Groups don't stop having different average IQs simply because they are defined as racial or ethnic,
But race and ethnicity themselves are not determinative.
intelligence is 85% heritable after all.
Citation needed. Most citations I could find said genetics may account or anywhere from 30 to 50% of a person's intelligence. But they have no idea what genes would possibly be contributing to that and how. So basically it's a hypothesis with zero proof. Either you are operating on junk science or straight up eugenicist.
While it is true that random groups of people may have different average IQs. It has more to do with what they eat, how often they eat and their exposure to different ideas than it does their genetics, etc. Even then, IQ is not actually a useful measure of intelligence.