When Charles Darwin began his five-year voyage around the world in 1831, he was little more than an enthusiastic amateur naturalist set on a career in the clergy. His formative years had been directionless, and at Edinburgh University he found the lectures stultifying; even those in geology – a subject that became a passion in later life – he described as “incredibly dull”. At Cambridge, studying divinity, he only just scraped through without honours. Yet it was there where he met Professor of Botany John Henslow, who recognized in the 22-year-old a talented mind with a flair for science. Henslow immediately recommended Darwin to Captain FitzRoy, who was seeking a naturalist on an expedition to chart the coast of South America. They set sail on HMS Beagle in December 1831.
Darwin suffered from terrible seasickness; whenever he could, he stayed on land and in the five-year voyage spent only eighteen months at sea. On September 15, 1835, the Beagle arrived at the Galápagos. “Nothing could be less inviting,” he wrote, “the country is comparable to what one might imagine the cultivated parts of the Infernal regions to be.” In the five weeks spent in the archipelago, he feverishly set about collecting samples and was taken aback by the “tameness” of the islands’ creatures.
Darwin noticed countless things previous visitors hadn’t. Still, it’s clear his experiences on the islands only planted the seeds of ideas that were to blossom on his return to England. Indeed, already exhausted from four years of hard travel, Darwin’s normally fastidious sampling was somewhat slapdash in the Galápagos. He failed to label the source islands of his bird collections (“it never occurred to me that, the productions of islands only a few miles apart, and placed under the same physical conditions, would be dissimilar”), and even misidentified the now celebrated Darwin’s finches. It wasn’t until his return to London, after the taxonomist John Gould had examined Darwin’s samples and told him about the thirteen closely related species of finch, that the penny dropped. Despite giving acclaimed lectures about his geological discoveries and publishing the Voyage of the Beagle in 1839, he only hinted at the big ideas troubling him. For example, about the finches, he writes “there is not space in this work, to enter on this curious subject”.
Instead, he set about working over his ideas in near secret in his famous Transmutation Notebooks, the first of which begins: “Had been greatly struck… on character of South American fossils and species on Galápagos Archipelago. These facts origin (especially latter) of all my views.” He saw the volcanic islands were relatively new and that life on the islands bore a resemblance to species in South America but were different in crucial ways. Darwin also realized life had come to the barren islands by air or sea and had adapted to the harsh environment through a process he termed “natural selection”. In this, he maintained that at a given time certain members of a species are more suited to their surroundings than others and are therefore more likely to survive in it, so passing on their advantageous characteristics to their offspring. Over the course of time an entire population would come to develop those special features, eventually to such a degree as to become a new species – what Darwin called “descent with modification”, rather than “evolution”, which implied progressive movement towards the highest point of development. In his groundbreaking model, change was without direction and could result in a number of new species coming from a single ancestor.
It pained Darwin to know his ideas would upset the public and the Church, and he sat on his theory for nearly twenty years, quietly amassing the information to back it up. It took a letter from Alfred Russel Wallace, who had arrived at a similar conclusion (though without Darwin’s intellectual rigour), to jerk him into action. In 1858 they offered a joint paper on their findings to the Linnaean Society in London and a year later Darwin published On the Origin of Species, which sold out in a day. It sent shockwaves throughout the Western world and opened up to science areas that had previously been the province of philosophers and theologians. Intense debate followed, but by the time of Darwin’s death in 1882, the notion of evolution was well established. The most important, original and far-seeing part of his theory – natural selection – was still highly controversial; it was only in the 1930s that it received the full recognition it deserved, forming the basis of modern biology and forever changing humanity’s view of itself.