I'm going to open with, this book is flat out amazing. In school, or even through popular science journalism, we learn a bit about some key points of geologic time. But these are snap shots, Dinosaurs, Ice Ages, even Snow Ball Earth. Really interesting things on their own, but they all seem a little disjoint.
This book brings an incredible visual narrative through life on Earth, by looking at the 5 mass extinction events the planet has experienced. An extinction is only emotionally meaningful if you understand what is lost, so the author paints an incredible picture of the aliens worlds that were Earth in these previous eras. Worlds without life on land, worlds of giant insects, worlds of bus size armored carnivorous fish as apex predators. He does this by road tripping to the scientists and fossil sites where this story is being assembled, talking with experts along the way. A story as old and hidden in the fossil record needs lots of lines of evidence to point to answers, and the author does a great job of doing that, and pointing out what we seem to know, and what we've only got guesses on.
The story of life on earth is the story of carbon and climate. As volcanoes stirred up carbon from the deep, and life reclaimed it, died, and sunk it back into the Earth. When this cycle gets really out of whack, the climate goes nuts, and life is paused on planet Earth, and taken tens of thousands of years to get back on track. There are many points of reflection about how our current mining and burning of ancient sequestered carbon is impacting our world today.
There are also just incredible moments that make you sit and think. The death of the land based mega fauna, 12,000 years ago, in North America, that still leaves ecological holes.
But the menagerie lives on in evolutionary ghosts. In North America, the fleet-footed pronghorns of the American West run laughably faster than any of their existing predators. But then, their speed isn’t meant for existing predators. It might be a vestige of their need to escape constant, harrowing pursuits by American cheetahs—until a geological moment ago. The absence was palpable to me as I rode a train past New Mexico’s Kiowa National Grassland, an American Serengeti, windswept and empty except for a lone wandering pronghorn still running from ghosts.
Other evolutionary shadows of the Pleistocene live on in the produce aisle. Seeds in fruit are designed to be eaten and dispersed by animals, but for the avocado this makes little sense. Their billiard ball–sized cores, if swallowed whole, would at the very least make for an agonizing few days of digestive transit. But the fruit makes a little more sense in a land populated by tree-foraging giants, like the sometimes dinosaur-proportioned ground sloths, who swallowed the seeds and hardly noticed them. The ground sloths disappeared a geological moment ago, but their curious fruit, the avocado, remains.
It will make me never quite look at an avocado the same way again.
There are so many things I learned which made me reconsider my whole view of dinosaurs. Like Dimetrodon, the creature with a large sale on it's back for temperature regulation, is more closely related to mammals than dinosaurs. And without the 3rd mass extinction, we'd never have seen Dinosaurs, and mammals might have ruled the Earth much earlier. And that T-rex showed up really late on the scene, filling the niche that that much more successful Allosaurs held as apex predators for most of the Jurasic era (the Allosaurs all disappeare in a more minor great extinction).
It's not often that you find a non fiction book that both reads fast, and dumps such an incredible amount of information on you. The jumping back and forth from road trip, chatting with scientists, facts, and painting pictures of the world that was, works really well. There is never a dull moment in it, and you come out the far end for a much greater appreciation for life on Earth in all its forms.