If you don’t think so, check out how many other female mammals have protruding mammary glands before the first gestation.
On the flip side, it can be argued that evolution among humans have selected for bigger wangs. Compare a human penis to that of a gorilla. Women, through the millenia have prefered to mate with men with bigger equipment, adding a mm here and there over the generations.
Well…they are a pretty good indicator of whether or not their owner is willing to have sex with you. If she allows you to play with 'em, odds are pretty good if not completely certain that the good times are about to roll. If she smacks you right away, well, you’ve saved yourself the hassle of dropping trou and finding out through more direct methods of inquiry.