Afarensis the earliest primates classified as Homonidiae appear in the fossil record in Africa during the Pliocene- Pleistocene transition between 5 and 1.25 Mybp. These early hominids were somewhat more than 1 m. tall and weighed about 22 kg.. They had an upright posture and bipedal gait well adapted to primarily a terrestrial environment of an open tropical savanna. They were probably carnivores since their environment was relatively poor in high-quality plant foods consumed by forest primates. Very likely, they were scavengers as well.
It is generally believed that their evolution from earlier species of primates can be explained by the climatic changes associated with a period of cooling and glacial advances that define the Pleistocene. As the climate cooled, tropical regions became drier and tropical forests were replaced by savannas. Primates like apes and monkeys adapted to "swinging from the trees" in a forest environment "came down from the trees" and evolved into a species better suited to the new savanna environment.
By about 2 Mybp these earlier species have developed into several hominid species including the species Homo habilis. These hominids were no larger than Australopithecus but their brain capacity was somewhat larger (650-775 cc. as opposed to 450 cc.).
Homo habilis appear to be the first hominids to systematically produce and use tools. Homo habilis and its successors almost certainly used tools make of wood, bone, fiber and other readily available materials. Stone tools comprise most of our evidence for human tool use simply because only stone tools have survived. Stone tools associated with Homo habilis (commonly called Olduvain ) include scrapers, cutting tools and possibly weapons. In some instances, raw material for making stone tools appears to have been transported in excess or 10 km.. These tools appear to have been used to cut meat and possibly wood. Whether they were used for hunting is not clear. Very likely, Homo habilis procured meat largely by scavenging. There is no evidence that Homo habilis used fire or communicated with language.
It is generally believed that the species Homo hablis is the ancestor of later human species Homo erectus and Homo sapiens sapiens while other contemporaneous hominid species ultimately went extinct.
