Ever since humans appeared on the scene, we have been altering life on Earth. Where once our actions could be considered part of nature’s fabric, our influence has become outsized and our options to exercise it have multiplied. Though the subtitle of Life Changing does not make it explicit, science writer Helen Pilcher focuses on our impact on the genetics and evolution of life around us. A book that stands out for its balanced tone, it managed to surprise me more than once, despite my familiarity with the topics considered.

Life Changing: How Humans Are Altering Life on Earth, written by Helen Pilcher, published by Bloomsbury Publishing in February 2020 (hardback, 391 pages)

Life Changing is told in three acts. Pilcher first examines the species we have purposefully engineered, then looks at the many animals unwittingly caught up in the advancing human juggernaut, and finally considers how we might wield our knowledge for good in conservation efforts. Examining the work of numerous scientists, she takes the reader through topics as diverse as domestication, cloning, invasive species, urban evolution, de-extinction, and rewilding. Two aspects of her writing stood out for me in particular: she gets the nuances of these technical topics right, and she is balanced, not letting personal prejudice get in the way.

First, those nuances. As a former reporter for Nature and with a PhD in cell biology, Pilcher understands the biology and knows how to communicate it. Right off the bat, she clarifies that domestication is simply another form of genetic modification. Making a distinction between this and modern, laboratory-based methods, as GMO opponents are often wont to do, is a good example of the appeal to nature fallacy. The difference is one of degree, not of kind. She similarly puts the record straight on cloning: clones are not 100% genetically identical. Although you duplicate the nuclear DNA, you will need an egg cell in which to do so. The egg donor contributes its own mitochondrial DNA, which is a small but not insignificant fraction. With time, further differences accrue due to mutations and epigenetics (processes that change the way DNA is expressed without changing the DNA sequence). “We are all far more than the sum total of our DNA” (p. 136), remarks Pilcher. The last example is de-extinction, the subject of one of her previous books. Often misrepresented as resurrecting an extinct species, in reality it means genetically modifying a closely related species to resemble its ancestor. The result is “a hybrid modern-day facsimile” that “doesn’t mark a return to bygone eras; instead it marks an entirely new phase in the evolutionary story” (p. 138).

The second strong suite of Life Changing is Pilcher’s balanced reporting. Cloning has found many uses in animal breeding, but we must not forget that it is a notoriously inefficient process with most clones dying before birth—which is one reason why she would not want to clone her dog. When discussing the genetic changes wrought by trophy hunting, she admits finding the whole business repugnant but recognises how South Africa has shown that the money ploughed back into wildlife reserves benefits wildlife overall. “Although it may seem counter-intuitive, sometimes, hunting can actually help wildlife” (p. 63). And while invasive species have a bad reputation, she also speaks at some length to ecologist Chris D. Thomas. In his book Inheritors of the Earth, he pointed out how many invasive species simply slot right into an ecosystem without disturbing the locals. New Zealand now has nearly double the number of plant species. “Despite what you might have heard, invasive species aren’t all bad” (p. 229).

“[…] de-extinction [is] often misrepresented as resurrecting an extinct species, in reality it means genetically modifying a closely related species to resemble its ancestor.”

Particularly interesting is the topic of hybridisation. There is much concern about closely related species hybridising as climate change causes home ranges to shift, with pizzlies (polar–grizzly bear hybrids) being one example. But, just as humans contain some Neanderthal DNA, studies have shown grizzly bears to contain some polar bear DNA; one example of the book surprising me with something I did not know yet. It is estimated that the two species have occasionally interbred for the last 40,000 years. So should we panic? This is perhaps where Pilcher’s logic lapses slightly. When she introduces extinction and climate change she admits that, yes, these are natural processes that have always happened, but it is the current high rate that is worrisome. That same logic is not applied to her discussion of hybridisation. On the flip side, it can also be a conservation tool. The northern white rhino is functionally extinct as only two females remain. Using frozen sperm from the last, now deceased male, researchers inseminated a female southern white rhino, creating two hybrid embryos. Are we diluting the northern white rhino genome or preserving a significant fraction of it? “In some instances, maybe it’s better to have a hybrid than it is to have nothing at all” (p. 216).

Besides nuance and balance, Life Changing has several other things going for it. As a comedy writer, Pilcher has a wicked sense of humour. Regarding artificial insemination in cattle breeding, she declares: “Romance is dead, replaced by a glorified bovine turkey baster” (p. 53). Her description of zoologist Mark Carwardine’s encounter with an amorous kakapo simply has to be read; I will just leave you with the words “demented pair of sex-mad avian earmuffs” (p. 290). Sometimes, the humour is acerbic. Industrial animal farming is a major driver of the global decline in biodiversity. If somebody were to populate a new ark to reflect this shift in abundance, she half-jokes, the roll call would go “chicken, chicken, chicken, chicken, chicken, chicken, cow” (p. 353).

Pilcher knows when not to provide too much information. Whole books have been written about e.g. the long-running fox domestication experiment in Siberia, evolution in urban settings and the textbook example of the peppered moth evolving in response to changes in air pollution, the gene-editing tool CRISPR, or the stratigraphical definition of the Anthropocene and what marker will be suitable (it might just be chicken bones). For all of these topics, she manages to provide the relevant details in just a few pages.

“[…] just as humans contain some Neanderthal DNA, studies have shown grizzly bears to contain some polar bear DNA […] It is estimated that the two species have occasionally interbred for the last 40,000 years.”

In other cases, she goes into great detail. This book could be a rather depressing read, so in the last part, she explores in-depth some examples of how our knowledge and technical skills can stem the tide of biodiversity loss. Some researchers have figured out how to make coral spawn on-demand in the lab, allowing the reintroduction of live coral to sites affected by bleaching. There is the intensively managed Kakapo Recovery Program in New Zealand, and the hands-off approach of rewilding, such as the Knepp Estate in the UK. The topic of rewilding is where I find Pilcher at her least critical and most starry-eyed. Although there are places where she hints at human population numbers multiplying our impact, she never mentions overpopulation out loud. And beyond some hints at eating less meat, she does not really address what limits we ought to impose on ourselves if we want large-scale rewilding efforts to exist side-by-side with 8 billion people. Admittedly these are huge and divisive topics without easy answers that are outside of the scope of this book, but they are barely acknowledged here.

