Recently, a live oak next door suddenly began sporting purple blossoms. This was strange: live oaks make greenish-brown catkins and reddish-green pistils that become acorns if fertilized by the catkins. Not purple flowers. Our neighbor briefly wondered if she was hallucinating, but an investigation revealed a trickster culprit from our house: a determined passiflora vine had struck out across our deck, run down a flight of stairs, scaled the fence, then climbed up into the tree, where it stretched itself ecstatically, filling the old oak with bright new finery. It took most of an afternoon to extricate the passiflora from the tree. Now I’m more vigilant and periodically coax its insistent tendrils from around the neighboring plants, reminded of how, when my children were babies, I would peel their fingers from my glasses or a hank of my hair.

Such animal behavior on the part of plants engrossed Charles Darwin in the last months of his life, and his thoughts on the subject appear in the recently published thirtieth and final volume of his letters. Like its predecessors, this volume of The Correspondence of Charles Darwin reads like a novel in the vividness of its characters and the immediacy of their daily lives; Stephen Jay Gould, reviewing the first volume for The New York Times, compared it to Middlemarch. Darwin was a great letter writer; in volume 30 he’s no longer the young adventurer of volume 1 who sent flirtatious notes to his first love before setting off to sea, but he still produces letters full of humor and interest with his signature self-deprecating charm.

The elderly naturalist in his dark cloak gazes somberly at you from the frontispiece; he clasps his hat in his hand, a warm light bathing his pate and luxuriant white beard. The artist John Collier made this painting, now in the National Portrait Gallery in London, for the Linnean Society. “I did not intend to have scribbled all this nonsense,” Darwin wrote to Collier in February 1882, after Collier sent a copy of his new book, “but only to have thanked you for your present.” (The “nonsense” was a playful tangent in which Darwin mused about challenging a mutual friend to a duel; more on that presently.) In response to a query from the journalist Alfred Arthur Reade, who was writing a study of the use of stimulants in intellectual life, he submitted his regimen:

I drink 1 glass of wine daily and believe I should be better without any, though all Doctors urge me to drink some or more wine as I suffer much from giddiness. I have taken snuff all my life and regret that I ever acquired the habit, which I have often tried to leave off and have succeeded for a time. I feel sure that it is a great stimulus and aid in my work. I also daily smoke 2 little paper cigarettes of Turkish tobacco.

Darwin asked Reade to keep the information private, but within a few weeks of Darwin’s death, Reade published it.

Reading the volume has all the pleasure of eavesdropping. Peering over the shoulder of the solicitor and writer Anthony Rich, we glimpse proud news of Darwin’s children: George is trying for the Plumian Professorship of Astronomy and Experimental Philosophy at Cambridge; Leonard has been appointed to observe the transit of Venus on an expedition to Queensland, Australia; William has been working too hard. “But good Heavens, what a deal I have written about my sons.”

Volume 30, which covers January through April 1882 and also contains a supplement of recently discovered letters extending back to 1831, is the culmination of a monumental undertaking begun half a century ago, when an academic visionary named Frederick Burkhardt, after stepping down from the presidency of the American Council of Learned Societies, launched the Darwin Correspondence Project. James Secord, a historian of science at Cambridge, became director of the project in 2006. In addition to producing the printed volumes, whose elegant introductory essays together compose a narrative of Darwin’s life as revealed in his letters, the editors publish all the contents on the project’s website, along with a cornucopia of resources: curated selections, essays, images, biographical sketches, time lines, family trees, and maps of the voyage of the Beagle, on which the young Darwin made a fateful five-year journey around the world. If you’ve been looking for a sophisticated form of procrastination, a deep plunge into the Darwin Correspondence Project website is as good as it gets.

Early on, the editorial team decided to include letters to as well as from Darwin, doubling the magnitude of their task and multiplying its interest. Darwin’s correspondents included men and women from various social classes, religions, family backgrounds, occupations, and parts of the world. (Translations of the letters in foreign languages appear in an appendix.) He conscientiously responded to their letters and often incorporated their observations into his publications. I began with a story about my garden because Darwin’s letters and writings were filled with such anecdotes, his own and those that others sent him.


