When Darwin returned to London he was already a celebrity in some scientific circles, since his mentor Henslow had shared many of his geological notes and biological findings with colleagues. After visiting family and friends Darwin returned to Cambridge and studied his notes, data, and samples with the help of many colleagues and scientists recommended by Henslow. Together they cataloged his collections from around the world and discussed many of the possibilities suggested by his geological findings and, most famously, discussed ideas about the variety of different species in the plant and animal kingdoms and whether or not species were immutable, as commonly assumed in those times. Darwin met British geologist Charles Lyell (1797-1875), with whom he discussed uniformitarianism. Lyell introduced Darwin to the young anatomist Richard Owen, and together they identified several extinct species that closely resembled living species in south America.
In December 1836 Darwin began writing up much of his work. He surmised that the south American continent was slowly rising and presented this idea to the Geological society of London on January 4, 1837, the same day he presented his collections of mammals and birds to the zoological society, where ornithologist John Gould identified the Galápagos birds as 12 separate species of finches. Darwin moved to London and continued his work and discussions with other scientists. By spring and summer 1837 Darwin's notebooks showed that he had derived his ideas that different species transmuted into other species and formed a branching evolutionary tree in which species merged backward in time to common ancestors. Darwin worked long hours and formally recorded his ideas in his journal in summer 1837. He had classified his numerous biological collections and derived the following ideas:
• Evolution did occur.
• Evolutionary change to form new species was gradual, requiring up to 3 million years.
• Natural selection was the main driving force for evolution.
• All the species of life that are present today came from a single unique life-form.
Darwin's theory states that within each species nature randomly selects which animal or plant will survive and which will die out. survival depends on how adaptable the species is to its surrounding dynamic environment.
By September 1837 Darwin developed health problems, including heart palpitations, and he rested for a while in the country. While there he observed the work of earthworms, then delivered a talk on the subject to the Geological Society in November, and in March 1838 Darwin became secretary of the society. His long hours of work took their toll, and Darwin developed more health problems such as stomach ailments, headaches, and heart symptoms, which caused him to be laid up for days at a time.
On November 11, 1838, Darwin proposed marriage to his cousin Emma Wedgwood, and she accepted. They were married on January 29, 1839, five days after the Royal Society of London elected him a fellow.
The Darwins returned to London, and for the next decade he prepared the results of his research for scientific publication. These works included his Journal and Remarks (The Voyage of the Beagle) published in 1839, and a book on coral reefs published in 1842. After this Darwin and his family moved to Down House outside London, so he could work in a more peaceful setting. Darwin's health continued to fluctuate, and in 1851 his daughter Annie became gravely ill and died. This loss led Darwin to abandon his faith in religion.
Darwin continued working to publish his main ideas, sometimes fearing he would die before his work was complete. In June 1858 a correspondence with the British naturalist Alfred Russel Wallace about the introduction of species and natural selection shocked Darwin, as it included a paper Wallace had written describing natural selection. Wallace and Darwin decided to present their work together at a meeting of the Linnean Society on July 1, 1858, but, tragically, just before the meeting, Darwin's baby son died of scarlet fever so he was unable to attend. Darwin's health continued to decline, and his works were not completed.
After another 13 months in preparation, Darwin arranged for his book on natural selection to be published in 1859 through British publisher John Murray (1745-93). The book, On the Origin of Species by Means of Natural Selection or the Preservation of Favored Races in the Struggle of Life, proved to be immensely popular as soon as it was published, with all 1,250 copies sold before publication. The text caused great controversy, especially with various religious institutions. Even some of Darwin's former tutors at Cambridge, including Sedgwick and Henslow, opposed the ideas in his book. It was said that his theories went against the teachings of the church, although perhaps some of his colleagues had merely been afraid to speak out against the church. Some liberal clergymen, however, spoke in favor of Darwin's ideas, calling them noble conceptions of deity. Darwin did not discuss religious views in his works, though he was in fact a very religious man (before his daughter's death), but other scientists after him have used his work as a basis of their own theories that there is no room for religion in science.
Darwin continued to work in the fields of botany, geology, and zoology, publishing works including Variation in Plants and Animals under Domestication (1868), followed by The Descent of Man, and Selection in Relation to Sex (1871). In 1872 Darwin published Expression of the Emotions in Man and Animals, followed by several books on plants, including insectivorous plants, and an insightful volume on The Power of Movement in Plants, describing heli-otropism and phototropism in plants, published in 1880, and a final book on earthworms.
Darwin died on April 19, 1882, and was buried in a state funeral at Westminster Abbey, near Sir Issac Newton and John Herschel. Charles and Emma Darwin had 10 children, three of whom (Annie,
Mary, and Charles Waring) died in childhood, and seven of whom survived Charles. These included Charles Erasmus, Henrietta Emma, George Howard, Elizabeth Bessy, Francis, Leonard, and Horace.
See also evolution; historical geology; Lyell, Sir Charles.
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