The Introduction lays out the theoretical stakes of the work as a whole. It opens with a critical evaluation of the work of acclaimed geneticist Spencer Wells, whose 2002 publication The Journey of Man has helped frame the now-standard interpretation of human evolution and migration from a single set of ancestors out of Africa. Wells's account of human evolution reveals the epistemic authority that modern genetics has obtained on the question of race and human beginnings. It is argued that contemporary biologists inherited this authority, however, from their Christian intellectual ancestors, who provided modern scientists with a cache of interpretive tools and assumptions that proved useful for narrating the development of human life and constructing theories of racial difference believed to supersede all previous accounts of human origins. After laying out the theoretical ground to be covered, this introductory chapter provides an overview of the chapters that follow.

Chapter 1 examines the thought of the eighteenth-century ethnologist Johann F. Blumenbach, whose 1775 work On the Natural Variety of Mankind is often represented as precipitating the secular turn in the modern study of race. The chapter offers an alternative account of the intellectual ancestry alive in Blumenbach's racial theories by recovering the Christian sources of his thinking. Political and philosophical anti-Judaism prevalent in late eighteenth-century Germany, the transformation of the Protestant Reformer Martin Luther into a pioneer of German national identity, and the anti-Jewish writings of Johann David Michaelis in the emergent field of biblical geography at Göttingen University were all crucial political, religious, and intellectual influences during the time Blumenbach developed his racial theories. Drawing on the notion that the epistemological origins of racial science are fundamentally mongrel, this chapter argues that Blumenbach's racial theories were not an expression of pure, untainted, secular rationality.

Chapter 2 analyzes scientific criticism leveled against the theory of common human descent beginning in the 1830s. It focuses on the thought of Josiah C. Nott, a southern physician, early epidemiologist, and major figure of the so-called American School of Ethnology. Nott claimed that humanity's common origin, or monogenesis, was an unscientific belief and a mere carryover from when natural historians were indebted to Christian ideas about nature and human life. Thus, he attempted to establish an account of the history of human racial groups that moved beyond the constraints of the narrative recorded by Moses in the Bible. Despite these secular aspirations Nott ultimately failed to offer an account of race that stood independent of Christian thought. The case of American polygenism illustrates the degree to which modern racial science is indebted to a religious intellectual history it has attempted to deny and supersede.

Chapter 3 explores how polygenist carryovers emerged in early twentieth-century medical and public health studies on the links between race and disease. This persistence further embedded ideas about race derived from Christian intellectual history into the methods and reasoning of modern scientists and public health researchers. In the early twentieth century, the concept of biological determinism—the idea that the fixed biological makeup of a racial group determines its members' health, behavior, and intelligence—reoccupies the epistemic space once filled explicitly by a theological view of nature. This chapter also introduces the work of the African American physician, ethicist, and social hygienist Charles V. Roman, who departed from the racial logic of his time. Roman stressed instead that the idea of common human ancestry should push public health researchers to think more critically about the social and environmental factors shaping health outcomes and black susceptibility to disease.

Chapter 4 examines how concepts about racial ancestry and the ontological uniqueness of human life from Christian intellectual history have historically informed scientific research on the Neanderthal. These Christian forms are at play in the sequencing of the Neanderthal genome and the unanticipated discovery that mating occurred between this hominid group and modern humans around forty thousand years ago. Geneticists claim that evidence of this encounter is found almost exclusively in the genomes of Europeans and Asians. This chapter also shows how scientists in both the nineteenth and twenty-first centuries deployed notions of distinct continental groups and fixed racial traits to draw conclusions about human-Neanderthal relatedness. In both centuries, concepts and reasoning strategies implicitly divinize nature while also framing human ancestry into three original groups that represent the reoccupation of the story of Noah's three sons, Shem, Ham, and Japheth, into contemporary algorithmic representations of human genetic ancestry.

Chapter 5 provides a summary of the major claims of the book. It also explains how the conflict thesis for representing the relationship between science and religion fails to capture how Christian intellectual history has been key to the formation of the race concept in modern science. Citing recent data from a 2015 Pew Research Survey, this chapter argues that the conflict thesis remains a fixture in the minds of Americans, which has consequences for shifting public perceptions about the assumed secularity of the scientific study of race. It closes with a call for recognizing that the scientific study of race is involved in providing a solution to the existential dilemma of defining what it means to be human. This solution is neither value-free nor detached from the cultural and religious inheritance that has fastened itself to the work of Euro-American scientists who study race.