Metamorphosis, page 1
Copyright © 2025 by Oren Harman
Cover design by Chin-Yee Lai
Cover images © kamomeen / Shutterstock.com; © Natural History Museum, London / Bridgeman Images
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First Edition: October 2025
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Library of Congress Control Number: 2025006249
ISBNs: 9781541607606 (hardcover), 9781541607590 (ebook)
E3-20250829-JV-NF-ORI
CONTENTS
Cover
Title Page
Copyright
Dedication
Preface
PART ONE
WHERE DO WE COME FROM? 1. Surinam
2. Cicada
3. Aristotle
4. Imposters
5. The Transfiguration of Jesus to Christ
6. Ex Ovo Omnia?
7. An Ingenious Woman
8. Gentlemen
9. White Witch
10. Nabokov
11. Mayfly
PART TWO
WHERE ARE WE GOING? 1. Anna
2. Immortal Jellyfish
3. Goethe
4. Progress
5. The El Dorado of Zoology
6. Cells and Embryos
7. Deus Sive Natura
8. Axolotl
9. Riddle
10. Lucy
11. Strauss
12. Eel
PART THREE
WHAT IS THE SELF? 1. Mount Monadnock
2. Rumi
3. Sea Squirt, Starfish
4. Evo-Devo
5. Wigglesworth
6. The Molecular Trinity
7. Hopeful Monsters
8. Origin
9. Thyroxine
10. Rosetta Stone
11. Sol
Photos
Acknowledgments
Discover More
Sources
About the Author
Praise for Metamorphosis
For Sol
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PREFACE
For me it began with The Very Hungry Caterpillar. My mother would turn its thick pages ever so slowly, seducing my imagination. What will come next? It seemed like make-believe. This turning into that?? It made no sense.
Later, like many other kids, I kept a “pet” caterpillar of my own, diligently feeding it with plants and watching it grow. One morning, sure enough, it disappeared into a golden chrysalis. Holding my breath, I’d stay awake into the small hours of the night with a flashlight strapped to my forehead and a little black notebook to scribble down observations. A sparkling blue butterfly appeared one afternoon, casually perched on a leaf as if nothing special had happened. But my heart was racing. The tips of my ears went warm. And I laughed uncontrollably with the purest feelings of joy.
Forty years passed. I traveled, wrote books, fell in love, became a parent. On special nights, my mother would read The Very Hungry Caterpillar to my own two little kids. Then one morning, a good number of years after my second child’s birth, my wife emerged from the shower holding a white stick with two pink lines on it. And suddenly, night after night, the blue butterfly from my childhood aquarium came back to me in my dreams.
Whether or not you’ve had kids before, to become a parent in late middle age is special. It makes you newly aware of the so-called cycle of life. More and more, I began to feel that it was getting hard to separate my personal and professional lives. I had spent a career thinking about the ideas of Charles Darwin, and the first thing my teachers taught me was that with no foresight, or plan of action, life drifts like a speck of pollen in the wind. And yet, every life-form has a beginning, an end, and a middle. An acorn becomes an oak tree, a tiny tadpole a leaping frog. Are our human lives also a kind of unfurling, a kind of working out of a preordained path?
An amalgam of two Greek words, metamorphosis means “transformation” or “transforming.” But the biological definition of metamorphosis—radical post-embryonic development—is actually arbitrary, a matter of convention. How “radical” does change have to be to be considered “metamorphic,” and who gets to decide? We may not turn from caterpillars into butterflies, but most of us would agree that we undergo pretty dramatic post-embryonic development. Creatures are said to be either metamorphic or not, but in reality they lie on a continuum. Having evolved from an ancient progenitor of jellyfish, in our own special way, we too metamorphose.
There was little chance of our not noticing. Moons sliver, seeds sprout, empires rise and crumble. Everything in the world around us, including our bodies, is in flux. And yet as witnesses to change, we have been and remain ambivalent: We cheer the flowering bud but mourn the rotting fruit. We search for our younger selves in mirrors while praising the wisdom that comes with wrinkles. Carried by hopes and shackled by memories, we struggle to live in the moment. Perhaps this is why in so many cultures, we’ve imagined ourselves with the following metaphors: earth molded and remolded, flowing rivers, passing shadows, falling leaves. Many things change us: ideas, travels, dreams. But nothing more than the people who depart from us, and the ones we bring to life.
“How many creatures walking on this earth / Have their first being in another form?” the Roman poet Ovid asked two thousand years ago. He could not have known the full extent of the truth. That creatures transform ran counter to Aristotelian science. It was considered a heresy by many even in Darwin’s day. Yet according to current estimates, nearly three-quarters of all animal species on Earth undergo a form of metamorphosis.
Consider the spadefoot toad.
