To clarify my opinion earlier in this thread, I'll repost an analogy I made in a previous thread:
"Natural intelligence to the HSC is what navigation is to an airliner. Without navigation, an aircraft can still fly perfectly - the engines, wings, stabilisers will all still work. But the lack of navigation greatly limits the distance such planes can fly. So, whilst navigation is not as significant as an airplanes wings or engines, without it a plane isnt going to get very far. By the same token, natural intelligence isnt as important as motivation or a strong work ethic, but without it, you arent going to get very far."
At the end of the day, hard work and motivation are the most important factors in achieving success. However, natural intelligence is nonetheless a necessity. Remember, even if something is relatively insignificant, it can still be necessary.