These weren’t diversions from his scientific research: they fundamentally shaped his thinking about biology, and he cited them as evidence for his theories. “Mr. D.F. Simpson, who has a small walled garden where worms abound in Bayswater,” Darwin reported in his last book, “informs me, that on a calm damp evening he there heard so extraordinary a rustling noise from under a tree from which many leaves had fallen, that he went out with a light….” But for the moment, we’ll leave Mr. Simpson here, clutching a candle wonderingly in the darkness; presently we’ll come back and see what he found, and how it made its way into Darwin’s final work.

First, the animal willfulness of plants, as exemplified by my passiflora. Darwin had an abiding project to show that plants were more like animals than people realized, in support of his theory that all forms of life had evolved from common origins. “It has often been vaguely asserted that plants are distinguished from animals by not having the power of movement,” he wrote in 1875. But this common view was mistaken: in fact, plants did move when they needed to. They just didn’t often see the need, since “food is brought to them by the air and rain.” A tendril-bearing plant, Darwin observed, displays a remarkable ability to move itself in several ways. “It first places its tendrils ready for action,” then the tendrils spontaneously revolve; when they strike an object, they can quickly curl around it and grasp it. They can also move toward or away from light, or disregard light altogether, as they see fit.

Darwin named this phenomenon—the spontaneous rotational motion of the growing parts of plants—“circumnutation,” from the Latin roots circum (“circle”) and nutare (“nod” or “sway”). In his penultimate book, The Power of Movement in Plants (1880), he explained that the radicle, or embryonic root of the plant, has a major part in this motion: it “acts like the brain” of a simple animal, directing the movements of the parts in response to the environment. In the winter and spring of 1882 Darwin was studying how plant roots responded to different substances, until his ailing cardiovascular system limited his own movements: “I find,” he wrote to a friend in early April, that “stooping over the microscope affects my heart.”

The animal agency of plants was part of a larger subject in which Darwin was keenly interested at the end of his life, a subject that soon became controversial and has remained so up to the present: the ability of individual living beings to shape the course of evolution by their own actions. After Darwin’s death his most influential interpreters, such as the German embryologist August Weismann, insisted that in true Darwinism the evolving organism is purely passive with respect to the evolutionary process. Weismann maintained that whatever characteristics an individual organism might manage to acquire during its lifetime, it could never pass these on to its offspring; they would disappear with its death. Organisms could only vary randomly from generation to generation and be acted upon by natural selection, favored or disfavored in the struggle for survival. This principle—no inheritance of acquired characteristics—became a pillar of mainstream neo-Darwinist evolutionary biology and a slogan of popular science writing.

Darwin himself, though, rejected the idea that living beings were the passive objects of evolution. In “pangenesis”—the name he gave his theory of inheritance—he hypothesized that each part of an organism threw off particles he called “gemmules.” (This was before the development of any idea of genes or DNA.) These gemmules shared a “mutual affinity” for one another that led them to gather in the reproductive organs, whence they transmitted inherited qualities to offspring. Darwin imagined that gemmules were modified by the organism’s use or disuse of the corresponding parts, so that individuals could indeed pass along the effects of their behaviors. In this regard, he followed the thinking of his main precursor in evolutionary theory, Jean-Baptiste Lamarck, who in his magnum opus, The Zoological Philosophy (1809), had proposed that living beings transformed themselves heritably by forming habits in response to their environments: in the famous example, giraffes, habitually stretching their necks to reach high branches, passed on incrementally longer necks to their descendants.

One of the botanical projects Darwin was working on in 1882 concerned the evolutionary agency of plants. A young friend, the physiologist George Romanes, had been trying to lend experimental support to Darwin’s idea that organisms transformed themselves heritably by pangenesis. Romanes had been grafting root vegetables such as potatoes, carrots, and beets to produce hybrids. Since the parts used in the graft didn’t include the reproductive organs, Romanes reasoned that the intermediate forms blending the features of the two parents, produced by means of grafting, showed that the elements responsible for shaping the next generation were spread throughout the tissues of each plant, just as Darwin’s theory of pangenesis proposed.


