In October 1838, Darwin began 'for amusement' Malthus’s Essay on the Principle of Population. This seminal work on population growth provided him with a vital key: 'being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The result of this would be the formation of new species. Here, then, I had at last got a theory by which to work' (Autobiography).
Thomas Robert Malthus, An Essay on the Principle of Population. Vol. I. London: Printed for J. Johnson, 1807. DeB Eb 1807M
In 1848, Henry Walter Bates (1825-92) accompanied Wallace on an expedition to the Amazon, with the prime purpose to gather facts 'towards solving the problem of the origin of species', a subject that both men frequently discussed. After eleven years collecting in Brazil, Bates, a committed evolutionist, returned to England and was encouraged by Darwin to write an account of his travels. On publication in 1863, Darwin described it as 'the best work on natural travels ever published in England.' This is a later edition.
Henry Walter Bates, The Naturalist on the River Amazons. London: John Murray, 1915. Leith Storage KUL B
Alfred Russel Wallace (1823-1913) read much the same books as Darwin: Lyell’s Principles, Chambers’ Vestiges, Malthus’s Essay, Humboldt’s Personal Narrative, and Darwin’s own Journal of Researches. After the Amazon, he spent eight years in the Far East (Borneo) collecting and analyzing data which refined his thoughts about evolution. In February 1855, he wrote a paper that appeared in the Annals and Magazine of Natural History that concluded with: 'Every species has come into existence coincident both in space and time with a closely allied species.' This foreshadowed his later thoughts on natural selection, most of which can be found in his Contributions.
Alfred Russel Wallace, Contributions to the Theory of Natural Selection. London: Macmillan, 1875. Leith Storage QH 366 W5391
In 1858, while on the island of Ternate (North Maluku, Indonesia), and suffering from a fever, Wallace conceived the principle of natural selection. While the notion was arrived at independently, Wallace had been stimulated by reading Darwin’s own researches. Nevertheless, when Darwin received Wallace’s notes at Down House in June 1858, it almost derailed his own work. It forced Darwin to publish his own ‘Species’ theory. The frontispiece image in Wallace’s Malay work is now a classic one.
____, The Malay Archipelago. Vol. I. London: Macmillan, 1869. Special Collections DS 601 W541