What is the theme in The Mound Builders by Lanford Wilson?

Permanence and impermanence are another theme in the book. The world of The Mound Builders is a cruel one. Not only do people betray each other, but the simple passage of time makes everything people do turn to dust. The constant action of the universe is to destroy, yet, even knowing this, the primal urge of people is to try to build something permanent. In the introduction to Lanford Wilson: Collected Works Volume II 1970-1983, Wilson wrote that even in the earliest drafts of the play, he realized that "at the burning heart of the theme was: Why do we strive to achieve? To build