2 well, if a trait has some visible manifestation, what prevents the offspring from being eaten before reaching reproductive age? Competition still works. 3. I don't know, too. Just thought someone might give it their best shot. 4. If only the sons can use it effectively, then does it not mean that daughters having this gene would be outcompeted, dying in childbirth always (if it's a dominant allele) or a fixed % of times (if it's not), and so the allele will just reach some equilibrium in the population? And the 'intelligent' males will seek to have children from 'not-intelligent' females, since some offspring is strictly better than zero? (That's probably what Vaniver said.)