In her introduction, Pilcher pithily states: “Life is changing. Humans are responsible“. Life Changing is a very enjoyable piece of popular science writing that shows the many ways in which this is true. I was particularly pleased that, despite my familiarity with the topic, she still had surprises in store for me.

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

Life Changing

Other recommended books mentioned in this review:

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In the wake of the COVID-19 pandemic, many publishers have seen an opportunity to reissue previously published books on viruses and pandemics. As a reader, it is always difficult to know whether you are actually getting any updated content beyond the obligatory new preface or afterword, or whether this is just a quick cash-grab. Fortunately, the third edition of Carl Zimmer’s famous virology primer A Planet of Viruses is here to prove those suspicions wrong.

A Planet of Viruses, written by Carl Zimmer, published by the University of Chicago Press in March 2021 (paperback, 144 pages)

A Planet of Viruses was first published in 2011, followed by the second edition in 2015, and now the third edition in 2021. The book is a collection of short essays, many of which were originally written for World of Viruses, a National Institutes of Health-sponsored pop-science project to communicate virology to a wider audience.

In Zimmer’s trademark crisp prose, each of the twelve essays focuses on a particular virus or class of viruses while simultaneously explaining certain virology concepts. Thus the chapter on tobacco mosaic virus discusses how viruses were discovered and led to breakthroughs in microbiology, while the essays on rhinoviruses and influenza explain how our immune system combats viruses and how rapid evolution means viruses and their hosts are locked in a perpetual arms race. But there is hope. The short history of smallpox introduces the important concepts of variolation and vaccination, and how some viruses can, in principle, be eradicated.

Although each essay is short, Zimmer has the enviable quality to highlight interesting facets in each story. The essay on HIV explains the crossing of species boundaries by infectious diseases, zoonosis, the origins of HIV, and how this virus, to quote David Quammen, has since diversified “like an infectious starburst“. A piece on the West Nile Virus shows how viruses can go global, and how insect vectors such as mosquitoes can assist. And then there are the viruses that infect bacteria, bacteriophages, that outnumber us to a mind-boggling degree. As two of the essays here show, our world is a virosphere rather than a biosphere.

“Although the placenta is one of the features that made us mammals, this is ultimately thanks to a viral stowaway.”

Other essays delve into virus evolution. Studies of ancient DNA have not only revealed that our ancestors interbred with Neanderthals, but also that we may have acquired some of their viruses, such as the cancer-causing human papillomavirus. Retroviruses, meanwhile, go far beyond taking over a host’s cellular machinery: they nestle themselves into its DNA and remain there. Our genetic material is riddled with such endogenous retroviruses, one of which produces the protein syncytin that is vital for the formation of the placenta during pregnancy. This infection has ancient roots, as the virus’s genetic code is found throughout the mammalian family tree. Although the placenta is one of the features that made us mammals, this is ultimately thanks to a viral stowaway.

Viruses even force you to ponder philosophical questions such as the definition of life. Viruses are typically considered to be non-living. Yet, the essay on giant mimiviruses and their large genomes containing thousands of genes shows that these lines are blurred. Consider this essay a taste of things to come in Zimmer’s new book Life’s Edge. And as he did in She Has Her Mother’s Laugh when discussing genetic mosaics, he can implode your sense of identity with a single sentence. When discussing retroviruses he concludes that “There is no us and them—just a gradual blending and shifting mix of DNA” (p. 71).

“It was not until I looked at the references that I realised each essay has been updated with new research published in the last six years.”

By now you might be chomping at the bit. What about COVID-19? New to this edition is the essay “The Pandemic Age”, which has replaced “Predicting the Next Plague” on Ebola from the second edition. This introduces coronaviruses more generally, briefly chronicles how the SARS and MERS outbreaks proceeded and how COVID-19 differs, and discusses some of the molecular details, such as how it enters the host cell. This essay felt a bit thin on the ground and did not provide all that much new information, especially given that Zimmer has written interesting pieces on vaccines and the virus’s structure for the New York Times. I guess book publication and news cycles will forever be out of step with each other.

Now, before you conclude that this is a somewhat disappointing update on the previous edition, let me stop you there. It was not until I looked at the references that I realised each essay has been updated with new research published in the last six years. It would have been easy to just slap in the COVID-19 essay, send it off to the printers, and call it a third edition. This is not the case, however, which reflects very well on both the author and the publisher. Furthermore, this edition features stylish woodcut-like illustrations from Ian Schoenherr that open each chapter (though, unfortunately, there are no illustrations included to explain biological concepts).

A Planet of Viruses is a captivating primer to the world of viruses that requires zero background in biology. The brevity of the essays and the small size of this book make it a suitable first introduction to this fascinating part of our world. Even for a biologist such as myself, there is much to admire in Zimmer’s writing: these essays are miniature masterclasses in science communication. If, for some reason, you have so far missed out on this book then what are you waiting for? At this price and this size, you have no excuse not to indulge.

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

A Planet of Viruses (3rd edition)

Other recommended books mentioned in this review:

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What is the price of humanity’s progress? The cover of this book, featuring a dusty landscape of tree stumps, leaves little to the imagination. In the eyes of French journalist and historian Laurent Testot it has been nothing short of cataclysmic. Originally published in French in 2017, The University of Chicago Press published the English translation at the tail-end of 2020.

Early on, Testot makes clear that environmental history as a discipline can take several forms: studying both the impact of humans on the environment, and of the environment on human affairs, as well as putting nature in a historical context. Testot does all of this in this ambitious book as he charts the exploits of Monkey—his metaphor for humanity—through seven revolutions and three million years.

