I think if you take the babies of the smartest X% people in the world and raise them in poverty then yes, their average IQ will be lower than if they were raised in a middle class household.
Poverty means you have to skip meals, you can't afford books, you go to a school were there aren't enough teachers and so on... Those are all things that have an influence the intellectual development of a person.
You are confusing intelligence with intellectual capacity (IQ).
IQ is the ability for a child to do exemplary things with his/her mind.
Intelligence is building upon that.
Being poor does not make you have lower IQ, nor does it make you less intelligent. A large number of the poor have come up from the depths and are very intelligent people.
> A large number of the poor have come up from the depths and are very intelligent people.
I like to consider myself one of those people.
But I have to say, I can't imagine how my IQ would have stayed the same as I got older if I had not at least been able to eat regularly, drink clean water, make medical check-ups, etc.
I get what you have been implying, which is that a person's theoretical intellectual capability is not necessarily tied to their current intellectual capability. But the brain is an adaptive organ, not a monolith that comes out of the womb fully-formed.
It's at least possible (and likely, IMO) that there are various 'gates' in the development of the brain where if pre-requisites for development are not met, that the opportunity for that natural development gets closed off as the brain moves onto further forms of modification and maintenance of its neural net.
At some point the brain has to switch over from adolescent development to adult 'maintenance programming'. If you are resource-constrained during that adolescent phase it may be difficult to catch back up, even in a resource surplus as an adult. This would show as a lower IQ (even on an ideal IQ test), even though a higher IQ could have been achieved with proper 'care & feeding' as a child.
Poverty means you have to skip meals, you can't afford books, you go to a school were there aren't enough teachers and so on... Those are all things that have an influence the intellectual development of a person.