Whatever their faults, dinosaurs have enjoyed good PR over the years, with the result that their extinction has overshadowed a number of similar Armageddon-type events – four, to be precise, occurring at staggered intervals over a mind-bendingly long period. One – the late Devonian – took between 20 and 25 million years to play out; further evidence, if it were required, that the story of planet Earth is not the story of homo sapiens.
While less special-effects driven than the extra-terrestrial impact that did for the dinosaurs, what all these apocalypses have in common is ‘violent changes to the planet’s carbon cycle’. In fact, says Peter Brannen, carbon dioxide-driven global warming ‘is an experiment that the Earth has already run many times in the deep past’ with results that it’s worth taking note of.
As he assesses the various theories behind these different events, it becomes clear that life has always involved a race between extinction and speciation; if new species can evolve faster than extinction rates, then life wins. That aside, experts disagree on much of the ground at stake. It’s long been somewhat disreputable, in scientific circles, to think in terms of sudden, eye-blink events: it smacks of Biblical destruction. It was not until 1980, then, when the link was made between a strike by a six-mile-wide asteroid and the death of the dinosaurs that the notion gained respectability, and while the strike that Brannen describes is now largely accepted – an impact so massive (100 million megatons), and so instantaneous, that there are ‘probably little bits of dinosaur bone up on the moon’ – dissenting voices remain.
Some of these can be readily ignored (depressingly, he notes, the Creation Museum, with its ‘dioramas of tyrannosaurs boarding Noah’s Ark’, is flourishing); for a fascinating overview of the others, read his book.