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rasmus Darwin's evolutionary ideas owe something to the discovery, in 1767, of mammoth bones in the course of digging a tunnel for the Grand Trunk Canal at Harecastle near Kidsgrove, Staffordshire. Recognizing that they did not relate to any known species, Josiah Wedgwood passed the bones to Darwin along with a request for his opinion. Darwin thought the bones must belong to an extinct species, an insight that led him to the general conclusion, in 1769, that organisms have evolved through time; and his concurrent conjecture that all organisms share a common ancestor — what he termed a "single filament" — formed in water by natural processes.

It is difficult to overstate the dangerousness of these views during the eighteenth century. As early as 1720, the French mathematician and natural philosopher Pierre Louis Maupertuis (1698-1759) had theorised that life had originated spontaneously in warm shallow water, a view that was not published until 1760, a year after his death. Darwin, who was probably aware of Maupertuis, echoed these ideas in his poem Economy of Vegetation (1791), in which he described life originating through natural processes in warm water. Just as Maupertuis had been cautious about broadcasting his ideas for fear of provoking a negative reaction, so Darwin was also reluctant to let others know too clearly of his views. He did, however, memorialize them in his family coat of arms. To the original design of three scallop shells, he added the motto: E conchis omnia, that is, Everything from shells. The coat of arms was painted on the doors of his coach and printed on his bookplate. When his neighbour in Lichfield cathedral close, one canon Seward, understood the meaning of the design, he urged Darwin to remove the emblem from public view. Darwin complied, realizing that if he were to make his ideas too well known, he would be in real danger of alienating his patients and thereby losing his source of income. Perhaps as a result of these pressures, he also delayed writing his medical treatise, in which he described his evolutionary ideas in prose, until 1793. The delay anticipates his grandson Charles' twenty-year delay in publishing his book on natural selection, which he, too, withheld in part for fear of a negative reaction.

In an extended essay appearing in the first volume of Zoonomia (1794; vol. 2, 1796), Darwin described, for the first time in English prose, the idea of the spontaneous generation of life by physico-chemical means in water. “[I]t appears that all animals have a similar origin, viz. from a single living filament," he wrote. (498) "All animals therefore, I contend, have a similar cause of their organisation, originating from a single living filament." (499)

Darwin believed not only that that animals had a common ancestor, but also that all life had a common ancestry. After describing different kinds of animals, he asked,

Shall we then say that the vegetable living filament was originally different from that of each tribe of animals above described? And that the productive living filament of each of these tribes was different originally from each other [...] [S]hall we conjecture, that one and the same kind of living filaments is and has been the cause of all animal life? (507)

In a passage which has often been overlooked, Darwin next argued that the initial living filament for each specific creature is to be found in all parts of the creature:

All animals therefore, I contend, have a similar cause of their organisation, originating from a single living filament, endued [sic] with different kinds of animal appetencies; which exist in every gland, and in every moving organ of the body, and are as essential to living organisations as chemical affinities are to certain combinations of inanimate matter. (499)

This passage suggests that Darwin understood the presence of what, in modern language, might be called DNA. Eighteenth-century knowledge did not, of course, extend to the molecular level in cells, but it seems Darwin appreciated that something similar must be present in all parts of organisms and that this element differentiated animated matter from inanimate. In distinguishing between organisms and non-organic matter, he implicitly rejected an idea, common at the time and which has persisted since, that organisms are fundamentally machines, or that they can be regarded as mechanical entities.

He identified three causes of changes to the morphology of living organisms: lust, hunger, and survival. In his discussion of lust, he linked sexual drive to the possession of physical attributes that, because they serve an individual's reproductive purpose, tend to persist. Thus, males of some species desire

the exclusive possession of females; and these have acquired weapons to combat each other for this purpose. [...] So the horns of the stag are sharp to offend his adversary, but are branched for the purpose of parrying or receiving the thrusts of horns similar to his own, and have therefore been formed for the purpose of combatting other stags for the exclusive possession of the females. The final cause of this contest among the males seems to be, that the strongest and most active animal should propagate the species, which should thence become improved. (503)

In this sentence "final cause" should be understood in the Aristotelean sense of the purpose for which something happens, in this case, sexual selection in at least the negative sense, that is, less adaptive traits fall out of populations over time.