Cataclysms: An Environmental History of Humanity, written by Laurent Testot, published by The University of Chicago Press in November 2020 (hardback, 452 pages)

To be frank, Testot deals with the first 2,988,000 years in the first two chapters. Understandably, as the pace of progress was initially slow, and comparatively little information is available to us from the palaeontological and archaeological records. Thus, he starts his history proper with the agricultural revolution ~12,000 years ago. Given the synthesizing nature of this book, Cataclysms will be a feast of recognition for readers that are familiar with the literature.

Some examples include the near-simultaneous rise of agriculture in several places, with geography playing an important role in which plants and animals were available to domesticate, or the fall of the Late-Bronze Age civilizations in the 12th century BCE. The myth of virgin rainforests and the long history of agriculture practised in the jungle. The microbiological onslaught that accompanied the Columbian exchange when Christopher Columbus and other explorers brought new epidemics to the Americas, or the scourge of mosquito-borne diseases that later decimated European colonialists overseas. The medieval Little Ice Age and the global crises it precipitated, or the worldwide impact of the Tambora volcanic eruption. The Great Acceleration in the 20th century and the recognition of the Anthropocene. All of these have been chronicled at length in books and other publications.

“Given the synthesizing nature of this book, Cataclysms will be a feast of recognition for readers that are familiar with the literature.”

Testot also mentions episodes that I was barely familiar with; partially, I suspect, because he can draw on the French history literature. For example the eruption of the Samalas volcano that seems to have served as a transition between the Medieval Warm Period and the Little Ice Age. Or the 15th-century mining for silver in the Andes and the immense pollution that caused. Or the environmental roots of the expression “mad as a hatter” (it involves the 17th-century beaver trade). Cataclysms sometimes seems to forget it is an environmental history book. Thus, the environment takes a backseat when he describes the Axial Age, the period between 800 and 300 BCE that saw the birth of universal religions and philosophies in both Asia and Europe that are still with us today. Similarly, the chapter charting the rise of money, empires, and trade in Europe and Asia before the Common Era only at the very end examines the environmental impact of it all.

The book’s style might divide opinions. Testot throws all his eggs in the proverbial narrative basket. The book is clearly deeply researched, but the notes section at the end encompasses a mere 16 pages. Testot must have decided that supporting every claim and fact with a footnote would have distracted from the story he tells. Although the references contain many interesting books and publications, those wishing to check up on certain claims will have to do their own research. Furthermore, the book is strikingly devoid of photos, maps, graphs, and tables, bar a single chart of the human world population through time in the appendix. As such, I felt Cataclysms did not deliver on the dustjacket’s promise of providing “the full tally” the way e.g. Vaclav Smil did in Harvesting the Biosphere. Those wanting a more data-driven overview will probably want to check out Cataclysms‘s big contender for 2020, Daniel R. Headrick’s Humans versus Nature. I had the chance to rifle through a copy, though not yet read it in full. At 604 pages with a 100-page notes section (and some illustrations), it promises to be a denser read.

“[The book] will undoubtedly charm newcomers to the field with its narrative style and ambitious scope […] but I suspect that seasoned readers will crave something more dense and data-heavy.”

Testot’s outlook for the future is bleak, though his concluding chapter wanders somewhat aimlessly. Rather than offering an overview of which planetary boundaries we have breached and how far in overshoot we are, Testot focuses on what he calls the upcoming Evolutive Revolution before turning to some likely consequences of climate change. This final revolution could either pan out as the pipe-dream of transhumanism where nano-, bio-, and information technologies converge into the singularity that would make humans immortal / obsolete as Artificial Intelligence takes over (something Testot is critical of), or we may end up as mutants in the chemical cesspit that we are making of our planet. Throw in a conclusion and an epilogue to the English edition that both reiterate main points from the book, and it starts to feel a little bit like Tolkien’s struggle to let the reader go in the last book of The Lord of the Rings.

Environmental history has become a rather crowded subject and opinions will probably be divided on whether Cataclysms stands out from the crowd sufficiently. It will undoubtedly charm newcomers to the field with its narrative style and ambitious scope—Testot knows how to spin a fine yarn and provides an entry point to many fascinating chapters in world history that readers will want to explore further. I certainly enjoyed reading it, but I suspect that seasoned readers will crave something more dense and data-heavy.

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

Cataclysms

Other recommended books mentioned in this review:

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Flies do not get a lot of love. Their culinary choices, from cow-pats to corpses, do not endear them to us. Add to that that the order Diptera also hosts mosquitoes, called our deadliest predator by some authors, and you can begin to see why. Entomologist Erica McAlister, the senior curator for Diptera at the Natural History Museum, London, is on a mission to change your mind. Chances are you never have been able to admire a fly close-up.

The Inside Out of Flies, written by Erica McAlister, published by the Natural History Museum, London, in September 2020 (hardback, 288 pages)

McAlister previously explored the different lifestyles of flies with her very successful book The Secret Life of Flies. Now she returns with The Inside Out of Flies in which she marvels at their anatomy. After an initial look at the larval stage, she takes a head-to-toes trip along their segmented bodies.

Part of this book, of course, relies on a certain freakshow factor and McAlister clearly delights in her role as curator of curiosa. Behold the Pipunculidae or big-headed flies, whose eyes are so large that they look like flying microphones. Marvel at the incredible Mydidid fly, Perissocerus arabicus, whose antler-like antennae make it look like a miniature flying reindeer. Gaze upon the amazing humped thorax of the family Hybotidae. Or witness the aptly named mantis fly of the genus Ochthera whose bulging front legs resemble those of, you guessed it, the praying mantis. And do not get me started about the chapter on genitalia—it is enough to make a grown man blush.

And it has to be said, the variation in anatomical structures is wild. Her vivid descriptions will regularly make you do a double-take: “did I really read that right?” She supports this throughout with numerous beautiful close-up photos and scanning electron microscopy pictures. Clearly, I need to reconsider getting Marshall’s book Flies, as their anatomy is both fascinating and beautiful.

“Part of this book […] relies on a certain freakshow factor and McAlister clearly delights in her role as curator of curiosa.”

