I read a book recently that took an athropological and evolutionary approach to the differences in the sexes. I think a lot of what they said makes sense, even though I may not agree with the "origins" of the male and female tendancies they illustrate. Their conclusion was that men have a preoccupation with various forms and shapes of the female body for progenitory reasons. In particular, hip to waist ratio preferences seem to be genetic in males. It is also possible that males have certain, shall we say, mammory preferences which relate to a females potential for nuturing strong healthy children. Those preferences for the natural purpose of breasts have a sexual manifestation - the "better" the breasts (and this doesn't necessarily relate to size), the more men want to have sex with a woman. So, our "preoccupation with bossoms", as J Algernon puts it, may in fact be genetic and have evolved for good reason.