Jouvet was the first to localize the trigger zone for  REM  sleep  and dreaming in the brain stem. In this book he provides a neurobiological and psychological analysis of sleep and dreaming. According to his findings, a dream  is the  vehicle  employed  by  an organism  to cancel or archive the day's experiences on the basis of a genetic program. Dreaming is a process that absorbs a lot of energy.
This theory would  also  solve  the  dualism  between  hereditary  and acquired  features.   An  hereditary component  is activated daily to decide how new data must be acquired.