Dreams and Religion

     The more I think about it, the more convinced I become that our ability to dream was one of the major factors in the development of religion.  Very often what we dream about are things that have happened in our lives recently.  So,the animal that attacked the caveman during the day, could visit him in his sleep, but where is it?  What if he had killed that animal during the day? Where did it come from? Is the animal's "spirit" or "soul" coming back for revenge?
     Guess there must be another world where these things live... thus the creation of the spirit world.  Also, seeing deceased loved ones in dreams could lead to the belief in afterlife and souls. 
     I know other animals dream. I've watched the REM activity in my dog as she lies on the floor. This is often accompanied by whimpers or growls. However, she has no real language to communicate this experience or the means by which to record it.  If she  did then maybe there would be a religion for dogs!