Sandra Herbert
CHARLES DARWIN, GEOLOGIST
485pp. Ithaca, NY: Cornell University Press. $39.95; distributed in the UK by NBN. £20.95.
0 8014 4348 2
In 1838, Charles Darwin wrote in his Notebook M, “I a geologist have illdefined [sic] notion of land covered with ocean, former animals, slow force cracking surface &c truly poetical”. When the young naturalist set forth on the Beagle late in 1831 he thought of himself not as a biologist, but as a geologist first and foremost. Our subsequent picture of him has been altogether coloured by the overwhelming impact of The Origin of Species, which was not published until 1859. But for a dozen years or so Charles Darwin was mostly concerned with geological problems, and it was a geological underpinning that led to much of what was most original in his subsequent work on evolution.
Sandra Herbert charts these early years – the era before Darwin became plagued by ill health and turned into the Sage of Down. This was a young man bursting with vigour, and not immune to poetical thoughts (years later he was to confess a little ruefully that he latterly preferred novels to the poetry of his youth). He was a naturalist let loose upon a world of uncharted wonders – flexible and fervent with enthusiasm, but already blessed with the dedicated, systematic approach to collections and observations which would so unfailingly serve him in the years to come.
Once aboard the Beagle he rigorously labelled his collections – and rocks were as important as zoological specimens or fossils. No major figure has left such a prolific paper trail: catalogues of specimens, notebooks, essays distilling his notebooks into theories, letters to friends, colleagues and family, even books with marginal notes and jottings. No wonder historians of science can cultivate new accounts by ferreting around in this rich mulch. Sandra Herbert has already mined the notebooks, and in Charles Darwin, Geologist most impressively draws from a multitude of other sources to show a great mind in the making. My initial cry of “Surely, not another Darwin book!” was soon countered by the sheer volume of scholarship and unexpected details revealing the character and extraordinary scope of interests of the young Charles.
Most biologists are aware of one of the main achievements of Darwin’s geological career – his observations of the formation of coral reefs. Darwin had appreciated that reefs form around oceanic volcanic islands. He had realized how choosy corals were about their conditions of life: they only grow in unpolluted, warm sea-water with a plentiful supply of light. He
posited that the oceanic volcanic islands had sunk slowly beneath the waves, but the corals kept on producing their hard skeletons to keep pace with the subsidence. They pulled themselves up by their own limestone bootstraps. As the top of the rocky island eventually disappeared from view, what survived was a circular atoll encompassing a blue lagoon, floored with coral sand – the encapsulation of the idyllic tropical island. This was a masterly deduction, published in 1844, but one that remained controversial for a long time. Indeed it was perhaps only finally proved in 1952, when Harry S. Ladd drilled through 1,300 metres of coral rock on Enewetak Atoll in the Marshall Islands, and “bottomed out” on a basalt island deeply sunk from view. Everything above had been made by corals, and the animals and plants associated with them on the reef. This distinguished geologist was compelled to stick up a notice by the borehole, saying: “Darwin was right!”.
What is not so widely appreciated is that Darwin was, on occasion, spectacularly wrong. Somehow this is rather consoling to us labourers on the shop floor of science: not even the greatest scientist of them all can lay claim to intellectual omniscience. In Glen Roy in Scotland the valley sides are marked with horizontal benches at several levels, so straight that they seem to have been ruled on the slopes by the hand of some Caledonian Titan. These are the “parallel roads” of Glen Roy. In all probability Darwin was influenced by his experience of rapid uplift of marine strata that he had seen in the Andes to interpret the “roads” as a succession of raised former beaches. Never slow with his pen, he put his views on the subject into print in 1839. At more or less the same time, Louis Agassiz was promulgating his glacial theory among the membership of the Geological Society – the notion that Northern Europe had been in the grip of an ice age in the comparatively recent geological past. This theory was capable of explaining by natural causes many of those “diluvial” features that had formerly been attributed to Noah’s Deluge. William Buckland of Oxford had made the case for the universal Flood in 1823, but he, too, was later to convert to the glacial theory.
