I disagree with the work ethic point, but I do think it's interesting and instead of both of us speculating would love to see some actual data.
There are a ton of dumbass people out there chugging away at grinding jobs to stay alive, and a ton of brilliant people sitting at their desks reading hacker news (not to imply that I'm brilliant; it's the rest of you I mean).
I disagree with the work ethic point based one a single datum. my work ethic drastically changed at one point in my life - whilst my IQ should have remained constant, and its quite high - 144.5 on the Mensa test I took some 15 years ago.
Similar story here - I had no work ethic at all until I failed my first year at University. (I had excellent school results, five unconditional offers of places at University etc.).
I went back, worked very hard, passed the exam I failed (maths) and after that graduated with a 1st.
I also got a stupidly high mark in an IQ test when I was 16 - largely as we had an educational psychologist in the family who had bombarded me with tests since I was about 4. There is no way that stuff actually makes you smarter but it sure does make you better at passing silly tests.
There are a ton of dumbass people out there chugging away at grinding jobs to stay alive, and a ton of brilliant people sitting at their desks reading hacker news (not to imply that I'm brilliant; it's the rest of you I mean).