Date: 1835
Owner: D. Appleton and Company
Source Type: Images

On the Galapagos Islands (galapago is Spanish for giant tortoise), Darwin saw tortoises that had shells over a yard long and weighed up to 500 pounds (he even noted how he rode on the back of one without slowing the behemoth's progress). He captured a few young ones and brought them back to England, along with a small menagerie of birds, plants, insects, and reptiles.

The giant tortoises are but one example of the striking oddity of life on the Galapagos, which are home to several species of plants, reptiles, birds, and crustaceans found no where else in the world, including other isles in that archipelago. Although he did not publish his theory of evolution for many years after his 1835 excursion at Galapagos, the diversity of life he observed and collected there was instrumental to its development. He reasoned that an ancestor of each unique species--such as the black iguana or flightless cormorant--made its way to the Galapagos at some ancient point in history, and adapted over millennia to its surroundings. The random adaptations that proved most conducive to survival became widespread while those varieties that developed less efficiently became extinct.

Empirical observations on a remote Ecuadorian island catalyzed a theory that would force Western civilization to rethink its most fundamental axioms. Although Darwin's theory has itself evolved since the mid nineteenth century, many of his assertions still hold sway in modern biology.

CITATION: Tortoise. Darwin, Charles. Journal of Researches into the Natural History and Geology of the Countries Visited During the Voyage Round the World of H.M.S. 'Beagle' Under the Command of Captain Fitz Roy, R.N. New York: D. Appleton and Company, 1890.