On the Origin of Species: Why Did Charles Darwin Write It?

Charles Darwin was well aware that both he and his family would be lambasted because of On the Origin of Species; so what drove him to write it at all?

Sep 3, 2022By Thea Baldrick, BS Biology w/ Molecular & Cellular Biology Concentration, BA Comparative Literature



When Charles Darwin was a young man, life on Earth was thought to be complete and unchanged since the beginning. The concept Special Creation was an especially entrenched idea in the early nineteenth century. Furthermore, human beings were particularly separate in the physical scheme of life. Darwin’s theory as it was eloquently explained in On the Origin of Species and subsequent publications chipped away at that belief. The backlash was considerable.


Before the Origin of Species: Science in Darwin’s Youth


Initially, Darwin disagreed with the concept of life evolving. Evolution was posited by a long line of intellectuals, beginning with Aristotle and including his own grandfather, Erasmus. Regardless, in Charles’ student days, he adhered to the traditional canons of theology. Indeed, there were many problems with evolution. Most significantly, it required vast amounts of time and, even within the realms of scientific thought, the Earth was just not that old.


Many thought the Earth to be slightly less than six thousand years old as determined by Bishop Ussher in the seventeenth century. Others allowed for tens of thousands or even hundreds of thousands years. Nevertheless, there were seeds of dissent. The study of geology presented progressively more evidence that the timespan involved in developing the landscape was immense.


roger bacon engraving 1867
Roger Bacon, by Jan Verhas, 19th century, via Wikimedia Commons


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It was also obvious that artificial selection among domesticated species can and did occur.  Roger Bacon in the seventeenth century noted that farmers often selected or bred the next generation of produce or livestock based on desired characteristics. If fatter pigs were wanted (and they usually were), or bigger corn cobs (and they usually were), the fattest pigs were bred together or corn kernels from stalks with larger corn cobs were planted. The different breeds of dogs were fast diversifying, too, by the same process.


After species was defined as that which produced similar plants and animals, Carl Linnaeus began his systematic categorization in the early eighteenth century. “Like begets like ” needed to be spelled out because there was a widespread belief in the spontaneous birth from the earth. It was also commonly believed that two completely different animals could mate, thereby creating a deformed creature or a chimera.


Erasmus Darwin, a key figure in the Enlightenment, suggested that all animals evolved.  His ideas were echoed and furthered by Jean-Baptiste Lamarck. Lamarck posited that animals developed traits during their lifetime based on the pressures of the environment, outcompeted others in their species, and then passed the traits along to their offspring. Lamarck suggested that an individual giraffe grew a longer neck to reach for higher leaves and bequeathed the next generation with longer necks. This was wrong, but the idea of evolution based on the surrounding conditions and competition had gained a foothold in the thoughts of academicians.


Thomas Malthus’ ideas on overpopulation, which Darwin read soon after his voyage, had also taken hold. Most plants and animals produced far too many progeny; but the consequences of the environment, such as lack of food, wars, disease, and predation, thinned the ranks.


Darwin’s Education

charles darwin seated as young man by richmond
Charles Darwin by George Richmond, 1830s, via Wikimedia Commons


Due to his father’s insistence, Charles attended medical school in Edinburgh. While he was there, he learned of various theories about the formation of the Earth. Hutton, a self-made man posited that a series of small events, over long stretches of time, created the world as it was then known. Labeled Uniformitarianism, the hypothesis required vast amounts of time to form features such as mountains.


Although the seeds of scientific analysis were sown in Edinburgh, Darwin was literally unable to stomach completing his medical degree. Upon witnessing surgery upon a child, necessarily at that time performed without sedation, Darwin left and would not return.


Next, he went to Cambridge in order to become a vicar. Adam Sedgwick, a prominent geologist was a crucial influence. In addition, Charles became a passionate beetle collector after attending a lecture by a famous botanist, the Reverend George Henslow. From Henslow, he developed crucial skills, most importantly, that of drawing conclusions from many observations. Henslow was an enthusiastic mentor who eventually recommended Darwin to the naturalist post on the Beagle.


Something of a wastrel with the required theological curriculum, Darwin nevertheless managed, with intensive last-minute studying, to graduate with his degree.  Surprisingly, most of all to himself, he placed tenth in his graduating class. The next step was to find a post as a vicar. The Beagle intervened.


