In This Article Expand or collapse the "in this article" section Natural Selection

  • Introduction
  • Original Exposition
  • Population Genetics
  • Quantitative Traits
  • Across a Species Range
  • Hierarchical Levels of Biological Organization
  • Measures in the Wild
  • The Molecular Level
  • Philosophical Considerations

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Evolutionary Biology Natural Selection
Mark A. McPeek
  • LAST REVIEWED: 12 April 2023
  • LAST MODIFIED: 13 January 2014
  • DOI: 10.1093/obo/9780199941728-0008


Natural selection is the evolutionary process by which individuals with particular attributes in a population change in relative frequency because of their differential survival or reproduction. These attributes may be alleles at a particular gene or set of genes, or particular phenotypic traits. Natural selection is the cornerstone of evolutionary theory, because it is the only process causing evolution that can make a population of individuals better adapted to its environment. Natural selection occurs when (1) individuals in a population differ in some phenotypic attribute; (2) these phenotypic differences cause differences in the survival, mating success, or fecundity among the individuals (i.e., individuals have different fitnesses); and (3) these phenotypic differences are caused by heritable genetic differences among the individuals.

Original Exposition

The idea that species may not be immutable was circulating among scientists in the late 18th and early 19th centuries, and various theories for possible mechanisms had been proposed and negated—most notable among them was the theory of Jean-Baptiste Lamarck, regarding the inheritance of acquired characters. Both Charles Darwin and Alfred Wallace were phenomenal natural historians, and both had literally traveled the world cataloguing the flora and fauna: Darwin on the circumnavigation of the globe aboard the HMS Beagle, and Wallace on exploration trips through Amazonia and the Malay Archipelago. This exposure to the breadth and diversity of the natural world and their reading of the scientific literature, most notably the writings of Thomas Malthus on human population growth, led both to develop the concept of natural selection as an explanation for how new species came into existence. Any serious study of natural selection must begin at the original expositions of the concept, in Darwin and Wallace 1858. Darwin 1859 is an “abstract” that Darwin published to expound the theory of evolution by natural selection. Stauffer 1975, an edited volume, is an attempt to reconstruct the larger book that Darwin was planning to write. Darwin 1871 is the author’s application of his ideas to human evolution and the exposition of sexual selection. Wallace waited thirty years to publish a book-length treatise on natural selection (Wallace 1889).

  • Darwin, C. 1859. On the origin of species by means of natural selection, or, The preservation of favoured races in the struggle for life. Library of English Literature 11392. London: John Murray.

    This book is Darwin’s definitive statement on his theory of evolution by natural selection. His main argument is based on evidence he presents both from his observations of the natural world and the artificial selection that humans impose on various animals and plants through selective breeding. A 150th-anniversary edition, edited and introduced by William Bynum, was published in 2009 (London: Penguin Classics).

  • Darwin, C. 1871. The descent of man, and selection in relation to sex. 2 vols. London: John Murray.

    In this book, Darwin extended his theory of evolution by natural selection to the properties of Homo sapiens, both in evidence that man is descended from other animals, and in explaining many phenotypic properties of man. He also elaborated how interactions within and between the sexes within a species can explain the elaborate mating rituals and ornamentations seen in many animals and plants. An edition was published in 2009 (Cambridge, UK: Cambridge Univ. Press), for the 200th anniversary of Darwin’s birth.

  • Darwin, C., and A. Wallace. 1858. On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection. Journal of the Proceedings of the Linnean Society of London: Zoology 3.9: 45–63.

    DOI: 10.1111/j.1096-3642.1858.tb02500.x

    This is the original paper expounding the concept of natural selection, published jointly by Darwin and Wallace and presented to the Linnean Society by Charles Lyell.

  • Stauffer, R. C., ed. 1975. Charles Darwin’s natural selection: Being the second part of his big species book written from 1856 to 1858. Cambridge, UK: Cambridge Univ. Press.

    This is a volume that attempts to re-create the larger book that Darwin was writing when he received Wallace’s paper. Darwin had planned to write a more expansive book, but Wallace’s paper forced him to shorten his volume into what we know today as the Origin of Species. He intended On the Origin of Species to be only an abstract of his larger theory.

  • Wallace, A. R. 1889. Darwinism: An exposition of the theory of natural selection, with some of its applications. London: Macmillan.

    This is Wallace’s book-length statement of evolution by natural selection. It was published about thirty years after Darwin and Wallace’s original paper together. Republished as recently as 2011 (New York: Cambridge Univ. Press).

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