The letters in this volume span the years from 1825, when Darwin was a student at the University of Edinburgh, to the end of 1859, when the Origin of Species was published. The early letters portray Darwin as a lively sixteen-year-old medical student. Two years later he abandoned any idea of following his father in becoming a physician and transferred to Cambridge University to prepare for the ministry. His interests as an undergraduate at Cambridge, as at Edinburgh, were clearly outside the established academic curriculum. He became an enthusiastic collector of insects, and a devoted follower of the professor of botany, John Stevens Henslow, who encouraged his interest in natural history, for which no degree was then offered. Soon after Darwin took his BA degree, Henslow recommended him for the post of unoffical naturalist and companion to Robert FitzRoy, captain of HMS Beagle, which was being prepared for a survey voyage to South America and the Pacific.
The letters that Darwin sent to his family and to Henslow during the Beagle‘s five-year circumnavigation of the globe contain extensive accounts of his experiences and observations. When excerpts from the letters to Henslow were made known to the learned societies in Cambridge and London, they aroused such intense interest that, by the time the Beagle arrived back in England in 1836, Darwin was already a well-known naturalist and an accepted member of the scientific community.
The years following his return were devoted to writing up the results of the voyage. His first book, Journal of researches, was to become one of the most famous travel books ever published. It was followed by three volumes on the geology of the voyage, in one of which he proposed a new explanation of the formation of coral reefs that won the support of Charles Lyell, the leading English geologist of the time. With a grant of £1000 from the Treasury he superintended and edited the Zoology of the voyage of the Beagle, a series of monographs in nineteen parts by expert taxonomists, describing the fossil and living mammals, fish, birds, and reptiles collected during the voyage. Darwin supplied geological and geographical introductions, with notes on the habits and ranges of the species. By 1846, he had also published over twenty-five scientific papers, almost all of them directly related to the observations made during the voyage.
The prodigious quantity of work produced during these years was achieved despite several periods of an illness that was to plague Darwin for most of his life. None of his many physicians ever found the cause and no treatment provided more than temporary alleviation. To this day it remains a subject of great interest to Darwin scholars and medical historians.
On 1 October 1846, Darwin, noting in his diary that he had finished the third volume of the geology of the voyage, wrote: ‘Now it is 10 years since my return to England. How much time lost by illness!’ On that same day, he began a description of an interesting barnacle that he had found off the coast of Chile. To understand its structure, he undertook to compare it with that of other species, and, finding that the literature on the classification of Cirripedia was chaotic and full of errors, he embarked on a study of both the fossil and living species. It was eight years before he completed what was the first taxonomic study of the entire order.
By this time, 1854, Darwin had become a family man. In January 1839, he had married his cousin Emma Wedgwood. In December of that year, William Erasmus Darwin was born, the first of ten children, two of whom died in infancy. A third, his beloved daughter Annie, died at the age of ten in 1851. The letters are an intimate chronicle of Darwin and of an affectionate family. A fascinating aspect of their close relationship is the extent to which the children, as they grew up, became active participants in Darwin’s scientific work. Even at an early age he encouraged them to make botanical and entomological observations for him. Though not mentioned specifically in the letters, field notes exist that record the observations made between 1854 and 1861 by five of his children, on the flight routes of male humble-bees.
As noted above, almost all of Darwin’s published work up to this time was the direct result of the Beagle voyage. Another, and eventually more important result, had not yet led to any published account, nor did it receive much direct mention in his letters. This was his work on what he called ‘the species problem’.
On the last leg of the homeward journey, as Darwin organised his notes on the Galápagos birds, it struck him that the indigenous mocking-birds were closely allied to species on the mainland, and yet were distinct and unique to that archipelago. In London, the similarity of the fossils of extinct mammals he had found in South America to some of the living animals, and John Gould’s naming of thirteen species of finches collected in the Galapagos impelled him to start investigating the possibility of evolution. His diary records his memory of the momentous decision in 1837:
In July opened first note Book on ‘transmutation of Species’— Had been greatly struck from about month of previous March —on character of S. American fossils—& species on Galapagos Archipelago. These facts origin (especially latter) of all my views.
The notebooks that he filled in the years that followed record an extraordinary amount of reading and collecting of facts on variations in plants and animals, with speculations
on how species might have arisen. In September 1838, reading Thomas Malthus’s Essay on the principle of population (London, 1826), he found a clue: in the competition for food, any variation that gave the slightest advantage would count in the struggle for survival. From then on his researches were guided by this hypothesis, which he named ‘natural selection’.
The letters show that Darwin was not as secretive about his species doubts as has been commonly thought. Between 1838 and 1857, he told at least ten of his correspondents that he was investigating the mutability of species. As early as 14 September 1838, before reading Malthus, he wrote to Lyell about ‘the delightful number of new views that have been coming in, thickly & steadily, on the classification & affinities & instincts of animals——bearing on the question of species—— note book, after note book has been filled, with facts, which begin to group themselves clearly under sub laws.’
In the years that followed, numerous letters were concerned with this search for data relevant to the species question, though without any direct mention of the theory behind the search. Correspondents all over the globe were plied with questions and requests for facts and specimens. His most important source of both information and critical discussion of his theory was, however, close at hand in the person of Joseph Dalton Hooker. Hooker had recently returned from an expedition to Antarctica to become assistant to his father, the director of the Royal Botanic Gardens at Kew. In his letter of 11 January 1844, Darwin revealed to Hooker that he thought he had found the mechanism of transmutation. There followed a lengthy and voluminous exchange of letters in which a close friendship developed, and Hooker became deeply involved in Darwin’s work as counsellor, critic, and, increasingly, as a collaborator in the construction of the case for mutability and natural selection.
In September 1855, an article by Alfred Russel Wallace appeared with the title, ‘On the law which has regulated the introduction of new species’. Wallace had been studying the geographical distribution of animals and plants in Malaysia and had concluded that every species had ‘come into existence coincident both in time and space with a pre-existing closely allied species’. To Charles Lyell this was a warning that Wallace might be on the track of something close to Darwin’s theory, and he urged his friend to publish, lest he be forestalled. Darwin, somewhat reluctantly, began to write ‘a sketch’, but found that, in order to present a convincing proof of his theory, a much longer work was required. He had written a quarter of a million words in ten and a half chapters of what he came to call his ‘big book’, when, in June 1858, he received the famous letter from Wallace in which was enclosed a manuscript describing his own independent discovery of natural selection. Lyell and Hooker, to salvage the twenty years of Darwin’s work, proposed that Wallace’s manuscript be published jointly with some excerpts of Darwin’s earlier, though unpublished, writing on the subject. The joint paper was read at the Linnean Society on 1 July 1858. A few weeks later, Darwin set to work on a condensation of his long manuscript. It too grew beyond the limits of any learned journal, despite the omission of much supporting data and sources. The result was the Origin of species.