We are given brains and the larger the brain or the better formed the brain was the less energy it consumed in solving a problem and the better it was in processing information.

from here a scientific american article on intelligence and the brain:

Perfection from Practice
Whatever the neurological roots of genius, being brilliant only increases the probability of success; it does not ensure accomplishment in any endeavor. Even for academic achievement, IQ is not as important as self-discipline and a willingness to work hard.