Not only is her subject matter engrossing and outlandish, but McAlister is also enthusiastic and witty. She marvels at blackfly larvae that “resemble members of a rather slow-paced Hells Angels gang […] as they ride, not on a motorbike, but on a crab or a mayfly to catch food”. She had me in stitches with the kinds of personal revelations that only a biologist would think of writing down: “Never have I thought that mammals were more disappointing than when I first compared their genitalia to that of flies”. And there is a streak of eccentricity in her fascination, such as the joy of watching decomposing wildlife in her garden to see the flies it attracts.

But The Inside Out of Flies is much more than just a carnival of the bizarre. McAlister introduces plenty of serious biology here and mines the research literature for little-known but captivating nuggets. The taxonomy of flies and the use of the number and position of hairs and bristles (chaetotaxy) to tell apart species. The hidden processes that happen in pupae during metamorphosis that are now being explored with micro-CT scanning. The structure and function of the individual ommatidia that make up the compound eyes of insects. The flight mechanics in the thorax that allow flies to beat their wings at such high frequencies. Or the different hypotheses of how insect wings evolved.

There is a third strand to this book that shows that fly research is good for more than just a few giggles and for satisfying the curiosity of scientists: the applications. Many Diptera are pests of crops or carriers of diseases such as malaria. This is where taxonomy, knowing which of the approximately 160,000 currently described species you are dealing with, suddenly is vital. Or where understanding the ins and outs of their reproduction (sorry…) can offer a new pest management strategy.

“But The Inside Out of Flies is much more than just a carnival of the bizarre. […] McAlister [combines] a heartfelt sense of wonder at the small things around us with a knack for popularizing science.”

One of my favourite such spin-offs is forensic entomology and McAlister provides a delightful example. Can physical barriers such as zippers delay the arrival of maggots at a corpse? This involved fresh meat covered by zippers cut from different models of suitcases and female blow flies. It is one of those seemingly weird experiments that might have people roll their eyes and mutter something about their tax money. But forensic experts and the police, who regularly pull body parts from suitcases, are really keen to know the answer to help them more accurately determine time since death and solve crimes.

And there are plenty of other examples. Studying the role of fly antennae in flight finds its application in the design of new miniature robots. The incredibly fast reaction times of a fly’s brain could pave the way to faster supercomputers. And the details of how mosquito mouthparts break skin to draw blood are inspiring new polymer microneedles that are less painful to use and have all sorts of advantages over regular steel ones.

So how does this book compare to her first book? There are a handful of examples and anecdotes that ended up in both books, but the overlap between the two is really quite small. Out of the two, The Inside Out of Flies feels like the more “serious”—and I put that in inverted commas as there is plenty to amuse and amaze you here. McAlister is an inspired spokeswoman for dipterology and entomology more generally, combining a heartfelt sense of wonder at the small things around us with a knack for popularizing science. The Inside Out of Flies, together with its predecessor The Secret Life of Flies, are must-read books for anyone interested in insects. Jonathan Balcombe, whose book Super Fly will be published later this year, is going to have his work cut out for him to put a new spin on this topic.

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

The Inside Out of Flies

Other recommended books mentioned in this review:

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Few people would count flies as their favourite animal, but, luckily for you and me, there are exceptions. Erica McAlister, the senior curator for Diptera at the Natural History Museum, London, has been enamoured with them since childhood and in 2017 wrote the very successful The Secret Life of Flies. In preparation for reviewing her new book The Inside Out of Flies, I (finally) read the book that started it all to see what the buzz was all about.

The Secret Life of Flies, written by Erica McAlister, published by the Natural History Museum, London in April 2018 (paperback, 248 pages)

The Secret Life of Flies is one of those books you wish that more scientists would write. There must be many more entomologists and other biologists that are treasure troves of knowledge who can give you a renewed appreciation for the mundane. In this handsome and very giftable little book, McAlister takes you on a ramble through the order Diptera—the flies, midges, mosquitoes etc.—with each chapter themed around a certain fly diet and lifestyle.

Your first surprise might be to learn that flies are important pollinators. Bees are the flamboyant movie stars of the insect world who get all the attention, but it is the small Theobroma cocoa fly that exclusively pollinates the cacao trees, giving us chocolate. And, as McAlister tells us here, flies are key pollinators of, for example, mango, chilli pepper, black pepper, carrot, fennel, and onion. But just as some flies make plants grow, plenty of others feed on them. Yes, there are vegetarian flies too, but we tend to be a lot less fond of those because of the global economic impact they have on our crops.

“Your first surprise might be to learn that flies are important pollinators. Bees are the flamboyant movie stars of the insect world who get all the attention, but it is [a] small […] fly that exclusively pollinates the cacao trees, giving us chocolate.”

It is a fly-eat-fly world out there, though, and a recurrent theme in this book is that of biological pest control. Not infrequently, there are other fly species that will parasitize the pest species we are bothered by. Another unusual food source for flies are fungi. Colour me surprised, for I did not know this. Some of these are obviously the scourge of mushroom farms. But you will find flies feasting on anything from large forest mushrooms to slime moulds, and some even infiltrate termite nests to plunder their underground fungus gardens!

Of course, a large part of this book delights in its yuck-factor. The flies feeding on decaying matter (the detritivores), poo (the coprophages), dead bodies (the necrophages), blood (the sanguivores), and the brutish world of predators and parasites. McAlister recounts some amazing findings here. The adults and larvae of Mystacinobia zelandica that live in sticky guano and groom each other to stay clean (how sweet!), a behaviour barely seen in flies. Or the scuttle flies that manage to get into sealed coffins six feet under to munch on desiccated corpses.

“But there are quite a few passages that made even the biologist in me cringe […] Death by a thousand cuts? How about exsanguination by 55,000 black fly bites?”

