The brain evolved like everything else. There has not been enough time for evolution to change the structure and size of our brains.

Furthermore, IQ is a measurement of the ability to take IQ tests. An indigenous Amazonian might be the smartest person in the world but will fail practically every IQ test you can give them.

IQ suggests there is only one sort of intelligence, which is nonsense and easily disproven by autistic people who have great difficulty achieving tasks by people determined to be of average intelligence but are able to do mathematics at a level that the average person couldn't even comprehend.

Kim Peek had a tested IQ of 87.

https://www.psychologytoday.com/us/blog/the-superhuman-mind/201212/kim-peek-the-real-rain-man

He could read both pages of an open book at once, one page with one eye and the other with the other eye. This style of reading continued until his death in 2009. His reading comprehension was impressive. He would retain 98 percent of the information he read. Since he spent most of his days in the library with his dad, he quickly made it through thousands of books, encyclopedias, and maps. He could read a thick book in an hour and remember just about anything in it.

Because he could quickly absorb loads of information and recall it when necessary, his condition made him a living encyclopedia and a walking GPS. He could provide driving directions between almost any two cities in the world. He could also do calendar calculations (“Which day was June 15, 1632?”) and remember old baseball scores and a vast amount of musical, historical, and political facts. His memory abilities were astounding.

How does IQ make any sense as an accurate measurement of intelligence in the face of people like Kim Peek?

Also, I have no idea why you think 'training' a brain would be any different now than it was 5000 years ago. That just means keeping your thinking skills active.

Do you ever think about looking into things before you decide you need to insist publicly they work this way?

They weren't primative, the Greek and Egyptian civilizations, some of the very first civilizations that existed, developed and exchanged technology, art, and information that we still use to this day. Western civilization wouldn't exist without them.

Their world was just as complex for them to survive in as ours is, and maybe more so. They came up with ideas and solutions to problems and their thinking gave us that tech we have today.