It can very easily be discounted, mere consumption of anything (psychedelics included) does not alter brain physiology or DNA. Getting high doesn't mean you will produce offspring with increased intelligence, that doesn't make any scientific sense whatsoever.lol!
there was a point of time in our evolution where our intelligence grew exponentially compared with the previous x amount of years, so far this rapid expansion is yet to be explained or figured out. The consumption of mushrooms is just one theory which at present can’t be discounted
Did use of psychedelics influence early human culture? I'd say yes, probably most significantly in the development of early proto-religions and the tribal idea of a shaman.