![chimpanzee skeleton chimpanzee skeleton](https://images.fineartamerica.com/images-medium-large-5/chimpanzee-skeleton-ucl-grant-museum-of-zoology.jpg)
This means that we shift less weight when walking, making it more efficient.
![chimpanzee skeleton chimpanzee skeleton](https://norwegianscitechnews.com/wp-content/uploads/2018/02/lucy-1000x644.jpg)
![chimpanzee skeleton chimpanzee skeleton](https://images.fineartamerica.com/images-medium-large-5/chimpanzee-skeleton-daniel-sambrausscience-photo-library.jpg)
This means that our thighs slope inward (we are ‘knock-kneed’) bringing our feet in closer to the centre of gravity. Humans also have a '''larger valgus angle''' the angle the femur makes at the knee. You should be able to see that the top of the femur increases in size, which reflects the increased weight load on the joint as humans spent more time walking on two legs and grew larger in size. The intermediates represent different Hominin species (in chronological order). This photo shows the femur from a chimp (left) through to that of a modern human (right). '''Femur (thigh bone)''': Bipedal standing increases the weight on each leg, and the area of the '''joint surfaces''' of the femur (upper leg bone) reflects this. Humans have a more ‘bowl shaped’ pelvis to better support the organs above. '''Pelvis''': Humans have a much broader pelvis giving stability when walking upright as it transfers the weight directly to the legs. It also acts a little like a spring to absorb force or jarring during activity. The human spine has an S shape that keeps the head and the torso above the centre of gravity. Apes have a rounder, barrel shaped rib cage. Humans have a broad chest that is flatter (front to back), placing the centre of gravity back towards the spine, helping us to stand more upright.