The 100 Most Influential Scientists of All Time (22 page)

On the last leg of the voyage Darwin finished his 770-page diary, wrapped up 1,750 pages of notes, drew up 12 catalogs of his 5,436 skins, bones, and carcasses—and still he wondered: Was each Galapagos mockingbird a naturally produced variety? Why did ground sloths become extinct? He sailed home with problems enough to last him a lifetime.

Following the voyage, Darwin became well known through his diary's publication as
Journal of Researches into the Geology
and Natural History of the Various Countries Visited by H.M.S. Beagle
(1839). He also employed the best experts and published their descriptions of his specimens in his
Zoology of the Voyage of H.M.S. Beagle
(1838–43). Darwin drafted a 35-page sketch of his theory of natural selection in 1842 and expanded it in 1844, but he had no immediate intention of publishing it. In 1842, Darwin, increasingly shunning society, had moved his family to the isolated village of Downe, in Kent, at the “extreme edge of [the] world.” (It was in fact only 16 miles [26 km] from central London.)

From 1846 to 1854, Darwin added to his credibility as an expert on species by pursuing a detailed study of all known barnacles. Intrigued by their sexual differentiation, he discovered that some females had tiny degenerate males clinging to them. This sparked his interest in the evolution of diverging male and female forms from an original hermaphrodite creature. Four monographs on such an obscure group made him a world expert. No longer could he be dismissed as a speculator on biological matters.

In the 1850s the changing social composition of science in England—typified by the rise of the freethinking biologist Thomas Henry Huxley—promised that Darwin's work would be well-received. Huxley, the philosopher Herbert Spencer, and other outsiders were opting for a secular nature in the rationalist
Westminster Review
and deriding the influence of “parsondom” (the influence of the church). Darwin had himself lost the last shreds of his belief in Christianity with the tragic death of his oldest daughter, Annie, from typhoid in 1851.

In 1854 Darwin solved his last major problem, the forking of genera to produce new evolutionary branches. He used an industrial analogy familiar from the Wedgwood
factories, the division of labour: competition in nature's overcrowded marketplace would favour variants that could exploit different aspects of a niche. Species would diverge on the spot, like tradesmen in the same tenement.

In 1856 Darwin began writing a triple-volume book, tentatively called
Natural Selection
. Whereas in the 1830s Darwin had thought that species remained perfectly adapted until the environment changed, he now believed that every new variation was imperfect, and that perpetual struggle was the rule. He also explained the evolution of sterile worker bees in 1857. These could not be selected because they did not breed, so he opted for “family” selection (kin selection, as it is known today): the whole colony benefited from their retention.

Darwin had finished a quarter of a million words by June 18, 1858. That day he received a letter from Alfred Russel Wallace, an English socialist and specimen collector working in the Malay Archipelago, sketching a similar-looking theory. Darwin, fearing loss of priority, accepted a solution proposed by geologist Sir Charles Lyell and botanist Joseph Dalton Hooker: joint extracts from Darwin's and Wallace's works would be read at the Linnean Society on July 1, 1858. Darwin was away, sick, grieving for his tiny son who had died from scarlet fever, and thus he missed the first public presentation of the theory of natural selection.

Darwin hastily began an “abstract” of
Natural Selection
, which grew into a more accessible book,
On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life
. Suffering from a terrible bout of nausea, Darwin, now 50, was secreted away at a spa on the desolate Yorkshire moors when the book was sold to the trade on Nov. 22, 1859. He still feared the worst.

The book did distress his Cambridge patrons, but they were marginal to science now. However, radical Dissenters were sympathetic, as were the rising London biologists and geologists, even if few actually adopted Darwin's cost-benefit approach to nature. The newspapers drew the one conclusion that Darwin had specifically avoided: that humans had evolved from apes, and that Darwin was denying mankind's immortality. A sensitive Darwin, making no personal appearances, let Huxley, by now a good friend, manage this part of the debate. The pugnacious Huxley, who loved public argument as much as Darwin loathed it, had his own reasons for taking up the cause, and did so with enthusiasm. He wrote three reviews of
Origin of Species
, defended human evolution at the Oxford meeting of the British Association for the Advancement of Science in 1860 (when Bishop Samuel Wilberforce jokingly asked whether the
apes were on Huxley's grandmother's or grandfather's side), and published his own book on human evolution,
Evidence as to Man's Place in Nature
(1863). What Huxley championed was Darwin's evolutionary naturalism, his nonmiraculous assumptions, which pushed biological science into previously taboo areas and increased the power of Huxley's professionals.

Huxley's reaction, with its enthusiasm for evolution and cooler opinion of natural selection, was typical. Natural selection received little support in Darwin's day. By contrast, evolution itself (“descent,” Darwin called it—the word
evolution
would only be introduced in the last, 1872, edition of the
Origin
) was being acknowledged from British Association platforms by 1866.

In the 1860s Down House continued to serve as Darwin's laboratory, where he experimented and revamped the
Origin
through six editions. Although quietly believing in natural selection, he answered critics by reemphasizing other causes of change—for example, the effects of continued use of an organ—and he bolstered the Lamarckian belief that such alterations through excessive use might be passed on. In
Variation of Animals and Plants under Domestication
(1868) he marshaled the facts and explored the causes of variation in domestic breeds.

