Despite repeated bouts of illness during the last twenty-two years of his life, Darwin's work continued. Having published On the Origin of Species as an abstract of his theory, he pressed on with experiments, research and writing of his “big book”, covering humankind’s descent from earlier animals including evolution of society and of human mental abilities, as well as diversifying into innovative plant studies and explaining decorative beauty in wildlife.

Enquiries about insect pollination led in 1861 to novel studies of wild orchids, showing adaptation of their flowers to attract specific moths to each species and ensure cross fertilisation. Fertilisation of Orchids published in 1862 gave his first detailed demonstration of the power of natural selection, explaining the complex ecological relationships and making testable predictions. As his health declined, he lay on his sickbed in a room filled with inventive experiments to trace the movements of climbing plants.Admiring visitors included Ernst Haeckel, a zealous follower of Darwinismus in a translation favouring progressive evolution over natural selection.Wallace remained supportive, though he increasingly turned to Spiritualism.

The first part of Darwin's planned “big book”, Variation of Plants and Animals Under Domestication, grew to two huge volumes, forcing him to leave out human evolution and sexual selection. It sold briskly in 1868 despite its size, and was translated into many languages. He wrote most of a second section on natural selection, but it remained unpublished in his lifetime.

Punch's almanac for 1882, published shortly before Darwin’s death, depicts him amidst evolution from chaos to Victorian gentleman with the title Man Is But A Worm.Lyell had already popularised human prehistory, and Huxley had shown that anatomically humans are apes.With The Descent of Man, and Selection in Relation to Sex published in 1871, Darwin set out evidence from numerous sources that humans are animals, showing continuity of physical and mental attributes, and presented sexual selection to explain impractical animal features such as the peacock's plumage as well as human evolution of culture, differences between sexes, and physical and cultural racial characteristics, while emphasising that humans are all one species.His research using images was expanded in his 1872 book The Expression of the Emotions in Man and Animals, one of the first books to feature printed photographs, which discussed the evolution of human psychology and its continuity with the behaviour of animals. Both books proved very popular, and Darwin was impressed by the general assent with which his views had been received, remarking that "everybody is talking about it without being shocked."His conclusion was "that man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system–with all these exalted powers–Man still bears in his bodily frame the indelible stamp of his lowly origin.”

His evolution-related experiments and investigations culminated in books on the movement of climbing plants, insectivorous plants, the effects of cross and self fertilisation of plants, different forms of flowers on plants of the same species, and The Power of Movement in Plants. In his last book he returned to The Formation of Vegetable Mould through the Action of Worms.

He died in Downe, Kent, England, on 19 April 1882. He had expected to be buried in St Mary’s churchyard at Downe, but at the request of Darwin’s colleagues, William Spottiswoode (President of the Royal Society) arranged for Darwin to be given a state funeral and buried in Westminster Abbey, close to John Herschel and Isaac Newton.Only five non-royal personages were granted that honour of a UK state funeral during the 19th century.

The Darwins had ten children: two died in infancy, and Annie's death at the age of ten had a devastating effect on her parents. Charles was a devoted father and uncommonly attentive to his children.Whenever they fell ill he feared that they might have inherited weaknesses from inbreeding due to the close family ties he shared with his wife and cousin, Emma Wedgwood. He examined this topic in his writings, contrasting it with the advantages of crossing amongst many organisms. Despite his fears, most of the surviving children went on to have distinguished careers as notable members of the prominent Darwin-Wedgwood family.

Of his surviving children, George, Francis and Horace became Fellows of the Royal Society, distinguished as astronomer, botanist and civil engineer, respectively.His son Leonard, on the other hand, went on to be a soldier, politician, economist, eugenicist and mentor of the statistician and evolutionary biologist Ronald Fisher.

Darwin’s family tradition was nonconformist Unitarianism, while his father and grandfather were freethinkers, and his baptism and boarding school were Church of England.When going to Cambridge to become an Anglican clergyman, he did not doubt the literal truth of the Bible.He learnt John Herschel's science which, like William Paley’s natural theology, sought explanations in laws of nature rather than miracles and saw adaptation of species as evidence of design.On the Beagle voyage Darwin looked for "centres of creation" to explain distribution, and related the antlion found near kangaroos to distinct "periods of Creation".He remained quite orthodox and would quote the Bible as an authority on morality.

