Inception of Darwin's theory
The inception of Darwin's theory occurred during an intensively busy period which began when Charles Darwin returned from the survey voyage of the Beagle, with his reputation as a fossil collector and geologist already established. He was given an allowance from his father to become a gentleman naturalist rather than a clergyman, and his first tasks were to find suitable experts to describe his collections, write out his Journal and Remarks, and present papers on his findings to the Geological Society of London.
At Darwin's geological début, the anatomist Richard Owen's reports on the fossils showed that extinct species were related to current species in the same locality, and the ornithologist John Gould showed that bird specimens from the Galápagos Islands were of distinct species related to places, not just varieties. These points convinced Darwin that transmutation of species must be occurring, and in his Red Notebook he jotted down his first evolutionary ideas. He began specific transmutation notebooks with speculations on variation in offspring "to adapt & alter the race to changing world", and sketched an "irregularly branched" genealogical branching of a single evolutionary tree.
Animal observations of an orangutan at the zoo showed how human its expressions looked, confirming his thoughts from the Beagle voyage that there was little gulf between man and animals. He investigated animal breeding and found parallels to nature removing runts and keeping the fit, with farmers deliberately selecting breeding animals so that through "a thousand intermediate forms" their descendants were significantly changed. His speculations on instincts and mental traits suggested habits, beliefs and facial expressions having evolved, and considered the social implications. While this was his "prime hobby", he was struggling with an immense workload and began suffering from his illness. Having taken a break from work, his thoughts of marriage turned to his cousin Emma Wedgwood.
Reading about Malthus and natural law led him to apply to his search for the Creator's laws Malthusian logic of social thinking of struggle for survival with no handouts, and he "had at last got a theory by which to work". He proposed to Emma, and was accepted. In his theory he compared breeders selecting traits to natural selection from variants thrown up by "chance", and continued to look to the countryside for supporting information. On 24 January 1839 he was elected as Fellow of the Royal Society, and on the 29th married Emma. The development of Darwin's theory followed.
After his early life in a Unitarian family, Charles Darwin developed his interest in natural history. At Edinburgh University his work as a student of Robert Edmund Grant involved him in pioneering investigations of the ideas of Jean-Baptiste Lamarck and Erasmus Darwin on homology showing common descent, but he also saw how controversial and troubling such theories were. Robert Jameson's course taught Darwin stratigraphic geology, and closed with lectures on the "Origin of the Species of Animals". At Christ's College, Cambridge to qualify as an Anglican clergyman, Darwin became passionate about beetle collecting, then shone in John Stevens Henslow's botany course. He was convinced by Paley's Natural Theology which set out the Teleological argument that complexity of "design" in nature proved God's role as Creator, and by the views of Paley and John Herschel that creation was by laws which science could discover, not by intermittent miracles. The geology course of Adam Sedgwick and summer work mapping strata in Wales emphasised that life on earth went back over eons of time.
Then on his voyage on the Beagle Darwin became convinced by Charles Lyell's uniformitarian theory of gradual geological process, and puzzled over how various theories of creation fitted the evidence he saw.
In the third edition of On the Origin of Species Darwin provided a historical sketch of his predecessors in writing of descent with modification or natural selection, including those who he had only learned of after the 1859 publication of The Origin. His account essentially deals with 19th-century authors; "Passing over authors from the classical period to that of Buffon, with whose writings I am not familiar, Lamarck was the first man whose conclusions on this subject excited much attention." However, in a footnote he remarks on how his grandfather, Dr. Erasmus Darwin, Goethe and Geoffroy Saint Hilaire came to the same conclusion on the origin of species in the years 1794-5, anticipating Lamarck.
There is no direct evidence linking Darwin to Benjamin Franklin's treatise "Observations Concerning the Increase of Mankind, Peopling of Countries, etc.." However, Franklin was a friend and colleague of both Erasmus and Robert Darwin, and it has been suggested that this work may have influenced Darwin's study of Malthus' belief on the relationship between population and subsistence.
Return to celebrity and science 
When the Beagle returned, Darwin was quick to take the coach home and arrived at the family home of The Mount House in Shrewsbury, Shropshire, late at night on 4 October 1836. He went straight to bed, then greeted his family at breakfast and began catching up with news of his family and of the country: "all England appears changed". The Reform Bill had brought what the Tory Duke of Wellington described as a shift in power from decent Tory Anglicans to Whig manufacturers, shopkeepers and atheists. Everyone was discussing the writings of Thomas Malthus on population outstripping resources as the New Poor Law described by opponents as "a Malthusian bill designed to force the poor to emigrate, to work for lower wages, to live on a coarser sort of food" brought the construction of workhouses in the southern counties despite riots and arson. The government had not yet dared introduce these measures to London and the industrial north, and recession was bringing threats of mass unemployment.
