Early humans lived off the land, eating fruits and fish and raw meat since they were unaware of fire. They stood upright, unlike apes, and lived in groups in trees or caves for protection from wild animals. Their clothes were made from leaves, animal hides, and grass to protect from heat and cold. They used stone tools like hammer stones and flakes, as well as wooden and bone tools, to hunt large animals and access new foods. A key development was the discovery of fire through rubbing stones together, which allowed cooking of food and keeping warm. The invention of the wheel, initially using tree trunks as wheels, revolutionized transportation by allowing pulling of carts and connecting isolated groups.