On New Year’s Day 1882, Darwin wrote to Romanes of news that had arrived the previous evening at Down House, Darwin’s home in the Kentish village of Downe: the French botanist Auguste François Marie Glaziou, director of parks and gardens in Rio de Janeiro, reported that he had created intermediate new varieties of sugarcane using grafts. Romanes offered to write a paper presenting the case of sugarcane in support of pangenesis, and Darwin provided a detailed outline. Their paper, “On New Varieties of the Sugar-Cane Produced by Planting in Apposition,” was read at the Linnean Society a fortnight after Darwin’s death.

Not only did living organisms transform themselves heritably, Darwin claimed, but animals also shaped the direction of evolutionary development in furtherance of their particular tastes by exerting preferences in choosing mates, a process he called “sexual selection.” The idea that animals express an aesthetic sense provided one topic of Darwin’s exchange with his portraitist friend Collier in February 1882. Collier, in his new book A Primer of Art, described the sense of beauty in Darwinian terms, as an evolutionary capacity already present in “lower animals.”

Here was the occasion on which Darwin made his joke about an imaginary duel. He mentioned to Collier that he’d been reading Thomas Henry Huxley’s new book of essays, one of which presented the opposite view from Darwin’s and Collier’s: in “On the Hypothesis That Animals Are Automata, and Its History,” Huxley argued that all organic beings, including people, were essentially automatic machines, their consciousness a mere “collateral product” of the mechanism. “If I were as well armed as Huxley,” Darwin remarked to Collier, “I would challenge him to a duel on this subject.” A month later, terminally ill and writing to thank Huxley for a note of advice and comfort, Darwin teased, “I wish to God there were more automata in the world like you.”

At the end of his life, in early 1882, Darwin was on the contentious cutting edge of the science of 2024: the inheritance of acquired characteristics and the associated phenomenon of graft hybrids have lately been subjects of renewed interest in evolutionary biology, but both became taboo in the decades after Darwin’s death, since they violated the neo-Darwinist principle that the individual organism was purely passive with regard to evolution and could vary only randomly.

It didn’t improve the reputation of these ideas in Europe and the United States when in the 1940s the Soviet agronomist Trofim Lysenko, attracted to this anathema of bourgeois capitalist science, promoted a largely fraudulent version of the idea that induced modifications could be inherited. Lysenko claimed he could change the germination season of wheat from winter to spring by subjecting the seeds to cold and moisture (he could, but this was an established practice among farmers) and that the change was inherited in the next generation (it wasn’t). He also promoted graft hybridization, using grafts to produce new varieties of plants, apparently with some success. Stalin endorsed Lysenko’s ideas, which became Soviet orthodoxy. At least one scientist who resisted Lysenkoism, Nikolai Vavilov, was arrested and died in prison.

Meanwhile, on the other side of the cold war, Lysenko became the personification of ideology-driven scientific fraud. The British evolutionary biologist and eugenicist Julian Huxley, grandson of Darwin’s automaton friend T.H. Huxley, used Lysenko to associate the idea of inheritance of acquired characteristics with Soviet Communism and the death of science. In Soviet Genetics and World Science: Lysenko and the Meaning of Heredity (1949), Huxley wrote that the idea was congenial to the Soviet dogmatic egalitarians who refused to accept the ugly but unavoidable implication of a strictly genetic theory of inheritance: that people are born unequal as a result of the random shuffling of genes. Rather than acknowledge the scientific fact of human inequality, according to Huxley, the Communists clung to “superstitions.”

The Soviet endorsement of inheritance of acquired characteristics was ideologically driven, and so was the anti-Soviet repudiation of that idea. It became difficult, though not impossible, to conduct genetics research in the Soviet Union during the 1950s; at the same time, it became correspondingly difficult in Europe and the United States to pursue research on factors other than genes that might play a part in inheritance and transmit acquired characteristics from one generation to the next.

Recently, though, the idea that acquired modifications can be passed on to offspring has been regaining some currency in mainstream biology in connection with the study of epigenetic inheritance. “Epigenetics” refers to all the factors outside the genome that influence how genes express themselves in an organism. Epigenetic factors can change over the course of an individual lifetime, and these changes are sometimes transmitted to the individual’s offspring, although the evolutionary implications of such changes remain controversial and subjects of research. The phenomenon of graft hybridization has also been making a comeback and is now generally understood as an instance of “horizontal gene transfer,” the movement of DNA from one organism to another outside the reproductive process.