Darwin wrote to Henslow that he was still "giddy with joy & confusion... I want your advice on so many points, indeed I am in the clouds" and on 15 October went on to Cambridge to get advice from Henslow and Sedgwick on the task of organising the description and cataloguing of his collections accumulated from the Beagle expedition. Henslow took on the plants, and Darwin was given introductions to the best London naturalists with a warning that they would already be busy with other work.
Charles went on to stay with his brother Erasmus in London, near the scientific institutions which were in the throes of renovation, while the city itself was being torn up to install new sewers and gas lighting. He went round the British Museum, the Royal College of Surgeons, the Linnean, the Zoological Society and Geological Society, trying to get the experts to take on his collections. Henslow had already established his former pupil's reputation during the Beagle expedition by giving selected naturalists access to fossil specimens sent back as well as having Darwin's geological writings privately printed for distribution. Darwin went "in most exciting dissipation amongst the Dons in science", and as Charles Bunbury reported, "[he] seems to be a universal collector" finding new species "to the surprise of all the big wigs". While geologists were quick to take on the rock samples, zoologists already had more specimens arriving than they could deal with. Their institutions were in turmoil as democrats argued for reforms replacing the aristocratic amateurs with professional salaried scientists as in the French research institutes. At the Zoological Society the reformers were led by Darwin's tutor from Edinburgh days, Robert Edmund Grant. Darwin now had an allowance plus stocks from his father, bringing him around £400 per year, and his sympathies were with the amateur clerical "Dons in science" of Cambridge.
Owen and fossils 
The geologist Charles Lyell invited Darwin to dinner on 29 October 1836. Over dinner Lyell listened eagerly to Darwin's stories (which supported Lyell's uniformitarianism) and introduced him to Richard Owen and William Broderip, Tories who had just been involved in voting Grant out of a position at the Zoological Society. Owen was rapidly ousting Grant as the country's leading anatomist. Darwin went to visit him at his Royal College of Surgeons, and Owen agreed to work on some animal specimens in spirits and the fossil bones. Owen shared Darwin's enthusiasm. He was a proponent of German ideas of "organising energy" and vehemently opposed to Grant's evolution. At around this time Grant was one the few to volunteer his help with cataloguing the collection. Darwin turned down the offer, not wanting to be associated with a disreputable radical who denounced his Cambridge friends.
On 12 November Darwin visited his Wedgwood relatives at Maer Hall and they encouraged him to publish a book of his travels based on his diary, an idea his sisters picked up when he visited his home.
On 2 December he returned to London and began finding takers for his specimens, with Thomas Bell and the Revd. William Buckland interested in the reptiles. Darwin's reputation was being made by the giant mammal fossils. Owen's first surprising revelation was that a hippopotamus sized fossil skull 2 feet 4 inches (710 mm) long which Darwin had bought for about two shillings near Mercedes while on a "galloping" trip 120 miles (190 km) from Montevideo was of an extinct rodent-like creature resembling a giant capybara, which Owen named Toxodon. Darwin wrote to his sister Caroline that "[the fossils] are turning out great treasures" and of the Toxodon, "There is another head, as large as a Rhinoceros which as far as they can guess, must have been a gnawing animal. Conceive a Rat or a Hare of such a size— What famous Cats they ought to have had in those days!" The College of Surgeons distributed casts of the fossils to the major scientific institutions.
Darwin paid a visit to his brother Eras's lady friend the literary Whig Miss Harriet Martineau who had strong views on egalitarianism and whose writings had popularised the ideas of Thomas Malthus. Around this time, she was writing her Society in America which included discussion of the geological "process of world making" that she had seen on her visit to the Niagara Falls. He sat there for almost an hour. "She was very agreeable and managed to talk on a most wonderful number of subjects, considering the limited time. I was astonished to find how little ugly she is, but as it appears to me, she is overwhelmed with her own projects, her own thoughts and own abilities. Erasmus palliated all this, by maintaining one ought not to look at her as a woman." In her autobiography, she later recalled Charles as being "simple, childlike, painstaking, effective".
Unhappy with life in a “dirty odious London” he returned to Cambridge on 13 December then wrote his first paper, showing that the Chilean coast and the South American land-mass was rising slowly, and discussed his ideas with Lyell. To Lyell's delight, Darwin went further in balancing the rising continent with sinking mountains forming the basis of coral atolls. Darwin briefly returned to London to read his paper to the Geological Society on 4 January 1837. Despite Darwin's nerves about his début, the talk was so well received that he felt “like a peacock admiring his tail”.
