Between 1860 and 1868, the life and work of Charles Darwin from Orchids to Variation continued with research and experimentation on evolution, carrying out tedious work to provide evidence of the extent of natural variation enabling artificial selection. He was repeatedly held up by his illness, and continued to find relaxation and interest in the study of plants. His studies of insect pollination led to publication of his book Fertilisation of Orchids as 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.

Darwinism became a movement covering a wide range of evolutionary ideas. In 1863 Lyell's Geological Evidences of the Antiquity of Man popularised prehistory, though his caution on evolution disappointed Darwin. Weeks later Huxley's Evidence as to Man's Place in Nature showed that anatomically, humans are apes, then The Naturalist on the River Amazons by Henry Walter Bates provided empirical evidence of natural selection. Lobbying brought Darwin Britain's highest scientific honour, the Royal Society's Copley Medal, awarded on 3 November 1864. That day, Huxley held the first meeting of what became the influential X Club devoted to "science, pure and free, untrammelled by religious dogmas".

Admiring visitors included Ernst Haeckel, a zealous follower of "Darwinismus" in a translation favouring progressive evolution over natural selection.Darwin Correspondence Project: Introduction to the Correspondence of Charles Darwin, Volume 14. Cambridge University Press. Retrieved on 28 November 2008 Wallace remained supportive, though he increasingly turned to Spiritualism..

The first part of Darwin's planned "big book", The Variation of Animals and Plants 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. Darwin's work on the Descent of Man and Emotions followed after this publication.

Background Darwin's ideas developed rapidly from the return in 1836 of The Voyage of the Beagle. By December 1838 he had developed the principles of his theory, but was conscious of the need to answer all likely objections before publishing. While he continued with research, he had an immense amount of work in hand analysing and publishing findings from the Beagle expedition, and was repeatedly delayed by illness.

Natural history at that time was dominated by clerical naturalists, whose income came from the Established Church of England, and who saw their science as revealing God's plan. Darwin found two close allies: the young botanist Joseph Dalton Hooker and the ambitious naturalist Thomas Huxley who lacked the family wealth or contacts to find a career and joined a progressive group looking to make science a profession, freed from the clerics. Darwin's correspondent Wallace arrived independently at his own version of the theory, which brought an early announcement of the theory and the publication of On the Origin of Species through Natural Selection in 1859.

This brought a storm of argument. Many naturalists attacked what they saw as an assault on established beliefs about the natural world, and perhaps the ideological foundations of the British social order, while liberal theologians and a new generation of scientists welcomed the theory. Charles Lyell and Hooker, as well as Asa Gray in America, gave support despite difficulty in coming to terms with natural selection and man's descent from animals. Huxley's interest in aggressively attacking the scientific establishment earned him the moniker "Darwin's bulldog" in a ferocious dispute with the leading anatomist Richard Owen as to whether the anatomy of brain structure was consistent with humans and apes having shared ancestry. The campaign was devastatingly successful for the Darwinian cause and brought new recruits.

Ape-men Lyell was troubled both by Huxley's belligerence and by the question of ape ancestry, but got little sympathy from Darwin who teased him in January 1860: "Our ancestor was an animal which breathed water, had a swim-bladder, a great swimming tail, an imperfect skull & undoubtedly was an hermaphrodite! Here is a pleasant genealogy for mankind." In April Lyell noted thoughts on humanity, and Darwin commented that "to me it would be an infinite satisfaction to believe that mankind will progress to such a pitch, that we shd. be looked back at as mere Barbarians." Huxley was busy attacking the old theory of divine providence as "anthropomorphism" and promoting the new Darwinian orthodoxy of "the passionless impersonality of the unknown and unknowable". He told Lyell that the range of brain sizes between people was greater than the difference between small-brained people and gorillas, and "Under these circumstances it would certainly be well to let go the head (as a way of distinguishing species) though I am afraid it does not mend matters much to lay hold of the foot."

Lyell began work on a book examining human origins. He toured archaeological sites in Britain and France, examining such evidence as the pre-glacial stone scrapers Hugh Falconer had found in a cave at Brixham in Devon in 1858 and flint tools in a Bedford, Bedfordshire, gravel pit. After touring the Abbeville flint site in France in 1859, Lyell announced that he had overcome thirty years of denial of such antiquity and accepted that ancient man pre-dated the ice age. A delighted Darwin responded in April 1861 "It is grand. What a fine long pedigree you have given the Human Race!" Lyell questioned Huxley about the Neanderthal fossil found near Düsseldorf and described by Hermann Schaaffhausen in 1858 which Huxley examined at the College of Surgeons in London. Lyell still, however, remained deeply critical of Darwin's idea of natural selection.

