There is a common misconception, which has surely been exacerbated by this year's bi-centennial celebrations, that Charles Darwin thought up his theory of evolution all by himself as a result of his own observations of nature. The reality is that no-one in Victorian Britain could have been better placed to be an evolutionist in terms of the influences that chance bestowed upon him. The accompanying chart shows the main influences upon Darwin and some of the known influences upon them.
Though not the first person in the modern era to have expressed evolutionary views, the first on the chart (on account of his known influence) is Pierre de Maupertuis, a French mathematician/philosopher whose anonymously published 1745 book, "Venus Physique", contained the following passage, which clearly anticipates Darwin:
Could one not say that, in the fortuitous combinations of the productions of nature, as there must be some characterized by a certain relation of fitness which are able to subsist, it is not to be wondered at that this fitness is present in all the species that are currently in existence? Chance, one would say, produced an innumerable multitude of individuals; a small number found themselves constructed in such a manner that the parts of the animal were able to satisfy its needs; in another infinitely greater number, there was neither fitness nor order: all of these latter have perished. Animals lacking a mouth could not live; others lacking reproductive organs could not perpetuate themselves. The species we see today are but the smallest part of what blind destiny has produced.
It was necessary to publish such heretical views anonymously (or under a pseudonym as Maupertuis later did) in pre-Revolutionary France, since the Catholic authorities came down very hard on deviations from Biblical orthodoxy.
A French diplomat, Benoit de Maillet, who had spent much of his life in India, reversed his name in the title of a fictional book, "Telliamed", in which an Indian philosopher expounds fantastical evolutionary views, such as fish turning into birds, but it was not published until 1748, ten years after its author's death. The book became a succes de scandale in France, so it could have been very influential.
A maverick French aristocrat, George-Louis Leclerc Buffon, who would undoubtedly have been guillotined if he hadn't died naturally the year before the revolution started, was the director of the Paris Jardin du Roi (which became the Museum of Natural History after the Revolution). He was the nominal author of a 44 Volume "Histoire Naturelle", begun in 1749. His early expressions of evolutionary beliefs, and his conviction that the world was very old, led to his being 'persuaded' to recant, so his strongest evolutionary assertion, in 1753, came complete with its own retraction:
....if the point were once gained that among animals and vegetables there had been, I do not say several species, but even a single one, which had been produced in the course of direct descent from another species; if for example it could be once shown that the ass was but a degeneration from the horse - then there is no further limit to be set to the power of nature, and we should not be wrong in supposing that with sufficient time she could have evolved all other organized forms from one primordial type.
But no! It is certain from revelation that all animals have alike been favoured with the grace of an act of direct creation, and that the first pair of every species issued full formed from the hands of the Creator.
If ever there was a tongue in cheek sentence, it is that last one. One of Buffon's acquaintances was the French writer and encyclopaedist, Denis Diderot, who did get imprisoned for expressing heretical, atheistic views and lived his life in constant danger of exile or further imprisonment. However, in 1754, he managed to slip the following passage into his "Thoughts on the Interpretation of Nature" without attracting undue attention:
If we consider the animal kingdom, and notice that among the quadrupeds there is none whose physical parts and functions, particularly the internal ones, are not quite similar, may we not readily believe that there was never more than one primeval animal, the prototype of all, while nature only lengthened, shortened, transformed, multiplied or obliterated some of its organs?
Though Diderot had a considerable influence on European intellectuals, I am not aware of his evolutionary views being cited. Buffon had phenomenal influence throughout Europe. In Scotland, he came to the attention of Lord Monboddo, an eccentric, judge and amateur anthropologist, whose principal interest was in the way different languages had evolved from a common root. His claim that humans had evolved from tailed apes was regarded with ridicule, as was his bizarre belief that midwives cut the tails off human babies. He is not included in the chart since his contribution was anecdotally amusing but not important.