While the birds seemed almost an afterthought the ornithologist John Gould took them on and was quick to notice the significance of specimens from the Galápagos Islands. He startlingly revealed at the next meeting on 10 January that what Darwin had taken to be wrens, blackbirds and slightly differing finches were "a series of ground finches which are so peculiar" as to form "an entirely new group" of 11 species. The story of what we now call "Darwin's finches" was covered by the daily newspapers, though Darwin was in Cambridge and did not get details at this stage. In the minutes of the meeting the number was extended to 12 species.
Owen was finding unexpected relationships from the fossils: the batch included the horse sized Scelidotherium which appeared to be closely allied to the anteater, a gigantic ground sloth, and an ox-sized armoured armadillo which he called Glyptodon. The Patagonian spine and leg bones from Port St Julian which Darwin had thought might be from a Mastodon were apparently from a gigantic guanaco or Llama, or perhaps camel, which Owen named Macrauchenia. Lyell saw a "law of succession" with mammals being replaced by their own kind on each continent, and on 17 February used his presidential address at the Geographical Society to present Owen's findings to date on Darwin's fossils, pointing out this inference that extinct species were related to current species in the same locality. He invited Darwin to come along, and the speech drew Darwin's attention to the question of why past and present species in one place should be so closely related. At the same meeting Darwin was elected to the Council of the Society. For Lyell this was "a glorious addition to my society of geologists", gentlemen (and amateurs of independent means) with duty only to scientific integrity, social stability and responsible religion, for Darwin it meant joining the respectable élite of eminent geologists developing a science dealing with the age of the earth and the Days of Creation.
Darwin had already been invited by FitzRoy to contribute his Journal, based on his field notes, as the natural history section of the captain's account of the Beagle's voyage, and this ended up keeping him fully occupied from 13 March to the end of September. He also plunged into writing a book on South American Geology, putting his and Lyell's ideas forward against the cataclysmic explanation of mountain formation Alcide d'Orbigny was promoting in a multi-volume account of the continent begun two years previously.
To supervise his collections Darwin had to return to London, and on Lyell's advice he planned to arrive on Friday 3 March 1837, in time for one of Charles Babbage's Saturday parties, talking shops about the latest developments "brilliantly attended by fashionable ladies, as well as literary and scientific gents" and "a good mixture of pretty women", bankers and politicians, where Babbage promoted such projects as his mechanical computer. At first Darwin stayed with Eras, in his journal written up later he put his date of moving as 6 March 1837. On the 13th he moved to nearby lodgings, joining Eras's circle of friends including Martineau and Hensleigh and enjoying his intimate dinner parties with guests such as Lyell, Babbage and Thomas Carlyle.
In their first meeting to discuss his detailed findings, Gould told Darwin that the Galápagos mockingbirds from different islands were separate species, not just varieties, and the finch group included the “wrens”. The two rheas were also distinct species, and on 14 March Gould's announcement of this finding to the Zoological Society of London was accompanied by Darwin, who presented a paper on how distribution of the two species of rheas changed going southwards.
Darwin was concerned to make sure that his theorising, whether published or private, fully complied with the accepted scientific methodology of his peers. John Herschel and William Whewell were recognised as the leading authorities on science, and were valuable connections for him.
Scientific circles were buzzing with ideas of natural theology. In a letter to Lyell, Herschel had written of “that mystery of mysteries, the replacement of extinct species by others”. This was circulated and widely discussed, with scientists sharing Herschel's approach of looking for an answer through laws of nature and rejecting ad hoc miracles as an explanation. Charles Babbage described God as a programmer of such laws. Darwin's freethinking brother Erasmus was part of this Whig circle and a close friend of the writer Harriet Martineau who promoted the Malthusianism underlying the controversial Whig Poor Law reforms to stop welfare from causing overpopulation and more poverty, which were then being implemented piecemeal in the face of opposition to the new poorhouses. As a Unitarian she welcomed the radical implications of transmutation of species, which was promoted by Grant and some medical men but anathema to Darwin's Anglican friends who saw it as a threat to the social order. Transmutation threatened the essential distinction between man and beast, and implied progressive improvement with the implication that the lower orders could aspire to the privileges of their aristocratic overlords.
The medical establishment controlling the London teaching hospitals, including the Royal College of Surgeons, was restricted to Anglicans and dominated by the aristocracy who saw perfect animal design as proof a natural theology supporting their ideas of God-given rank and privilege. Since the 1820s large numbers of private medical schools joined by the new had introduced the "philosophical anatomy" of Geoffroy Saint-Hilaire based on unity of plan compatible with the transmutation of species, implying ideas of progressive improvement and hence radical support for democracy. This anatomy had already spread from Paris to the medical schools of Edinburgh, and the new London schools attracted Scots including Grant. Numerous journals new promoted these radical ideas, including Thomas Wakley's The Lancet started in 1823 with support from William Cobbett and William Lawrence, whose 1819 publication of evolutionary ideas had been prosecuted for blasphemy. In response, the medical establishment gave support to the idealist biology of Joseph Henry Green and his younger protégé Richard Owen, based on the vitalism of German Naturphilosophie and Platonic idealism which held that anatomical forms were "archetypes" in the Divine mind, imposed through "descensive" powers of delegation of divine authority in accordance with traditional hierarchies.
