By Dr. Cora Angier Sowa. Here's her summary:
Ancient and mediaeval epic tales like the Iliad and Odyssey, Gilgamesh, and the Chanson de Roland had plots made up of modular elements taken from traditional themes or story lines. Among these themes were The Hero's Life, The Journey, The Marriage of the Fertility Goddess, The Epiphany of a God, and Invention of Technology. These same themes, with the same panoply of elements, as outlined in the following essay, have persisted through many civilizations, and can be found in our own movies. Such survivals appear not just in self-conscious imitations of Greek and other myth like O Brother Where Art Thou (which purposely adapted plot elements from the Odyssey) but in movies like The Godfather, Jaws, The Phantom of the Opera, and even Lassie Come Home. The same characters also recur in the stories, like The Goddess Across the Water, the Two Helpers, The Substitute Who Dies, and The Trickster-Inventor. We act out the plots of our myths, too, as can be seen in some poignant moments from our space program.
Full text at her website, Minerva Systems (she's also a computer programmer).