You, sir, are way off base here. A certain male mindset trends to making “arguments from nature” for which there is no evidence and are, in fact, arguments from culture. Think about what you are saying here. You seem to be saying that fitness to breed male perceptions favor the seriously underweight (and undersized) female. Clearly this is nonsense. I could go on and lay out what the the seriously underweight female does signal to the male gaze but I’ll let you chew on the absurdity of what we are are asserting here for awhile as first steps.