This seems to be ignoring the elephant in the room.
Regardless as to if it's genetics or environment, neither of which are the objective fault of the person in question & both undermine any aspect of equality of opportunity & both lend an argument towards polices which ensure equality of outcome (as the previous is unachievable, better to have no game than a rigged one).
Regarding the hereditary aspect of IQ & intelligence posted earlier.
The evidence isn't that great, as to make a reasonable judgement call you need to compare children who had been adopted (twins being perfect) but even they have shared the same experiences during conception (in which parental stresses, toxicity, addiction, nutrition/malnutrition rates & will have a notable impact on a child's development.
Not to mention the studies simply show that it indicates a link, it doesn't conclusively prove anything - they also stress that environment is a very strong influence also (cases of children adopted by middle class/high IQ parents & ending up with IQ's 10/15% higher than the average - the uplift from the environment).
http://www.education.com/reference/article/effects-heredity-environment-intelligence/
The pretty obvious likely conclusion is that it's a combination of both which determines an individuals chance to succeed.