A scientist, teacher, and environmental theorist, Shepard moved beyond the factual realm of biological science to expand upon the nature of human behavior and its roots in the natural world. He was a prolific writer who have had a profound influence on a variety of contemporary thinkers.

In his introduction to The Subversive Science: Essays Toward an Ecology of Man, edited with Daniel McKinley, Shepard discussed the reluctance of modern (as opposed to primitive) people to view humanity as one element of the whole of creation. Instead, humanity is wrongly seen as the singular focus or the intended culmination of creation, thereby denying the role played by all other life forms in the evolution of humankind. Shepard suggested this need to dominate has led to physical and mental separation from the whole, resulting in innumerable problems...