Evolutionary Road

Darwin’s great theory was years in the making

By Tom Chaffin | February 28, 2022
Flickr/Anthony C
Flickr/Anthony C

We think we know the story: Charles Darwin hitched a ride on the HMS Beagle to a distant Pacific archipelago called the Galápagos Islands. Looking around, he noticed some, well, peculiar-looking birds and turtles, and voila! In a blinding revelation, the theory of evolution emerged.

In truth, the Galápagos as the hallowed site where evolutionary lightning struck shortchanges Darwin’s real story, and the way science itself progresses. The Beagle spent just five weeks in the Galápagos, out of five-years of global travels, four years of which were in South America. From the journal and field notes Darwin kept, and his letters home, we know that he was taken by the islands, but he recognized nothing paradigm-shattering about them.

The barnacles that obscure Darwin’s history—and that of the theory of evolution—begin with his age: he was just 22 years old when the Beagle left England, and 25 when, in 1835, he visited the Galápagos. It was almost a lifetime later, at age 50, that he published On the Origin of Species.

When the Beagle embarked, Darwin was a novice naturalist. He had recently graduated from Cambridge, with the same bachelor’s degree held by Anglican priests. An invitation from the Beagle’s captain, to serve as a dinner-table conversationalist on topics of natural history, placed him on the ship. He had no formal role in its mission, which was to conduct marine surveys for commercial, military—and only incidentally scientific—purposes.

Darwin departed Britain in 1831 and returned in 1836, with his belief in the immutability of species largely intact. It was only in retrospect, and in particular as he organized his journals for publication and compared notes with other naturalists, that he began to systematically reconsider many past assumptions.

None of his writings from the voyage even make mention of the famous group of passerine species (“Darwin’s finches”) whose beaks and other variations would bolster his later theory of evolution. Indeed, his diary contains only one (passing) reference to any sort of Galápagos finch. But if Darwin didn’t write about the finches while in the Galápagos, he did collect them there, shooting and preparing specimens that he sent to England. In the process, he commingled the birds, failing to record on their labels the specific island on which each had been killed—a lapse in his usual fastidious attention to detail, and one that shows how little attention he was paying to island-to-island diversity. Not until 1837 in London, after the birds’ inspection by zoologist John Gould, did Darwin come to recognize the variations among them.

Similarly, although Darwin noted and recorded the behavior of the massive tortoises on the islands, their differences didn’t strike him until the governor of the Galápagos brought them to his attention. And as with the birds, it was another scientist, the French herpetologist Gabriel Bibron (studying specimens from other Galápagos expeditions) who later confirmed for him those variances.

Late in life, Darwin was asked directly whether he had been an evolutionist during his Beagle travels: “I believed in the permanence of Species,” he answered, “but, as far as I can remember, vague doubts occasionally flitted across my mind. … But I did not become convinced that species were mutable until, I think, two or three years had elapsed.”

The Galápagos was never his sole focus. About a year after the Beagle’s voyage ended, he referenced, roughly, the “character of S. American fossils—& species on Galapagos Archipelago,” in his notes, adding: “These facts origin (especially latter) of all my views.” But the opening sentence of On the Origin of Species doesn’t credit the Galápagos with a special role in his thinking. Instead, it’s the natural phenomena of the whole of the South American continent that Darwin claims as inspiration.

So how did the islands become synonymous with Darwin’s theoretical leap? Historian of science John van Wyhe has traced the linkage. Initially, and for 50 years after the great man’s death, van Wyhe wrote, “most accounts of the origins of Darwin’s theory … attribute no particular significance to his visit there as compared to South America.”

However, Darwin’s son (and biographer) Francis Darwin at least mentioned the islands in an 1888 entry in Britain’s Dictionary of National Biography, echoing his father’s early note: “And above all, he came back full of the thoughts on evolution impressed on him by South American fossils, by Galapagos birds, and by the general knowledge of the complex interdependence of all living things gained in his wanderings.”

Over time, Darwin’s use of Galápagos evidence in his theory morphed into a Eureka! moment. By van Whye’s count, in the early 20th century, about a quarter of publications referencing Darwin had him discovering evolution while he was in the islands.

Then in 1935, the centennial of the Beagle’s Galápagos sojourn, a group—sailing from San Francisco and calling itself the Darwin Memorial Expedition—physically reinforced the linkage. During a two-year voyage, the expedition members unveiled a monument on San Cristóbal Island, where Darwin first went ashore in the Galápagos. The inscription read, in part:

Charles Darwin landed on the Galapagos islands in 1835 and his studies … thereon led him for the first time to consider the problem of organic evolution. Thus was started that revolution in thought on this subject which has since taken place.

Later that year, a gathering of British scientists further ratified the connection, devoting a session to papers on the “Centenary of the landing of Darwin on the Galapagos Islands, and of the birth of the hypothesis of the ‘Origin of species.’”

“Now, for the first time,” noted van Wyhe, “Darwin was widely represented as discovering evolution on the Galapagos. The title of this section alone was reproduced in newspapers and journals throughout the world.”

Two hundred years after Darwin set sail on the Beagle, the notion that the Galápagos is, literally, the birthplace of the theory of evolution is commonplace. Among scientists and other intellectual pioneers, however, such breakthroughs rarely arrive as blinding revelations; they are more often the product of plodding, cumulative, laborious work, trial-and-error, even happenstance. And thus, for Darwin, there was no revelation in the Galápagos—no epiphany among the tortoises and finches there. The scientist and the science had to evolve.



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