Themes
Key
LitCharts assigns a color and icon to each theme in The Origin of Species, which you can use to track the themes throughout the work.
Natural Selection and the Power of Nature
Reason, Argument, and the Scientific Method
Time and Progress
Collaboration and Science
Summary
Analysis
Darwin summarized his book as “one long argument,” and concluded that as a result, it might be helpful to the reader for him to summarize some of the major points.
Very little of what Darwin mentions in the final chapter is new information. Instead, Darwin uses it to summarize his most important arguments and distill his book down to the core points. This reflects his intention to write at least in part for a popular audience rather than exclusively for an audience of scientific specialists (who might not need as much summarizing).
Themes
Literary Devices
Darwin repeated what he believed to be some of the most reasonable objections to his arguments, in particular the idea that extremely complex organs like the human eye give the appearance of having been designed and created all at once. He nevertheless maintained that in fact, it was very possible for natural selection to arrive at complex organs like an eye, and that all of these complex organs can be traced to a series of gradual, incremental improvements.
Darwin spends multiple chapters responding to real and anticipated criticisms of his work, so it is fitting that he takes a moment to summarize some of the most significant. He returns to the issue of the eye, which seems to some to be so complex and organized that it couldn’t have arisen under natural selection. For Darwin, however, the eye is just the opposite: a sign of how even the most complex organs can be developed and selected for incrementally.
Themes
Darwin also summarized his arguments about the sterility of crosses between species and how the rules governing fertility in these cases were complex and not as universal as some other naturalists of his era claimed.
Reproduction is a central part of Darwin’s theories, and the sterility of hybrids is an interesting aspect of reproduction that helps illuminate how natural selection works (and where it can’t work due to infertility).
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Darwin moved on to the subject of geographical distribution and repeated his belief that many species descended from a few ancestor species that migrated around the world, and in isolated geographic locations, the process of adaptation and natural selection often led to endemic species.
Another big part of Darwin’s argument is the role that migration plays (and as a result, the role that barriers to migration play in creating new divergences). These ideas reflect the influence of his important Galapagos Islands voyage on his way of thinking.
Themes
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On the topic of intermediate forms, Darwin once again covered the imperfections of the geological record, why intermediate forms are more likely to go extinct, and how even with these issues, it is still possible to reconstruct what role intermediate forms played in natural selection. He went on to explain the causes behind the imperfections of the geological record in greater detail, and also why the fossil deposits that do remain show development consistent with natural selection.
Here, Darwin recounts the influence that Charles Lyell and other geologists have played on his thinking. Geology suggests that events on earth happen over a long time frame, but the imperfections of the geological record suggest that the past is not perfectly preserved and that often recreating the past involves making inferences from the limited (but important) evidence that does survive.
Themes
Darwin then changed the focus to domestication and what it can and can’t demonstrate about natural selection. Darwin reminded readers that humans don’t cause variability in domestic animals and plants, they simply create conditions of life that cause certain characteristics to be passed down. Similar principles occur in nature, just without the direction of humans. Struggles for mates and changes in climate are some of the factors that can lead organisms with certain variations to survive.
Studying domestication helped Darwin understand important principles about reproduction because it provides a controlled environment where humans watch the results of each crossing of parents to create new offspring. Though domestication does not perfectly line up with nature, nature is also harder to observe. Additionally, by comparing natural selection to the better-understood topic of domestic breeding, Darwin helps make his ideas more familiar and approachable.
Themes
Darwin repeated that species were simply “strongly marked and permanent” types of varieties. In some ways, the distinction was arbitrary, although it could also convey important information about genealogy and fertility. New varieties and species with improved adaptations will eventually supplant less well-adapted species and cause them to become extinct. As always, natural selection works in small, successive steps, never in great leaps, even when the end results do seem to lead to a large divergence.
Though Darwin believes classification is important, he also believes it can be arbitrary, specifically when it comes to distinctions between varieties and species. Darwin believes that through natural selection, varieties often actually become new species, and so for this reason, it is difficult to draw a clear boundary between varieties and species that will hold true in all cases.
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Natural selection plays a role in everything from physical attributes to instincts to beauty. New species and varieties are not created independently but arise through “descent with modification,” diffusing and diverging out from common ancestors. Migration also played an important role in this process and suggests that the same species has never independently arisen in two separate areas.
In this section, Darwin emphasizes the comprehensive nature of natural selection, how it can affect not only body parts but even instincts, too. Though there is a wide variety of life on earth, Darwin believes that it arose through migration and divergence rather than through separate acts of creation.
