> Your previous education, your upbringing, your cultural values, these things all also have huge effects on your aptitudes, and you've just dismissed them out of hand, apparently in favour of pre-determined genetic intelligence.

They didn't seem to do this at all. It can simultaneously be true that there are some who, due to genetics, simply cannot complete a particular task, no matter how conducive an environment they are put in, while for others genetically do not have these hurdles but whose success is still dependent on their environment.

If anything, you are the one dismissing this possibility out of hand, and making leaps of logic.