I'm not sure you understand how evolution works. Stupid people reproduce at a much higher rate than smart people.
And also being smarter than a bunch of primeapes who haven't even colonised a planet yet does not mean you aave the answers to everything
shoulda just titled it "define stupid" since the term is pretty subjective itself
This is purely anecdotal, but the majority of the intelligent individuals I know had really great parents, and the majority of the not-so-smart individuals I know had a poor upbringing.
So from my perspective, it feels like the environment that someone grows up in has a significant impact on a person's intelligence.
being not smart makes you stupid
Fluoridated tap water and not living in a bomb shelter or at least having one within walking distance of your house. Also, watching TV without a helmet made out of tin foil.