Category: Book Review

*****A unique on the story of dinosaur extinction and its aftermath

The day an asteroid slammed into the Yucatán Peninsula some 66 million years ago is a strong contender for “the worst day in history”. The K–Pg extinction ended the long evolutionary success story of the dinosaurs and a host of other creatures, and has lodged itself firmly in our collective imagination. But what happened next? The fact that a primate is tapping away at a keyboard writing this review gives you part of the answer. The rise of mammals was not a given, though, and the details have been hard to get by. Here, science writer Riley Black examines and imagines the aftermath of the extinction at various times post-impact. The Last Days of the Dinosaurs ends up being a fine piece of narrative non-fiction with thoughtful observations on the role of evolution in ecosystem recovery.

Before delving in, a brief word on what is not in the book. Black does not discuss the history of the research that discovered evidence of an asteroid impact, such as the iridium spike and the crater. Nor does she go into the ongoing debate on the relative contributions of the asteroid and Deccan Trap volcanism. Instead, Black’s approach is to imagine a day in the life of the survivors at various time points post-impact: after an hour, a day, a month, a year, a century, all the way up to one million years. She focuses on the Hell Creek formation in western North America as it offers one of the clearest windows into the mass extinction and its aftermath. Most chapters have a short coda that looks at how life was faring elsewhere on the planet. Black’s style of choice is narrative non-fiction: she is resurrecting individual animals and imagining their lives. As she explains in her preface, to allow full immersion, she is not interrupting the flow of her story with notes and references, which are found at the back of the book. An extensive, 58-page(!) chapter-by-chapter appendix reveals her process and discusses what we know, what is hypothetical, and where she has speculated to smooth over the gaps in our knowledge.

Now, when this book was announced, just the prospect of dipping into the story of the disaster and the ensuing recovery already had me excited. However, The Last Days of the Dinosaurs surpassed even these expectations for two main reasons.

First, there are plenty of exciting new ideas and scientific findings here. Black’s interpretation of the impact will no doubt ruffle some feathers as it is particularly catastrophic. Forget the often-depicted idea of an asteroid seen streaking across the sky, Black writes, this thing came in fast at some 45,000 miles per hour (~20 km/s). Forget, too, the often-depicted drawn-out hunger winter for the surviving dinosaurs. I had not come across this idea before, but Black writes how a global heat pulse that lasted several hours fried anyone that could not crawl underground or stay submerged underwater. This is based on estimates of the amount of material ejected by the impact that, upon re-entry, heated the atmosphere to several hundreds of degrees centigrade. It would have ignited global wildfires. Finally, the impact injected vast amounts of sulfate aerosols into the atmosphere as the impact site was rich in calcium sulfate. The ensuing acid rain “might have effectively erased some of the slowly forming fossil record” (p. 256), explaining why fossils are hard to find in the layers around the K–Pg boundary.

Regarding the survivors, Black has plenty of interesting ideas too. As seen at other times and other places, there was a fern spike. A rapid initial proliferation of ferns is frequently seen in devastated ecosystems where plants have died. And why did birds survive? One novel idea is that the survival of beaked, but not toothed birds is part of the answer. “Maintaining a mouth of sharp teeth comes with a reliance on animal food. […] A consumer that feeds on other consumers has very little to survive on now. But beaked birds do not face the same constraints” (p. 117). With the extinction of toothed birds and pterosaurs, the beaked birds were poised for an evolutionary radiation. Something similar happened with the mammals. Black prominently mentions the idea that Elsa Panciroli promoted in Beasts Before Us, that “it was competition between mammals that limited the number of different forms and niches Mesozoic mammals evolved into” (p. 158). With the extinction of more archaic mammaliaformes, the placental and marsupial mammals would flourish.

The second reason the book surpassed my expectations is Black’s reflections on the process of evolution and its role in ecological recovery. This is where her prose sings in places. One thousand years post-impact “[…] there is no script for what’s about to unfold, no cast of characters that inevitably must be filled” (p. 142). One million years post-impact a reptilian resurgence seems unlikely, but “the rise of the mammals is anything but assured […] When a global disaster ends one evolutionary dance, shifting the tempo, another begins, with no certainty as to who will lead” (p. 182). She poignantly notes how the fossil record “is not in any way a complete record of life on Earth. It is a record of fortuitous burials” (p. 254). And on the process of evolution, she writes how variation and happenstance provide “the raw material for natural selection and other evolutionary forces to shunt down different pathways. Not that there is any intent to this. It’s a passive state, a constantly running routine that is merely part of existence itself” (p. 196). This is music to my ears and Black’s writing is one of the highlights of this book.

Writing about such an iconic event carries the risk of intense scrutiny. No doubt, some experts and other palaeo-nerds will disagree with some of the details presented here. I think her appendix is sufficiently explicit about where she speculates and where she has chosen not to hedge her bets on different explanations. I was willing to read the book in this spirit, as one possible interpretation of how things might have unfolded, though one that Black carefully backs up with scientific evidence. My quibbles are rather minor instead. One is that the book has no index, the other is that there are no notes to the appendix. Relegating the discussion of the underlying science to the appendix is a defensible choice. But not properly referencing the studies mentioned here is, to me, a minor blemish on an otherwise excellent book.

