I have written previously that deducing behaviour of extinct animals from fossils millions of years old might seem science fiction, but is very much science fact. That said, in his previous book, English palaeontologist David Hone pointed out that dinosaur behaviour is the one area where we see the greatest disconnect between what we know and what people think we know. His new book Uncovering Dinosaur Behavior is a sobering reality check for the lay reader, but I suspect that even palaeontologists might come away wondering whether there is anything we know for sure. Concise, well-structured, and beautifully illustrated by palaeoartist Gabriel Ugueto, this is a superb book that transcends “merely” being a good popular science work by also addressing professional palaeontologists.

Uncovering Dinosaur Behavior: What They Did and How We Know, written by David Hone, published by Princeton University Press in November 2024 (hardback, 232 pages)

Uncovering Dinosaur Behavior opens with a very clear mission statement: what the book is and is not about, who it is for, and even what its potential weak points are. Hone writes about dinosaur behaviour, yes, but this is more than a catalogue of studies showing that species X likely did behaviour Y. He is aiming for a more integrated work, explaining how we figured these things out and offering advice on how to resolve conflicting results and answer remaining questions. His target audience encompasses dinosaur enthusiasts, of course, but he is additionally aiming at both palaeontologists interested in animal behaviour and ethologists interested in dinosaurs. He is upfront about the potential weaknesses: in trying to serve several masters, he might please none. Furthermore, he unapologetically follows the biases of the existing literature that emphasizes the charismatic megafauna at the expense of a broader take on dinosaurs at large. Having explicitly laid his cards on the table, Hone follows through with a logically structured book.

Three introductory chapters cater to both palaeontologists and ethologists by providing primers on dinosaurs, the fossil record, and the study of animal behaviour. You will find both a helpful appendix briefly introducing all major dinosaur lineages, and an introduction to Niko Tinbergen’s four famous questions of why an animal behaves the way it does that became the foundation for ethology. One of the chapters introduces the basic biology that both determines and limits dinosaur behaviour; topics such as activity patterns (when during the day are you active?), habitat choice, physiology, posture, and locomotion. A final important concept is extant phylogenetic bracketing, that is, looking at the behaviour of the nearest living relatives of dinosaurs (birds, crocodilians, and reptiles more widely). This will help you determine how far back in time a certain behaviour likely evolved. Armed with all of the above, you should be better able to judge whether behaviours inferred for dinosaurs are theoretically possible, plausible, or even likely.

Hone here also lays out his challenge to fellow palaeontologists to produce more rigorous science, giving you a set of eleven guidelines that he published together with Chris Faulkes in a 2014 paper. He has observed several recurrent problems with how data is used, interpreted, and presented, leading to misrepresentation and over-extrapolation of behaviour far beyond what the data supports. His philosophy is to “always favor a degree of uncertainty or lack of confidence in a result, rather than embracing an interpretation confidently that may be wrong” (p. 35).

“[The] target audience encompasses dinosaur enthusiasts, of course, but he is additionally aiming at both palaeontologists interested in animal behaviour and ethologists interested in dinosaurs.”

The remainder of the book examines five broad categories of behaviours. Given what I just wrote about Hone’s attitude to the research field, I can now explain why I introduced this book as a sobering reality check. Take the frequently depicted idea that dinosaurs lived in groups, with a certain franchise making hay out of pack hunting. Now, many animals alive today live socially, and there are advantages to doing so, but how do you deduce this from fossils? The problem with bonebeds is that fossils found in groups did not necessarily live or even die together: the taphonomic history (what happened between death and burial) matters. But equally, many groups will have lost members individually: solitary fossils do not exclude social behaviour. Trackways can similarly not be taken at face value. Beyond the challenge of assigning them to species, determining if they were laid down together is challenging, and even if they were, many interpretations are possible beyond social behaviour.

Hone is similarly circumspect when it comes to signalling and reproduction. He highlights what we know and what remains unknown. For instance, dinosaurs likely used visual and auditory signals, and they laid eggs. But did they use touch, taste, or smell? How did they mate? How many eggs did a female typically lay? What amount of care did parents bestow on offspring before and after hatching? We have data and tentative hints for some species, but for many questions, we cannot go much beyond generalities. The situation is better for combat: many species sported implements that intuitively look like weapons, but how and on whom they used them is harder to determine. Studies have furthermore focused on a small number of species while ignoring many others. Feeding biology is the area that has the most robust support, bringing together many independent lines of evidence such as biomechanics, trace fossils, isotope data, tooth microwear analysis, stomach contents, and coprolites. Even here, though, such full pictures are only available for a handful of species.

Overall, interpreting dinosaur behaviour is “profoundly difficult” (p. 152) due to both the limitations of the fossil record and the diversity and plasticity we see in the behaviour of animals alive today. The problem he observes is that “much of the scientific literature tends toward a confidence in interpreting dinosaurian behaviors that probably should not be there [while failing] to recognize alternate possibilities and the inherent uncertainty of interpreting ancient behaviors” (p. 153). That sounds pretty damning but he also recognizes that the field has come a long way from early guesswork and extrapolations to more rigorous methods that take seriously the fact that dinosaurs were once real, living animals rather than mythical monsters.

“Hone’s work […] hit the sweet spot of the kind of depth I look for in my popular academic books: fairly technical, thought-provoking, never shirking the hard questions, and yet admirably brief”

Compared to the previously reviewed The Future of Dinosaurs, which had a somewhat haphazard ordering of its chapters, Uncovering Dinosaur Behavior benefits from an excellent and logical structure that flows very well. However, some noticeable typos did slip through again, despite the extensive proofreading. All chapters come with a helpful summary and an interesting case study; I thought the one on ankylosaurs and what their tail clubs were used for was particularly compelling. I also have to praise the fantastic illustrations by Ugueto. The colour plate section is mouthwatering eye candy, and there are numerous classy and useful black-and-white drawings and diagrams throughout the book. Some of the black-and-white photos of fossils are harder to decipher, and I would not have minded had some been included in the colour plate section.

Uncovering Dinosaur Behavior was published about a year after Michael J. Benton’s Dinosaur Behavior: An Illustrated Guide, meaning Princeton University Press now has two illustrated books on this topic. Which one do you choose? In my review, I highlighted that Benton’s is an introductory book for novices that starts from first principles. Hone’s work, though very accessible, is more advanced and, for me, hit the sweet spot of the kind of depth I look for in my popular academic books: fairly technical, thought-provoking, never shirking the hard questions, and yet admirably brief at 207 pages. One thing Hone does not do is introduce and explain the various techniques. He assumes that phrases such as isotope data, palynology, and finite element analysis mean something to you and do not require more than a brief definition. If you find your eyes glazing over at these terms, maybe start with Benton’s book. For everyone else, however, Uncovering Dinosaur Behavior is a superb book that should be your go-to reference for a thoughtful appraisal of what we know about dinosaur behaviour.

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

Uncovering Dinosaur Behavior

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

There are plenty of popular palaeontology books that tell you everything we know about dinosaurs and several excellent examples have been reviewed here in the past. For the 500th review on this blog, I take the road less travelled. In The Future of Dinosaurs, English palaeontologist David Hone flips the script by asking what we do not know about dinosaurs. I have been meaning to review this book since it was first published in 2022. With the recent publication of his latest popular book on dinosaur behaviour, I decided to make time and read up on Hone’s work. First up, an exploration of our ignorance that is as much a celebration of all we have learned and how we have learned it.

