Darwin wrote to US geologist and zoologist James D. Dana in April 1857 to say:
[Professor] Owen has lately published a new Classification of mammals, taken from [i.e. based on] the structure of [their] Brain [s]; so great an authority ought to be right; but I cannot help always having doubts on a classification founded on one [single] character, however important.17
In that month of April Darwin told Lyell, ‘though as a general rule I am much opposed to the Forbesian continental extensions, I have no objection whatever to its being proved in some cases’.18 This was a reference to Edward Forbes, Professor of Natural History at Edinburgh University, who attempted to explain the distribution of flora and fauna by arguing that land masses must have been recently connected with each other. For example, said Forbes
Although I have made icebergs and ice-flows the chief agents in the transportation of an Arctic flora southwards, I cannot but think that so complete a transmission of that flora as we find in the Scottish mountains, was aided perhaps mainly by land to the north, now submerged.19
My main position may be stated in the abstract, as follows:
The specific identity, to any extent, of the flora and fauna of one area with those of another, depends on both areas forming, or having formed, part of the same specific centre, or on their having derived their animal and vegetable population by transmission through migration, over continuous or closely contiguous land, aided, in the case of alpine floras, by transportation on floating masses of ice.20
Forbes also believed that species were originated by acts of divine creation, in specific centres, from which they migrated to the limits set by their conditions of existence.
Darwin told Hooker on 3 June,
My observations, though on so infinitely a small scale, on the struggle for existence, begin to make me see a little clearer how the fight goes on: out of 16 kinds of seeds sewn on my meadow, 15 have germinated, but now they are perishing at such a rate that I doubt whether more than one will flower.21
Later that month Darwin asked Shropshire naturalist Thomas C. Eyton, to search ‘in Ireland or elsewhere for any cases of Horses or Ponies with transverse bars [stripes] on [their] legs like those of zebra, or on shoulder & along the back, as with the ass.’22
On 20 July in a letter to Asa Gray, Darwin included an ‘Enclosure’, in which the following words appeared
I think it can be shown that there is such an unerring power at work, or Natural Selection (the title of my Book), which selects exclusively for the good of each organic being.23
On 29 November, having been asked by Asa Gray to do so, Darwin defined what he understood by the term ‘Natural Selection’. It meant, he said,
The tendency to the preservation (owing to the severe struggle for life to which all organic beings at some time or generation are exposed) of the slightest variation in any part, which is of the slightest use or favourable to the life of the individual which has thus varied; together with a tendency to its inheritance.
Any variation, which was of no use whatever to the individual, would not be preserved by this process of ‘natural selection’.24
When his son Erasmus was in East Anglia with his tutor William Greive Wilson in February 1858 Darwin, anxious to miss no opportunity for scientific research, wrote to him to say,
As Norfolk is near Suffolk, look out for me, whether there are near you any Suffolk Punches or [other] large Cart-Horses of a Chestnut colour; if so, please observe whether they have a dark stripe or band down the spine to root of tail; also for mere chance, whether any trace of a cross stripe on the shoulder, where the Donkey has [them], & any cross-stripes on the legs.25
Darwin’s letter to Hooker of 23 June revealed, that on the domestic front, ‘Poor dear Etty [his daughter, Henrietta] has been very seriously ill with Dipterithes [diphtheria] …’.26 The health of the Darwin children will be discussed later.
To his son William, Darwin wrote on 22 September:
If you go out shooting look at Birds’ feet & see if any dirt sticks to them: I want to collect such dirt, & see, if by any splendid chance a plant would come up [derived from seed contained therein], for then could I not carry seeds across the sea!27
Of an address, delivered by Professor Owen to the British Association for the Advancement of Science, of which he was president, held at Leeds in that same month, Darwin subsequently declared, ‘He defines & further on amplifies his definition that Creation means a process he knows not what.’28
In October William commenced at Christ’s College, Cambridge – his father’s former college. The following February Darwin told Fox that William was ‘very happy at Cambridge & he has changed into my old rooms …’.29
Writing from Down on 24 February 1859 Darwin told his son George that a billiard table had arrived on the premises: ‘I heartily wish you & Willy were here to play with me. The whole affair has only cost £153. 18s. 0d.’30 Clearly, the loving relationship that had existed between Darwin and his late father was now being mirrored by that which now existed between Darwin and his offspring.
