The Origin of Species · Chapter
Summary of the Preceding and Present Chapters explained
Darwin summarizes the key arguments from previous chapters, emphasizing the extreme imperfection of the geological record, the role of migration, the slow and successive appearance of new species, and the extinction of old forms as a conseq
What happens
Darwin summarizes the key arguments from previous chapters, emphasizing the extreme imperfection of the geological record, the role of migration, the slow and successive appearance of new species, and the extinction of old forms as a consequence of natural selection. He argues that despite the lack of infinite transitional forms, the laws of palaeontology support descent with modification and the survival of the fittest.
Themes in this chapter
Imperfection of the Geological Record
Darwin argues that the geological record is extremely imperfect, with long gaps between formations, explaining the scarcity of transitional forms.
Extinction and the Succession of Forms
The chapter explains that extinction is the inevitable consequence of new species arising through natural selection, and that dominant groups tend to leave modified descendants while weaker groups die out.
Key passages
“I have attempted to show that the geological record is extremely imperfect; that only a small portion of the globe has been geologically explored with care; that only certain classes of organic beings have been largely preserved in a fossil state; that the number both of specimens and of species, preserved in our museums, is absolutely as nothing compared with the number of generations which must have passed away even during a single formation;”
Darwin argues that the fossil record is highly incomplete because only a tiny fraction of the Earth has been thoroughly studied, only certain types of organisms fossilize well, and the specimens we have represent a minuscule sample of all the generations that ever lived.
This passage summarizes the core argument for the imperfection of the geological record, a key theme of the chapter.
“The extinction of old forms is the almost inevitable consequence of the production of new forms.”
When new species evolve, older species are likely to go extinct as a direct result.
This succinctly states Darwin's view on the link between speciation and extinction.