The Future of Dinosaurs: What We Don’t Know, What We Can, and What We’ll Never Know, written by David Hone, published in Europe by Hodder & Stoughton^[1] in March 2022 (hardback, 252 pages)

This book seemingly flows from Hone’s efforts at science communication. In speaking to the general public, he has noticed the sometimes large disconnect between what palaeontologists know and what people think they know. Thus was planted the seed for a Rumsfeldian^[2] book about what is unknown, what is knowable, and what is unknowable in palaeontology. Fifteen chapters run the gamut of topics and chart the cutting edge of our ignorance and our understanding. Given the large number of popular dinosaur books, it is a refreshing take on the genre that is chock-full of interesting insights.

Take some examples of unknowns. What is the total number of species that ever evolved and how many can we still expect to find? That is unknown, though if you plot discovery rate against time you expect a curve that will eventually level off. Where we are on that curve? Who knows! The rate at which we name new species each year shows no signs of slowing down yet. Did sauropods have multi-chambered stomachs like today’s large herbivores? That is unknown, as soft-tissue preservation of this kind is exceedingly rare. All we have for now is a spectacular fossil of the small theropod Scipionyx where the guts were infilled with sediment, resulting in a remarkable cast of an otherwise unremarkable digestive tract.

Many things are knowable though, with questions often being an absence-of-evidence problem that can be resolved with more fossils and more research. Anatomical features such as the frills of ceratopsians are usually bent and broken during the long journey through time, but detailed scans and computer analyses allow us to undo such distortion virtually. It is still early days for this technique, but we have the fossils, so with time, effort, and experience, our knowledge is likely to improve. Were dinosaurs sexually dimorphic? That is, did males and females differ noticeably in size or appearance? Since most species are only known from one or a few specimens, we just do not have the required sample sizes yet, and where we do, we have not found such differences. However, given the large diversity of dinosaurs, there are bound to have been sexually dimorphic species, so with more fossils this question is ultimately answerable.

“[The] disconnect between what palaeontologists know and what people think they know […] planted the seed for a Rumsfeldian book about what is unknown, what is knowable, and what is unknowable in palaeontology.”

The unknowables are some of the most fascinating and frustrating questions discussed here. Are tooth marks on bones the result of predation or scavenging? Predators readily did both and the two are near-indistinguishable. “This is annoyingly trite as a revelation about their behaviour” (p. 183), but the data simply do not allow for firmer conclusions. The small asterisk is that some questions are not strictly unknowable, but would require such unlikely fossils that, for all intents and purposes, we can consider them unknowable. Others require completely new types of evidence that we had not previously conceived of. For example, the colour of dinosaurs was considered unanswerable until recently. The discovery of ancient biomolecules such as melanosomes changed that somewhat, as their shape corresponds to colour. “It is as if you went to a paint store and each colour was in a uniquely shaped pot” (p. 151), is how Hone memorably describes it. But he quickly tones down the enthusiasm: only certain colours are melanosome-based and sampling them is destructive, so palaeontologists try and limit it to spot sampling. Our knowledge is thus far less certain and complete than artist reconstructions suggest.

Despite my enthusiasm for Hone’s three-pronged approach, I do have some criticism. First is that the order of chapters feels somewhat haphazard, with the book jumping around between different topics and levels of organisation. Some closely related topics are scattered over the book with e.g. chapters on habitat and ecology separated by seven chapters. Others feel out of order. Why start with a chapter on extinction when, by your own admission, anatomy (now chapter 7) is the fundamental topic on which everything else in palaeontology is built? I would have reorganised the chapters for a more logical structure. Second is that the writing is sometimes not the most graceful. Take the book’s subtitle: to me, it cries out for a third “know”; leaving it out of the middle clause is just jarring. There are examples of long, run-on sentences expressing several ideas that should have been separated. Other sentences are awkwardly constructed, or switch from passive to active voice midway, with my brain expecting one thing but Hone writing something else. Now, I do not want to over-egg this: big picture, they are all minor blemishes on what is otherwise an entertaining and engaging book.

Next to Hone’s stated running theme of the disconnect between the public’s perception of our knowledge and our actual knowledge, some other fascinating themes emerge. One example is the nature of the fossil record and how it can mislead through both a glut and a dearth of fossils. Bonebeds are often significant sources of information due to the large number of bones preserved, but if they resulted from abnormal circumstances such as catastrophic floods, droughts, or volcanic eruptions, how representative are such assemblages? They risk giving “a very misleading picture of what lived locally and in what kind of numbers” (p. 194). At the other extreme are the low odds of preserving the statistical outliers such as the largest or oldest individuals. Similarly, newly emerging species often occur in low numbers and limited geographic areas, so the age of a species should be considered a minimum estimate. The odds are very much stacked against the earliest, if not the first, representatives of a species entering the fossil record, surviving to the present day, and then being discovered rather than lost to erosion.

“[…] some other fascinating themes emerge. One example is the nature of the fossil record and how it can mislead through both a glut and a dearth of fossils.”

Another fascinating theme that emerges is the impact of the huge size range of dinosaurs on their biology and ecology. Dinosaurs never evolved to be rodent-size small; as Elsa Panciroli discussed, mammals occupied that ecological niche. Furthermore, independent of their adult size, dinosaurs hatched from eggs as small juveniles and had to go through sometimes gargantuan growth spurts. Hone points out that juveniles of sauropods and large theropods simply could not have been eating the same food and playing the same ecological role as the adults. Fellow palaeontologist Michael J. Benton recently highlighted research that suggested carnivores passed through a range of feeding modes as they grew up, sequentially occupying different ecological niches and effectively acting as different species on their way to adulthood. Similar shifts might have also happened to metabolism, Hone suggests. Adult sauropods were so large that their surface-to-volume ratio meant they did not need to actively generate body heat to keep warm (a condition known as gigantothermy). But the same could not have been true of small juveniles; seeing their growth rates they likely were endotherms, actively generating body heat. If true, this would be remarkable, as we know of no living species that so radically change their physiology growing up.

Despite some minor flaws, The Future of Dinosaurs is both a fascinating exploration of our ignorance and a celebration of how much we have learned from sometimes very challenging source material. By tracing the contours of where our knowledge ends, Hone gives you an insider’s look into the discipline—from its storied history to today’s cutting-edge technologies. It seems almost prophetic that he writes that behaviour is the subject where we see the greatest disconnect between what palaeontologists know and what the public thinks they know: he tackles this topic in his recently published Uncovering Dinosaur Behavior to which I will turn next.

1. ↑ Note that in the USA, this book was published by Princeton University Press with the title How Fast Did T. rex Run?: Unsolved Questions from the Frontiers of Dinosaur Science.

2. ↑ I am, of course, referring to United States Secretary of Defense Donald Rumsfeld’s briefing where he popularised the notion of known knowns, known unknowns, and unknown unknowns.

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

The Future of Dinosaurs

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

As a bonus to conclude my (now) four-part review series on the history of taxonomy, I am looking back to Susannah Gibson’s 2015 Animal, Vegetable, Mineral? After dealing with biographies of Linnaeus and Buffon, and then Ragan’s Kingdoms, Empires, & Domains, her book was just crying out to be read next. Given that those three were all published in 2023 and 2024, I will leave a comparison for the end of this review and first judge this book on its merits. As it turns out, this is an easy and intriguing read that I ignored for far too long.

Animal, Vegetable, Mineral? How Eighteenth-Century Science Disrupted the Natural Order, written by Susannah Gibson, published by Oxford University Press in July 2015 (hardback, 215 pages)

Gibson is an affiliated scholar at the Department of History and Philosophy of Science, University of Cambridge. Though she keeps a low profile online, a little research shows that since this 2015 debut, she has written two more books, The Spirit of Inquiry (2019) and Bluestockings (2024), showing a continued engagement with (science) history.