On 20 October Darwin told Lyell, who persisted in favouring the ‘Creationist’ notion of evolution
I have reflected a good deal on what you say on necessity of continued intervention of creative power. I cannot see this necessity; & its admission, I think would make the theory of [natural selection] valueless.31
Darwin was never afraid to challenge the theories of others, however eminent they might be. Yet, at the same time he was always ready to tell those, such as Lyell, how much he valued their friendship.
Another argument which the ‘Darwinists’ might have used against the ‘Creationists’ was put forward, a century and a half later, by US physician and evolutionary biologist Professor Randolph M. Nesse, who declared, ‘No sensible person would have ever left the body the way it is. The human eye is a perfect example of why the body is not designed.’, and Nesse drew attention to the fact a), that there is a ‘blind spot’ in the eye’s field of vision and b), there is always the possibility of near or far-sightedness. He proceeds to cite further examples of ‘poorly designed’ bodily components – the appendix, wisdom teeth, and the female birth canal, which might almost have been intended to make birth difficult. The existence of these ‘botched jobs’, or ‘built in vulnerabilities’, can be explained only by natural selection.32 Another argument, which Nesse might have put forward, was why would an intelligent ‘god’ trouble to create billions and billions of virtually identical organisms?
Darwin informed Professors Owen and Sedgwick, on 11 November, that he had instructed his publisher, John Murray, to send them each a copy of his forthcoming book The Origin of Species.33
In that year Darwin was awarded the Geological Society’s Wollaston Medal ‘for his geological work in South America, his theory of the origin and structure of coral reefs, and other contributions to geological science’.34
Finally, on 24 November, Darwin’s magnum opus The Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races [i.e. species] in the Struggle for Life, was published by John Murray.
Despite her misgivings about the theological implications of the work, Emma had previously helped her husband with the correction of the proofs.35
NOTES
1. Darwin to J. S. Henslow, 10 November [1855], Cor. 5, p.500.
2. Darwin to Edgar Leopold Layard, 9 December 1855, Cor.5, p.524.
3. Darwin to Henslow, 22 January [1856], Cor.6, p.25.
4. Cor.6, pp.55 and 56, note 2.
5. Darwin to Laurence Edmondston, 3 May [1856], Cor.6, p.99.
6. Darwin to W. D. Fox, 8 June 1856, Cor.6, p. 135.
7. Darwin to T. V. Wollaston, 6 June 1856, Cor.6, p.134.
8. Wollaston, T. Vernon, On the Variation of Species, with Special Reference to the Insecta; followed by an Enquiry into the Nature of Genera, pp.180, 188.
9. Darwin to J. D. Hooker, 17/18 June 1856, Cor.6, p.147.
10. Darwin to Charle
s Lyell, 5 July 1856, Cor.6, p.169.
11. Darwin to Charles Lyell, 10 November 1856, Darwin Correspondence Project, Letter 1984.
12. Darwin to S. P. Woodward, 18 July 1856, Cor.6, p.189.
13. Hamlet, Act 3, Scene 1.
14. Darwin to J. D. Hooker, 30 July 1856, Cor.6, p.193.
15. Darwin to Frances E. E. Wedgwood, 18 August 1856, Cor.6, p.205.
16. Darwin to J. D. Hooker (after 20 January 1857), Cor.6, p.325.
17. Darwin to J. D. Dana. 5 April 1857, Cor.6, p.367 (Owen 1857b).
18. Darwin to Charles Lyell, 13 April 1857, Cor.6, p.376.
19. Forbes, Edward, Essay ‘On the Connexion Between the Distribution of the Existing Fauna and Flora of the British Isles’, p.399.
