Why do these girls look so good in the summer?

I've long held the belief that human beings are at their attractiveness prime during the college age years. It seems like the majority of us have developed to adult form by this time and yet - depending on how badly the freshman-15 hits us - we are generally in better shape now than we will be as we age. Incidentally, at UVA they call freshman "first years" so does that translate to the first-year-15? Anyway, you might say we're at our physical peak. Or at least approaching it. After all, it's fairly well documented that a baseball player reaches his prime around his mid to late twenties (I can't wait to see what Pujols is going to do these next few years). Still, I can't help but wonder if this is all perspective. When I was in grade school I had a crush on many a young lass. But looking at girls of that age now, they clearly appear as children to me - and thus not attractive physically. At each age, I've always been attracted to the people in my age range. But I must admit, there are not too many 40 or 50 year olds that I have the hots for. Will this change? In another decade will I look at the 20 something crowd and think of them as children? even though they're technically adults? I suppose one way to find out would be to go around asking a bunch of older women if they find me attractive. One would think a young strapping lad like myself would have his share of admirers. But perhaps not. Perhaps they'll say to me - young man you have no grey in your beard!