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Chapter 6
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 announced his intention to use this chapter to respond to some miscellaneous critics of natural selection. Darwin believed that perhaps the most serious objections came from Heinrich Georg Bronn, a distinguished German paleontologist. Bronn thought it unlikely that a variety would live side-by-side with its parent species. He also believed that different species must differ not just in a single characteristic but in multiple ways. Finally, Bronn (and others) suggested that many creatures have characteristics that seem to be useless and therefore could not have been influenced by natural selection.
In order to properly respond to his critics’ objections, Darwin often explained these objections in great detail. While this might at first seem counterproductive to his argument, in fact, Darwin’s argument benefits from the strategy because he takes the time to prove that his theories are comprehensive enough to counter even the most serious of objections.
Themes
While Darwin acknowledged the validity of Bronn’s concerns, he cautioned against making sweeping generalizations about what was and wasn’t a useful characteristic. The ears of mice, for example, were listed by Bronn as an example of a trivial adaptation, but Darwin noted that these ears were full of nerves and that their size likely did play an important role. Darwin also acknowledged that he had adapted his own views on the issue since the previous edition of the book.
Darwin’s scientific way of thinking sometimes led him to unexpected conclusions. For example, on the surface, the large ears of a mouse might not seem to be particularly useful. Nevertheless, careful observation showed that in fact, the ears might play an important role because of the nerves inside them.
Themes
A prominent zoologist named St. George Mivart was a critic whom Darwin respected and wanted to answer. Mivart had a couple objections, notably that a giraffe didn’t make sense under natural selection because the additional bulk added by its neck (requiring an increased supply of food) surely outweighed any potential advantages. Darwin argued that the increase in food was great enough to justify the neck and that perhaps the tall neck also helped the giraffe observe and fend off predators.
The fact that Darwin spends so much time responding to St. George Mivart suggests that he took Mivart’s objections seriously (and perhaps also that readers in Darwin’s initial intended audience would have taken Mivart seriously). Giraffes come up elsewhere in the book and are an interesting example because of their unusual anatomy. Here, Darwin argues that despite a giraffe’s unusually long neck, its relationship to food and predators is much the same as any other animal’s.
Themes
Literary Devices
Mivart’s second objection was that if a giraffe is so well adapted, why haven’t all four-legged mammals developed a long neck like giraffes and, to a lesser extent, camels have? Darwin believed that this objection could be dealt with by considering the different geographies of different creatures’ environments. Another solution is considering how a feature like a long neck requires other body adaptations to be an advantage, meaning it would not be naturally selected for in all animals.
The strength of Darwin’s ideas is that they are flexible, and natural selection often acts differently depending on the specific situation. Mivart’s argument makes sense based on logic, but Darwin’s reply makes more sense based on observation and the scientific method.
Themes
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Darwin continued looking at some of Mivart’s other objections, including the idea that the jaw of a Greenland whale is so large and complex that it couldn’t have arisen through slight successive adaptations under natural selection. Darwin held firm in his disagreement, however, using the example of the shoveler-duck’s beak to show how a structure like a whale’s jawbone could have similarly arisen through natural selection. Mivart had other objections of a similar nature, and Darwin responded in turn to each of these with examples.
The issue of the Greenland whale’s jaw is similar to that of the human eye, and Darwin’s answer for both of these objections is the same. Again, Darwin’s wide familiarity with species living around the world (particularly birds) helped him find examples of different species that could have existed in the past.
Themes
Ultimately, Darwin’s disagreement with Mivart was that Mivart believed drastic adaptations like a bat’s wings happened suddenly, rather than through successive variations as Darwin proposed. While Darwin acknowledged that in some ways Mivart’s view sounded reasonable, he ultimately believed it required making too many assumptions, and that there was not enough evidence in the geological record or in studies of embryos to suggest that it was valid.
Though the disagreements between Darwin and Mivart may seem minor at times, Darwin knew that the success of his theory rested on its accuracy, even on small details. He used critics like Mivart as an opportunity to refine and expand on his own ideas.
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