12 November 2022
This is a thoughtful volume on mass extinctions written for the novice. One thing I really liked about this book is that it was written very clearly from the mind of a skeptical scientist who is conscientious about explaining each step in his thinking while explaining fairly complicated, murky stuff for a lay audience. Hallam succeeds magnificently in defining ideas first, and only later attaching jargon or terminology to the concept. I really liked the organization of the book, too – rather than the typical march through mass dying through time (i.e., a chronological approach), Hallam organizes his discussion around the various proposed causes of mass extinction, and explores each of those in depth, citing evidence from the Big Five and other events in Earth history that both support and weaken the causative hypotheses. Going at it this way puts a different emphasis on thinking about mass extinctions – it’s a mechanistic approach rather than a historical whodunnit. I learned a lot, and particularly appreciated Hallam’s review of the literature on the role of sea level change in driving mass extinction events – something that often gets left out of the discussion when more attention-grabbing topics like ocean anoxia, large igneous provinces and (yes) meteor impacts are also in the mix. All told, it’s a solid, readable book. The one odd note was a four or five page digression into adventure stories while collecting data in remote corners of the world. Hallam’s discussion of the Pleistocene megafauna extinction really influenced my thinking on that issue. This was not one of the “Big Five” but still of keen interest to many given its unusual scope (large terrestrial species) and timing (shortly after humans arrived on various landmasses).