Darwin was working mostly with plants in his last months, but he still believed that all kinds of organisms transmitted newly acquired characteristics to their offspring—so frequently indeed that inheritance of acquired characteristics must be “the rule, and non-inheritance the anomaly.” (In the case of noninherited changes such as amputations, he supposed sudden mutilations might not eradicate the gemmules associated with the lost part; he believed gemmules accumulated over many generations.) According to his principle of “inheritance at corresponding ages,” a characteristic would generally appear in the offspring at the same age at which the parent had developed or acquired it.

He was especially interested in testing the implications of this idea in human beings, and seized the opportunity in the summer of 1881, after Emily Fairbanks Talbot, a Bostonian social reformer and feminist, wrote to him in connection with her study of infant development. Talbot, together with her daughter Marion Talbot and the MIT chemist Ellen Swallow Richards, was in the process of founding the Association of Collegiate Alumnae (later to become the American Association of University Women), and she was also working with the American Social Science Association on a survey containing questions for parents regarding the mental and physical attainments of their children.

Darwin wrote back with lively interest in the project (in return for which the American Social Science Association made him a corresponding member in January 1882). He suggested several lines of research that bore on how his theory of pangenesis might apply to human evolution. First, does the education of the parents correlate with the mental powers of the children at any age? Darwin hypothesized that “any transmitted effect from education” would appear at “a somewhat advanced age”; this was in keeping with his idea that characteristics acquired at a given age tend to reappear in the next generation at that same age. He thought it would be good to “test statistically…the truth of the often repeated statement that coloured children at first learn as quickly as white children, but that they afterwards fall off in progress.” If true, he thought, this pattern would support the idea that “education acts not only on the individual, but by transmission on the race.” He apparently assumed the parents of Black children would necessarily have less education than those of white children, and he didn’t consider the many social factors that might differentially affect the children’s performance in school.

To the end, Darwin persisted in seeing people as unequal in moral and intellectual qualities. It wasn’t just the letters to him, but also some of the ones from him, that must have led the Darwin Correspondence Project to add a warning to its website advising visitors that they might encounter “content and language that is upsetting or offensive. This reflects the attitudes of the historical period in which they were written.” The warning includes a link to the Darwin Correspondence Project’s brief discussion of “Charles Darwin’s views on race and gender,” which identifies the ways that Darwin described people as unequal while also detailing his insistence on the fundamental unity of the human species. In addition to being a fervent abolitionist, Darwin was an early and influential advocate for women’s higher education in science and medicine and a lifelong promoter of programs of social welfare and poverty relief.

This set of attitudes may seem incoherent, but Darwin’s belief in the self-transforming capacities of all living beings, including humans, can help make sense of it. This belief led him to see what he took to be inequalities in people as shallow and impermanent. For instance, he argued that the differences among human races—as he saw them—were too superficial to be caused by natural selection and that they instead might result from sexual selection reflecting the “continued preference by the men of each race for the more attractive women, according to their standard of taste.”

In his letter to Talbot, as we’ve seen, Darwin considered that Black children might learn less well than white children from a certain age owing to differences they’d inherited from their parents. But he also thought that if this turned out to be the case, it meant that the children’s education would improve not only their own abilities but those of their children and grandchildren. He didn’t distinguish social from biological causes in these considerations; he conflated them, but not in the standard eugenic manner, which reduced social differences to biological ones. His view traveled in the opposite direction: from social causes to a changed biological situation, so that an education would heritably increase people’s ability to learn.

Darwin’s thinking, even at its most conventional and prejudiced, tended away from rather than toward an essentialist, reductive view of people: he assumed that people, like other organisms, were constantly changing and remaking themselves with lasting, evolutionary effects. In certain fundamental ways he failed to transform himself, to relinquish some of his most conventional views. Yet his belief in the ubiquitous capacity for self-transformation exerted a countervailing force on the very prejudices he retained.