Even as I acknowledge Ragan’s point that dividing the natural world into animals, vegetables (i.e. plants), and minerals was neither rooted in prehistory nor universal, it cannot be denied that for centuries it was a widely accepted division. The 18th century was a time of radical change, though, with e.g. the French Revolution and the Scottish Enlightenment causing political and societal upheaval, while colonialism and empire-building brought home a raft of organisms previously unknown to Europeans. All this caused people to question traditional ideas and beliefs, including scholars who re-examined those creatures that had always straddled the border between different kingdoms. Importantly, while science was advancing rapidly, “this greater abundance of knowledge did not always lead to agreement” (p. 166), so Gibson connects her examples to larger debates of the era.

Zoophytes, those creatures that mix traits of animals and plants, are an appropriate place to start. She is on the ball in not attributing the term to Aristotle (as Ragan was at pains to emphasize in Kingdoms, Empires, & Domains), even as he got the whole zoophyte ball rolling with his interest in polyps, corals, sponges, and other marine invertebrates. They were still being discussed in the 18th century when naturalist Abraham Trembley garnered attention with his description and study of freshwater polyps (distant relatives of jellyfish in the animal phylum Cnidaria). Next to its biology combining elements of animals and plants, it has the remarkable ability to completely regenerate and multiply when cut into pieces. Trembley’s work fed into the larger ongoing debate between materialism (all is matter and energy, and matter and energy is all) and vitalism (living beings possess a special spark, a vital force). It spurred such questions as: “Is cutting a polyp into two a separate act of creation?”, “Is the soul then split into two?”, and “Where is God in all this?”

“while science was advancing rapidly [in the 18th century], “this greater abundance of knowledge did not always lead to agreement” (p. 166), so Gibson connects her examples to larger debates of the era.”

Linnaeus used sexual reproduction as a basis for plant taxonomy and drew analogies between animals and plants, even as his critics pointed to plants reproducing without seeds. This work in turn fed into larger debates about reproduction, which saw preformationism pitted against epigenesis. The former held that God had created everything in one go such that future offspring were stacked inside each other like so many Matryoshka dolls; the latter held that life resulted from the gradual organisation of disorganised matter via the laws of physics and chemistry—no God required. Note that Gibson illustrates this with animal rather than plant examples, including the historical dispute between Albrecht von Haller and Caspar Friedrich Wolff on chicken eggs and the unbelievable work of Lazzaro Spallanzani who kitted out male frogs with tiny waterproof trousers (!) to test the idea of egg preformation.

Gibson has a knack for uncovering some of history’s whackier tales. The chapter on minerals, which includes our struggle to understand fossils, might not feature a link to larger philosophical debates but does come with two intriguing character stories. The history of William Smith’s first stratigraphical map of Britain that relied on fossils has been told before, but the amazing story of Johann Beringer who fell victim to an elaborate hoax as he was trying to understand fossils was completely new to me. Here, as elsewhere, Gibson is a sensitive historian. Even as she defends some scholars from modern accusations of gullibility, pointing out that their methods and logic were sound but their knowledge a product of its time, she subtly scolds others for not crediting the unnamed slaves, fishermen, or gardeners who helped them make the observations for which they are remembered.

My only real criticism is that I am not fully convinced by one important line of her argumentation. She repeatedly contends that new findings in science had serious ramifications for society at large: “anything that could be used to show that nature didn’t always echo religious orthodoxy was dangerous […] abstract scientific questions could have all-too-concrete consequences” (p. 177). All this academic chatter of border-straddling animals and plants might cause people to question the natural order of things! I think it is an intuitively appealing idea, but what is the evidence for it? Yes, she shows how Linnaeus’s ideas on plant reproduction were readily satirized, even as they offered an opportunity to discuss sex in polite company. However, what were the “bigger religious and social implications” (p. 78) of the interest in Trembley’s polyp research? And how did the discovery of the Venus fly-trap that seemed to defy the God-given category of plants cause people to question social stratification? Maybe I am being too literal-minded, but did people ever revolt, pitchfork in one hand and scientific paper in the other? Could you not just as well argue that the revolutionary spirit in society bled into science, or, equally likely, that the two influenced each other? To my taste, much is asserted here without providing clear examples, though I will gladly admit my ignorance of this historical period. Perhaps the answer lies in her conclusion that in dismantling the familiar concepts of animals, vegetables, and minerals, naturalists gave society “a focus for asking a set of much bigger questions” (p. 188).

“Reading Animal, Vegetable, Mineral? a decade after its publication, how does it hold up? Actually, rather splendidly.”

To wrap up, I promised a comparison with the previous three books. Reading Animal, Vegetable, Mineral? a decade after its publication, how does it hold up? Actually, rather splendidly. For Linnaeus, Gibson relies on Lisbet Koerner’s biography and by and large agrees with Broberg’s book, except in a few details. For example, where Gibson writes that Linnaeus’s ideas were welcomed in England, Broberg argued this took time and the initial reception was lukewarm; and where she mentions the outrage caused by his writing on plant sexuality, Broberg contended this has been exaggerated. Gibson is briefest on Buffon but nails the core difference with Linnaeus that Roberts highlighted in Every Living Thing: Linnaeus preached an artificial system while Buffon countered that nature did not yield to such strict classification.

Most interesting is the comparison to Ragan’s book. Though Gibson’s first chapter is effectively an appreciation of Aristotle, she compresses the next two millennia. I think this is justified: as Ragan has so painstakingly documented, in essence not much happened beyond repeatedly redefining the concept of zoophytes. Even Cuvier remarked that Aristotle “left very little to do for the centuries after him” (p. 15). Gibson thus focuses on 18th-century developments while her epilogue is a speed-run through 19th and 20th-century biology. In a mere 215 pages, her book is of course no match for Ragan’s encyclopedic overview, but that was never the intention. That said, Ragan did not mention fossils or the wider social context. Can this book be a starting point if Ragan’s book seems too intimidating at first? If you finish it fascinated by zoophytes and want to immerse yourself deeply in the history of that concept, then, certainly, yes. But, more than a mere prelude, Gibson’s work readily stands on its own two feet even a decade later, covering subjects and stories not encountered in these three later books. Animal, Vegetable, Mineral? is a whip-smart book that I ignored for far too long.

Animal, Vegetable, Mineral?

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

This is the first of a trio of reviews in which I take a brief detour into ants and collective behaviour more generally. Next up are entomologist Deborah M. Gordon’s 2010 book Ant Encounters and her recent The Ecology of Collective Behavior, but first The Ant Collective. This one grabbed my attention as soon as it was announced. Not a comic or graphic novel, but an A4-format book about ant colonies that is chock-a-block with infographics? Yes, please! Showcasing the best of what science illustration can be and combining it with a genuine outsider’s interest in entomology, The Ant Collective makes for a wonderful graphical introduction that will appeal to a very broad audience of all ages.

The Ant Collective: Inside the World of an Ant Colony, written by Armin Schieb, published by Princeton University Press in May 2024 (hardback, 128 pages)

This book was originally published in German in 2022 as Das Ameisenkollektiv by Kosmos Verlag. It was quickly snapped up for translation into French and Spanish (always a sign of a book’s popularity) before Princeton University Press published it in English in 2024, courtesy of translator Alexandra Bird. Armin Schieb is a freelance science illustrator based in Hamburg, Germany, and this book derives from his master’s thesis in Informative Illustration at the Hamburg University of Applied Sciences. His portfolio shows infographics, 3D models, and cover illustrations for a range of clients, from magazines to newspapers to publishers, but this book represents his first published work to date.

Based on direct observations, sketches, and photos of red wood ants (Formica rufa), Schieb has designed 61 highly detailed computer-generated illustrations showing ants from a bug’s eye perspective that entomologists can only dream of. The eight chapters each contain a mixture of full-page spreads with naturalistic 3D renderings of landscapes full of ants, and pages with numerous smaller infographics that explain how colonies function. Annotations are scattered throughout to provide context to what you are looking at. Neatly, many of the full-page spreads continue overleaf, forming eight-page tableaux. One can only imagine what they would have looked like if the publisher had included them as gatefolds!