If you have any interest whatsoever in dinosaurs and their extinction, this book comes highly recommended. Her take on the topic, dipping into the extinction and recovery at various moments post-impact, is novel. I am not familiar with other books attempting this. As a bonus, I expect that many readers will come away with a better understanding of the process of evolution.

The Last Days of the Dinosaurs is available from our online bookstore.

**** Handsomely illustrated and accessible

 Reconstructing how dinosaurs behaved from just their fossilised bones might seem like science fiction but is very much science fact. In Dinosaur Behavior: An Illustrated Guide, veteran palaeontology professor Michael J. Benton joins forces with palaeoartist Bob Nicholls to do what it says on the tin: write a richly illustrated introductory book on dinosaur behaviour that is well-suited for novices.

In Dinosaur Behaviour, Benton takes the reader through five main topics: physiology (which sets the pace for everything else), locomotion, senses and intelligence, feeding, and social behaviour (which includes courtship, reproduction, parental care, and communication). One or several ‘forensics’ boxes in each chapter introduce the basic gist of certain methods.

Reading through this book, it becomes abundantly clear that our understanding of dinosaur behaviour relies on two approaches. Though Benton does not mention it as explicitly as in his previous book The Dinosaurs Rediscovered, the first of these is new high-tech toys and tools. Examples include computed tomography (CT) scanners, normally used in hospitals, to make detailed X-ray scans of fossilised brains (so-called endocasts) and so determine brain anatomy. Or finite element analysis normally used in engineering to model forces and stresses on jaws and teeth and so determine e.g. bite force. The second approach is ‘old-fashioned’ comparative anatomy and ethology: it pays to have a good knowledge of natural history when you are a palaeontologist. One example is the histological study of fossil dinosaur bones. Cutting thin bone sections and examining these under a microscope shows that some dinosaurs closely resemble mammals and birds, supporting the idea that smaller species were endotherms (‘warm-blooded’, i.e. generating their own body heat). Or take the microscopic study of melanosomes (pigment-containing organelles) in fossil feathers to determine colour in life. A final example is the comparison of footprints made by modern running birds with fossil tracks to determine things such as gait and running speed. 

If you are well-versed in (popular) palaeontology, much of what is presented here will be familiar. Even so, I picked up interesting titbits. One example is a recent study of Psittacosaurus that describes a cloaca, the multipurpose orifice also seen in birds where the digestive, urinary, and reproductive tracts all open to the outside world. This suggests that dinosaur sex, for at least some species, was a matter of the appropriately named ‘cloacal kiss’ rather than the brandishing of reptilian genitals. Other insights fell into the embarrassing ‘I should have known this’ category. We tend to think of walking on two legs as something advanced because our mammalian ancestors walked on all fours, but for dinosaurs, it was the reverse; they started out bipedal and quadrupedality only evolved later in e.g. the large sauropods. Particularly interesting is the study by Kat Schroeder and colleagues who looked at fossil communities of theropods and noticed a so-called carnivore gap: there is a lack of medium-sized ones in the fossil record, even though there are medium-sized herbivores. One explanation could be that dinosaur eggs had an upper size limit, meaning that young carnivores hatched small and had an awful lot of growing to do. As they did, ‘they passed through a whole range of feeding modes, each step along the way acting like a different species’ (p. 137), effectively plugging the ecological niche of medium-sized carnivores.

Despite the broad range of topics, there are some curious omissions. The chapter on feeding e.g. discusses jaws, teeth, and the use of isotopes to determine diet, but not microwear analysis of teeth. What I found most surprising is that Benton does not introduce the concept of trace fossils or ichnology, their study. Yet, examples such as trackways (some possibly showing long-distance migrations), coprolites (fossil poop), and nests are all discussed here. Another surprising omission is that the two-page bibliography does not include most studies mentioned in the text, even though it references other technical articles.

Dinosaur Behavior is mostly very suitable for readers with little to no background in palaeontology. Benton explains even basic terminology (physiology, cannibalism) as he goes, though there is the occasional curveball. One example is the morphospace diagram showing a principal component analysis on page 131, which, I hope those with a background in statistics will agree, is a rather abstract way of visualizing data that requires a bit more explanation than is given here. Though the book is published by Princeton University Press, it has been produced by UniPress Books who can be considered the spiritual successor to popular science publisher Ivy Press. What this means is that information is accessibly presented in bite-sized sections on one or several page spreads, with long sections further divided using subheadings. The downside is that this restricts how thoroughly topics can be explored. Leafing through e.g. Naish & Barrett’s Dinosaurs: How They Lived and Evolved shows more nuance in its chapter on behaviour.

Finally, I have to mention the excellent colour and black-and-white artwork by Bob Nicholls that livens up the text. I loved the drawing of courtship in Confusiusornis on pages 168–169. Despite the overlap in topic, this is all-new artwork compared to Locked in Time. Other diagrams have all been carefully designed or redrawn, using colours where appropriate. The only design element that did not work for me was the choice of sans-serif font which made e.g. the letters ‘a’ and ‘o’ hard to tell apart. 

Serious palaeontology buffs might find the contents here somewhat superficial, but overall, this is a handsomely illustrated book that offers an accessible introduction suitable for novices and possibly even curious high-school pupils. It would also make for a great gift. 

Dinosaur Behaviour: An Illustrated Guide is available from our online bookstore.