HMS Beaglesails through the Straits of Magellan Wikimedia CommonsAfter having been twice driven back by heavy southwestern gales, Her Majestys ship Beagle, a ten-gun brig, under the command of Captain Fitz Roy, R.N., sailed from Devonport on the 27th of December, 1831. So begins The Voyage of the Beagle, Charles Darwins account of his trip around the coast of South America, between the islands of the Galpagos, and back to Englanda journey that inspired his theory of evolution by natural selection.Darwin was a young man of 22 at the time, a recent graduate of Christs College, Cambridge, where his intention to become an Anglican priest had morphed into studies in botany, animal biology and geology.In August 1831, Darwin received a letter from his mentor, fellow geologist John Stevens Henslow, explaining that the Beagles new captain Lieutenant Robert Fitzroy was seeking an assistant who could help with collecting, observing, & noting anything worthy to be noted in Natural History on an upcoming voyage.I have stated that I consider you to be the best qualified person I know of who is likely to undertake such a situation, Henslow wrote.Dawins father, however, took a much different view of his sons qualifications and strongly opposed the voyage. His father wanted him to settle down as a clergyman, so Darwin politely declined the offer. If it were up to him, I should I think, certainly most gladly have accepted the opportunity, Darwin wrote back to Henslow.Just a few days later, his fathers mind changed. Darwin hastened to accept the offer to see the watery part of the world and all its thrilling natural features. The expedition would, in Darwins words, complete the survey of Patagonia and Tierra del Fuego survey the shores of Chile, Peru and of some islands in the Pacific.As the Beagle left England on December 27, its crew fell into a routine that would last the next five years. While others dedicated themselves to mapping and surveying work, Darwin took the role of a gentleman naturalist, strolling about and making geological and zoological observations.He religiously kept a journal of his detailed notes as not a record of facts but of my thoughts, as he described it in a letter to his sister. He also became an avid reader of the Principles of Geology by Charles Lyell, a prominent geologist. Among other things, Lyells work aimed to show that small, incremental changes could have profound effects over long periods of time.The Beagle reached the Galpagos Islands, a volcanic archipelago in the Pacific Ocean, in September 1835. As the ship hopped between the islands, Darwin industriously collected all the animals, plants, insects & reptiles from each, he noted in his journal.Later, someone aboard the ship pointed out that the tortoises differed from the different islands, and that he could with certainty tell from which islands any one was brought. This gave the scientist the inkling that evolution could take different paths of speciation depending on an islands unique conditions. Perhaps small changes in species over time, branching out from a single ancestor, could result in starkly unique tortoises, Darwin reasoned.Upon the Beagles return to England in October 1836, the idea was still just an inkling. It would take another 23 years, including a friendship with Lyell and a retreat into English country life, until Darwin fully fleshed out his vision of evolution in the groundbreaking On the Origin of Species. Small things, after all, accumulate when given enough time.Get the latest stories in your inbox every weekday.Filed Under: Charles Darwin, Evolution, On This Day in History, Ships