By profession a physical anthropologist, university administrator, and lecturer, Loren Eiseley was nevertheless an essayist by choice and a poet by temperament. His works include fifteen published volumes: Darwin’s Century: Evolution and the Men Who Discovered It (1958), a work of scholarship whose conclusion reflects his development as a popular essayist; six collections of popular essays; a biography of Francis Bacon; a loosely structured series of reminiscences published as an autobiography, All the Strange Hours: The Excavation of a Life (1975); three volumes of poetry; and a posthumous collection of essays, scholarly and popular, on which he had worked to establish the importance of Edward Blyth’s contributions to evolutionary theory, Darwin and the Mysterious Mr. X: New Light on the Evolutionists (1979). In 1987, a collection, drawn from Eiseley’s notebooks and including notes, poems, a fragment of a novel, and photographs of the Eiseley family, was published under the editorship of Kenneth Heuer as The Lost Notebooks of Loren Eiseley.

Confronted with temporary deafness in 1948, Eiseley turned from strictly scientific research to a form that had intrigued him even in high school, the nature essay. Out of a world of silence, a broad scientific knowledge, and a poet’s love of language, he forged a form that he would later call “the concealed essay, in which personal anecdote was allowed gently to bring under observation thoughts of a more purely scientific nature.” In his concealed essays, Eiseley blends personal experience and anecdote with archaeology, paleontology, and evolutionary biology, drawing on science to create art.

Before he began to write for a general audience, Eiseley had published a number of articles in scientific journals. Darwin’s Century, written concurrently with The Immense Journey, is an intensive study of the history of evolutionary thought that won the 1959 Phi Beta Kappa Science Award. The Immense Journey is informed by the knowledge and insights that Eiseley developed in the research for Darwin’s Century. Evolution is the central theme in both books, but in The Immense Journey Eiseley focuses on the human meaning of evolution. The essays were composed over a decade and reflect Eiseley’s knowledge as a physical anthropologist, an archaeologist who has done extensive fieldwork, and a historian of evolutionary biology, as well as his literary concerns with the human relationship to the natural world.

The Immense Journey is a collection that defies classification. The essays have been considered “natural history,” “popularization,” “popular science,” and “personal essays.” Eiseley’s chief concerns are nature and man and their relationship. His popular essays reflect his literary inclinations and his focus on the implications of evolution for humankind. Thus, science becomes the vehicle for humanistic insights.

The book consists of thirteen essays. It opens with two epigraphs—one by Henry David Thoreau on the need to look through and beyond nature, the other by William Temple on existence as revelation. In the first essay, “The Slit,” Eiseley re-creates his descent into a sandstone crevice that contained evidence of ten million years. In the last essay, “The Secret of Life,” he echoes the first essay’s downward journey, concluding that no matter how instructive the journey, science will never completely explain life, which contains mysterious powers. Between the first descent and the last, he considers the mystery of water, the human quest for the source of life in the ocean depths, the transition of life from water to land dweller, the importance of symbiosis as symbolized by the role of flowers in providing the food that would make possible the evolution of humankind, and speculation that the “man of the future” (as projected by science) has...