Given that we are nothing but mammals, it is perhaps understandable that humans are rather mammal-centric, something that conservation organisations capitalise on. But where palaeontology is concerned, dinosaurs get all the love. And that does early mammals little justice says Scottish palaeontologist and Palaeocast co-host Elsa Panciroli. Far from mere bit players cowering in the shadows of these “terrible lizards”, mammals have a long and rich evolutionary history that predates the dinosaurs but is poorly known outside of specialist circles. Panciroli’s debut changes all that and does so in a most readable and immersive fashion.

Beasts Before Us: The Untold Story of Mammal Origins and Evolution, written by Elsa Panciroli, published in Europe by Bloomsbury Publishing in June 2021 (hardback, 320 pages)

To pick up the tale of mammal evolution, Panciroli takes you all the way back to the Carboniferous (roughly 360–300 million years ago) when higher oxygen levels supported a land of giants. It was here that the first fish made landfall and tetrapods evolved. To get from this distant ancestor to modern mammals, you have to follow the story through groups whose names are likely unfamiliar. To help you visualise these, stylish illustrations from April Neander open each chapter, while the endpapers* provide a helpful family tree drawn by Marc Dando. These do not list all mentioned groups but do present the big picture and I found myself referring to them frequently.

Thus we get to meet the synapsids, one of which you will know: the sail-backed, no-it-is-not-a-dinosaur Dimetrodon. Synapsids included the pelycosaurs (also not dinosaurs), which gave rise to the therapsids: carnivores with more powerful jaws and a stronger bite. Some of these, including the gorgonopsians, pioneered sabre-teeth, proving later groups to be mere copy-cats. Convergent evolution is, quite literally, a recurrent theme that Panciroli mentions whenever she can get away with it. Various therapsids were also the first groups to evolve endothermy or warm-bloodedness, though “like so many of the features associated with mammals [it] emerged scattershot. It wasn’t switched on like a lightbulb, lighting up all therapsids at once” (p. 120).

As the end-Permian mass extinction wiped the slate clean, the age of reptiles had begun. But some of our mammal ancestors survived. Rising like a phoenix from the ashes were, amongst others, the dicynodonts, who would have looked you in the eye from behind tusks and a turtle-like beak. One particularly successful group, possibly because it dug burrows, was Lystrosaurus, a genus that in the early Triassic made up 90% of all vertebrates. A related group, the cynodonts, is largely responsible for the misconception that our ancestors were insignificant during the reign of the dinosaurs, as they evolved to be smaller. But this was a feature, not a bug: “With no space among the giants, they took a different route: they perfected being tiny” (p. 163). They exploited the safety of the night, became nocturnal, and developed sensitive eyes. They also lost some ribs and developed a waist, allowing for more flexibility in their locomotion—early synapsids had ribs all the way down.

“[One] group, the cynodonts, is largely responsible for the misconception that our ancestors were insignificant during the reign of the dinosaurs, as they evolved to be smaller. But this was a feature, not a bug”

The Jurassic saw groups such as tritylodontids, docodontans, and multituberculates flourish. As their names imply, these groups experimented with tooth morphology, which later became important diagnostic fossil characters. None of them left living descendants. Instead, it was the therians who were our direct ancestors, but they did not diversify until after the K–Pg boundary. Interestingly, Panciroli suggests** that it was not the dinosaurs that kept the therians in check, but competition from all the other Jurassic mammal groups. This more recent history of the adaptive radiation into modern marsupials and placental mammals is well known, so she purposefully ends the book where most others start the story of mammal evolution .

This brief exercise in name-dropping provides only a snapshot of what Panciroli discusses, and she does a far better job of it. She weaves in the history of fossil discovery and her own work at dig sites in South Africa and Scotland, or labwork at the European Synchrotron Radiation Facility in France. Next to telling the story of mammal evolution, Panciroli also takes on the task of disarming and deconstructing a large amount of cultural and linguistic baggage, with two issues standing out.