A further example of this tension in Darwin’s thinking arises in his response to another American feminist social reformer, Caroline Kennard, who wrote to him from Brookline, Massachusetts, in December 1881. Kennard appealed to Darwin after hearing a presentation at the New England Women’s Club by Martha A. Hardaker, a journalist at the Boston Evening Transcript, titled the “Intellectual Inferiority of Woman from Physical Conditions.” Hardaker reasoned that since women ate less than men, and used some of what they ate to nourish the next generation, the proportion of food they devoted to thought must be correspondingly less. “It follows, therefore, that men will always think more than women.” She also warned that with absolute equality, women would have “no food whatever” to devote to reproduction, bringing about “the extinction of the human race.” Alongside these remarkable arguments, Hardaker invoked Darwin’s Descent of Man (1871), in which he wrote that sexual selection—the competition among men for women—had resulted in men having greater intellectual powers than women.

Kennard wrote to ask Darwin whether Hardaker had correctly represented his views and, if so, whether he’d changed his mind since publishing them. “Dear Madam,” Darwin replied carefully, “The question to which you refer is a very difficult one.” He explained that while he believed women to be morally superior to men, he continued to think that they were “inferior intellectually.” But not primordially so: “There is some reason to believe that aboriginally (& to the present day in the case of Savages) men & women were equal in this respect.” Women could recover their intellectual equality, Darwin thought, but only by becoming “regular ‘bread-winners,’” which would cause great harm to the education of children and the happiness of homes.

In response, Kennard politely pointed out that women were already regular breadwinners, teaching, nursing, laboring outside the house or taking in work to support their households, paying for their sons’ and brothers’ educations. Kennard had it from James Walker, a former president of Harvard, that three quarters of the young men there who weren’t independently wealthy were financially supported by women. Moreover, running a household itself required “executive ability, fixedness of purpose, and courage of execution.” Kennard apparently got the last word.

Now, remember Mr. Simpson? We left him clutching a candle in his garden on a damp night in Bayswater, entranced by a strange rustling sound. He was in fact a composer named James Frederick Simpson (Darwin apparently mistook his first initial), and what he found upon investigation was a cacophony of earthworms “collecting knots or bunches of leaves together, & drawing them, burrow-like, in the earth.” Simpson reported this discovery to Darwin having seen reviews of Darwin’s last book, The Formation of Vegetable Mould, Through the Action of Worms, with Observations on their Habits, published in the autumn of 1881.

Darwin had emphasized that the worms didn’t act by “mere blind instinctive impulse” but showed a “degree of intelligence,” varying their behavior to suit the circumstances. They positioned leaves and other objects to plug up the mouths of their burrows according to the shapes of the spaces and objects. Simpson agreed: the leaves caught up in the worms’ sonorous bustle were “curled up & screwed at the points nearest the worm. They seem to ‘select’ the leaf apex of the leaf to draw in, leaving the stem sticking out of the ground.”

Darwin included Simpson’s observations in the next printing of his book. In a subsequent letter, Simpson described the dance that accompanied the music: “The stalwart fellow who comes ‘on search’ to the surface…sweeps round the immediate locality in a wide radius which is not ungraceful in movement”—perhaps not unlike the circumnutation of tendril-forming plants.

By their minute mode of activity, Darwin showed, worms shaped the English landscape, rendering it productive and beautiful. The agricultural economy depended on their work in conjunction with other “small agencies”: moles, burrowing larvae, and insects, especially ants, that brought fine earth up to the surface. “When we behold a wide, turf-covered expanse,” he concluded,

we should remember that its smoothness, on which so much of its beauty depends, is mainly due to all the inequalities having been slowly levelled by worms. It is a marvellous reflection that the whole of the superficial mould over any such expanse has passed, and will again pass, every few years through the bodies of worms.

Darwin’s earthworm book was widely reviewed, mostly positively. Even the anonymous commentator for the conservative Quarterly Review wrote in January 1882 that while he remained unconvinced about “the Darwinian theory of Evolution,” he nevertheless had the “highest admiration” for Darwin’s research. “If the Reviewer is a young man & a worker in any branch of Biology,” Darwin wrote confidently to his publisher, John Murray, “he will assuredly sooner or later write differently about evolution. Literally I cannot name a single youngish worker who is not as deeply convinced of the truth of Evolution as I am.” The reviewer was in fact Henry Wace, a clergyman then aged forty-five, so not exactly young—maybe youngish—and not a worker in any branch of biology; he doesn’t appear to have changed his mind about evolution.