Red notebook 
By mid-March, Darwin was speculating in his Red Notebook on the possibility that "one species does change into another" to explain the geographical distribution of living species such as the rheas, and extinct ones such as Macrauchenia which resembled a giant version of the modern guanacos that Darwin had hunted in the same area of Patagonia. Darwin speculated as to why the territories of the rheas overlapped without intermediate species, wondering if mutations (known then as "monsters" or "freaks") "present an analogy to production of species". His Cambridge tutor Adam Sedgwick had described those promoting similar ideas as "infidel naturalists..[adopting] false theories". Even for Lyell, this was a heresy which implied ape ancestry, destroying mankind's "high estate".
Darwin was more open to new speculation. He had seen the bestial life of the natives of Tierra del Fuego, apparently happy in their harsh environment, and Jemmy Button's reversion to savagery. To him the need was to explain how both Fuegians and civilised Europeans could be "essentially the same creatures" from the hand of the same Creator. At the Geographical Society meeting on 2 May 1837, when Darwin read his next paper on the Pampas, the first discoveries of ancient fossil monkeys were announced. Lyell uncomfortably joked that from "Lamarck's view" this gave a long time "for their tails to wear off", but Darwin was beginning to look at these "wonderful" fossils in an evolutionary light.
At their frequent meetings, Owen argued that intrinsic "organising energy" in the "embryonic germ" set the lifespan of the species and precluded transmutation. The botanist Robert Brown showed Darwin a different concept, of "swarming atoms" inside the germ, allowing nature's self development. Embarrassed by his lack of labels for his finch specimens, he examined FitzRoy's in the British Museum and contacted seamen including Syms Covington for their collections. From this he was able to relate the finches to separate islands, with distinct species on each island. As well as pressing on with his Journal, he started an ambitious project to get the expert reports on his collection published as a multi-volume Zoology of the Voyage of H.M.S. Beagle. A search for sponsorship was answered when Henslow used his contacts with the Chancellor of the Exchequer Thomas Spring Rice to arrange a Treasury grant of £1,000, a sum equivalent to about £75,000 in present day terms.
During the Beagle voyage Darwin had noted the distribution of the two species of Galápagos iguanas and suspected that "this genus, the species of which are so well adapted to their respective localities, is peculiar to this group of Isds." He had identified the sea iguanas from a book on board as having been named Amblyrhyncus Cristatus by Bell from a specimen which had arrived in Mexico, probably found on the Pacific shore. In June he gave this information to William Buckland. As the Victorian era began, Darwin pressed on with writing his Journal, and in August 1837 began correcting printer's proofs.
Transmutation notebooks 
In mid-July 1837 Darwin began a notebook on "transmutation of Species", his "B" notebook, having been "greatly struck from about month of previous March on character of S. American fossils — & species on Galapagos Archipelago. — These facts origin (especially latter) of all my views." The title page was headed Zoönomia, referring to his grandfather's evolutionary ideas.
He scribbled down a framework for his speculations, jotting down thoughts on the lifespan of individuals and of species, including Richard Owen's idea that complexity of a species was inversely related to its life span. Darwin thought about reproduction, with asexual reproduction resulting in copies of the original, but sexual reproduction producing variation in the offspring which made it possible "to adapt & alter the race to changing world". This could explain the divergence from a common ancestor of Galápagos tortoises and mockingbirds, and of the rheas which remained distinct species with their overlapping territories. He sketched branching descent, then a genealogical branching of a single evolutionary tree, in which "It is absurd to talk of one animal being higher than another". He was thinking of life as arising only once and discarding the independent lineages progressing to higher forms as proposed by Lamarck and Grant as well as rejecting Lamarck's gradual progression in favour of what Darwin called "inosculation", a clear distinction between even the most closely related species. Still influenced by Paley, he assumed that variants emerged perfect, and developed the hypothesis that, for example, where every island in the Galápagos Archipelago had its own kind of tortoise, these had originated from a single tortoise species and had adapted to life on the different islands in different ways. Thinking of how ancestors could have spread to islands, he noted possible experiments.
Darwin thought that the possibility of common ancestry could not be denied when such strange forms as the platypus existed. He believed at that time that the Creator used laws to create, and felt this was shown by the unique plants and animals on the Galápagos islands sharing features with mainland American species, while wandering birds such as sandpipers were unchanged. A similar relationship in time was shown by the extinct armoured giant Glyptodon resembling the modern South American armadillo. He considered that the way that astronomers once thought that God ordered the movement of individual planets was comparable to individual creation of species in particular countries, but divine powers were "much more simple & sublime" in creating the first animals so that species then arose by "the fixed laws of generation". A hypothesis of "fresh creations" was "mere assumption, it explains nothing further".
