Darwin's Backyard

by James T. Costa

  DARWIN’S

  BACKYARD

  HOW SMALL EXPERIMENTS

  LED TO A BIG THEORY

  JAMES T. COSTA

  W. W. NORTON & COMPANY

  Independent Publishers Since 1923

  NEW YORK LONDON

  For Randal Keynes—

  Darwin-inspired friend and mentor

  But I love fools’ experiments. I am always making them.

  —CHARLES DARWIN

  CONTENTS

  PREFACE

  1. Origins of an Experimentiser

  Experimentising: Going to Seed

  2. Barnacles to Barbs

  Experimentising: Doing Your Barnacles

  3. Untangling the Bank

  Experimentising: A Taste for Botany

  4. Buzzing Places

  Experimentising: Bees’ Cells and Bubbles

  5. A Grand Game of Chess

  Experimentising: Getting Around

  6. The Sex Lives of Plants

  Experimentising: Darwinian Encounters of the Floral Kind

  7. It Bears on Design

  Experimentising: Orchidelirium

  8. Plants with Volition

  Experimentising: Feed Me, Seymour!

  9. Crafty and Sagacious Climbers

  Experimentising: Seek and Ye Shall Find

  10. Earthworm Serenade

  Experimentising: Get Thee to a Wormery

  ACKNOWLEDGMENTS

  NOTES

  FURTHER READING AND RESOURCES

  BIBLIOGRAPHY

  INDEX

  PREFACE

  We can only imagine that Emma Darwin had the patience of Job. At one point in the 1850s, sheets of damp paper stuccoed with frog eggs lined the hallway of her house, pigeons cooed boisterously in a dovecote in the yard, row upon row of glass jars with saltwater and floating seeds filled the cellar, and malodorous pigeon skeleton preparations permeated the air. And that was only the beginning: there was a terrarium of snails with suspended duck feet, heaps of dissected flowers, and the fenced-off plots in the lawn where the grass was carefully scraped away to study struggling seedlings. Of course, being married to Charles Darwin over a dozen years by then, she was undoubtedly used to it. Charles, she might have said to friends, was experimentising again.

  Down House, Darwin’s home of 40 years in Kent, south of London. Photograph by the author.

  Darwin’s experimentising, which appeared to some as merely the odd pursuit of an eccentric Victorian naturalist, turned out to push the envelope on his—and our—understanding of the biological world and our place within it. Darwin was laying the empirical groundwork for key elements of his revolutionary ideas on evolution.

  This book introduces a Charles Darwin that few people know. His evolutionary ideas were not pulled out of thin air. He was an observer and experimentalist, and his clever and quirky investigations were not the schemes of some solitary eccentric sequestered in a lab. No, Darwin’s home was his laboratory, and his and Emma’s large family of seven surviving children often worked with him as his able field assistants. Darwin even published with his kids, in a fashion: the very year On the Origin of Species was published, a notice on rare beetles appeared in the Entomologist’s Weekly Intelligencer by Darwin, Darwin, and Darwin—the authors being sons Franky, Lenny, and Horace, ages 10, 8, and 7, written with a wink by their proud dad on their behalf. He also had a talent for roping the butler and governess into his field studies, along with his cousins and nieces. He signed up legions of friends and strangers alike to make observations, try experiments, send him specimens, and serve as sounding boards. Yet, while Darwin may be a household name and his work equally well known, most are unfamiliar with Darwin the scientist, let alone the person.

  His landmark books are appreciated as astonishing compendia of information, yet even many Darwin enthusiasts have little sense of Darwin the inveterate observer and correspondent, ingenious synthesizer and experimentalist, or family man. The rich array of experimental projects carried out by Darwin and his family reveal a very different—very human—side of a person too often seen as a cardboard icon. Whether enthusiastically taking up one son’s suggestion to test the viability of seeds in the crops of dead birds, staking out and chasing oddly buzzing bumblebees in the garden, or venting his frustration to friends over uncooperative fish spitting out the seeds he was trying to feed them, Darwin’s experiments are often humorous and always instructive. They may have been “fools’ experiments,” as he liked to call them, but as a Darwin friend pointed out, “fools’ experiments conducted by a genius often prove to be leaps through the dark into great discoveries.”

