The Rise and Reign of the Mammals: A New History, from the Shadow of the Dinosaurs to Us

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This is a very beautiful story-driven, well-written book. This is like a fun novel you’re reading.” — Dax Shepherd, Armchair Expert The story of the Age of Mammals is often told as the flip side to the dinosaurs’ demise. But the fossil record reveals that mammals were hardly newcomers: They arose around the same time as the dinosaurs, over 200 million years ago. Even during the Age of Dinosaurs, “in the smaller and hidden niches, it was already the Age of Mammals,” Brusatte writes. “Mammals were better than the dinosaurs at being small.” Beginning with the earliest days of our lineage some 325 million years ago, Brusatte charts how mammals survived the asteroid that claimed the dinosaurs and made the world their own, becoming the astonishingly diverse range of animals that dominate today's Earth. Brusatte also brings alive the lost worlds mammals inhabited through time, from ice ages to volcanic catastrophes. Entwined in this story is the detective work he and other scientists have done to piece together our understanding using fossil clues and cutting-edge technology. Another great overview by Steve Brusatte (if you have not yet read The Rise and Fall of the Dinosaurs, I highly recommend that you do). In this book, Brusatte covers the evolution of mammals from Carboniferous period mammal ancestors up through present-day species. One of my favorite aspects of the book are the fictional vignettes Brusatte includes at the beginning of many of the chapters. These short stories (which are based on fossil evidence) really enrich the reading experience and illustrate what these animals would have been like while alive. I also enjoyed the passages where he talked about his own experiences as a paleontologist. Like The Rise and Fall of the Dinosaurs, which I sped through in a few days, this book is highly readable. As a science consultant for the forthcoming film Jurassic World Dominion, Brusatte has nothing against dinosaurs, and the shelves of his office are teeming with sketches, plastic models and even origami creations of the beasts.

Mammals shared our planet with the dinosaurs throughout their long reign, from the initial split of our amniote common ancestor into synapsids (us) and diapsids (them), to their extinction at the end of the Cretaceous. Over the course of some 100 million years, a parade of lineages evolved—archaic mammals all—piecemeal developing the traits we recognize as mammalian today: pelycosaurs, therapsids, cynodonts, mammaliaformes, docodonts and gliding haramiyidans, multituberculates, and therians who gave rise to today's placentals, marsupials, and monotremes. However, the above must not be mistaken for a linear march of progress. "[M]ammals were a still unrealized concept, which evolution had yet to assemble" (p. 20). Simultaneously, it does not behove us to call these now-extinct groups evolutionary dead ends. "In their time and place, these mammals were anything but obsolete" (p. 88). I am not a paleontologist nor any other kind of scientist, but recently I have become obsessed with books that explain how the world became what it is today. That obsession led me to listen to this book.The manner in which he tells the story, our story, is nothing short of prosaic prose transformed into poetry. ... Brusatte presents a myriad of facts about todays’ mammalian cohabitors of our planet that will whet your appetite and fire up your imagination.” — Times of Israel I've previously read Brusatte's book The Rise and Fall of the Dinosaurs: A New History of a Lost World. As he tells in the beginning of this volume, he was lured into paleontology by dinosaurs, those fearsome extinct creatures that have enraptured generations of children. I was one of those kids, so his dinosaur book was retreading well known territory for me. It was written in an accessible style and I was delighted when I realized that he had penned a similar book about early mammals. Over these immense stretches of geological time, mammals developed their trademark features: hair, keen senses of smell and hearing, big brains and sharp intelligence, fast growth and warm-blooded metabolism, a distinctive line-up of teeth (canines, incisors, premolars, molars), mammary glands that mothers use to nourish their babies with milk, qualities that have underlain their success story. The number of mammal species continued to expand and diversify through the Paleogene era. South America, Australia, and Madagascar experienced some unique species because of their isolation. About three million years ago the drifting continent of South America made connection with North America which resulted in the extinction of many of the South American mammals because of new predators moving in from the northern continent. I can remember learning in grade school science that dinosaurs ruled the earth for a while until they disappeared; then the mammals took over. Years later that perception was reinforced while visiting the Smithsonian Museum of Natural History where I noticed a small model of a fur ball on the floor next to a display of a gigantic dinosaur skeleton. As I recall there was a label next to the fur ball indicating that it represented the typical mammal during the time of the dinosaurs.

Watching these pieces of the past come together was deeply gratifying, if not a little dizzying. The present is so familiar that it feels inevitable. But it was striking to see modern civilization, even modern humans, in context, to recognize how all that we are now actually hinges on countless moments of invention, improvement and experimentation in the deep past. Upper-side 3D rendering of content inside a burrow: Thrinaxodon and Broomistega. Photograph: Creative Commons Attribution LicenseTodd Marshall But Brusatte is not only enthusiastic about showcasing bizarre mammals of the past. He wants greater appreciation of what is here now. To illustrate his point, he notes that besides birds and pterodactyls, only one creature has evolved the ability to fly by flapping its wings: bats. Some of the moments of evolutionary invention that led to what we now think of as a mammal are remarkably subtle. There’s the hard roof of the mouth that created a dedicated airway to the lungs, allowing mammal ancestors to eat and breathe at the same time. There’s the change from a spine that bends from left to right (which produces the classically reptilian side-to-side gait) to one that enables bending up and down, which ultimately allowed mammals to take in more oxygen as they moved, helping them run faster. And there’s the variety of tooth shapes — incisors, canines, premolars and molars — that made it possible for mammals to eat many kinds of food. A reptile, by contrast, tends to have just one tooth type.On the whole I am less familiar with prehistoric mammals than I am with dinosaurs. Although the book includes plenty of photos of skeletal remains, I kept breaking off to look on the web for artistic reconstructions of what the animals might have looked like. Of course once we get to the Ice Age the animals tend to be more familiar. I probably enjoyed that chapter the best, along with the author’s explanations as to why these huge climatic shifts happened. Humans, too, offer much to marvel at: as Brusatte points out, we are sentient apes that have changed the world. But we are only a chapter in a far bigger story.