Darwin had seen the effects of “rafting” of glacial boulders on icebergs in the southern oceans, especially where he saw glaciers coming down to the sea, as he did in Tierra del Fuego. He was predisposed to interpret glacial erratic blocks (those scattered features geology students invariably Spoonerize to “erotic blacks”) over the northern parts of the British Isles as the result of deposition by former icebergs. It was only to be expected that he would attribute the “parallel roads” to the action of an arm of the sea that once extended inland, leaving behind old beaches isolated by the subsequent elevation of the land. The glacial theory, on the other hand, required that a previously extensive ice-field had dammed a lake over the glen. Lake shores made the “parallel roads”, which recorded different levels of the lake as it drained away through several, progressively lower outlets. Many of the most distinguished geologists of the day took themselves off to Glen Roy to see the evidence for themselves; surveyors measured the levels of the “roads” as precisely as the technology at the time admitted. Eventually, plausible outlets for the successive levels of the former lake were identified: the glacial theory had won the day. Darwin found himself on the wrong side of a scientific argument. As the evidence built up for the glacial theory he backed off reluctantly, shoring up his opinions as he went. But when the evidence was overwhelming he admitted defeat. Perhaps it was this experience which served to push his interests more in the direction of the problem of how new species arose, although his notebooks show that he had con-sidered alternative explanations of this phenomenon from an early stage in his career.
While he was a geologist, Darwin had made a considerable impact on the science. This is reflected in his rapid promotion through the Council of the Geological Society of London to become its Secretary. Part of this advancement might have been because of his impeccable connections – he famously accompanied the Cambridge Professor Adam Sedgwick into the field, and was a friend, even confidant, of Charles Lyell. The Geological Society was also not a little snooty: it was a company of gentlemen, engaged in manly unscrambling of landscapes. Many of the Fellows of the Society would have had private incomes, as did Charles Darwin, and his connections with the Wedgwood family would have done him no harm, either. He was, in short, a member of the Establishment. His Geological Observations on South America (1846) certified him as one of the leading recorders of the geology of far-flung parts, and the Society was devoted to the acquisition of useful facts which might one day feed into a defensible theory of the Earth. There had been, in truth, rather an excess of such theories in the eighteenth century, and the gentlemanly brotherhood was enjoined to place observations first. Darwin duly obliged in this book, although he was a compulsive theorizer elsewhere. The evidence he presented of recent uplift all along the Andes has stood the test of time, and he brought to the attention of an avid public some of the prodigious “organic remains” of extinct mammals he had discovered – fossils which caused almost Spielbergian excitement in the first half of the nineteenth century. He was awarded the highest honour of the Geological Society, the Wollaston Medal, the only gong that I know of minted from the element palladium (which was discovered by William Wollaston, chemist and polymath). Nowadays, this Medal is a lifetime-achievement prize, but even in the early days of the Society it was already a mark of real distinction. If Darwin had wished, he could have become a senior figure in British geology, and lived off his Beagle experiences in the comfort of the Geological Society Dining Club for years to come. He certainly need not have courted the controversial celebrity that came with the publication of The Origin of Species. It was single-mindedness that spurred him on.
Darwin did publish scientific papers in the regular scientific journals, but from the first he set his sights on promoting his ideas and experiences through books. No doubt he hoped to make some money from these publications, but his early efforts were not lucrative. Almost all “hard” science today is conducted through the journals, with an article in Science or Nature the guarantee of attention, but with thousands of other journals as a measure of productivity for Research Assessment Exercises and the like. There is no scientist in the modern era who has made his mark in the same literate way as Darwin, with the possible exception of Stephen Jay Gould, who may consciously have based his own oeuvre on the Darwinian model. As the industry in popular-science books has grown, so has a gulf between the arcane worlds of scientific journals and the literate public. There is something rather wonderful about the idea of the intelligentsia rushing out to buy “the latest Darwin” in order to encounter new ideas.