Named for the spades on its hindfeet that it uses to dig itself into the soil of the arid Sonoran Desert, this toad, which is really a frog,i is a burrowing animal, and it bleats like a goat. Every summer, after weeks of intensive feeding, it disappears underground. It will remain there, as still as a rock, protected by the earth’s moisture. It’s emergence, after ten whole months, was the inspiration for what to my mind is one of the most perfect descriptions in the English language, penned by George Orwell:
Something—some kind of shudder in the earth, or perhaps merely a rise of a few degrees in the temperature—has told him it is time to wake up.… At this period, after his long fast, the toad has a very spiritual look, like a strict Anglo-Catholic towards the end of Lent. His movements are languid but purposeful, his body is shrunken, and by contrast his eyes look abnormally large. This allows one to notice, what one might not at any other time, that a toad has about the most beautiful eye of any living creature. It is like gold, or more exactly it is like the golden-coloured semi-precious stone which one sometimes sees in signet rings, and which I think is called chrysoberyl.
It is enough to take one’s breath away. And yet the really astonishing drama of the toad’s life has already taken place. In the process of turning from a tadpole into an adult, the spadefoot toad switched from breathing underwater to breathing air on land. It exchanged aquatic for terrestrial locomotion, a diet of plants and tiny water bugs for flies, crickets, and earthworms. The toad’s skin had to adapt to life above water, and to the sun and winds and rains. Gills became lungs. It grew a new cardiovascular system, to carry hemoglobin, and a new immune system, since dangers that lurk underwater are quite different from those that prowl on land. New color patterns invaded the skin, to make terrestrial camouflage possible. The throat was recut, in sync with new chest muscles, to allow females and males to breathe above water, but also to call each other to mate. Front and back legs grew internally, then popped out spontaneously. The tail was absorbed into the body, the gut was shortened, heart arteries newly tooled, the eyes reformed into the gems that enchanted Orwell. A tiny tadpole brain was rewired and encased in a bony cranium. There was massive destruction of tissues and organs. Cell death. Regeneration. Genetic reprogramming. Anatomical remolding. And all this in a matter of weeks.
Metamorphosis is wild. And it poses a tough evolutionary question: Why in the world all this wasted energy and time? Prick a pupa with a pin and watch an oozing sludge trickle down; the entombed caterpillar has dissolved into goo in order to rebuild itself virtually from scratch. To emerge a butterfly, a brand new brain and wings and eyes and legs
As I imagined our baby developing, I knew she, too, would undergo dramatic changes. The first cleavage into two, four, eight—and by day four, sixteen cells, a microscopic speck. A neural tube forming. A tiny heartbeat appearing, bones and little fingers emerging, as if from thin air. In the coming weeks the embryo would begin to gain the features of a human, turning into a fetus and beginning to blink. Brain cells would wire like crisscrossing speed skaters at a dizzying clip. And then, when the time was right, a marvel: Having exchanged gases in the womb through my wife Yaeli’s placenta, our baby would expel the water inside her lungs, and breathe air for the very first time. Slowly, over the fourth trimester, she’d begin to focus her eyes. And one day she’d look at us and smile.
The blue butterfly appeared in my dreams for a reason. Few experiences are as life-changing as bringing a kid to the world, and fewer wonders more exhilarating than the natural magic of metamorphosis. Both mark beginnings, but are, in fact, continuations. Both, in different ways, are also forms of endings. And both make us wonder about the riddles of our world.
And so I decided to write a book about metamorphosis. Not a biological textbook, or a philosophical treatise, or even a straightforward history of science. It would be a meditation, of a father-to-be. I was curious to uncover the scientific story of metamorphosis, which I was astonished to learn had not really been told. But again and again, the human themes kept emerging. The science and philosophy and art of transformation seemed hopelessly entangled. In different ways all asked similar questions: What is an individual? Why must we struggle to change? Does the life cycle take us forward, or backward, or are we just standing in place?
Metamorphosis: A Natural and Human History attempts to address these questions. At its heart are two mysteries. First, what is metamorphosis, how does it work, and why does it exist? These are scientific questions whose solution we have been slow to discover. Already the ancients recognized the puzzle. And gradually, from mayflies flitting above lazy spring rivers to anchored sea squirts in frigid ocean depths, the life cycles of countless creatures were described over the centuries. In kissing bugs and immortal jellyfish, the last one hundred years have uncovered hormones controlling metamorphosis, and in the past decades, the genes behind them have been discovered and their pathways mapped. The experiments have been dazzling, matched only by the colorful scientists behind them—from an Englishman who decapitates insects, to a Japanese man who sings karaoke to baby jellyfish, to Sigmund Freud searching in vain for eel testicles, and all the way to the ancients, searching for the origins of life in cheese. Still, metamorphosis remains elusive. There are parts of the story that may forever remain unknown.
