Humans have a shorter, S-shaped, and somewhat flexible backbone. Power Grip and Precision Grip Prehensile movements allowed fingers to wrap around objects in a grasp. Opposable thumb and fingers allowed more refined use of the hand. The precision and power grip movements of the human hand allowed for toolmaking. Teeth for All Occasions Monkeys have rectangular jaws and long canines.
Humans have a bow-shaped jaw and smaller teeth reflecting the changes in diet.
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.