Who Was Charles Darwin? Twenty Years of Not Publishing

Born in Shrewsbury in 1809 into a wealthy family, the grandson of both the physician and poet Erasmus Darwin, who had written speculatively about species changing, and of the potter Josiah Wedgwood, he was sent to Edinburgh to study medicine and left after two years, unable to tolerate surgery performed without anaesthetic. His father, exasperated, sent him to Cambridge to prepare for the clergy, which was a respectable holding position for a young man with private means and no direction. There he attached himself to the botanist John Stevens Henslow and became a serious beetle collector, and it was Henslow who recommended him in 1831 for an unpaid position aboard a naval survey vessel, chiefly as a gentleman companion for a captain who feared the isolation of command. His father objected and was talked round by an uncle.

The Beagle sailed at the end of 1831 and returned in October 1836, almost five years rather than the two planned, circumnavigating the globe while surveying the South American coast. Darwin was seasick for much of it and spent as much time ashore as possible, collecting and shipping specimens back to England, where Henslow circulated them and quietly built his reputation before he returned. What mattered most was not the Galapagos, which loom disproportionately in the popular account, but the accumulation of observations across a continent:

• •Fossil giant mammals in Argentina, including a giant ground sloth, resembling smaller living South American species rather than anything elsewhere, which suggested continuity within a region
• •An earthquake in Chile that raised the land visibly, and marine shells found high in the Andes, which made Lyell's gradual geology vivid rather than theoretical
• •The replacement of one species by a closely related one along the length of the continent, particularly among the rheas
• •Coral atolls, for which he proposed a theory of subsidence that was confirmed by drilling a century later, and which was his first significant scientific success
• •The Galapagos finches, whose significance he did not grasp at the time, having failed to label which island each came from, and which the ornithologist John Gould identified as distinct species on his return

The idea that species change was not new and was associated with disreputable speculation, including his own grandfather's. What was missing was a mechanism, and Darwin found one in 1838 after reading Malthus on population, who argued that populations increase faster than food supply and are checked by starvation and disease. The step is straightforward once stated: organisms produce far more offspring than can survive, individuals vary, some variations improve the chances of surviving and reproducing in a given environment, offspring inherit those variations, and over many generations the composition of a population shifts. Nothing directs the process and there is no goal, which is the part that was and remains hardest to accept. He extended it with sexual selection, which explains traits such as a peacock's tail that harm survival and improve mating success, and he applied the principle to descent, arguing that all living things share common ancestors, which makes the tree of life a genealogy rather than a classification.

He wrote a thirty-five-page sketch in 1842 and a two-hundred-and-thirty-page essay in 1844, gave his wife Emma instructions for publishing the latter if he died, and then did not publish. Several reasons operated together. He was genuinely anxious about the reception, both socially and for Emma, who was devout and troubled by what the argument implied. He was aware that a previous anonymous book on species change had been savaged for its lack of evidence, and he was determined not to be dismissed the same way, which is one honest reading of the barnacle years: eight volumes describing every known species of barnacle established him as a working systematist who understood variation within species in enormous detail. He was also chronically ill from the mid-1840s with symptoms nobody has diagnosed with confidence. The delay ended in June 1858, when Alfred Russel Wallace sent him an essay from Ternate describing natural selection, and friends arranged for both to be presented jointly to the Linnean Society. Darwin then wrote what he called an abstract in thirteen months, and On the Origin of Species sold out its first printing on the day of publication in November 1859.

The central mechanism has held up completely and the gaps in his account were real and known to him. He had no theory of inheritance, since Mendel's work was published in 1866 and ignored until 1900, and the blending inheritance assumed in his day would have diluted any new variation out of existence within a few generations, an objection raised forcefully at the time and not answered until genetics supplied particulate inheritance in the twentieth-century synthesis. His own proposed mechanism, pangenesis, was wrong. He underestimated the age of the Earth because the physics of the day, which did not know about radioactive heating, gave the sun far too short a life. He also wrote a great deal more than the one famous book, including studies of orchids, climbing plants, earthworms, emotional expression in humans and animals, and human evolution in The Descent of Man, which applied the theory to our own species and contained the sexual selection argument in full. He died in 1882 and was buried in Westminster Abbey, a few metres from Newton.

A young naturalist taken aboard a survey ship largely as a captain's companion spent five years collecting across South America and the Pacific, and in 1838, after reading Malthus, arrived at natural selection: more offspring than can survive, heritable variation, and differential reproduction with no goal or direction. He delayed publication for twenty years through anxiety, a determination to build unanswerable evidence and chronic illness, and published in 1859 only after Wallace sent him the same idea from the Malay Archipelago.