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Like Confessing a Murder

Part of the Darwin exhibition.

Once settled at Down House, Darwin wrote a fuller version of his theory of evolution by natural selection. Yet he didn't publish it--why?

There are several reasons. Darwin's theory was still incomplete; he wanted to think more, gather more evidence. Other writers, with other evolutionary schemes, were being ridiculed, and Darwin was determined to avoid that fate. His own ill health and family tragedy interfered with work. Imagining the reaction of the public and the established church filled him with dread.

Yet gradually, over a decade or so, Darwin began letting a few trusted friends in on the secret. It was "like confessing a murder," he wrote. But private confession was one thing; telling the world, quite another. Darwin intended to work at his own pace, until his theory was solid enough to satisfy his severest critic--himself.

A Step Closer

This landmark manuscript on evolution by natural selection dates from early 1844. Writing it took Darwin one giant step closer to what he called his "big book on species." In this essay Darwin tackles the same topics he had covered in his brief outline two years earlier, but the treatment is much fuller. As his son Francis later noted, "In the 1844 Essay there is an air of freedom, as if the author was letting himself go." Darwin may have felt liberated because he never intended the Essay to be published in his lifetime--and indeed, it wasn't. But with it, Darwin crossed a threshold: almost all of his major thinking was in place.

In the page on display, Darwin discusses something he saw as a difficulty with his theory. Natural selection depended on variation, but Darwin was having a hard time determining how much variation actually existed in nature.

"Lamarck has observed that, as long as we confine our attention to one limited country, there is seldom much difficulty in deciding what forms to call species and what varieties; and that it is when collections flow in from all parts of the world that naturalists often feel at a loss to decide the limits of variation."