First, as part of a younger generation of scientists, Panciroli is keen to decolonise her discipline. This means acknowledging that the scientific collections on which she herself works are the spoils of empire. Our museums are filled with colonialist plunder. Especially in the first chapter, where she gives a potted history of geology and biology, she repeatedly points to the imperialist framework in which these disciplines were born and how that has shaped conventions and biases to this day. Celebrated figureheads such as Buckland, Darwin, Lyell, Cuvier, Hutton, Lamarck, Owen etc. simultaneously held ideas now considered unsavoury, and they rarely credited Indigenous knowledge or help in the acquisition of fossils. Furthermore, as a woman, she has a few things to say about diversity. Like many academic disciplines, palaeontology remains largely populated by white, Western men, and it has been hard to shake off the image of the “stereotypical male adventurer” and his “macho plundering of the past” (p. 249). Fortunately, the contributions of women are increasingly being acknowledged, and Panciroli here celebrates Polish Mesozoic mammal researcher Zofia Kielan-Jaworowska who was the first woman to lead fossil collection expeditions in Mongolia.

“[…] the long history of evolutionary theory means that outdated modes of thinking continue to permeate our language. […] Panciroli similarly uses every opportunity to remind you that evolution is not goal-directed”

Second, the long history of evolutionary theory means that outdated modes of thinking continue to permeate our language. She shudders at the term “mammal-like reptiles” still used to describe the synapsids: “This first amniote tetrapod was neither mammal nor reptile—neither of those groups had evolved yet” (p. 61). We did not evolve from reptiles, nor are they more primitive compared to us. Panciroli similarly uses every opportunity to remind you that evolution is not goal-directed: “It is random, the route forged by happenstance” (p. 57). It has proven hard to let go of the Scala Naturae, the idea of a linear series of improvements, “like an assembly-line through time” (p. 120) leading ultimately to the perfect organism: us.

This neatly leads to my last observation: Panciroli’s writing is sublime. Her prose is concise without being stunted, her visual metaphors rich without being flowery. Of the late Triassic mammals she writes: “These tiny ancestors were living microchips. They were night-vision goggles. They were fuzzy little ninjas, wielding shuriken teeth to reap their insect prey in silence and stealth” (p. 171). On the break-up of Pangaea: “After their epic 250 million-year snuggle, the continents of Earth were parting ways […] By the end of the Jurassic, the whole world was unzipping itself, with new seas and oceans splashing into the gaps” (p. 203). On the K–Pg event: “The universe drew an iridium line under things. From here on, life would be different” (p. 274). And her description of the tritylodontid herbivore niche is just beautiful: “All of the non-mammalian cynodonts had turned to dust, except for the tritylodontids […]. Natural selection had moulded them into premier leaf-grinding machines. Of course there had been synapsid herbivores before […] but those bulky predecessors were gone. In the world of crocs and dinosaurs, mammals had microscoped themselves into the understorey, and the tritylodontids were left to eat the scenery” (p. 237).

Beyond a few academic textbooks and technical monographs, the deep evolutionary history of mammals has remained largely hidden in the academic literature. Beasts Before Us unleashes their story most spectacularly and engagingly. This beautifully written debut marks Panciroli as a noteworthy new popular science author. May this be the first of many books! You might also want to check out my Q&A with Panciroli published over at the NHBS Conservation Hub.

* Illustrated endpapers are one of my favourite features in a book, and one that, I think, too few publishers and authors use.

** The paper arguing this, still in press when she wrote this book, has just been published in Current Biology.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Beasts Before Us

Other recommended books mentioned in this review:

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“The Story of the Earth in 25 Rocks: Tales of Important Geological Puzzles and the People Who Solved Them“, written by Donald R. Prothero, published by Columbia University Press in January 2018 (hardback, 354 pages)

The range of topics covered by Prothero is diverse, and seemingly not organised in any fashion. But start reading through the book, and connections are made across chapters. Some of his chapters tie in with Dartnell’s book Origins: How The Earth Made Us that I just reviewed, chronicling the discovery of economically important deposits of coal, tin or iron and how these were formed. Others will take the readers off the planet as he tackles meteorites and moon rocks. Interestingly, Prothero thinks Earth’s water has been present since the beginning, discounting the mechanism of delivery-by-comet, something which Starkey deemed a much more likely possibility (see my review of Catching Stardust: Comets, Asteroids and the Birth of the Solar System).

Throughout, Prothero highlights the role of chance discoveries, such as the finding of cyanobacterial colonies in Australia that leave behind domed rocky structures called stromatolites, some of the oldest trace fossils in the fossil record, or the famed iridium layer that birthed the idea of a cosmic impact ending the reign of the dinosaurs (see T. rex and the Crater of Doom – Prothero gives a very informative overview of how the tide of opinion and evidence on how impactful that impact was sways back and forth to this day). Another famous story is how Clair Patterson’s research on dating of meteorites produced exquisitely sensitive methods to measure lead levels, resulting in the discovery of widespread lead pollution, a discovery for which he was attacked by powerful industry lobbies throughout his lifetime.

