>>16694660
>much of the human brain remains a mystery.
I 100% agree, but IQ (which measures g) is a psychometric phenomenon; g is unitary at the psychometric level.
>Human intelligence is not fully understood
I also agree, but intelligence (just like everything else in science) is probabilistic, it's also probably certain.

p.s. correlations between tests: https://en.wikipedia.org/wiki/General_intelligence#Cognitive_ability_testing (they all load on a common factor)