Killer Instinct traces how scientists and science writers constructed, popularized, and debated human nature from the 1930s to the early 1980s. Over these 50-some years two rival conceptions of human nature, one as inherently aggressive and violent, the other as yearning for love and cooperation, competed for public acceptance and political influence and were in turn politicized and polemicized.

The first arc in Nadine Weidman’s account spans the first five chapters and presents different conceptions of human nature, explains their development, and then traces the dynamics of the debates surrounding them in published materials, both popular and scientific. Popular writing and scientific engagement with the public were critical aspects of these debates. Konrad Lorenz, Robert Ardrey, Ashley Montagu—all of them were aware of their status inside, outside, or on the periphery of science and how that status could be used to attract and persuade audiences. Weidman portrays Lorenz as a professional scientist encouraging amateurs to engage with animal behavior through the power of observation, Ardrey is depicted as an amateur proudly proclaiming that his outsider status conferred precisely the clarity that science was lacking, while Montagu is shown as playing an uneasy role as the public face of anthropology without an academic home in the discipline for much of his career. By not limiting her analysis to scientific publications, Weidman draws a rich picture of how the human nature debate played out in the public sphere.

Weidman offers exceptionally clear and lucid explanations of the scientific ideas and background motivations of her actors, such as Lorenzian instinct theory, but her analysis truly shines when she looks beyond individual scientists and shows their interaction within and across the pre-conceived camps of the debate. This focus on interactions pays off in big ways—showing that the theories and ideas of her actors did not develop in isolation—and in small: we learn that Montagu and Ardrey commiserated about their role as non-academic science popularizers while engaging in a heated public debate about the nature of aggression, for example. The first chapter about Lorenzian ethology is based only on his published materials, but when she introduces Anthony Storr, a British psychoanalyst who shared Lorenz’s outlook on aggression as productive, and delves deeper into his correspondence with Lorenz in the second chapter, she unlocks the full power of her interactionist perspective and explores hitherto lesser-known actors and relationships in the historiography of the aggression debates. The third and fourth chapters continue this approach as Weidman presents the intellectual networks that surround two of the most prominent contestants and positions in the debate: Robert Ardrey’s argument arguing that weapons and the “killer instinct” were at the center of human evolution, and Ashley Montagu’s view of a cooperative drive shaping human nature.

The fifth chapter concludes the first arc on the aggression debate from the mid-1960s to approximately 1976 and deftly combines public arguments and private correspondence. Weidman shows how the debate mixed scientific theories with public and political positioning, carefully delineating the positions taken by individuals during the debate and examines how the dynamics of the debate influenced their positions in return. She avoids the trite explanation of yet another round of the nature-nurture debate and instead concludes that the nature-nurture narrative resulted from strategic rhetoric rather than accurately representing the true positions of any involved party. Weidman attributes these misrepresentations to various factors: the dynamics of the debate, the construction of “strawman” arguments, and participants abandoning the complexity of their original positions to conform to the increasingly hostile tone of the debates. Scientific polemics and politicization are intricately intertwined in Weidman’s reconstruction of how the aggressionists positioned their theory as a bulwark against behaviorism and communism. Killer Instinct also highlights that the liberal alliance against the aggressionists advocated for a human nature rooted in love and cooperation, yet refused to relinquish the notion of a gendered human nature and its associated political and social model. Weidman argues that the debate ended in a stalemate. Its legacy was establishing a political framing with extremist positions in the public sphere that was hard to escape in future debates.

The second arc about the sociobiology debate continues this skillful use of the full breadth of historical material, including archival finds, lesser-known publications, and landmark monographs. Spanning two chapters, it covers the sociobiology debate in its connection to pop-ethology as well as a group of feminist critics of sociobiology, the Genes and Gender Collective, that has not received much historical attention thus far.Footnote 1 Weidman adds significantly to the existing historiography by showing nuances and ambivalences within the two well-established camps of the sociobiology debate. Often the differences between Wilsonian sociobiology and pop-ethological aggression theory are plastered over with the nature-nurture narrative. But in the sixth chapter, Weidman fixes this oversight. When E. O. Wilson arrived on the scene it was as a professional scientist, demarcating his sociobiology from the dilettantism of pop-ethology. But while E. O. Wilson initially sought to distance himself from earlier iterations of pop-ethology with the publication of Sociobiology: The New Synthesis in 1975, Weidman demonstrates how the dynamics of the debate pushed Wilson to align quickly with Ardrey and the others. In the other camp, the historiography of sociobiology’s critics thus far has been dominated by the critique advanced by the Sociobiology Study Group (SSG). Again, Weidman adds complexity as she illustrates how feminist critique was marginalized within the SSG—a frequent issue within the predominantly white and male New Left movement. Weidman excels in dissecting the various critiques, demonstrating that the critics were not a monolithic bloc. Her analysis here could have even been expanded to cover other lines of criticism of sociobiology such as those by Donna Haraway and Donald Campbell, or the critical perspectives within the biological disciplines. Exploring the history of these debates beyond the nature-nurture narrative reveals a deeper history and allows for a more nuanced understanding of the aggression and sociobiology debates, one that proposes that the positions of both camps were not foregone conclusions but shaped by the debate itself.

This is also true for the leftist position on the existence of human nature. When Weidman characterizes Montagu as a biological essentialist whose understanding of human nature was rooted in love and cooperation (a viewpoint strategically abandoned during the aggression debate in favor of a blank slate, nurturist position), she contends that by the mid-1970s, the concept of human nature had been abandoned by the left: “The concept of a biologically based human nature became the province solely of those assumed to be racists and conservatives” (p. 227). I want to add that the inner dynamics of SSG contributed to this surrender of human nature. As early as December 1975 the group set out to “develop a positive position on the question of human nature,”Footnote 2 but members found it difficult to openly disagree with the anti-human nature stance that had developed throughout the debate. The meeting minutes of the SSG show that the group continued to grapple with defining its stance on human nature until the late 1970s, even drafting a manifesto on human nature in 1977. The manifesto itself was fiercely debated within the group but never widely distributed or published. Over time the lack of a positive formulation of human nature by the leftist critics turned into the denial of the existence of a biological human nature.

Killer Instinct provides an excellent analysis of the public debates about human nature, delving deeply into the dynamics between individual actions, collective endeavors, and public positions. Weidman enriches our comprehension with layers of complexity and nuance while managing to craft a coherent and convincing narrative. Her pioneering work offers a novel perspective and paves the way for future research.