Lower Paleolithic - Gelasian

Gelasian

Further information: Gelasian, Homo habilis, and Olduvai Gorge

The Lower Paleolithic begins with the Gelasian (Lower Pleistocene), some 2.5 million years ago with the appearance of the Homo genus (Homo habilis), possibly developing out of australopithecine forebears (such as Australopithecus garhi). These early members of the Homo genus had primitive tools, summarized under the Oldowan horizon, which remained dominant for the best part of a million years, from about 2.5 to 1.7 million years ago. Homo habilis is assumed to have lived primarily on scavenging, using the tools to cleave meat off carrion or to break bones in order to extract the marrow.

The move from the mostly frugivorous or omnivorous diet of Australopithecus to the carnivorous scavenging lifestyle of early Homo has been explained by the climate changes in East Africa associated with the Quaternary glaciation. Decreasing oceanic evaporation resulted in a drier climate and an expansion of the savannah at the expense of forests. Reduced availability of fruits forced some Australopithecine to unlock new food sources found in the drier savannah climate. Derek Bickerton has placed to this period the move from simple animal communication systems as they are found in all great apes to the earliest form of symbolic communication systems capable of displacement (referring to items not currently within sensory perception), motivated for the need for "recruitment" of group members for scavenging large carcasses.

Homo erectus appears by about 1.8 million years ago, via the transitional variety Homo ergaster.