20. Ibid, p.350.
21. Darwin to J. D. Hooker, 3 June 1857, Cor.6, p.407.
22. Darwin to T. C. Eyton, 26 June 1857, Cor.6, p.417.
23. Burkhardt, Frederick (editor), Charles Darwin’s Letters: A Selection 1825–1859, New York: Cambridge University Press, 1996, pp. 177–9.
24. Darwin to Asa Gray, 29 November 1857, Cor.6, p.492.
25. Darwin to William Erasmus Darwin, 11 February 1858, The Correspondence of Charles Darwin: Volume 7, 1858–1859, Cor.7, p.21.
26. Darwin to J. D. Hooker, 23 June 1858, Cor.7, p.115.
27. Darwin to W. E. Darwin, 22 September 1858, Cor.7, p.158.
28. Darwin to Huxley, 18 January 1861, C9, p.1 and p.2 note 9.
29. Darwin to W. D. Fox, 12 February 1859, Cor.7, p.247.
30. Darwin to George Howard Darwin, 24 February 1859, Cor.7, pp.251–2.
31. Darwin to Charles Lyell, 20 October 1859, Cor.7, p.354.
32. Richard Dawkins presents The Genius of Charles Darwin, C. IWC Media Ltd, Channel 4 DVD, 2008. Professor Randolph M. Nesse, in conversation with Professor Richard Dawkins.
33. Cor.7, pp.371, 373.
34. The Correspondence of Charles Darwin: Volume 12, 1864, p.509.
35. Darwin, Francis, op. cit., p.59.
Chapter 15
The Origin of Species
Darwin’s masterpiece was The Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life commonly abbreviated to Origin. It was concerned not only with how animals and plants had evolved, but also with the mechanisms by which they had become distributed over the Earth’s surface. Darwin’s observations also included those of animals in their pre-natal state. He wrote:
Hardly any point gave me any satisfaction when I was at work on the Origin, as the explanation of the wide difference in many classes between the embryo and the adult animal, and of the close resemblance of the embryos within the same class.1
In 1958, almost a century after it was published, Julian Huxley, grandson of Professor Thomas H. Huxley, posed the question
Why is The Origin of Species such a great book? First of all, because it convincingly demonstrates the fact of evolution: it provides a vast and a well-chosen body of evidence showing that existing animals and plants cannot have been separately created in their present forms, but must have evolved from earlier forms by slow transformation. And secondly, because the theory of natural selection, which the Origin so fully and lucidly expounds, provides a mechanism by which such transformation could and would automatically be produced. Natural selection rendered evolution scientifically intelligible: it was this more than anything else which convinced professional biologists like Sir Joseph Hooker, T. H. Huxley, and Ernst Haeckel (German biologist and physician).2
In his ‘Introduction’ to Origin, Darwin states that, having returned from the Beagle voyage,
It occurred to me, in 1837, that something might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years’ work I allowed myself to speculate on the subject, and drew up some short notes; these I enlarged in 1844 into a sketch of the conclusions, which then seemed to me probable: from that period to the present day I have steadily pursued the same object.
