i know you guys probably get annoyed when i bring up stuff i learned about this topic, but this is interesting:
i had a couple lectures in a class called biosocial anthro and the teacher was talking about physical cues. a cross-cultural study found that people rate western women as appearing younger than non-western women because of 1) shelter from the environment, 2) make-up, and 3) bras.
for that class we have a discussion session once a week run by a grad student majoring in sexual selection. she mentioned that during human evolution, men that prefered saggy breast didn't reproduce and pass their genes as much as men who sought firm breast (because breast characteristics indicate estrogen levels, age, etc.). hypothetically, if 50% men prefer firm breast and 50% prefer saggy breast and if breasts indicate fertility (which they do), then many generations later, the proportion of men who prefer firm breasts will increase because those men pass more of their genes than men who prefer saggy breasts.