By his return he was critical of the Bible as history, and wondered why all religions should not be equally valid.In the next few years, while intensively speculating on geology and transmutation of species, he gave much thought to religion and openly discussed this with Emma, whose beliefs also came from intensive study and questioning.The theodicy of Paley and Thomas Malthus vindicated evils such as starvation as a result of a benevolent creator's laws which had an overall good effect. To Darwin, natural selection produced the good of adaptation but removed the need for design,and he could not see the work of an omnipotent deity in all the pain and suffering such as the ichneumon wasp paralysing caterpillars as live food for its eggs.He still viewed organisms as perfectly adapted, and On the Origin of Species reflects theological views. Though he thought of religion as a tribal survival strategy, Darwin still believed that God was the ultimate lawgiver.

Darwin continued to play a leading part in the parish work of the local church,but from around 1849 would go for a walk on Sundays while his family attended church.Though reticent about his religious views, in 1879 he responded that he had never been an atheist in the sense of denying the existence of a God, and that generally “an Agnostic would be the more correct description of my state of mind.”

The “Lady Hope Story”, published in 1915, claimed that Darwin had reverted back to Christianity on his sickbed. The claims were refuted by Darwin’s children and have been dismissed as false by historians.His last words were to his family, telling Emma "I am not the least afraid of death – Remember what a good wife you have been to me – Tell all my children to remember how good they have been to me", then as she laid down for a rest, he repeatedly told Henrietta and Francis "It's almost worth while to be sick to be nursed by you".
Darwin’s theories and writings, combined with Gregor Mendel’s genetics (the “modern synthesis”), form the basis of all modern biology.However, Darwin’s fame and popularity led to his name being associated with ideas and movements which at times had only an indirect relation to his writings, and sometimes went directly against his express comments.


For more details on this topic, see Eugenics.
Darwin was interested by his half-cousin Francis Galton's argument, introduced in 1865, that statistical analysis of heredity showed that moral and mental human traits could be inherited, and principles of animal breeding could apply to humans. In The Descent of Man Darwin noted that aiding the weak to survive and have families could lose the benefits of natural selection, but cautioned that withholding such aid would endanger the instinct of sympathy, "the noblest part of our nature", and factors such as education could be more important. When Galton suggested that publishing research could encourage intermarriage within a "caste" of "those who are naturally gifted", Darwin foresaw practical difficulties, and thought it "the sole feasible, yet I fear utopian, plan of procedure in improving the human race", preferring to simply publicise the importance of inheritance and leave decisions to individuals.

Galton named the field of study Eugenics in 1883, after Darwin’s death, and developed biometrics. Eugenics movements were widespread at a time when Darwin's natural selection was eclipsed by Mendelian genetics, and in some countries including Belgium, Brazil, Canada, Sweden and the United States, compulsory sterilisation laws were imposed. Following the use of Eugenics in Nazi Germany it has been largely abandoned throughout the world.

Taking descriptive ideas as moral and social justification creates the ethical is-ought problem. When Thomas Malthus argued that population growth beyond resources was ordained by God to get humans to work productively and show restraint in getting families, this was used in the 1830s to justify workhouses and laissez-faire economics.Evolution was seen as having social implications, and Herbert Spencer's 1851 book Social Statics based ideas of human freedom and individual liberties on his Lamarckian evolutionary theory.

Darwin's theory of evolution was a matter of explanation. He thought it "absurd to talk of one animal being higher than another" and saw evolution as having no goal, but soon after the Origin was published in 1859 critics derided his description of a struggle for existence as a Malthusian justification for the English industrial capitalism of the time. The term Darwinism was used for the evolutionary ideas of others, including Spencer's “survival of the fittest” as free-market progress, and Ernst Haeckel's racist ideas of human development. Darwin did not share the racism common at that time. He was strongly against slavery, against "ranking the so-called races of man as distinct species", and against ill-treatment of native people.

Writers used natural selection to argue for various, often contradictory, ideologies such as laissez-faire dog-eat dog capitalism, racism, warfare, colonialism and imperialism. However, Darwin's holistic view of nature included "dependence of one being on another", thus pacifists, socialists, liberal social reformers and anarchists such as Prince Peter Kropotkin stressed the value of co-operation over struggle within a species.Darwin himself insisted that social policy should not simply be guided by concepts of struggle and selection in nature.

