What are the motifs in The Evolution of Calpurnia Tate by Jacqueline Kelly?

One recurring theme or motif in the novel, The Evolution of Calpurnia Tate, is evolution. This motif is illustrated through Callie's interest in science and Darwin's theory of evolution, Callie's personal evolvement over the course of the novel, and the changes (evolution) taking place in the world during this time period.