@grimalkina I remember reading The Mismeasure of Man when I was in grad school (for physics, so this was just pleasure reading) and being struck when Gould pointed out that the existence of general intelligence is a hypothesis that must be proved; it's by no means obvious that it's true, and the burden of proof is on those asserting it. It was one of those things that's obvious once it's stated, but I don't think I could have clearly articulated it before reading that book.
@internic I had the same experience reading it as a teenager!