Bipedal Locomotion

Summary of the anatomical characteristics that reflect the human adaptation to bipedal locomotion

Hominins are the only primates that are fully bipedal. As with other types of locomotion, bipedalism is reflected in numerous adaptations of skeletal structure, starting from the head and moving toward the toes.

Two important adaptations are found in the cranium. The first is the position of the foramen magnum, the large hole at the base of the cranium that allows the brain to connect to the spinal cord. In a quadruped, the foramen magnum is positioned posteriorly, toward the back of the cranium, allowing the vertebral column to remain parallel to the ground. In a human the vertebral column is perpendicular to the ground. Therefore, the foramen
This is largely the result of our elongated femurs, tibias, and fibulas.In addition to being longer, the biped femur also has an unusual angled position. In most primates, the femur extends relatively straight from the pelvis to the knee. This keeps the knee toward the lateral side of the body. In contrast, bipeds have an angled femur that extends down and medially (inward) from the femur to the knee. This centers the knees (and lower legs) under the body and near the midline, which improves our balance and walking efficiency. As we move forward, our body follows a central path, rather than wobbling from side to side. In addition, when we briefly balance on one foot each time we take a step, the lower leg is closer to our midline and more stable. In bipeds, the two feet support the entire weight of the body and are the only areas to make contact with the ground while moving. Therefore, they are incredibly important and have several key
The ape toe has a dual function, including terrestrial walking and grasping or manipulating objects. Humans have largely lost their ability to manipulate objects with their toes. The position of the ape big toe is abducted while the human hallux is adducted. Bipeds have shorter toes than other primates. Instead, we use our toes for support while standing and to help push off when we step forward. The hallux is larger than the other toes, which is the opposite of what is seen in most primates. Our relatively enlarged hallux helps with bearing weight and transmitting force as we take steps. Second, bipeds have an adducted hallux that is in line with the other toes to provide better balance and pushing off ability. Third, the biped foot has a longitudinal arch that extends down the length of the foot from the base of the toes to the heel. This arch helps with shock absorption as we walk, and it helps to direct our body weight and energy to create a smooth push off while stepping