An evolutionary scenario: the early hominids
The first hominids split off from the primates six million years ago and were distinctly bipedal, with erect posture, freed hands, and appositional thumbs. They showed a striking increase in brain size compared to the apes, and they were strongly visual. The main form of cognition in Australopithecus was episodic, in that it was concrete, situation-bound, and non-reflective-time-bound to the present moment. Learning was procedural and involved actions rather than thought, although there were indications of a crude capacity to develop internal representations and of abilities to abstract from concrete events. The Australopithecines were faced with several emergent adaptive issues and selection pressures beyond those faced by the primates. They included a dawning social organization of greater stability and complexity compared to that seen with apes. Despite another one million years of developmental time, this species of hominids was very much like the Australopithecines—attesting again to the incredibly slow pace of evolutionary change.