The term “Social Darwinism” was used infrequently from around the 1890s, but became popular as a derogatory term in the 1940s when used by Richard Hofstadter to attack the laissez-faire conservatism of those like William Graham Sumner who opposed reform and socialism. Since then it has been used as a term of abuse by those opposed to what they think are the moral consequences of evolution.

During Darwin’s lifetime, many species and geographical features were given his name. An expanse of water adjoining the Beagle Channel was named Darwin Sound by Robert FitzRoy after Darwin’s prompt action, along with two or three of the men, saved them from being marooned on a nearby shore when a collapsing glacier caused a large wave that would have swept away their boats,and the nearby Mount Darwin in the Andes was named in celebration of Darwin’s 25th birthday.When the Beagle was surveying Australia in 1839, Darwin’s friend John Lort Stokes sighted a natural harbour which the ship’s captain Wickham named Port Darwin.The settlement of Palmerston founded there in 1869 was officially renamed Darwin in 1911. It became the capital city of Australia’s Northern Territory,which also boasts Charles Darwin University and Charles Darwin National Park.Darwin College, Cambridge, founded in 1964, was named in honour of the Darwin family, partially because they owned some of the land it was on.

Although related to American Emberizidae or Tanagers rather than finches, the group of species related to those Darwin found in the Galápagos Islands became popularly known as “Darwin's finches” following publication of David Lack's book of that name in 1947, fostering inaccurate legends about their significance to his work.

In 1992, Darwin was ranked #16 on Michael H. Hart’s list of the most influential figures in history.Darwin came fourth in the 100 Greatest Britons poll sponsored by the BBC and voted for by the public.In 2000 Darwin’s image appeared on the Bank of England ten pound note, replacing Charles Dickens. His impressive, luxuriant beard (which was reportedly difficult to forge) was said to be a contributory factor to the bank’s choice.

The Linnean Society of London has commemorated Darwin's achievements by the award of the Darwin-Wallace Medal since 1908.

In the Galápagos Islands, the Charles Darwin Foundation based at the Charles Darwin Research Station does research and conservation. To mark 2009 they are helping to reintroduce to Floreana Island (Charles Island) the specific mockingbird which first alerted Darwin to species being unique to islands. It was eradicated from the main island by European species, mainly rats and goats, but survived on two small islands nearby.

As a humorous celebration of evolution, the annual Darwin Award is bestowed on individuals who “improve our gene pool by removing themselves from it.”

Numerous biographies of Darwin have been written, and the 1980 biographical novel The Origin by Irving Stone gives a closely researched fictional account of Darwin’s life from the age of 22 onwards.

Two pound coin commemorating Darwin's birth and publication of On the Origin of Species.Darwin Day has become an annual celebration, and the bicentenary of Darwin's birth and the 150th anniversary of the publication of On the Origin of Species are being celebrated by events and publications around the world.[161] The Darwin exhibition, after opening at the American Museum of Natural History in New York City in 2006, was shown at the Museum of Science, Boston, the Field Museum in Chicago, the Royal Ontario Museum in Toronto,then from 14 November 2008 to 19 April 2009 in the Natural History Museum, London, as part of the Darwin200 programme of events across the United Kingdom.The University of Cambridge features a festival in July 2009.His birthplace is celebrating with "Darwin's Shrewsbury 2009 Festival" events during the year.

In the United Kingdom a special commemorative issue of the two pound coin shows a portrait of Darwin facing a chimpanzee surrounded by the inscription 1809 DARWIN 2009, with the edge inscription ON THE ORIGIN OF SPECIES 1859. Collector versions of the coin will be released at a premium, and during the year the coins will be available from banks and post offices at face value.

In September 2008, the Church of England issued an article saying that the 200th anniversary of his birth was a fitting time to apologise to Darwin "for misunderstanding you and, by getting our first reaction wrong, encouraging others to misunderstand you still".

Darwin was a prolific writer. Even without publication of his works on evolution, he would have had a considerable reputation as the author of The Voyage of the Beagle, as a geologist who had published extensively on South America and had solved the puzzle of the formation of coral atolls, and as a biologist who had published the definitive work on barnacles. While The Origin of Species dominates perceptions of his work, The Descent of Man, and Selection in Relation to Sex and The Expression of Emotions in Man and Animals had considerable impact, and his books on plants including The Power of Movement in Plants were innovative studies of great importance, as was his final work on The Formation of Vegetable Mould Through the Action of Worms.

Charles Darwin is denoted by the author abbreviation Darwin when citing a botanical name.