Review of THE RISE AND REIGN OF THE MAMMALS
Steve Brusatte’s highly anticipated follow up book is here!
I remember reading Steve Brusatte’s excellent first book, The Rise and Fall of the Dinosaurs, back in 2018 and was obsessed with it. Truly one of the best science books I had read, and packed with fascinating insights. Soon after the success of his book, Brusatte announced that he would be writing a follow up book about mammal evolution. For years, I’ve been eagerly awaiting the book, and at the end of April, a beautiful advanced readers copy showed up in my mailbox.
The Rise and Reign of the Mammals: A New History From the Shadow of the Dinosaurs to Us was worth every minute of waiting. I blew through this 400-page book in 3 days and may or may not have put off other important things to do so because I couldn’t put it down. Brusatte is truly one of the greatest science writers I’ve had the privilege of reading. He masterfully presents highly detailed research in an organized and accessible way that makes for a highly enjoyable read.
I learned lots of new things about mammal evolution, but here are a few things stood out to me. First, that mammals have been evolving and thriving for a very long time – with mammalian traits evolving over hundreds of million years! The common narrative is that mammals were a trivial piece of the animal ecosystem during the reign of the dinosaurs, and it wasn’t until after they went extinct (with the exception of birds) that mammals finally had their time. In one sense that is true, but as with most things, it’s a bit more nuanced than that. Mammals simply occupied a different niche than dinosaurs. Mammals were abundant and diverse during the age of dinosaurs, but they were just very tiny. And what’s even more interesting, is that dinosaurs not only put pressure on mammals to stay small, but mammals also put pressure on dinosaurs to stay big!
Second, jaw and teeth evolution played a key role in mammals becoming who they are. Brusatte’s book focuses a lot on teeth and jaw evolution – and for good reason. Mammals evolved a new jaw joint that not only allowed us to innovate in the way we ate – allowing for chewing rather than swallowing food whole (imagine crocodiles eating) – but it also led to our keen hearing by freeing up some bones that were repurposed into the tiny three inner ear bones that define mammals.
Third, when the asteroid impact 65 million years ago killed off the dinosaurs, lots of mammals also went extinct – we too almost died out! North American fossils suggest that less than 10% of mammal species survived. And placental mammals, like us, took advantage. While placental mammals are most abundant today, in the Cretaceous period before the impact, marsupial mammals were on top. What helped mammals survive and thrive again post impact were the flexible, omnivorous diets – something dinosaurs lacked. And once the dinosaurs were gone, mammals began to grow rapidly and exploited new niches. As Brusatte says, “mammals had become the dinosaurs.”
But in terms of size, it’s unlikely mammals will get to titanic sizes that dinosaurs reached. Although the largest ever animal is a mammal – the blue whale – it lives in the ocean, not on land and doesn’t have to contend with gravity so much. The prize for largest land animals goes to the dinosaurs. Bigger animals have less surface area to expel heat (which is why elephants have big cooling ears!). But, crucially, the way in which mammalian lungs work differ from dinosaur lungs in such a way that they are less effective at cooling the body. Whereas mammals only get oxygen when breathing in, dinosaur and bird lungs get oxygen when breathing in and out. Dinosaurs also have air sacs throughout the body that essentially act as a massive air conditioning system throughout the body. It’s likely dinosaurs will retain the title for largest land animal – mammals will simply get too hot any bigger.
I could go on and on with interesting facts and new insights from The Rise and Reign of the Mammals, but I’ll let you read for yourself. It’s truly an astounding book, and I encourage everyone to pre-order your copy. I’m grateful for receiving an advanced copy and can’t wait to see the final version next week, when the book is released on June 7 in the US.
Published: June 2022
Format: Hardcover
If you think this sounds interesting, bookmark these other great reads:
Jungle: How Tropical Forests Shaped the World―and Us by Patrick Roberts (2021)
Spying on Whales: The Past, Present, and Future of Earth's Most Awesome Creatures by Nick Pyenson (2018)
Evolution's Bite: A Story of Teeth, Diet, and Human Origins by Peter Ungar (2017)
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