[23] Darwin spent the summer of 1825 as an apprentice doctor, helping his father treat the poor of Shropshire, before going to the well-regarded University of Edinburgh Medical School with his brother Erasmus in October 1825.
[26] He assisted Robert Edmond Grant's investigations of the anatomy and life cycle of marine invertebrates in the Firth of Forth, and on 27 March 1827 presented at the Plinian his own discovery that black spores found in oyster shells were the eggs of a skate leech.
He returned home on 29 August to find a letter from Henslow proposing him as a suitable (if unfinished) naturalist for a self-funded supernumerary place on HMS Beagle with captain Robert FitzRoy, a position for a gentleman rather than "a mere collector".
As FitzRoy had intended, Darwin spent most of that time on land investigating geology and making natural history collections, while HMS Beagle surveyed and charted coasts.
[54] On rides with gauchos into the interior to explore geology and collect more fossils, Darwin gained social, political and anthropological insights into both native and colonial people at a time of revolution, and learnt that two types of rhea had separate but overlapping territories.
Owen's surprising results included other gigantic extinct ground sloths as well as the Megatherium Darwin had identified, a near complete skeleton of the unknown Scelidotherium and a hippopotamus-sized rodent-like skull named Toxodon resembling a giant capybara.
Questions of how to combine his diary into the Narrative were resolved at the end of the month when FitzRoy accepted Broderip's advice to make it a separate volume, and Darwin began work on his Journal and Remarks.
[84] Early in March, Darwin moved to London to be near this work, joining Lyell's social circle of scientists and experts such as Charles Babbage,[85] who described God as a programmer of laws.
Transmutation was anathema to Anglicans defending social order,[86] but reputable scientists openly discussed the subject, and there was wide interest in John Herschel's letter praising Lyell's approach as a way to find a natural cause of the origin of new species.
His uncle Josiah pointed out an area of ground where cinders had disappeared under loam and suggested that this might have been the work of earthworms, inspiring "a new & important theory" on their role in soil formation, which Darwin presented at the Geological Society on 1 November 1837.
[94] Despite the grind of writing and editing the Beagle reports, Darwin made remarkable progress on transmutation, taking every opportunity to question expert naturalists and, unconventionally, people with practical experience in selective breeding such as farmers and pigeon fanciers.
For the rest of his life, he was repeatedly incapacitated with episodes of stomach pains, vomiting, severe boils, palpitations, trembling and other symptoms, particularly during times of stress, such as attending meetings or making social visits.
She accepted, then in exchanges of loving letters showed how she valued his openness in sharing their differences, while expressing her strong Unitarian beliefs and concerns that his honest doubts might separate them in the afterlife.
[110] His research included extensive experimental selective breeding of plants and animals, finding evidence that species were not fixed and investigating many detailed ideas to refine and substantiate his theory.
[150] Though Darwin's illness kept him away from the public debates, he eagerly scrutinised the scientific response, commenting on press cuttings, reviews, articles, satires and caricatures, and corresponded on it with colleagues worldwide.
Darwin's old Cambridge tutors Sedgwick and Henslow dismissed the ideas, but liberal clergymen interpreted natural selection as an instrument of God's design, with the cleric Charles Kingsley seeing it as "just as noble a conception of Deity".
In it, Baden Powell argued that miracles broke God's laws, so belief in them was atheistic, and praised "Mr Darwin's masterly volume [supporting] the grand principle of the self-evolving powers of nature".
Joseph Hooker argued strongly for Darwin, and Thomas Huxley's legendary retort, that he would rather be descended from an ape than a man who misused his gifts, came to symbolise a triumph of science over religion.
[167] The Origin of Species was translated into many languages, becoming a staple scientific text attracting thoughtful attention from all walks of life, including the "working men" who flocked to Huxley's lectures.
He covered human descent from earlier animals, including the evolution of society and of mental abilities, as well as explaining decorative beauty in wildlife and diversifying into innovative plant studies.
[178] According to an editorial in Nature journal: "Although Charles Darwin opposed slavery and proposed that humans have a common ancestor, he also advocated a hierarchy of races, with white people higher than others.
To Darwin, natural selection produced the good of adaptation but removed the need for design,[200] 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.
Around twenty years later, racism became a feature of British society,[25][209] but Darwin remained strongly against slavery, against "ranking the so-called races of man as distinct species", and against ill-treatment of native people.
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.
Thomas Malthus had 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.
However, Darwin's holistic view of nature included "dependence of one being on another"; thus pacifists, socialists, liberal social reformers and anarchists such as Peter Kropotkin stressed the value of cooperation over struggle within a species.
FitzRoy's diary during the ascent of the River Santa Cruz in Patagonia recorded his opinion that the plains were raised beaches, but on return, newly married to a very religious lady, he recanted these ideas.
"[236] and in the concluding chapter: "The framework of bones being the same in the hand of a man, wing of a bat, fin of the porpoise, and leg of the horse … at once explain themselves on the theory of descent with slow and slight successive modifications.
^ David Quammen writes of his "theory that [Darwin] turned to these arcane botanical studies – producing more than one book that was solidly empirical, discreetly evolutionary, yet a 'horrid bore' – at least partly so that the clamorous controversialists, fighting about apes and angels and souls, would leave him... alone".
David Quammen, "The Brilliant Plodder" (review of Ken Thompson, Darwin's Most Wonderful Plants: A Tour of His Botanical Legacy, University of Chicago Press, 255 pp.