This is a classic episode in the history of science, a story of a coincidence and its aftermath, told and retold in books about how evolutionary biology came to be: the near simultaneous formulation of what we now think of as Darwin's theory by Darwin himself and a young upstart, Alfred Russel Wallace. Classic or not, many people nowadays are unaware of it. Wallace, famed during his life as Darwin's junior partner and for his other contributions to science and social thought, fell into obscurity after his death, in 1913. In recent decades his renown has been revivified, both by scholars who mine every aspect of Darwin's life—Wallace was a crucial part—and by a few popular writers. His grave marker, in the village of Broadstone, no longer stands crumbling and overgrown by tree limbs. His portrait now hangs, along with an older one of Darwin, in the meeting room of the Linnean Society in London, the same scientific society to which the Darwin-Wallace co-discovery was announced 150 years ago, on the evening of July 1, 1858. His writings, on subjects from evolutionary theory and social justice to life on Mars, are coming back into print or turning up on the Web. He is recognized among science historians as a founder of evolutionary biogeography (the study of which species live where, and why), as a pioneer of island biogeography in particular (from which the science of conservation biology grew), as an early theorist on adaptive mimicry, and as a prescient voice on behalf of what we now call biodiversity. That is, he's a towering figure in the transition from old-fashioned natural history to modern biology. During his years afield Wallace was also a prolific collector, a ruthless harvester of natural wonders; his insect and bird specimens added richly to museum holdings and the discipline of taxonomy. Still, most people who know of Alfred Russel Wallace know him only as Charles Darwin's secret sharer, the man who co-discovered the theory of evolution by natural selection but failed to get an equal share of the credit.
Wallace's story is complicated, heroic, and perplexing. Besides being one of the greatest field biologists of the 19th century, he was a man of crotchety independence and lurching enthusiasms, a restless soul never quite satisfied with the place in which he lived, a believer in spiritualism and séances, a devotee of phrenology, a dabbler in mesmerism, a later apostate from Darwinian theory when it came to the development of the human brain, an opponent of smallpox vaccination, and an advocate of nationalizing large private landholdings, who by these and other eccentricities gave his detractors some grounds for dismissing him as a crank. Which they did. The question that no scholar or biographer has adequately answered is: How to reconcile such brilliant achievements, radical convictions, and incautious zealotries within one human character—the character of a consummate empiricist and field naturalist? If he hadn't existed, this Alfred Wallace, it would have taken a very peculiar Victorian novelist to create him.