The Evolution of Dreams

How does dreaming evolve?  In what crucible of trial and error is dreaming tested?   Where is the DNA advantage in my children because I dreamed?

This is a good question.  There must be a specific way dreaming affects survival. Dreaming occupies hours out of every day of my life, comes in pulses at 90 minute intervals and is generally forgotten, perhaps designed to be forgotten.  It shows up in other mammals as anyone who has watched a sleeping dog's twitching toes knows. Why is something that is somehow essential, yet is essentially forgotten -- so prevalent?  What survival advantage accrues to dreaming?  Why do some other animals have REM sleep?  In what crucible is their dreaming tested?

Man has always been interested in dreams, wondering what they mean. Perhaps they mean nothing apart from being a form of behaviour.  The activity of dreaming is important and the dreams don't mean much in themselves.  Having recorded a couple thousand of my own dreams, I feel comfortable with that observation.  As Marshall McLuhan said, "The message is the medium".

Added:   The idea that I dreamed, sorted some stuff out, and later on survived because of it .... is not enough.  The actual REM event must reward the animal.