Both Buffon and Monboddo influenced an English polymath, physician and famous grandfather, Erasmus Darwin, whose 1794 book, "Zoonomia", clearly expressed evolutionary views as well as an early indication of sexual selection:
Would it be too bold to imagine that, in the great length of time since the earth began to exist, perhaps millions of ages before the commencement of the history of mankind, would it be too bold to imagine, that all warm-blooded animals have arisen from one living filament, which THE GREAT FIRST CAUSE endued with animality, with the power of acquiring new parts, attended with new propensities, directed by irritations, sensations, volitions and associations, and thus possessing the faculty of continuing to improve by its own inherent activity, and of delivering down these improvements by generation to its posterity, world without end!
As air and water are supplied to animals in sufficient profusion, the three great objects of desire which have changed the forms of many animals by their desires to gratify them are those of lust, hunger, and security. A great want of one part of the animal world has consisted in the desire of the exclusive possession of the females; and these have acquired weapons to combat each other for this purpose, as the very thick, shield-like, horny skin on the shoulder of the boar is a defence only against animals of his own species who strike obliquely upwards, nor are his tusks for other purposes except to defend himself, as he is not naturally a carnivorous animal. So the horns of the stag are sharp to offend his adversary, but are branched for the purpose of parrying or receiving the thrust of horns similar to his own, and have therefore been formed for the purpose of combating other stags, for the exclusive possession of the females; who are observed like the ladies in the times of chivalry to attend the car of the victor.
Maupertuis had spent part of his life in Berlin, where he influenced many German thinkers, some of whom developed his, and Buffon's, evolutionary views. They were the philosophers, Kant, Herder and Schelling, the all-round genius, Goethe, and the biologists, Treviranus and Oken. In his 1795 "Introduction to Comparative Anatomy", Goethe came up with the boldest assertion yet:
Thus much then we have gained, that we may assert without hesitation that all the more perfect organic natures, such as fishes, amphibious animals, birds, mammals, and man at the head of the last, were all formed upon one original type, which only varies more or less in parts which are none the less permanent, and still daily changes and modifies its form by propagation.
Lorenz Oken subsequently included the most disillusioning view of evolution yet in his 1809 "Manual of the Philosophy of Nature":
Every organic thing has arisen out of slime, and is nothing but slime in different forms. This primitive slime originated in the sea, from inorganic matter in the course of planetary evolution.
Like Buffon and Erasmus Darwin, those early German evolutionists all rejected Biblical literalism, but they still believed that evolution was the method of creation rather than an alternative to it. That belief has remained commonplace ever since, right up to many of today's exponents of Intelligent Design.
We return to France now, where one of Buffon's proteges, for whom he had secured a position at the Jardin du Roi, was Jean-Baptiste Lamarck. By 1809, Lamarck had developed a comprehensive theory of evolution and written about it in his masterpiece, "Philosophie Zoologique", from which comes the following, bold, early assertion:
I shall show that the habits by which we now recognise any species are due to the conditions of life under which it has for a long time existed, and that these habits have had such an influence upon the structure of each individual of the species as to have at length modified this structure, and adapted it to the habits which have been contracted.
And that is what the rest of the book attempted to do. Quite simply, Lamarck was the first person to nail his colours to the mast and stake his whole reputation on being an evolutionist. His theory was total and natural, in the sense that he saw evolution from simple, spontaneously-generated organisms (which we would now call bacteria) as the way that all the present wide variety of species had been produced, without the aid of any outside agency. It was also naive, since he thought all change was entirely due to the responses that organisms made to the environments they inhabited. Thus he relied on the mechanism of the inheritance of acquired characteristics to allow progressive accumulation of the effects of responses.
Since few natural historians or biologists have doubted that the environment can have some effect on organisms, and the science of epigenetics is now showing that the inheritance of acquired characteristics is a reality that has to be accommodated in evolution theory, Lamarck ought to be regarded with great reverence by evolutionists. But he isn't. Instead, his theory has been by turns condemned, disparaged, ignored, ridiculed and vilified for the last 200 years, and his reputation became as the person who got evolution theory wrong. That is because he hadn't got the mechanism of natural selection, though the following passage shows that he was not oblivious to the issue of competition and survival:
In consequence of the extremely rapid rate of increase of the smaller, and especially of the most imperfect, animals, their numbers would become so great as to prove injurious to the conservation of breeds, and to the progress already made towards more perfect organisation, unless nature had taken precautions to keep them down within certain fixed limits which she cannot exceed.......
