Few things make me gag and cringe in horror like the thought of parents having sex. Not just my parents, mind you. All parents. I understand that it's silly of me to refuse to accept that people over the age of 50 have sex lives. And I also acknowledge that were it not for that one time my parents accidentally did it, I would not be here today to be grossed out about it in the first place. I get all that, people. But I think there must be an evolutionary basis for why "parents" and "sex" are two words I'd just as soon not have appear in the same sentence, let alone paragraph. And I don't think I'm alone in this.