In 1867 the engineer Fleeming Jenkin argued that any single favourable variation would be swamped and lost by back-breeding within the general population. No mechanism was known for inheritance, and so in the
Variation
Darwin devised his hypothesis of “pangenesis” to explain the discrete inheritance of traits. He imagined that each tissue of an organism threw out tiny “gemmules,” which passed to the sex organs and permitted copies of
themselves to be made in the next generation. But Darwin's cousin Francis Galton failed to find these gemmules in rabbit blood, and the theory was dismissed.

Darwin was adept at flanking movements in order to get around his critics. He would take seemingly intractable subjects—like orchid flowers—and make them test cases for “natural selection.” Hence the book that appeared after the
Origin
was, to everyone's surprise,
The Various Contrivances by which British and Foreign Orchids are Fertilised by Insects
(1862). He showed that the orchid's beauty was not a piece of floral whimsy “designed” by God to please humans but honed by selection to attract insect cross-pollinators. The petals guided the bees to the nectaries, and pollen sacs were deposited exactly where they could be removed by a stigma of another flower.

But why the importance of cross-pollination? Darwin's botanical work was always subtly related to his evolutionary mechanism. He believed that cross-pollinated plants would produce fitter offspring than self-pollinators, and he used considerable ingenuity in conducting thousands of crossings to prove the point. The results appeared in
The Effects of Cross and Self Fertilization in the Vegetable Kingdom
(1876). His next book,
The Different Forms of Flowers on Plants of the Same Species
(1877), was again the result of long-standing work into the way evolution in some species favoured different male and female forms of flowers to facilitate outbreeding.

Through the 1860s natural selection was already being applied to the growth of society. The trend to explain the evolution of human races, morality, and civilization was capped by Darwin in his two-volume
The Descent of Man, and Selection in Relation to Sex
(1871). The book was
authoritative, annotated, and heavily anecdotal in places. The two volumes were discrete, the first discussing civilization and human origins among the Old World monkeys. (Darwin's depiction of a hairy human ancestor with pointed ears led to a spate of caricatures.) The second volume responded to critics who doubted that the iridescent hummingbird's plumage had any function—or any Darwinian explanation. Darwin argued that female birds were choosing mates for their gaudy plumage. Darwin as usual tapped his huge correspondence network of breeders, naturalists, and travelers worldwide to produce evidence for this. Such “sexual selection” happened among humans too. With primitive societies accepting diverse notions of beauty, aesthetic preferences, he believed, could account for the origin of the human races.

Darwin finished another long-standing line of work. Since studying the moody orangutans at London Zoo in 1838, Darwin had been fascinated by facial expression. As a student he had heard the attacks on the idea that people's facial muscles were designed by God to express their unique thoughts. Now his photographically illustrated
The Expression of the Emotions in Man and Animals
(1872) expanded the subject to include the rages and grimaces of asylum inmates, all to show the continuity of emotions and expressions between humans and animals.

The treadmill of experiment and writing gave much meaning to Darwin's life. But as he wrapped up his final, long-term interest, publishing
The Formation of Vegetable Mould, Through the Action of Worms
(1881), the future looked bleak. Such an earthy subject was typical Darwin: just as he had shown that today's ecosystems were built by infinitesimal degrees and the mighty Andes by tiny uplifts, so he ended on the monumental transformation of landscapes by the Earth's humblest denizens.

(b. Feb. 16, 1822, near Sparkbrook, Birmingham, Warwickshire, Eng.—d. Jan. 17, 1911, Grayshott House, Haslemere, Surrey)

E
nglish explorer, anthropologist, and eugenicist Sir Francis Galton was known for his pioneering studies of human intelligence. He was knighted in 1909.

When Galton was a young man, he traveled in southeastern Europe. From Vienna he made his way through Constanza, Constantinople, Smyrna, and Athens, and he brought back from the caves of Adelsberg (present-day Postojina, Slovenia) specimens of a blind amphibian named
Proteus
—the first to reach England. On his return Galton went to Trinity College, Cambridge, where he was a medical student and where, as a result of overwork, he broke down in his third year. But he recovered quickly on changing his mode of life, as he did from similar attacks later.

After leaving Cambridge without taking a degree, Galton continued his medical studies in London. But before they were completed, his father died, leaving him “a sufficient fortune to make me independent of the medical profession.” Galton was then free to indulge his craving for travel. Leisurely expeditions in 1845–46 up the Nile with friends and into the Holy Land alone were preliminaries to a carefully organized penetration into unexplored parts of southwestern Africa. After consulting the Royal Geographical Society, Galton decided to investigate a possible opening from the south and west to Lake Ngami, which lies north of the Kalahari desert some 550 miles east of Walvis Bay.

The expedition, which included two journeys, one northward, the other eastward, from the same base,
proved to be difficult and not without danger. Though the explorers did not reach Lake Ngami, they gained valuable information. As a result, at the age of only 31, Galton was in 1853 elected a fellow of the Royal Geographical Society and, three years later, of the Royal Society. In 1853, too, Galton married. There were no children of the marriage. Galton wrote 9 books and some 200 papers. They deal with many diverse subjects, including the use of fingerprints for personal identification, the correlational calculus (a branch of applied statistics)—in both of which Galton was a pioneer—twins, blood transfusions, criminality, the art of travel in undeveloped countries, and meteorology. Most of Galton's publications disclose his predilection for quantifying; an early paper, for example, dealt with a statistical test of the efficacy of prayer. Moreover, over a period of 34 years, he concerned himself with improving standards of measurement.