Both monkey (Macaca fuscata, left) and human (Homo sapiens, right) have five physically independent fingers (top) and five toes (bottom), although the human foot is irregular in shape. Monkey hand, foot and human hand are similar in shape except for monkey heel (grey). In addition, human toe I is larger than the lesser toes, whereas monkey toes are similar in size. The fingers were represented independently (color coded) in the primate somatosensory cortex (SI): I, red; II, orange; III, yellow; IV, green and V, blue. By contrast, the representations of the toes were fused, with the exception of the great toe in humans.