Differential of average IQ by country might have something to say in this regard, but also this is very controversial (even if a meaningful and true contributin

Differential of average IQ by country might have something to say in this regard, but also this is very controversial (even if a meaningful and true contributing factor to differential between national achievement). Of course then the question is what produces this differential? Culture and environment producing some sort of selective pressure perhaps, with both feeding back into each other. Certainly the heritability of intelligence argues this is a biological phenomenon to some degree.