According to naturalist author Mary Ellen Pitts, in the "seminal" "Darwin's Century", Eiseley was studying the history of evolutionary thinking, and he came to see that "as a result of scientific studies, nature has become externalized, particularized, mechanized, separated from the human and fragmented, reduced to conflict without consideration of cooperation, confined to reductionist and positivist study." The results for humankind, "as part of the 'biota' – Eiseley's concern as a writer – are far reaching." In the book, his unique impact as a thinker and a literary figure emerges as he reexamines science and the way man understands science. She concludes that, for Eiseley, "Nature emerges as a metonym for a view of the physical world, of the 'biota,' and of humankind that must be reexamined if life is to survive."