Either were programed to look for certain things in a mate (no clue why "brains" isn't one) or maybe the media (tv, internet ect) has shown us what we want and we accept it in ignorant bliss.
I think being attracted to one thing seems kind of silly though. Imagine if it were completely random and not a factor of childhood/life experiences or external influences.
Guy 1: I think your ears are hhhooottt.
Girl 1: Tee Hee, my what a nice and big right knee cap you have (blush)
Our current idea of beauty is based on Cleopatra of the Egypt! There have been many points of view I’m sure. In Edwardian times in England men thought that women’s foreheads were sexy (don't understand that one), this could have been the first indication of choosing a mate based on skull size.
I hate it when people use the word 'ego' wrongly. Everyone is supposed to have an ego. Its healthy.
What better honesty could there be besides chasing after what you want! Sure, certain people would want bad things but thats generally unhealthy. I don't think people should fear wanting reasonable things.
It is also true that a persons id and super ego can be out of proportion.