The Voyage That Changed Darwin’s Life

map voyage charles darwin beagle
Map of the Voyage of Charles Darwin 1831 -1836, via university of Illinois


After fielding his father’s concerns and meeting favorably with Captain FitzRoy, Darwin was hired as the naturalist on board the Beagle. FitzRoy’s main responsibility was to survey the waters around South America and across the Pacific. Initially only supposed to last three years, the journey on the Beagle lasted five, from 1831 to 1836. During that time, Darwin spent much more time on land than he did at sea.


The notes Darwin took on the voyage were highly detailed and indicated concentrated knowledge on a vast array of scientific topics. He wrote a popular book on the voyage upon his return which is still well-published today. In the book, he mentions his own experiments and observations and often references others’ works. The result was a compendium of information about the flora, fauna and geology of South America written with an engaging style.


While on board, he read Lyell’s first two volumes of Principles of Geology which argued for Uniformitarianism and the long times spans involved. Darwin found much evidence to back up Lyell’s ideas and wrote back to England highlighting his observations. Lyell himself eventually became Darwin’s friend and supporter, even as he refused to accept that Darwin’s ideas on evolution could be applied to human beings.


Darwin collected and sent back to England numerous collections of animals, plants, and fossils never seen before in Europe. The famous finches, which he used as an example of diversification, in his most famous book, were not, in fact, finches, but a type of tanager. Upon his return to England, Darwin teamed up with John Gould, a noted ornithologist, to identify them.  The most striking feature of the birds are the beaks that vary from island to island. The variation in beaks fueled Darwin’s realization that physically separating a species could fuel diversification and eventually create an entirely separate species.


Back to England

frontispiece principles of geology charles lyell
Frontispiece of Principles of Geology by Charles Lyell,1857, via Wikimedia Commons


When he first returned to England in 1836, it was obvious that he no longer needed to follow the vicar’s path in order to have a career. His letters had, in his absence, created a furor of interest among the scientific community; but it was not in biology that he first became famous. It was geology.


Along with several astonishing fossils, he presented to the Geological Society his evidence of extinct sea life in the mountains of South America 14,000 feet above sea level. Additionally, he recounted his experience of the land being raised eight feet after an earthquake there. His observations demonstrated that over long periods of time, land on the bottom of the sea could be raised to mountain tops just as Lyell had suggested.


Furthermore, his hypothesis on coral reefs was especially compelling, presenting a new idea to the scientific community. Coral reefs that needed sunlight formed on top of dying coral reefs as an island sank back into the sea; therefore, the land was not only being raised in some places but it was sinking in others.


Building a Base to Present His Theory

charles darwin home shere wrote on origins of species
Photograph of Down House, via Country Life Magazine


From evidence in his diaries, by 1837 Darwin had begun to develop his ideas on evolution; but the social and political climate was a problem. In the 1830s and 40s, England was in upheaval. The working classes wanted more rights as citizens. In the early part of their marriage, the Darwins lived in London where much of the violent protests occurred. Although Darwin was a Whig and sympathetic to the plight of the protesters, it was neither a suitable atmosphere to raise a family nor to introduce a controversial theory that would have been immediately politicized. The couple and their young children bought a house in the country, Down House, where Darwin spent the rest of his life and wrote his most famous works.


Darwin was also entirely aware that the kickback based on religious dogma was likely to be severe, even in his private life. He had married his cousin, Emma Wedgeworth, with whom he discussed his ideas on natural selection before he proposed. She obviously cared for him deeply but throughout their life together was deeply concerned about the state of his soul. She was afraid that his beliefs would preclude them from spending eternity together after death. Her concerns mattered to him even though he did not share them. He also had a growing family, seven out of ten survived to adulthood, and a respected position in the scientific community.  Both positions gave him reason to postpone publishing.


charles darwin photograph
Charles Darwin, print made by C. Kiven after Maull, 1860-1882, via British Museum


Nevertheless, the more research he conducted the more firmly he believed that his concept on natural selection was correct. In addition, Darwin felt his credentials as a biologist needed a boost. He was viewed by his colleagues as a geologist. The last thing he wanted was for his ideas to be dismissed because he was reaching too far out of his field. Consequently, he began a protracted study of barnacles, the results of which strengthened his assurance in the validity of natural selection. He found both hermaphroditic barnacles, with both sex organs, heterosexual barnacles, and several intermediate forms where the male, or several males, was attached to the female.  He called them “little husbands.” After eight years on the study and classification of barnacles, he had established that variation was not the exception in nature, but the rule.


