My take on the theory of the origin of theater is that it originated completely out of human boredom. Before there was theater, there was storytelling - the only viable method of describing both fiction and nonfiction, other than constructing crude images (which took quite a lot of effort back then). The fact that storytelling was the only way of doing this became quite boring, and thus human nature took over and an effort was made to do anything to relieve that boredom, and the idea of telling stories through movement was brought into existence.