Content Warning: The source text uses outdated, offensive language when discussing non-Western cultures, Indigenous populations, and Black Africans.

Following a detailed table of contents that lists the many subsections of each chapter, Darwin gives a brief “historical sketch” of scientific theory on the origin of species, focusing on recent history. In this way, Darwin acknowledges the contributions of his predecessors and contemporaries to theory on the generation and modification of species before publication of the first edition of On the Origin of Species in November 1859. He notes that Jean-Baptiste Lamarck, in 1801, was the first biologist “whose conclusions on the subject excited much attention” (528). Lamarck’s lasting contribution is his development of the idea that biological change is the result of adherence to natural law, not divine intervention. In addition, Darwin refers to Alfred Russell Wallace, whose research on natural selection theory was presented in 1858 along with Darwin’s, and Herbert Spencer, who coined the term “survival of the fittest” and was an adherent of what became “Social Darwinism.” Darwin notes Spencer’s contribution to contrasting instantaneous creation with theories of organic development.

For Darwin, the origin of species is the most substantial of all mysteries of the natural world.