untermensche
Contributor
Well, yeah. But you're not saying that if a human newborn does not get exposed to certain modes of thinking that that child will have the intelligence of an amoeba, are you?
While human DNA codes for a highly-intelligent brain that is capable of abstract reasoning, logic, symbolic thinking, and complex social and emotional cognition, these faculties only develop to normal, healthy levels if a child achieves a series of neurodevelopmental milestones throughout their formative years.
If a child's environment doesn't provide the necessary stimuli, or provide noxious stimuli, then the child can develop cognitive deficiencies. For example, young children learn number skills such as cardinality, counting order, and abstract numbers. These abilities aren't learned automatically as the brain grows; they emerge while the child performs counting exercises during play and early education. If these opportunities are limited or denied to the child then they will be slow to develop. (The kitten's eyesight is an extreme example of such a phenomenon, but it is the same in principle.)
If the development of fundamental cognitive skills like these are affected by the mental stimulation a child receives then it follows that researchers need to ensure that such variation in environment doesn't confound their analysis.
I don't think the DNA codes for high intelligence.
It gives general commands to the developing brain. The neurons migrate long distances and half die. This can't be under direct genetic control. It has to be under general control with contingent action based on changing circumstance.
Sometimes by sheer luck high intelligence arises.