But there are quite a few passages that made even the biologist in me cringe or cry out; the treatment of gangrene with live maggots who munch necrotic tissue (still an option today, though somehow not very popular). The scuttle flies who use blade-like ovipositors to pierce the back of ants to insert eggs. The hatched larvae then crawl into the ant’s head and slowly eat the contents while they walk around alive until their heads drop off. Death by a thousand cuts? How about exsanguination by 55,000 black fly bites? (The victim in question was a cow.) Or the bumblebee robber fly who have a hardened proboscis surrounding a long, slender tongue-like structure called the hypopharynx, which they use to hunt. By stabbing their prey. In the eye.

Despite being a little shop of horrors in place, McAlister’s goal is foremost to show you how flies, which we often ignore or just swat, are fascinating creatures in their own right. Their tiny dramas may be largely invisible to us, but they are no less intriguing for it, and no less deserving of our curiosity and attention. And in some ways, this is a little book of gratitude—we would be knee-deep in corpses and excrement if it was not for these industrious little insects.

McAlister opens the book admitting that this is not a book on the taxonomic arrangement of flies, which is forever in flux, nor on their structure or workings. Luckily, she is now making up for the latter with The Inside Out of Flies, to which I will turn next.

The Secret Life of Flies

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With the world in the throes of the COVID-19 pandemic, the questions posed by the subtitle of this book are on everyone’s mind. Associate Professor at the London School of Hygiene & Tropical Medicine Adam Kucharski here takes the reader through the inner workings of contagion. From violence and idea to financial crises and, of course, disease – some universal rules cut right across disciplines. So, is this the most topical book of the year? Well, yes and no.

The Rules of Contagion: Why Things Spread – and Why They Stop, written by Adam Kucharski, published in Europe by Profile Books in March 2020 (hardback, 341 pages)

Kucharski is uniquely positioned to write a wide-ranging book like this. Next to his current position, he is trained in mathematics and did a spot of interning with a bank when the 2008 financial collapse hit. As such, he is at ease explaining both epidemiology and investment banking.

On the disease front, Kucharski covers recent outbreaks of fairly novel diseases such as Zika (which he encountered first-hand in Fiji in 2015), AIDS, Ebola, and SARS. He does not provide the full history of these the way David Quammen did in Spillover, but nevertheless gives you the relevant points in a concise form. Similarly, there is attention for some historical cases such as the miasma theory (the idea that bad air was behind diseases) and how John Snow’s work on cholera in 1850s London disproved this.

Particularly relevant to this moment in time are the epidemiological details, the titular rules of contagion. Kucharski introduces you to the SIR model, which describes how people move through three groups during a disease outbreak (Susceptible, Infectious, Recovered), how this plays into the concept of herd immunity, and how vaccination influences this. He explains the reproduction number R, its four components, abbreviated DOTS (R = Duration × Opportunities × Transmission Probability × Susceptibility), and how this explains why measures such as washing your hands and social distancing have an effect. And then there are those mysterious superspreaders which requires Kucharski to delve into network topology (the architecture of connections in a network). Having read this book, you should come away with a far better understanding of these parameters and mechanisms.

“here is the kicker of the book: these rules [of contagion] are not unique to disease outbreaks.”

But here is the kicker of the book: these rules are not unique to disease outbreaks. Ideas from public health can and have been applied to numerous other fields. This sees Kucharski branch out widely and cover a huge number of seemingly unrelated topics. His internship with a bank has given him an insider’s view of financial contagion, allowing him to clarify pyramid schemes and financial bubbles, but also how the notion of superspreaders applied to the 2008 banking crisis.

The transmission of ideas similarly follows many patterns seen in disease outbreak, although Kucharski is careful to consider ideas other than social contagion for how information spreads. His reminder of some of the psychological biases that can hinder or encourage the spread of information is a topic that will never lose its relevance. On the other side, online contagion can be encouraged by e.g. social media companies who apply epidemiological knowledge to viral marketing and the never-ending battle for your attention. This has a darker side too, ranging from echo chambers and online manipulation to the privacy concerns of many citizens about the amount and nature of data harvested by these companies.

Of course, you cannot talk about technology without touching on computer viruses, and Kucharski is equally capable of writing engagingly about computer viruses and worms, malware, botnets, DDoS attacks, or the danger of poorly secured devices that are forming the Internet of Things (see also the forthcoming Crime Dot Come and my review of Industry of Anonymity). Or what of the little-known habit of programmers to borrow pieces of code for online applications that all need to be called on, creating a vulnerable chain of dependency? This chapter might at the outset feel like a digression. But Kucharski beautifully circles back to the topic at hand by showing the parallels between virus evolution in both living and artificial systems. It is a neat writing tactic that crops up several times.

“One particular example that made me squeal with delight was how phylogenetics […] can be applied to […] the history of folk tales.”

More eye-opening for me was the long history of applying epidemiological ideas to public health. The spread of violence, riots, even suicide, can be studied and understood in this framework. One topic that made me squeal with delight was how phylogenetics (the study of evolutionary relatedness by identifying common ancestors) can be applied to a completely different field such as the history of folk tales.

From the above, it is clear that, next to disease outbreaks, The Rules of Contagion ricochets off a huge number of topics. Not all of these will interest everyone, but the enthusiasm with which Kucharski covers them is tangible, and the universal relevance of the epidemiological rules striking. Some of his metaphors are particularly lucid. Of models, he writes that they are “just a simplification of the world, designed to help us understand what might happen in a given situation […] particularly useful for questions that we can’t answer with experiments“. While of the difficulty of applying phylogenetic analysis to a slowly evolving pathogen, such as measles, he writes it is “a bit like trying to piece together a human family tree in a country where everyone has the same surname“.

“[…] of the difficulties of understanding the spread of a pathogen that evolves only slowly […] he writes it is “a bit like trying to piece together a human family tree in a country where everyone has the same surname“.”

The timing of publication of this book was uncanny, right as the COVID-19 pandemic started ramping up around the world. This presents both a blessing and a curse. On the one hand, there is a sudden, huge interest in the topic of epidemiology, and the publisher has understandably been keen to emphasize this while marketing The Rules of Contagion. On the other hand, its publication in March 2020 meant that the writing for it will have finished when the pandemic was but Chinese whispers on the wind.

