Studies today proves that bipedal locomotion evolved from quadrupedalism because it was more energy efficient.
In a research conducted by scientists
4 humans and 4 chimpanzees were made to run on a treadmill, the chimpanzees were trained to walk quadrupedally and bipedally on treadmill. When the results came out humans had used only one quarter of the energy the chimpanzees had used while knuckle walking.
