The thumb stands out so much against the other digits because, unlike the other four, the thumb is opposable. This means it can rotate and move around to touch the pads of the other four fingers on the hand. This advanced mobility that the thumb possesses is what makes it so we can pick up and grip objects. Contrary to initial thought, opposable thumbs are not unique to humans. Most other primates, like chimpanzees and monkeys, also have opposable thumbs!