Charles Darwin was born on Feb. 12, 1809. He was an English naturalist renowned for his documentation of evolution and for his theory of its operation, known as Darwinism. His evolutionary theories, propounded chiefly in two works--On the Origin of Species by Means of Natural Selection (1859) and The Descent of Man, and Selection in Relation to Sex (1871)--have had a profound influence on subsequent scientific thought.
Darwin was the son of Robert Waring Darwin, who had one of the largest medical practices outside of London, and the grandson of the physician Erasmus Darwin, the author of Zoonomia, or the Laws of Organic Life, and of the artisan-entrepreneur Josiah Wedgwood. Darwin thus enjoyed a secure position in the professional upper middle class that provided him with considerable social and professional advantage.
Darwin`s mother died when he was eight years old. Otherwise he enjoyed a golden childhood, cosseted and encouraged by adoring sisters, an older brother, and the large Darwin and Wedgwood clans. He was keenly interested in specimen collecting and chemical investigations. At age 16 he was sent to study medicine at the University of Edinburgh, where he was repelled by surgery performed without anesthetics. During his two years in Scotland Darwin benefited from friendships with the zoologist Robert Grant, who introduced him to the study of marine animals, and the geologist Robert Jameson, who fed his growing interest in the history of the Earth.
Disappointed by Darwin`s lack of enthusiasm for medicine, his father sent him to the University of Cambridge in 1827 to study divinity. At the time Darwin adhered to the conventional beliefs of the Church of England. His academic record at Christ`s College was as undistinguished as it had been at Edinburgh.
On leaving Cambridge in the spring of 1831 Darwin, in preparation for a scientific trip to the Canary Islands, read Alexander von Humboldt`s Personal Narrative of Travels to the Equinoctial Regions of the New Continent, a scientific travelogue of a journey to Central and the northern parts of South America. At Henslow`s recommendation he accompanied Adam Sedgwick, Woodwardian professor of geology at Cambridge, on a three-week tour of North Wales to learn geologic fieldwork.
In August 1831, at Henslow`s recommendation to the Admiralty, Darwin was invited to sail as the unpaid naturalist on HMS Beagle. The ship was to survey the east and west coasts of South America and continue to the Pacific islands to establish a chain of chronometric stations.
Henslow suggested Darwin as both an acute observer and a companion for the aristocratic young captain, Robert FitzRoy. (The Beagle already had a naturalist-surgeon, but one whom FitzRoy found socially unsuitable.) Robert Darwin first refused permission on grounds that it was dangerous and would not advance Charles in his career. But upon the intercession of his brother-in-law, Josiah Wedgwood II, he changed his mind.
On Dec. 27, 1831, Charles Darwin sailed from Plymouth, Eng., on the Beagle, a 10-gun brig that had been refitted as a three-masted bark. The voyage, planned for two years, lasted five, during which Darwin kept meticulous notes and sent back geologic and biologic specimens.
The Voyage of the "Beagle"
In a letter to FitzRoy accepting the post Darwin explained that he expected the voyage to be a "second birth."
There is no doubt that the years he spent exploring the South American continent and the offshore islands of the Galapagos honed his skills as a collector, observer, and theorist.
Often seasick, Darwin rested horizontally in a hammock during the worst motion and spent long periods of time ashore whenever the opportunity arose. He delighted in the exotica of the tropics.
On the Origin of Species
When Darwin returned to England in 1836 he was welcomed by the scientific fraternity as a colleague and was promptly made a fellow of the Geological Society. The next year he was elected to its governing council.
Privately Darwin had begun a remarkable series of notebooks in which he initiated a set of questions and answers about "the species problem." He proceeded to collect facts about species through letters and discussions with breeders, gardeners, naturalists, and zookeepers, as well as through extensive reading.
Darwin kept this interest secret while he gathered evidence to substantiate his theory of organic evolution. He was mindful of the fate of other unorthodox scientists. He jotted in his notebook, "Mention persecution of early astronomers--then add chief good of individual scientific men, is to push their science a few years in advance only of their age."
Darwin`s ideas were not only scientifically radical but also could have been interpreted as actionable under the laws governing blasphemy and sedition.
England at the time was intensely evangelical, and the natural world was understood as one in which the spirit of God could be seen in the creation of new species of plants and animals that appeared to come into existence to replace those that became extinct. Darwin gradually became intellectually uncomfortable with this view of life as he confronted puzzling evidence.
Upon his return from the voyage Darwin had turned over his specimens to cataloging experts in Cambridge and London. In South America he had found fossils of extinct armadillos that were similar but not identical to the living animals.
Argentina he had seen species vary geographically; for example, the giant ostriches (rheas) on the pampas were replaced to the south in Patagonia by much smaller species, both of which were akin to but different from the African ostrich.
He had been disturbed by the fact that the birds and tortoises of the Galαpagos Islands off the western coast of Ecuador tended to resemble species found on the nearby continent, while inhabitants of similar neighbouring islands in the Galapagos had quite different animal populations.
In London Darwin learned that the finches he had brought from the Galαpagos belonged to different species, not merely different varieties, as he had originally believed. He also learned that the mockingbirds were of three distinct species and that the Galapagos tortoises represented at least two species and that, like many of the specimens from the archipelago, they were native to the islands but to neither of the American continents.
After Darwin received these reports, his doubts about the fixity of species crystallized into a belief in transmutation. In March 1837 he confided in his notebook that species changed from one place to another or from one era to the next. He continued analyzing his data, searching for a mechanism for this process.
Then in October 1838 Darwin read Thomas Malthus` An Essay on the Principle of Population. Malthus argued that population growth is geometric, while the food supply increases only arithmetically, and thus that population increase is always checked by a limited food supply.
By 1842 Darwin was confident enough in his theory to draft a short sketch, and in 1844 he composed a longer version, which he showed to his friend, the botanist Joseph Dalton Hooker. Wary of presenting his theory to the public, Darwin spent the next decade concentrating on a treatise on barnacles, in which he hinted but did not actually say that species were the product of natural selection. In the meantime the intellectual atmosphere in England altered and discussions about evolution became commonplace.
The second half of the book elaborated upon the theory of sexual selection. Darwin observed that in some species males battle other males for access to certain females. But in other species, such as peacocks, there is a social system in which the females select males according to such qualities as strength or beauty.
Twentieth-century biologists have expanded this theory to the selection by females of males who can contribute toward the survival of their offspring; i.e., female selection secures traits that make the next generation more competitive.