Environmental factor is a contributing factor to general high inteligence in the larger populace in the USA. "Lead" and other poulutants were infused in the neighborhood of underpriviledge minorities in across the USA.  Intentional or not, this is a major factor. We're seeing an uptick in intelligence for example in Baltimore, due to the fact that these environmental polutants are taken off from the equation.  Why are their more geniuses in WestAfrica and North Africa than in Central Africa..etc? Environmental pulutants thats the answer. Lucky few, escape this by mutating into Savants. I totally disagree with the old chap in your interview.