The Thoughtful Animal

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This week marked the release of Brian Switek’s (blog, twitter) first book, Written in Stone. I got my hands on a review copy a few weeks ago, and I have nothing but good things to say about it. (Disclaimer: I was provided with a free review copy of the book, without any expectation that I’d review it on my blog or elsewhere.)

Written in Stone is a highly-accessible, engaging book which takes the reader simultaneously through the story of vertebrate evolution and the story of the scientists who – quite literally – uncovered it. The book’s main success might be in its seamless transition back and forth between the narrative storylines and the specific scientific findings. The book is chock full of details, and yet they are presented in such a way that you are kept interested and engaged throughout, wondering what’s going to happen next. Who knew that bumps and notches on bones could be so thoroughly fascinating?! Written in Stone is, in a sense, the telling of the ultimate evolutionary detective story.

As someone who has been a reader of Brian’s blog Laelaps for several years already, it was nice to see echoes of posts that he had written months or even years earlier, and how they connected to other ideas from within the broader perspective of vertebrate paleontology. As someone who studies the evolution of behavior and cognition, I was hoping for a bit more on what the fossil record can tell us about behavior, and while there was some, the clear focus was on comparative anatomy. In that sense, this was the perfect book to bring me up to speed on the evolution of anatomy. While drawing connections between fossils and behavior (as you’ll see below) is fraught with difficulties, any student of evolutionary psychology (broadly construed) should read this book to gain a deeper understanding of evolution and the fossil record.


Brian took a few minutes out of his very busy schedule to answer – in depth – a few questions that I had, about his writing process as well as some more specifics regarding the content of the book:

Jason Goldman: I think one of the reasons why the book works so well and keeps readers (or at least, me) engaged is that there is just so much squeezed into every page, so the narrative moves along at a good pace. But to get so many details into each chapter, you must have done TONS of research – not only on the science but also on the historical context surrounding the scientific discoveries as well as the personalities of the scientists themselves. Did you have a process for organizing your research? How did you determine what deserved inclusion in the text and what was better left in a footnote or in the references list?

Brian Switek: Thanks, Jason – I am glad that the effort shows! I was inspired to write a book about evolution about four years ago, but it took three years of research to narrow down the story I wanted my book to tell. From there things progressed much more rapidly. After preparing three sample chapters to entice an agent and a publisher, I wrote the bulk of the original manuscript between September and December of 2009.

Blogging definitely proved advantageous during the writing process. Through feeding my blogs – Laelaps and Dinosaur Tracking – I was able to keep up with the latest research and collect the disparate pieces of information which eventually found their way into the mix of the book. I did not blog with the intention of including the material in the book, but blogging about science kept relevant material and ideas fresh in my mind (in addition to acting as places to practice my writing).

When it came down to actually writing each chapter, though, I did have a specific strategy. The first thing I had to do was construct a framework for the concepts and examples I was going to employ. Without a narrative, each chapter would just turn into an unorganized tangle of dead-ends. (You should have seen some of my early drafts. They were atrocious.) With that in mind, I simply wrote out everything I could immediately recall about the subject with the goal of creating a narrative thread. I didn’t sweat the details, but I did make notes about areas where I needed concrete examples or more evidence.
With this outline in place, I dove into the literature for examples. I was already familiar with some ideas or studies which were easily integrated into the story, but to make sure that I was not missing anything I created a list of papers for each chapter and read each of them for any details which may have slipped past. How heavily I had to mine the literature differed from chapter to chapter. The chapters on feathered dinosaurs and early whales, for example, were easy to write because I was already very familiar with those subjects, whereas I was less familiar with the evolution of early mammals and required more background reading to write that chapter.

Editing came next. I usually rewrote each chapter paragraph-by-paragraph, smoothing out rough patches and making sure that I had balanced accuracy with accessibility. I didn’t keep an exact count, but I think I edited each chapter an average of three times (before it went off to my publisher for suggestions from my editor), and I rewrote the introduction and conclusion several times. Those were actually the most difficult parts of the book to write, and I saved them for last.

I usually saved personal opinions, technical caveats, and other tidbits for the endnotes. If something was interesting, but had no natural place in the flow of the story, I plunked it down in an endnote. Some are fun, and some are technical, but I am already glad that I included some of them. For example, in the chapter on the origin of mammals I mention the uncertain evolutionary placement of an ancient collateral relative of mammal ancestors called Tetraceratops. It was just a little technical notice for those who wanted a little more information, but since the book went to press a paper has appeared in the journal Acta Palaeontologica Polonica which redescribes this enigmatic creature. The average reader probably won’t care, but I would like to think that a paleo enthusiast who wants to know more might Google the name and turn up the new research as a result of seeing the endnote.

