“The best book on this is The Bell Curve...”
Read it and believe it. If somebody reads it entirely, it is difficult to refute.
It proved the English professor’s point some time back.
And the point is that smart people earn more money, live better, birth smart people who repeat.
And that dumb people birth dumb people, who earn less money, who live less well.
Etc. Oh yeah, all races do not have the same mean and median IQs.
And if I remember a central tenet of the Bell Curve correctly, smart people by and large marry other smart people, so this divide in intellectual capability is only increasing over time.