A self-propelling, two-legged movement that covers ground faster than a running man or woman can. The most obvious ancestor of walking is found in modern hoofed animals, such as the horse and rhinoceros. However, there may be evidence that humans already used to walk on two legs at least 50,000 years ago. Still later in time, people began to build statues of the Egyptian deity Anubis showing him with four legs and a trunk holding up his head because he was believed to be the inventor of walking. Walking was originally only for hunting (especially for long-distance) or migration (e.g., from Africa to Europe).
Paleoanthropologists agree that early humans walked with an erect posture, similar to the pose of modern apes. In this position, the pelvis rotates forwards and backwards to provide balance and stability. While walking in this upright stance, the leg moves along the ground at a steady speed and perpendicular to its direction of travel. The front foot is planted firmly on the lower leg, while the rear foot is lifted off of the ground. By placing weight on only one foot (and possibly in a non-neutral leg position), humans may have been able to move easily over uneven surfaces like rocks and logs that animals cannot avoid. However, the amount of time and energy expended in walking is still debated.
Scientists believe that human-like bipedal locomotion evolved from quadrupedalism, which is a kind of locomotion that uses four limbs. Walking may have been the second step towards standing upright, because it allowed humans to stand up on two legs—a position that is easier to maintain than walking while also placing less stress on the joints. However, bipedalism has other advantages over quadrupedalism as well, such as allowing for more precise movements and allowing a person to see where they are walking.
The word “walk” is used to describe a wide variety of movement patterns, including not only walking in the strict sense but also running and even crawling. If one assumes that walking is defined as simply a means of locomotion using two legs, then animals with six or more legs would not be considered to walk. The word “walk” comes from the Old English “wealcan” meaning to roll or toss about as waves do in the water.
Many animals have developed organs that help them move up and down surfaces with greater ease, including non-vertebrate species such as insects and molluscs (which use their muscular foot).