Next to obligatory drawings introducing ant anatomy, the focus of this book is on colony-level behaviour, with chapters depicting e.g. nuptial flights, nest establishment and construction, seasonal cycles of nest maintenance, foraging, trail formation, food acquisition and defence, reproduction, nest defence, and the formation of new colonies. The clever use of cutaway illustrations reveals processes that normally play out unseen underground.

“Schieb has designed 61 highly detailed computer-generated illustrations showing ants from a bug’s eye perspective that entomologists can only dream of.”

There are some memorable scenes in here showing e.g. green woodpeckers and boars raiding ant nests. The woodpecker illustration stands out in particular. Red wood ants defend themselves by spraying formic acid and are normally inedible. The birds, though, have turned the tables on the ants twice over, picking them up in their beak and rubbing them on their feathers where the ants discharge the contents of their poison glands. As an added bonus, the formic acid repels feather parasites. This whole story is illustrated by overlaying several semitransparent motion frames of a woodpecker twisting its head and is glorious to behold. Elsewhere, Schieb uses motion blur to good effect to highlight the action-packed nature of spiders and antlions catching hapless ants.

Needless to say, this book is full of fascinating titbits of information. Schieb explains the phenomenon of age polyethism that I first encountered in Ant Architecture. Young ants tend to stay inside or close to the nest, while older ants venture further out to do the dangerous job of foraging (though see my next review of Ant Encounters for some criticism of this idea). Speaking of the next review, Schieb (perhaps unwittingly) offers an excellent illustration of colony behaviour arising through interaction networks when he shows how foraging trails wax and wane as a function of behavioural interactions between ants. There is similarly a deft explanation of the anatomical details of the eyes that allow them to see both polarized and unpolarized light: straight or spiralling stacks of light-sensitive tubules. It is one of those concepts where a picture says more than a thousand words. The only criticism I have of this particular section is that I would have opened it with the otherwise excellent illustration explaining sky polarization. Additionally, I would have added an infographic that explains what polarized light actually is, as it is a surprisingly tricky phenomenon to explain. Michael Land’s book Eyes to See contains a good picture, whereas Schieb basically takes it as a given that readers will understand what he means when writing that “almost all photons in a polarized light ray vibrate in the same plane” (p. 64).

“Over the years, I have reviewed some seriously impressive photographic books on ants […] The Ant Collective rubs shoulders with the greats where visual content is concerned.”

The promotional blurb for the book mentions it draws on the latest science though I was left somewhat confused when I finished it. Schieb is obviously not an entomologist but a graphic artist. There is no mention of the project having benefited from one or several entomologists acting as consultants to give the contents the once-over for scientific accuracy. There is no acknowledgements section where Schieb credits scientists for advice and input. There is not even a list of references or recommended reading included. Or is there? Since I do not have access to the German original I had to resort to some online sleuthing and found a preview on Amazon.de that includes the reference list on p. 126 (shown here). This reveals that, yes, he has consulted books and scientific papers in both English and German, including that evergreen The Ants, an older edition of Insect Physiology and Biochemistry, and both specialist and general German books on forest insects. So, Schieb did his homework, Kosmos referenced it, but for some bizarre reason, Princeton simply omitted it, as the page between 125 and 127 is… blank! Did I just happen to receive a dud to review? Checking eight other copies at the warehouse of the bookseller where I work confirmed that, no, this is a feature, not a bug. Hopefully, if there are future print runs, this is a detail that can be rectified, as it could easily leave readers with the wrong impression.

Over the years, I have reviewed some seriously impressive photographic books on ants, covering amongst others army ants, desert ants, and myrmecophiles. Despite being a slimmer volume written for a general audience, The Ant Collective rubs shoulders with the greats where visual content is concerned. This is a feast for the eyes that will lure newcomers into entomology but should also please seasoned myrmecologists.

A final thing to note is that this book tells the biology of a single species. Wood ants are well-studied as far as ants go, but as the subtitle indicates, this is a look inside the world of a ant colony. It would be a mistake to come away from this book thinking that this is how colonies of all ant species function. As hopefully will become clear in the next two reviews of first Ant Encounters and then The Ecology of Collective Behavior, the world of ants is one of bewildering diversity, though themes and unifying principles are starting to emerge.

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

The Ant Collective

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

Jules Howard is no stranger to sex. A science writer and zoological correspondent, his gleefully amusing 2014 book Sex on Earth is particularly relevant to the topic at hand. Even there, however, eggs were just a sideshow. And therein lies the problem. Likely, the first question to be asked when eggs come up in conversation is how you like them for breakfast, or some hackneyed joke involving chickens. Focusing on the oology in zoology, Infinite Life retells the history of life, this time from the perspective of the almighty egg.

Infinite Life: A Revolutionary Story of Eggs, Evolution and Life on Earth, written by Jules Howard, published in Europe by Elliott & Thompson in May 2024 (hardback, 258 pages)

Howard’s approach in Infinite Life is to take the reader chronologically through the history of life, one geological period per chapter. Familiar as that framework might be for readers of popular evolutionary history books, it is the subject matter that is engrossing; eggs really have been a neglected topic so far. Consider, for example, that though we think of eggs as an animal invention, there have been egg-like precursors. Sometime between 1 to 2 billion years ago, cyanobacteria evolved a resting stage, “an armoured sleepsuit” (p. 9), known as cysts. These acted as “a device that propelled genetic material forwards in time” and you could say that here, in the Proterozoic Eon, “the egg—as a concept—was forged” (p. 12). It was only later, when the earliest animals started experimenting with sex during the Ediacaran, that the first true eggs—”vehicles for genetic mixing” (p. 22)—show up in the fossil record. It needs to be said that the evidence is confusing, fragmentary, and of poor quality, and not accepted by all palaeontologists.

Once the egg was established, Howard takes the opportunity to revisit several critical junctures in evolutionary history. In the Cambrian, for instance, a division took place between organisms with and without separate cell lines. Cnidaria, of which jellyfish are a member, belong to the latter group and produce eggs later in life by dedifferentiating body cells, effectively putting their developmental programme in reverse. Most other organisms you are familiar with (mammals included) at a very early stage of embryonic development split into germ cells (which exclusively produce sperm and eggs) and somatic cells (which go on to form the rest of the body). And this is just one of three important egg inventions during the Cambrian he discusses. Howard proposes several later critical junctures where eggs may have been an influential factor. For instance, the explosion in insect diversity during the Carboniferous might well be partially attributed to the evolution of the serosa, an armour-like covering that waterproofs eggs. The success of archosaurs in the Triassic, which paved the way for the dinosaurs, is traditionally attributed to several anatomical features but might also have had something to do with parental care of eggs and nests. Lastly, the evolution of a hardened eggshell was an important factor in the success story of the birds (Howard concedes a big intellectual debt to Tim Birkhead’s The Most Perfect Thing when discussing birds and their eggs).

“Familiar as [the book’s] framework might be for readers of popular evolutionary history books, it is the subject matter that is engrossing; eggs really have been a neglected topic so far.”

Other aspects evolved in tandem with eggs, and Howard touches on sexual reproduction (a costly endeavour that nevertheless has some critical advantages), sperm, a bewildering assortment of male genitalia that deliver sperm near eggs before the female wraps the egg in an impenetrable shell, and the placenta in those organisms that develop their egg cells internally. Especially that last organ, the placenta, is a bizarre evolutionary invention when you consider it. Embryos invade maternal tissue to aggressively obtain resources needed for growth, while mothers try to balance between providing for their developing offspring and somewhat inhibiting their demands. The real kicker in this story? The protein that allows maternal and placental cells to fuse originated in retroviruses.