Under pressure with organising Zoology and correcting proofs of his Journal which had to have the introduction revised when FitzRoy complained that he was "astonished at the total omission of any notice of the officers" for their help, Darwin's health suffered. On 20 September 1837 he suffered "an uncomfortable palpitation of the heart". His doctors advised him "strongly to knock off all work" and leave for the country. Two days later he went to Maer Hall, the Wedgwood's home, for a month of recuperation. His relations wore him out with questions about gaucho life. His invalid aunt was being cared for by the as yet unmarried Emma, and his uncle Jos pointed out an area of ground where cinders had disappeared under loam which Jos though might have been the work of earthworms. Darwin returned to London on 21 October and on 1 November gave a talk on the role of earthworms in soil formation to the Geological Society, a mundane subject which to them may have seemed eccentric. William Buckland subsequently recommended Darwin's paper for publication, praising it as "a new & important theory to explain Phenomena of universal occurrence on the surface of the Earth—in fact a new Geological Power", while rightly rejecting Darwin's suggestion that chalkland could have been formed in a similar way.
Darwin's notebooks developed an essentially materialist and deterministic view of human beings, with the conclusions that freewill was an illusion and the brain was mechanistic. He had avoided taking on official posts which would take valuable time, turning down William Whewell's request that he become Secretary of the Geological Society with excuses including "anything which flurries me completely knocks me up afterwards and brings on a bad palpitation of the heart", but by March 1838 he accepted the post. On 7 March he read to the Society his longest paper yet, which explained the earthquake he had witnessed at Concepción, Chile, in terms of gradual crustal movements, to the delight of Lyell. Despite hours of practice "I was so nervous at first, I somehow could see nothing all around me, & felt as if my body was gone, & only my head left." At the same time Darwin was privately scorning Whewell's faith in a human-centred universe being perfectly adapted to man and writing of "my theory" which he thought "would give zest to recent & Fossil Comparative Anatomy", transforming the "whole metaphysics".
Darwin's ideas fitted with the radical Unitarianism of his brother Erasmus's circle including Harriet Martineau, but were heretical to his Anglican friends in the scientific establishment. Despite stomach upsets Darwin explored in his notebooks the metaphysical implications of a consistent positivist creed, arguing that a person can be “congratulated for doing good” but the act is actually purely conditioned and “deserves no credit”. Indeed, “wickedness is no more a man’s fault than bodily disease!”. His Anglican friends would have found this deterministic materialism more shocking than his ideas of evolution. Such materialist ideas had been seized on by socialist agitators, red Lamarckians who stirred the mob to overthrow the social order and Chartists who even demanded the vote for working men! The establishment and the Tory press were quick to crush such ideas, using the full force of the law at a time when blasphemy was a criminal offence. Many were denounced and overthrown for such scandalous ideas, including the surgeon William Lawrence who was forced to resign his post and lost copyright on his book Lectures on Man. This book was promptly pirated by the notorious agitator and pornography publisher William Benbow, and then published in cheap editions such as the copy that Darwin now read. He was cautious about giving away his half-formed ideas, but openly mentioned his interest in the species question to friends and colleagues.
Dissenters such as John Wesley abhorred slavery and privilege, and had a bleaker view of nature than Paley. Darwin reflected these ideas in his notes, writing "Animals – whom we have made our slaves we do not like to consider our equals. – Do not slave holders wish to make the black man other kind? Animals with affections, imitation, fear, pain, sorrow for the dead." and "if we choose to let conjecture run wild then animals our fellow brethren in pain, disease death & suffering & famine; our slaves in the most laborious work, our companion in our amusements, they may partake, from our origin in one common ancestor we may all be netted together."
Animal observations 
By February 1838 Darwin was on to a new pocketbook, the maroon C notebook, and was investigating the breeding of domestic animals. He found the newspaper wholesaler William Yarrell at the Zoological museum a fund of knowledge, and questioned if breeders weren't going against nature in "picking varieties". He was now writing of "Descent" rather than transmutation, and hinting at ideas of "adaptation" to climate.
At the zoo on 28 March he had his first sight of an ape, and was impressed at the orang-utan's antics "just like a naughty child" when the keeper held back an apple. In his notes he wrote "Let man visit Ourang-outang in domestication, hear expressive whine, see its intelligence.... let him look at savage...naked, artless, not improving yet improvable & let him dare to boast of his proud preeminence." Here Darwin was drawing on his experience of the natives of Tierra del Fuego and daring to think that there was little gulf between man and animals despite the theological doctrine that only humanity possessed a soul.
