<p style='text-align: justify;'><p>One of a series of notebooks including <a href='/view/MS-DAR-00122'>Notebook C (MS DAR 122)</a>, <a href='/view/MS-DAR-00123'>Notebook D (MS DAR 123)</a>, and <a href='/view/MS-DAR-00124'>Notebook E (MS DAR 124)</a> on transmutation of species created by Darwin following his return from the Beagle voyage in 1837. They were inspired especially by his observations of the geographical distribution of species and the affinities between extinct and currently existing animals in South America. Darwin started writing this notebook in July 1837 and completed entries in it by around February 1838.</p><p>Notebooks B and C show Darwin’s thinking before he read Thomas Malthus’s <i>Essay on the Principle of Population</i> in late September 1838, which suggested to Darwin the idea of natural selection as a mechanism for evolution, elaborated in Darwin’s <i>Sketch</i> (1842) and <i>Essay</i> (1844) outlining the argument of his <i>Origin of Species</i> (1859) The notebooks provide an extraordinary insight into Darwin’s search for the solution to what one contemporary had called ‘that mystery of mysteries’, the origin of new species. They draw on a remarkable variety of sources, from readings in philosophy, economics and literature to conversations with breeders of dogs, horses and poultry. At this time Darwin was living in central London, close to good libraries and an unparalleled range of scientific expertise.</p><p>Darwin opens Notebook B by exploring the idea that species evolve through changes induced through sexual reproduction—a view he later rejected in favour of natural selection. Geographical isolation of these changes, as on the Galapagos archipelago, would lead to diversity. The famous <a href='' onclick='store.loadPage(21);return false;'>‘transmutation’ diagram</a> illustrates the branching system of descent that explained the relations between existing and extinct species. Species well adapted to their circumstances would continue their lineage, whereas others would become extinct.</p><p>A transcription of this <a target='_blank' class='externalLink' href='https://www.amnh.org/research/darwin-manuscripts/catalogue-darwin-manuscripts/cambridge-university-library?darbaseurl=https%3A%2F%2Fdarwin.amnh.org%2Fviewer.php%3Feid%3D73125'>notebook</a> is available on the <a target='_blank' class='externalLink' href='https://www.amnh.org/research/darwin-manuscripts'>Darwin Manuscripts Project website</a>.</p></p>
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