Why do monkeys walk on all fours?

Why do monkeys walk on all fours? Chimpanzees and gorillas engage in knuckle-walking. This form of hand-walking posture allows these tree climbers to use their hands for terrestrial locomotion while retaining long fingers for gripping and climbing. It may also allow small objects to be carried in the fingers while walking on all fours.

Chimpanzees and gorillas engage in knuckle-walking. This form of hand-walking posture allows these tree climbers to use their hands for terrestrial locomotion while retaining long fingers for gripping and climbing. It may also allow small objects to be carried in the fingers while walking on all fours.