What part of the human upper limb has changed most dramatically during the evolution of its species?

In the process of evolution of the human species, the hand has undergone the greatest change in the upper limb. The first finger moved further, became shorter, opposed to the rest. Man has gained the ability to form a ring with his thumb with others. Such a need arose due to the fact that a person began to use various tools of labor. The rest of the fingers acquired mobility, which is not found in other primates. The man’s palm became flat.