Inception of Darwin's theory

Reading about Malthus and natural law led him to apply to his search the Malthusian logic of social thinking of struggle for survival with no handouts, and he "had at last got a theory by which to work".

At Edinburgh University his work as a student of Robert Edmund Grant involved him in pioneering investigations of the ideas of Lamarck and Erasmus Darwin on homology showing common descent, but he also saw how controversial and troubling such theories were.

I had always been much struck by such adaptations, and until these could be explained it seemed to me almost useless to endeavour to prove by indirect evidence that species have been modified.When Beagle returned, it anchored at Falmouth, Cornwall, on 2 October 1836.

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.

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".

Darwin paid a visit to his brother Erasmus'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.

[9] 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.

[11] Owen was finding unexpected relationships from the fossils: the batch included the horse sized Scelidotherium which appeared to be closely allied to the anteater,[5] 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.

[12] 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.

On the 13th he moved to nearby lodgings, joining Erasmus's circle of friends including Martineau and Hensleigh and enjoying his intimate dinner parties with guests such as Lyell, Babbage and Thomas Carlyle.

[14] 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".

As a Unitarian, Martineau 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.

[20] 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 of 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 London University 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 supporting radical demands for democracy.

Later notes mention discussions with other experts, including the geographer Sir Woodbine Parish, geologists Charles Lyell and Roderick Murchison, and the conchologist James De Carle Sowerby.

[26] At the same meeting, announcements were made of the first discoveries of ancient fossil primates; finds by Proby Cautley and Hugh Falconer in Neogene strata of the Sivalik Hills, and by Édouard Lartet in Miocene beds at Sansan, Gers.

[27] Later, Lyell joked uncomfortably to his sister that "according to Lamarck's view, there may have been a great many thousand centuries for their tails to wear off, and the transformation to men to take place", but Darwin was beginning to look at these "wonderful" fossils in relation to transmutation.

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,[29] a sum equivalent to about £115,000 in present-day terms.

[40] This novel view contrasted with the ideas of transmutationists of the time (including Lamarck and Grant), who envisaged independent parallel lineages impelled by inner forces to make progress to higher forms.

[46] 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.

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[original research?]

[50] 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.

[54] Contrary to the views of his Cambridge professors that humans were "godlike", around February 1838 Darwin wrote in his B notebook; "Animals whom we have made our slaves we do not like to consider our equals.

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.

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.

– take a solitary walk on Salisbury crags & call up old thoughts of former times then go on to Glasgow & the great valley of Inverness, – near which I intend stopping a week to geologise the parallel roads of Glen Roy, – thence to Shrewsbury, Maer for one day, & London for smoke, ill health & hard work.

[93] 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.

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.

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.