The second mystery of this book is about the meaning of metamorphosis for us humans, the questions we perennially ask ourselves about transformation and change. As a cultural preoccupation metamorphosis has attracted the attention of wordsmiths from Orwell to Ovid, philosophers from Plato to Parfit, and followers of every god or son of god from Jupiter to Jesus to Jagannath. In modern times it’s spawned plays like Peter Pan, inspired music by Strauss and paintings by Dalí and Kafka’s Gregor Samsa, to name but a few. Alongside being a gateway into biology, metamorphosis in a more lyrical sense is a portal into our innermost obsessions. Why we yearn to grow but are also afraid of it. What it feels like to be ourselves. How it’s possible that we remain the same while changing all the while.
We do science for practical reasons, like better medicines and weather forecasts and more efficient agriculture, and electronics. Often we do it to find “truth.” But we also engage in science to encounter metaphors that help explain life to us. And as creatures that grow, adapt, and remember, metamorphosis is a puzzle that speaks to us in a very personal way. Sometimes, when we look at ourselves closely, we disband, like a caterpillar in a chrysalis. Just as often, when we look to our past, we say: “I was a different person then.” But on most days we feel like ourselves, despite the fact that we’re constantly changing. And so it means something to us to learn that grown butterflies have memories from the time they were caterpillars. It means something that starfish can exist as two separate, different selves. What identity is will probably forever remain a secret to us. But each of us will spend a lifetime trying to figure it out.
Metamorphosis: A Natural and Human History is divided into three parts. Part 1 hearkens back to thinkers who began to unravel the mystery of reproduction and growth. The story begins with Aristotle and moves through dramatic breakthroughs in the second half of the seventeenth century, including the discovery of the very ingredients that give rise to life. Many men appear in the tale, but its central figure is the artist and naturalist Maria Sibylla Merian, sometimes referred to as the first ecologist. In a world struggling to come to terms with the place of Man—and Woman—in God’s universe, Merian’s life is a performance of the period’s emblematic question: Where do we come from?
Part 2 picks up the story in the nineteenth century and the era of Darwin. With the birth of evolutionary theory, it now became possible to interrogate life in a completely new way. No longer perfect creatures, finished by the hand of God, species were now seen to be in a state of constant flux. And as scientists unraveled their deep histories, they also began to imagine a better future. Turning evolution into a theory of everything, they applied it to sex and race and morality. One such scientist was a brash and brilliant man named Ernst Haeckel, a zoologist, marine biologist, philosopher, and artist. Trying to overcome a great tragedy, Haeckel created a new religion, and came to believe that, because he knew where we came from, he could answer the question Where are we are going?
Today we can manipulate genes to control metamorphosis, and new imaging technologies allow us to peer into a chrysalis and see how a butterfly is constructed from goo. Emboldened by these powers, many believe the views of ancient Greeks, early-modern Christians, and nineteenth-century romantics can be safely consigned to the past. But anchoring Part 3 is an extraordinary husband-and-wife couple, who are using the tools of modern biology to hearken back to an ancient belief. Lynn Riddiford and James (Jim) Truman have devoted their lives to uncovering the molecular pathways of metamorphosis, showing how genes and hormones and nerves shape bodies and behaviors. They add mesmerizing detail to our biological understanding, but also expose its limits. Can science provide answers to our most intimate questions? Riddiford and Truman provide the theme of this book in its final trimester: What is the self?
In the dramatic episodes that follow, the story goes back and forth between conventional and imaginative biography, natural creatures and intellectual history, science and philosophy and art. A spirit of loose-jointedness blows through the book to reflect the way I experienced writing it, circling around my chosen subjects and the questions they studied with the uncertainty of a fellow curious heart. I tried to sketch the debates they inherited, and to make myself live within those intellectual and spiritual confines. I circled around my protagonists again, and again, trying to get inside their heads, even adopting their language. Along the way, in a spirit of camaraderie, I recorded my own moments of wonderment.
As I awaited becoming a father for the third time, the questions posed by metamorphosis enveloped me: Where do we come from? Where are we going? What is the self? With the help of my companions, I saw how these questions were echoed in the history of science. For me this particular journey ends with Sol, our third baby. But I’d be delighted if readers felt inspired to continue the journey for themselves.
Footnote
i Generally speaking, frogs have long legs and smooth skins covered in mucus, whereas toads have shorter legs and rougher, thicker skins. Toads generally lay their eggs in long strands, whereas frogs lay theirs in a cluster, like grapes or tapioca. Most frogs have vertical pupils, whereas pupils of true toads are horizontal. But for everything just mentioned, there are also exceptions.
