The Reluctant Mr. Darwin (7 page)

Abruptly, for whatever reasons, at the age of about fifty-five, Lamarck lost his belief in the immutability of species. Soon afterward, in May 1800, he gave his first lecture with an evolutionary slant. He presented his full theory nine years later in
Philosophie zoologique
, the book from which it's mainly known. A refined version appeared still later, in the introduction to his seven-volume natural history of invertebrates. Lamarck outlived four wives, went blind, survived to the age of eighty-five under the care of an unmarried daughter, struggled financially the whole way, and died in 1829, at which point he was more admired by radical British evolutionists (such as those teaching anatomy to medical students in Edinburgh and London) than by his colleagues in France. He was buried cheaply in an unmarked grave, like Mozart.

Most people, if they know anything about Jean-Baptiste Lamarck, associate him with a single idea: the inheritance of acquired characteristics. There was more, as Darwin's groaning dismissal of what he considered Lamarckian nonsense (“tendency to progression” “adaptations from the slow willing of animals”) in the letter to Hooker reflects. Lamarck argued that two factors account for evolution. One is, as Darwin noted, an inherent tendency in living creatures to progress from simple forms toward complexity. This tendency is conferred on them, Lamarck thought, by “the supreme author of all things.” The simple forms originate by spontaneous generation. The increasing complexity comes as certain “subtle fluids” somehow open new channels through body tissue to create new and more intricate organs. Lamarck didn't explain why the progressive tendency exists, or just how those precious bodily fluids do their magic. He treated this factor as a given. It yielded separate lineages, progressing independently toward more complex species—but not to a branching tree of life. That's an important distinction to keep in mind: Lamarck never proposed that all creatures are descended from common ancestry. The right image for his theory would be prairie grass, with short stalks and long stalks rising parallel from the ground, not a bush or a tree with divergent branches, like the drawing in Darwin's “B” notebook.

Lamarck's second factor, which is more materialistic than his supposition of a God-given tendency to progress, encompasses four elements. First, animals face certain pressures from the external conditions (that is, the environment) within which they live. Second, when external conditions change, animals have new needs (
besoins
); they respond to those needs by increased use of certain organs or capacities, or by neglecting to use those they've been using. Third, increased use tends to enlarge or strengthen an organ or capacity; disuse tends to make it atrophy. Fourth, all such acquired changes are heritable. So here's the familiar idea, accurately associated with Lamarck but incompletely representing his theory: Offspring inherit the traits that their parents have acquired. The young giraffe is born with a long neck because its mother and father stretched to reach high leaves. The blacksmith's daughter is gifted with big muscles because her dad developed his over the anvil. Kiwis have useless little winglets because kiwi ancestors neglected to fly.

Two factors accounting for evolution, four elements within the second factor—and as though that's not enough, here's another ingredient of the theoretical stew: Lamarck's
sentiment intérieur
. At one point in the
Philosophie zoologique
, he posited this powerful but obscure
sentiment
(a sort of “feeling of existence,” he explained, without adding much clarity) in higher animals, supposedly driving their subtle fluids and impelling their bodies toward those uses that produce new strengths and capacities. Maybe
sentiment intérieur
was just another name for what's now called consciousness. Or maybe he meant something more. Given the wooziness of the ideas and the losses in translation, it's not surprising that Lamarck has been often misconstrued. One misconstrual was that he claimed animals have an inherent power to enlarge organs or capacities in response to their
wants
(a misreading of the French
besoins
). A giraffe wants a longer neck so it can browse on acacias—and desire plus effort makes it so. That seems to have been Darwin's impression when he ridiculed Lamarck for suggesting that adaptations derive from “the slow willing of animals.”

Darwin had gotten his first sniff of Lamarckism back in Edinburgh, as a teenager, during the period when he was discovering that natural history engaged him much more than the grisly and boring demands of medical training. He read old Erasmus's
Zoonomia
and, in an uncritical way, admired it. (He wasn't yet the tough judge of theory and supporting data that he would be later, and it was nice knowing that his own grandfather had written a notorious book.) He also read Lamarck's technical work on invertebrate classification and, more important, heard talk about Lamarckian evolutionism from a dazzling young instructor who had befriended him, Robert Grant.

