The trap was laid thusly…
(7 year old)Boy: Why do fish die out of water?
Father: They can’t breath.
Father: Their bodies aren’t made to take oxygen from air.
Boy: But they can from water? Why?
Father: They evolved that way.
Boy: Oh… (father holds breath boy won’t ask him to explain evolution before bed)… well, what if fish eggs were out of water?
Father: They’d probly dry up.
Boy: And not become fish?
Father: Right. Anyway, they wouldn’t be fertilized. (Oh crap, why’d I add that?)
Father: Yup. (Giving away nothing.)
Boy: What’s fertilized?
Father: (Shit.) Female fish drop eggs. Male fish have something eggs need to turn to little fish.
Boy: (Moment of quiet reflection)
Father: (how about a red herring?) But some creatures don’t do it like that. Some don’t even need two.
Boy: Like people…
Father: (Shit.) No.
Boy: (sitting up) You have something eggs need?!
Father: (sigh) Yes.
Boy:(confident expression)…you give it to girls by kissing…
Father: (Ah shit.) No.
Boy: Then what?
Father: I’ll tell you… I’ll tell you later.
Boy: (hurt expression) Tell me now.
Father: (Fuck it.) It’s called sex and I know you’ve heard of it because I saw your little buddies saying “success sounds like…” and giggling when I got you from school one day.
Boy: (broad, satisfied -even gloating- grin)
Father: Goodnight! (Kisses son’s head and exits before any further questions can be advanced. Immediately finds mother to debrief [not that kind of debriefing, dear dirty audience.] Heads out for some fresh air.)