Friday, August 21, 2015

Adventure classics – Neglected finches of the Galápagos

The Voyage of HMS Beagle
by Charles Darwin
Charles Darwin’s mind was so far from formulating his theory of evolution by natural selection that he initially overlooked the significance of the Galápagos Islands’ now-famous finches. As the official geologist of the Royal Navy’s survey ship, HMS Beagle, he considered the obvious volcanic origin of the islands their most striking aspect when he first caught sight of them September 15, 1835.

The original plan of a two-year voyage to survey the coasts of South America had stretched to nearly four years by the time the Beagle rounded the continent’s southernmost tip and reached its western extremity in the archipelago that had first gained notoriety as a pirate hideaway.

Darwin evoked shivers in his readers with the tale of a ship’s captain murdered by mutineers, his skull still visible in the underbrush. And he was still young enough to thrill at catching a ride on the immense tortoises: “I frequently got on their backs, and then giving a few raps on the hinder part of their shells, they would rise up and away; -- but I found it very difficult to keep my balance,” he admitted in his journal of the Beagle’s voyage.

He noted that “there can be little doubt that this tortoise is an aboriginal inhabitant of the Galápagos” and was struck by the islands’ seagoing iguanas (but not realizing they were in fact, the only such species), the birds he described as “finches,"  later realized to be more closely related to tanagers, did not at first excite his interest.

Rather than being “brilliantly colored, as might have been expected in an equatorial district. . . the males of all, or certainly of the greater number, are jet black; and the females (with perhaps one or two exceptions) are brown. The most curious fact is the perfect gradation in the size of the beaks. . .”

He was an avid collector (his days spent shooting while at Cambridge were paying off), but still so far from forming a theory of evolution of species that he neglected to keep records of which “finch” came from which of the archipelago’s numerous islands.

The Beagle finally returned to England in October 1836, after circumnavigating the globe, and in January 1837 Darwin presented the preserved “finches” along with his other bird and mammal specimens to the Geological Society of London. Not until he received a report from the society’s ornithologist did the possibility of the birds being unique to each island – and the implications of that fact for the transmutation of species – occur to him.

Fortunately, the Beagle’s Captain Fitzroy had also collected bird specimens, labelled according to island by his steward Harry Fuller and Darwin’s servant Syms Covington. These specimens helped him reconstruct the locations where his own birds had been shot.

Seventy years after Darwin set foot on the Galápagos islands and nearly a half-century after the publication of his landmark volume, On the Origin of Species, a more comprehensive collection of birds gathered by the 1905-06 Galápagos expedition by the California Academy of Sciences (link) would further confirm the significance of the little birds immortalized as the Galápagos finches.

(The picture illustrating this post is a facsimile of the original illustration in The Voyage of HMS Beagle, engraved for a 1957 edition by Ralph Beedham, although a version is also available on Wikipedia.)

(Next Friday, Adventure classics sees Darwin across the Pacific, concluding an August of adventures at sea.)

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