Sandra Herbert rather glosses over the barnacle years. This was a long period, after his “I a geologist” phase, during the late 1840s and 50s when Darwin immersed himself in the study of those aberrant marine crustaceans. He not only studied living barnacles, but also prepared a fine monograph on the fossil ones – you might say he was edging towards zoology from geology by the study of the remains of organisms preserved in the rocks themselves. It seems rather plausible to me that during this period he was establishing himself as a serious zoologist – not merely a dilettante who had changed his field of interest after burning his fingers on the glacial theory, if that’s not a contradiction in terms. He needed to make his mark in a different field. To use the modern jargon, he had to have the papers on the table to prove his worth. Of course, ideas for The Origin were simmering away during this long period, and his humble objects of study taught him all kinds of useful things about sex and adaptation, and about imperfections in the fossil record. I think it is significant that he did not attempt to produce a book on the subject – this time he went through the respectable pages of the Ray Society and the Palaeontographical Society. With their imprimatur he could be taken seriously. This was important to him. Evolutionary ideas had emerged sensationally in the anonymously published Vestiges of the Natural History of Creation (1844), which could be pooh-poohed by the orthodox scientists of the day as a mishmash of half-baked ideas from the pen of a pseudo-scientist (it was subsequently revealed as the work of the antiquarian and publisher Robert Chambers). Darwin would not want to be taken lightly or dismissed as a mountebank: he was evidently a realist when it came to his career.
The same kind of judgement probably lay behind his move from geology. He was itching to concoct a theoretical explanation of major earth features. He speculated that the rise of the Andes must be balanced by a comparable depression of the Pacific basin. He clearly realized that there had to be a Theory of Everything that would explain the configuration of mountain belts and oceans, and he wanted it to be a simple theory. The trouble was that the data simply weren’t there – so little was known about the structure of the ocean floor, for example. More than a hundred years were to elapse before the unifying theory of plate tectonics actually supplied the explanatory Holy Grail that would unlock the secrets of the earth. Darwin could have wasted his life on speculations that would only founder under the evidence of twentieth-century data. But he didn’t. Instead he tackled a problem which he felt he might succeed in unravelling: the origin of species. On this sticky question his genius for generalization might gain a proper purchase: let the complexities of earth theory wait for some other scholar.
More prosaically, Darwin’s shift from geology to biology coincided with the appearance of the illness that was to dog him for the rest of his life. Geology is an occupation for the physically fit, and was even more so at a time when most of the hard slog had to be done on foot. He could no longer tackle Snowdon, let alone the Andes. Much has been written about the cause of Darwin’s malaise. There is the idea that he was an unconscious hypochondriac, secretly relieved to have an excuse not to go to council meetings in London, or attend to other social responsibilities that might shift him from the pursuit of the great work. More plausible, perhaps, is a proposal that he acquired Chagas disease in South America, the chronic symptoms of which match Darwin’s recurrent complaints quite closely. Whatever the cause, the symptoms did not affect his intellect, nor his capacity for friendship and the love of his family. Darwin remains that rarest of creatures, the genius whose necessary devotion to work did not compromise his ability to be a warm and loving father, a generous correspondent, and appreciative of the work of colleagues.
It is good to have Darwin’s achievements as a geologist accorded their proper place in his history, and Sandra Herbert has been almost geological in her cracking of the strata of his early years. I doubt whether this exhumation of Darwin’s formative years will ever be bettered. This leaves the question whether Darwin’s name would have survived on the basis of his geological work alone, had he not gone on to revolutionize biology. Surely, his perceptive solution to the problems of the formation of coral reefs around tropical islands would have perpetuated his name. But he would probably rank among a number of pioneer geologists who successfully applied the scientific method to unpicking the complexity of the Earth, men like Adam Sedgwick or James Dwight Dana. Their achievements are familiar to the cognoscenti, but they are hardly household names. Perhaps we should be grateful that Charles Darwin backed the wrong explanatory horse in the “parallel roads” of Glen Roy. Had he triumphed, he might have taken a different path in research, and the honour of demonstrating a mechanism for the origin of species passed uncontested to Alfred Russel Wallace. “Wallacian evolution” doesn’t have the same appeal, somehow.
