The idea of mass extinction as part of our regular vernacular is a relatively recent event - likewise its importance to the process of evolution. The cultural and somewhat scientific icon of extinction has always been that of the dinosaurs. With the announcement over 20 years ago by the Alvarez team of 'proof that an extraterrestrial object struck the Earth at the end of the Cretaceous Period, all eyes have looked skyward for follow-up data. Not so for Vincent Courtillot, who has argued for more earthly causes for over 15 years. In Evolutionary Catastrophes, he lakes the reader back over the progress of these developments in the extinction discourse and provides a personal view of a different, sometimes solitary, path taken. Courtillot has argued that the volcanic events resulting in the Deccan Traps of India should also have equal, if not top, billing as the cause of the climatic changes 65 million years ago. 'It was hard to see this [the timing and intensity of the volcanic emissions] as only a coincidence' (p.56) with the terminal Cretaceous extinction event. Yet through the debates, described in polite and honest detail by the author, and the growing awareness of the geochemical signatures that mark the sources of terrestrial and extraterrestrial events, Courtillot's work has unpredictably branched to broader geological events. 'it is clear', the author states 'that rarely, but sharply, the internal dynamics of the globe affect the evolution of species' (p. 141). In fact, over the last 300 million years, ten traps have been identified. Of these, seven coincide with mass extinctions. Although it appears that the famed Cretaceous event has an extraterrestrial component, the sudden outburst from within of ash, aerosols and gases can obviously have local, regional and global consequences.
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