page_title: On the Origin of Species
section_title: Summary of Darwin's theory
hierarchical_section_title: On the Origin of Species / Summary of Darwin's theory
caption_attribution_description: English: Photograph of Charles Darwin
context_page_description: On the Origin of Species, published on 24 November 1859, is a work of scientific literature by Charles Darwin which is considered to be the foundation of evolutionary biology. Darwin's book introduced the scientific theory that populations evolve over the course of generations through a process of natural selection. The book presented a body of evidence that the diversity of life arose by common descent through a branching pattern of evolution. Darwin included evidence that he had collected on the Beagle expedition in the 1830s and his subsequent findings from research, correspondence, and experimentation.
  Various evolutionary ideas had already been proposed to explain new findings in biology. There was growing support for such ideas among dissident anatomists and the general public, but during the first half of the 19th century the English scientific establishment was closely tied to the Church of England, while science was part of natural theology. Ideas about the transmutation of species were controversial as they conflicted with the beliefs that species were unchanging parts of a designed hierarchy and that humans were unique, unrelated to other animals.
context_section_description: Darwin's theory of evolution is based on key facts and the inferences drawn from them, which biologist Ernst Mayr summarised as follows:
  Every species is fertile enough that if all offspring survived to reproduce, the population would grow (fact).
  Despite periodic fluctuations, populations remain roughly the same size (fact).
  Resources such as food are limited and are relatively stable over time (fact).
  A struggle for survival ensues (inference).
  Individuals in a population vary significantly from one another (fact).
  Much of this variation is heritable (fact).
  Individuals less suited to the environment are less likely to survive and less likely to reproduce; individuals more suited to the environment are more likely to survive and more likely to reproduce and leave their heritable traits to future generations, which produces the process of natural selection (fact).
  This slowly effected process results in populations changing to adapt to their environments, and ultimately, these variations accumulate over time to form new species (inference).
caption: Darwin pictured shortly before publication
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