Sunday, July 30, 2017

Malthus, Darwin and Evolution

Thomas Robert Malthus’ An Essay on the Principle of Population was first published in 1798. An influential revised edition followed in 1803, and a sixth edition in 1826. In this work, Malthus mulled over the population, social and economic trends that we now call Malthusianism.

Charles Darwin was driven to one of his most important insights into biological evolution by reading Malthus’ An Essay on the Principle of Population in 1838 in the sixth edition, during a terrible depression in England (Desmond and Moore 1991: 264–265; Browne 1995: 385–390). It is dramatised in this documentary:

Darwin began reading Malthus on 28 September 1838. After he finished reading it on 3 October 1838, he soon formulated the principle of natural selection (Browne 1995: 388–390). He also took inspiration from the creation of new breeds of animals by artificial selection, and from the work of Charles Lyell which emphasised the struggle of survival between species.

Darwin seems also to have taken inspiration from Adam Smith’s metaphor of the “invisible hand”: only it was the “invisible hand” of differential survival rates of individuals of the same species in nature, selected for their greater fitness given accidental genetic traits, that was the mechanism for evolution of individual species (Browne 1995: 389).

This was explicitly stated by Darwin both in his autobiography and in a letter to Alfred Russel Wallace of 1859, the relevant quotations from which are reproduced below:
(1) Darwin’s “Autobiography”:

“In October 1838, that is, fifteen months after I had begun my systematic enquiry, I happened to read for amusement ‘Malthus on Population,’ and 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; but I was so anxious to avoid prejudice, that I determined not for some time to write even the briefest sketch of it. In June 1842 I first allowed myself the satisfaction of writing a very brief abstract of my theory in pencil in 35 pages; and this was enlarged during the summer of 1844 into one of 230 pages, which I had fairly copied out and still possess.” (Darwin 1911: 68).

(2) Letter to Alfred Russel Wallace, Down, April 6th, 1859:

“I this morning received your pleasant and friendly note of November 30th. ….

You are right, that I came to the conclusion that selection was the principle of change from the study of domesticated productions; and then, reading Malthus, I saw at once how to apply this principle. Geographical distribution and geological relations of extinct to recent inhabitants of South America first led me to the subject: especially the case of the Galapagos Islands. I hope to go to press in the early part of next month. It will be a small volume of about five hundred pages or so. I will of course send you a copy. …. .” (Darwin 1903: 118–119).
Browne, Janet. 1995. Charles Darwin: Voyaging. Volume 1 of a Biography. Pimlico, London.

Darwin, Francis (ed.). 1903. More Letters of Charles Darwin: A Record of his Work in a Series of Hitherto Unpublished Letters (vol. 1). John Murray, London.

Darwin, Francis (ed.). 1911. The Life and Letters of Charles Darwin, including an Autobiographical Chapter (volume 1). D. Appleton and Company, New York and London.

Desmond, Adrian and James Moore. 1991. Darwin. Penguin Books, London.

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