“Prothero highlights the role of chance discoveries [such as] Clair Patterson’s research on dating of meteorites [that] produced exquisitely sensitive methods to measure lead levels, resulting in the discovery of widespread lead pollution […]”

Another theme that returns time and again is how external forces and priorities provided funding and resources for important discoveries. It was the search for coal in Victorian Britain that led William Smith to produce the first map of geological strata in England in 1815, which pretty much launched the discipline of stratigraphy (see The Map That Changed the World: A Tale of Rocks, Ruin and Redemption for more). Other authors have already highlighted how the military has been instrumental in the developing discipline of oceanography, providing the material and thirst for knowledge to map the globe’s deep sea.

Prothero rightfully lavishes most attention on the cornerstones of geology; concepts such as deep time (see e.g. Earth’s Deep History: How It Was Discovered and Why It Matters or Nature’s Clocks: How Scientists Measure the Age of Almost Everything) and plate tectonics. Other than the now-famous insights of Alfred Wegener (much ridiculed during his lifetime and afterwards, see my review of Four Revolutions in the Earth Sciences: From Heresy to Truth), he discusses all the evidence in favour, and the vindication that came with findings from amongst other palaeomagnetism (see my review of The Tectonic Plates are Moving! and The Spinning Magnet: The Force That Created the Modern World – and Could Destroy It). But he also highlights subsequent insights, such as subduction zones and transform faults (e.g. the infamous San Andreas Fault).

The Story of Earth in 25 Rocks celebrates the many scientists whose names and contributions have been downplayed, such as Marie Tharp’s contribution to creating a map of the entire ocean floor (see Soundings: The Story of the Remarkable Woman Who Mapped the Ocean Floor). Or the people who are rarely mentioned, such as Scotsman James Croll’s work on variation in Earth’s orbital motion patterns well before Milutin Milankovitch. Prothero rightfully speaks of the Croll-Milankovitch cycles. Similarly, his chapter on turbidites (the product of large underwater landslides) highlighted fascinating research and characters that were all new to me.

“The Story of Earth in 25 Rocks celebrates the many scientists […] who are rarely mentioned, such as Scotsman James Croll’s work on variation in Earth’s orbital motion patterns well before Milutin Milankovitch.”

Each chapter comes with a short recommended reading list, highlighting a selection of excellent popular science books and more academic works. A great selection of period photographs is included and many diagrams and graphs have been redrawn or slightly modified to ensure their legibility and usefulness – some photos of rock formations, on the other hand, would have been better off being reproduced in colour. There are some minor mistakes, such as submarine Alvin supposedly diving almost 4,800 kilometres beneath the waves (p. 19), which made me question the statement on page 146 that the Hull-Rust-Mahoning iron mine has produced over 650 million metric tonnes of ore, and more than 450 metric tonnes of waste (should that latter also be million metric tonnes, or is this mine particularly rich in iron ore?) Prothero furthermore reports dimensions and masses in both metric and imperial units in some chapters, but is not consistent in doing so throughout the book.

The above are but minor quibbles that take nothing away from the sheer joy and enthusiasm with which Prothero serves up these 25 chapters. Incredibly well written and insightful, there is something here for everyone with an interest in geology. Prothero distinguishes himself as an excellent science communicator and I cannot wait to get my hands on his other two books, The Story of Life in 25 Fossils: Tales of Intrepid Fossil Hunters and the Wonders of Evolution, which preceded this book, and The Story of the Dinosaurs in 25 Discoveries: Amazing Fossils and the People Who Found Them.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

The Story of the Earth in 25 Rocks paperback, hardback or ebook

Other recommended books mentioned in this review:

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“Earth History and Palaeogeography“, written by Trond H. Torsvik and L. Robin M. Cocks published by Cambridge University Press in December 2016 (hardback, 317 pages)

Trond H. Torsvik and L. Robin M. Cocks, both established geologists, draw on a huge body of interdisciplinary knowledge for this book. This includes, amongst others, palaeomagnetism and polar reversals (see my recent review of The Spinning Magnet: The Force That Created the Modern World – and Could Destroy It for an introduction), past volcanic eruptions, geophysics and tomography (a technique to visualise the inside of the planet), the rock record, and fossil distribution. Putting this all together allows them to reconstruct the face of the Earth over the last 540 million years. We know that plate tectonics was happening earlier in time as well, the geological story at the heart of the lyrical A Wilder Time: Notes from a Geologist at the Edge of the Greenland Ice was that we have evidence for plate tectonics as far back as approximately 2 billion years, and this book even mentions 3 billion years. But details just become too sketchy to make reliable planetary-scale reconstructions. So, as the authors make clear, this is by no means the definitive story but a work in progress. This book shows the current state of our knowledge, which will no doubt be further refined in the future.

