Better Brains, Bodacious Behavior Brain expansion and elaboration produced a brain of increased mass and complexity, especially for thought, language, and conscious movements. Human brain development led to patterns of human behavior known collectively as culture. By the Eocene, their descendants were living in trees, had larger brains, were active in the daytime, and possessed better grasping movements. The First Hominids Most of the earliest known hominids lived in the East African Rift Valley Cooler and drier weather encouraged the transition of hominids to mixed woodlands and grasslands. The plasticity of early hominids was the result of the capacity to learn to adapt.
More robust forms are A. boisei and A. robustus .
Homo habilis and the First Stone Tools Hominids began to use stone tools about 2.5 million years ago to get marrow out of bone and to scrape flesh from bones. From Homo erectus to Homo sapiens H. erectus migrated out of Africa into Europe and Asia. Selection pressures triggered adaptive radiations resulting in physical changes as well as cultural shifts. Homo erectus made advanced stone tools and used fire as they migrated out of Africa into Asia and Europe. By about 100,000 years ago, Homo sapiens had evolved from Homo erectus.