I *can* sleep anywhere, most of the time, but generally choose not to. Never been able to sleep on my back, even after night shift. If I'm trying to stay awake to get back onto a days sleep pattern I just find a sofa or something and lie on my back, works perfectly. Normally sleep on either my side, in the style of any of the aforementioned chimps, or on my front. Have to say the comfiest sleep I ever had was actually in a hammock, although that may have had something to do with the sun/beer combination I'd been enjoying at the time As to the original question, yes I think it's quite possible for human beings to sleep without cushioning, however I don't see any reason to. I suspect it would probably lead to musculo-skeletal disorders in some cases, given how much longer we tend to live then we would have when sleeping rough all the time, but perfectly possible.