According to Darwin, the necessity "of procuring food" had "diversified the forms of all species of animals." He described how pigs had hard noses to grub in the ground, elephants have trunks to reach branches and leaves, cattle have rough tongues to pull grass, and birds have a variety of beaks: "Some birds have acquired harder beaks to crack nuts, as the parrot. Others have acquired beaks to break the harder seeds, as sparrows. Others for the softer seeds of flowers, or the buds of trees, as the finches. . . All which seem to have been gradually produced during the many generations by the perpetual endeavour of the creatures to supply the want of food" (504).

Darwin also described how animals had acquired different forms for purposes of self-defense, either by running away from enemies or by concealing themselves:

Some have acquired wings instead of legs, as the smaller birds, for the purpose of escape. [...] Others great swiftness of foot, as the hare. Others have acquired hard or armed shells, as the tortoise and the amphibious Echinus marines [...] The colours of many animals seem adapted to their purposes of concealing themselves either to avoid danger, or to spring on their prey."(p504 and p509).

Darwin noted that birds laid eggs of different colours according to what colour was most protective in their surroundings. Birds nesting in hedgerows laid green eggs; those whose nests who tended only to be seen from below, like crows and magpies, laid blue or white eggs; in the case of ground nesting birds, Darwin observed, the eggs were grey or brown. (510) In these passages, Darwin was describing the results of natural selection.

He also understood mimicry as a form of protection, as in the case of the "frog-fish, Lophus histrio, which inhabits large floating islands of seaweed above the Cape of Good Hope, and has fulcra resembling leaves, that the fishes of prey may mistake it for sea-weed, which it inhabits."

Recognising anatomical structures common to all warm-blooded animals, Darwin concluded by returning to his conjecture of the "living filament":

From thus meditating on the great similarity of the structure of warm blooded animals, and at the same time of the great changes they undergo both before and after their nativity; and by considering in how minute a portion of time many of the changes of animal above described have been produced; 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 [...] with the powers 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 posterity, world without end? (505)

He drew his readers’ attention to frogs and butterflies, which undergo metamorphosis as part of their life cycles. He also pointed out how some animals have been changed by "accidental or artificial cultivation, as in horses, which have exercised for the different purposes of strength or swiftness, in carrying burthens or in running races." (500) He supplied a list of animals — pigeons, dogs, cattle, sheep and camels — which had been modified by cross-breeding to better suit the needs of breeders. He also noted that unique features, such as unusual size, could be inherited: "Many of these enormities of shape are propagated, and continued as a variety at least, if not as a new species of animal. I have seen a breed of cats with an additional claw on every foot; of poultry also with an additional claw, and with wings to their feet." (501)

Darwin did not know what "powers" caused organisms to acquire new parts over time, but he clearly recognised that such changes have taken place, and in doing he disagreed with the majority of his contemporaries. Later Cuvier, Lamarck, Geoffroy and Richard Owen would discuss similar anatomical structures to argue for and against transformism, as evolution was called in the early decades of the nineteenth century. Although his belief in "irritations, sensations, volitions, and associations" as causes of change within organisms was vague, it can be compared with Lamark's later suggestion of an organism's "incidental need" or "modifying cause," which also failed to explain how any change originated or grew. Eventually Darwin's view of the relation between form and function became an important line of evidence for the fact of evolution. His ideas and many of his examples re-appeared in volumes published after 1859 by his grandson, Charles.

Like his contemporaries who believed in natural theology, Darwin was clearly an adaptationist, but unlike most modern biologists who support adaptationism, he never used terms such as design, mechanism, or other terms borrowed from physics or engineering when referring to organisms or living entities. The key difference between Darwin and his theologian contemporaries was that he was an atheist and a materialist by the time he came to write Zoonomia. Darwin presented natural theology without God, inverting the adaptationist ideas of natural theology to which he added the idea of self-organisation and common ancestry, thereby anticipating ideas which were not to be widely discussed until nearly two hundred years later. He suggested that all changes within the physical universe were caused by natural processes. He understood that organisms interact with each other and undergo changes in so doing. Although he did not understand the world as a global system, he realised that local communities had to be recognised as greater than the sum of their parts.

Despite the dangerousness of its author's ideas, Zoonomia was a great success. It was translated into German, French and Italian, and it was also published in an American edition. Zoonomia even appeared on the Index of books prohibited to Roman Catholics by the Pope. It may have influenced the great French evolutionist Jean-Baptiste de Lamarck, who began teaching courses on evolution in 1802: King-Hele avers that it influenced Lamarck's Philosophie Zoologique (1809). More than a few of Lamarck's observations, such as of the enlarged muscles of blacksmiths, appeared in Zoonomia. By the end of the eighteenth century, Darwin's ideas had propagated widely through educated circles across Europe and North America, and continued to do so well into the nineteenth century.

