London Years - Darwin's scientific manuscripts from Spring 1837 - July 1842
In January 1837, shortly after the Beagle voyage ended, Darwin settled in London. The five years he lived in the capital of Britain and of British science, saw his most brilliant period of intellectual activity. It was in London that Darwin not only accepted, but also committed himself to critically testing the species theory in his private Transmutation Notebooks and his Metaphysical Notebooks. It was in the course of filling the Notebooks that in 1838-1839 he first grasped and elaborated natural selection as a central ‘agency’ or mechanism for explaining the origins of both adaptation and new species.
The Notebooks bring us extraordinarily close to Darwin’s theory making as he postulates successive connected explanations, that each deploys the ‘known laws’ of reproduction and variation to explain what for Darwin was the key evolutionary phenomenon: adaptation to environmental and geological change. As Darwin thought through different sides of reproduction and variation, his assumptions and the internal logic of his explanation were revised. It was Darwin’s fortune that out of this process he grasped the concept of natural selection, where competition for resources in reproducing populations sifts hereditary variants and thereby produces adaptation.
Thus during the London years, Darwin laid out the scope and formulated the theoretical core that defined the rest of his life.
At the end of the London period, while transitioning to his permanent residence—Down House in Kent—Darwin wrote the first narrative draft of the theory, which he latter described as ‘First Pencil Sketch of Species Theory | Written at Maer & Shrewsbury during May & June 1842.’ Thus the London years mark the beginning of the writing of what became the Origin of Species.
In the Notebooks, Darwin’s writing was often terse, with no continuous narrative extending for more than a few hundred words. In the 1842 Sketch, the narratives stretch to many foolscap pages. Yet Darwin’s sentences and paragraphs often break off and revert to the concise summary comments that characterize the Notebooks. Significantly, the Sketch was accompanied by a list of ‘Omissions’. Nevertheless, in places the language of the Sketch evokes the Origin. For example, Darwin evidently invented the fateful term ‘natural selection’ as the title for a section of the Sketch. The crucial structural analogy of selection under domestication versus natural selection, which we find perpetuated in the Origin was first established in the Sketch. Also the beautiful language of the Origin is anticipated in Sketch’s concluding lines:
"There is a simple grandeur in this view of life «with its power of ‹growth›, assimilation & reproduction» being «originally» breathed into matter under one or a few forms & that whilst this our planet has gone circling on according to fixed laws, & land & water in a cycle of change has gone on replacing each other, ‹by› «that» ‹&› from ‹this› «so» simple «an» origin through the process of gradual selection of infinitesimal changes endless forms most beautiful & Most wonderful have been evolved.—"