acts as a shock absorber when walking. One feature mentioned in article 20 is a oval hollow at the bottom of the humerus where the humerus and the ulna lock in place. This is an adaptation to knuckle walking and is not present in bipedal hominids.Many theories have been made about what type of paleoecology or paleoecological changes were the niche for bipedalism. It must have been a strong force since bipedaliam is generally slower and more awkward than quadrapedal locomotion. It also puts the animal at a greater risk of injury, according to Owen Lovejoy of Kent State. The current most widely accepted theory is that there was a continent wide drying up of Africa starting around 5mya. This caused shrinkage of the large forests to scattered patches and an increase in the size and amount of savanna grassland. The savanna hypothesis states that these changes forced our ancestors to adapt from living solely in the jungle to spending some time in the savanna where bipedalism would make them better suited through such ways as providing them greater protection from the sun by putting less surface area of their bodies directly under it. Walking bipedally would be an efficient manner of locomotion through the arid and somewhat barren (compared to the jungles) savanna grasslands between the sparse resource richer forests. Standing upright on the hind legs would have raised out ancestors heads above the tall savanna grasses so that they could see where they were going, whatever they might be looking for or what predators might have been looking for them. Some anthropologists theorize that bipedal locomotion was reinforced by the fact that the freed arms could be used for such tasks as carrying large amounts of food to feed their young and mate(s). Later, as hominids became more intelligent, the arms could be used to carry weapons for defense against predators and for hunting....
