Darwin's Forgotten Metaphor: Wedges and the Unseen Hammerer
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In the 1830s, Charles Darwin sent a letter from South America to his mentor John Henslow, of his recent forays in the passes and plateaus of the Andes. … In the letter, he describes a scene full of “wedges of variously coloured rocks … in every possible shape and formation.” … In 1838, puzzling over the birth of new species, he was seized by an image different and stranger than natural selection. He wrote in his notebook of “a hundred thousand wedges trying [to] force every kind of adapted structure into the gaps in the economy of Nature, or rather forming gaps by thrusting out weaker ones.” In his vision, space was tight.
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Over the next 20 years, Darwin returned to the idea of wedges regularly. In the metaphor’s fullest treatment, written in an unpublished precursor to The Origin of Species, he describes species as “packed closely together and … driven in by incessant blows,” as though they were wedges being struck again and again by a mallet. The wedges, he wrote, were of varying shapes and the shocks from each blow traveled across the field in all directions.
The wedges-as-species comparison made it as far as Darwin’s first edition of The Origin of Species, published in 1859. But at some point soon after Darwin abruptly removed it, and it never appeared again. Today, Darwin’s eerie metaphor of a vast and wedge-filled landscape, pounded by the blows of an unseen hammerer, is … all but forgotten. He never explained why he dropped it, but one possible reason is that he doubted people would like it. To those with no interest in rocks, such a metaphor would have seemed bleak and alien. … It’s nature as whack-a-mole, with humans as just another mole being whacked into – and perhaps one day out of – existence. One modern scholar describes the idea as “grotesque” and even “shockingly sadistic.” To Darwin’s readers, imagining the history of life in such violent and mechanical terms might have been at least unpalatable, and at most unbearable.
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Whatever his reasons for abandoning the wedges, it was likely not a rash decision. Darwin did not take metaphors lightly. He … held on to them tightly, defying detractors. Several of his contemporaries were displeased with “natural selection.” His rival turned comrade-in-arms, Alfred Wallace, was particularly critical. In a letter to Darwin, Wallace argued … that the word “selection” encouraged readers to view nature as a forward-looking, intelligent designer that was shaping the evolutionary course of life. Wallace was astute in his reading of Darwin’s language. According to Darwin biographer Janet Browne, Darwin often seemed to imagine nature as an “all-seeing farmer in the sky,” a benevolent overseer that selects, scrutinizes, and rejects. As Wallace saw it, the problem with this rosy view is that, strictly speaking, it’s wrong. There is no nice, celestial farmer – just a struggle for existence, with winners and losers.
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Over the objections of Wallace and others, Darwin clung to “natural selection” even as he discarded the wedges. Perhaps he sensed the power of his “all-seeing farmer” and, in doing so, intuited something deep about human psychology. People are deeply familiar with the logic of purposeful design, and research has shown that they like to view the world through this lens…
