The Rise And Reign Of The Mammals: A New History: From The Shadow Of The Dinosaurs To Us, by Steve Brusatte

Having read about the Cenozoic Period before–that is, the period between the cataclysmic end of the time of the Dinosaurs to today–I can appreciate what this book has to offer in terms of providing a narrative. As it happens, the author himself was educated and first spent a great deal of time as an expert in dinosaurs and has recently found himself more interested in exploring mammals, with implications to the present-day. The author is free in acknowledging his fictionalizing of tales that are based on the evidence of bones, and it is similarly clear that paleoarchaeology rests on some very slender supports as a field. There are at least a few cases where the absence of evidence is frequently taken as the evidence of absence, and where areas that were thought to be “picked over” for bones have continued to provide surprises such that even a first-year student in the field as an undergraduate can find new species. There are also serious questions how, in a world where convergent evolution is considered to be so rampant, and where the mammals themselves have frequent trouble in distinguishing between similar looking beings that serve the same functions but may not necessarily be closely related simply because they look similar or have similar roles. The author makes a great deal out of a pattern that diversification within mammals comes frequently from insectivores, for what it’s worth.

This book is a bit more than 400 pages of material that is organized generally but not entirely chronologically and also a bit thematically. The book begins with a timeline of mammals, a mammal family tree, maps of the earth over time and an introduction about the family of mammals as a whole. After this we have a look at mammal ancestors going back, in the author’s estimation, more than 200 million years ago (1). This is followed by a discussion of early mammals and what makes a mammal (2) as opposed to a mammal-like reptile. An entire chapter is devoted to the relationship between mammals and dinosaurs (3), which focuses on the fact that mammals monopolized the smaller land-animal niche just as dinosaurs were, well, larger. This is followed by a discussion of the mammalian revolution and, crucially, its happening while dinosaurs were still around (4), and another chapter on the familiar and often-told tale of the impact that killed all the dinosaurs (except for avian ones) but allowed some mammals to survive (5). A chapter then follows on the modernizing and development of mammal branches on already separated continents (6). This is followed by a discussion of extreme mammals like the whale, rhino, and elephants, among others (7). After this comes a look at how mammals dealt with changing climates in the period after the Eocene (8), as well as how they dealt with the ice ages (9) that include our own current interglacial period. This is followed by a chapter on human involvement with the world and the development of our own sort of being (10). An epilogue on the future follows before th book ends with notes on sources, acknowledgements, and an index.

There are a lot of takeaways that one can get from this book. One of them is that mammals themselves are a pretty opportunistic group of animals, and that contrary to what we may expect, there are wide differences in the mammal lineage that go back a long, long way. In addition, there appear to have been multiple cases where mammals arrived via the water from Africa to South America, which is worthy of further investigation than has been done previously, or at least communicated to other people widely. The author talks about climate change, although he is optimistic that human beings and other mammals will survive, despite the pretty grim look at extinction in the present day that others have noticed thanks to predictable discussions of global warming. The author also comments, almost apologetically, on the struggle that climate modelers have in properly understanding the origins of climate or what factors cause the climate changes that are seen in the record of the earth in tree cores and the like. There is a lot going on, and the author’s narrative threads a delicate needle between dealing with definitions, seeking to provide a readable narrative of ancient and often extinct life, and also sticking to the science, and there are about 70 pages or so of worthwhile discussion of the many sources that the author consulted in writing this book, which, if not perfect, is certainly a worthwhile achievement nonetheless.