[psoy]

I don't know, wouldn't be so sure without actual supporting data.

Anecdotally I know many talented people who got "broken" at high school level (due to any number of issues, from poverty to physical and emotional trauma). Having connections, mentors, initial capital, educated family, it all helps a lot.

This is not US-specific either, I made it to the US from a war-torn country across the globe with no money or connections, but I am extremely stubborn. There were definitely people who didn't make it this far who arguably had the pure IQ advantage.