NCERT · Class 12 · Biology · EvolutionTrace the key trends in human evolution from Australopithecus to Homo erectus, highlighting changes in cranial capacity, posture, and tool usage.

Human evolution reflects systematic structural, functional, and behavioral changes over millions of years. Key evolutionary milestones from Australopithecus to Homo erectus include:

1. Australopithecus: Inhabited East African grasslands about 2 to 4 million years ago. They exhibited bipedal locomotion while walking on land, though they retained features suited for tree climbing. Their cranial capacity was relatively small, ranging between 400 to 500 cubic centimeters (cc), comparable to modern apes. They used simple natural stones as weapons.

2. Homo habilis: Emerged around 2 million years ago as the first human-like hominid ('handy man'). Their cranial capacity increased noticeably to 650–800 cc. They possessed fully erect posture and were the first to deliberately fashion chipped stone tools, though they were primarily herbivorous.

3. Homo erectus: Emerged approximately 1.5 million years ago. They showed a substantial jump in cranial capacity to around 900 cc. They walked completely upright, engaged in meat-eating, developed sophisticated stone tools, and mastered the controlled use of fire.