Lili you seem very quick to scoff about Darwin but your comments suggest you have not read anything about his theory. I suggest you do before disregarding it out of hand. I would recommend a book by a British scientist called Richard Dawkin. It is called climbing mount improbable (or another book called the blind watchmaker)

Sex doesn't need to involve emotion and when it does so what. The key is for me the expression "if you don't buy a ticket you can't win the lottery". Basically saying if you are unwilling to get hurt ever then you can't expect to get the best rewards. Works in two ways....if you refuse to commit yourself emotionally to things for fear of getting hurt then you can't get the full benefits of satisfaction from being deeply in love etc the other way is that if you refuse to expose yourself to the chance of rejection then you will reduce your chances of fulfilling your dreams.