Men need to be needed. They need to feel relevant. They need to think that they are important.
Agreed, though I would change "men" to "humans."
Throughout the majority of human history, heterosexuality has contained a quality of male dominance over females. This element was established based wholly on the physical differences between human males and human females. Specifically, the fact that males tend to be bigger, stronger, faster, etc. than females. In our proto-human past, in our hunter-gatherer past, and in our pre-nuclear past, men did indeed rule the world. Enemies were well-defined, and men did most of the providing, creating, inventing, and protecting. In those days, a man's strength was unquestionably greater than that of a woman. That dynamic made it desirable for a man to have "as much woman" as he could handle. An example of this was the Reubenesque beauty--a young, pampered, and well-fed woman...supported by a rich and powerful man.
I would say your history here is a little reckless. I'm not going to bother to google which gender did more of the providing "in our hunter-gatherer past," though I'd be willing to bet the tribes relied on gathered foods about as much as they did hunted ones -- hence the presence of both in the name. As for "protecting," no male would live to be old enough to hunt if females weren't doing their share of the protecting. Creating and inventing? Hard to say since pre-history is, by definition, pre-history.
And of course 16th c. Peter Paul Rubens, and those who admired his paintings, did not live in a hunter-gatherer society. But then you say "pre-nuclear"? So maybe you mean everything up until 1945. And here, as when you say "well-fed," you're onto something.
In the post-modern world, with all of its technological advancements--women have achieved a much greater level of parity with men. As such, women have less of a need for men. Some might say that women don't really need men at all. Yet the primal urge men have for being needed persists. The male dominance over females has not gone away. But because women can now compete with men on a male level in our society, "as much woman" is a smaller, more frail, more dependent package than it used to be. That's "as much woman" as today's man thinks he can handle.
Men's preferences don't solely dictate fashion. Especially not straight men's preferences. If they did, fashionable clothes would look A LOT different.
But actually, this body trend has much more to do with economics, class and snobbery.
Throughout most of human history -- a period, as Milo points out, that dates from our proto-human past through Rubens' 16th century to the nuclear age -- it was hard to get enough food to be fleshy. Hunter-gatherer societies were often at risk of starvation, among many other threats. The most successful hunters AND GATHERERS (i.e., the highest-status members of the society) would of course be least likely to be thin. Jumping ahead to Rubens' time, same thing. The nobility could afford plenty of food and leisure and get chubby pretty easily. Look at Henry VIII. But the average peasant? Not so much; work was physical, food was scarcer, and if a crop failed one year those peasants would get awfully skinny. Jump ahead to everything up until mid-20th century America. Before the New Deal, if you were out of money and food you were just about out of luck. You would rely on charity, maybe, and scrape by. Read Erskine Caldwell's "Tobacco Road" for a harrowing account of what life was like for the rural poor in the '20s and '30s: It includes scenes of hungrily devouring scavenged radishes, trying to sell gathered branches as firewood, etc.
Now to post-WWII America. Suddenly, thanks to the New Deal, even most poor people can usually get food. And thanks to a bunch of other trends in post-war society, food is abundant -- especially cheap and fattening food, like junk food and fast food. Obesity increases, along with diabetes, heart disease and all that other stuff. Suddenly, for the first time in all of human history, people are more likely to die of
too much food than too little.
But who is best able to avoid the health hazards of excess food and obesity? Once again, it's the rich. They have both more money and leisure time -- they can afford the gym memberships, the private trainers, the neighborhoods with running and biking trails, the fresh vegetables, the cooked-from-scratch meals. The poor often can't move about freely in their neighborhoods and have a harder time accessing healthy foods. And compared to the poor of the past, they are far more likely to work in sedentary jobs.
Fashion is usually, one way or the other, a reference to wealth, not sex. Excluding the odd self-consciously rebellious period ("grunge," hippies, which both involved conscious protest against status-quo excess), the look that is fashionable is what the rich can afford to look like. That's certainly the case today.
I know I've talked about suntanning trends before, but they operate on the same principle.
Chuck is right when he says that the women on the top row can't hold a candle to the women on the bottom row. But neither can their male peers hold a candle to the men who were peers of the women on the bottom row.
I think they're all fine. I don't judge women (or men) on their thinness any more than their fatness. Kiera and Kristen appear to be naturally thin people (and hooray to Kristen for not falling victim to the tanning trend, or maybe she's just careful to maintain a Bella-like pallor). Nicole, as anyone who spends any time in grocery store checkout lines or dentist's offices knows, used to be heavier. But who can blame her for wanting to meet her culture's standards for attractiveness? Most of America does -- though most subcultures in America aren't quite as fat-hating as Hollywood celebrity subculture. Put on a few pounds and you can expect to have your cellulite displayed on the cover of US magazine. As for Heidi, well, she does have those boobs. And so could any of the others here if they wanted to obtain them the same way she did.