Charles Darwin A statue of the naturalist at the Natural History Museum in London
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Editor's Note: We are reposting this article from the October 1996 issue of Scientific American in commemoration of Charles Darwin's 200th birthday this week.

After lunch on September 16, 1876, Charles Darwin stretched out on his drawing-room sofa, as was his unvarying routine, smoked a Turkish cigarette and read the “bloody old Times.” He often fumed at its politics (the editors supported the South in the American Civil War), and his wife, Emma, suggested that they give up the paper altogether. But he replied he would sooner “give up meat, drink and air.”

In the “Letters” column, he noticed a report that a young zoologist named Edwin Ray Lankester was bent on jailing a celebrated spirit medium, “Dr.” Henry Slade, who was bilking gullible Londoners. By hauling Slade into court as “a common rogue,” Lankester would become the first scientist to prosecute a professional psychic for criminal fraud—an action Darwin thought long overdue. Although he was delighted at Lankester’s attack on Slade, Darwin was distressed to learn that Alfred Russel Wallace, his friendly rival and co-discoverer of the theory of natural selection, was also a target.

The Slade trial was to become one of the strangest courtroom cases in Victorian England. Some saw it as a public arena where science could score a devastating triumph over superstition. For others, it was the declaration of war between professional purveyors of the “paranormal” and the fraternity of honest stage magicians. Arthur Conan Doyle, the zealous spiritualist whose fictional detective, Sherlock Holmes, was logic personified, characterized it as “the persecution [rather than prosecution] of Slade.” But what made the trial unique was that the two greatest naturalists of the century ranged themselves on opposite sides. The “arch-materialist” Darwin gave aid and comfort to the prosecution, and his old friend Wallace, a sincere spiritualist, was to be the defense’s star witness—making it one of the more bizarre and dramatic episodes in the history of science.

Wallace was respected as an author, zoologist, botanist, the discoverer of scores of new species, the first European to study apes in the wild and a pioneer in the study of the distribution of animals. But he constantly courted ruin by championing such radical causes as socialism, pacifism, land nationalization, wilderness conservation, women’s rights and spiritualism. In addition to his classic volumes on zoogeography, natural selection, island life and the Malay Archipelago, he had written Miracles and Modern Spiritualism, which lauded spirit-mediums. And he had just allowed a controversial paper on “thought transference” to be read at a meeting of the British Association for the Advancement of Science—touching off an uproar that led him to avoid scientific meetings for the rest of his life.

Wallace wanted the best of both worlds. With insects or birds, he was even more rigorous than Darwin in applying the principle of natural selection, but he questioned its efficacy for humans. If early hominids required only a gorilla’s intelligence to survive, Wallace asked, why had they evolved brains capable of devising language, composing symphonies and doing mathematics? Although our bodies had evolved by natural selection, he concluded, Homo sapiens has “something which he has not derived from his animal progenitors—a spiritual essence or nature . . . [that] can only find an explanation in the unseen universe of Spirit.” Wallace’s position did not stem from any conventional religious belief but from his long-standing interest in spiritualism: a melding of ancient Eastern beliefs with the Western desire to “secularize” the soul and prove its existence. When Wallace published this view in 1869, Darwin wrote him: “I differ grievously from you; I can see no necessity for calling in an additional and proximate cause [a supernatural force] in regard to Man.... I hope you have not murdered too completely your own and my child”—meaning their theory of natural selection.