What Darwin Didn't Know- page 2 | Science | Smithsonian
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"Light will be thrown on the origin of man and his history," Darwin (c.1880) said of a future in which his hard-won findings would be tested. (Bettmann / Corbis)

What Darwin Didn't Know

Today's scientists marvel that the 19th-century naturalist's grand vision of evolution is still the key to life

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(Continued from page 1)

Darwin began training to be a physician but didn't have a taste for doctoring, so he moved on to studying for the Anglican priesthood at Cambridge. His real passion, however, was natural history. Shortly after graduation in 1831, he signed on for an unpaid position as a naturalist aboard the Beagle, which was about to embark on a survey of South American coastlines. During the five-year voyage Darwin collected thousands of important specimens, discovered new species both living and extinct and immersed himself in biogeography—the study of where particular species live, and why.

Upon his return to England in 1836, Darwin stayed busy, publishing scientific works on the geology of South America, the formation of coral reefs and the animals encountered during his Beagle expedition, as well as a best-selling popular account of his time aboard the ship. He married his cousin, Emma Wedgwood, in 1839, and by 1842 the growing Darwin family was established at Down House, in a London suburb. Charles, plagued by poor health, settled down with a vengeance.

By 1844, he was confiding in a letter to a fellow naturalist, "I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable." Still, he hesitated to publicize the idea, instead plunging into the study of domestic animal breeding—natural selection, he would argue, is not unlike the artificial selection practiced by a breeder trying to enhance or eliminate a trait—and the distributions of wild plants and animals. He devoted eight full years to documenting minute anatomical variations in barnacles. A prolific letter writer, he sought samples, information and scientific advice from correspondents around the world.

It was a young naturalist and professional specimen collector named Alfred Russel Wallace who finally spurred Darwin to publish. Working first in the Amazon and then in the Malay Archipelago, Wallace had developed an evolution theory similar to Darwin's but not as fully substantiated. When, in 1858, Wallace sent the older man a manuscript describing his theory of evolution, Darwin realized that Wallace could beat him into print. Darwin had an essay he had written in 1844 and Wallace's manuscript read at a meeting of the Linnean Society in London on July 1, 1858, and published together later that summer. Wallace, then on an island in what is now Indonesia, wouldn't find out about the joint publication until October. "There's been an argument about whether Wallace got screwed," says Sean B. Carroll, a biologist and author of books on evolution. "But he was delighted. He was honored that his work was considered worthy" to be included alongside that of Darwin, whom he greatly admired.

This first public airing of Darwinian evolution caused almost no stir whatsoever. But when Darwin published his ideas in book form the following year, the reaction was quite different. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life soon sold out its first press run of 1,250 copies, and within a year some 4,250 copies were in circulation. Allies applauded it as a brilliant unifying breakthrough; scientific rivals called attention to the gaps in his evidence, including what would come to be known as "missing links" in the fossil record; and prominent clergymen, politicians and others condemned the work and its far-reaching implications. In 1864 Benjamin Disraeli, later Britain's prime minister, famously decried the idea—barely mentioned in Origin—that human beings too had evolved from earlier species. "Is man an ape or an angel?" he asked rhetorically at a conference. "I, my lord, I am on the side of the angels. I repudiate with indignation and abhorrence those newfangled theories."

Darwin had anticipated such protests. "Any one whose disposition leads him to attach more weight to unexplained difficulties than to the explanation of a certain number of facts will certainly reject my theory," he wrote in Origin. But, he also said, "I look with confidence to the future, to young and rising naturalists, who will be able to view both sides of the question with impartiality."

The age of the earth was, for Darwin, a major unexplained difficulty. He recognized that a great deal of time must have been necessary for the world's diversity of plants and animals to evolve—more time, certainly, than the 6,000 years allowed by the leading biblical interpretation of earth's age, but more also than many scientists then accepted. In 1862, the physicist William Thomson (later Lord Kelvin) calculated that the planet was unlikely to be more than 100 million years old—still nowhere near enough time for evolution to have acted so dramatically. "Thomson's views on the recent age of the world have been for some time one of my sorest troubles," Darwin wrote to Wallace in 1869. Further studies, including one by Darwin's son George, an astronomer, fixed earth's age at well under 100 million years.

It wouldn't be until the 1920s and 1930s that geologists, calculating the rates of radioactive decay of elements, concluded that the earth was billions of years old—according to the latest studies, 4.5 billion years. Darwin surely would have been relieved that there was enough time for evolution to have accounted for the great diversity of life on earth.

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