In this book Nathaniel Comfort argues for the coexistence of two positions in eugenics from the late nineteenth century onwards, both of them fundamental for the existence of the current gene-based medicine in the United States: one genetic, the aspiration to achieve hereditary enhancement, and the other medical, the aspiration to alleviate suffering. He also demonstrates how these coexisting positions have alternated between dominance and subordination during that period, and how that depended on a complex relationship between different sociopolitical circumstances (Progressive era, Second World War, Cold War etc.) and several kinds of scientific development.

Comfort is quick to announce that his book is an alternative to the ‘master narrative’ of a present medical genetics originating from a ‘medical turn’ (p. x); a turn, that is, from eugenics as a politically based pseudoscience, as a bad set of ideas contaminating hereditary knowledge aimed exclusively at human improvement, to genetics, a science (a serious, apolitical one) intended to contribute to human health.

Critical for Comfort's resistance to this master narrative are his arguments concerning the coexistence of the genetic and medical positions in eugenics, which he tracks back to two lineages of thought on heredity represented respectively by Francis Galton and Archibald Garrod. Although interested in the consequences of disease, Galton's main objective was a society capable of modifying its own nature. For that he envisaged a population approach, based on the finding of ‘patterns in data’ (p. 27) from different sources such as questionnaires, twin studies and statistics. With these patterns in hand, the aim was to enhance the reproductive capacity of the ‘best stock’, which happened to be ‘idealized upper-class English intellectuals’ (p. 9). Garrod, however, was predominantly interested in the chemical analysis of disease in individuals, which he saw as emerging from the interaction between their genetic constitution and the environment. Although drawing conclusions from diseases running through families, Garrod's main concern was ‘the medical side of medical genetics’ (p. 27); that is, the avoidance of suffering by prevention. Galton's and Garrod's lineages, in Comfort's words, ‘have shaped the contours of medical genetics as it developed over the twentieth century’ (p. 2), ‘eventually dissolving into each other’ to produce what we nowadays know as ‘modern genetic medicine’ (p. 3).

Comfort expands themes that, although mentioned, had a tenuous treatment in Daniel Kevle's classic In the Name of Eugenics (1995). Comfort does, however, far more than that. He discusses in depth the many intricacies of the relationship between eugenics and the effects on human heredity of radiation (through mutations). This relationship was of primary importance for the geneticist Hermann Joseph Muller and others who, during the 1940s and 1950s (a period when atomic bombs became more available to different nations), conceptualized mutations as a threat to the eugenic ideal of a scientifically controlled human evolution. Comfort also discusses the importance of work on microorganisms that allowed the performance of experiments otherwise considered to be unethical in humans; Comfort cleverly labels this ‘genetics without sex’, the title of Chapter 7 of the book. In a similar way, he highlights the importance for genetic medicine of chromosome research and blood group serology for disease diagnosis during the 1940s and 1960s, the performance of cell hybridization experiments during the 1960s, the technical advances in academic hospitals during the 1950s and 1960s that made medical problems attractive for geneticists, and, above all, the irruption of recombinant DNA technology and gene cloning from the mid-1970s. For Comfort, this last, alongside its ensuing genome project, are key developments for, first, the consolidation of a ‘germ theory of genes’ – that is, the notion of a gene as disease agent; and, second, the present blend of the Galtonian and the Garrodian approaches, in which the divide between therapy and enhancement, between somatic and germ-line intervention (‘the last sacred moral genetic boundary’ (p. 244)), has become hazy and uncertain.

Comfort's move to disentangle a period, the 1930s to 1960s, which has been little attended to by earlier scholars, is well executed, and in the process he dethrones one of the key assumptions of the ‘medical turn’, namely that Victor McKusick was the father of medical genetics. In Comfort's words, ‘When McKusick began studying heredity, medical genetics was not merely extant; it was to those working in it, vibrant, with a history stretching back decades’ (p. 163).

Some weak points of the book are the late definition of the concept of the ‘germ theory of genes’ (although mentioned many times previously, its meaning is only clarified on p. 230); the taken-for-granted use of the concept of the ‘Progressive era’; and the lack of a chart containing all the roles and professional linkages of all the personalities that he discusses as well as the intensive crosstalk among the different institutions in which they worked, to help the reader to understand those many connections. That said, these small points are negligible compared to the book's main strength, which is the author's impressive work in identifying and closely following the lineages of scientific ideas held by the many professionals and personalities that have been part of the history of American eugenics and genetics from their modern inception in the late nineteenth century, through the twentieth century, to the present. All of this is based on the author's meticulous study of the published work, correspondence, memoranda and other archival sources of both well- and lesser-known geneticists, physicians, eugenicists and others who participated in the conformation of medicine in America and beyond.

All in all, The Science of Human Perfection is a well-researched and well-written book; not only is it a pleasure to read, but it is also a necessary and vital contribution to our knowledge of genetic medicine, and the social and political milieu where scientific ideas, past and present, arise and continue to develop.