The opening discussion between Howard and Melinda, two children, helps to establish the drama's fundamental frame of reference.  Howard talks about how Melinda, at one point, was a "worm" and how her father is a "monkey."  It is obvious that Howard is speaking from the position of evolution that has received so much attention in Hillsboro with the jailing of Bert Cates.  Howard's contention that Melinda was "a worm once" and that her father is "a monkey," are common expressions of Darwin's theory of evolution in a town that has banned it.  

This dialogue that features the presence of worms and monkey represents the basic discussion of evolution and the opposition to it that will underscore the drama.  Another reason for having the presence of the monkey and the worms to open the drama might be to convey how human beings, themselves, act in a way that is more reflective of animals than humans. This echoes Hornbeck's sentiment that humans "have not evolved" and that "Darwin was wrong."  The behavior of some of the people in the drama will reflect a tendency to embrace the animalistic conditions of survival than the "enlightened civilization" of human beings.  These images are present in the opening of the drama.