you can't compare IQ scores between groups living in different conditions. It's also dubious on an individual level.

IQ is not a universal measure of intelligence, IQ tests are biased to measure a certain kind of thinking that you find in a certain kind of environment. People grow up in different environments and think in different ways, and the test is gonna favor some over others. American IQ scores increase every year, and the average American IQ score in 1932 has been back-estimated to around 80. According to the logic of this twitter lib, the average American in 1932 would have been "borderline cognitively impaired."

https://www.theguardian.com/technology/2012/sep/23/james-flynn-iq-scores-environment

If you were asked [on an IQ test]: "What do dogs and rabbits have in common?", what would you say?

Interviewer: They are both mammals.

Correct. A kid in 1900 would say: "You use dogs to hunt rabbits." He would get the question wrong because, before people had lots of formal schooling, they had a utilitarian mentality, and they were fixated on the concrete world and using it to advantage. You've been raised in a scientific world where you think classifying things is an obvious prerequisite for understanding them. To you, a dog and a rabbit are just mammals; you are not interested in whether it is a beagle and good for hunting rabbits. So IQ gains over time are totally fascinating if you know how to interpret them and don't just run around saying: "Are we getting more intelligent?"