One thing I noticed is that Howard leaves no opportunity unused to remind you that evolution proceeds without a grand plan. Early bombardments of the planet by space debris, “without any thought or forward planning, delivered the precursors for life” (p. 4). The arrival of invertebrates on land “had nothing to do with bravery or pioneering spirit or anything like that. Rather it was the stacking up of numbers, of trials, over thousands or millions of years” (p. 48). The arms race in birds between hosts and brood parasites such as cuckoos can result in beautifully patterned eggs “without any opinion or intelligence or any artistic nous of any sort” (p. 175). In a book for a general audience, it never hurts to remind readers of this.

Overall, Howard’s writing resorts to the occasional linguistic flourish but steers clear of both excessive humour and highly crafted creative writing. Instead, Infinite Life primarily relies on delivering interesting subject matter. Adding eggs to the mix makes for a fascinating retelling of the evolutionary history of life.

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

Infinite Life

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

Where evolution is concerned, the city is a cauldron exerting its own unique mix of selection pressures on the organisms living here. The metronome beating at the heart of this process is sex. For this book, retired physician Kenneth D. Frank has explored his hometown of Philadelphia in the Eastern US state of Pennsylvania and documented the astonishing variety of sex lives playing out right under our noses. Many of these organisms can be found in cities around the world. Remarkably well-researched and richly illustrated with photos, this collection of 106 one-page vignettes shows what avocational naturalists can contribute both in terms of observations and in terms of highlighting the many basic questions that are still unanswered.

Sex in City Plants, Animals, Fungi, and More: A Guide to Reproductive Diversity, written by Kenneth D. Frank, published by Columbia University Press in May 2022 (paperback, 175 pages)

That animals get up to all sorts of reproductive shenanigans is something I would know. I spent five years for my PhD degree looking at the sex life of a small fish, the three-spined stickleback, and especially how males have different options when it comes to siring offspring, known as alternative reproductive tactics. Frank, however, opens the book with some 30-odd vignettes on plants, reminding me that I really do not appreciate plants enough.

Take purple cliffbrake fern (Pellaea atropurpurea) that does not need to be fertilized by sperm and whose embryos emerge from somatic (i.e. body) cells. Jewelweed (Impatiens capensis) can form big showy flowers that are cross-fertilized (i.e. the regular bees-and-flowers story) or it can form smaller flowers that fertilize themselves under conditions of drought and shade. St. John’s Wort (Hypericum perforatum) can do it all: self-fertilization, cross-fertilization, double fertilization^[1], single fertilization, or no fertilization. All these species are well adapted for variable conditions in city environments. Meanwhile, a tree such as Norway maple (Acer platanoides) can change its sex over the course of days, producing male flowers followed by female flowers, or vice versa. This prevents self-fertilization, which is a measure of last resort from an evolutionary point of view as it produces offspring that are less genetically diverse.

“[…] this collection of 106 one-page vignettes shows what avocational naturalists can contribute both in terms of observations and in terms of highlighting the many basic questions that are still unanswered.”

The next major group Frank covers are insects and other invertebrates whose sex lives are just wicked. Male European paper wasps (Polistes dominula) are a lekking species, which means they congregate in a small area, the lek, to collectively advertise their presence in the hope of picking up a female. (One could theoretically argue that nightclubs fulfil a similar function in humans.) Male blue dasher dragonflies (Pachydiplax longipennis) are territorial and defend areas preferred by egg-laying females. The females can mimic the male in appearance and it seems these mimics avoid harassment by males. A problem for both sexes is light reflected by metal and glass, which is polarized—the light waves vibrate predominantly in one direction—and resembles light reflected by water. Some dragonflies end up defending the shiny surface of a car bonnet rather than a pond. Milkweed aphids (Aphis nerrii) are such pests as they reproduce through parthenogenesis: eggs develop into embryos without requiring fertilization, and all grow into females that will never mate. The bridge spider (Larinioides sclopetarius) thrives around outdoor lights, which form hubs where spiders “eat, meet, and mate” (p. 76). Males have secondary genitalia and first transfer their sperm to two so-called pedipalps: pom-pom-like appendages in front of their head that they use to inseminate females with.

In comparison, vertebrates seem tame. As in many other reptiles, sex in red-eared slider turtles (Trachemys scripta elegans) is temperature-dependent. What I did not know is they simply have no sex chromosomes! Male bluegill fish (Lepomis macrochirus) build nesting areas to which they attract females. Afterwards, they nurse the broods on their own. Some males, sneaker males, forego all this effort and simply intrude on an ongoing mating, releasing their own cloud of sperm in the water (the sticklebacks I studied do the same). Male eastern gray squirrels (Sciurus carolinensis) leave a mating plug in the female’s genital tract which is hypothesized to have one or more functions (including a sperm blocker to other males, a hormone booster, or maybe an anti-aphrodisiac pheromone releaser). European starlings (Sturnus vulgaris) are a fine example of a species that is socially but not sexually monogamous, as paternity tests have shown. Notably missing from the book are mammalian predators such as and coyotes that also thrive in city environments.

“Frank highlights where we know or suspect that certain strategies result in organisms either thriving or struggling in urban environments; not every organism can radically reorganise its sex life to take advantage of the city.”

The above is a small sample from the wide range of reproductive diversity on display in urban environments. Frank highlights where we know or suspect that certain strategies result in organisms either thriving or struggling in urban environments; not every organism can radically reorganise its sex life to take advantage of the city. Obviously, Frank has not observed all these phenomena first-hand, and the amount of research that has gone into this book is impressive. The reference section spans 32 pages, which is a lot considering the vignettes take up only 106 pages. Many include facts and data from five to ten different papers. He also uses this opportunity to highlight how many basic biological questions remain unanswered. For example, does nocturnal light pollution interfere with moths fertilizing flowers of white campion (Silene latifolia)? How do female dragonflies mimicking males mate and could this be a post-fertilization adaptation? Does artificial crowding in city parks cause male squirrels to become less aggressive over time? What Frank has done is track down nearly all the species discussed here: the book is richly illustrated with his (macro)photography, with some contributions by others.

As much as Sex in City Plants, Animals, Fungi, and More is a nicely curated collection of interesting nuggets, it lacks an overall narrative. In particular, the bigger picture of how reproduction translates into longer-term evolutionary changes is only occasionally hinted at. Menno Schilthuizen wrote a very entertaining account in Darwin Comes to Town, but it has become a serious subfield of evolutionary biology. As such, this is a popular science book that is great for dipping into (whether it would make for suitable bedtime reading depends entirely on what you are into…). And if you are looking for inspiration for student or PhD projects, the book provides numerous ideas of biological mysteries at your doorstep.

1. ↑ double fertilization is the default in flowering plants. One fertilized cell forms the embryo, and the other forms endosperm that offers nutritional support to the developing embryo.

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

Sex in City Plants, Animals, Fungi, and More

Other recommended books mentioned in this review:

__________________________________________________________________

It is tempting to call animal domestication humanity’s oldest and longest-running experiment, but professor of palaeobiology Marcelo R. Sánchez-Villagra would beg to differ. It is worth opening with a quote from The Process of Animal Domestication to set the tone: “domestication is actually pretty poor as experiments go; there are too many variables involved with little control, and no records of how things started” (p. 206). The excellent structure prevents the book from becoming an overwhelming infodump, making this a valuable synthesis of data across a large number of disciplines that will interest a wide range of researchers.

