The Origin of Species

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    In 1859 Charles Robert Darwin (1809 Feb 12 – 1882 Apr 19) published one of the best-known and least-read books in science. In that book he laid out a theory that he had begun developing in the early 1830's when he had become a de facto naturalist on His Majesty’s Ship Beagle (he originally joined the expedition as a dining companion for the ship’s captain, Robert FitzRoy).

    Originally intended to become a Doctor of Medicine, like his father, Darwin served as an apprentice to his father in the summer of 1825 (when he was only sixteen) and helped the elder Darwin treat the poor people of Shropshire. In October of that year Darwin went with his grandfather Erasmus to Edinburgh to learn medicine at the university. There he discovered that the lectures bored him and that he had no stomach for surgery.

    Darwin did learn at Edinburgh that he had a strong interest in natural history. He learned taxidermy from a freedman who had learned the skill in the rainforest of South America and enjoyed the company of that black man, whom he described as "very pleasant and intelligent". He also joined the Plinian Society, a group of students who devoted themselves to the special study of natural history. He also served as an assistant to Robert Edmund Grant in the latter’s study of marine invertebrates in the Firth of Forth, making discoveries of his own in the process: in March 1827 he stood before a meeting of the Plinian Society and described his discovery that black spores that he found in oyster shells were the eggs of a skate leech. He also assisted in the work organizing the collections of the University Museum.

    Eventually Darwin’s neglect of his medical studies led his father to send him to Christ’s College at Cambridge in January 1828. There he would obtain a Bachelor of Arts degree, the first step toward becoming an Anglican parson. At Cambridge Darwin continued to pursue his interest in natural history. He became a close friend of Reverend Professor John Stevens Henslow (1796 Feb 06 – 1861 May 16), Professor of Botany who was also a geologist. It was Henslow who got Darwin his berth on the Beagle.

    As to his studies, Darwin enjoyed reading William Paley’s "Evidences of Christianity" and "Natural Theology", taking delight in Paley’s use of language and logic. In January 1831 Darwin passed his final examination at the position of tenth out of 178 men passing the exam. In November of that year Henslow sent him a letter proposing that he join the Beagle expedition as a gentlemanly companion for Captain Robert FitzRoy.

    The post Darwin filled was no triviality. The stress and loneliness of long sea voyages at that time led a number of ships’ officers to commit suicide to escape the depression that overcame them. Indeed, on Beagle’s first voyage of survey Flag Lieutenant Robert FitzRoy was made captain when Beagle’s first captain, Pringle Stokes killed himself.

    His Majesty’s Ship Beagle left Plymouth on the day of 1831 Dec 27 to continue the South American Survey that Captain FitzRoy had begun on her first voyage (1826 May 22 – 1830 Oct 14). Originally built as a ten-gun brig-sloop, Beagle had been reconfigured as a six-gun survey barque. Beagle returned to England at the port of Falmouth on the day of 1836 Oct 02.

    The Admiralty had sent Beagle to explore the coast of South America (the Galapagos Islands were a mere stopover). In addition to mapping the coast and the nearby seascape, the survey included the tasks of studying the flora and fauna of the region. In Argentina, in pursuit of those goals, Darwin found fossils that resembled the skeletons of present-day mammals, such as that of the giant sloth and the glyptodont, which resembled the armadillos he saw on the pampas. He also noticed two species of Rhea, the greater rhea living almost exclusively north of Argentina’s Rio Negro and the lesser rhea (originally called Rhea darwinii) living almost exclusively south of the Rio Negro. That fact later offered a clue to the process of evolution, descent with modification. Only after he returned to England did Darwin add the Malthusian struggle for existence to his evolving concept of the origin of species. But he certainly had the foundation of his theory, as he pointed out in the opening sentences of his great work, "When on board H.M.S. ‘Beagle’, as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent. These facts, as will be seen in the latter chapters of this volume, seemed to throw some light on origin of species – that mystery of mysteries, as it has been called by one of our greatest philosophers."

    From 1837 onward Darwin labored to put his data together into some kind of coherent pattern. By 1844 he had a clear enough picture of evolution by means of natural selection that he began showing it to friends and colleagues. Perfectly aware of the intellectual tinder that he had piled around himself, he resisted publishing his work, arguing that he was still putting together the grand treatise that it required and perhaps intending, like Copernicus before him, to have it published only upon his death. He only had it published when he did, and only as an abstract of the full treatise, because he was compelled to do so by an inadvertent challenge from Alfred Russell Wallace (1823 Jan 08 – 1913 Nov 07).

