Here's a scene that takes place everyday, in every city.
A man is walking down the street, minding his own business, and then from a distance, he sees an attractive woman, or a woman with an alluring walk. As they approach each other, he checks her out from head-to-toe (or at least from head to waist), awaiting the fleeting moment when they will come face-to-face. When she passes him, she grants him a clear view of her butt as she walks by.
The man doesn't have to look - but he usually does. Why is that? Is it instinctive? Or habitual? Is it wanton lust? Or just male curiosity?
Perhaps the answer to these questions will vary among men, but all will agree on one thing: there's just something about a nice butt that we find very sexy. When I say "nice," I'm allowing for variations in definition here.
Some men like small, perky butts. Some like voluptuous, heart-shaped butts. Some men like firm, athletic butts. Some men like petite, model-like butts. Others like butts that are round, but not obtrusive. Many like shapely butts that are in proportion to a woman's figure.
There are some who don't particularly care about butts at all (they are in the minority). Then there are those on the opposite end of the spectrum who like big, even gargantuan butts.
Speaking of big butts, they tend to create a more pear-shaped body, which according to scientists makes better use of insulin, which can offer protection against type 2 diabetes and heart disease. In addition, extra "padding" is still believed to facilitate pregnancy.