All i think boobs are is an organ to generate milk for newborns. Until then,they're just useless blobs of fat and stuff :o
Well when your hormones are going crazy and stuff, your instincts try to find you the best mate. The girls perceived as "Hot" are generally in decent shape, good complexion, and big boobs (I'm sure there's other stuff). Anyways, these all relate to her genes. Evolution has caused men to seek out those that are healthiest and thus will yield offspring that are more likely to survive. Large boobs indicate that the woman will be capable of feeding the offspring. If the girl has tiny boobs, baby might starve. As such, boobs are perceived as hot. (I think that's it anyways...)
