Alright, here's my scientific go at it:
Attraction in general comes from what is biologically perceived as better to raise kids. Therefore, the general attraction to the mammary glands comes from the notion that larger breasts=better-fed children. A larger bottom implies larger & stronger hips, meaning that the baby and mother are more likely to survive birth.
That actually makes a lot of sense. A cousin of mine (also petite, like my mother and sister) almost died from giving birth to her first child -ever since, she and her fiance have opted for adopting kids.
In a way, the smaller a woman is, the less margin for error she has when she is giving birth.
Like I said, it's all about waist-to-hip ratio, not anything brute force about how big the individuals are themselves (
Singh, 1993;
Singh & Young, 1995;
Henss, 2000). In any case, like I apparently hallucinated saying earlier, despite my attempts to find any scholarly work about breast/butt size, I wasn't able to. I suspect this might be because, unlike waist-to-hip ratio, it's hard to make boob/butt size something that people won't explicitly evaluate when deciding whether someone's attractive.
