In the context of current concerns within the environmental humanities to challenge the idea that humans are somehow irreducible to nature, this article takes up the much-neglected history of the idea of human exceptionality itself. According to now familiar accounts, metaphysical assumptions about the unique status of the human are considered to have persisted—including to the present day—despite evolutionary contentions that the human should be understood as a purely physical being. Such, largely Christian and Cartesian, metaphysical notions of a human soul or mind doubtlessly endure. But in this article we consider the—largely ignored, yet now arguably more prevalent—idea that humans are exceptional because of their physicality. Here, then, we outline the emergence of the scientific claim that a uniquely human condition of nature transcendence is owed not to some immaterial quality of mind or soul, but rather to the distinctiveness of human anatomy. It was, we will argue, the body—and, above all, the head—which provided the basis of a modern attempt to establish that humans were creatures of a categorically different order from all other animals. More precisely, it was as human cultural differences were correlated with variations in the size and shape of the head that the human body, in its upright stature, came to provide an explicitly materialist—and, as we shall see, potently ethnocentric—foundation for the claim that human beings are exceptional. The modern idea of human exceptionality is thus shown to be based in large part on a scientifically dubious, and culturally specific, argument about the nature-transcendent quality of beings that walk upright. This is a particular form of humanist discourse that often forgets its own contingencies and instabilities, as well as its comprehensively violent inheritances.