Henry Nicholls writes: When the HMS Beagle dropped anchor on San Cristobal, the easternmost island in the Galapagos archipelago, in September 1835, the ship’s naturalist Charles Darwin eagerly went ashore to gather samples of the insects, birds, reptiles, and plants living there. At first, he didn’t think much of the arid landscape, which appeared to be “covered by stunted, sun-burnt brushwood…as leafless as our trees during winter” But this did not put him off. By the time the Beagle left these islands some five weeks later, he had amassed a spectacular collection of Galapagos plants.
It is fortunate that he took such trouble. Most popular narratives of Darwin and the Galapagos concentrate on the far more celebrated finches or the giant tortoises. Yet when he finally published On the Origin of Species almost 25 years later, Darwin made no mention of these creatures. In his discussion of the Galapagos, he dwelt almost exclusively on the islands’ plants.
By the early 19th century, there was increasing interest in what we now refer to as biogeography, the study of the distribution of species around the globe. Many people still imagined that God had been involved in the creation of species, putting fully formed versions down on Earth that continued to reproduce themselves, dispersing from a divine “center of creation” to occupy their current habitats. To explain how the plants and animals reached far-flung places such as the isolated Galapagos, several naturalists imagined that there had to have been land bridges, long-since subsided, that had once connected them to a continent. But in the wake of the Beagle voyage, the collection of Galapagos plants suggested an alternate scenario.
Even if there had once been a land bridge to the islands, it could not account for the fact that half of the plant species Darwin collected were unique to the Galapagos, and that most of them were particular to just one island. “I never dreamed that islands, about fifty or sixty miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under a quite similar climate, rising to a nearly equal height, would have been differently tenanted,” wrote Darwin in his Journal of Researches. His observations could be best explained if species were not fixed in nature but somehow changed as the seeds traveled to different locations. [Continue reading…]