Grant was crusty and formal on the outside but daringly unconventional in his thinking; a prickly and complicated man. Trained as a doctor, he taught invertebrate anatomy in Edinburgh and spent his free hours doing research on marine animals, especially sponges, or taking part in small scientific clubs such as the Plinian Society. He had a habit of making himself the mentor of select students, and in 1827 he picked Darwin. Probably the fact that this gawky youth was the grandson of Erasmus Darwin, whom Grant venerated as an evolutionary pioneer, helped settle his attentions on Charles. Together they took hikes to the seashore, waded in tide pools collecting wormy and mossy creatures, dissected them with the aid of the microscope at Grant's house, and eventually shared a strong interest in one particular organism, the “seamat” (but it was an animal, not an alga or a throw rug) known as
Flustra foliacea
.

One day while they were walking, Grant launched into a panegyric on Lamarck and his evolutionary theory, taking the younger man by surprise. At that point, after all, Charles was a dutiful middle-class kid from Shrewsbury who, despite the surname, wasn't inclined toward radical ideas, especially those imported from France. “I listened in silent astonishment,” Darwin recalled years later, “and as far as I can judge, without any effect on my mind.” He hadn't bought transmutation as peddled wholesale by his own grandfather, and he didn't buy it now as retailed in Grant's riff on Lamarck. Another reason for his resistance may have been that he'd already seen a dark, mean side of Robert Grant, when the older man pirated some of Darwin's neophyte observations on the life history of that sea-mat,
Flustra foliacea
, and incorporated them into a paper. There was no acknowledgment to Charles Darwin, as data contributor or for anything else, in the published version. On the verge of his own first real contribution to science, Darwin had learned a hard lesson about credit and competition. He never forgot.

He met Lamarckism again during the
Beagle
voyage, when the second volume of Lyell's
Principles of Geology
reached him by mail in Montevideo. He had already read the first volume, which presented Lyell's critique of old-fashioned geological thinking, with its dependence on ancient catastrophes such as Noah's Flood. Lyell made the case for a new vision (adopted and modified from James Hutton's work, forty years earlier) of geological processes that were more continuous, more gradual, more uniform. That vision, in contrast to catastrophism, would become known as uniformitarianism. Lyell's point was that geological change tends to be slowly cumulative, not catastrophic, and caused by familiar forces that operate in the present as they did in the past. This seemed brilliantly persuasive to Darwin, and his own geologizing during the voyage was informed by it.

The second volume of Lyell's
Principles
was different. Although it carried the same subtitle, announcing
An Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation
, this one looked at flux and transition among the animal and plant kingdoms. How were fossils formed? How did peat grow? What went into the formation of coral reefs? Before tackling any of these questions, Lyell addressed a more controversial one: Do species themselves change? His first two chapters were devoted to Lamarck, giving a thorough exposition of the Frenchman's theory, noting that it “has met with some degree of favour from many naturalists,” and then doggedly refuting it. No, species
don't
transmutate, Lyell decreed, not by action of Lamarck's factors nor by any others. Cats buried with Egyptian mummies look the same as our own cats, he argued. Feral cattle in America, living wild in an unfamiliar climate, eating unfamiliar foods, revert to exact likenesses of aboriginal European cattle. Yes, domestic breeding can yield novel strains of livestock, but those only constitute new varieties, never a new species. It just didn't seem compatible with Lyell's uniformitarian view—of large geological changes effected incrementally over long stretches of time—to recognize that species might change that way, too.

Darwin had read all this and agreed. Lamarck was nonsense. A dozen years later he still claimed to feel that way, with some coy stipulations: wrong answer, right question. But then how
does
transmutation occur? I think I know, he whispered to Hooker.

