What is the author's tone in Flight by John Steinbeck?

Although "Flight" is similar in tone and form to a folktale, it is written in a highly naturalistic style Naturalism is a style of fiction which developed from the ideas of Charles Darwin's mid-nineteenth century theories of evolution and natural selection. Naturalist writers, according to M. H. Abrams's Glossary of Literary Terms, "held that a human being belongs entirely in the order of nature and does not have a soul or any other mode of participation in a religious or spiritual world beyond nature; that such a being is therefore merely a higher-order animal whose character and fortunes are determined by two kinds of forces, heredity and environment."