The strongest and best armed for attack eat the weaker, and the greater kinds eat the smaller.
Lamarck's commitment to evolution was continued in his 7 volume,"Histoire Naturelle des Animaux sans Vertebres", published between 1815 and 1822.
Two people not included in the chart (for the sake of neatness) were Etienne Geoffroy Saint-Hilaire and his son. Between them, they kept Lamarckian theory alive in France in the first half of the 19th century, though neither was as bold or committed as Lamarck in their assertions.
A Scottish zoologist, Robert Grant, who had cited Erasmus Darwin's work in his Ph.D. thesis, went to Paris to study and was befriended by the elder Geoffroy Saint-Hilaire. He returned to Edinburgh University (and subsequently London) to become the leading British exponent of Lamarckian evolution theory. He was a radical, an atheist and, allegedly, a homosexual. Though he published many academic papers, he never published any popular books and his career was hampered by the intervention of anti-evolutionists.
We now come on to the young Charles Darwin, who read his grandfather's works in his youth and was thus well primed to become an evolutionist. He then went to Edinburgh University to study medicine and was befriended by Grant, who tried to convince him of the veracity of Lamarckian evolution. Darwin was unconvinced then, but it must have sowed the seeds of doubt in his mind and prepared him for his future conversion. Under Grant's tutelege, Darwin read a book by a Swiss-born French botanist, Augustin de Candolle, who had worked with Lamarck. The 1820 book, "Essai Elementaire de Geographie Botanique", contained the following passage:
All the plants of a given country are at war one with another. The first which establish themselves by chance in a particular spot, tend, by the mere occupancy of space, to exclude other specie - the greater choke the smaller, the longest livers replace those which last for a shorter period, the more prolific gradually make themselves masters of the ground, which species multiplying more slowly would otherwise fill.
Though Darwin would not provide proof that he had read that passage till 1842, one person who certainly had noticed it was the Scottish geologist, Charles Lyell, whose Uniformitarian geology clearly refuted Biblical literalism, due to its view of gradual changes over vast eons of time. That left open to question the issue of how species came into being, and Lyell was very interested in the subject. He had read Lamarck's "Philosophie Zoologique", but, as a religious man, he had not been able to go along with its atheistic implications. In the 2nd Volume of his hugely influential "Principles of Geology", published in 1832, Lyell not only included an extensive critique of Lamarck's theory but also his own interpretation of de Candolle's views:
Unhealthy plants are the first which are cut off by the causes prejudicial to the species, being usually stifled by more vigorous individuals of their own kind. If therefore the relative fecundity and, or, hardiness of hybrids be in the least degree inferior, they cannot maintain their footing for many generations, even if they were ever produced beyond one generation in the wild state. In the universal struggle for existence, the right of the strongest eventually prevails, and the strength and durability of a race depends mainly on its prolificness, in which hybrids are known to be deficient.
On the Voyage of the Beagle, Charles Darwin not only had with him, and frequently cited, Lamarck's "Histoire Naturelle des Animaux sans Vertebres" but also had sent to him, and read, the 2nd Volume of Lyell's "Principles of Geology". So his conversion to evolution during that voyage could have been as much due to what he was reading on board as to what he was observing on land. He was well steeped in Lamarck's evolution theory while he was on the Beagle.
On his return to England, Darwin became friends with Lyell, as they had similar interests in geology and natural history. In 1837, possibly on Lyell's recommendation, Darwin read a book about the Canary Islands by a German geologist, Leopold von Buch, who was Lyell's great rival and whose naturalist friend, Alexander von Humboldt, was also a friend of Goethe's. What particularly impressed Darwin was a passage in which von Buch expresses the belief that, in geographical isolation, species change to the point of becoming different species:
On continents the individuals of one kind of plant disperse themselves very far, and by the difference of stations of nourishment & of soil produce varieties which at such a distance not being crossed by other varieties and so brought back to the primitive type, become at length permanent and distinct species. Then if by chance in other directions they meet with another variety equally changed in its march, the two are become very distinct species and are no longer susceptible of intermixture.