I have been urged to publish this Abstract … [i.e. Origin], as Mr Wallace, who is now studying the natural history of the Malay Archipelago, has arrived at almost the same general conclusions that I have on the origin of species.3
Chapter 1: Variation under Domestication
Of domestic pigeons, wrote Darwin,
I have kept every breed which I could purchase or obtain … . The diversity of the breeds is something astonishing. Great as are the differences between the breeds of the pigeon, I am fully convinced … that they are all descended from the rock-pigeon [rock dove] (Colomba livia) … .4
The same applied to plants. For example
the strawberry had always varied since it was cultivated, but the slightest varieties had been neglected. As soon, however, as gardeners picked out individual plants with slightly larger, earlier, or better fruit, and raised seedlings from them, and again picked out the best seedlings and bred from them, then (with some aid by crossing distinct species) those many admirable varieties of strawberry were raised which have appeared during the last half-century.5
To sum up on the origin of our domestic races of animals and plants. Changed conditions of life are of the highest importance in causing variability, both by acting directly on the organisation, and indirectly by affecting the reproductive system. Variability is governed by many unknown laws … . Over all these causes of Change, the accumulative action of Selection, whether applied methodically and quickly, or unconsciously and slowly but more efficiently, seems to have been the predominant power.6
Here, Darwin postulates on the one hand, that variations are principally the result of changes in the environment, but on the other, admits that the question of variability remains largely an open one.
Chapter 2: Variation under Nature
Individual differences
The many slight differences which appear in the offspring from the same parents … may be called individual differences.7
Summary
We have … seen that it is the most flourishing or dominant species of the larger genera within each class which on an average yield the greatest number of varieties; and varieties, as we shall hereafter see, tend to become converted into new and distinct species. Thus the larger genera tend to become larger; and throughout nature the forms of life which are now dominant tend to become still more dominant by leaving many modified and dominant descendants. But by steps hereafter to be explained, the larger genera also tend to break up into smaller genera. And thus, the forms of life throughout the universe become sub-ordered into groups subordinate to groups.8
Chapter 3: Struggle for Existence
Darwin identifies climate, the availability of food, and the tendency of animals to prey upon one another as three of the factors which limit a species from increasing ‘inordinately in numbers’. If, however, a species does multiply, despite these factors, then ‘epidemics [of illness, causing disease and death] often ensue …’.9
Chapter 4: Natural Selection; or the Survival of the Fittest
Divergence of Character
Mere chance … might cause one variety to differ in some character from its parents, and the offspring of this variety again to differ from its parent in the very same character and in a greater degree; but this alone would never account for so habitual and large a degree of difference as that between species.10
On the Degree to Which Organisation Tends to Advance
Natural selection acts exclusively by the preservation and accumulation of variations, which are beneficial under the organic and inorganic conditions to which each creature is exposed at all periods of life. The ultimate result is that each creature tends to become more and more improved in relation to its conditions. This improvement leads to the gradual advancement of the organisation of the greater number of living beings throughout the world.11
Chapter 5: Laws of Variation
I have hitherto sometimes sp
oken as if the variations … were due to chance. This, of course, is a wholly incorrect expression, but it serves to acknowledge plainly our ignorance of the cause of each particular variation.12
Although Darwin is anxious to explain why variation in species occurs, he is honest enough to admit that to do so was beyond the scope of present scientific knowledge.
Chapter 7: Miscellaneous Objections to the Theory of Natural Selection
A serious objection has been urged by [German geologist and palaeontologist Heinrich G.] Bronn, and recently by [French physician and anthropologist Pierre Paul] Broca, namely, that many characters appear to be of no service whatever to their possessors, and therefore cannot have been influenced through natural selection.
There is much force in the above objection. Nevertheless, we ought, in the first place, to be extremely cautious in pretending to decide what structures now are, or have formerly been, of use to each species.13
Mr [St George J.] Mivart [biologist] is … inclined to believe that new species manifest themselves ‘with suddenness and by modifications appearing at once’. This conclusion, which implies great breaks and discontinuity in the series, appears to me improbable in the highest degree.14
Chapter 8: Instinct
No one will dispute that instincts are of the highest importance to each animal. Therefore there is no real difficulty, under changing conditions of life, in natural selection accumulating to any extent slight modifications of instinct which are in any way useful.15
Here, Darwin surmises that in the same way as physical characteristics may be inherited, so instinct may also be a heritable phenomenon.
Chapter 10: On the Imperfection of the Geological Record
Charles Darwin Page 12