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

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

2022 has been a banner year for me in terms of non-fiction reading, and that trend continues with The Rise and Reign of the Mammals: A New History, from the Shadow of the Dinosaurs to Us, by Steve Brusatte, an epic and vividly told survey of how evolution bit by bit equipped our ancestors with the tools necessary to at first survive and then thrive. As with Brusatte’s earlier work, the excellent The Rise and Fall of the Dinosaurs, this is popular science as it should be done: clear and compelling.

Brusatte begins before the mammal line as we think of it comes into existence, setting the context for what drove the evolution and doing so broadly, discussing not just specific creatures but eco-systems (i.e. including plants), climate, and the impact of extinction events. He also does a nice job of dealing with a common issue in popular science, which is not just informing readers but also sometimes having to “un-inform” them, by which I mean having to disabuse them of prior notions which are now in error (these may be the reader’s misconceptions/misunderstanding but just as often are formerly consensus scientific views that have been superseded by improved knowledge). For instance, early on he updates readers on the former phrase “mammal-like reptile” (which I’m old enough to recall in my popular science reading), which has been replaced by “stem mammal” for the pretty logical reason that any such creature, such as the well-known Dimetrodon, was “not a reptile nor did it evolve from reptiles.” Similarly, the idea that mammals only got their chance thanks to the dinosaurs going extinct is also debunked, with Brusatte making clear that the mammal antecedent were around well before then, mammals coexisted with dinosaurs, and also makes the nuanced point that while dinosaurs may have prevented mammals from growing large, mammals (thanks to filling their own ecological niche) conversely kept dinosaurs from radiating into small sizes. In that same “knowledge marches on” vein, he clearly explains how early relationship trees based on anatomical similarities have been refined (and often completely changed) thanks to DNA studies, which have shown that much of what was once thought to show ancestry/relationship was actually simply a matter of convergent evolution.

Steve Brusatte

From these early stem mammals, Brusatte takes us on a lively tour (mostly chronological though that changes somewhat when he gets to evolution of specific animal lines such as whales and horses) of transformations that get us to, well, us. These include evolutionary changes in teeth, ankles, spine, placentas, diet, metabolism, and more. While I personally found it all fascinating, I can’t say that some people might not want less detail on, say, teeth. But that’s the reality of paleontology — if you’re going to distinguish creatures, you’re going to have to discuss, a lot, the nature of teeth. Not only because they are such a distinguishing characteristic but because of how, thanks to their makeup, they tend to survive a lot more frequently (and in quantity) than other body parts. Often, for long periods of time, teeth are the only body part we have for a particular creature.

While the entire work is excellent throughout, the book really soars (literally when it comes to the section on bats) when Brusatte narrows the scope a bit to focus on particular lines, including, bats, whales, and elephants. These chapters create that sense of awestruck wonder good nature writing can do, where one cannot help but marvel at the variety, fecundity, and audacity of nature, as mammals take to the sky and to the water to spread across the globe. None of it, btw, out of any sense of design or purpose, as Brusatte is careful to remind us of many times, as when he tells us “natural selection doesn’t plan for the future.” It’s also always nice when a scientist lets us see how they too share our sense of wonder, as when Brusatte waxes rapturously on how “the biggest animal that has ever lived is alive right now. Of all the billions of species that have lived during the billions of years of Earth history, we are among the privileged few who can say such a thing. How glorious is it that we breathe the same air as a blue whale, swim in the same waters, and gaze at the same stars?”

While the title includes an “Us” in there, and humans do make an appearance, it is only at the very end, as Brusatte is much more interested in our primate cousins. When humans do show up, we get a nicely concise overview of our evolutionary “bush” with a few dips into some star examples, such as Lucy, but really this is not the book to turn to if you’re interested in human evolution. In fact, Brusatte spends just as much time on our devastating impact on other creatures as our own development (though he does end on an optimistic, or at least, hopeful, note). On the other hand, individual humans come across much better than our species as a whole, as Brusatte takes the time to paint several engaging portraits of scientists — past and present — who have contributed to our knowledge.

The prose is clear, lively, engaging, and personable throughout. And some scenes are wonderfully vivid, particularly a narrative section depicting the volcanic devastation that killed a huge number of creatures in Ashfall, Nebraska, preserving them in ash (I’ve been to Ashfall several times and the bodies are as amazing as Brusatte makes them out to be). The prose is also nicely bolstered by a large number of illustrations that are particularly helpful when it comes to showing the evolutionary changes. Meanwhile, the bibliography is absolutely fantastic, not just for the breadth but because of how it takes a much more narrative, conversational form than most, with Brusatte detailing how or why he used some sources, or why he didn’t have time/space to use others and characterizing many of the sources as “exciting” or “masterful” or “required reading.” I always consider it the mark of an excellent non-fiction work when I find myself highlighting (a lot) the bibliography/chapter notes.

Finally, a year ago Elsa Panciroli came out with Beasts Before Us: The Untold Story of Mammal Origins and Evolution, and while the title obviously points to there being a lot of overlap between the two, if you haven’t read Panciroli’s excellent work I highly recommend reading both one after the other as the two strongly complement one another, are different enough in detail and style to keep both interesting and engaging, and the dual reading will cement things in your head.

I’ve been in love with dinosaurs since I was a child, and my office has several biologically accurate models of them in clear sight. I’m thinking now I’m going to have to add some early mammals to my menagerie as well.