By the 1850s, society was changing. Industry fueled the second half of the century in England and its cultural offshoots. The wealth and jobs the technology brought also opened the minds of the public to the value of new ideas. Darwin’s friends began to push him to publish. Lyell, in particular, was concerned that Darwin would be preempted.


The Final Push: Alfred Russel Wallace

alfred russel wallace photograph
Photograph of Alfred Russel Wallace, via Natural History Museum, London


By 1854, with the change in intellectual atmosphere and now firmly established as both a geologist and a biologist with numerous books in both fields, Darwin began to organize his notes and in 1856 began work on a large book about his grand theory. He was in no hurry, but on June 18th, 1858, he received a shocking letter from Alfred Russel Wallace. Darwin had corresponded with Wallace before. In fact, Darwin had even purchased specimens from the younger man and evolution had been broached in their letters. Wallace was a specimen collector, selling the results of his worldwide search to wealthy collectors in order to fund travels and his own passion for biological science.


Wallace’s paper was, to all intents and purposes, the same as Darwin’s. They were so similar that some of the very phrases Darwin used in his book reappeared with small variation in Wallace’s paper.


Darwin wanted to relinquish all honors to Wallace, but Darwin’s colleagues talked him out of it. A joint presentation with Wallace’s paper, Darwin’s 1844 outline and a letter from 1857 in which Darwin propounded his theory to another colleague, was presented on July 1, 1858 at the Linnean Society. Neither Wallace nor Darwin attended. Wallace was still on the other side of the world on the Malay Archipelago and Darwin’s tenth child died from scarlet fever on June 28th at a year and a half years old.


On the Origin of Species: The Theory of Natural Evolution

on the origin of species charles darwin first edition
Title page of On the Origin of Species by Charles Darwin, 1859, first edition, via the Library of Congress


At its most simplistic, natural evolution is based on two points: variation and speciation.  Variation means that offspring are not exact copies of their parents. Slight variations exist.  Selection means that the environment removes life forms that are not as well suited to the world it finds itself in.


Survivors, those with the variation that help it outcompete the others in its species, reproduce.  The offspring have more of the traits that permitted their parents to survive, but again those have variation.  As the environment fills, competition becomes more fierce.


Darwin did not show that evolution in general could occur among species.  That concept was already well established by agriculture. Darwin showed why evolution occurred in the natural world. The environment selected the most favorable versions to survive.


collier charles darwin painting
Charles Darwin, copy by John Collier, 1883 based on a work of 1881, via National Portrait Gallery


In retrospect, there was a certain obviousness to the process of natural selection, and a degree of beauty, despite its harshness. Natural selection is beautiful in the way that a balanced, mathematical equation is beautiful. In the words of Darwin himself at the conclusion of the On The Origin of Species,


“There is a 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.”


On the Origin of Species continues to benefit mankind and the world it lives in as its tenets are put into place in applications ranging from medicine to environmental science. Why Charles Darwin wrote his theory on natural selection is no different than why natural selection itself takes place. As a species adapts to its world, the traits—and the ability to reason accurately are clearly traits—that provide the best information enhance survival.


Recommended Reading:


White, Michael, and John R. Gribbin. Darwin: A Life in Science. Pocket, 2009. 

Darwin, Charles. The Voyage of the Beagle. Collier, 1969.

Darwin, Charles. On the Origin of Species: Complete and Fully Illustrated. Gramercy Books, 1979.

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By Thea BaldrickBS Biology w/ Molecular & Cellular Biology Concentration, BA Comparative LiteratureD. Thea is a contributing science writer with a B.S. Biology with a Concentration in Molecular and Cellular Biology and a B.A. Comparative Literature from the University of Cincinnati. For fun, she spends time inhabiting the world of dinosaurs with family members. She prefers to be the Brachiosaurus.