Unfortunately, however, there were a few sections of the book I had to cut due to concerns over length. One was on the origin of primates. I wanted to review the evolutionary radiation of archaic primates which provided the context for early human evolution, but that chapter was so long that something had to be tossed (and, given that the introduction talks about the origin of anthropoid primates, I had covered at least some of the subject elsewhere in the book). I hope that I will eventually get to return to the story at some point in the future – it is one of the great, lesser-known tales in evolutionary history.

JG: It’s amazing how much you can learn from fossils, especially in terms of comparative anatomy. But I was wondering what (if anything) can be learned about behavior and cognition from studying fossils? There were only a few places in the book (that I recall) that briefly touched on behavior; does that reflect the fact that there isn’t much to be gleaned about behavior from fossils, or does it simply reflect your personal interests?

BS: I do mention behavior at various points in the book, but you’re right that cognition and behavior do not form major threads within the story. I was primarily concerned with anatomical change over time – the sort of examples which would help people understand how terrestrial mammals were adapted into whales and how our skeletons are built on a body plan which originated among the early tetrapods over 370 million years ago. Where aspects of behavior intersected the storyline, I included them, but my emphasis was more on changes in form rather than behavior.

In general, behavior and cognition – especially the latter – are difficult to perceive from the perspective of the fossil record. How much a paleontologist is able to reconstruct depends on the fossil evidence available and what we have been able to glean from living animals. If you know where to look, though, traces of fossil behavior can be starkly apparent.

Trackways are the most obvious examples of fossil behavior. Every footprint can tell us something about how the animal moved, and exceptional trackways of various types can act as windows into the lives of individual animals. One of my favorite examples is a recently-discovered trackway from China of several dromaeosaurid (“raptor”) dinosaurs moving side-by-side in the same direction. Does this mean that these dinosaurs were pack hunters like the Velociraptor of Jurassic Park? The traces don’t tell us anything about hunting behavior, but they are consistent with the idea that some of these dinosaurs were at least occasionally gregarious. There is a lot of cautious language there, yes, but the important point is that the tracks record a brief few moments in time when these dinosaurs walked together.

Since I have had dinosaurs on the brain lately, two other examples spring to mind. Just a few weeks ago paleontologists published evidence that Tyrannosaurus rex sometimes ate the remains of its own species. This hypothesis is supported by distinctive toothmarks on Tyrannosaurus bones which could not have been made by any other known theropod living in the same place at the same time, and the fact that scientists found toothmarked bones from at least three Tyrannosaurus hints that cannibalism might have been relatively frequent for this dinosaur (particularly considering how many tyrannosaurs never made it into the fossil record for one reason or another). From just a few bones, paleontologists may have detected an important aspect of the life – and death – of individual Tyrannosaurus.

Triceratops bones, too, show damage made by members of their own kind, but for a different reason. Numerous skull bones from this dinosaur bear distinctive lesions which are consistent with the way Triceratops would have locked horns with each other. It had long been suspected that these dinosaurs were sparring with each other, but this was as solid a confirmation as could be hoped for (barring the discovery of two Triceratops skulls locked together, like the two mammoths which got stuck on each other’s tusks and died together).

Cognition is a bit more difficult to get at. Exceptionally-preserved skulls and endocasts allow us to study the brain anatomy of many extinct creatures, but without living specimens it is near-impossible to study what their thought processes might have been like. Even so, the information which is available to paleontologists can be used to investigate a few hypotheses about intelligence. According to the “social brain hypothesis”, gregariousness helped drive the acquisition of high levels of intelligence among carnivorous mammals (e.g. wolves and spotted hyenas). In 2007, however, John Finarelli and John Flynn published a study in PNAS which looked at how brain size – a proxy for intelligence – related to the inferred sociality of carnivores in the fossil record. They found that brain size increased in multiple carnivore lineages which were both classified as social and solitary, and so they suggested that evolutionary increases in brain size are probably attributable to different pressures in different lineages. Assumptions are involved in this study, of course, and we can’t directly observe the social behavior of fossil taxa, but I mention it here to show that paleontologists are interested in testing ideas about intelligence and behavior.

Behavior is difficult to study in the fossil record. All we get are snippets – footprints or bite marks or other traces which may represent little more than a split second in the life of an individual animal. Still, I think it is amazing that we have these traces at all, and paleontologists regularly consider the behavior of extinct animals when they feel they have something solid to work with.

JG: Thanks for your time, Brian, and for sharing your thoughts with me and my readers!

Written in Stone is available in paperback now. I was provided with a free review copy of the book, without any expectation that I’d review it on my blog or elsewhere.