In the spring of 1861 John Stevens Henslow, the botany professor whose natural history course Charles had joined thirty years earlier who was also Hooker's father-in-law, lay dying of heart disease. Darwin's own health was precarious, and he had recently suffered 24 hours of vomiting after the excitement of a few minutes of speaking at the Linnean Society. He agonised about visiting the man who had made the Beagle trip possible and had given him much support since, and on 23 April told Hooker that "the agitation would cause me probably to arrive utterly prostrated." He had "never felt my weakness a greater evil." Henslow died on 18 May.

Darwin was well into his work on domestication, obtaining skeletons of fowl and animals, borrowing specimens or stewing pigeons he had bred and rabbits he had requested, "I want it dead for the skeleton, not knocked on the head". This would eventually lead to his book The Variation of Animals and Plants Under Domestication.

He continued to suffer from illness and worries about the health of his children, and felt "incessant anxiety" about his daughter Henrietta. She had suffered a typhoid infection the previous month, and was an invalid at only 18, close to death and needing three attendants round the clock. Emma Darwin was used to nursing, but was at her wit's end: "I have succeeded pretty well in teaching myself not to give way to despondency, [but can] only live from day to day." She wrote another touching letter to Charles, saying the "only relief [was to take] affliction as from God's hand [and] try to believe that all suffering & illness is meant to help us to exalt our minds & look forward with hope to a future state... When I see your patience, deep compassion for others, self command & above all gratitude for the smallest thing done to help you I cannot help longing that these precious feelings should be offered to Heaven for the sake of your daily happiness... It is feeling & not reasoning that drives one to prayer." Charles wrote "God Bless you" at the bottom of the note.

Lyell attended Huxley's continuing working-men's lectures, and was "astonished at the attentiveness and magnitude of the audience...[who would] devour any amount of your anthropoid ape questions". Human origins had been taboo to the scientific élite, but had long been featured in the radical press and the secularist Reasoner was currently running a series about evolution to combat "Theological Theories of the Origin of Man" with information about human fossils and Darwin's book. Huxley was tailoring his lectures to bring Darwinism to this wider constituency, saying that "Brought face to face [with chimpanzees or apes] these blurred copies of himself, the least thoughtful of men is conscious of a certain shock... It is as if Nature herself has foreseen the arrogance of man, and with Roman severity had provided that his intellect by its very triumphs, should call into prominence the slaves, admonishing the conqueror that he is but dust." Man might have come from the brutes, but "he is assuredly not of them... [man is not] degraded from his high estate [by descent from a] bestial savage,... [but] once escaped from the blinding influences of traditional prejudice, will find in the lowly stock whence Man has sprung, the best evidence of the splendour of his capacities; and will discern in his long progress through the Past, a reasonable ground of faith in his attainment of a nobler future." This was Darwinism supporting the creed of working class self-improvement.

Orchids

For July and August 1861 they took their daughter Henrietta to the seaside village of Torquay. Darwin was diverted by spending hours considering the variety of wild orchids to be found along the shore, continuing an interest in insect pollination dating back to the late 1830s when on the recommendation of Robert Brown he had read Christian Konrad Sprengel on the subject. He wrote a brief paper on the topic. On returning home he looked for these plants near Downe, and found a beautiful spot teeming with orchids which his family named "Orchid Bank". His requests to the wealthy enthusiasts who had taken up growing rare orchids brought large numbers of specimens. These would be a test of his theory: Huxley had once asked "Who has ever dreamed of finding an utilitarian purpose in the forms and colours of flowers?"

He explored the intricacies of how the petals guided specific bees or moths, and found that what had been thought to be three different genera of flowers growing on the same plant (a mysteriously monstrous specimen that puzzled the Linnean Society) were actually the male, female and hermaphrodite forms of the orchid Catasetum. This unusual plant, Darwin discovered, fired arrows with a sticky pollen head as the insects brushed past – to which Hooker responded "Do you really think I can believe all that!" In this, Darwin followed his grandfather Erasmus Darwin in exploring the sex life of plants, he analysed how parts of the plants were "homologous", having evolved from an original structure to meet different functions in different species. He persuaded John Murray that this would be a fashionable book to publish, but his illness returned, causing delay.