Galapagos explores Nature Versus Nurture as it explores ideas about evolution, charting the development of humanity across a million years. From Leon’s perspective, the novel shows how the species evolves from the familiar, depressing time of the end of the 20th century to a time a million years later, when humanity is a fur-covered, semiaquatic mammal. In presenting this development, Leon seeks to ask whether nature or nurture is more important. In other words, he tries to determine whether people are genetically predisposed to act in a certain manner—or whether their characters and behaviors are a product of their environment. The nature argument suggests that people are simply born a certain way and are unlikely to change, while the nurture argument suggests that people are shaped by the environment in which they’re raised.

A key character in Leon’s investigation into nature versus nurture is James Wait. Leon can look into the characters’ pasts and, when he looks into Wait’s, sees a tragic upbringing. Wait is the product of an incestuous relationship, so many people in society view him as the immoral result of inbreeding. His genetic history, in society’s view, is abnormal, suggesting that some degree of immorality is encoded in his DNA.