Roving genes - Oh, I don't know. I don't think that has anything to do with it. Good examples are the important element.
Catholic marriage - I think this actually appeals to some of the more desirable young ladies. Even the atheist girlfriend found it admirable that my son's faith was so important that he would not marry someone over the issue. It intrigued her and caused her to start to study the Catholic faith.
She's still an atheist at this point. And my son broke up with her. But who knows what seeds were planted?
Dating as evangelism. LOL!
“... the very lucky minority of women on campus...”
Women have the power. They just don't recognize it. Many of my son's friends cad about (or at least enter semi-exclusive or exclusive unchaste relationships) because, well,... they can. The young ladies are willing (some are even eager). But interestingly, many of the young men are willing to have chaste relationships with young ladies, if that's what the young lady insists upon. However, the young men will generally not turn down free sex if they sense it's on offer.
My son has friends who are “doing it” with their girlfriends, and friends who are not. The ones who are “doing it” are doing so at the implicit or even explicit invitation of the young ladies.
My own sense is that many of these young people want precisely what my son has, but don't realize it, and don't think it's realistic, because they think that the members of the opposite sex want something else. The girls think the boys all want sex, and the boys think the girls want disposable relationships, and just want to be treated like men. Equality. Reproductive rights (what do you need "reproductive rights" for if you're not going to have sex??). No "gender" differences to be recognized.
It's a lot of groupthink.
sitetest
Sadly, young women’s drive for sex, and love through sex, is probably almost as strong as young men’s—but the emotional fallout for the women is much greater. Too often American women find this out on their own. And, their disadvantage in sex ratio on campus is significant and growing.
I do think there has been found a genetic link to the propensity toward infidelity in men, and in our culture-optional society I imagine men do quite a bit of self-selection in choosing their culture. (E.g., the churched and the unchurched)