“Sex and love – I have only just realised how very different they are. Sex says spread your seed as widely as possible. Love says put all your eggs in one special basket. Sex says me, me, me: love says you, you, you. Sex says muscle in on all the best-looking genes you can find. Love says search for that one unforgettable face. Sex says move on, find someone new. Love says don’t let anyone or anything take her away. Sex, you see, is biology. But love is chemistry.”