Themes
All current and past organisms can be categorized in classes, a large classification group. Within these classes, some organisms may seem similar on the surface, while others may seem quite different, but ultimately, they all descend from a common ancestor.
Darwin reiterates how all life shares broad similarities, particularly at the highest levels of classification, but also how genealogy can be used to draw more specific distinctions.
Themes
Corresponding parts, like the similarities between human hands, bat wings, and horse legs, provide evidence of how natural selection could have worked in successive variations, showing that great leaps in adaptation wouldn’t have been necessary. Sometimes disuse of a part or organ causes it to become useless after many generations of natural selection.
Darwin emphasizes the idea that natural selection happens as a series of gradual, successive steps and how, given enough time, these little steps are enough to account for big changes (for example, the difference between a bat’s wing and a horse’s leg).
Themes
Darwin recalled how after earlier editions of The Origin of Species, critics misrepresented his position, saying that he credited natural selection with bringing about all modification of species. While he remained convinced of its significance, he allowed that other factors could also play a smaller role in modifying species, even in the first edition.
Darwin revised The Origin of Species over the course of his life, in some cases to respond to comments on the previous edition. Most (though not all) versions of the book published today incorporate revisions that Darwin made later in his life, well after the book’s initial 1859 publication.
Themes
Darwin wrote that he couldn’t see why his book would offend religious people, and he noted that religious critics once attacked other scientific principles that were soon commonly accepted, like gravity.
Darwin is potentially understating the issue here—his arguments in defense of his theories elsewhere in the book suggest he was in fact aware of the reasons why certain religious leaders might disagree with him. Nevertheless, Darwin chooses to present himself as humble and agreeable rather than emphasizing the potentially controversial aspects of his claims.
Themes
Darwin speculated that the reason why so many naturalists believed in the immutability of species was that it was hard to imagine the individual steps. He compared his work to Lyell’s, noting that Lyell’s theories about how dramatic geological features like cliffs and valleys formed were also met with resistance, but that people were more likely to believe them once they understood the intermediate steps.
Though not exclusively a religious idea, the concept of immutability of species was often connected to religious beliefs, particularly the belief that God created nature and it is already in its perfect form. Darwin allows that the imperfections of the geological record might at first seem to support immutability, but he argues that a deeper analysis reveals plenty of evidence of intermediate steps, which would suggest that species are in fact mutable (i.e., able to adapt, evolve, and diverge into new species).
Themes
Darwin considered the question of how far he would extend his ideas about natural selection. He acknowledged that his arguments carried more force in certain situations than others before ultimately stating his belief that all animals and plants each came from no more than four or five ancient progenitor species. He considered the idea that all animals and plants ultimately descended from a single origin, and considered the idea possible but not necessarily inevitable.
Though Darwin’s The Origin of Species is famous in popular culture for popularizing the idea that humans descended from ape-like ancestors, in fact, Darwin is very careful not to state that idea too directly in the book (even though he did believe it and wrote about it in more detail in future books). This section is probably the closest Darwin comes to mentioning human evolution —if all species descend from a few progenitors, or even just one, then surely humans are no exception.
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Darwin looked ahead to how his views might spark a revolution in natural history, particularly when it came to classification. While he believed it would involve leaving behind some old ideas about species, it would also lead to greater general interest in natural history as a discipline. He also predicted his work could have an impact on research in other fields, such as psychology.
Despite his seeming humility elsewhere in the book, Darwin is aware of the potentially revolutionary nature of his ideas, and he takes a moment here at the end to present this revolution as something to celebrate and embrace rather than something to fear.
Themes
Darwin concluded by arguing that in spite of the fact that many prominent authors believed that species arose independently, Darwin believed that natural selection seemed to better reflect the will of a Creator and to give creations more nobility. He believed that under natural selection, all living things would continue to progress toward perfection. Darwin marveled at the grandeur and complexity of nature and how “endless forms most beautiful and most wonderful have been, and are being evolved.”
Darwin’s religious views (or possible lack of them) are frequently debated and may have changed over the course of his life. In The Origin of Species, however, Darwin seems to be less interested in advocating for a specific religious position and more interested in presenting a coherent scientific argument. He knows that a good argument often must not only be logical but also be appealing in other ways, and that is likely why he chooses to end with a sentence that emphasizes the beauty of natural selection and its continuity with religious tradition, rather than emphasizing something more pessimistic.
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