I read an interesting reply recently on Reddit about this. Essentially, the poster says that in what you refer to as Neolithic times, women with large bellies, ample bosoms, and wide hips were generally women who were healthy and had access to food and the ability to get it for themselves. Men were biologically attracted to this display of "wealth".

Contrast that to today, where having wealth means having the disposal to hire personal trainers, time to exercise, and not having to eat processed foods. Women of wealth will typically go to lengths to look a certain way (tan, skinny, etc.). I know that wealth is different from being in good reproductive health, but being wealthy definitely plays an important role in determining mates. As the definition of wealth changed, so did men's interest in women.

Sorry about the lack of citations, but it was a while ago and from a secondhand source, so I would take it with a grain of salt. It does sound reasonable though.