On 1 April Charles wrote to his older sister Susan that he had also seen the rhinoceros in the zoo let out for the first time that spring, "kicking & rearing" and galloping for joy. He then passed on the gossip that Miss Martineau had been "as frisky lately [as] the Rhinoceros.— Erasmus has been with her noon, morning, and night:—if her character was not as secure, as a mountain in the polar regions she certainly would loose it.— Lyell called there the other day & there was a beautiful rose on the table, & she coolly showed it to him & said “Erasmus Darwin” gave me that.— How fortunate it is, she is so very plain; otherwise I should be frightened: She is a wonderful woman". He began thinking about marriage himself, listing the pros and cons on the back of an old letter and noting that rather than being "a man tied down in London" going over information, "I have so much more pleasure in direct observation... In country, experiment & observation on lower animals, – more space."
Darwin found a pamphlet by Yarrell's friend Sir John Sebright with a passage reading:
A severe winter, or a scarcity of food, by destroying the weak and the unhealthy, has all the good effects of the most skilful selection. In cold or barren countries no animals can live to the age of maturity, but those who have strong constitutions; the weak and the unhealthy do not live to propagate their infirmities.
After reading the pamphlet, Darwin commented "excellent observations of sickly offspring being cut off so that not propagated by nature".
Sebright talked of females falling to "the most vigorous males" and of how "the strongest individuals of both sexes, by driving away the weakest, will enjoy the best food, and the most favourable positions, for themselves and their offspring."To Darwin, while nature removed runts and thrust the fit forward, "the whole art of making [domestic] varieties" by selecting mates to breed an ornamental duck produced "a mere monstrosity propagated by art". Quizzing his cousin William Darwin Fox about crossing domestic breeds, he admitted for the first time that "It is my prime hobby & I really think some day, I shall be able to do something on that most intricate subject species & varieties." Pondering likely opposition to his ideas, he noted that there must have been "a thousand intermediate forms" between the otter and its land ancestor. "Opponents will say, show me them. I will answer yes, if you will show me every step between bull Dog & Greyhound."
Darwin's speculations in his notebooks deepened as he wondered how instincts and mental traits were passed on to offspring, finding it "difficult to imagine [thought as] anything but structure of the brain". He wrote of habits, beliefs and even the "love of deity" having evolved, adding to himself "oh you Materialist!". In private discussions with his cousin, "Hensleigh says the love of the deity & thought of him or eternity, only difference the mind of man & animals" which conflicted with Darwin's own experience with the "savages" of Tierra del Fuego. He struggled on with the Beagle geology, overworked, worried and suffering stomach upsets and headaches which laid him up for days on end. Privately he thought of the social implications of evolution, writing "Educate all classes, improve the women. (double influence) & mankind must improve." This was similar to the position of the radical Lamarckians, but female education was already supported by the whole Wedgwood-Darwin family, and strongly advocated by Martineau.
Darwin wrote "Man in his arrogance thinks himself a great work, worthy the interposition of a deity, more humble & I believe true to consider him created from animals." He thought grinning was "no doubt a habit gained by formerly being a baboon with giant canine teeth... Laughing modified barking, smiling modified laughing. Barking to tell [troop] good news. discovery of prey. – arising no doubt from want of assistance. – crying is a puzzler."
In June as he worried at these ideas and the Beagle Geology his illness intensified, with stomach upsets, headaches and heart troubles, so that he became overworked and laid up for days on end. "I hope I may be able to work on right hard the next three years... but I find the noddle & the stomach are antagonistic powers, and that it is a great deal more easy to think too much in a day, than to think too little – What thought has to do with digesting roast beef, – I cannot say."
At the same time Darwin was gaining public position, and on 21 June 1838 was elected to the establishment Athenaeum Club, along with Charles Dickens. He would dine there daily, feeling " like a gentleman, or rather like a Lord... I enjoy it the more, because I fully expected to detest it... one meets so many people there that one likes to see."
Thoughts of marriage 
The Hensleigh Wedgwoods were now living next door to Erasmus and were visited for a week by Catherine Darwin and Emma Wedgwood. Charles visited and found them "a very pleasant merry company", particularly noticing Emma's remarkably pleasant manners.
Illness prompted Darwin to take a break from the pressure of work and on 23 June 1838 he took the steamboat to Edinburgh to go "geologising" in Scotland. After revisiting Edinburgh on 28 June (the day that Queen Victoria had her coronation in London) he went on to Fort William. At Glen Roy in glorious weather he was convinced that he had solved the riddle of the "parallel roads" around the glen, which he identified as raised beaches, though later geologists would support the ideas of Louis Agassiz that these had been formed by glaciation.