  Through his experiments and other investigations Darwin systematically gathered data testing his evolutionary ideas. Beginning with his geological works of the 1840s, his experimentising and other pursuits provided invaluable material that bolstered his arguments. His pace picked up considerably in the 1850s, when his experiments became behind-the-scenes efforts to look into nature as no one had before, through the lens of evolution and natural selection. Darwin referred to the Origin of Species as “one long argument,” but we should step back and consider his entire post-Origin opus in precisely the same way: one longer argument. After the Origin, he published myriad papers and some 10 books: on orchids, domestication, human evolution, climbing plants, animal behavior, carnivorous plants, flower structure, and earthworms. The topics are far-ranging yet all of a piece in support of a grand vision, many involving a prodigious number of homespun experiments and other projects.

  Beyond the fun of coming to know Darwin as worm whisperer, chaser of bees, and flytrap fancier, this book too has a serious point to make. Darwin’s experiments instruct as well as entertain. Novel, amusing, at times hilarious, yes,—but they also shine a spotlight on science as a process. Darwin was a prototypical MacGyver figure: sleuth of the sandwalk—his gravelly thinking path at Down House—he shows how real insights into nature can be gained with simple tools at hand in yard, garden, or woodland. Modern visitors to Down House, ably managed by English Heritage, can see several of these experiments replicated in the meticulously restored gardens, greenhouses, and grounds.The deeper message here is that Darwin’s experiments provide object lessons and blueprints for how science works. By and large these experiments can be done here and now, in any schoolyard, backyard, classroom, or kitchen.

  A view of Darwin’s gravel thinking path, the sandwalk. Photograph by the author.

  Anyone can become an experimentiser like Darwin and learn how to look a bit more closely at the natural world. In this regard, Darwin’s experiments are an untapped resource that has been staring us in the face for a century and a half. At a time of much hand wringing over the teaching of evolution and critical thinking in science, one invaluable resource for helping communicate the essence of scientific inquiry has been all but overlooked. It is none other than the field’s founder: Darwin himself. In Darwin’s Backyard, I show how we can draw upon Darwin in exploring nature and better understanding evolution and how science works. Taking a thematic approach, this book thus has dual goals. First, I aim to take readers on a journey to see Darwin and his remarkable insights through the lens of his family life: his expansive curiosity at work and how family, friends, and a wider circle of naturalists were an integral part of this process. This very human Darwin with his homespun experiments is not the Darwin that most people are familiar with. Yet without appreciating this side of him, neither the man nor his achievements are to be fully understood. Second, I aim to show how Darwin’s method has relevance today: how his backyard experiments can be your backyard experiments. To this end I offer up a menu of Darwin-inspired experiments, using that term inclusive of Darwin’s observational projects as well as those more experimental in m
ethod.

  Where did Darwin’s penchant for experimentising come from? Though his no-nonsense father once despaired that his bug-collecting, horse-riding son would never amount to much, Charles Darwin clearly came by his philosophical turn of mind honestly—after all, his grandfather Erasmus Darwin was a famed physician and poet, with an inventive mind so fertile that the poet Samuel Taylor Coleridge coined the term “darwinizing” to describe his brand of wild speculation. Coleridge considered Erasmus to be “the most inventive of philosophical men,” and his grandson was certainly cut from the same cloth. To understand the evolution of this experimentiser, we will start with his first forays into science as a kid, in league with his beloved older brother Erasmus, his grandfather’s namesake, and their sometimes disastrous chemistry experiments. We’ll meet, too, Darwin as a college student, making sense of the natural world from Edinburgh to Cambridge, and the exhilarating experience of the Beagle voyage. Here we see a working method born, inspired by Charles Lyell’s landmark Principles of Geology. Within months of his return from his formative voyage around the world, Darwin was convinced of the reality of evolution and became the Lyell of biology. Over time his curiosity grew and his experimental eye was cast further and further afield, ferreting out the secrets of barnacles and bees, primroses and pigeons, weeds and worms. And yet in a sense he didn’t look further than the gardens, woodlands, and meadows of his beloved home, morphed into a kind of Beagle, a ship on the Downs with family and friends his dedicated crew. Marcel Proust once wrote that “the real voyage of discovery consists not in seeking new landscapes but in having new eyes.” Darwin did travel to new landscapes, but for most of his life he simply learned to see what was before him, with new eyes. In getting to know Darwin the experimentiser, we, too, can learn to discover the unfamiliar in the familiar.