The Process of Animal Domestication, written by Marcelo R. Sánchez-Villagra, published by Princeton University Press in March 2022 (paperback, 296 pages)

Before delving in, let us consider the scope of this book. The Process of Animal Domestication focuses on genetics, evolution, development, and morphology. Such is the amount of research done on these topics that animal behaviour is barely touched on here. This would require a separate book and Sánchez-Villagra refers you to two texts published by CABI, to which I would add Grandin’s book on behavioural genetics. The bulk of the research covered here is on mammals (dogs feature prominently) and birds, with fish and insects getting two brief chapters at the end of the book.

Since many people own pets, and many more have been around pets or farm animals at some point, I am sure most of us think we understand domestication. How appropriate, then, the first chapter, that I would like to characterise as “everything you thought you knew about domestication is wrong”. Forget the notion of centres of domestication, or of it being a historic event: “Domestication is a process, a transition, without clear boundaries in place and time” (p. 25). Forego a human-centric view that sees domestication as an intentional and goal-oriented decision on our part. Consider instead the option we had no long-term vision, and that animals have agency too, some possibly choosing domestication, as Stephen Bonduriansky has argued. Forget the dichotomy between wild and domesticated, think rather of “a continuum […] of gradually intensifying relationships” (p. 1). The search for the “first” or “oldest” example is thus misguided; there are many other, more relevant questions to ask in zooarchaeology. And comparing current wild and domestic populations is fraught with difficulties: “no living population is any group’s ancestral population” (p. 14). Wild populations of now-domesticated forms are often extinct. In short, this chapter read like a sobering reality check and was the highlight of this book for me.

“Since many people own pets, most of us probably think we understand domestication. Appropriately, the first chapter could be characterised as “everything you thought you knew about domestication is wrong””

Chapters 3 to 7 form the core and cover genetics, evolution, development, and morphology. There is so much material here that I can only give you a subjective highlights reel. What is notable is that the author discusses both how domestic animals shed light on biology, and how biology sheds light on domestic animals. In other words, he discusses both studies that use domestic animals as model organisms and studies on the biology of domestication.

So, Thomas Hunt Morgan and Sewall Wright studied domestic animals to make pioneering contributions to genetics, while studying genetics has revealed how traits of domestic animals come about, e.g. the mutations underlying different head crests in pigeons. An interesting question is whether the same genes are involved in domestic phenotypes across species. The answer so far is no. Given different phylogenetic histories, different genes are responsible for producing similar phenotypes. In studies of evolutionary developmental biology or evo-devo^[1], domestic animals are model organisms in e.g. comparative embryology^[2], while evo-devo studies have revealed e.g. developmental biases during digit formation. In pigs, gene downregulation during early limb patterning means some digits do not form, while in horses they do, but increased cell death then sculpts the tissue around the remaining toes.

The chapter on ontogeny (the development from egg to adult) focuses on what studies using domestic animals have taught us about the developmental mechanisms resulting in different phenotypes. The next chapter on life history and growth focuses mostly on how domestication affects ontogeny, e.g. growth, fecundity, seasonality of reproduction, litter size, gestation length, sexual maturity, tooth eruption, and lifespan. The chapter on morphological diversification similarly shows how domestic animals have been favourite study subjects to explore the concept of morphospace (the “universe of potential phenotypes” [p. 172]) and how domestication has resulted in variation in e.g. coat colour, body size and proportion, brain size and anatomy, and size and shape of skulls and teeth.

“The core of this book covers genetics, evolution, development, and morphology and discusses both how domestic animals shed light on biology, and how biology sheds light on domestic animals”

These core chapters are followed by one rather interesting chapter on some odds and ends. Here, Sánchez-Villagra argues feralization is not just domestication in reverse. Feral animals never fully return to a wild state, and environments have usually changed in the meantime, frequently because of disturbance by humans. He discusses domestication experiments on chickens, rats, the famous long-term study on silver foxes, and the existence or not of the domestication syndrome. This is the idea that selection for tameness results in a suite of co-occurring phenotypic changes, a “package deal” that includes floppy ears, reduced aggression, and smaller brains. Sánchez-Villagra is more circumspect: though there are some generic changes across mammals, there are few universal domestic features: “domestication produces, as it happens in evolution, wonderful variation and a lack of universals” (p. viii). Finally, this chapter asks whether domestication accelerates rates of evolution. The studies discussed here had mixed outcomes and it seems that “human intervention per se does not necessarily accelerate evolutionary rates of organisms” (p. 217).

A synthesis of this calibre is obviously going to be a mile wide and an inch deep, but that is the whole point. The Process of Animal Domestication is a perfect entry point if you want to dig deeper into the biology of animal domestication, with 59 pages containing some 1500 literature references. What prevents this book from becoming an overwhelming infodump is its excellent structure. Each chapter is divided into many short, headed sections of 2–3 pages, with boxes used for asides.

“Domestication has depended on more than just animal traits; there is also a human cultural component to it. Not all people in history pursued it. “

A final point I appreciated is how outspoken Sánchez-Villagra is on topics of broader relevance. Domestication has depended on more than just animal traits; there is also a human cultural component to it. Not all people in history pursued it. Why? Because of “the different worldview or logic guiding the relations […] with other animals“. Understanding this cultural component will hopefully make us “realize the singular as opposed to universal nature of the Western world view” (p. 32). Our Western paradigm of prosperity through perpetual economic growth has stimulated the production of animal protein at the lowest cost, disregarding environmental and animal welfare issues. Selective breeding for (economically) optimal traits can cause suffering and pain. Changing this, the author argues, will require changes in consumer behaviour and economic imperatives, even embracing “the idea that limitations on industrial and population growth can make sustainable and healthy human life and environmental protection possible” (p. 167).

The Process of Animal Domestication is a fascinating book that comes highly recommended. Its synthesis of a large body of research makes it incredibly valuable to evolutionary and developmental biologists, geneticists, anthropologists, and (zoo)archaeologists. However, the writing is accessible enough that (under)graduate students wanting to read up on animal domestication can safely turn to this book as well.

1. ↑ A quick definition of evo-devo is useful, if only because Sánchez-Villagra gives such a clear one: if developmental biology studies “how a cell becomes a completely formed organism“, then evo-devo studies “how that process has changed over the course of evolution” (p. 91).

2. ↑ Domestic animals are often used out of practical considerations such as cost or ease of breeding in the laboratory. This unfortunately means we lack information on other workhorses in evolutionary biology such as cichlid fish or Anolis lizards.

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

The Process of Animal Domestication

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

Italian plant neurobiologist (yes, this is a thing) Stefano Mancuso previously impressed me with The Revolutionary Genius of Plants. With The Incredible Journey of Plants, he has written a captivating collection of vignettes around the subject of plant migration. We tend not to think of plants as moving creatures because they are rooted to the ground. But this, as Mancuso shows, is where we are mistaken.

The Incredible Journey of Plants, written by Stefano Mancuso, published by Other Press in March 2020 (hardback, 158 pages)

This book was originally published in Italian in 2018 as L’Incredibile Viaggio delle Piante by Editori Laterza. The English version, courtesy of translator Gregory Conti, has been released by US publisher Other Press. Right at the start, Mancuso recaps the main (and for me most memorable) point of The Revolutionary Genius of Plants: plants are so very different from us because their body plan is the inverse of ours. Animals concentrate functionality in specialised organs while plants distribute these throughout their body in a diffuse fashion. Mancuso immediately demonstrates his deft pen when to this he adds: “We will never be able to understand plants if we look at them as if they were impaired animals” (p. xiv).

To put that into the context of this book, it is incorrect to say that plants do not move—the time-lapse footage showing otherwise will be familiar to many. We need to be more precise. “What plants are unable to do is locomote, or move from place to place, at least not in the course of their lifetime” (p. xiii). If the idea of plants moving through space in slow-motion, generation by generation, sounds familiar, that is because you remember my review of the amazing The Journeys of Trees. Though Mancuso explores the same principle, there is, remarkably, almost no duplication between these two books.

