Intelligence is mostly determined by genetics. That's why smart children nearly always have smart parents. If intelligence is mostly determined by genetics and there is a group that has large intelligence gaps demonstrated by every indicator of intelligence that we have ( IQ tests, school tests, standardized tests, LSATs, SATs, professional job tests, ASVAB military tests, as well as pure observation
it must be logically so that most of that difference is attributable to genes. Look, there's no ways around it, no if ands or buts, it's very simple. SOME of the reason for differences for intelligence is due to environment and such things like health, education, effort, etc. To say that there is no genetic component to intelligence flies in the face of all common sense!