I find it quite painful sleeping on the ground, but perhaps that's because i'm not used to it. Did previous humans such as hunter and gatherers just sleep on the ground without any padding for their body and head?
Not everyone has or uses beds and pillows even today. Is there a particular culture/region you're asking about?
Meanwhile, you'll find some examples of alternatives in here
You'll likely find more people better suited to answer this question at /r/askanthropology.