Darwin, who was interested in agriculture and increasing food supplies by cross breeding plants and animals, borrowed the term natural selection from breeders. In 1800, he published the last of his prose works Phytologia; or the Philosophy of Agriculture and Gardening. This book, which he organized in three parts, included important discoveries and descriptions. In the first part, he further discussed sexual selection with respect to plants and described how different types of seeds are dispersed (113). He showed how plants breathe through holes in their leaves by covering the undersides of some in wax which then died, although the pores under leaves were not discovered until the nineteenth century. He recognised that plants make sugar, which is an important food source for many forms of life, both plant and animal. In part II, he wrote: "This carbonic gas (carbon dioxide)….is the principal food of plants…..Next to carbonic acid …. water seems to afford the principal food of vegetables…. when vegetable leaves are exposed to the sun's light, they seem to give up oxygen gas" (193-194). Here Darwin described the process of photosynthesis for the first time, for although others had recognised different parts of the process, he was the first to describe it as a complete system. He explained that in order to grow plants need nitrogen, phosphorus, carbon, and calcium, advocating that these elements should be regularly added to cultivated soils in order to maintain their fertility, to increase crop and animal yields, and to improve the their quality. He also proposed sewage farms to transform human waste into manure that could be used in fields; and that tape-worms be introduced to help control rat populations, among other ingenious ideas.

In Part III of Phytologia, which dealt with fruits, trees, root crops, and the uses of bark, leaves, and the wood of trees, points to the savagery of nature: "Such is the condition of organic nature! whose first law might be expressed in the words, "Eat or be Eaten!" and which would seem one great slaughter-house, one universal scene of rapacity and injustice!" (556) Later Herbert Spencer was to express similar views, and Tennyson described "Nature, red in tooth and claw." His grandson Charles would also be reminded of these words when he witnessed the extravagant life in the rain forests of South America. Unlike some later commentators, Darwin did not hold views that were uniformly or unremittingly dark. Rather, he believed that animal activities were in part directed towards pleasure. Unconstrained by the theological frameworks typical of clergymen and other believers of his day, Darwin developed an interpretation of life that was different to his more conservative contemporaries Paley and Malthus: he did not believe that the amount of pleasure in the world was balanced by the amount of pain.

Evolution was a popular idea in the nineteenth century among political and social radicals in many countries other than Britain, and Darwin's and Lamarck's names were associated with it. But the idea of evolution remained an anathema to social and political conservatives for decades. Both Darwin and Lamark were considered heretics because conservatives believed that evolution called into question both the Creation and the existence of God. Believing that the world had been created by God, they found any suggestion of natural change blasphemous; and social change was accordingly impossible to imagine. After the revolution of 1789, the French government effected a clear separation between Church and state, and advocated a society in which benefits were distributed on a meritocratic rather than hereditary basis. In Britain and elsewhere, conservatives observing these developments associated the godlessness of evolutionary ideas with violent revolution.

References

Darwin, Erasmus. The Botanic Garden, Part II: Containing the Loves of the Plants, a Poem: with Philosophical Notes. London: Joseph Johnson, 1789.

Darwin, Erasmus. The Botanic Garden: A Poem in Two Parts, Part I: Containing the Economy of Vegetation London: J. Johnson, 1791.

Darwin Erasmus. Zoonomia; or the Laws of Organic Life. 2 vols. London: J. Johnson, 1794-96; rev. 1801.

Darwin, Erasmus. Phytologia: or the Philosophy of Agriculture and Gardening. London: J. Johnson, 1800.

Darwin, Erasmus. The Temple of Nature, or The Origins of Society. London: J. Johnson, 1803.

Fara, P. Erasmus Darwin: Sex, Science and Serendipity. Oxford: Oxford University Press, 2012.

King-Hele, D. Doctor of Revolution, The Life and Genuis of Erasmus Darwin. London: Faber and Faber, 1977.

King-Hele, D. Erasmus Darwin: A Life of Unparalleled Achievement. London: Giles de la Mare Publishers, 1999.

King-Hele, D. Erasmus Darwin and Evolution. Sheffield: Stuart Harris, 2014.

Lamarck, Jean-Baptiste. Philosophie Zoologique. 2 vols. Paris: Dentu, 1809.


Last modified 31 March 2018