Specifically, how did we go from preferring women with very robust, curvy figures (Marilyn Monroe is the first, most famous example I can think of, but I'm sure there are many more) to preferring women with much slimmer figures? Understand, I'm not talking about personal tastes, but the tastes of "society at large," or the fashion industry, especially in regards to magazines like Cosmopolitan and all the others (in other words, the kinds of things that often set beauty ideals for girls that are growing up, like it or not.)
See, it doesn't seem to make sense. From a biological perspective, we should prefer women with wider hips (which normally means wider everything) and heavier frames, right? Wider hips mean more room for a developing fetus and a wider birth canal, reducing the likelihood of complications during birth. Obviously, modern medicine and the magic of the (survivable) c-section make this something of a moot point, but would our biological drives change in such a short amount of time as a safe c-section has been available? Additionally, heavier frames would mean a person that's more capable of surviving hardship and defending themselves against whatever, right?
Hell, wouldn't a healthy, maybe even slightly overweight (we're talking like ten pounds here, not obese) person be considered more attractive since being slightly overweight was traditionally a sign of wealth and status?
So where'd this preference for slim figures come from? Why'd it change?