I read an blog post online observing that cats and other animals tend to be diurnal and wondering if it would be possible for humans to act the same. Personally I've always felt most of society acts like birds with blankets over their cages in reverse, relying on artificial light to such an extent that we loose touch with nature's patterns. I'm very sunlight oriented, to the point that I love daylight's savings times, because it makes the clocks match what the outside is doing. I attribute a lot of this meshing of schedules to the fact that I have never used dark curtains in my bedroom. As a kid I had yellow curtains and for the last few apartments I've either not bothered at all or had sheer white ones. That means when the sun gets up, I get up too!