Fully recuperated and optimistic, he returned home to The Mount, Shrewsbury. He discussed his ideas with his father and asked for advice about Emma. Speaking from experience, Doctor Robert Waring Darwin told his son to conceal religious doubts which could cause "extreme misery... Things went on pretty well until the husband or wife became out of health, and then some women suffered miserably by doubting about the salvation of their husbands, thus making them likewise to suffer." Charles drew up a list with two columns on a scrap of paper. Under Marry he listed benefits, "Children–if it please God–Constant companion & friend in old age will feel interested in one,–object to be beloved and played with, better than a dog anyhow.....Imagine living all one's day solitary in smoky dirty London House.–only picture to yourself a nice soft wife on a sofa with good fire, & books & music perhaps...", while Not Marry headed "Freedom to go where one liked... Not forced to visit relatives..to have the expense and anxiety of children.. fatness & idleness... if many children forced to earn one's bread..". He jotted down further thoughts, then concluded "My God, it is intolerable to think of spending ones whole life, like a neuter bee, working, working, & nothing after all. — No, no won't do. — Imagine living all one's day solitarily in smoky dirty London House. — Only picture to yourself a nice soft wife on a sofa with good fire, & books & music perhaps – Compare this vision with the dingy reality of Grt. Marlbro' St. Marry–Marry–Marry Q.E.D."
Then he spent his fortnight being "Very idle at Shrewsbury" which meant starting his "D" notebook on the transmutation sequence and his "M" notebook on the evolutionary basis of moral and social behaviour, filling sixty pages with notes and anecdotes from his father about experiences with patients.
Having come down in favour, he went to visit his cousin Emma on 29 July. He did not get around to proposing, but failed to conceal his ideas on transmutation. Emma noted "he is the most open, transparent man I ever saw, and every word expresses his real thoughts." When she asked about ultimate origins he steered clear of the subject, aware that "it will become necessary to show how the first eye is formed" which he could not yet do.
Malthus and natural law 
After returning to London on 1 August 1838 Darwin read a review of Auguste Comte's Positive Philosophy at the Athenaeum Club. It bolstered his pantheist ideas of natural laws, making him remark "What a magnificent view one can take of the world" with everything synchronised "by certain laws of harmony", a vision "far grander" than the Almighty individually creating "a long succession of vile Molluscous animals – How beneath the dignity of Him"! Only a "cramped imagination" saw God "warring against those very laws he established in all organic nature." His work on Coral Reefs and a paper theorising that Glen Roy had been an arm of the sea soldiered on. He visited the zoo to experiment, observing the reactions of the apes and seeing emotions like "revenge and anger", implying that "Our descent, then, [is the root] of our evil passions." He needed an ally, and hinted to Lyell that his work was "bearing on the question of species", amassing "facts, which begin to group themselves clearly under sub-laws."
Then in late September he began reading "for amusement" the 6th edition of Malthus's An Essay on the Principle of Population which reminded him of Malthus's statistical proof that human populations breed beyond their means and compete to survive, at a time when he was primed to apply these ideas to animal species. Malthus had softened from the bleakness of the earlier editions, now allowing that the population crush could be mitigated by education, celibacy and emigration. Already Radical crowds were demonstrating against the harsh imposition of Malthusian ideas in the Poor Laws, and a slump was resulting in mass emigration. Lyell was convinced that animals were also driven to spread their territory by overpopulation, but Darwin went further in applying the Whig social thinking of struggle for survival with no handouts. His views were secular, but not atheistic. He asked how God's laws had produced "so high a mind" as ours, with purpose shown by descent geared towards the "production of higher animals", suggesting that "we are [a] step towards some higher end".
Malthus's essay calculates from the birth rate that human population could double every 25 years, but in practice growth is kept in check by death, disease, wars and famine. Darwin was well prepared to see at once that this related to de Candolle's concept of "nature's war" and also applies to the struggle for existence amongst wildlife, so that when there is more population than resources can maintain, favourable variations that allow the organism to better use the limited resources available tend to be preserved, and unfavourable ones destroyed by being unable to get the means for existence, resulting in the formation of new species. On 28 September 1838 he noted this insight, describing it as a kind of wedging, forcing adapted structures into gaps in the economy of nature formed as weaker ones were thrust out. He now had a theory by which to work.
Darwin's thoughts and work continued and he suffered repeated bouts of illness. On 11 November he returned to Maer Hall and proposed to Emma.
Again he discussed his ideas, and she subsequently wrote telling him of her "fear that our opinions on the most important subject should differ widely. My reason tells me that honest & conscientious doubts cannot be a sin, but I feel it would be a painful void between us. I thank you from my heart for your openness with me & I should dread the feeling that you were concealing your opinions from the fear of giving me pain.... my own dear Charley, we now do belong to each other & I cannot help being open with you... Will you..read our Saviour's farewell discourse to his disciples [from the Gospel of St. John]. It is so full of love & devotion & every beautiful feeling". As well as "love one another" it also includes "If a man abide not in me...they are burned". He sent her a warm reply which gave her the comfort that he had entered into her heart's concern "a little more", but this tension would remain.
