There just ain't no goddamn gene that decides whether you'll be able to install a light switch or not. If one understands the proper paradigm for learning something they'll be able to do it. It's just that the paradigm for learning mathematics and say, history are different. If you're having trouble learning calculus you need to change your method - find out how people who are succesful at mathematics go about it. Introspection is a difficult business.
People like to make their thought processes seem more esoteric than they actually are.
Success in life has nothing to do with this mythical potential. When you apply to a college or for a job only a very small portion of you is reflected in the application. College admissions offices know your grades and standardized scores, have a writing sample, and the opinion of a few high school teachers. They make an admissions decision based upon very limited criteria - criteria which one has a great deal of control over. It's thought by many people that standardized tests measure the ability of an individual to achieve in that particular area.