Given the urgency with which people now want accessible information, many will come to this book with a narrow focus of interest and might end up frustrated or disappointed with what they see as too many irrelevant asides. Some Amazon reviews suggest this has already been the case. Personally, I think this is both unfair and misses the point. One only has to look at Kucharski’s Twitter feed to see how involved he is with the ongoing pandemic. If he had finished writing it later, would it have been a different book? I would not be surprised if the paperback* will contain a new introduction or post-script. Or Kucharski might follow Quammen’s example. A year after Spillover was published he excerpted and adapted part of it at the start of the 2014-2016 Ebola outbreak.

Whatever Kucharski will do next, here is a writer to keep an eye on. The Rules of Contagion is an incredibly engaging piece of cross-disciplinary popular science that will hold its relevance well beyond the COVID-19 pandemic.

* Update February 2021: Having leafed through a copy of the UK paperback, I can confirm that Kucharski has chosen to update some sections of his book to reflect the events of 2020.

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

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Some books, it seems, sit on your shelf just waiting for the right moment. David Quammen’s Spillover may have been published back in 2012, but it eerily foreshadows the 2019-20 coronavirus pandemic that currently keeps the world in its grip, and provides many insights. Right now, most people are of course concerned with the direct impact on public health and their jobs. While we try to slow down the spread of this disease, the global economy is taking a nosedive as country after country goes into lockdown. Once we come out on the other side though, there will be deeper questions to be asked. Could this happen again? How do we prevent that? And what the actual fuck just happened? Let Quammen be your guide, for, as he will show, everything comes from somewhere…

Spillover: Animal Infections and the Next Human Pandemic, written by David Quammen, published by Vintage in August 2013 (paperback, 592 pages)

Quammen likes to write big, chunky books. Spillover tops out at 587 pages. But do not let this put you off, for he is a master at writing a suspenseful narrative and has chopped up the book in 115 short chapters that irresistibly flow into each other.

He kicks off with the pandemic that wasn’t. You can be excused for never having heard of Hendra. First recognized in Brisbane, Australia, in 1994, it killed a dozen horses and one man. After months of research, it was traced back to bats. This crossing of species boundaries by infectious diseases is at the heart of Spillover and is a phenomenon known as zoonosis (professionals will want to refer to Zoonoses).

Zoonosis leads on to the second important concept in this book: reservoir hosts. The reason viral diseases such as polio and smallpox no longer plague us is that they only occur in humans. With nowhere else to hide, they can be eradicated by sustained vaccination campaigns. Zoonoses, in Quammen’s words, are more like guerilla fighters. They strike unexpectedly and disappear again, sometimes for years, while living on in other organisms where they cause little harm. Tracking down these reservoir hosts requires intrepid individuals willing to leave the confines of their laboratory. Several such virus hunters have written about their adventures.

“[…] the second important concept in this book: reservoir hosts. […] Zoonoses are more like guerilla fighters. They strike unexpectedly and disappear again, sometimes for years. But where do they go?”

Quammen spares no effort and accompanies many such scientists in the field, specifically to learn more about Ebola. The bloody details of this disease have been slightly exaggerated in the (in)famous book The Hot Zone (Quammen provides a healthy corrective). But it still is a horrific disease that stalks Africa, periodically popping up in humans but also killing many gorillas. The hunt for its reservoir host continues, although bats are a likely candidate. Quammen’s vivid and personal descriptions of the fieldwork, the extraordinary working conditions, and the chance scientific breakthroughs are what make Spillover such a pleasant mix of popular science and reportage. It is worth noting that at the beginning of the 2014 Ebola outbreak, a part of Spillover was updated and republished. It was a bit premature in hindsight, as that outbreak lasted until 2016.

Of course, a large part of virological research plays out in the lab, and Quammen shows himself equally at home here. The long chapter on AIDS and HIV is a perfect example, describing the decades-long research effort that has pushed the emergence of this disease back in time, all the way to the start of the 20th century. At the same time, the family tree of HIV has exploded “like an infectious starburst”, and Quammen skillfully guides the reader down the warren of HIV-1 and HIV-2, the different groups within these, and, nested within those, the many subtypes. Oh, and of course the numerous variants of the closely related simian immunodeficiency virus, or SIV, found in apes and monkeys. He relies on interviews and close reading of publications to reconstruct the tumultuous and twisting history of scientific breakthroughs and blind alleys.

Quammen also shines when it comes to memorable metaphors and masterful distillation of technical details. All of this is helped by crisp writing, short and straightforward sentences, and the repeating of salient points. He knows the details are complicated, yet he enlightens you in a conversational tone without ever being condescending. He is equally at ease giving you a potted history of the important epidemiological parameter R₀, as he is highlighting the unique character of retroviruses such as HIV. The former is the basic reproduction number that you will have seen in the news lately.

“There is some eerie foreshadowing when Quammen asks: “Will the Next Big One come out of a rainforest or a market in southern China?” […] once we get out on the other side, there will be some uncomfortable and probing questions to be asked.”

Particularly relevant now is the distinction between DNA and RNA viruses, coronaviruses belonging to the latter. As highlighted in my review of Viruses, single-stranded RNA lacks the error-correction mechanisms of DNA and is thus much more prone to mutation and rapid evolution. Quammen throws three metaphors at you to emphasize this point before repeating it: “RNA viruses mutate profligately“.

A host of other, lesser-known diseases fills these pages: herpes-B, Nipah, Marburg, bacterial zoonoses such as Lyme disease, psittacosis, and Q-fever. Even a surprise zoonotic strain of malaria. After all, most strains of malaria are vector-borne diseases, mosquitoes being their vector. They are incredibly deadly, but they are not zoonoses.

All of these have fascinating backstories. But one point jumped out at me in particular: bats. Bats are, or are suspected to be, the reservoir hosts of many zoonoses. Why? Quammen highlights some of the unique aspects of their biology that might contribute to this: there are many species (a little-known fact is that about 20% of mammal species are bats!), they roost and hibernate at extremely high densities, and they fly. For more, see Bats and Viruses, Bats and Human Health, and the practical FAO manual Investigating the Role of Bats in Emerging Zoonoses.

