foot. In contrast to humans, the femur bones of apes drop down vertically, making the knees relatively far apart and the feet far apart. When apes (or bears) try to walk on two legs, it can be observed that they sway awkwardly from side to side as they try to maintain balance. Apes must have widely spaced feet because this gives stability in quadrupedal motion. The angled femur bone of humans also explains why humans are so good at standing on one leg. VII FULLY EXTENDABLE KNEE JOINTS The human knee
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