Eiseley's writing often includes his belief that mankind does not have enough evidence to determine exactly how humans came to be. In "The Immense Journey", he writes, "... many lines of seeming relatives, rather than merely one, lead to man. It is as though we stood at the heart of a maze and no longer remembered how we had come there." According to Wentz, Eiseley realized that there is nothing below a certain depth that can truly be explained, and quotes Eiseley as saying that there is "nothing to explain the necessity of life, nothing to explain the hunger of the elements to become life. ... " and that "the human version of evolutionary events perhaps too simplistic for belief."