Insomnia is a very common problem, and sometimes a very frustrating and persistent one.  But what if our expectations of an uninterrupted 7 or 8 hours of sleep is unrealistic?  What if a night of sleep for 4 hours, wakefulness for an hour or two, and then more sleep for 3 hours is how most of humanity slept before artificial lighting? In a provocative article last year in Applied Neurology, Dr. Walter Br...