Review: ‘Nursery Earth’ By Danna Staaf

Get ready to second-guess everything that has been taught in high school biology for the past three decades. Prepare to be amused, horrified, and astonished by the gory details of embryonic development in everything from squids to squirrels. Because in Nursery Earth – The Wondrous Lives of Baby Animals and the Extraordinary Ways They Shape Our World by Danna Staaf, you will find very little that is cute and fluffy, and nothing at all that is conventional. 

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Nursery Earth takes the reader on a rip-roaring journey on every imaginable aspect of the early phases of animal life. The book brings to light fascinating details of creatures both common and uncommon, from the first moments of fertilisation, through feeding and brooding, to larval development, metamorphosis and emergence. It also explores the unintended consequences of human activity – especially climate change – on baby animals, and the complicated role of conservation efforts.

Danna Staaf, a developmental biologist and science communicator, could be the person for whom the term “infectious enthusiasm” was coined: every page has some unexpected fact or insight that makes the reader want to share it with everyone in hearing range. She finds delight in the fragility, the tenacity, and the wild extremes of life’s variety.

As a graduate student, Staaf worked to uncover the fertilization and early development of the Humboldt squid. In this book, she acts as scientist, science reporter, and subject, elucidating the vast and complex range of ways that animals ensure the survival of the next generation. She refers to her own research in some areas, summarizes that of others, and includes lengthy direct passages from leading development biologists who specialize in various arcane fields. She offers charming quotes from several in this last category, such as one from ecologist Martha Weiss of Georgetown University (on parasitoid wasps): “It’s not easy being a caterpillar. Lots of people want to eat you, and lots of people want to lay their eggs inside your body.” 

The author also employs a convention throughout the text of comparing her own body, and later her pregnancy and children, to the development of the animals she studies. At several points she refers unexpectedly to her human identity in the context of whatever aspect of development that chapter is focusing on. This never fails to elicit a laugh: for example, when she was working on in-vitro fertilization of Humboldt squid, she says, “I took a couple of big steps forward on my path of understanding reproductive biology. First, I got married, and second – following a long-standing post-marital tradition – I made a lot of babies. However, they weren’t human babies, and I made them independently of my spouse.” 

This convention has the welcome effect of bringing the subject matter very close to the reader, reminding us that we are human animals, sharing fundamental aspects of our lives with all living creatures but also differing in a few important ways. Likewise, it is impossible not to imagine, fondly, growing up in the Staaf household, where Mom goes out of her way to help nesting phoebes or flies across the country just to inspect molting cicadas, and the kids bicker with each other using terms from embryo formation. 

The author structures the book along the path of an organism’s development, beginning with the egg and explaining how parents feed and incubate their young at the earliest stages. Here, we learn about concepts like protostomes, symbiotes, and brood parasites. These early chapters provide the first clues to how much biological research has accelerated over the past several decades. For example, it is now known that the composition of a father’s sperm changes depending on environmental conditions, that genes do not remain fixed throughout an organism’s life, that many species (including condors!) can reproduce parthenogenetically, and that factors such as temperature, pressure or population dynamics – rather than genes – can determine the sex of an organism like the common Wolbachia bacterium or change that of a clownfish. 

It is also where the insidious influence of climate change on early animal development can already be found. The author describes the disturbing concept of “ecological traps.” In Taiwan, for example, the warmth of concrete in built-up areas attracted native skinks to brood on it. Shortly thereafter, however, increasing temperatures made the concrete too hot, damaging the concrete-nesting populations. Furthermore, while habitat loss is in general a known conservation issue, many endangered species are at risk specifically because of the loss of habitats where their babies are spawned or reared. 

As the book proceeds through the pregnancy, larval, and juvenile stages of animal development, and eventually through metamorphosis and emergence, the paradoxes become evident. Baby animals are delicate, on one hand, but highly adapted to ensuring their own survival. Staaf describes these behaviors and phenomena in all of their extraordinary, gruesome glory: fish fathers that surround their eggs with antibacterial glue, sibling cannibalism in the womb, and physogastric mites that develop to maturity inside the mother’s body, mate with each other, and kill their mother as they emerge.

The elegance of the author’s writing, familiar but precise, makes these mind-bending facts all the more memorable. The poetry excerpts at the beginning of each chapter, along with beautiful, unnerving color photos in the middle of the book, contribute as well. Staaf is joyous in her curiosity and discovery (“Look at that humming-bird nest!”) but does not hesitate to share opinions when she has them (“Parasitic wasps horrify me, so their setbacks delight me.”). She calls octopuses “the poster child of good mommies” – they care for their young for up to four years – but does not hesitate to weigh in on serious issues, stating that “Prenatal chemical exposure is a serious issue of social justice.”

This last point becomes clear when she explains that maternal diet and environmental conditions may affect not only babies, but their genes, and therefore the next generation. For example, human women exposed to the chemical Diethylstilbestrol (DES) as embryos had daughters with endocrine disruptor risks, even though their kids were never exposed; a similar phenomenon has been found with the fungicide vinclozolin and male mouse embryos.

However, the author points out that the influence of conservation efforts on animal development is as complex as the developmental factors themselves. While she cites the conservation of the California condor as an enormous inspiration, she also points out that some efforts are seriously misguided. One core reason for this is that despite all of the advances of the past decades, each new discovery leads to more questions, and a greater understanding of how little we understand. The depth of research that necessarily underlies each page can only be imagined: for example, that of scientist Danielle Zacherl, who researches the microscopic ear bones of veliger larvae, analyzing the infinitesimally tiny layers of calcium like tree rings to understand how far the larvae have traveled since birth. The impact of climate change is mentioned almost matter-of-factly throughout the book, but each reference carries with it the implication that we are impossibly far from appreciating its broad consequences.

While Nursery Earth sometimes takes a philosophical turn (Are babies parasites? How has the answer to the nature-versus-nurture question changed over time?) and does not flinch when confronting the planetary dangers we are facing today, what comes through most of all is the celebration of discovery. More than anything, Staaf’s book is an inspiration to find out more about the world of baby animals, and to learn more about our own place in that world.

Nursery Earth: The Wondrous Lives of Baby Animals and the Extraordinary Ways They Shape Our World
Danna Staaf
2023, The Experiment, 260pp

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