American IQ scores have rapidly dropped, proving the 'Reverse Flynn effect'

hmmm, but if you have two bushmen, one with a high IQ and one with a low IQ who will better survive. Or what if the most intelligent person in the Savanna was a bushman...So it depends on what you consider intelligence. Critical thinking is part of IQ testing and I would expect a wiley bushman to be good at critical thinking if he is going to survive.

Exactly. People that want to apply IQ see it as a general performance metric. But general performance has many different aspects. In the example of the bushman it does not matter how fast you can count the alphabet,.it won't be helping your survival.