> College graduates only marrying college graduates, repeat that for many generations and it is bound to have an effect. I think there's enough infidelity arou

> College graduates only marrying college graduates, repeat that for many generations and it is bound to have an effect. I think there's enough infidelity around to cancel out this effect. You have around a million n*great grandparents at n=20. How many of those are likely fathered by "somebody else"? And that's just at n=20; evolution runs much slower than that. Even with perfect class-based marriage, good genes have inevitably worked their way across the social ladder through infidelity by now. "Bad" inbred lines only exist as lines; when measuring the total effect, illegitimate children need to be included, but of course they are invisible.