There is a way hook ups are serving young women. And it was important for me to always talk about how behaviours were serving girls, not just making them the victims.

I asked a high school girl about unreciprocated oral sex and said, "What if guys were asking you to get them a glass of water and never offered to you a glass of water? Would you put up with that?" She burst out laughing. It never occurred to her.

Saying "yes" [to sexual activity] is a pretty low baseline for sexual experience and I wanted to write about what was happening to girls after "yes."

Parents tend to name all of baby boys' body parts, but with girls they go from belly button to knees with this void in the middle. That doesn't change as kids go into puberty.

Girls would say: "I have a boyfriend for that." So in addition to putting their pleasure literally into someone else's hands - an inept teenage boy - these are the same girls who say they do not climax with a partner. It's the opposite with boys; they say because they can do that themselves, girls should perform oral sex.

Sex-ed courses look at girl's internal parts: for boys it's about ejaculation, erection and wet dreams; for girls, it's periods and unwanted pregnancy. We never talk to girls about sexual self-exploration or self-knowledge.

While I completely disagree with the "purity" concept, it was the only place I saw fathers talking to girls about their expectations and attitudes to sex and expressing love and support. I didn't see liberal dads having similar conversations with their daughters.