Emma's father promised a dowry of £5,000 plus £400 a year, while Doctor Darwin added £10,000 for Charles, to be invested. They decided to move to London until Charles had "wearied the geological public" with his itch to write, then they would "decide, whether the pleasures of retirement & country... are preferable to society."
Charles went house-hunting by day. At night he thought about "innumerable variations" (which he still thought were acquired in some way) with competitive nature selecting the best leading to step by step change, while vestigial organs like the human coccyx (tail) were not, as commonly thought, God "rounding out his original thought [to its] exhaustion", but ancestral remnants pointing to "the parent of man".
Darwin considered Malthus's argument, that human populations breed beyond their means and compete to survive, in relation to his findings about species relating to localities, earlier enquiries into animal breeding, and ideas of Natural "laws of harmony". Around late November 1838 he compared breeders selecting traits to a Malthusian Nature selecting from random variants, now thrown up by "chance", and in mid-December described this comparison as "a beautiful part of my theory, that domesticated races of organics are made by precisely same means as species – but latter far more perfectly & infinitely slower", so that in "species every part of newly acquired structure is fully practical & perfected."
The second edition of Charles Babbage's The Ninth Bridgewater Treatise. A Fragment published that year included a copy of a letter John Herschel had sent to Charles Lyell in 1836, not long before Darwin visited Herschel in Cape Town. On 2 December, Darwin wrote in his E Notebook "Babbage 2d Edit. p. 226 – Herschel calls the appearance of new species the mystery of mysteries, & has grand passage upon the problem.! Hurrah — 'intermediate causes' ". Herschel's letter advocated seeking natural causes, as opposed to miraculous causes, and gave philosophical justification to Darwin's project.
The Zoology ran into difficulties, with Richard Owen having to halt work on Fossil Mammalia, and John Gould sailing off for Tasmania leaving Darwin to complete the half finished Birds. "What can a man have to say, who works all morning in describing hawks & owls; & then rushes out , & walks in a bewildered manner up one street & down another, looking out for the word To Let'." Emma had arranged to come with the Hensleigh Wedgwoods to London for a week to help with the search for a house, and wrote telling him "It is very well I am coming to look after you my poor old man", before arriving on 6 December.
On 19 December 1838 as secretary of the Geological Society of London Darwin witnessed the vicious interrogation by Owen and his allies including Sedgwick and Buckland of Darwin's old tutor Robert Edmund Grant when they ridiculed Grant's Lamarckian heresy in a clear reminder of establishment hatred of evolutionism.
During her visit, Emma thought Darwin looked unwell and overtired. At the end of December she wrote urging him "to leave town at once & get some rest. You have looked so unwell for some time that I fear you will be laid up... nothing could make me so happy as to feel that I could be of any use or comfort to my own dear Charles when he is not well. So don't be ill any more my dear Charley till I can be with you to nurse you".
On 29 December 1838, Darwin took the let of a furnished property at 12 Upper Gower Street. He wrote to Emma that "Gower St is ours, yellow curtains & all", and of his delight at being the "possessor of Macaw Cottage". which he long recalled for its gaudy coloured walls and furniture that "combined all the colours of the macaw in hideous discord", Emma rejoiced at their getting a house she liked, while hoping that they had got rid of "that dead dog out of the garden". Darwin impatiently moved his "museum" in on 31 December, astounding himself, Erasmus and the porters with the weight of his luggage containing geological specimens.
On 24 January 1839 he was honoured by being elected as Fellow of the Royal Society and presented his paper on the Roads of Glen Roy. The next day he took the train home to Shrewsbury, then on the 28th travelled to Maer Hall.
On 29 January 1839, Charles married Emma at Maer, Staffordshire in an Anglican ceremony arranged to also suit the Unitarians, conducted by the vicar, their cousin John Allen Wedgwood. Emma's bedridden mother slept through the service, sparing Emma "the pain of parting". Immediately afterwards Charles and Emma rushed off to the railway station, raising their relative's eyebrows, and ate their sandwiches and toasted their future from a "bottle of water" on the train. Back at Macaw Cottage, Charles noted in his journal "Married at Maer & returned to London 30 years old", and in his "E" notebook recorded uncle John Wedgwood's views on turnips.
See the development of Darwin's theory for the ensuing developments, in the context of his life, work and outside influences at the time.
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- "Letter 449 – Wedgwood, Emma (Darwin, Emma) to Darwin, C. R., (3 Dec 1838)". Darwin Correspondence Project. Retrieved 16 June 2010.
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Note that this article is largely based on Desmond and Moore's book, with commentary summarised in other words and quotations (or extracts from quotations) repeated verbatim.
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