Perhaps surprisingly for a book titled The Formation of Vegetable Mould, Darwin’s treatise on earthworms inspired a lot of fan mail. “The success of this worm-book has been almost laughable,” Darwin wrote to a friend in February.

I have, however, been plagued with an endless stream of letters on the subject; most of them very foolish & enthusiastic, but some containing good fact, which I have used in correcting yesterday the “Sixth Thousandth” [print run].

One day a letter arrived from a barrister’s clerk named George Frederick Crawte, who wrote to Darwin regarding the extraordinary “muscular powers of the worm and its capacity for self defence,” submitting “a short note of a combat which took place in my garden some two years since between a worm and a frog.” The worm, Crawte reported, was six or seven inches long, and the frog about ordinary frog-size. When he first came upon them,

half the worm had disappeared down the frog’s throat. I watched them for a quarter of an hour and during that time the tussle was pretty severe. The worm on several occasions threw the frog on its back, and, though apparently unable to disengage itself, the annelid seemed to have rather the best of the fight.

Having stepped away from the battlefield for ten minutes, Crawte returned to find the combatants declaring a truce. “The frog limped away in a very ‘groggy’ condition, whilst the worm crawled off in an opposite direction.”

Darwin continued to receive bulletins from people’s gardens and daily lives describing the extraordinary exploits of small beings. His final publication compiled some of these; it was a note, “On the Dispersal of Freshwater Bivalves,” published in the April 6 issue of Nature, proposing that these mollusks transported themselves considerable distances by clinging tenaciously to the legs of ducks, beetles, frogs, and newts.

The instances Darwin cited came largely from letters he’d received, several of them from a shoe manufacturer in Northampton named Walter Drawbridge Crick (whose grandson Francis Crick, seventy years later, participated in identifying the double-helix structure of the DNA molecule). But one example came from Darwin’s son Francis, who recounted that he and a friend, while fishing in the sea off North Wales, had several times brought up mussels on their hooks and had the distinct impression these hadn’t been just torn from the bottom mechanically but had actually “seized the point of the hook.”

This story of course inspired more mail. A week before he died, Darwin received a letter from Dr. William Ogle, who had been fishing for mackerel in Cardigan Bay with a friend. They’d had a wager as to who would catch the first dozen fish. Ogle’s companion, who was one fish shy,

getting a bite, as he supposed, began to haul up as fast as he could, calling out in triumph—“I win! Here he is! Such a whopper”! when to his and my astonishment there appeared a big oyster on his hook in place of a fish. He stuck to it, that the hook was inside the shell; but I always have fancied that he was humbugging me, till I read your remarks in Nature; and now find that he may have told the simple truth after all.

The small agencies of living beings were everywhere, and even an oyster could exert itself to perform prodigious feats.

At the end of his life, Darwin was thinking about how mortal beings strive to make what they can of themselves and then pass along the results to their offspring. His pride in his children’s accomplishments was continuous with his interest in the circumnutation of tendril-forming plants, the creative industry of earthworms, and the enterprising tenacity of mollusks.

Darwin’s last surviving letter involved the actions of creatures frequently seen around the house and garden: dogs. He loved dogs and kept many over the course of his life—Nina, Spark, Pincher, Sheila, Snow, Dash, Bob, Bran, Polly—observing them as attentively as he did his cats and children. In The Expression of the Emotions in Man and Animals (1872), for instance, he described two amusingly pointless behaviors of domestic dogs: they bury surplus food but seldom dig it back up, and “after voiding their excrement often,” quite uselessly, “make with all four feet a few scratches backwards, even on a bare stone pavement, as if for the purpose of covering up their excrement with earth.”

The poet William Watson, then a young man of twenty-three, wrote to Darwin in the spring of 1882 for clarification of these observations. On April 17, two days before he died, Darwin responded explaining that he thought each habit—the food-burying one in which the dog makes “a hole…with his front legs alone, & shovels in the earth with his nose,” and the “supposed excrement-covering” gesture of the hind feet—was a remnant of a separate useful behavior that dogs had developed in the wild. It’s a perfect last letter for the Darwin correspondence: it joins science with daily life, naturalism with poetry, the patterns and passages of history with the passed-along agencies of living beings.