“[…] it is incorrect to say that plants do not move—the time-lapse footage showing otherwise will be familiar to many. We need to be more precise.”

What follows are six chapters that look at plant migration from different angles, each chapter written as a collection of two or three vignettes that tell the story of certain plant species. Thus, we meet the pioneering plants that colonize volcanic wasteland or that, like an unstoppable tide, move in as soon as humans abandon a place, such as the Chernobyl exclusion zone. We meet the invasive species that have spread around the world. And the rare species whose seeds can survive long oceanic voyages (Darwin wasted a lot of time testing many of them). We encounter the time-travellers, the ancient beings who have outlived us many times over, or the seeds that have bridged time in dormancy, only to be revived decades, centuries, sometimes millennia later.

There are the paradoxical lonely trees and the stories of how they ended up in some of the most remote and inhospitable places on the planet. And we meet the unlikely evolutionary anachronisms: those plants who rely on a few or only one animal species to transport their seeds. They have tied their fate to their disperser, and extinction of the latter often means extinction of the former. Occasionally, such plants survive by latching on to a new seed disperser “while maintaining […] as a souvenir of these “dangerous liaisons,” some bizarre characteristics, reasonable only in light of their original partnership with now-extinct animals and today completely out of place” (p. 133).

What makes this collection of stories irresistible is how Mancuso combines science and history. I found the research explaining why the seed of the coco de mer palm is so huge just as captivating as the history of the Roman siege of the Israeli fortress–palace of Masada. Its archaeological remains have yielded seeds of date palms that could be revived 2000 years later. Mancuso’s writing is superb, whether relating the emotive story of the plants and humans that survived the atomic bomb dropped on Hiroshima, or giving you a deft two-sentence explanation of the difficulties faced by stratigraphers trying to define new geological epochs such as the Anthropocene.

“What makes this collection of stories irresistible is how Mancuso combines science and history. I found the research on the size of the coco de mer palm seeds just as captivating as the history of the siege of Masada.”

Through it all runs Mancuso’s rebellious streak. When it comes to invasive species, he echoes Chris D. Thomas’s sentiment expressed in Inheritors of the Earth. “Plants that are now perceived as part of our cultural heritage are merely well-assimilated foreigners” (p. 26), as shown by the story of Oxford ragwort, an invader from Sicily. Similarly, “the species that we consider invasive today are the natives of tomorrow” (p. 27). And when discussing evolutionary anachronisms, he admonishes our species. “In nature everything is connected. This simple law that humans don’t seem to understand has a corollary: the extinction of a species […] has unforeseeable consequences” (p. 135).

The book is accompanied by watercolour drawings by Grisha Fischer. However, these do not show the plants or plant structures described in the text, some of which, such as the voluptuously shaped coco de mer, are better pictured than described. Instead, it seems that the illustrator was given carte blanche to interpret the theme of “plant migration”. She has drawn imaginary maps composed of leaves and other plant parts that, though atmospheric, seem in no way connected to what the text is describing. At least, not as far as I could discern.

The Incredible Journey of Plants is a delightful book that is nicely paced and full of fascinating science told in a captivating manner. I found it impossible to put down, though you can easily dip in and out of this book if you are pressed for time. If plants do not normally excite you, think again. This is a little gem that you do not want to miss.

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

The Incredible Journey of Plants

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

The word biology derives from the Greek words bíos (βίος in Greek), meaning “life”, and -logía (-λογία in Greek), meaning “branch of study”, and is usually defined as “the study of life”. But what is life? Remarkably, biologists cannot agree on a definition. Everyone can name clear examples of living and non-living things. However, as so often in biology, there is no sharp demarcation between the two. There is a grey area where things are, well, somewhat alive? Lifelike? It is these borderlands between life and non-life that famous science writer and journalist Carl Zimmer explores in Life’s Edge. Instead of providing an answer, this intellectually stimulating and rewarding book will help you understand why it is such a hard question to begin with.

Life’s Edge: The Search for What It Means to Be Alive, written by Carl Zimmer, published in Europe by Picador in August 2021 (hardback, 347 pages)

Zimmer approaches this thorny question from different sides and has divided his book into four parts. Throughout, he speaks to scientists working on these matters, delving into their ideas. Zimmer starts by drawing in his audience with two subjects that matter deeply to all humans: birth and death. When does human life begin and when does it end? These seemingly simple questions have been legal and moral battlegrounds for centuries. The first has seen struggles over the right to abortion. “Life begins at conception” is a catchy phrase for anti-abortionists to rally behind, but matters are not that simple, argues Zimmer. For example, the first cell of a new human arises from the fusion of two living cells, and you can reason your way backwards through time; “You’d have to canoe up life’s river billions of years before reaching its headwaters” (p. 27). As he explained in-depth in She Has Her Mother’s Laugh, some twins merge early in development to become a human chimaera, giving rise to one person made up of two distinct populations of cells. Did two lives become one? Death is a similar battleground over the right to euthanasia. People in a coma are one inhabitant of the borderlands and the medical definition of death as brain death has its problems. Possibly, many patients retain a functional hypothalamus and one young woman went through puberty and started menstruation while on life support.

But the borderlands house many other, more bizarre examples. Zimmer speaks to the scientist who grows brain organoids—clumps of human neurons—in the lab. Before you recoil in horror, remember the Zika virus? This research immediately proved its value as a model system that gave a quick and relevant answer to how the virus attacks infant brain tissue. People who also oppose animal testing might want to reconsider their objections. Meanwhile, several invertebrate animals such as rotifers and tardigrades can be revived from lifeless states after decades, a phenomenon known as cryptobiosis. Viruses, Zimmer’s speciality, are generally considered non-living. And what of red blood cells? They contain no DNA. One fish species, the Amazon molly, is a hybrid resulting from the mating of two other molly species. Only female Amazon mollies are found. They are effectively sexual parasites, requiring the males from either parent species to reproduce.

“Everyone can name clear examples of living and non-living things. However, as so often in biology, there is no sharp demarcation between the two.”

Now, biologists do agree on some things, so Zimmer appropriately turns to the hallmarks of life next in five short chapters of 10–12 pages each. Life shows metabolism, though snakes ramp theirs up and down between meals to an extreme degree. How? They use their genes in unusual ways. In one of his trademark phrases, Zimmer writes that “Their genetic orchestra uses the same instruments as ours, but they were reading different sheet music” (p. 74). These kinds of imaginative metaphors are why I so thoroughly enjoy his books. Life gathers information, though slime moulds take this to an extreme. Their large cells explore their environment and find the shortest route to food without a brain. They are so good at it that it has given rise to its own branch of computing to solve complex problems. Life shows homeostasis, keeping its internal environment at a constant setpoint, though bats can radically alter their settings when hibernating. Life reproduces, though as e.g. maple trees show, most seeds never get a chance. Unique amongst these hallmarks, reproduction is optional. The trees that do grow into adulthood “are the product of a thin pedigree of success that has sliced through a vast field of reproductive failure” (p. 109). Finally, life evolves, which is perhaps its clearest hallmark: “Life continues to evolve today. It can no more escape evolution than water can escape being wet” (p. 113).

These hallmarks result from centuries of exploration, experimentation, and thought, so Zimmer next charts their long intellectual pedigree. This was an extraordinarily interesting part of the book, populated by many fascinating historical episodes and characters of which I can only serve up a few examples here. There was the battle between Descartes’s mechanical view of life and the vitalists who insisted on a vital essence animating life. There were the chemists chipping away at this notion experimentally, creating life’s organic molecules out of ordinary chemicals; or figuring out how yeast produced alcohol through fermentation, leading to the discovery of enzymes. There are cautionary tales such as Thomas Huxley’s Bathybius haeckelii and William Carpenter’s fossil Eozoön. These species of protoplasm, a primordial goo thought to be life’s precursor, both turned out to be chemical precipitates; nothing more than “deceptive crystallization“. Zimmer warns that “In the borderland between the living and the nonliving, conceptual mirages have a way of taking shape and gaining fame” (p. 166). And then there was Hungarian physiologist Albert Szent-Györgyi who discovered vitamin C, elucidated how muscle tissue works at a molecular level, and was a World War II spy for the allied forces. He was not convinced we would ever settle on a simple definition of life, observing that “We can find different features of life at different scales” (p. 180).