  Down House and grounds, site of many of Darwin’s investigations. Drawing by Leslie C. Costa.

  Cullowhee & Highlands, North Carolina

  DARWIN’S

  BACKYARD

  1

  Origins of an Experimentiser

  When Charles Darwin was a kid of eleven or twelve his nickname was “Gas.” No, not for flatulence. His schoolmates gave him the nickname for his penchant for the noisy and smelly chemistry experiments that he and his older brother Erasmus would conduct in their makeshift “laboratory” way at the back of the garden of their handsome red-brick house. The Mount, as the home was called, was built by their physician father Robert Darwin high on a hill overlooking the River Severn in Shrewsbury, a prosperous market town in the west country of Shropshire, England. Following the fashion of the time the Darwin boys boarded at Shrewsbury School despite its proximity to home. Erasmus—dubbed “Bones,” but always ‘Ras to his siblings—left the school to continue his studies at Cambridge in 1822, and his younger brother, then 13, dutifully kept up their investigations on the home front. The “Lab,” as they called it, being a short walk from the school, it was easy for Charles Darwin to spirit a blowpipe and chemicals to his bedroom where he would “experimentise” at the gas lamp after bedtime—until, that is, the headmaster, Samuel Butler, got wind of it. Darwin never forgot the very public (and, he thought, unjust) rebuke of branding him a “poco curante”—a superficial dabbler.1

  Chemistry was all the rage at this time, and had been since the late 1700s when the likes of Joseph Priestley in Britain and Antoine Lavoisier in France made stunning discoveries on the nature of matter, Humphry Davy dazzled standing-room-only crowds with chemical demonstrations in London, and their own grandfather, Josiah Wedgwood, achieved renown across Europe for his chemical innovations in creating new forms of porcelain and glazes at his pottery, the Etruria Works.2 Beyond the spectacles that chemistry afforded, the transformations inherent in dissolving, melting, and burning substances were terribly exciting for their philosophical implications about matter and the nature of all things, living and nonliving. The Darwin brothers may have found the classical curriculum of Shrewsbury School mind-numbing (Charles later said “nothing could have been worse for the development of my mind than Dr. Butler’s school”3), but through their chemistry investigations they experienced some of the excitement and wonder of that scientific age. “The subject,” Darwin later wrote in his autobiography, “interested me greatly, and we often used to go on working till rather late at night. This was the best part of my education at school, for it showed me practically the meaning of experimental science.”4

  “Experimental science” was to Charles and Erasmus hands-on science: manipulate, dissect, mix, probe, poke, prod, heat, and carefully observe the results. Then repeat, with suitable tweaking. Experimental science in their day was broadly conceived to include demonstrations and dissections, close observations and collections, unlike today’s rather strict definition of “experiment” that involves well-framed hypotheses and careful attention to controls, replication, and sample size. Practitioners of science (natural philosophers until the English polymath William Whewell coined the term scientist in 1840) became increasingly self-conscious during the nineteenth century about the procedures and methods they deployed in figuring things out. Induction was at the heart of scientific inquiry in Darwin’s day: amassing enough facts to connect the dots and draw inferences about general principles. Deduction, the use of general principles to make predictions about facts of nature, and frame concise and testable questions to refine the principles, came on the scene largely in the twentieth century. The so-called “hypothetico-deductive” method of modern science is a misnomer, however: pure deduction never replaced earlier induction; rather, induction and deduction are used together in a fruitful iterative and mutually reinforcing process. As we will see throughout this book, Darwin’s approaches were varied, sometimes more inductive and at others more deductive by modern standards, and rarely meeting modern standards of rigorous experimental design. But for all that, Darwin managed to learn an awful lot about how the world works. To appreciate his broad-minded approach to “experiment” we must cast the net equally widely and consider the diversity of investigations he undertook over the years, in field (his yard, meadows, and woodlands) and lab (his study and greenhouse), and from methodical data-yielding experiments in the modern sense to tests, dissections, demonstrations, and comparative observations.

