Why did humans begin walking on two legs?

Humans began walking on two legs, or bipedalism, primarily as an adaptation to environmental changes and the need for efficiency. This upright posture allowed early hominins to traverse open landscapes, see over tall grass for predators, and carry objects or children. Additionally, bipedalism freed the hands for tool use and manipulation, which played a crucial role in the development of human culture and technology. Overall, these factors contributed to the evolutionary advantages of walking on two legs.