“Many will have been left bewildered by the abrupt arrival of the current coronavirus pandemic. To better understand the world that has just gate-crashed ours, Spillover is (still) a magnificent piece of science reporting”

Viruses are everywhere: some speak of the virosphere rather than the biosphere, while Carl Zimmer calls ours a planet of viruses. Of the Ebola virus, Quammen writes that it “is not in your habitat. You are in its.” And the virosphere is a Pandora’s box that we have ripped wide open through our actions. A recurrent and important message in Spillover is how habitat fragmentation and destruction exposes us to a menagerie of new viruses as wild animals are forced to live and die in our midst.

Particularly fertile breeding grounds for zoonoses are the bushmeat trade and the so-called wet markets in Asia where a wide range of poached animals are traded and slaughtered. Nuwer’s Poached highlighted the exotic tastes and conspicuous consumption by wealthy diners as one of several driving forces behind the demand for wild meat. These markets were ground zero for the SARS outbreak in 2002-03, and likely too for the current coronavirus pandemic. There is some eerie foreshadowing here when Quammen asks: “Will the Next Big One come out of a rainforest or a market in southern China?” As I said at the beginning, once we get out on the other side, there will be some uncomfortable and probing questions to be asked.

COVID-19 is only the latest in a long line of zoonotic diseases, and will certainly not be the last. But rather than wanting to make you more worried, Quammen wants to make you more smart. Many will have been left bewildered by the abrupt arrival of the current coronavirus pandemic. To better understand the world that has just gate-crashed ours, Spillover is (still) a magnificent piece of science reporting that weds exceptional clarity to spell-binding storytelling.

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Ours is the latest generation to be engaged in a blood-soaked conflict that has lasted millennia. The quote “we have met the enemy, and he is us” might come to mind, but no. Rather, as E.O. Wilson once wrote: “It is the little things that run the world“. Historian Timothy C. Winegard here offers a sweeping history of major turning points in human history observed through the compound lens of the mosquito. With an estimated compound death toll of 52 billion an insect that is truly worthy of the title “destroyer of worlds”.

The Mosquito: A Human History of Our Deadliest Predator, written by Timothy C. Winegard, published in the US by Dutton Books in September 2019 (hardback, 480 pages)

Though readers might be suspicious of single-cause explanations for historical events, the general thrust of environmental history books such as these rings true: our historical narratives are particularly enamoured with pivotal wars, politics, religion, and economics, while side-lining the influence of environmental factors. As Winegard shows, though, those stories are no less fascinating.

After a short overview of the mosquito, the diseases it can harbour, and the genetic defences humans have evolved against malaria in particular, Winegard takes the birth of agriculture as the starting point of our shared history. Or, as he so poignantly puts it: “cultivation was shackled to a corpse“. Land clearance, irrigation, and the keeping of livestock all brought us a lot closer to mosquitoes and created the perfect feeding and breeding grounds for them. Out of agriculture rose city-states, commerce, and conflict, all of which encouraged the spread of disease.

The role of trade was highlighted in Mark Harrison’s book Contagion. Winegard focuses more on conflict, which is not entirely surprising given his background as an officer and his previous books on military history. In colourful prose, often steeped in military metaphors, he takes the reader on a riveting tour of duty through prominent theatres of war.

“[…] “cultivation was shackled to a corpse“. Land clearance, irrigation, and the keeping of livestock all brought us a lot closer to mosquitoes […]”

Winegard covers ancient history with Ancient Greece and the military campaigns of Alexander the Great, Ancient Rome (with a nod to Harper’s magnificent The Fate of Rome), the Crusades, and the Mongol hordes of Genghis Khan and subsequent barbaric invasions. More modern history follows with the period from the “discovery” of the Americas, the Columbian Exchange, and African slavery, all the way to the First and especially Second World War. Given my limited knowledge of these periods, I was particularly interested reading about the colonial war games between Spain, France, Britain over Caribbean colonies, and the conflicts and revolutions giving rise to the modern United States, followed by the American Civil War.

This tour of duty takes up the lion’s share of the book and is neatly divided over a series of absorbing and very readable chapters. Winegard convincingly shows how, at every turn, General Anopheles stalked the battlefields, attacking people indiscriminately. The death toll from malaria, yellow fever, dengue and other diseases is mind-numbing, virtually always overshadowing combat casualties, sometimes by an order of magnitude.

Insidiously, as Winegard shows, it did not take military commanders long to cotton on to that. The causes of these diseases may have long escaped us*, but the correlations did not. Starting very early on, a preferred battlefield strategy was to use local terrain to one’s advantage. By forcing, luring, or manoeuvring enemy troops into swampy areas, mosquitoes could take a heavy toll, after which the weakened and decimated survivors could easily be mopped up.

“The death toll from malaria, yellow fever, dengue and other diseases is mind-numbing, virtually always overshadowing combat casualties, sometimes by an order of magnitude.”

Despite Winegard’s initial assertion that historians often neglect the role of disease, this is far from the first popular book that tries to take in the fast sweep of history. Diamond’s Guns, Germs and Steel, McNeill’s Plagues and People, and Shah’s The Fever are but three examples. Indeed, Winegard’s notes are a treasure trove of references for further reading, showing the amount of work he has ploughed through in the writing of The Mosquito. The books mentioned here so far are but a sample.

What I particularly liked about Winegard’s writing was that he does not shy away from unpleasant observations and some healthy historical correctives. There is his amusing takedown of the fabricated narrative around Pocahontas: “In Disney’s vision, Pocahontas and Smith run barefoot through the utopian natural splendor of the New World, frolicking in its idyllic waterfalls. In truth, the situation in Jamestown was a cannibalistic, mosquito-ravaged mess“. Others are more serious, such as his observation that the African slave trade flourished in part because some African tribes willingly captured and sold enemy tribe members to Europeans. Some are ruthlessly pragmatic: “a sick soldier is just as useless to the war effort as a wounded soldier, and twice the burden of a dead soldier“. Others downright chilling: during the Second World War the US was scrambling to find a cure for malaria, using inmates as voluntary test subjects in experimentation that “mirrored the Nazi procedures being carried out on Jewish prisoners at Dachau“.

