Skeletal Changes Brought by the Evolution of Bipedalism

• Femur – Evolved into a slightly more angular position to shift the center of gravity toward the geometric center of the body.
• Knee and ankle joints – Became increasingly robust to support weight better, aiding in upright walking.
• Vertebral column – Became S-shaped and the lumbar vertebrae became shorter and wider to support the increased weight on each vertebra in the upright position.
• Vertebral column – Became S-shaped and the lumbar vertebrae became shorter and wider to support the increased weight on each vertebra in the upright position.
• Big toe – Moved into alignment with the other toes to help in walking forward, improving balance and forward propulsion.
• Human pelvis – Short and broad to support internal organs and stabilize the body during bipedal movement.
• Gorilla pelvis – Longer and narrower, adapted for quadrupedal locomotion and not suited for upright walking.
• Foramen magnum – Migrated under the skull to a more anterior position, allowing the head to balance directly over the spine for upright posture.
• Foramen magnum – Migrated under the skull to a more anterior position, allowing the head to balance directly over the spine for upright posture.
• Iliac blade – The long downward-facing iliac blade was shortened and widened to keep the center of gravity stable while walking. This led to a smaller birth canal, which influenced human birth:

  • Resulted in giving birth to relatively immature infants,
  • Brain growth continues significantly after birth,
  • Promoted extended maternal care and brain development.