    On the day of 1859 Nov 24 Darwin had "The Origin of Species by means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life" published. His friends had urged him to do so when they became aware that Alfred Russell Wallace had sent Darwin a manuscript presenting an essentially identical theory of life, asking Darwin to pass it on to Charles Lyell for publication in The Journal of the Linnaean Society (which Darwin did). Darwin thus produced what he called an abstract, comprising 670 pages of text, a 14-page Historical Sketch, a 16-page Glossary, and a 17-page Index. He produced the book in some haste, in order to have it published more or less simultaneously with Wallace’s paper. He had originally presented a sketch of his hypothesis to a number of learned men in 1844 to get their opinions on it and then had begun converting that sketch into a formal treatise. Goaded by Wallace, Darwin wrote "The Origin of Species" as an abstract of that treatise. The effort necessary to trudge through a reading of "The Origin of Species" tells us how glad we must feel that Darwin never got around to completing that treatise.

    Following a brief introduction, in which he summarized his inspirations and the basic ideas underlying his hypothesis, Darwin began his book with a review of artificial selection. He pointed out that over the span of human history, and often within a single human lifetime, breeders, both deliberate and accidental, had wrought substantial changes in the forms of various animals and plants. Having bred the birds himself, he devoted a long section of his first chapter to pigeons as an illustration of what artificial selection can accomplish.

    But if breeders can produce over historic time the kinds of changes that we see reflected in the various breeds of dog, for example, then how great and how profound are the changes that selective breeding can yield over geologic time, whose depth people were just beginning to understand in 1859? Even though the science of the time contained no knowledge of genetics and Darwin’s own understanding of the basis of heredity stood false to Reality, Darwin extrapolated from what he did know for certain. If someone were to take some species, divide it into two populations, and keep those populations separate from each other, then different sets of changes will accumulate in those populations. At some time enough changes will have accumulated that the two populations will reach a point of no return, a time after which the two populations can no longer interbreed. Two separate varieties will have thus become two separate species.

    Darwin then had to confront the question of what selects the traits that will become part of a transformed species. To answer that question Darwin provided what no one had offered before. He drew inspiration from "An Essay on the Principle of Population", which the Reverend Thomas Robert Malthus (1766 Feb 13 – 1834 Dec 23) had published in six editions over the span from 1798 to 1826. In that essay Malthus described the fundamental challenge facing Humanity as residing in the fact that the growth of population will always exceed the growth of the resources necessary to support it. Darwin understood that Malthus’ law applies to all life-forms and from that understanding conceived the idea of the struggle for existence. In that Malthusian struggle, Darwin then asserted, the process of natural selection shapes the species through the survival of the fittest (which infamous phrase Darwin used as part of the title of Chapter IV), which means that those individuals that fit their environment best will tend to reproduce themselves more than will those who fit the environment less well.

    Having thus laid out his hypothesis, Darwin then discussed a number of difficulties that he had conceived as troubling the hypothesis and some other objections to it. Chief among the difficulties that he conceived stood the observation that we see distinct species and, apparently, no transitional forms. He then noted that natural selection operates primarily as a process of subtraction. A species changes as the individuals most like the original species die out faster and those most unlike the original species reproduce themselves faster; thus, a species changes in large part by the extinction of the transitional forms.

    Darwin then piled on the evidence to support his hypothesis (and at that point, strictly speaking, it did not yet deserve to be called a theory). He especially referred his readers to the still sparsely explored fossil record, noting that many fossils resemble the skeletons of still living creatures, an observation that he had made himself when he visited South America on the Beagle expedition. He then discussed classification and embryology as natural selection applies to those areas of study. By bringing in evidence from a wide variety of fields of study Darwin not only provided preliminary support for his hypothesis, but also established natural selection as a basic principle around which all of the life sciences could accrete into a unified discipline, modern biology.

    Finally, like a lawyer facing a jury, Darwin summed up his case. Referring to his book as "one long argument", he repeated briefly its main points, objections, and evidence. He discussed the potential width of its application in science. And then he ended his abstract with one of the best-known paragraphs in all of scientific literature:

    "It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved."

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