"Environmental circumstances could possibly lower the IQ of a person"
Absolutely. It goes both ways. Being forced to adapt to survive vs staying in the same sedentary lifestyle in an area with abundance tends to weed out the less intelligent. You could even argue that it's not about lowering the IQ, it's about failing to raise it through evolution.
You can’t transform an average person into a 140 IQ genius via good nutrition and education, but you can destroy someone with 140 IQ potential by sabotaging their environment.
"Environmental circumstances could possibly lower the IQ of a person"
Absolutely. It goes both ways. Being forced to adapt to survive vs staying in the same sedentary lifestyle in an area with abundance tends to weed out the less intelligent. You could even argue that it's not about lowering the IQ, it's about failing to raise it through evolution.
You can’t transform an average person into a 140 IQ genius via good nutrition and education, but you can destroy someone with 140 IQ potential by sabotaging their environment.
Correspondingly, you're not going to be able to see what a population would achieve in a proper environment until you get them there.
Selection is required just to maintain IQ, let alone raise it. Without it, the population accumulates IQ-reducing mutations over time.
Guy, intelligence isn't the only viable survival strategy.
Jellyfish are doing just great, thanks.
Environmental pressure could just as easily select for, say, athletic ability rather than cognitive ability.