The idea that extinction is a bad thing and diversity a good thing seems self-evident to us. But, by surveying more than two centuries of scholarship, science historian David Sepkoski shows that this was not always the prevailing belief. Rather than a book discussing mass extinction, Catastrophic Thinking is more meta than that, discussing how we have been discussing mass extinction. So, we have an interesting premise, but also an interesting author because—bonus detail—the work of his father, J. John (Jack) Sepkoski Jr., was instrumental in recognizing the Big Five mass extinctions. I could not wait to get to grips with this book.
Extinction was long considered a theological non-starter in Western philosophy; God’s creation is perfect after all. But once some naturalists finally accepted fossils for what they were, extinction became a possibility and this is where Sepkoski starts to chart our thinking on extinction through four transitions. In the Victorian era extinction was initially seen as a regular process that was the logical consequence of natural selection. After the trauma of World War I it morphed into a cyclical process, extinction being the result of species reaching the end of their “life span”. The invention and deployment of nuclear weapons and the shadow cast by the Cold War prepared the way for a more catastrophic interpretation so that when the Alvarez team proposed a fiery end to the reign of the dinosaurs, it found fertile ground in the popular imagination. And that concern gave way to considering extinction as a ongoing slow-motion biodiversity crisis.
This exceedingly brief and simplified outline can barely do justice to the many subtleties and insights that Sepkoski unearths. Catastrophic Thinking stands out for the depth of its scholarship; next to careful reading of books and journal articles, he has interviewed some key figures and dives into private correspondence held in archives. Sepkoski previously wrote Rereading the Fossil Record in which he charted the rise of palaeobiology as a discipline, and he draws on that book here. For palaeontologists and evolutionary biologists there are thus plenty of fascinating science history details.
For example, how Charles Lyell’s uniformitarian views of slow and gradual change won out over Georges Cuvier’s ideas of periodical catastrophic revolutions and went on to influence Charles Darwin’s thinking. Sepkoski is at pains to explain that the uniformitarianism-versus-catastrophism dichotomy is itself an oversimplification and was only one of the concerns, another being the question of intrinsic versus extrinsic causes of extinction. Somewhat later, the rise of cyclical thinking questioned Darwin’s assumption that the fossil record is very fragmentary and incomplete; perhaps the sudden disappearance of species was not an artefact after all.
“Catastrophic Thinking stands out for the depth of its scholarship […] For palaeontologists and evolutionary biologists there are […] plenty of fascinating science history details.”
This, in turn, paved the way for catastrophic thinking when the question of the fossil record’s completeness got an empirical boost in the 1950s through the work of first Norman Newell and later Sepkoski’s father on fossil marine invertebrates. As Sepkoski explains, their remains are so plentiful, several orders of magnitude richer and more complete than vertebrate fossils, that they are considered to offer a true and reliable picture of the history of life. And this record was revealing five big mass extinctions and potentially many other smaller ones. This raised questions whether natural selection and Darwinian evolution might be suspended during such crises, which David Raup pithily summarized in the title of his book Extinction: Bad Genes or Bad Luck?
The catastrophic school of thought, too, planted the seeds for the next transition. After all, mass extinctions reveal themselves as a rapid and precipitous drop in biological diversity. Already in 1992, none other than E.O. Wilson argued that biodiversity loss due to human-caused habitat loss and climate change are plunging the world into a sixth mass extinction. This concept was further popularised in 2014 by Elizabeth Kolbert although, as Sepkoski explains, there is some pushback from palaeontologists.
I could go on, but the biological story is only one side of this book. Catastrophic Thinking is part of Chicago’s science•culture series which contains books examining the intersection of the two. A central theme for Sepkoski, reiterated throughout, is how he sees science and culture as inseparable: “[…] cultural and biological values surrounding extinction mirrored and reinforced one another” (p. 84). Attempting to disentangle the two is a fool’s errand that will confront you with “a serious chicken-and-egg problem” (p. 287). At any given historical period, science and culture combined to form an extinction “imaginary”, an academic term he borrows from art. This may sound somewhat abstract but once Sepkoski gets underway it quickly becomes clear what he means.
“A central theme for Sepkoski, reiterated throughout, is how he sees science and culture as inseparable: “[…] cultural and biological values surrounding extinction mirrored and reinforced one another“”
So, Darwin’s ideas were used to justify imperialism, slavery, and racism—the “extinction” of “primitive” tribes encountered by colonialists being perceived as a regrettable but also inevitable result of the strong vanquishing the weak. Sepkoski emphasizes how we cannot simply blame Darwin for this, even though his ideas fed off, and in turn fed into, Victorian-era culture and politics. The later cyclical thinking echoed contemporary historical accounts that emphasized the cyclical rise and of fall of civilizations. The idea of dinosaur-extinction-by-asteroid hit a collective nerve, especially when Carl Sagan and others made direct links with the potential consequences of a nuclear winter in case atomic weapons were to be used. And most recently the idea of biological diversity as a sign of a healthy planet has been applied to culture, as exemplified by the UNESCO Universal Declaration on Cultural Diversity.
The only nitpick I have is regarding the supposed periodicity of mass extinctions, roughly every 26 million years, that Sepkoski mentions several times. Without going into the nitty-gritty, he leaves out two recent books arguing in favour, but, more importantly, he does not mention that this idea is not widely accepted. Raup, who originally proposed it together with Sepkoski’s father, wrote in his 1999 afterword to The Nemesis Affair that “[…] the periodicity question is firmly planted on the back burner.” and is not supported by the consensus (p. 217). Indeed, Ted Nield wrote in 2011 that “the theory seems unable to go further. […] The jury awaits further evidence.” (p. 141), while Michael Benton added in 2019 that “The debate rumbles on […] but most have abandoned the idea of periodicity” (p. 264).
Leaving aside that minor detail, I found Catastrophic Thinking a thoroughly enjoyable and convincing read. My impression is that there has not been a reflection of this kind, at least in book form, since The Mass-Extinction Debates in 1994. Catastrophic Thinking presents a far wider and more inclusive take on the topic though and is positively bristling with fascinating insights. Obviously, this is a must-read for science historians, but palaeontologists and evolutionary biologists interested in the history of their discipline can also safely pick this up. Furthermore, thanks to the compelling arguments and accessible writing, this book should appeal strongly outside of these disciplines to anyone with an interest in palaeontology, evolution, or mass extinctions.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
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