“Winegard’s writing […] does not shy away from unpleasant observations […] Some are ruthlessly pragmatic: “a sick soldier is just as useless to the war effort as a wounded soldier, and twice the burden of a dead soldier“.”

The final few chapters chronicle how the mosquito was finally unmasked in 1897 as the agent of disease transmission, and the temporary success story of pharmaceuticals and the insecticide DDT in combating malaria during and after the Second World War. A premature feeling of victory, indiscriminate use of these cures, and the profit-motive of pharmaceutical companies all have led to insufficient research on new cures, quickly resulting in resistant mosquitoes threatening humanity once more (a pattern that is seen more widely). Winegard briefly discusses CRISPR as the latest weapon in our arsenal and seems hopeful this could go a long way in fighting back.

If you are fond of big history books, The Mosquito is easy to recommend. Winegard has written a captivating and absorbing narrative history book that serves as a powerful reminder just how much disease has plagued us in the past and just how large a share of this is courtesy of a certain diminutive flying insect with a stinging proboscis.

*The word malaria, for example, comes from the mediaeval Italian “mala aria”, meaning “bad air”, pointing to the long-held miasma theory that blamed noxious fumes associated with marshy and swampy areas for the disease.

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

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Extremes fascinate us: the biggest, the fastest, the oldest, the tallest. Books and TV-programmes regularly scratch our itch for records, whether it is feats of engineering or biological extremes, and many sporting events revolve around humans attempting to set new records. One glance at the cover of Matthew D. LaPlante’s book Superlative and you might think that this is yet another book offering lots of gee-whiz factoids. You would also be wrong. Instead, this is an amusing and fascinating book that digs just that much deeper into the biology behind extremes, and why studying them is so worthwhile.

Superlative: The Biology of Extremes, written by Matthew D LaPlante, published by BenBella Books in May 2019 (hardback, 304 pages)

Superlative starts with an interesting observation: science often purposefully ignores statistical outliers. And yet, studying them can be revealing, showing how evolution manages to push organisms to extremes. Next to satisfying our curiosity, understanding how such extremes can exist could lead to all sorts of applications. Take size, most recently also discussed in Nature’s Giants. From books such as Scale and Why Size Matters, I already knew that most things do not scale linearly with one another. But given the vastly larger number of cells that make up an elephant, how is it they do not develop cancer more? As mammals, humans and elephants share a large amount of genetic material, but clearly the latter are doing something different. Through a close reading of both primary literature and popular articles, LaPlante explains how elephant cells activate apoptosis pathways (basically a form of cellular suicide) at the first sign of mutation.

Throughout Superlative, LaPlante employs this strategy, thus examining the world’s biggest, smallest, oldest, fastest, toughest, deadliest, smartest, and most-keen eared organisms. Bringing his background as a newspaper reporter to bear on this topic, he offers plenty of interesting tidbits with the wide-eyed wonderment of an outsider while witty footnotes provide more details on some of the interesting research that he puts in the spotlight here. There was plenty here that raised my eyebrows, though, as mentioned, the book avoids being a mere collection of factoids, rather seeking to stimulate deeper reflection.

“Even for simple metrics such as speed or age, determining who is the faster or oldest is less straightforward than you might think.”

For one, it is not always easy to determine who is the most extreme in something. When it comes to something as complex as intelligence this should come as no surprise. LaPlante discusses dolphins (admittedly a somewhat loaded topic) to then show how other animals are also very smart, including octopuses, elephants, ants, plants, and even slime moulds. Each of these is smart in their own unique way.

But even for simpler metrics such as speed or age, determining who is the most extreme is less straightforward than you might think. Sure, cheetahs are fast, but not for very long. And when you measure speed in comparison to body size, they pale in comparison to tiny mites which have been shown to sprint over 300 body lengths per second. Slow in absolute terms, but lighting-fast in relative terms. Age can be similarly slippery. A bristlecone pine nicknamed Methuselah is estimated to be 4,850 years old, but what of clones? Aspen trees exist as clonal colonies that might well be tens to hundreds of thousands of years old, taking the cake for being both the oldest and largest organisms on the planet – though certain fungal colonies might disagree (the wonderful coffee-table book The Oldest Living Things in the World illustrates many of the plants LaPlante mentions).

“Many record-holders are threatened with extinction, and many others might disappear before we had a chance to learn much about them, or to even become aware of their existence in the first place!”

The other thing is that many of the current record holders may not stay that way for long, for we often simply have not looked very hard. New discoveries can be made under our very noses, such as the world’s smallest frog (average length: a mere 7.7 mm), which was found in between leaf litter layers where nobody had thought to look. Admittedly, in some cases, we need to look outside of our normal range of perception, such as with infra- and ultrasound. But the real reason LaPlante flags this up is his concern with the biodiversity crisis. Many record-holders are threatened with extinction, and many others might disappear before we had a chance to learn much about them, or to even become aware of their existence in the first place!

The last way in which his theme of extremes serves a larger purpose is that LaPlante uses it to make a case for fundamental research. Much of the science discussed here superficially seems quirky and pointless (Do elephants experience long-term trauma? Why are waterbears so tough? How do these super fast tiny mites change direction?). But seeing scientific knowledge only through the lens of immediate (monetary) applications is a shallow perspective. In that sense, Superlative does a, well, superlative job of pointing out the value of seemingly useless research. Whether it is better understanding morphology, physiology, diseases, ageing, or evolution, we can learn an awful lot about both our own and other’s biology by being more observant of nature’s extremes. To that end, Superlative offers a very pleasant mix of mindblowing facts and a deeper context into which to place them.

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

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