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LEAFING THROUGH THE MAIL at his home near London, one June day 150 years ago, Charles Darwin came across an envelope sent from an island in what is now Indonesia.
The writer was a young acquaintance, Alfred Russel Wallace, who eked out a living as a biological collector, sending butterflies, birds and other specimens back to England. This time, Wallace had sent a 20-page manuscript, asking Darwin to show it to other members of the British scientific community.
As he read, Darwin saw with dawning horror that the author had arrived at the same evolutionary theory he had been working on, without publishing a word, for the last two decades. "All my originality, whatever it may amount to, will be smashed," he lamented in a note to his friend, the geologist Charles Lyell.
Darwin ventured that he would be "extremely glad now" to publish a brief account of his own lengthy manuscript, but that "I would far rather burn my whole book than that [Wallace] or any man should think that I had behaved in a paltry spirit."
The threat to his life's work could hardly have come at a worse moment. Darwin's daughter Etty, 14, was seriously ill with diphtheria. His 18-month-old son, Charles, would soon lie dead of scarlet fever. Lyell and another of Darwin's friends, the botanist Joseph Hooker, cobbled together a compromise, rushing both Darwin's and Wallace's works before a meeting of the Linnean Society a few days later, on 1 July 1858.
The reading took place in a narrow, stuffy ballroom at Burlington House, just off Piccadilly Circus, and neither author was present. (Darwin was at his son's funeral; Wallace was in New Guinea.) Nor was there any discussion. The society's president went home muttering about the lack of any "striking discoveries" that year. And so began the greatest revolution in the history of science.
WE CALL IT DARWINISM, for short. But in truth, it didn't start with Darwin, or with Wallace either, for that matter. Great ideas seldom arise in the romantic way we like to imagine – the bolt from the blue, the lone genius running through the streets crying, "Eureka!" Like evolution itself, science more often advances in small steps, with different lines converging on the same solution.
"The only novelty in my work is the attempt to explain how species become modified," Darwin later wrote. He did not mean to belittle his achievement. The how, backed up by an abundance of evidence, was crucial: nature throws up endless biological variations, and they either flourish or fade away in the face of disease, hunger, predation and other factors.
Darwin's term for it was "natural selection"; Wallace called it the "struggle for existence". But we often act today as if Darwin invented the idea of evolution itself, including the theory that human beings developed from an ape ancestor. And Wallace we forget altogether.
In fact, scientists had been talking about our primate origins since at least 1699, after the London physician Edward Tyson dissected a chimpanzee and documented a disturbing likeness to human anatomy. And the idea of evolution had been around for generations.
In the 1770s, Darwin's grandfather Erasmus Darwin, a physician and philosopher, publicly declared that different species had evolved from a common ancestor. He even had the Latin motto "E conchis omnia" ("Everything from shells") painted on his carriage.
In the 1794 book of his two-volume Zoonomia, the elder Darwin ventured that over the course of "perhaps millions of ages ... all warm-blooded animals have arisen from one living filament," acquiring new traits and passing down improvements from generation to generation. His contemporary Samuel Taylor Coleridge mocked this sort of evolutionary theory as "darwinising". But it was by no means a family monopoly.
