Annie is a self-sufficient woman who quietly manages the surreal reality of her lover transforming into earlier evolutionary forms. She continues her daily job while keeping his condition a secret from friends and colleagues who eventually stop calling. As her partner regresses physically, she transitions from an equal romantic companion to a solitary caretaker.

Ben is Annie's boyfriend, a man heavily burdened by his anxiety over human progress and the modern world. Before his physical regression begins, he expresses frustration that humanity focuses too much on intellect at the expense of emotion. His deep melancholy regarding civilization heavily influences his worldview.

The Biology Professor is an aging, disgruntled educator whom Annie consults for scientific context regarding her situation. He acts as a representative of rational society, showing reluctance to provide his expertise on evolution unless he receives payment for his time.