That was exactly what Darwin had felt on the Galapagos Islands. It was only corroborative evidence though, since he was by then convinced about the truth of evolution.
He still wasn't satisfied by Lamarck's mechanism though, and the views of de Candolle and Lyell on the struggle for existence had not caused him to see the light. Like everyone else, he had also missed an article by a Scottish-American physician, William Charles Wells (who is not included in the chart because he had no influence), who believed that all the different human races had arisen from common stock and thrived (or otherwise) according to their suitability to the environments they inhabited. (See Darwin essay)
Though Darwin would much later claim that it was the doctrine of Thomas Malthus that gave him the mechanism of natural selection in late 1838, it is now well established from Darwin's notebooks that, by early 1838, Darwin had read two articles by an amateur ornithologist, Edward Blyth. As one of the many readers of Lyell's "Principles of Geology", Blyth was clearly of the view that competition and survival were paramount in nature. Though Blyth was not a total evolutionist, he did believe that varieties were produced by natural changes, which proliferated if they aided survival and reproduction within the inhabited environment, and were eliminated if they didn't. Like Erasmus Darwin, Blyth had clearly got the gist of sexual selection too, as demonstrated by this passage from his 1835 article:
When two animals are matched together, each remarkable for a certain given peculiarity, no matter how trivial, there is also a decided tendency in nature for that peculiarity to increase; and if the product of these animals be set apart, and only those in which the same peculiarity is most apparent, be selected to breed from, the next generation will possess it in still more remarkable degree; and so on, till at length the variety I designate a breed, is formed, which may be very unlike the original type.
It is worthy of remark, however, that the original and typical form of an animal is in great measure kept up by the same identical means by which a true breed is produced. The original form of a species is unquestionably better adapted to its natural habits than any modification of that form; and, as the sexual passions excite to rivalry and conflict, and the stronger must always prevail over the weaker, the latter, in a state of nature, is allowed but few opportunities of continuing its race. In a large herd of cattle, the strongest bull drives from him all the younger and weaker individuals of his own sex, and remains sole master of the herd; so that all the young that are produced must have had their origin from one which possessed the maximum of power and physical strength; and which, consequently, in the struggle for existence, was the best able to maintain his ground, and defend himself from every enemy.
In like manner, among animals which procure their food by means of their agility, strength or delicacy of sense, the one best organized must always obtain the greatest quantity; and must, therefore, become physically the strongest, and be thus enabled, by routing its opponents, to transmit its superior qualities to a greater number of offspring.
Darwin must have been influenced by Blyth's views, but he chose not to acknowledge anything other than factual information. The best accolade he ever gave to "Mr Blyth, whose opinion, from his large and varied stores of knowledge, I should value more than that of almost any one" falls far short of saying that Blyth had unwittingly handed him natural selection on a plate. The person Darwin did acknowledge - Malthus - was a long-dead clergyman, whose warning about the dire consequences of population increase - death of the weakest - could be construed as an attempt to dissuade people from engaging in practices which resulted in reproduction.
One other person I have included in the chart is the Scottish arboriculturist, Patrick Matthew, who had outlined his belief in evolution by a 'natural process of selection' in 1831. Though Darwin claimed not to have known about him till 1860, there is a considerable amount of evidence that Darwin did know about him, possibly as early as 1837. For the full story, see separate essay on "Darwin's Guilty Secret". The contributions of Robert Chambers, Herbert Spencer and Alfred Wallace came too late to have been influential on Darwin's thinking.
It can be seen from the above extracts that Darwin's great contribution to science was not so much as a revolutionary original thinker, as he is often portrayed, but rather as a methodical and meticulous plodder, who spent 20 years accumulating the necessary evidence to present a well-argued case for the theory he had put together from other people's ideas. They deserve recognition too.