  In subsequent chapters, then, we’ll meet Darwin the gleaner, observer, and synthesizer in addition to Darwin the experimentiser. These were all of a piece to Darwin, because to him even observational studies were hands-on. And it all began in that smelly boyhood laboratory at the bottom of the garden.

  Edinburgh: Flustered over Flustra

  Robert Darwin saw that Shrewsbury School was becoming a waste of time (and money) for his son. In 1825 Erasmus finished up a medical course at Cambridge and was sent to the University of Edinburgh, the center of medical education in Britain, to continue his preparation for a medical career. Robert took the extraordinary step of removing 16-year-old Charles from the local school and packing him off to Edinburgh too. Clearly Charles had no aptitude for languages or the classics, so law was out of the question, and neither did he have the mathematical acumen to study physical sciences. Robert figured his sons would follow the family tradition and become doctors, so why not send Charles to medical school sooner rather than later, where he and his older brother might help each other out? It turned out to be disastrous in some respects: Charles and ’Ras got on as warmly as ever, but Charles discovered he had little stomach for the horrors of the operating theater—or the patience for certain mind-numbing lecturers. In other ways, though, it was an auspicious commencement to a deeper education: the spirit of the Scottish Enlightenment was still alive in Edinburgh, a more dynamic and forward-looking place than most in Britain at that time, its medical faculty up on the latest ideas from the continent.

  A central idea was “philosophical anatomy,” which took as its expansive subject the material basis of animal structure and function, growth and decay, health and disease. Partially an outgrow
th of “vital materialism,” it held that the properties of life were inherent in matter itself. It was married to the exciting implications of Luigi Galvani’s demonstrations back in the 1780s and ’90s of the commonality between electricity and the animating spark of life. Galvani, who was professor of surgery at the University of Bologna in Italy, had discovered “animal electricity” (called electrophysiology today) in his famous experiments with frog’s legs showing that electricity could induce muscular motion. (His 1791 treatise on the subject, De viribus electricitatis, was an important source of inspiration for Mary Shelley’s Frankenstein.) The mysteries of animal motion, long attributed to some divine animating spirit, was yielding to the empirically testable material phenomenon of electricity.

  Jean Baptiste de Lamarck was a proponent of these ideas. A sometime botanist, Lamarck was assigned to analyze and classify the ill-defined menagerie of invertebrates (a term he coined) at the Muséum d’Histoire Naturelle in postrevolutionary Paris. These animals inspired his doctrine of evolution, or “transformism.” “Nature,” he wrote in 1801, “in producing in succession every species of animal, and beginning with the least perfect or simplest to end her work with the most perfect, has gradually complicated their structure.” Lamarck saw the ubiquitous, abundant, “least perfect” of animals—invertebrates—as lowest in the scale of organization, and therefore closest to the origin of living organisms. In his thinking, microscopic organisms ceaselessly arise through spontaneous generation, and through their vital energy or life force, complicate their structure by extremely slow degrees over generations in response to their adaptive needs. Insofar as invertebrates represented an early stage in the gradual complication of structure, in Lamarck’s view, by virtue of their superabundance and diversity they also represented the best group with which to document transitions. If, as Wordsworth rhapsodized in his poem on revolutionary France, “Bliss was it in that dawn to be alive, But to be young was very heaven!”—to be an invertebrate zoologist then, too, “was very heaven,” moving the likes of Charles Darwin’s grandfather Erasmus Darwin—brilliant Enlightenment physician, inventor, political radical, and poet—to verse of his own: