David Sepkoski, Catastrophic thinking: extinction and the value of diversity from Darwin to the Anthropocene, Chicago: the University of Chicago Press, 2020.

With his latest book, David Sepkoski offers the reader the opportunity to explore the emergence of a particularly critical concept—that of extinction—and the intellectual contexts it has been involved in from the nineteenth century to the present day. The author investigates the scientific, political, and cultural dimensions of the discourse from which the main ideas of extinction have emerged. This is what Sepkoski calls an ‘extinction imaginary’. From a marginal catastrophic Cuvierian concept of extinction, which appeared rather contestable in the optimism of the Victorian era, to the concepts of diversity and stability as developed in the twentieth and twentieth-first centuries, the reader is taken on a very intriguing historical journey that raises a number of philosophical considerations. For instance, the inherent normative value of diversity is highlighted by the author and thoroughly examined in the ecological context of the current biodiversity crisis. Moreover, the author focuses not only on the historical context of catastrophic thinking in Western society, but also tells a universal story common to every human being pertaining to our anxieties about the future and the fear of our demise as a species. In this regard, Sepkoski demonstrates a profound understanding of human nature, of its failures as well as of its healing abilities, as he ultimately addresses the crucial question of the current Sixth Extinction.

David Sepkoski is the son of the prominent paleontologist Jack Sepkoski, who along with Dave Raup and David Jablonski developed the periodicity model of diversification in the 1980s and proposed the ‘Big-Five’ mass extinctions. Accordingly, he displays an intimate knowledge of palaeobiological mechanisms, and he describes the story behind this model, showing how it contributed to a more precise understanding of the nature of extinction, biological diversity, and diversification in the framework of Darwinian evolution. Scientifically, Catastrophic Thinking reinforces the threefold relation of extinction-diversity-evolution that constitutes a key element in our current understanding of the diversity crisis. Philosophically, the book considers how we should think of the relation between science and culture. And historically, the book traces the main developments that marked the discourse on extinction over the years, showing how popular thinking influenced—or even drove—the establishment of some scientific ideas.

Sepkoski’s historical investigation of the extinction concept begins with the first attempts by scientists to address the meaning of catastrophe in the nineteenth century. He shows that the French naturalist Georges Cuvier was one of the first scholars to propose a pattern of sudden, catastrophic episodes of geological change, which he called revolutions, based on the fossil record and the differences in geological data. Cuvier’s views were largely rejected by the scientific community of his time, as the vast majority opted instead for a uniformitarian form of gradual change that conformed to the general fixist idea of the ‘economy of nature’. This idea had been popularized by Linnaeus in the previous century in his Oeconomia Naturae of 1749. Although the causes of extinction were not generally addressed during this time, Giambattista Brocchi did propose some of the first ideas on piecemeal, gradual change, which suggested that the causes of extinction are intrinsic. In particular, Brocchi argued that species go extinct because they have natural life spans in the same way that individual organisms do.

Brocchi’s uniformitarian approach inspired the work of Charles Lyell as well as that of Charles Darwin, who also favored a gradualist account whilst claiming that biological and geological changes are due to external factors. Nevertheless, the idea of a ‘self-renewing’ balanced nature remained the main fundamental assumption, and diversity was taken for granted in line with the optimistic spirit of the Victorian era. In this way, Sepkoski argues that scientific positions reflected the cultural imaginary of the post-Darwinian nineteenth century. As such, they were used to justify and atone European imperial expansions and even racial extinctions, as competition between cultures was thought to be inevitable.

At the same time, anxiety for racial senility and degeneration began to rise in Western society in the aftermath of the First World War. In the third chapter of the book, Sepkoski underlines the emergence of a new extinction imaginary, one that he calls catastrophic or apocalyptic thinking. This imaginary is characterized by a newly experienced sentiment of cataclysm and apocalypse of an uncertain future that is often depicted in pseudoscientific works and ‘apocalyptic’ fiction. The author also indicates that, from a scientific standpoint, the first part of the twentieth century was characterized by cyclical theories of species life spans. In this regard, civilizations by analogy were considered to have predetermined life cycles.

The fear of senescence that arose among the Modernists of the early twentieth century developed into an increasingly substantial force after 1945, the moment when “the Atomic age had begun” (p. 127). The second half of the century is described by the author as ‘post-apocalyptic’ or ‘post-modernist’ in the fourth and fifth chapters. Sepkoski argues that this historical period is characterized by a collective fatalism that overwhelmed philosophers, writers, art-workers, and even scientists. He highlights that “[w]hat was new about the atomic age was not the idea of a final civilization-ending catastrophe, but rather the fact of its imminence” (p. 128) given that “formerly unthinkable events had become a reality” (pp. 130–131). These pessimistic feelings were also popularized by the scientific community in the form of hypotheses about mass extinctions. The Alvarez hypothesis of the asteroid impact and the resulting extinction of the dinosaurs, along with the alarming work of paleontologists and scientists such as the eminent astronomer Carl Sagan, led to the establishment of the reality of mass extinctions. Sepkoski addresses questions about the nature of these phenomena: he indicates that although they occur on regular timescales, they are still largely arbitrary. Particularly important in this discussion is the notion of ‘contingency’ (p. 223). Following this, Sepkoski declares that the development of modern ecology and the results of the periodicity paleontological model (pp. 175–189, 201–203) marked a turning point that reinstated a sort of optimism. Extinctions might be inevitable but they can also ‘give space’ for novel genetic experimentation and diversification in the course of evolution.

The book also highlights the fact that with the emergence of the concept of the ecosystem, all elements composing the biosphere came to be regarded as being tightly interconnected and rather fragile. The diversity of complex bioecological systems was increasingly endowed with a sort of stability, or equilibrium, that could be nonetheless disturbed irreversibly. The statistical significance of the great loss of biodiversity—the so-called ‘sixth mass extinction’—is discussed in the last chapter, along with a meticulous exposition of the difficulties that scientists and politicians face when trying to define precisely the notion of biodiversity and estimate rigorously the ‘slow-motion’ anthropogenic ‘catastrophe’ (p. 232). Following the rise of population genetics and ecological theorization and modeling, Sepkoski urges a new, more inclusive and less anthropocentric imaginary. Biological as well as cultural diversity needs to be re-evaluated as inherent normative goods in order to maintain the fragile complex systems of the planet healthy. In this ‘post-postapocalyptic’ context, the conservation discourse acquires for the author markedly utilitarian connotations.

Sepkoski concludes the book with an insightful discussion of neoliberalism and the concept of the Anthropocene that inspires a critical reconsideration of the evidently catastrophic attitude of humans. Indeed, Homo sapiens is ‘the dinosaur and the asteroid’ of our era. Finally, although the book was written before the outbreak of the COVID-19 pandemic, Catastrophic Thinking seems to provide a very appropriate framework in which to address current questions relating to the major challenges facing human beings on a global scale.