Final answer:
Bipedalism is the human trait of walking on two legs, which is made possible by anatomical adaptations such as the valgus angle of the femur, spinal curves, arched feet, and toe alignment.
Step-by-step explanation:
The human trait of habitually walking on two legs is called bipedalism. This mode of locomotion is a key characteristic that differentiates human beings from other animals. While bipedalism is seen to various extents in other primates, it is a definitive trait of humans and has been a significant factor in the evolution of the Homo genus. Bipedal locomotion is achieved through complex anatomical changes such as the evolution of the valgus angle in the femur, spinal curves that balance the weight of the upper body, the formation of an arch in the foot, and the alignment of the big toe with the other toes. These adaptations over time have allowed for efficient bipedal movement, which has had several proposed advantages including improved thermoregulation, energy efficiency, and the ability to carry tools, food, or offspring.