11

After confessing his transmutationist thinking and his murderer's sense of guilt, in that letter of January 11, 1844, Darwin waited for Hooker's response. None came. Two weeks passed. It's a safe guess that Darwin felt some nervous impatience. Had he scandalized the new pen pal? Had he kaboshed their friendship before it got going? Finally he sent another note, nudging Hooker to reply. And now Hooker did, with a long, cordial letter full of information on botanical geography and the cheerful news that he was studying Darwin's Galápagos plants. He chattered on about his pet subject, the native vegetation of remote islands, and mentioned a remarkable species of cabbage endemic to Kerguelen, in the far southern Indian Ocean. That Kerguelen cabbage, Hooker reckoned, was the weirdest cruciferous vegetable in the whole southern hemisphere. How did it get where it was? And why didn't it exist anywhere else? Pondering the cabbage, plus some other strange island creatures, led him to admit a heterodox opinion of his own: that there may have been a series of such unusual productions in isolated spots, “& also a gradual change of species.” Whoa, change of species? That was a big concession. Sounding open-minded but sensible, Hooker added, “I shall be delighted to hear how you think that this change may have taken place, as no presently conceived opinions satisfy me on the subject.” You're not crazy and you're not in danger of denouncement, not from me, he was telling Darwin, but…well, let's see what you've got.

Darwin went back to the sketchy outline he had tucked away two years before. He began writing again, articulating arguments and inserting evidence within the structure he had already arranged. This time he tried to produce something readable by others—and not just readable, persuasive. Again he started with the topic of variation among domesticated species, and how breeders select and amplify those small differences, the first leg of his cardinal analogy. Then he turned to species in the wild. He was still under the impression that wild populations vary little, except when unsettled by environmental changes. Never mind; a little was enough. Even tiny amounts of variation arising infrequently would allow natural selection, operating over great stretches of time, to produce new species of animal and plant.

Having explained his hypothetical mechanism—that is, the logic of how evolution
could
occur—he marched again through the categories of evidence showing that evolution, by some mechanism or another,
has
occurred. The pages piled up. Through late winter and spring of 1844, Darwin interrupted himself with a few minor distractions (seeing a short paper into print, commuting to London for Geological Society meetings, a family visit to Shrewsbury) but stayed focused and highly productive, as he could when his juices were hot and his health allowed. By early July he had finished a 189-page manuscript. This time he did what he hadn't done with the sketch: sent it off to a local schoolmaster to be copied in legible handwriting. The rationale for a clean copy was that it could be read by others. But by whom? Select friends like Hooker or Lyell? Typesetters at a publishing house? No…nobody, not for now. Instead he tucked it away in his office, along with a letter to his wife intended for reading “in case of my sudden death.” The letter was his informal literary will.

Here's the draft of my species theory, the letter said. If the theory is correct, and if even one competent judge of the subject is converted, “it will be a considerable step in science.” So please get this manuscript published, he told Emma, and he gave instructions on how he wanted that done. She should enlist an appropriate person to finish, improve, and edit the work. As enticement, she should offer that person £400, plus all Darwin's natural history books, plus any profits that might come from publication. She should also pass along to the editor all of Darwin's notes—his six years' accumulation of facts and quotes—written on scraps of paper and sorted by subject into eight or ten brown portfolios kept on shelves in his study. “Many of the scraps in the Portfolios contain mere rude suggestions & early views now useless,” he explained, “& many of the facts will probably turn out as having no bearing on my theory.” But he wanted his editor to sift through them. Some might be preciously relevant.

Who should this editor be? He mentioned a short list of scientific colleagues, including Charles Lyell, gentle old John Henslow in Cambridge, a brilliant paleontologist named Edward Forbes, and the congenial new acquaintance he'd been cultivating by letter, Joseph Hooker. The name of Robert Grant, Darwin's mentor from the Edinburgh days, now a hot-fire radical teaching anatomy and preaching Lamarckism in London, didn't appear. Grant was a transmutationist, as Darwin well knew, but a transmutationist who embraced the wrong theory and belonged to the wrong political camp. Darwin wanted to modernize natural history, making it law-based and materialistic in its view of causes and effects; he did
not
want to foment class warfare. If none from his list agreed to take on such an onerous job, Darwin told Emma in the testamentary letter, she should please raise the offer to £500. And if that didn't suffice, he wrote, just publish the thing as it is.