How should humans sleep?

Last week, I went to the Annual Associated Professional Sleep Societies (APSS) Meeting in Minneapolis. Although there wasn't much presented in my specific line of work, I really enjoyed learning about the broader, human-based perspectives on sleep. One of the pre-meeting workshops I went to was called the Anthropology of Sleep. The speaker made the argument that how we sleep is a cultural phenomenon, and varies widely in populations throughout the globe. For instance, most of us associate sleep with: quiet, comfortable, bed, relaxing, soft bedding, etc. But there are many people that sleep on the floor in crowded rooms (for protection), without covering or even clothes (to prevent bug infestations), with thin walls separating them from wild animals. Although we would probably have a difficult time acclimating to their sleeping habits, it's likely that they wouldn't enjoy ours, either. (For instance, the speaker explained that it was inconceivable for them to sleep in isolation.)

The workshop and an article Dro sent me got me thinking about how we may have evolved to sleep optimally. In this article published by NPR, the writer introduces a study that found subjects who napped in a rocking apparatus had seemingly better quality sleep than those that did so in a stationary bed. The rocking motion was intended to mimic a gently swaying hammock. Where did the idea of sleeping on pillow-top mattresses come from, anyway? I would be interested to see if sleeping on the rocking bed for many consecutive nights continues to appear beneficial. It would also be cool to compare sleep quality in other environments - on the floor, out in the woods, on a boat, and so on. Since quality sleep is increasingly hard to come by for many of us, an evolutionary approach may not be a bad idea.