I find it hard to believe that human adults need as much sleep as some paleos advocate.I see folks say to get AT LEAST 8 or 9 hours a night and some reporting sleeping like 10 hours??? The only way I could sleep that much every night is if I was seriously ill or drunk every night. When I was job searching for like two months and slept all I wanted every night, I slept 6 and 1/2 hours like clockwork.
Edit: To answer the question, what I know to be true, but can't prove: a healthy adult doesn't sleep for 10 hours every night. There's something going on if you sleep that much day in, day out.