After outlining their methodology and introducing, with maps, all 268 tectonic units that they have recognised as currently making up the surface of our planet (that’s a lot more you typically see on schematic maps) we get to the bulk of the book. This consists of eleven chapters that cover each geological period from the Cambrian (541-487 million years ago) to the Neogene and Quaternary (23 million years ago to today). Each chapter starts with several overview maps of the whole planet at various stages of each geological period which are already worth their weight in gold if this floats your boat. But that’s just the beginning.

“[these] overview maps […] are already worth their weight in gold if this floats your boat.”

A large number of maps and diagrams show different projections and perspectives, systematically going through each of the major continents as they existed back then. These maps show current continent outlines and estimated coastlines and deep and shallow seas back then, but also divisions between plates where the seabed was spreading apart or where plates were being subducted or colliding to form mountains chains. Symbols indicate approximate locations of major reefs, ice caps, lakes, areas of volcanic activity including large igneous provinces (the massive volcanic eruptions implicated in mass extinctions that we met in The Ends of the World: Volcanic Apocalypses, Lethal Oceans and Our Quest to Understand Earth’s Past Mass Extinctions), areas where coal was deposited, areas that dried up and left evaporites, faunal provinces that show the distribution of important fossil groups, as well as side-bars with approximate sea-level and climate conditions compared to today, and many other details. In the later chapters on geologically younger periods, when more details can be reliably reconstructed, many other diagrams and maps are shown, detailing the formation of mountain ranges such as the Himalayas, the appearance and disappearance of oceans, movements of the oceanic plates, etc. etc. The amount of information that is packed into these figures is breathtaking.

The text, meanwhile, links together the different events depicted and provides further context and details. Some things cannot be shown on the maps, such as the location of certain minor plates. We know they were somewhere, but we often lack enough information to place them on a map in any meaningful way. The text not only covers the geological details but also contains a section describing the dominant flora and fauna and important developments in the evolution of life during the period in question.

The book is not what you would call bedtime reading (though that did not stop me from doing so anyway) and is suffused with jargon. This comes from three sources. All geological periods are divided into shorter stages that have their own names, as shown on the official International Chronostratigraphic Chart that is printed on both endpapers. All 268 tectonic units have their own names that are introduced in detail in chapter 3. But on top of that is the terminology for geological processes and rock types. This is where my decision to study biology rather than geology comes back to bite me (I am looking at investing in some undergraduate geology textbooks because the subject continues to interest me). So if, like me, you can’t tell your ignimbrite from your gneiss, or don’t know the difference between volcanoclastic intercalations and diachronous migration, you might struggle with the text. Now, to fault the book for this would be completely missing the point. This is an advanced-level reference work, squarely aimed at an audience of geologists and palaeontologists with the relevant background knowledge – but it is good to know going in. Even so, with my limited knowledge of geological processes mostly gleaned from popular academic books, I was able to follow the grand narrative just fine. And what a fantastic story it tells!

“This […] advanced-level reference work [is] squarely aimed at an audience of geologists and palaeontologists with the relevant background knowledge”

I cannot think of another book that takes such a clear, graphic approach as Earth History and Palaeogeography does. Not being familiar with the field, I am hesitant to claim this is a first, but it is obviously a very valuable compilation of the current state of our knowledge. For geologists and palaeontologists this is a mandatory reference work, but academically-minded book readers might also find this very interesting. I expect I will regularly be pulling it off the shelf to consult it while reading other books on palaeontology or geology.

For those interested, there are supplementary online resources, including several programmes that allow you to make your own reconstructions, including graphics and maps like the ones shown in the book. I have not played around with this, but it is fantastic to see the authors willing to keep this project alive post-publication.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Earth History and Palaeogeography hardback or ebook

Other recommended books mentioned in this review:

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