“Zimmer’s final take on the topic covers origin-of-life research and astrobiology […] these are not mere tangents, but highly relevant to the question of what life is […] and [I] was pleasantly surprised by how clued-in Zimmer is.”

Zimmer’s final take on the topic covers origin-of-life research and astrobiology. The first wrestles with the question of how non-living matter became alive, the second how we would recognize life elsewhere. Thus, these are not mere tangents, but highly relevant to the question of what life is. I have reviewed several books on these topics recently and was pleasantly surprised by how clued-in Zimmer is. Though not a complete account of origin-of-life research compared to The Genesis Quest, his potted history hits all the relevant notes. And though he primarily speaks to David Deamer, who argues lipid compartments came first, Zimmer is not beholden to this view. He also discusses the other major schools of thought that argue that RNA or metabolism came first. Similarly, when he touches on hydrothermal vents at mid-ocean ridges as a site for life’s origin, he also mentions alkaline vents and the possibility of life on moons such as Saturn’s Enceladus, discussed in Alien Oceans. Pleasingly, he adds details not mentioned in either book. This includes Deamer’s fieldwork in volcanic ponds in Kamchatka or Laurie Barge’s research on self-assembling crystal structures that might be present in Enceladus’s waters.

Zimmer first spoke to Deamer in 1995. However, he has not worked on Life’s Edge continuously since then, publishing many other books in the meantime. Reading between the lines, my impression is that Zimmer has gathered many ideas, interviews, and contacts over his decades-long career. At some point, he can just crystallize whole books out of the material he is sitting on. It makes you wonder how many other ideas for books he has tucked away in his mind. If they are all going to be such fascinating and satisfying reads as Life’s Edge, then I hope many more. This book reiterates that Zimmer is one of today’s finest science writers.

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

Life’s Edge

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

Fossils are our prime source of information about life in the past. As I delve deeper into palaeontology and earth sciences, the process of fossilisation increasingly fascinates me. How does dead biological tissue fossilise? What information is lost, what is added, and what is distorted in the process? And, ultimately, how true or filtered a picture of past life does the fossil record provide? The edited book Fossilization brings together scientists from a range of disciplines working on cutting-edge topics. The result is a well-written if somewhat eclectic collection of chapters that addressed some of my queries and also answered questions I did not even know I had.

Fossilization: Understanding the Material Nature of Ancient Plants and Animals, edited by Carole T. Gee, Victoria E. McCoy, and P. Martin Sander, published by Johns Hopkins University Press in May 2021 (hardback, 290 pages)

This book needs some context. Despite the single-word title, Fossilization is not a textbook that will introduce you to taphonomy, the process of fossilisation. (I might be overlooking something, but my impression is that there is no good recent textbook and I would need to refer readers to older books such as Life History of a Fossil or Taphonomy.) Nor does this edited collection strive to be an as-broad and as-inclusive overview as possible. No, essentially Fossilization is a showcase of the research being done at DFG Research Unit FOR 2685 at the University of Bonn in Germany. Funded by the Deutsche Forschungsgemeinschaft (the German Research Foundation), this is a consortium of nine research projects under a program titled “The Limits of the Fossil Record: Analytical and Experimental Approaches to Fossilization”.

What these projects are, however, is interdisciplinary. As two of the editors clarify in their introduction, the focus of this research unit is the small: evidence at the histological, cytological, and molecular level. This is where palaeontology starts touching on neighbouring disciplines and progress requires the know-how and input from e.g. microbiologists, organic chemists, mineralogists, geochemists, pharmacists, and petrologists. Furthermore, “fossilisation” is much more than just bones turning to stone. It is an umbrella term for several geochemical processes that vary with both tissue chemistry and the environment, encompassing processes such as silicification (of wood), pyritization (of arthropods), permineralization (of bones), and others.

“[…] there are two preservation pathways [in amber] with radically different outcomes: either decay with loss of all soft tissue so that only an arthropod-shaped void remains or, spectacularly, complete preservation.”

Next to an introductory and a concluding chapter, Fossilization contains eight chapters that break down into four chapters on palaeobotany, two on fossil animals, one on amber preservation, and one on Raman spectroscopy, all of which clock in at between 20–40 pages. Throughout, attention is paid to the many modern variations of microscopy, spectroscopy, and spectrometry that can be brought to bear on fossil material. What stood out is how readable these chapters are. I am not much of an expert in any of the above disciplines, yet found that I could follow along with most chapters just fine. And some of this material is outright fascinating.

Thus, there is a chapter on soft-tissue preservation at the microscopic level, think cells or blood vessels, in dinosaur and other tetrapod bones. Is this original material or biofilm produced by bone-degrading bacteria? I remember this discussion making news headlines a few years ago. A review of studies so far concludes that the evidence points towards the former. Another chapter looks at the fossilisation of reproduction-related tissues and structures in avian dinosaurs and birds, and what analytical methods you could use to detect them. So far we have found evidence of e.g. ovarian follicles, shell membranes, eggshell pigmentation, and medullary bone (this is incidentally the same study that Lomax referenced in Locked in Time).

Two chapters stood out in particular. Chapter 5 looks at soft-tissue preservation of arthropods trapped in amber. The authors argue that there are two preservation pathways with radically different outcomes: either decay with loss of all soft tissue so that only an arthropod-shaped void remains or, spectacularly, complete preservation. They then discuss what factors might be responsible for this dual pathway. Chapter 8 draws heavily on the work of one of the authors, Conrad C. Labandeira, and reviews fossil evidence for insect-plant interactions, looking both at traces of insect damage, but also at structural and chemical defences in plants. We know that insects and plants coevolved but these authors propose a model of four phases during the last 400 million years of arthropod herbivory expanding and, in response, plant defences developing. This is a fascinating idea that is crying out for a popular treatment, and if I had to point a university press towards an idea for a new book, this chapter is it.

“Given the book’s somewhat eclectic selection of topics and relatively high price tag, who is this for? [individuals] might wish to only consult a few chapters. I would thus argue that this book is particularly suitable for academic and institutional libraries.”

More technical chapters give an introduction to Raman spectroscopy and how it can be used in palaeontology, and the structure and chemistry of silica in mineralized wood. Fossil wood also features in a chapter on experimental silicification of wood in the laboratory with comparisons to the fossil record. This chapter mentions the interesting phenomenon of in vivo mineralization where living trees in certain environments, for example Yellowstone National Park, are already fossilising during their lifetime. Finally, there is a chapter on colour in the palaeobotanical record which gives a thorough introduction to colour in living plants and then asks whether the colours we see in fossil plants result from original material, their degradation products, or from later diagenetic processes. A colour plate section, relevant especially to the last chapter, is included.

Given the book’s somewhat eclectic selection of topics and relatively high price tag, who is this for? Depending on your interests and background, your mileage may vary and you might wish to only consult a few chapters. I would thus argue that this book is particularly suitable for academic and institutional libraries. For them, it is a worthwhile investment as edited collections of this kind are often picked up by the likes of Springer or Elsevier who publish print-on-demand books with production values not nearly half as nice as Fossilization at double the price.

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

Fossilization

Other recommended books mentioned in this review:

__________________________________________________________________