The AiA derivation is the story of the development of the brain in association with the development of skills of the hands. There is strong support to indicate that the brain and humanity owe their evolution to the hand which adapted to ulnar opposition allowing the thumb to oppose the 3rd, 4th, and 5th fingers. This motor function distinguished humans from other primates and enabled the hand to hold instruments and objects and to have fine control of their use. The development of the brain seems therefore to have followed the skills of the hand.
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